Comments on: The Universe is expanding at 74.2 km/sec/Mpc

By: The Best Dating Products

The Best Dating Products — Sat, 30 Jun 2012 14:20:54 +0000

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By: malectric

malectric — Sat, 05 May 2012 05:55:04 +0000

Please forgive typos in what I just submitted. They should be obvious.

By: malectric

malectric — Sat, 05 May 2012 05:53:59 +0000

I see a revolution in perception and interpretation of observations coming (from someone much brighter than me). Some things about “observed” expansion rates bother me enormously. For example, I often see it said that such-and-such a galaxy is x LY away from us and that its redshift implies that it is moving away from us at such and such a rate. Here are problems I have with some issues:
It is all very well to say that some particular galaxy is some particular distance from us but, isn’t it the case that our current perception/observation of its distance is actually not current at all? As in the light we now see was emitted a very long time ago (according to our up-to-date clocks)? So how current are such observations?
Another problem I can’t fathom is why, when we look back in time (i.e. at increasing “distances”) why does the universe not appear to get hotter as we approach the visible horizon? After all we are told that at some point it was extremely hot. I know about the opacity argument but as we approach that point should we not being seeing a much higher temperature than that in our locality?
On what grounds can one argue that the expansion rate is increasing? It would seem to me that if this is based on observing objects at ever greater distances that we are kidding ourselves because we are not looking at all at the present situation but at a situation which is receding into the past, the further out we look. To me, the place to look for the actual expansion rate is in our locality as this is the most up-to-date we can get in observing anything.
I would welcome any enlightenment.

By: Ghost72

Ghost72 — Sat, 28 Apr 2012 10:23:10 +0000

I had an idea that since the universe is expanding, time would be relational to the point in space relative to another point in space. In other words; if I didn’t move, my location in space in an hour would be completely different than it once was. ( the earth was rotating, the earth was revolving around the sun, the sun was revolving in our solar system, the universe was expanding)

Then I read this article and thought … oh never-mind.

By: mannon

mannon — Mon, 02 Apr 2012 19:42:48 +0000

@booboo There is a lot of gas and dust in our galaxy, but not that much between galaxies (with exceptions). So there are several reasons why this would not explain red shift. First of all simply absorbing some radiation would dim the light from distant galaxies, but it would not cause a red shift. We determine the red or blue shift independently of luminosity by looking for the tell tale absorption and emission lines of known elements in the spectra of visible objects. Basically there are patterns and we know where on the spectrum these patterns should be so when they are too to one direction or the other we know that the light has been shifted.

On top of that even if hydrogen gas caused a red shift nearly all the gas between us and distant galaxies is contained within our own galaxy, with a whole lot of nothing between us and most other galaxies we can observe. Our galaxy is obviously not spherical, but we know the shape of our galaxy and the approximate distribution of gas and dust within it, and the red shift does not obey that shape. Instead more distant galaxies tend to show a higher red shift. This implies that the distance it-self is the important factor and not what part of our galaxy the light came through.

@telson It’s really not all that mysterious, especially for Andromeda. Just because the Universe is expanding that does not mean that all of the galaxies within it are static like the points on the balloon. That’s merely a thought experiment to help visualize expansion. We know very well that galaxies are not static as in-fact pretty much nothing in the Universe is static. Everything is moving. Everything has some intrinsic velocity and is being nudged and pulled in various directions by gravity. Galaxies clump together and even collide. All of these motions impart their own red and blue shifts. The importance of expansion is that it adds an additional red shift on top of all these other shifts, and that shift grows over distance while all the other shifts do not. That means for relatively close galaxies we observe quite a bit of “noise” in the shifts from all of the galaxies moving through space under their own momentum and the gravitational influences upon them. But at extreme distances those shifts are minuscule, even negligible, compared to the red shift from expansion. In fact beyond certain distances there are no blue shifts at all… anywhere, because expansion red shift drowns them all out. So at cosmic distances the expansion of space dwarfs the movement through space and this is consistent with our observations.

By: ajollynerd

ajollynerd — Mon, 02 Apr 2012 17:04:25 +0000

@Tom Marking: Interestingly, if you average each of the methods, then average all of those results, you end up w/ 13.7 Gyr. (not sure if that’s how the 13.7 number was reached originally, but it is interesting nonetheless; at least, I find it interesting)

By: Stephen

Stephen — Mon, 02 Apr 2012 16:42:04 +0000

A few years ago, there was an interesting article that showed how one could observe eclipsing binary stars in other galaxies to determine distance geometrically. It went something like this: 1) watch for orbit, 2) figure out the orbit size, 3) measure max separation angle), 4) do the math for the distance. However, i’ve not heard of any followup. Does anyone use this method? Is there some problem with it?

By: swanand

swanand — Thu, 29 Mar 2012 16:33:53 +0000

the universe is expanding because there may be energy expanding space because after big bang so many other things were formed like galaxies planets etc big bang happened from a single particle and there may be some energy which is leading to expansion of space…..

By: booboo

booboo — Mon, 12 Dec 2011 02:23:50 +0000

All this expansion stuff is a hoax !! There was no BB !! The red shift does not indicate an expanding universe because between the earth and all the rest there is hydrogen gas which absorbs some of the radiation, hence lowering the frequency !! google for no big bang. Astronimers are only seeking job security and funding for bigger toys. All this knowledge will never benefit humanity for the next zillion years. Ban cosmology now !!!!!

By: Nick

Nick — Wed, 23 Nov 2011 17:46:56 +0000

So is it possible that the universe has such a large time frame that we are still in the process of the initial acceleration of the big bang?