The Universe is expanding at 73.8 +/- 2.4 km/sec/megaparsec! So there.

By Phil Plait | March 22, 2011 7:00 am

In 1998, two teams of astronomers independently reported amazing and bizarre news: the Universal expansion known for decades was not slowing down as expected, but was speeding up. Something was accelerating the Universe.

Since then, the existence of this something was fiercely debated, but time after time it fought with and overcame objections. Almost all professional astronomers now accept it’s real, but we still don’t know what the heck is causing it. So scientists keep going back to the telescopes and try to figure it out.

[Click to galactinate, or grab the cosmic 3500 x 4000 pixel browser bruiser.]

This gorgeous image is of the nearby spiral galaxy NGC 5584, where of course "nearby" to an astronomer means 72 million light years. This galaxy is loaded with a specific type of variable star — called Cepheids — which are very important: the way they change their brightness depends on how luminous they are. Measure the change, and you measure the luminosity, and if you measure how bright they appear in the sky you get their distance. It’s a bit like judging how far away a car is by gauging how bright its headlights are. Except in this case astronomers use Hubble instead of their eyes. It’s a tad more accurate.

It so happens that in 2007, NGC 5584 was the host of a Type Ia supernova, the Golden Standard of distance indicators. These are so bright they can be seen clear across the Universe! By knowing the distance to the one in NGC 5584, we can then use that to get the distances to supernovae much, much farther away.

It’s a bootstrappy way of measuring the cosmic distance scale.

But it appears to work. By measuring the Cepheids in eight galaxies that also hosted Type 1a supernovae, astronomers (led by my old pal Adam Riess; we were grad students together when he cracked the Type 1a code that led to the discovery of the universal acceleration — which will win him the Nobel one day, I’d wager) were able to hone the distance bootstrap even better.

And now, by measuring first the Cepheids and then using them to determine the distance to far-flung supernovae, they have nailed down just how fast the Universe is expanding: 73.8 (plus or minus 2.4) km/sec/megaparsec.

OK, so what does that mean?

We see galaxies rushing away from us. Moreover, the farther away they are, the faster they appear to be moving. The rate of that expansion is what was measured. If you find a galaxy 1 megaparsec away (about 3.26 million light years), the expansion of space would carry it along at 73.8 km/sec (fast enough to cross the United States in about one minute!). A galaxy 2 megaparsecs away would be traveling away at 147.6 km/sec, and so on*.

The last time this was measured accurately, the speed was seen to be 74.2 +/- 3.6 km/sec/mpc. Note the uncertainty; both the old and new measurements overlap to within their uncertainty (which is good!), but the new one has a smaller uncertainty. In other words it’s most likely more accurate.

By knowing this number so well, it allows better understanding of how the Universe is behaving. It also means astronomers can study just how much the Universe deviates from this constant rate at large distances due to the acceleration. And that in turn allows us to throw out some ideas for what dark energy is, and entertain notions of what it might be. For example, one idea was that instead of dark energy accelerating the Universe, it was an illusion due to our region in the local Universe being unusually underdense — that would make it look like distant galaxies are receding faster than expected. However, the precision of the new measurement rules this out; the value needed by the void model would have to be much lower. So right away we know that this explanation doesn’t work, and the idea of dark energy survives another battle.

So that number of 73.8 +/- 2.4 km/sec/mpc may sound arcane and weird to you, but it is in fact the key to understanding the Universe itself. It’s amazing that so much can ride on one number… but that’s the Universe for you.


* In reality it’s a little more complicated than that. Due to gravity of galaxies and clusters, the rate of expansion doesn’t really kick in until you get out to a distance of a handful of megaparsecs. But the concept is the same.

Comments (137)

  1. Messier Tidy Upper

    But .. but .. isn’t that number meant to be 42? ;-)

  2. Caleb

    Well, if the object you are observing is ~0.569 mpc away, then it would be receding at 42km/s. Quick, somebody find out what happens to be that far away!

    (you also have to ignore Phil’s footnote, but whatever)

  3. So, given that 73.8 km/megaparsec is roughly 2.39 parts per quintillion (as both are measures of distance) could we say that the rate of expansion is 2.39 ± 0.08 parts per quintillion per second?

  4. Tobin Dax

    @ MTU – That number is 42 in base 18. :)

  5. X

    It’s probably more useful to think about it as being 7.5%/Gyr.

  6. Sam H

    @Tobin Dax = WORD!! :) But I never got how it’s even possible to count outside of base ten…

    Anyway, could the same base force or substance be behind both dark matter and dark energy? (I know the difference between the two, but at our current level of knowledge I wouldn’t say that’s impossible). And BTW, have they confirmed the so called “Dark Flow” yet?

    Messier, while I didn’t need all those quotes you offered yesterday due to most of them being irrelevant, the one on it taking 5200 years to drive to Neptune at 100 kph will certainly be used in my presentation (although I’m going to have to give them a very basic idea of multiplication in order for them to understand what “5200” actually means). The only thing I can’t include is the fact that an asteroid will hit us again one day, as the teacher said it could give some of them nightmares. Anyway, since it’s today I’m really excited now, and I can’t wait to see their expressions of childlike, innocent awe and wonder.

    And I need to visit Oz one day (or any continent aside from NA)!! It’ll actually be mentioned in the presentation in my own special way ;)

  7. SeanMcD

    So, there is a limit to how far we can see in the universe, i.e. once the rate of expansion at a given distance is greater than the speed of light, that light will not reach us… ever. Some light math, :-), and it looks like that’s out at about 13,196,221,498 light years. Hey, that number looks familiar, it the approximate age of the universe itself, and as about as far as we’ve been able to see (I noticed that after looking at my own comment!). Now the next question is just how unimaginably big is space?

  8. kingthorin

    This is really confusing “the way they change their brightness depends on how luminous they are”

    I read this and was confused, I even checked dictionary.com for “luminous” (http://dictionary.reference.com/browse/luminous):
    “1. radiating or reflecting light; shining; bright”

    So Phil’s saying brightness depends on how bright they are…we never coulda guessed that. I’m sure there’s a point in there but it doesn’t make sense to a lay person :(

  9. N. Batty

    as Monty Python’s Eric Idle sings

    The universe itself keeps on expanding and expanding
    In all of the directions it can whizz
    As fast as it can go, the speed of light, you know
    Twelve million miles a minute and that’s the fastest speed there is

    So remember, when you’re feeling very small and insecure
    How amazingly unlikely is your birth
    And pray that there’s intelligent life somewhere up in space
    ‘Cause there’s bugger all down here on Earth

  10. electrikmonk

    At that rate, how quickly does a given unit of space double in volume?

  11. Are they looking for that “something” with other instruments than telescopes? I mean, what if they’re using the wrong instrument? What if that “something” that’s expanding the universe is only measurable with… I don’t know… Uh… Some other tool?

    I mean, someone surely must have thought about this, but what if that “something” is actually a whole bunch of infinitesimally small things?

    Know what I mean?

  12. J. R. Braden

    I really do love Phil’s blog. Without dumbing down the information he makes it easy for a philosophy/religion student like me to understand somewhat-complicated aspects of astronomy. Without him, this stuff would blow my little theologian noodle.

  13. Bob_in_Wales

    Back in the early 80s when I did my degree there were two separate methods of measuring the Hubble constant. I don’t recall what they were but I do remember that one gave a figure of around 50 and the other around 100 km/s/mpc. We used to joke that it was therefore probably about 75, you know – top flight science – add up and divide by 2. Nice to see we were right.

  14. Jenna

    @#7: Little Theologian Noodle… a great idea for a cafe!
    @#1: Also disappointed, but 42’s time will come soon!
    I know what is causing everything to move away from us… They must think we’re ugly… or smelly.

  15. electrikmonk

    If I did my math right (which I don’t take as a given) and not considering the rate changing over time, a volume of scape would take 5.485×10^9 years to double in volume.

    Did I do this right?

  16. John

    So, what happens at about4100 mpc?

    c/(73.8 +/- 2.4 km/sec/mpc)

  17. Messier Tidy Upper

    @^ John : Can we get it up to 42,00 mpc? ;-)

    @ 9. Jenna : or both? ;-)

    @ 4. Tobin Dax : Nicely done! That’s some good mathematics & quickdraw calculating there! 8)

  18. Messier Tidy Upper

    Great galaxy image btw. :-)

    Those wishing to know more about Cepheid variables – which are truly rather impressive stars in their own rights* – can czech out :

    http://en.wikipedia.org/wiki/Cepheid_variable

    & those seeking to see a Cepheid should see :

    http://stars.astro.illinois.edu/sow/mekbuda.html

    Otherwise known as Zeta Geminorum and one of the brighter examples in earthly skies along with Eta Aquilae and Delta Cephei itself which can be found by Northern hemispherers here :

    http://stars.astro.illinois.edu/sow/cep-t.html

    via Kaler’s wonderful Stars website.

    Hope folks find these links interesting / useful. :-)

    * Think of yellow supergiants. Imagine seeing our Sun – like we see it from 1 Astronomical Unit (AU – the Earth-Sun) but looking about as we see it from around Pluto’s distance (30 AU) away. Now imagine it pulsating like a stellar heartbeat, noticeably dimming and brightening, shifting from slightly whiter to slightly yellower, like clockwork. Also, these stars are celestial lighthouses of superluminous brightness. Recall that we can see them individually in whole other distant galaxies. Yowza! :-o :-)

  19. Jason

    Stupid question: how can they be sure this is a constant? How can we know that it’s not different in one direction than another?

  20. OK, I’m trying to sink my teeth into this expansion acceleration concept. People say the universe is expanding and the expansion is accelerating; citing the rate of expansion increasing the farther away objects are from us. But, hold the phone. If we peer into deepest space where the expansion is going the fastest, doesn’t that mean that the expansion was faster in the past but now it is slower? If the universe was accelerating the expansion, I would expect closer objects to be receding faster than the farther ones.

    I’m probably upside down on this. Help a brother out, won’t you?

  21. As an alternative to dark matter distribution rationalizing the observed rotation rate of galaxies to large radius, MOND suggests (Newtonian) gravitation does not quadratically asymptote to zero with distance. MOND proposes there is a universal floor to gravitation at large distances. The one parameter fit is spookily good for galactic edge rotations including 21 cm hydrogen beyond star distribution.

    If MOND is da bomb, as it were, then dense galaxy distributions should show anomalously high mutual gravitational interactions. Expansion of the universe with time, given that inverse square attentation does not obtain, should be slowed.

    It would appear that you folks have some serious problems here making your curve fits consistant at increasingly larger scales. One is reminded of biology that was purely descriptive – huge catalogs of rationalizations – until genomics came along to fundamentally, sparely describe what was being seen.

  22. Nigel Depledge

    @ John (10) –
    I know this one. It’s not that the galaxies are moving through space at that speed, it’s that the recession is caused by the space between galaxies expanding.

    So, the recession velocity really does exceed c at that distance, from our point of view. But the galaxies there are moving through local space no faster than is our Milky Way (probably). This is why the observable universe has a boundary (the boundary being where apparent recession velocity exceeds c). IIUC, most cosmologists expect the universe to be infinite.

  23. Nigel Depledge

    @ Psyber Dave (13) –
    IIUC, it is the shape of the curve (if you plot distance versus recession velocity) that indicates that the rate of expansion is accelerating. Obviously, in any expanding universe, more distant objects will be receding faster than nearby ones. However, if the nearby ones are receding a bit faster (and conversely if the distant objects are receding a bit slower) than you would expect from a simple linear relationship, you can conclude that the rate of expansion is accelerating.

    D’you see?

  24. Messier Tidy Upper

    NB. For those (like me) in the southern hemisphere who are unlikely to see Delta Cepehei itself, taking a look at :

    http://stars.astro.illinois.edu/sow/betador.html

    Beta Doradus is perhaps one of the best chances to see a Cepheids on view southern circumpolar stars~wise.

    Kaler’s photographic finderchart for it is here :

    http://stars.astro.illinois.edu/sow/dor-t.html

    My source for the cepheid disance is here – Celestia program via an article I wrote some time ago on the three related supergiants of (near) gold (Sadalmelik, Sadalsuud and Enif) :

    Reflect on this. The next sunny day, its worth looking around and reflecting that if Sadalmelik [A G2 I yellow supergiant star but notactyually acepheid although inthesame class as many of them – ed] replaced the Sun then given its identical spectral type, it would likely appear the same as our Sun in brightness and general appearance. We’d see the same white–yellow orb casting the same strong light and heat – but only if our Earth was orbiting Sadalmelik from a distance of fifty-six Astronomical Units rather than our present location a single AU away! That is way beyond Pluto’s orbit, indeed, its roughly equivalent to the orbit of that most distant ice dwarf planet Eris! (‘Celestia’ computer program, Sept. ’08.) [Emphasis added.]

    Whilst, finally, the Cepheid story virtually requires a mention of :

    http://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt

    one remarkable astronomer by the name of Henrietta Leavitt. :-)

  25. Nigel Depledge

    @ Uncle Al (14) –
    Unfortunately, MOND does not explain gravitational lensing of galaxy clusters.

    Also, you rae being a bit dismissive of several quantitative areas of biological science that existed in the pre-genomics world.

    Population genetics and enzyme kinetics*, for instance, both had a firm quantitative footing before genomics came along. Also, genomics has yet to fulfill its potential. Until a genome is fully annotated, it is not much more than a catalogue of genes, which is a static description of a dynamic system. Transcriptomics, proteomics and metabolomics – all of which are nascent areas of biological research – look far more promising as ways of understanding the dynamism of biological systems.

    * I refer you to Michaelis I. and Menten M.L., (1913) Die Kinetic der Invertinwirkung, Biochem. Z., 49: 333 – 369. But that does rely on your being able to find a paper copy of Biochemische Zeitschrift from 1913. And, to be honest, my German was not up to following the text of the paper, but the equations all looked very familiar.

  26. Joakim Rosqvist

    @Jason(12): because we can redo the measurements with other Cepheids and supernovas in several directions.

  27. Nigel Depledge

    @ Jason (12) –
    It’s not a stupid question, but, IIUC, it has occurred to various cosmologists and has been investigated. AFAWCT, it is the same in all directions.

  28. Messier Tidy Upper

    Hmm.. Just checked again and worried that Kaler’s photofinder link for Beta Doradus could be a mite confusing for some folks – so try :

    http://en.wikipedia.org/wiki/Dorado_(constellation)

    for clarity instead /as well.

    Beta Doradus is pretty much on a line betwixt Canopus & the Large Magellanic Cloud & ranges from 3.46 to 4.08 in apparent magnitude.

    PS. Jason (#13) that’s not a stupid question at all but a very reasonable one – as are the answers to it as provided by (#21.) Nigel Depledge & (#20.) Joakim Rosqvist. :-)

  29. Terry

    @Psyber Dave (13):

    The further away we look, the further back in time we see. If you look at the deepest reaches of space, the speed of expansion is faster than if you look at the medium range. This is the effect of gravity slowing down matter as it expands and is the proof that it was once all at the same point in space (big bang). However, if you look the closest area, it is moving faster than would be predicted by a straight deceleration curve when compared with the medium or long range areas, proving that in addition to the effect of gravity at the large scale, there is another large scale force operating to speed expansion up. It is a truly minor force, only relevant due to its overwhelming size. We don’t know what that force is, so we call it “dark energy” because calling it “dark force” would scare a lot of Star Wars fans.

    The NASA image above shows how the the forces of dark energy interact with dark (and regular) matter. Gravity from matter does the slowing while dark energy does the speeding, it creates a combined curve denoted by the red line. The other colors denote other models, without dark energy and with gravity at different force levels, for comparison to observation. The observable constant above makes us lean further toward the red line model. Basically, think of it as two forces interacting, like a car hitting the brakes then getting rear ended by the guy behind him.

  30. DrBB

    So… something blows up in empty space (well, actually it creates the space it’s blowing up into since there wasn’t any before). The fragments go zizzing out and gravity eventually starts pulling bits of ‘em together, which glom onto other bits etc etc and then a) if their aggregate mass is high enough, the whole thing stops zizzing out and ends up collapsing back together again, or b) if it isn’t, the zizzing never stops, and everything eventually goes dark and cold and silent. We now have observational evidence strongly indicating it’s b.

    That’s my naive view, obviously uninformed by anything but the most basic intuitive-level “physics.” But I set it out in order to ask, in terms I can hopefully understand, what is lacking from that description that requires invoking “dark energy” to explain? In b) the blowing up force is greater than the mass, so of course everything just keeps flying away from the point of origin. Seems logical; why isn’t that enough? Is it the fact that it’s still accelerating? That makes it seem like the original explosion is still going on–i.e., the energy that blew the original dingus apart is still, as it were, blowing. Is that it? If so, it seems to imply that dark energy is also going to account for why that original whole-universe-in-a-hyperdense-pinpoint blew up in the first place instead of just sitting there forever.

    Can someone weigh in with the cosmology-for-dummies answer to these befuddlements?

  31. That’s fast. But, can it make the Kessel Run in 12 parsecs?

  32. aleksandar

    Wait, does this mean that Big Rip is valid end of universe?

  33. oldebabe

    Isn’t the Andromeda galaxy moving toward us (the Milky Way galaxy)?

    And isn’t some asssumption being made here that we are at the center of the universe? point of origin? i.e. that everything is moving away from us?

  34. Chris Winter

    There is (or was) a firm in Atlanta, GA called KesselRun Corporate Travel Solutions (kesselrunconsulting.com )

    “At KesselRun, superior performance is implied.” :-)

    And then there’s this:

    Copyright (c) 2009 Vanderbilt Journal of Entertainment and Technology Law
    Vanderbilt Journal of Entertainment and Technology Law
    ARTICLE:Is It Really Possible to Do the Kessel Run in Less than Twelve Parsecs and Should It Matter? Science and Film and its Policy Implications
    Winter, 2009
    11 Vand. J. Ent. & Tech. L. 249
    Author
    Dov Greenbaum*

    Science and film have traditionally had an uncomfortable relationship. Whereas science is about finding objective truths, movies are, if not wholly fictional, thoroughly laced with elements of fiction. When these fictional elements combine with a portrayal of science, often based on visceral fears, our understanding of that science becomes indelibly and negatively colored. This Article concerns those instances where films tend to add to the information pollution that already clouds society’s understanding, promoting policy decisions that might not be in the best interests of science.

    The full article costs $12.50 or thereabouts.

  35. DrBB

    @23: I think I know the answer on that one: space itself is expanding, therefore at any given point it looks like all of it is moving away–anywhere you are looks like the point of origin. Usual thought-model is to think of making dots on a balloon with a sharpie and then inflating it. From the point of view of any dot, it looks like the others are all moving away while your dot is staying still.

  36. Other Paul

    @Meng Bomin : The expansion is about 2.39 * e-18 per second, as you say. But eliminating the length dimensions is only part of the way to de-humanising this number. A ‘second’ is pretty arbitrary (and derived from the parochial earth) – so how about a more universal and less geocentric unit of time? E.g. the 1420MHz hydrogen line? So we’d divide by 1.42e6 and take your number down even further to 1.68e-24. But Hydrogen’s so ‘physical’ – anything else?

  37. #5 Sam H – for base 18, just use your fingers and eight of your toes. When you get to the 18th “digit”, you’ve got ten!

  38. Jason

    @23,oldebabe

    Yes, Andromeda is moving towards us. That’s because it’s part of the Local Group, which are all gravitationally bound together. Gravity is holding everything all the galaxies in the group together, preventing the expansion from pulling them apart.

  39. John Moore

    It’s like being a snipet of DNA looking out towards the center of an aeomeba trying to figure out how fast the cell is dividing…..

  40. BradC

    @DrBB (20): The problem is that the observed state is really c) The particles aren’t being SLOWED in their flight away from each other by gravity, as you would expect. They are actually ACCELERATING away from each other.

    That’s the weirdness, and so scientists said “some (unknown) force is pushing galaxies away from each other at an accelerating rate. We don’t know what it is, but lets call that force DARK ENERGY, so we’re all on the same page. Hopefully, we’ll eventually figure out what it actually is.”

    Sorta, mostly.

  41. Random thoughts:

    What if rather than space expanding faster, it’s time that is slowing? How would you tell the difference?

    I always found the km/sec/megaparsec units a bit odd – there are two units of distance in there, which would seem like they cancel out and give the rate of expansion as 1/s, or Hz, meaning the expansion is a frequency. :)

  42. Grizzly

    See if it were 67.6 +/- 3.6 km/sec/mpc the answer WOULD be 42 (miles that is).

  43. Ryan

    Something about this post made me wonder about why most hst and other telescope images are of “close” objects. I took a quick look at your archives, APOD and Chandra and a significant portion of the 37 images I looked at are roughly between ~12 mly and ~80 mly. Some are sprinkled in between 300 and 800 mly. Kind of the same deal with closer stuff, less than 30000 ly for most of it. Is this just a function of where we are looking? Our telescopes? I seem to remember reading that we are kind of isolated once you get away from the local group. Does it have something to do with that? Is it odd that few things are in the 100 mly and up range until you start running into clusters in bly distances?

  44. Rift

    Phil- I remember when you first announced this back in 1998 on your old old board. You were very skeptical. (you were also ‘careful’ (the word i would use about your stance) about global warming back then too).

    That’s why I love science. We aren’t dogmatic and don’t ignore evidence, like say, ahem, religion.

    Which is why I get a kick when you do, say, a global warming post and all the deniers say you’ve been duped. I’ve watched you (heck myself too) go from careful and skeptical to seeing the vast mountain of evidence pile up.

    Good thing the expansion of the universe speeding up hasn’t gone political yet :P

  45. Matt B.

    This post doesn’t really deal with the acceleration of expansion, although if that number is a constant it certainly shows a failure to slow down. We’re basically being given an equation “a = k * d^1″. If the expansion were slowing down, it should be something like say “a = k * d^1.1″ (because farther things are being observed longer ago, and therefore should be receding faster than linearly proportional to distance). If the acceleration is increasing over time, it should decrease with increasing distance and give us something like “a = k * d^0.9″. Please let me know if I’m off base here.

  46. OldTimer

    I believe we are being duped by our assumptions about time and acceleration and the speed of light. I think the rate of passage of time varies 1) near massive objects per general relativity 2) over long distances of space. Some physicists/philosophers believe that there can be no such thing as time – that there is just the present and we are constantly collapsing a wave function of possible realities. I just believe that we don’t have a handle on what’s going on and that our measurements are accurate but our assumptions are wrong.
    Does quantum mechanics make sense to us? No. What’s the deal with gravity being equivalent to an accelerating inertial mass – does that make sense? Is what we feel as gravitational acceleration on earth really an acceleration or the effect of the change of rate of time passage near the mass of earth. I admit I am confused!

  47. I RoboSapien

    @ #13 PsyberDave –

    Let me see if I can state this in English rather than mathematics. The farther any two galaxies are apart, the faster they recede from each other, so more distant galaxies do move faster away from us. But any other galaxies local to (closer to) those distant galaxies will by moving away FROM EACH OTHER slower, just as galaxies close to us move away from us slower than more distant ones. So we can look back in time at a distant galaxy and see it speeding away from us, yet moving slowly with regard to its more local galaxies. Does that help, or am I just confusing things more?

    @ # 10 John, and #15 Nigel DePledge –

    Remember that velocity is relative, and relativistic velocity is not linear but is asymptotic. The farther away something is the faster it recedes relative to us, yet that relative velocity can approach but never exceed light speed, even though the object may be continuously accelerating — just as a spaceship may accelerate forever, always steadily increasing its speed from its own perspective, yet relative to its point of origin it never exceeds cee (which leads logically to the concepts of time dilation and space foreshortening, but that’s another subject).

    @ # 20 DrBB –

    Yes, you’ve arrived intuitively at a more mathematically complex deduction, that that dark energy pushing the universe apart may have been the driving force behind the Big Bang, only now dispersed over a vast volume (and in fact much of the original dark energy was probably converted to ordinary energy in the early moments of the universe in something called a phase transition, allowing the formation of the more stable matter/energy universe we’re familiar with and reducing dark energy’s power). Dark matter, on the other hand, is a hypothetical exotic form of matter we cannot directly detect, we only see its gravitational effects on galaxies and via gravitational lensing — the bending of light in empty space. Supersymmetry theory proposes a number of particles that would account for dark matter, particles that interact only weakly if at all with our ordinary matter (hence making them practically undetectable), but that do have gravitational effects. These things are important because our best measurements indicate that the universe is made up of only about 4% atoms, but 23% cold dark matter, and 73% dark energy, so we must take those into account if we really want to understand the universe.

    @ # 23 oldebabe –

    Yes, Andromeda is on a collision course with us. But Andromeda is part of our local closely-grouped cluster of galaxies, which are gravity-locked with each other as a unit, much like our planets and sun orbit each other as a unit, bound together by mutual forces. There are many such clusters of gravity-locked galaxies. Yet in the larger scale of the universe as a whole, all free matter moves away from all other free matter, so the clusters move away from other clusters, and in practical terms we see all other galaxies outside our own local cluster moving away from us.

    As to your second point, it’s a difficult concept to grasp, but there is no center to the universe (and no edge, either). Or conversely every point is the center of the universe. That’s because in the beginning everything WAS the center (the Big Bang started as a dimensionless point). So at one and the same time, EVERY point in space can be considered the center (because in the beginning it was), and NO point is the center (because any other point could just as well be). It all depends on your viewpoint – because space itself was created with the universe, the Big Bang didn’t occur within some larger spatial framework. Consequently, there is no absolute point of spatial reference.

  48. Regner Trampedach

    Matt B. @ 35: “This post doesn’t really deal with the acceleration of expansion,…”
    That is entirely correct. This was a measurement of the current speed of the expansion of the Universe. But, as in any science, a single measurement never stands alone. It is only a single piece in the amazing puzzle of Nature. Comparing that single puzzle piece with some of the other pieces we have found, actually does tell us something about the acceleration of the expansion of the Universe and narrows down its value.
    Cheers, Regner

  49. The Universe is expanding at 73.8 +/- 2.4 km/sec/megaparsec!

    A new song on They Might Be Giants’ next album.

  50. Sam H. @ 5: Check out “New Math” by Tom Lehrer. That helps loads in explaining other bases to me (which I had to use – binary (base 2), octal (base 8), hexadecimal (base 16)… Check out http://video.google.com/videoplay?docid=-7841878207694220233# for more information. :)

  51. @kreyg #31: What if rather than space expanding faster, it’s time that is slowing?

    Seems to me that time slowing down would cause the expansion of space to slow down proportionately, and thus make no difference to observations.

  52. “(led by my old pal Adam Riess; we were grad students together when he cracked the Type 1a code that led to the discovery of the universal acceleration — which will win him the Nobel one day, I’d wager”

    One of the rules in Nobel’s will which is strictly followed is that the prize is split among at most 3 people. (Another strict rule is no posthumous awards.) The Hubble diagram for SNIa involved many people. Do you want to give it to just the team leaders? OK, that was what happened when Smoot and Mather got it, but one could make a case that there was quite a gap between the team leaders and the rest of the team. That’s not really the case here. If you do that, you leave some deserving people out, so the move might be not to award this discovery at all. Yes, all were not equally deserving, but I don’t think you can pick out three.

    Also, although important, this discovery alone would never have been convincing. The fact that the value for the cosmological constant from this work is the same as, or at least compatible with, that from other projects—though perhaps individually less dramatic—is what makes it convincing. It is sort of like measuring the Avogadro constant. It wasn’t so much one experiment but rather the fact that several independent lines of evidence pointed to the same result which was convincing.

  53. “Anyway, could the same base force or substance be behind both dark matter and dark energy? (I know the difference between the two, but at our current level of knowledge I wouldn’t say that’s impossible). And BTW, have they confirmed the so called “Dark Flow” yet?”

    The name “dark energy” is one of the biggest goofs in the communication of science. As Sean Carroll pointed out, everything has energy and lots of things are dark, so the name really tells us very little. (He suggested the much better name “smooth tension” which emphasises the key aspects.) It suggests an affinity to dark matter which simply does not exist, as far as we know. Dark Flow? Can you say “bandwagon”?

  54. “But .. but .. isn’t that number meant to be 42? “

    He turned out to be wrong, but Allan Sandage really did write A case for H0 = 42 and Omega(0) = 1 using luminous spiral galaxies and the cosmological time scale test, but we now know that he was wrong about both H0 and Omega0.

  55. “So, what happens at about4100 mpc?

    c/(73.8 +/- 2.4 km/sec/mpc)”

    Nothing. Can’t be explained in a comment. I suggest reading Edward Harrison’s textbook Cosmology: The Science of the Universe.

  56. “Stupid question: how can they be sure this is a constant? How can we know that it’s not different in one direction than another?”

    Because it has been measured in several directions.

    In the case of the Hubble constant, it is the constant in the sense of an equation describing the slope of a line. It is also independent of direction, so in that sense constant. It is not constant in time, in general. The cosmological constant, on the other hand, is constant in time (and from place to place).

  57. “OK, I’m trying to sink my teeth into this expansion acceleration concept. People say the universe is expanding and the expansion is accelerating; citing the rate of expansion increasing the farther away objects are from us. But, hold the phone. If we peer into deepest space where the expansion is going the fastest, doesn’t that mean that the expansion was faster in the past but now it is slower? If the universe was accelerating the expansion, I would expect closer objects to be receding faster than the farther ones.”

    In the beginning, the universe was decelerating, then expansion took over. While one measures objects at different distances, the result is that one measures the expansion now. One can also calculate the rate of expansion and of acceleration (perhaps negative) at any time in the future or in the past, once one knows the cosmological parameters.

  58. “Wait, does this mean that Big Rip is valid end of universe?”

    No.

  59. “Isn’t the Andromeda galaxy moving toward us (the Milky Way galaxy)?”

    Yes, a local effect. The “Hubble flow” isn’t reached until one gets to larger distances.

    “And isn’t some asssumption being made here that we are at the center of the universe? point of origin? i.e. that everything is moving away from us?”

    No. Read any cosmology textbook.

  60. “I always found the km/sec/megaparsec units a bit odd – there are two units of distance in there, which would seem like they cancel out and give the rate of expansion as 1/s, or Hz, meaning the expansion is a frequency.”

    Yes, in a sense, and the reciprocal of the Hubble constant is the Hubble time. But it isn’t a frequency since it is not a repeating phenomenon, even though the unit in both cases is an inverse time. The Curie has the same units.

    There are similar cases. At http://en.wikipedia.org/wiki/Torque one can read:

    “The joule, which is the SI unit for energy or work, is dimensionally equivalent to a newton metre, but it is not used for torque. Energy and torque are entirely different concepts, so the practice of using different unit names for them helps avoid mistakes and misunderstandings”.

    There are many other cases, such as units of radiation in energy per frequency per time. The last two cancel (and of course energy also has a time component), but that would obscure time: the per frequency is a bandwidth and per time is normal time.

  61. jess tauber

    Sooooo, mathematical geniuses on the list, how many planck lengths/planck time/planck length is this? Just want the figure in fundamental units, to see if it means anything significant. Thanks.

    Jess Tauber

  62. This has units of inverse time, so the right thing to compare it with is a frequency. If I haven’t bobbled the calculation, it’s about 1.3 x 10^-61 times the Planck frequency. Make of that what you will.

  63. …Anyway, I wouldn’t expect the current value of the Hubble constant to have any great fundamental cosmic significance, since it’s not really a constant; it should change with time.

  64. Dutch Railroader

    @Phillip & Jason,

    When the recession velocities are probed over the sky in different angular directions, differences in the mean Hubble relation are often seen, which are generally interpreted to be due to the space motion of our galaxy or coherent bulk flows galaxies over large regions of space (100s of Mpc). The studies vary on the size of such effects, and studies that have produced large flows on large scales are not generally accepted due to poor mutual agreement and contradiction of favored theories of structure formation.

    Studies like the present one cited generally attempt to use a Hubble diagram averaged over the full sky to cancel out bulk flows, or other inhomogeneities in the velocities. However, they generally do not probe fine differences in the expansion rate as a function of position on the sky.

  65. Bob O'Rygmy

    Phil: You said: ” It so happens that in 2007, NGC 5584 was the host of a Type Ia supernova, the Golden Standard of distance indicators.” If the supernova occurred in 2007, how are we observing only three years after occurence?

  66. Bob O'Rygmy

    I realize there must be a simple answer for my question; I’m obviously not a scientist, but I read your blog every day………..

  67. Dutch Railroader

    @Matt

    To be correct, the Hubble “parameter” describes the expansion rate at any time, while Ho – “H naught” gives the rate at only the present epoch. It is an extremely important constant as it sets a boundary condition, allowing an overall scale and age of the Universe to be determined under any model of how the expansion parameter changes with time.

  68. The dumb blond asks this dumb questions

    The Universe is expanding into what?

    If Space is expanding, what is Space? What is it made off? Is it made of nothing? If made of nothing, how can something be made of nothing?

    If Space is expanding at at 73.8 km/Megaparsec then at 4065 Megaparsec (13.252 Billion light years) then the rate of expansion reaches the speed of light at that distance from here. Therefore whatever is beyond this distance is out of sight. However each year we can see one light yer farther because the Universe has aged by one year. Is it possible to know how big is the Universe by seeing only up to our 4065 megaparsec horizon? If the Universe is very big, then it might be flat as it appears to us. Then it would appear Flat only because we see a minute portion that it appears Flat. I dislike the idea of a Flat Universe because my mind is too small. Will some big brain give me some hope that the Universe is not Flat? I dislike Flat places. If the Universe is Flat, then I leave this place

  69. response to 22. aleksandar Says:
    Wait, does this mean that Big Rip is valid end of universe?

    Well, I prefer Big Rip over slow decay into nothingness. Big rip is fast. Puts the patient out of misery fast. If we have to return back to nothing let’s do it fast. Ah, for those who do not know, the Big Rip that I talk has nothing to do with my stockings. See http://en.wikipedia.org/wiki/Big_Rip

    The Big Crunch please Fundamentalists Christians because it matches “…the stars will fall…” mentioned in Mark 13. 25 [Source http://bible.cc/mark/13-25.htm

    The Big Bounce will please the Hindu who see the Brahma Cycle confirmed [Source http://en.wikipedia.org/wiki/Hindu_cosmology

    I do not find any end that suits me. Not even the Static Universe [Anything that goes on forever bores me in the end] This is why I am called Capricious, nothing pleases me. Trying to please a dumb blond is a hard task for intelligent scientists

  70. ad

    Void model ruled out? Maybe not, worth a look: http://arxiv.org/abs/1012.3460

  71. So if the universe is infinite and the farthest a galaxy is, the fastest it is accelerating away from us, then the farthest galaxy from us is moving away from us at light speed. Then the universe is not infinite, but at the same time, it is. Just a random thought.

  72. PeterA

    @Matt
    No, not inverse time.
    Velocity. in km/s.

    You do not seem to understand the way fractions are written. For example, hopefully you know 9.81 m/s^2? It can be written 9.81 m/s/s.
    9.81 m/s/s for 1 s = 9.8 m/s * 1s = 9.81 m/s
    so …

    At 1 megaparsec away:
    74.2 km/sec/mpc * 1mpc = 74.2km/sec

    At 2 megaparsecs away:
    74.2 km/sec/mpc * 2mpc = 148.4km/sec

  73. I always found the km/sec/megaparsec units a bit odd – there are two units of distance in there, which would seem like they cancel out and give the rate of expansion as 1/s, or Hz, meaning the expansion is a frequency.

    The frequency is roughly the age of the universe. If it weren’t for factors like gravity and dark energy affecting the expansion, it would be exactly the age of the universe.

  74. Perhaps slightly more human sized:

    Over the diameter of the Earth, space is expanding at roughly a third the diameter of an atom per second (about 0.03 nm/s).

  75. Matt McG

    Sometimes I seriously think things like this have a biocentrifugal (like that?) aspect to them… that life/consciousness/observation is helping to cause “the answers” to recede away from us.

    It is probably just my own necessary rationalization so that I can deal with how mysterious the universe is (I fool myself into believing it’s “awesome” that we’ll likely never know everything we want to), but if anyone has an understanding of biocentrism or related ideas, wanna chime in on whether I’m being a fanciful pop physicist?

  76. Yavor

    Hi all,

    Please correct me if I am wrong but being curious I have made some calculations and it seems that if the Universe is 14 billion years old (or so but calculated with that figure) and if the speed of light cannot be reached by any object save from those without mass at the borders of our known universe if there are galaxies or even atoms they should be traveling with speeds above that of light if the above number is correct:

    14 000 000 000 in megaparsecs is 4292 (1 megaparsec equals 3 261 636 light years)

    300 000 / 73.8 is 4065

    That is at 4065th megaparsec we will reach terminal velocity of light. What happens in next 227 megaparsecs?

    :-)

  77. Rabidmob

    Is this when measured from Earth to the Object or is it measured from a central universal point to the object?

    If it’s measured from the Earth, that leaves an odd center of the universe feel or is it Entropy directly at work?

  78. Brad

    This blog entry reminds me of a scene from Annie Hall when the young Alvy Singer and his mother are at the doctor’s office. Alvy’s depressed because the Universe is expanding. His mother says,

    What has the universe got to do with it? You’re here in Brooklyn! Brooklyn is not expanding!

  79. Curious

    Just an observation but 73.8 km/s/mparsec is 22.6 km/sec per million light years. If the universe is about 13.7 billion years old then from are destination to the edge of the observable universe would mean that the universe is expanding at 22.6*13700=roughly 300,000km/sec, which is the speed of light!….So this might be a bit of a stretch but couldn’t the expansion of the universe be directly correlated with the speed of light therefore meaning the expansion is just time passing….

  80. Themos Tsikas

    I prefer to see it as inflation. Space is being devalued at a rate of 0.00755% every million years.

  81. The need for Dark energy is because it is not understood that when Hubble’s linear red shift observations are extended to very far distances the energy of the photons approach zero slower and can never become negative. When the distance determined from the red shift is compared with the distance from the corresponding type Ia supernovae it is believed/speculation that the very far stars/galaxies had accelerated resulting in the need for dark energy. Also the red shift does not correspond to velocity but only an “apparent Doppler effect” as stated by Hubble.
    Red shifts can be caused by gravitational effects such as photons from our sun. Einstein’s General relativity can explain the effects of gravity on photons.

    Also, there no direct observations of the receding velocity of galaxies.

    The need for Dark matter is due to the belief/speculation that Newton’s law is also valid at very large distances outside our solar system. When applied to cosmic observations it is necessary to invoke Dark matter to explain/speculate the inability to use Newton’s gravitational constant. Analysis suggests that my theory of additional gravity. TAG, can fit the observations by adding a linear dependence on distance to the gravitational constant, and is not significant in our solar system.

    For details do a Google search on “sol Aisenberg”

  82. jay

    Can someone please explain this:

    If we have two galaxies say 5000 megaparsecs apart, does the distance between them increase 5000 * 73.8 km /sec = 369 000 km/sec?

    That seems to exceed the speed of light, but is nonetheless the relative speed between two galaxies. Confused..

    Thanks

  83. Nigel Depledge

    Philip Helbig (40) said:

    The name “dark energy” is one of the biggest goofs in the communication of science. As Sean Carroll pointed out, everything has energy and lots of things are dark, so the name really tells us very little. (He suggested the much better name “smooth tension” which emphasises the key aspects.) It suggests an affinity to dark matter which simply does not exist, as far as we know. Dark Flow? Can you say “bandwagon”?

    Perhaps so, but “dark” also means “unknown”. Hence, the Dark Ages (before we learned more about them). Dark Energy might not be the best name, but it certainly implies an energy of whose nature we are ignorant.

  84. Gil

    So, can we build a big reel with weighted cords wrapped around it and let it unwind with universal expansion to get some free energy?
    /not a physicist

  85. Currently, the thought is that there is now way to use dark energy to power your toaster. For that reason, i don’t like the idea of using e = mc^2 to claim that dark energy is 70% – ish of the Universe.

    One thought is that the sum of the energy of the Universe is zero. When you toss an apple into the air, you start with some kinetic energy (speed) and it gets converted into potential energy (height). One of these energies has the opposite sign of the other, and if you add the two together, you get a constant. For the Universe, you add them together and get zero. And, the discussion continues by saying that Dark Energy doesn’t change this idea.

    So, the total energy of the Universe is zero. We live in the error bar.

  86. vel

    can someone explain why it is always said that galaxies are “rushing away from us” when we know the Milky Way will in fact collide with other galaxies and we’ve seen the remains of other collisions? I keep hearing how this is the reason we know that the universe is expanding, that everything moving away from everything else, but that is obviously not the case. So why is it claimed that way? The old analogy of either a balloon or “raisin bread” fails miserably as soon as one galaxy impacts another.

  87. Dave in Calif

    What if it is something not from inside our universe pushing/pulling everything apart, but outside and as the galaxies get closer to the source, you know square of the distance stuff, they would appear to accelerate. Until they came into contact with the “source”, so gravity still rules.

    Dave

  88. Themos Tsikas

    The raisins can slide on the balloon, as it were, responding to the gravitational attraction of each other.

  89. CB

    @ Vel;

    Simple. They’re only saying everything is moving away from us if they’re being sloppy or just casual, when they mean that nearly everything is rushing away from us, with the only exceptions being nearby objects. Every object has its own velocity in space, but at sufficient distances their velocity relative to us is dominated by expansion and so they are all moving away. Andromeda is very close by, so it’s movement away from us due to expansion is relatively small compared to it’s movement in space-time towards us.

    The raisin bread analogy and balloon analogies fail to describe this, in part because the scale is off, and because you’re intended to imagine the raisins as not moving on their own. If the raisins are supposed to be galaxies, then they do move, but not very fast at all compared to the rising of the bread except at very close distances. However, if the entire universe is supposed to be a loaf of bread, then the Milky Way and Andromeda would be like two atoms within the same raisin, or subatomic particles in one of the atoms of a raisin.

    Those analogies are meant to illustrate the principles of 1) how everything can be moving away from us, without that implying that we are at the “center”, and 2) how there is a relationship between how far away something is, and how fast it appears to be receding.

    At the scale of those analogies, the motion of the individual objects in the universe is irrelevant.

    Hope that helps.

  90. Torbjörn Larsson, OM

    So there.

    @ #14:

    Matter at hand was dark energy, not dark matter. Both are tested by standard cosmology, this was about new tests and how other theories fail.

    “One is reminded of biology that was purely descriptive – huge catalogs of rationalizations – until genomics came along”

    Niles Depledge (#17) has the expertise here, but my personal impression is that this was the main point of the New Synthesis, marrying quantitative stuff like population genetics with basic evolution theory. This happened 1936-1947 (Wp), so before DNA was known to code for proteins (1953 – 1958).

    @ #20:

    “the energy that blew the original dingus apart is still, as it were, blowing. Is that it?”

    No. The initial expansion is, within the standard cosmology, caused by inflation AFAIU. This, dark energy, is a negative pressure in general relativity terms. It was always there, but now it is dominant since the other parts of the universe has become too diluted (ie their effects on expansion too weak).

    @ #22:

    “Big Rip is valid”

    There is no “Big Rip” in standard cosmology, you would need new physics.

    @ #31: How would you measure a change in rate of time? You can’t, so your idea can’t be tested. Yes, time is _that_ fundamental.

    But FWIW, the overall direction of time is set by the very universal expansion we are studying.

  91. Torbjörn Larsson, OM

    @ #56:

    You are in effect claiming that general relativity isn’t a fact. That is rejected by the GPS locator in my cell in my pocket: general relativity is needed to predict the corrections so the locator can get a signal to lock.

    Isn’t it wonderful how relativity can be seen in our daily lives? First magnets and then electronics (special relativity), now GPS (both special and general relativity).

    @ #61: Read the post again, it tells you such ideas are just thrown out, for good. The near outside universe is of the same density as the local.

  92. Themos Tsikas

    “What if it is something not from inside our universe pushing/pulling everything apart, but outside and as the galaxies get closer to the source, you know square of the distance stuff, they would appear to accelerate. Until they came into contact with the “source”, so gravity still rules.”

    That assumes that we are at the centre of the universe and it only looks as it does because we are at a special point. We don’t do cosmology like that, we assume that what we see is typical of the view from everywhere.

  93. Joseph G

    Pardon me if this is a dumb question or if it’s already been answered (it was a long night for me), but how does increasing the certainty of distance measurements using standard candles allow for accurate observation of the speed of universal acceleration? I thought that red-shift was more or less the gold standard in this area. I can see how measuring distance is important, but can you actually measure distance over time using supernovae and cepheids to a high enough resolution that you can get speed and acceleration out of it, too?!?

  94. Notsosmart

    This gives me a chance to ask a question I’ve had that really needs to be knocked out of my head. Could the universe’s acceleration be due to something like gravity gradually weakening? If space is expanding at a constant rate with matter riding along, gravity between the bits of matter should slow down the separation between the bits with respect to the rate of expansion. But if gravity were very slowly losing its grip, then the speed of separation would increase, kind of like a cork that was dragging against something in a stream and is now floating more freely with the current.

  95. Dutch Railroader

    @66

    The relationship between true distance and redshift is function that changes depending on the cosmological distance model. You must measure accurate distances to get both variables.

  96. Joseph G

    @55 Themos: I prefer to see it as inflation. Space is being devalued at a rate of 0.00755% every million years.
    Win.

    @60 vel: can someone explain why it is always said that galaxies are “rushing away from us” when we know the Milky Way will in fact collide with other galaxies and we’ve seen the remains of other collisions? I keep hearing how this is the reason we know that the universe is expanding, that everything moving away from everything else, but that is obviously not the case. So why is it claimed that way? The old analogy of either a balloon or “raisin bread” fails miserably as soon as one galaxy impacts another.

    The important thing is to differentiate between the expansion of spacetime and actual motion of objects through space.
    First, imagine a non-expanding universe, where galaxies are moving more or less randomly, but affected by one another’s gravity, so that they form clusters and sometimes collide. We see this happening.
    Now, add in the expansion of space itself at large scales. Galaxies still move around and attract one another, but on large scales, the expansion of space overwhelms local motion, causing distance between objects to increase. Two objects can actually be moving toward one another (each moving through space toward the other when seen from a local reference frame) and yet the distance between them may continue to increase if they’re far enough away for universal expansion to dominate.
    It’s hard on the ol’ noggin to picture, I know. Our hominid brains aren’t designed to deal with these kinds of things. Full disclosure, this is my imperfect understanding of how to picture it, so I may be dead wrong, too, of course :P

  97. jess tauber

    Re: #47- Thanks, Matt

    Here’s what I MIGHT make of it-

    1.3 is close to 1.38…, which is is 2-phi (the smaller value of the Golden Ratio, as (sqrt5-1)/2 ), and -.61 is close to -.618… phi, again the smaller Golden Ratio.

    Both these values are found in a whole slew of spacing and timing aspects of natural phenomena from the biggest to the smallest. For ex. the average nucleotide composition in large stretches of DNA, or the Periodic Table, the ratio of protons to neutrons in nuclei with increasing atomic number, quasicrystals, metal alloys and coordination compounds; orbital and rotational dynamics in cosmology. Not *perfectly*- there are variations, holes, errors, but these themselves tend to hint at further associated organization.

    The expansion rate varies over time- but perhaps also over space- a 4D cellular structure? That might be what one should expect if the Golden Ratio is involved- growth and packing constraints.

    Remember folks, and Phil- you read it here first

  98. Buzz Parsec

    MTU- It’s 45.9 miles/sec/megaparsec… Getting closer to the correct value, which is obviously 42. It might come out right if measured in AU/fortnight/megalightyear or some other units. Try everything!

  99. Messier Tidy Upper

    @ ^ Buzz Parsec : Thanks! :-)

    @86. Stephen :

    For the Universe, you add them together and get zero. And, the discussion continues by saying that Dark Energy doesn’t change this idea. So, the total energy of the Universe is zero. We live in the error bar.

    Or in other words, the universe is just a big fat zero! ;-)

    Nothing comes of nothing? Everything *is* nothing! ;-)

    @94. Joseph G :

    Pardon me if this is a dumb question or if it’s already been answered (it was a long night for me), but how does increasing the certainty of distance measurements using standard candles allow for accurate observation of the speed of universal acceleration?

    Not a dumb question at all. They say the only dumb questiuon is the one that goes unasked! Although, yeah, there *might* be exceptions to that rule. But NOT your one tho’. ;-)

    The answer has to do with refining calculations – if we know more precisely where Cepheids are then we can work out from there, to how fast the universe is expanding for them to appear as bright as they do.

    I thought that red-shift was more or less the gold standard in this area.

    I gather Supernovae esp. “white dwarf” type Ia supernovae which are most consistent and Cepheids are better or at least less complicated standard candles but I won’t swear to that.
    Redshift can be confusing in that there’s also other forms of redshift such as gravitational redshift, which, I think, might complicate things but again not entirely 100% sure about this myself.

    I can see how measuring distance is important, but can you actually measure distance over time using supernovae and cepheids to a high enough resolution that you can get speed and acceleration out of it, too?!?

    Yes, I think so.
    Cosmology isn’t exactly my area of expertise but that is my understanding such as it is.

    If I may I’ll recommend Tim Ferris’es The Whole Shebang book to folks as a readable and interesting guide to cosmology. Time I re-read it myself actually! ;-)

  100. Messier Tidy Upper

    See :

    http://en.wikipedia.org/wiki/The_Whole_Shebang:_A_State-of-the-Universe(s)_Report

    For the book by Tim Ferris mentioned above. :-)

    http://en.wikipedia.org/wiki/Redshift

    for redshifts – there’s gravitational & cosmological included under that.

    Plus try :

    http://www.asterism.org/tutorials/tut29-1.htm

    For an online piece by Mike Luciuk on redshift’s and their various varieties. :-)

  101. Messier Tidy Upper

    Also see:

    http://www.bautforum.com/archive/index.php/t-105657.html

    For a BAUT forum discussion of this.

    Whilst :

    http://www.experts123.com/q/do-astronomers-take-into-account-gravitational-redshifts-when-they-compute-the-cosmological-redshift-of-a-distant-galaxy.html

    says there’s not so much an issue with gravitational vs cosmological redshift – at leats for the expert cosmologists .

    Additionally, there’s :

    http://curious.astro.cornell.edu/question.php?number=278

    For ask-an-astronomer’s explanation on the redshift topic. :-)

  102. Scott Daris

    @#98 Is the entire galaxy spiral made up of the golden ratio spiral? If so, in perfect future perfect, I will have shat myself upon learning this.

  103. Nigel Depledge

    Notsosmart (95) said:

    This gives me a chance to ask a question I’ve had that really needs to be knocked out of my head. Could the universe’s acceleration be due to something like gravity gradually weakening? If space is expanding at a constant rate with matter riding along, gravity between the bits of matter should slow down the separation between the bits with respect to the rate of expansion. But if gravity were very slowly losing its grip, then the speed of separation would increase, kind of like a cork that was dragging against something in a stream and is now floating more freely with the current.

    This is an interesting question.

    I think the easiest way to come to grips with it is to remember that the expansion of space is not governed by gravity.

    The movement of galaxies within that expanding space is, however, governed purely by gravity.

    That is, if I have correctly understood BB cosmology and GR (and bear in mind I have never attempted to get to grips with the maths of these ideas – non-Euclidean geometry makes my head hurt).

  104. Wilson

    Please would someone answer a stupid question that has been troubling me for years.

    The further out we look, the further back in time we look, so shouldn’t the galaxies be closer together out there as they were just after the Big Bang?

    It seems to me that the further out we look, the more dispersed they are in every direction, so how can we be looking at a time just after the Big Bang?

    If the universe is indeed 14 billion years old then there should be a point beyond which there is nothing. Hubble sees near the edge of the universe in every direction, we are told, but this edge is equidistant from Earth, and is too geocentric a view, to be acceptible.

    Thanks in advance.

    Wilson

  105. Tuttle

    Wilson: Inflation is the terse answer to all three questions.

    The further out we look, the further back in time we look, so shouldn’t the galaxies be closer together out there as they were just after the Big Bang?

    Draw two points on a deflated balloon. Now blow it up. The points were close when the inflation started but get further away as the balloon increases in size.

    It seems to me that the further out we look, the more dispersed they are in every direction, so how can we be looking at a time just after the Big Bang?

    Trickier. The balloon is a two dimensional example. Expand the metaphor to four dimensions and this becomes more understandable. We see a part of the time after the big bang. The part within 14 billion light years of us.

    If the universe is indeed 14 billion years old then there should be a point beyond which there is nothing.

    Debatable, but if there is a point beyond which there is nothing (not empty space, NOTHING) it is much further away than we can perceive since the universe expanded faster than the speed of light at some point (and as this math seems to indicate, still is out on the edges).

    Hubble sees near the edge of the universe in every direction, we are told, but this edge is equidistant from Earth, and is too geocentric a view, to be acceptible.

    That’s just bad semantics. The universe is 14 billion years old so all we see is stuff within a sphere 14 billion light years in radius. That’s the “edge of the universe” as far as our perception goes, but the universe is bigger than 28 billion light years in diameter. It is a geocentric view, but that’s because we have no other vantage point.

  106. Dutch Railroader

    @wilson

    You are completely correct. There is a relationship between the angular-size of objects, given their physical extent and redshift. The Universe was smaller at high redshift, so things will appear bigger than you would expect. A crude analogy – consider standing at the North pole and look at someone standing at the south pole with the constraint that light travels only along the surface of the Earth. You would see his head hugely magnified and actually spread completely around your horizon. Also imagine looking down a railroad track going to the south pole. For a while it would appear to converge to a point as you are used to, but it would never quite get there and as you looked further down the track it would appear to spread out again (as it crossed the equator). In both pictures the “size” of the Universe at any time is the same as a circle of latitude. If the big band occurred at a “point” right at the south pole, standing at the north pole you would see the radiation from the microwave background arriving from all directions.

  107. I RoboSapien

    Response to: Are Some Galaxies Travelling Faster Than Light?

    To those who’ve expressed the belief that distant galaxies past some point must be receding from us faster than light, you seem to have reached that conclusion by using linear math calculations. But you have to understand that extreme velocities and astronomical distances do not conform to linear rules. That’s where relativity comes in instead, and you need the basic relativity formula to calculate speeds of distant galaxies relative to us — and those speeds always come out to something less than light speed, because of the inherent nonlinearity of relativity.

    See my previous post (#47), the second paragraph, where I attempt to explain this briefly without getting technical.

    Unfortunately to really wrap your mind around the concept you need at least a nodding acquaintance with relativity theory, if not the math then at least the principles and the visual examples or metaphors used to describe how it works.

  108. I RoboSapien

    @ #86 Stephan –

    Yes, the universe has zero total energy — Stephen Hawking says he can prove this mathematically quite easily, using reasoning much like you employed. That includes all forms of energy, gravitational, expansive, electromagnetic, even dark energy if we allow the existence of such.

    In this and many other respects, infinity and zero are merely different expressions of the same thing, or the same thing looked at different ways.

  109. I RoboSapien

    @ #91 Torbjörn Larsson, OM (re your response to # 20 DrBB) –

    I hate to contradict you, but some cosmologists do credit dark energy with powering the early inflationary period, and possibly the Big Bang itself. Astrophysicist Martin Rees points this out in his book Our Cosmic Habitat. To quote him:

    “Why is our universe so big? Why, indeed, is it expanding at all? By far the most plausible answers involve a so-called inflationary phase. According to this concept, very early on, when everything astronomers now see was literally of microscopic size, the dominant stuff in the universe was not ordinary particles or radiation, but concentrated dark energy latent in the original space.”

    “The ‘dark energy’ overwhelmed ordinary gravity, generating an immensely powerful antigravity, or cosmic repulsion. The expansion was exponential; the scale doubled, then doubled, and then doubled again. And then, the fierce repulsion switched off; some of the dark energy was converted into ordinary energy, generating the heat of the primeval fireball and initiating the more familiar expansion process that has led to our present habitat.”

  110. Dutch Railroader

    @109

    SR velocity addition is not appropriate to describe the Hubble flow. Galaxies are not flying through space apart from one another, but rather space is expanding between them. In this case > c recession velocities are possible and are seen. See:

    http://arxiv.org/abs/astro-ph/0310808

    “Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe”

    We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard Lambda-CDM cosmology we point out confusions regarding the particle horizon, the event horizon, the “observable universe” and the Hubble sphere (distance at which recession velocity = c). We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests. Attempts to restrict recession velocities to less than the speed of light require a special relativistic interpretation of cosmological redshifts. We analyze apparent magnitudes of supernovae and observationally rule out the special relativistic Doppler interpretation of cosmological redshifts at a confidence level of 23 sigma.

  111. Morgan L Kramm

    Using somewhat simple applications of the laws of physics as I uderstand them there are some inconsistancies that I have stumbled upon. I know that a great many brilliant scientists that accept the Big Bang Theory is correct, but I have these doubts and would submit them for comment

    Observations of Some Inconsistencies of the Big Bang Theory of the Universe

    It would seem unlikely that the Big Bang was the beginning of the universe. The total mass of the universe had to already exist or there could not have been anything to explode.

    If the collapse of an expended star can create a black hole from which nothing can escape, how could a black hole with all the mass of the universe possibly explode and release all the mass and energy in the universe? These two theories would certainly appear incompatible.

    We should expect that all mass from an explosion will move radially away from the original position without a non-radial vector. How can we explain the collision of galaxies if this is true?

    How do we explain that all proposed velocities of observed stars in all directions are essentially the same and places Earth at the center of the explosion? It would seem highly improbable that this would be the case.

    There are some proposals that the outer reaches of the universe is expanding faster than the speed of light. That would seem highly unlikely with the laws of physics of our local solar system. It is worrisome that it is proposed that the laws of physics that apply to our local solar system may be different elsewhere. What physical evidence would justify this?

    Why do we observe stars in all stages of their lifetimes if the universe was originated all at the same time?

    We can verify that the Doppler effect is valid as a sonic frequency because we can observe it from both sides. Since there are few observations from stars coming toward us there is no verification there is a similar effect on the light in the universe.

    Trying to visualize the geometrical configuration that should be associated with the Big Bang is more difficult. If it is assumed that the Big Bang occurred 13 or so billions of years ago, then the furthest stars have been traveling away from us all that time and the light observed from them has been traveling toward us for an equal amount of time. Why would it be assumed that the light was generated at the beginning and we were already separated by that distance?

    Why not look for an energy or velocity loss mechanism for light as it passes through an ill-defined medium for eons that could cause the red shift to a lower energy light spectrum? This concept, if somehow validated, might possibly resolve some of the inconsistencies listed above.

  112. I RoboSapien

    Oh, just to add a “however” to my last, Tuttle (#107) is right, inflationary theory also says there was a period very early on (the actual inflationary period, hence the name), when space did expand faster than light. In fact many times faster. This was WAY early, though, before the separate physical properties and laws of our universe “solidified out” from the grand unified force, before atoms or particles were formed, when light speed was not yet a constraining constant. We’re talking about prior to about 10^-36 seconds (a trillion-trillion-trillionth of a second). Going forward from the Planck time of 10^-44 seconds, the smallest “time” there can be, that’s 10^8, which is a hundred million times longer than the Planck time, so RELATIVELY speaking it was a long process, even though it’s still far less than one second from The Beginning.

    This means that much of the contents of our universe today would have long ago traveled beyond the ability of its light to reach us, and would be outside our visible light sphere.

    As to some other posters’ continuing confusion about an edge to the universe (or a center), I addressed this in my earlier posting (#47), the last paragraph. Rather than repeat myself, I would refer you back to there. Admittedly this is a counterintuitive concept (as is pretty much all of modern cosmology), yet it’s what we’ve been able to figure out.

    So hold on for the ride, the Cosmic Carnival is full of strange and weird surprises!

  113. jess tauber

    @#104. Scott Daris Says:
    March 24th, 2011 at 12:54 am
    I will have shat myself upon learning this

    Luckily Branes come in rolls- help yourself.

  114. avimort

    What the new value of H means, is that the Universe is now younger than it used to be!
    if H = 73.8km/s/MPc, and Age of Universe = 1/H, and 1 MegaParsec = 3.08567 x 10^19km
    then Age = 3.o8657 x 10^19 s / 73.8
    = 4.181 x 10^17 s = 13.25 billion years
    as compared to the previous age of ~13.85 billion years!

    Don’t you all suddenly feel a lot younger!

  115. Nigel Depledge

    Morgan L Kramm (113) said:

    It would seem unlikely that the Big Bang was the beginning of the universe. The total mass of the universe had to already exist or there could not have been anything to explode.

    Er, no.

    First, this looks like an argument from personal incredulity. It may seem unlikely to you, but that is neither here nor there.

    Special relativity has demonstrated the equivalence of mass and energy, so the entire mass of the universe would have arisen from its initial energy. We do not know exactly from whence the energy came, because our best theories can only look back as far as 10^-36 sec after the big bang.

    Additionally, it did not explode, because that implies it had something to explode into, but – as far as we can tell – space itself came into existence at the big bang.

    If the collapse of an expended star can create a black hole from which nothing can escape, how could a black hole with all the mass of the universe possibly explode and release all the mass and energy in the universe? These two theories would certainly appear incompatible.

    Stephen Hawking worked out that black holes evaporate (nearly 40 years ago! Get with the programme). Although the BB started from a spacetime singularity, it was not necessarily a black hole.

    Also, the universe can still be considered to be a black hole, but I do not understand this interpretation. Here I have to trust the experts to know what they’re doing.

    We should expect that all mass from an explosion will move radially away from the original position without a non-radial vector. How can we explain the collision of galaxies if this is true?

    First, it was not an explosion.

    Second, when an artillery shell on Earth explodes, how come the fragments all fall to Earth afterwards? The answer to this question is the same as the answer to your question – gravity.

    How do we explain that all proposed velocities of observed stars in all directions are essentially the same and places Earth at the center of the explosion? It would seem highly improbable that this would be the case.

    This is not the case. BBT does not require this to be the case. The space between objects is expanding, regardless of the individual velocities of those objects.

    There are some proposals that the outer reaches of the universe is expanding faster than the speed of light. That would seem highly unlikely with the laws of physics of our local solar system. It is worrisome that it is proposed that the laws of physics that apply to our local solar system may be different elsewhere. What physical evidence would justify this?

    Some preceding comments have answered this already.

    From our frame of reference, distant objects may be receding at velocities exceeding c. But those objects are not exceeding c in their movement locally through space. The space between us and those objects is expanding rapidly enough for their recession velocities to exceed c.

    Why do we observe stars in all stages of their lifetimes if the universe was originated all at the same time?

    Because star formation takes time, and requires the right conditions to occur. Most stars that we observe are third-generation stars (i.e. they contain enough elements heavier than He that we know they cannot be primordial stars). Why would you expect stars to all be the same age?

    We can verify that the Doppler effect is valid as a sonic frequency because we can observe it from both sides. Since there are few observations from stars coming toward us there is no verification there is a similar effect on the light in the universe.

    First, this is wrong. Some local galaxies are moving towards us, and their light is indeed blue-shifted. Second, there are plenty of ways in which we can verify the Doppler effect for light here on Earth, in exactly the same type of experiment as you might use to verify it for sound.

    Trying to visualize the geometrical configuration that should be associated with the Big Bang is more difficult. If it is assumed that the Big Bang occurred 13 or so billions of years ago, then the furthest stars have been traveling away from us all that time and the light observed from them has been traveling toward us for an equal amount of time. Why would it be assumed that the light was generated at the beginning and we were already separated by that distance?

    The galaxies’ redshift in relation to the cosmic microwave background tells us what proportion of the time since the big bang has passed in the journey time of that light. This would apply irrespective of when the big bang occurred.

    What exactly is the problem here?

    Why not look for an energy or velocity loss mechanism for light as it passes through an ill-defined medium for eons that could cause the red shift to a lower energy light spectrum? This concept, if somehow validated, might possibly resolve some of the inconsistencies listed above.

    Who’s to say that people have not already sought such things?

    It seems that you are not familiar with exactly how red-shift is measured, because a little more understanding of the details would clear up some of your issues immediately.

    When red-shift is measured, it refers not to the peak emission of the galaxy’s spectrum, but to the atomic absorption lines within that galaxy’s spectrum. These lines form distinctive patterns, so it is always possible to identify the absorbance lines for (say) Hydrogen by how far apart from one another they are in the spectrum. Where in the spectrum those lines occur (relative to where they occur in static experiments on Earth) tells us the amount by which the light has been red-shifted.

    Here on Earth, there are only two things that can cause light to red-shift : gravity and the Doppler effect. Since these two components can completely account for the red-shifting of the spectral lines we observe, there is no need to invent something else unknown in the intergalactic medium to account for it.

    The “inconsistencies” you describe are not inconsistencies in the theory, but in your understanding of what it states.

  116. I RoboSapien

    @ #112, Dutch Railroader

    Okay, I stand corrected. However, in my defense I was merely trying to point out the common lay person’s fallacy of applying simple linear math to nonlinear phenomena, while steering clear of technical complexities and terminology which are unfamiliar to most — and which are more confusing than clarifying, especially when left undefined (as, unfortunately, is the jargon you used…sorry). Consequently I left a great deal out of my cursory explanation.

    Of course, I suppose I am not as up-to-date and deeply immersed in current cosmology theory as are some. So forgive my indiscretion.

    My advice for people who want real answers: Study actual research results and read quality books on the relevant subjects, don’t rely on word-of-mouth sound bites or comment postings.

  117. jess tauber

    Ok, here’s a wild take- the cosmic equivalent of plate tectonics. New spacetime is being created all the time either everywhere or more where there isn’t any, or not much, normal matter. Matter is consolidated when larger bodies of it are close together, but clumps at great distances are flying apart because of expansion.

    If the tectonics analogy is apt then there should be somewhere where spacetime is being ‘subducted’- black holes. The question then becomes where does it come out again? And how?

    Jess Tauber

  118. Wilson

    Interesting stuff, but mathamatical models of the universe have to be fudged incrementaly to create the latest theory, ever since Einstein invoked his “cosmological constant”. Today we invoke other non observable phenomona to make the mathematics fit, i.e. “dark matter”, “dark energy”, “branes”, “strings”, and such. And, of course “inflation” which is invoked to explain inconsistancies in the rate of early expansion.

    Those who arrogantly tell us they know what was happening at 10^-36 sec after the big bang, when the BB theory itself is a fudged theory make me laugh!

    The emperor has no clothes!

    A lot relies on the “red shift” doppler effect but if we have the arbitrarily invoked “dark matter, and “dark energy” dominating the universe and it has yet to be observed or explained, who’s to say that light travelling through dark matter and dark energy isn’t red-shifted for other reasons than velocity?

    Expanding space is also consistent with shrinking matter!

    Given enough invoked unobservable factors, mathematics can be cobbled to fit any theory, but it is admitted by most experts, that all our present models of the universe are incomplete.

    Beware of “fudge factors”.

    It is far better to stick with observable evidence and admit we don’t know the how, where and why of the universe, than to, like the AGW folks, dismiss all sceptisism, be saying “the science is settled”

    What a poor legacy we leave for future brilliant minds, if we insist that the BBT is the only valid explanation of how and why we are here!

  119. I RoboSapien

    @ #120 Wilson –

    I think you’ve got it wrong. Science is never truly “settled” or written in stone. (Engineering or a piece of technology might be considered “settled” based on the fact that it works, but theoretical and experimental science is always open to better data.)

    While scientists may speak with confidence about a certain theory that’s backed up by solid evidence, if they’re truly scientific then they know that’s just the current best understanding based on the available evidence, but that it’s always subject to revision should we get better data. Sometimes new evidence leads us to whole knew ways of looking at things. When that happens scientists alter their view to match the evidence. Science is ALWAYS about gaining more data and refining our understanding based on evidence. Certainly we must form theories to explain the evidence, but that’s what “understanding” means. We may have wrong theories; honest scientists recognize this and stay open to new ideas. But those ideas or theories must fit the observed facts.

    Other times new evidence confirms or reinforces the existing theories. This has been the case with the Big Bang theory. An enormous amount of evidence from many different fields converges independently upon the same conclusion. Yet there are many scientists who would love for something to come along that disproves the Big Bang. The BB theory was in fact only accepted reluctantly in the first place, as the best explanation that fit the observed data — many scientists fought hard to find some alternative because they did not want to believe such an outlandish idea as a universal Big Bang. Now, of course, we have ultra-high-energy particle accelerators that can duplicate the energies of the very early moments of the (hypothetical) Big Bang, and we have a map of the cosmic background radiation which is essentially a picture of the fireball left over from the Big Bang, and we understand nuclear processes and stellar formation and galaxy dynamics, and we can measure red shift (as well as blue shift in galaxies we know are moving toward us, so there is some good evidence that red shift is a function of velocity), and we can see the gravitational effects of something in the universe that we can’t otherwise detect and so we give it a name, dark matter. All this converging data and the theories built up around them fits together and can be extrapolated back to within a millisecond of the Big Bang with 99% confidence, according to cosmologists (the 10^-36 figure is purely speculative, the millisecond figure is based in actual measurements of particle energies and the like).

    So of course our models of the universe are incomplete! Of course we try to stick to observable evidence and admit that we don’t know it all. But we don’t dismiss our best understanding BECAUSE we don’t know everything. Science is an unfolding process. We operate on what we have in front of us now, while staying open to better ideas in the future. That’s why we speak of the Big Bang theory AS IF it were true, because our best evidence points us there. We didn’t WANT to go there, the universe dragged us there kicking and screaming.

    So it’s not arrogance. It’s actually humility. Those who deny the evidence and instead operate on speculation or dogmatic belief — I’d say that’s arrogance.

  120. Nigel Depledge

    @ IRoboSapien (121) –
    Yes! This!

  121. Nigel Depledge

    Wilson (120) said:

    It is far better to stick with observable evidence and admit we don’t know the how, where and why of the universe, than to, like the AGW folks, dismiss all sceptisism, be saying “the science is settled”

    OK, I’ll bite.

    Which climate scientist(s) said that the science is settled? When and where did they say it? And is there a wider context than you are providing?

  122. Nigel Depledge

    Wilson (120) said:

    What a poor legacy we leave for future brilliant minds, if we insist that the BBT is the only valid explanation of how and why we are here!

    Why?

    Cosmologists know it is, at best, incomplete. They are seeking better theories. However, inflationary BBT is better than all of its predecessors. It at least accounts for pretty nearly all the observed facts.

    Thus, we can be fairly confident that BBT is a pretty good approximation for how the universe began, even if aspects of it are wrong. If it were wrong in any major way, we would already know by now.

  123. DrBB

    @111. I RoboSapien

    Thanks for your very lucid explanations throughout, and @111 (in response to a query of mine, once removed) in particular. The quotation does seem to confirm in a more detailed and accurate way what I was imagining the relation between dark energy, the BB and the expansion of space-time to be. I’m never going to get beyond the For Dummies stage with this stuff–defeated by the math, alas–but I like to have a reasonably sound lay-person’s grasp of it. Fascinating stuff.

  124. I RoboSapien

    @ 122 Nigel DePledge –
    and
    @ 125 DrBB –

    I appreciate your notes of acknowledgement. Nice to get that now and then. And good to know that reasoned minds are in the fight for truth and higher understanding.

    Oh, DrBB, FYI: Cheer up, we don’t all have to be mathematicians or specialists to grasp concepts, general ideas or principles — as long as they’re presented clearly (an uncommon occurrence, I know, yet a treasure when found).

  125. Nigel Depledge

    IRoboSapien (126) said:

    Oh, DrBB, FYI: Cheer up, we don’t all have to be mathematicians or specialists to grasp concepts, general ideas or principles — as long as they’re presented clearly (an uncommon occurrence, I know, yet a treasure when found).

    Seconded.

    I have at least some understanding of such theories as quantum mechanics and Big Bang cosmology, despite never having got involved with the maths (the closest I came was when I was in a 3rd-year Chemistry lecture at Uni – my “major” being biochemistry – and when the lecturer mentioned ab initio molecular orbital calculations, several of the chemistry majors groaned and dropped their heads to the desk). But in that instant I became aware of two things I had not previously known – first, that it is possible in principle to calculate (as opposed to measure) the behaviour of electrons in a molecule; and, second, that it is fiendishly difficult even for a molecule of hydrogen, and may be impossible for very complicated molecules.

  126. I RoboSapien

    @ #127 Nigel Depledge –

    Now if only we could synthesize quantum theory with relativity theory!

    There’s hope, though. Here’s what Tom Siegfried says in his book Strange Matters; Undiscovered Ideas at the Frontiers of Space and Time (I hope this quote falls under Fair Use laws, or at least that Tom and his publisher will permit me this indulgence, purely for educational purposes or as free advertising for the book — read it, people!). This is from his exposition on Unity and Harmony and “the unreasonable effectiveness of mathematics”:

    “Poincaré understood how this process works. Imagine, he says, a chart depicting all ‘the variations of the world.’ At each point in time everything in the universe is in a particular arrangement. At the next instant the arrangement will be slightly different. (The differences from one instant to the next would be the result of the combined operations of all the laws of physics.) A graph of those changes over time would take the shape of a curve. A good mathematician could figure out an equation to describe that curve.”

    “But earthbound mathematicians can never see the whole curve. Human theories are always based only on one arc, one piece of the universal curve. Two theories based on different arcs might deduce different equations to describe the whole curve. (Quantum mechanics and general relativity describe different aspects of reality exquisitely well, for example, while appearing to be incompatible.)

    “However, Poincaré notes, a greater intellect, or a similar intellect with a wider field of view, could perceive the region between these two arcs and construct a better equation. That equation could describe not only both arcs but also the part of the curve in between. And sometimes human scientists can figure out that better equation before they see the whole curve. If they get the right equation, it will then tell them things about regions of the curve that have not yet been measured.”

    Science is about filling in the missing points on that larger universal curve, one tiny dot at a time. It is the epitome and acme of being human, of what makes us intelligent beings.

  127. Nigel Depledge

    @ IRoboSapien (128) –

    I have no answer for that, other than the immortal words of Hazel O’Connor:

    What’s done has been done
    And I won’t be the one
    Who despairs in the wheelchair
    At the sight of “if only”

    So I’ll stand up again, and I’ll run
    I’ll jump up ’til I touch the sun
    Because I won’t be the one to be bound
    By the sound of “if only”.

    ;-)

  128. I’m not entirely convinced on this “theory” of an expanding universe. An analogy would be a nat sitting on the south end of a north bound elephant, trying to explain the trunk. As we all are aware, light can be deceptive. Hey…wait till we discover that there are multiple unverses (perhaps billions) out there. That will put a whole new perspective on things. Just a thought.

  129. Nigel Depledge

    Rebel (130) said:

    I’m not entirely convinced on this “theory” of an expanding universe.

    Well, lucky for you it ain’t a theory. It’s a conclusion. A conclusion drawn by logical reasoning from hard data.

    Even proponents of the “steady-state” universe (such as Fred Hoyle, who coined the term “big bang” as a derogatory nickname for the theory that the universe had a beginning) accepted that the universe was expanding. Why? Because the measurements are irrefutable.

    An analogy would be a nat sitting on the south end of a north bound elephant, trying to explain the trunk. As we all are aware, light can be deceptive.

    Er, no. Not when one understands general relativity.

    Your analogy fails, because the trunk is not expanding, and is not covered in sources of information that are sending that information to the gnat.

    Hey…wait till we discover that there are multiple unverses (perhaps billions) out there. That will put a whole new perspective on things. Just a thought.

    And, until there is evidence on which to base some conclusions, your “just a thought” will remain a piece of idle speculation.

  130. Bucho

    After reading all these articles and watching shows on how the Universe is expanding I never hear anyone talk about one fundamental question: “What is the Universe expanding into?”

    It seems to me that if you want to know about what is causing an expansion of a body (say creation itself) it would only make sense to know what that body is expanding into. To me it seems that the Universe is expanding because the area its expanding into is well…..nothing. If that is the case isn’t it possible that its expanding due to wanting to have equilibrium? As for acceleration its accelerating due to the surface area that needs to expand is constantly growing. As the universe grows so does the surface area that is bordering the nothingness and hence the acceleration increases.

    Its a simplistic approach to the topic but one I wanted to at least throw out for debate.

  131. Allen

    97. Joseph G: Two objects can actually be moving toward one another (each moving through space toward the other when seen from a local reference frame) and yet the distance between them may continue to increase if they’re far enough away for universal expansion to dominate.
    It’s hard on the ol’ noggin to picture, I know.

    Am I noggin-grasping the concept with this (layman’s and very rudimentary!) analogy?

    I have a blue marble on a 15-degree-right-inclined plate o, and a green marble on a 15-degree-left-inclined plate o/. The blue and green marbles are rolling toward each other, yet the plates are separating; the plates are moving farther apart faster than the marbles are rolling toward each other, thus netting the universal expansion result above. IIUC, that involves only one local reference frame (a point on an equivalent plane to the plates) vs two (the former point, plus a point on an equivalent plane as the marbles) from which to deduce the theory.

    ATM, I’m at a loss to better explain what I hope to further understand. Fascinating, all! :)

  132. Montaray Jack

    How could one differentiate between dark energy accelerating the expansion of the universe and time approaching Proper Time in the expanses between clusters?

    In the voids, time would be faster than in the inertial frame of reference of the galaxies. I would think that time distortion would follow the same inverse square law as gravity. Or has this been accounted for in the calculations?

    Ever since I first read about the experiments to measure the expansion, this bit about relativity and time distortion near masses has been bugging me, but unlike cosmologists, my math skills are nowhere near good enough to work out Einstein’s field equations for myself.

  133. zuma

    1. The reasons why the data that have been gathered for red shift and blue shift from the observation of galaxies through the use of telescope might not be served as a guide that the world would be expanding:
    a) The accuracy of the telescope that has been used to determine whether the galaxies would be in red shift and blue shift in order to conclude that the galaxies would moving away or towards the earth could be in question. In short distance of viewing an object, the telescope could identify accurately the change of the size of planet from big to small or small to big so as to give signal whether it should be in blue shift or red shift. However, if the object is placed very far away from telescope, the object that is shown in the screen on the telescope would be very small. The telescope might turn up to show one signal as a result of its inability to identify the accuracy of change of size of the object as if that all the galaxies are moving far away from the earth. Or in other words, it might have given wrong signal that the world would be expanding due to the inaccuracy of the telescope since it might be accurate in short distance with a big object and yet it might not be accurate if if would be in very small and tiny object that would appear on the screen when it would be placed many miles far away from the earth. Thus, the accuracy of the telescope might be in question since it has not been tested whether it could be accurate when objects would appear to be very tiny and small on the screen..
    b) The telescope might have been tested on earth to be accurate in short distance and yet it has not been tested from one galaxy to another so as to determine whether it is still accurate to measure the movement of object in the galaxies that is located in many miles far away from the earth.
    c) If you would blow a balloon, all the substances in the balloon would be shaken and vibrated. Even if they would be creatures inside the balloon, all the creatures would feel the strong pressure, i.e. wind, pulling them towards the corner of this balloon. Why is it that we that are on earth would not feel the pressure that the earth would be expanding? As we know if we blow the balloon, all the things in the balloon would fly away and would turn up to be in messy order. Question has to be raised. Why is that the air would still remain on earth despite the great pressure that has caused galaxies to advance as a result of expanding? No matter the pressure would externally influence as a result of the world expanding, nothing has affected the earth and it seems to be that something is controlling the earth to make it a secure place. Religious people call it, God.
    d) If you blow a balloon, all the substance would go travel towards the corner of this balloon. Let’s use blowing balloon to explain the galaxies. Let’s assume that you blow from the Sun, you would certainly see blue shift as well as red shift since some galaxies would move towards the earth from Sun. If you would blow from the Pluto, the same, you would still see some galaxies moving towards the earth since there are some galaxies from the sun would move towards the earth from the Pluto. However, if you would blow from the earth as a centre outwards, you would then see all galaxies would be moving far away from the earth. Now question has to be raised. The assumption that all galaxies would have been moving far away from the earth seems to presume that the earth would be stagnant and all galaxies would be advancing away from the earth. As the earth would turn up to be the centre of the universe, it turns up that a person would view from any side of the earth would turn up to be that all galaxies seem to moving away from earth. This seems to be weird and irrational.
    The reliability of data gathered from scientist that the world would be expanding is in question.

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