Does this perigee make my Moon look fat?

By Phil Plait | August 26, 2010 7:02 am


I’ve been posting a lot of extreme close-ups of the Moon, but sometimes you can learn something by taking a step back.

For example, I imagine if I went out in the street and asked people what shape the Moon’s orbit was, they’d say it was a circle (or, given recent poll results, they’d say it was Muslim). In fact, however, the Moon’s orbit is decidedly elliptical. When it’s closest to Earth — the point called perigee — it’s roughly 360,000 kilometers (223,000 miles) away*, and when it’s at its farthest point — apogee — it’s at a distance of about 405,000 km (251,000 miles).

That’s a difference of about 10% — not enough to tell by eye, but certainly enough to see in a picture… like this one, by the Greek amateur astronomer Anthony Ayiomamitis:

lunar-apogee-perigee-2010

[Click to emperigeenate.]

Amazing, isn’t it? The Moon is noticeably different! He took those images at full Moon, but seven months apart, when the Moon was at perigee (last January) and apogee (just a few days ago as I write this). It’s part of a project he does every year, and it’s pretty cool. He was able to get these images within a few moments of the exact times of apogee and perigee.

You might wonder how the Moon can be at apogee when it’s full one time, and perigee at another time it’s full. That’s a good question, and it’s because the phase of the Moon doesn’t depend on the shape of its orbit, it depends on the angle between the Sun, the Moon, and the Earth.

If the Sun is behind the Moon from our viewpoint, we see only the dark side, and the Moon is new. If the Sun is behind us, and shining straight down on the Moon, we see it as full. The crescent and gibbous phases happen in between those times. So while the Moon’s phase depends on where it is in its orbit relative to the Sun and Earth, the orbit shape — the fact that it’s a bit of an ellipse and not a circle — isn’t all that important.

Not only that, the time it takes to go from full Moon to full Moon (called the synodic month) is not the same amount of time it takes to go from perigee, around the Earth, and back to perigee (called the anomalistic month). The first is about 29.5 days, the second about 27.6 days. That difference means that every time the Moon gets to perigee, it takes an extra 2.2 days or so for the phase to catch up.

Or, a better way to think about it is like this: say at some date the Moon is both full and at perigee. 29.5 days later, it’s full again, but it’s had an extra 2.2 days around the Earth. It’s a little bit past perigee when it’s full (or you could say it hit perigee before it was full again). Wait until the next full Moon and now it’s 4.4 days past perigee (or, it was at perigee again 4.4 days before it was full a third time). Keep doing that; after about 6 cycles of its phases, that extra time will add up to about half of the anomalistic cycle.

In other words, full Moon will happen at apogee!

It’s not an exact match, so you don’t really get a perfect full Moon at perigee and another at apogee in one year. But as Anthony showed, you can get pretty close.

And if you’re wondering why you’ve never noticed the 10% difference in Moon size, it’s because when you look at it, you’re not comparing it side-by-side with itself like in the picture. You don’t have a good gauge of exactly how big it is from month to month, so you never notice. You need to photograph it, or observe it very carefully through a telescope.

I’ll note that the Earth’s orbit around the Sun is also an ellipse, so the Sun appears bigger and smaller throughout the year; the change isn’t as big as for the Moon, but you can see for yourself because Anthony has images of that as well.

And if you’re curious about on what dates the Moon reaches perigee and apogee, head over to Fourmilab’s Perigee and Apogee calculator.

Amazing, isn’t it, that something that seems this obvious can be hidden in plain view. It makes you wonder what else you’re missing, doesn’t it?



* That distance is measured between the center of the Earth and the center of the Moon. Subtract the radii of each [(1737 + 6360) ≈ 8100 km (5020 miles)] to get the rough distance between the surfaces of the two objects.

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (57)

  1. alfaniner

    I heard it’s going to be as big as Mars in the sky next month…

  2. I imagine if I went out in the street and asked people what shape the Moon’s orbit was, they’d say it was a circle (or, given recent poll results, they’d say it was Muslim).

    I’d say the Moon is American & Western – thanks to the bravery and engineering know how involved with the Apollo space program back in the visionary age of US space exploration under JFK when the Free Democratic World beat the evil empire of Communist ideology – winning the space race & setting footsteps in the lunar regolith :

    “..in peace for all Mankind.”

    NASA hasn’t yet handed over the Moon to the Muslims as Islamic only territory – although with President Obama in charge… :-(

  3. Allen

    Very cool comparison of the moon at apogee and perigee, the difference is a lot bigger than I would have expected, but I guess this explains why a solar eclipse can be total or annular.

  4. @alfaniner

    I heard Mars was going to be as big as the moon on Aug. 27th. Sent Phil an e-mail about it. Apparently, the new incarnation of that canard is accompanied with a picture of two of Saturn’s moons from Cassini.

  5. Donnie B.

    These pictures also show another easy-to-miss feature of our Moon — namely, its libration.

    Look at the position of Tycho (the bright-rayed crater below the equator) and you can see that the Moon doesn’t keep exactly the same face to us all the time.

  6. rob

    i heard due to budget concerns, they are gonna demote mars from a planet to a moon and outsource it to jupiter. no word on the fate of phobos or deimos. rumors are they will just stick them back in the asteroid belt.

  7. IVAN3MAN_AT_LARGE

    Donnie B. (#4):

    These pictures also show another easy-to-miss feature of our Moon — namely, its libration.

    For those of you who don’t know what the bloody hell he’s talking about, see: APOD — Lunation.

    (I, of course, knew that; that’s how I knew where to find that link!)
    :cool:

  8. Messier Tidy Upper

    @ ^ rob : LOL. Don’t go giving the IAU any ideas now! ;-)

    @4. Donnie B. : Well spotted – nice observation, good comment. :-)

    @3. Todd W. : Which 2 of Saturn’s Moons?

    Every time I hear about our Moon now I can’t help wondering who is going to land on it next, when and whether they’ll be as relatively benevolent and generous about as as the USA has been. I always assumed growing up that America would land there again – to stay – in my lifetime. But now .. :-(

  9. TheMetalChick

    Messier Tidy Upper essentially Says: “The Moon Belongs to America”
    (It’s a Simpsons quote, I suggest you check it out.)

  10. Messier Tidy Upper

    @ ^ Todd W. : Thanks. :-)

    @9. TheMetalChick : Well they did get there first! ;-)

    @7. IVAN3MAN_AT_LARGE : Great video – but false advertising – it’s not a picture but a movie! Not that I mind. ;-)

    ***

    PS. Does anyone recall the name and/or author of a dystopian SF short story I vaguely remember reading many years ago about the USA abandoning spaceflight and surrendering the Moon and planets and thus having their global future wrecked with the winning nation – either Russia or China – left tyrannically ruling the world and oppressing the West? Sure would suck if *that* tale was coming true, eh? :-(

  11. MaDeR

    @TheMetalChick : It is not really suprising. He seems to be very much detached from reality and chock-full of propaganda.

    @Messier Tidy Upper:
    “free Democratic World”
    Last I heard, certain Korea called itself democratic. Words means nothing, doing things are everything. And in last 10 years, this does not look good for USA.

    “beat the evil empire of Communist ideology”
    Lesser evil beat greater evil. Proud much? You talk exactly like commie (when they were still at it, before fall), only in reverse.

    No, your country is not democratic nor free. It is duopoly: two big parties divided power between them and mercilessly execute any possible comeptition (thrid party have so high barriers to entry, not to mention legal and not-so legal persecution). And do not even get start me at your wars, especially Iraq fiasco based on killer lies.

    Only your freedom of speech, still taken seriously in some part of USA, saved you from being autocratic fundistan, like some christian version of Iran, only with more nukes. At least for now.

  12. MT-LA

    @MTU: You’ve been throwing out that troll bait for 3 posts now. Is it about time to put away that fishing poll? Or are you still trying to nab a whopper for your mantle?
    (by the time this posts, it might not even be relevant since I’m sure someone will indulge MTU…but it’s still annoying)

  13. Nemesis

    Besides the obvious issue of size, I thought Phil was referring to its libration when he stated “The Moon is noticeably different!”. Hopefully, everyone noticed that.

  14. IVAN3MAN_AT_LARGE

    Messier Tidy Upper (#11):

    Great video – but false advertising – it’s not a picture but a movie!

    From Dictionary.com:

    movie

    —noun 1. motion picture.
    […]


    :cool:

  15. parclair

    A friend and I have had a long disagreement regarding the moon. (I’ve tried to research this, but my math isn’t up to par).

    I say that the moon always arises and sets from the same points in the east and west. She claims that it moves like the sun does from north to south and back again.

    My reasoning is that the moon always presents the same exact face to the earth, which would indicate no tilt, therefore no north south movement. But, as I said, I can’t understand the math…..

    Please help? It’s driving me nuts.

  16. Fry

    I think I read about this after my son studied some astronomy in his kindergarten class. He learned that the moon ‘wobbled’. So of course, when he asked me, I Googled it.

    http://dumbscientist.com/archives/the-moon-wobbles has a great animation of this phenomenon. Great, though somewhat trippy when it’s not what you’re expecting.

    Then again, my son also told me about Mercury occasionally having a double sunrise. Seeing that in person would be even crazier/cooler.

  17. jick

    Well, I don’t find the Moon-is-American argument any more convincing than the Moon-is-Muslim one, but the spirit of sending a handful of people into a few selected spots in a spherical surface larger than Africa, and then claiming that the whole goddamn thing belongs to a political entity, does sound very “American Western” to me.

    * I do have very high respect for those who actually got there and others who made it possible.

  18. Messier Tidy Upper

    When it comes to the linked article there I think that while Obama may not be a secret Muslim he is certainly, undeniably the most pro-Muslim president in the USA’s history.

    Which, given the West is currently involved in the global war against Jihadist Islamic terrorism that was started by Osama bin laden on the 11th of September 2001, could be seen as something of a serious concern.

    It should also be noted that Obama being African-Amercian is a common misunderstanding – Obama is actually biracial half European American and half Kenyan-Indonesian-American. I wonder if perhaps the constitution will be changed after the Obama presidency to bar those who weren’t raised in America to parents of fully American background and origin from being presidential candidates. I cannot forgive Obama’s betrayal of America -especially regarding its space program. I wonder how many others feel the same?

    As for the Court Judges versus the Disney dwarfs *that* at least could be explained positively by the fact (I’d reckon!) of more people coming into contact with and having personal experience of the Disney dwarfs than the US Supreme Court! ;-)

    The geography and astronomy ignorance is just dumb-founding though. I hope alot of it is peopel deliberatley giving joke answers to what are dumb questions -like answering 5 to the question of “how many 2 + 2 equals. :-(

  19. John Moore

    Phil, I have been wondering for some time now about the increase in distance of the moon from the Earth. I know it moves about an inch or so a year. My question is how much affect has this had on tides over the years, decades, centuries? It would seem that tides would have diminished over the years. Any input would be appreciated.

  20. Messier Tidy Upper

    @13. MT-LA : I’m expressing my views and feelings just as you are. I’ll defend your freedom to do so – so, I reckon, you should be willing to defend mine too.

    I do think these are serious questions which deserve proper discussion & I’ll admit these are things I feel very strongly about. Is that really such a crime or to be considered “trolling” or annoying? :-(

    @12. MaDeR :

    He [ie. me] seems to be very much detached from reality and chock-full of propaganda.

    Same back at you. :-P

    What precisely have I said that you *think* is inaccurate or “propaganda” as opposed to reality?

    I’m calling you out on your nasty ad hominem attack on me there.
    Note that the fact that I disagree with you does NOT make me deluded or a propagandist as you seem to think. I’m being polite to you and expect the same courtesy in return.

    Last I heard, certain Korea called itself democratic.

    1. Which Korea – I presume you mean the Northen one? Technically, I believe it is called The Democratic People’s Republic of Korea (in Korean natch!) while in fact being none of those things.

    2. Last I heard the United States of America called itself a Republic! Does that mean it must always be run by Republicans? ;-)

    (Historical note : Nations often aren’t what they seem to sound like they are. Famous example – the Holy Roman Empire was neither Holy nor Roman nor an empire. Another example – India was named after the Indus river which is now in .. Pakistan. Thinking of which, Pakistan literally means “land of the pure” which given its dubious govt and levels of corruption, double dealing over terrorism & the Taliban, lack of sanitation, etc .. just has to be a misnomer! ;-) )

    3. So you are comparing the United States of America with its political system of representative democracy, a free media and frequent elections to the Communist totalitarian one-party cult dictatorship of NorthKorea?!? What the ..?! Really? Seriously?

    No, your country is not democratic nor free.

    My country is actually Australia, mate. We’ve just had an election and still don’t know who’s running the govt after a hung parliament result. ;-)

    do not even get start me at your wars, especially Iraq fiasco based on killer lies.

    Gee, and you accuse *me* of being a “troll” and a “propagandist!?” The Iraq war was – in hindsight – a mistake but it sure wasn’t that simple.

    It was a complicated situation caused by a number of things but at the time everybody expected that Saddam did have WMDs, he was keen to aquire them and did pose a regional risk and he was an nasty dictator who was supporting terrorism – for instance, paying the families of Palestinian homicide-suicide bombers – & brutally oppressing his own people. Oh & recall how he used poison gas against the Kurds?

    Whole other discussion there – but it is not as straightforward as you make it sound. I don’t think Bush-Cheney were great leaders but evil as you consider them do you really think the go to war just for the fun of it without good reason like pantomine villains??

    ***

    PS. Now taking my dog out for a late night /early morn walk then going to bed.

  21. MaDeR

    This was reaction to earlier comment to someone else.
    @MTU: now I know that you are simply troll. Blablering nonsense in answer to something unrelated is good indication.

    PS: did you know that Obama’s grandma was Armenian, and he himself is in fact Jude?

    Now, to the gist.
    “My country is actually Australia, mate.”
    Oh dear. You sure spoke like some rightwing nut. Sorry for mistake – it is hard to see difference.

    “Last I heard the United States of America called itself a Republic!”
    You claimed it is free and democratic. I consider USA neither. I already told about duopoly and you ignored this.

    “So you are comparing the United States of America with its political system of representative democracy, a free media and frequent elections to the Communist totalitarian one-party cult dictatorship of NorthKorea?!?”
    No, I am comparing propaganda techniques. Do you claim that democratic goverment cannot possible lie or practice propaganda?

    “The Iraq war was in retrospect a mistake but it sure wasn’t that simple.”
    Do you deny that official reason to start this war was based on complete lie? And I claim this was known already by deciders.

    “you consider them do you really think the go to war just for the fun of it without good reason like pantomine villains”
    No, not for fun, but for reasons that have nothing to do with anything what I would consider “good reason”.

  22. Patrick

    @todd w.

    I work at a company that manufactures consumer scopes. For as long as I have worked here we have gotten emails and calls about that. They usually get passed over to me to explain as I am one of the few people here who actually understands the background of the hoax, and can explain to them rationally that it is impossible.

    However at the end of August we still get people calling up angry because they bought a telescope, and then there was no giant Mars. Thank god I am not in customer service.

    Sigh.

  23. MT-LA

    MTU: Perhaps I should have made my point a little bit more clear, and perhaps troll is the wrong word, though annoying is still pretty accurate.

    See, what annoys me is that this is an astronomy blog, and this article is talking about the moon. You jump up and start complaining about the policies of a country of which you are not a citizen, and you vent about the religious leanings of a head-of-state which is not your own head-of-state.

    Then, when no one responds to your mini-rant, you try again, casting out the bait, this time hiding it behind a series of congratulatory platitudes to other posters, and a healthy dose of smiley-faces to make sure that no one actually thinks you have a bad attitude.

    Acch…still no success. The desperation drives you to post yet a third time, your insinuations now contained in a PS statement, affirming that your point probably has nothing to do with the thread of the discussion – but hey, you want to be heard and noticed, so you’ll say it anyways.

    Finally, someone inevitably takes the bait. You go full bore into a Socratic defense of your views, finishing nearly every sentence of your post with a question mark (though its obvious some of those weren’t actually questions). Then, to fully complete the circle of (I dont even have an adjective for this), you announce to all that you will not even bother checking the responses to your many and varied questions.

    Yes, I know that occasionally Phil posts about things other than astronomy/skepticism/bad-assness. But this is his forum. You are clearly looking for a forum to discuss your political views. Why inject them, artificially, into this discussion when there are plenty of other websites that would gladly run with your discussion? Why subject us to it? (again, and again, and…)

  24. Brandy

    But the important question is…Can we turn the man in the moon into a rabbit?? :-)

    Filigree apogee pedigree perigee

  25. llewelly

    parclair, August 26th, 2010 at 9:29 am :

    I say that the moon always arises and sets from the same points in the east and west. She claims that it moves like the sun does from north to south and back again.

    The movement of the points from which the Sun rises and sets occurs because the orbit of the Earth around the Sun is not aligned with the orientation of the Earth’s axis of rotation. The orbit of the Moon around the Earth is also not aligned with the Earth’s axis of rotation, and therefor the points at which the Moon rises and sets also move north and south on the horizon.

  26. llewelly

    Messier Tidy Upper : August 26th, 2010 at 9:35 am :

    It should also be noted that Obama being African-Amercian is a common misunderstanding – Obama is actually biracial half European American and half Kenyan-Indonesian-American.

    Indonesia is one of the places he grew up in, not part of his race.

  27. MaDeR

    @llewelly: Bah, who cares about little details, we know that Obama have suscipious ancestry, as MTU proved. We all agreed that he is Jude and of Armenian ancestry already. If this does not disqualify him, I do not know what would! Hmm, lets see what else. Lying about oral sex? Sure, this is horrible, horrible thing, as anything involving sex anyway. This is shifty and lefty. Lying about WMD and causing war that killed already tens of thousands people? No, this is alright, or even far right. The more bodies, the better.

  28. parclair

    @llewelly Thank you for the explanation. I owe my friend a bottle of wine, drat. ;-)

  29. jfb

    @MTU:

    It should also be noted that Obama being African-Amercian is a common misunderstanding – Obama is actually biracial half European American and half Kenyan-Indonesian-American

    Kenya was part of Africa, last I checked. Secondly, BHO Sr. was not part Indonesian; both of his parents were Kenyan. When BHO Jr.’s mother married Soetero after divorcing BHO Sr., BHO Jr. didn’t magically become part Indonesian.

    Unless you’re claiming BHO Jr.’s mother was half-Indonesian, in which case … no.

    And yeah, it’s a sad fact that for most Americans, if you ain’t all white, you ain’t any white. We’re working on it.

    When it comes to the linked article there I think that while Obama may not be a secret Muslim he is certainly, undeniably the most pro-Muslim president in the USA’s history.

    Meaning, he’s not out to blow them off the face of the Earth just on general principle. Realize that we’re grading on a curve, here.

  30. Chris Winter

    Donnie B wrote: “These pictures also show another easy-to-miss feature of our Moon — namely, its libration.

    Look at the position of Tycho (the bright-rayed crater below the equator) and you can see that the Moon doesn’t keep exactly the same face to us all the time.”

    I knew that, but I’m still surprised at the amount of libration those pictures show. Just eyeballing it, it looks to be close to 30°.

  31. These are also important words to remember if you hope to achieve substitutiary locomotion. Bed knobs and broomsticks . . . anyone. . . ?

  32. DrFlimmer

    Why is here a debate about Obama going on, again, when the thread was about a rising moon?

    Wait. A rising moon? He’s getting bigger? NOOO, HE’S COMING FOR US! HE WILL DESTROY THE EARTH! RUUUUUNNNNNN!!!!!!!!!!!!!!!!!!

    Maybe I should work a little bit on my “conspiracy” skills ;)

  33. IVAN3MAN_AT_LARGE

    Damn it, after all those irrelevant comments above, I’ve forgotten what I came here for!

    Oh, yeah, now I remember…

    @John Moore (#20):

    … I have been wondering for some time now about the increase in distance of the moon from the Earth. I know it moves about an inch or so a year. My question is how much affect has this had on tides over the years, decades, centuries?

    You will find a good explanation (without blinding you with some serious mathematics!) here:
    The Recession of the Moon.

  34. Ross

    I understand the Moon’s orbit is tilted with respect to the Earth-Sun ecliptic. How does the tilt progress as the Earth and Moon orbit the Sun? Does it remain fixed with respect to the stellar background (like the Earth’s axis always pointing at Polaris), or does it rotate with the Earth’s orbit around the Sun?

  35. Mark Hansen

    parclair, the best way of determining whether the moon does indeed rise and set at different points or the same one would be to verify it yourself. Unfortunately llewelly does give the game away with a scientific explanation but even so, try some observations and see if it is right. Here’s a link to one someone prepared earlier. apod.nasa.gov/apod/ap050713.html

    Rest of the world, we’re not all like MTU here. Really, we’re not!

  36. Babak

    Alternately, the area (rather than the diameter) of the perigee moon is over 30% larger than the moon at apogee, making it visibly larger in the sky.

  37. t-storm

    I love orbital mechanics.

    Question about the moon and life. If we didn’t have the moon how different would life be? No tides come to mind. Would the planet be a giant stagnant cess pool?
    Oh, no werewolves would be cool.
    Andy Williams wouldn’t have anything for the third encore.
    Dropping my pants and showing my bare ass would be just that.
    Aqua Teen Hunger Force would be lacking some awesome characters.
    Neil Armstrong would just be a professor at UC.
    People acting crazy would just be doing so because they are.
    Frank Zappa wouldn’t know what to name his kid.
    Luna moths would just be big ass green moths.

    I can go on for days, 86,164 seconds at a time.

  38. Donnie B.

    There would still be tides without the Moon. Solar tides have about half the magnitude of the lunar contribution, so solar-only tides would be much smaller and more regular (since you wouldn’t have the effect of the solar and lunar tides canceling or reinforcing one another).

  39. Chip

    Those of us ham radio types who communicate by bouncing radio signals off the moon know all about this. The return signals from the moon are right at the level of “almost undetectable”. That 10 percent difference in the moon’s orbit often makes the difference between successful contact and no contact. Granted, there are other factors at work as well, but during moon apogee it’s usually best to use other modes of communication.

  40. Stubby

    Question. With the moon ‘growing and shrinking’ by 10% how does that effect solar eclipses ? Do eclipses always happen when the moon is at the same point in its orbit?

  41. Chris Winter

    According to Ward & Brownlee’s Rare Earth, a large moon is necessary to stabilize its primary’s obliquity, else the planet’s axis will wobble too much and surface temperatures will change too much for complex life to develop.

    See e.g. http://www.chris-winter.com/Erudition/Reviews/Ward_Brownlee/Habitatable.html

    Hmmm… Thanks to Kepler, I may have to revise some of that.

  42. Trebuchet

    #41 Stubby: No, eclipses always happen at a new moon but not necessarily at the same point of the orbit. When the moon is at apogee (smallest) we get annular eclipses, where the moon doesn’t quite cover all of the sun.

  43. Grand Lunar

    Very cool, Phil!

    I wondered just how much of a size difference there was.
    Now we can see it plainly!

    It’s good that there are those out there that share their enthusiasm of astronomy in such ways.

    @ 2. Messier Tidy,
    Sorry, but your closing statement in that post isn’t very smart.

  44. MaDeR

    @Chris Winter:
    “According to Ward & Brownlee’s Rare Earth, a large moon is necessary to stabilize its primary’s obliquity, else the planet’s axis will wobble too much and surface temperatures will change too much for complex life to develop”
    Define “too much”. Undoubtedly, sufficiently high variation would make life too hard, but do they proved that lack of Moon would did such excessive, life-preventing variation?

    Also, some comments about this page:
    “Not be in an elliptical galaxy/globular cluster” – while this is true, that these object contain older stars, what it have to do with “containing the amounts of heavy elements”? If anything, there should be more heavy material after bilion years of producing it in stars. While in such galaxies new stars are forming at slower rate, they should have plenty heavy elements.

    “Be in a single-sun solar system.” Not so fast. We already know about planets in such systems. So much for “negation of long-term stability”.

    “then they would be tidally locked to the star, and life probably could not develop under that condition.”
    They have no basis whatsoever for this claim. Tidal lock does not prevent developing life in twilight zone, and if planet have sufficiently dense atmosphere, temperature differences will equalize, giving microbes whole planet back. I consider this claim biggest single BS of their book.

    “Have a giant planet in the system to act as an “asteroid sink”.” There was many articles that give doubt to this, claiming that Jupiter can also drawn asteroids closer without being hit by them, negating at least part of protecting role, if not making it more dangerous.

    “Not have the giant planet too close, or in a highly elliptical orbit.” I read articles that claim doom of rocky planets is not certain in this scenario. Anyway, we will know soon (few year), if there is really anything to it.

    By the way, some argument are repeating (quantity over quality, eh?). For example, “Have radioisotopes to keep core molten, drive magnetic field, make volcanoes & plate tectonics” is directly linked to “sufficient size/mass of planet” and “holding water”.

    “Hypothetically, animal life will not develop without such “snowball” events.”
    First time I heard about that. Anyway, this does not prevent microbial life.

  45. JerryP

    “There is no dark side of the moon, really…In fact it’s all dark” – Roger Waters

    Has nothing to do with any of these comments, but I did start humming Eclipse while reading the OP.

    On another side note, I’ve received (and debunked) 5 of those “Mars as big as the moon” memes since June, already. Why anyone would perpetuate such stupidity, or revel in its proliferation is beyond understanding.

  46. mikekoz68

    We should really send a man up there to see what’s going on, can’t believe its 2010 and we still have never gone to the moon.

  47. Chris Winter

    MaDeR:

    Thanks for your comments in #45. I won’t try to address them here; I’ll just make some changes in the table. As you noted, it is intended to reflect what’s in that particular book.

    I’ve generally been quite critical of books by Ward & Brownlee. I really liked Ward’s Under a Green Sky, however, and am now reading his new one, The Flooded Earth.

  48. Brent

    Actually the moon’s orbit is not quite elliptical but more like a rounded off 13-sided polygon.

  49. My favorite size-of-the-moon story sounds even sillier than the Giant Mars story, but is actually true. Everybody has noticed how big the full moon seems to be when it first rises, and how by midnight it looks much smaller when it is high in the sky. Probably everybody knows it is really the same apparent size at both times, as you can prove to yourself by comparing it to a finger on an outstretched arm. So the changing-size effect is purely psychological. What is not so widely known is how to remove the psychologcial effect. Just stand up, turn your back to the moon, spread your legs, and bend down and look through your legs (head upside down) at the moon. Don’t ask me why, but this pretty much kills the illusion of large size. Try it at home (preferably when no one else is around).
    Lou

  50. Messier Tidy Upper

    Did I mention I liked the image? I did ;-)

    Its just that whenever I hear anything about the Moon now I can’t help but think :

    “Durnnit,we should be going there already! Thanks Obama – NOT!”

    Then I start feeling steamed up. Its a hot button issue with me. I don’t mean to spoil things for people here but .. sheesh. Can’t I voice my opinion?

    I think it *is* important for our futures – not just for Americans but Westerners more widely and the rest of Humanity in general & I do strongly feel that Obama has betrayed the human space program and science and our collective futures with it. I hate him for that. Really hate him. :-(

    Also note that the Bad Astronomer also referred to politics and raised the issue of Obama’s background & religious beliefs in the opening article – or was I the only one to actually click the link in that post? :roll:

    @44. Grand Lunar :

    @ 2. Messier Tidy, Sorry, but your closing statement in that post isn’t very smart.

    Yeah, maybe not in retrospect.

    @24. MT-LA Says:

    Then, to fully complete the circle of (I dont even have an adjective for this), you announce to all that you will not even bother checking the responses to your many and varied questions.

    Not true. Saying I’m going to go for a walk and then sleep isn’t at all the same as saying I’m not going to check or reply later. Don’t you have to sleep sometimes too? I’m in a (very) different timezone & was just letting people know that if they didn’t already. Okay?

    Naturally, I don’t agree with the rest of your assessment of my conduct on this thread either.

  51. Messier Tidy Upper

    Arrgh. Since we’re already talking about this here, I do feel I need to respond to some of the comments others have made :

    @ 30. jfb Says:

    @MTU: “It should also be noted that Obama being African-American is a common misunderstanding – Obama is actually biracial half European American and half Kenyan-Indonesian-American.”
    Kenya was part of Africa, last I checked. Secondly, BHO Sr. was not part Indonesian; both of his parents were Kenyan.”

    The fact that Obama was raised in Indonesia means the nurture / socio-cultural environment part of Obama’s nature /nurture equation was Indonesian. Indonesia is the world’s largest Muslim nation and is a hotbed of terrorism with such things as the Bali bombings which killed many Aussies among other Westerners and the headquarters of the Jemaah Islamiya terrorist group among others. Given Obama lived many of his formative years there it does raise certain legitimate questions over his cultural and political identity and where his sympathies lie.

    Plus “African-American” isn’t necessarily the same as recently coming from Africa to America. There’s an African-American community that has been generations in the USA with a culture and history of its own and then there’s Kenyan-Americans which are Americans from a recent Kenyan migrant background. “African-American” refers to those of real previous generations of African-slave-originating-American background – which Obama isn’t. Politically Correctness really does make it hard to communicate plainly sometimes.

    [Pro-Muslim] Meaning, he’s [Obama’s] not out to blow them off the face of the Earth just on general principle.

    Aaand ‘blowing Muslims off the face of the Earth on general principle’ is a bad thing because..?? ;-)

    Okay, not really. But the thing is that all too many Muslims (not *all* I know, but more than enough) want to blow *the West* off the face of the Earth – and are actively trying to do so. Westerners then cannot fairly be blamed for responding in self-defence or viewing Muslims negatively as a result of, y’know, such Islamic terrorism & rhetoric.

    Besides Obama goes wa-ay further on the pro-Muslim side ledger than you suggest to the point of activly favouring Islam over the Western (incl. Israeli) interests – in my view anyhow.

    @27. llewelly Says:

    Indonesia is one of the places he grew up in, not part of his race.

    I know that – I was referring to the fact that he was raised in Indonesia by a Kenyan Muslim father & an American-Amercian mother and thus his idenity is part Kenyan part Indonesian and part American. Obama is two thirds non-American in reality. Non-American Kenyan Muslim father, non-American Indonesian upbringing, partly American by descent on his mothers side only – and she was atypical enough to be non-American in choice of her life partner and living overseas for a considerable time. You can call Obama many things but “all-American” is certainly NOT one of them.

    @22. MaDeR Says:

    did you know that Obama’s grandma was Armenian, and he himself is in fact Jude?

    Obama is very clearly NOT Jewish. Claiming that is far more absurd and unfounded by any reasonable evidence than suspecting based on his evident pro-Islamic bias that he’s secretly Muslim or knowing he used to belong to Jeremiah Wright’s radical anti-American “Christian” group.

    You claimed it is free and democratic. I consider USA neither. I already told about duopoly and you ignored this.

    Well *I* consider the USA both free and democratic.

    To support this I’ll note the United States has elections, has a free press & a constitution & Bill of Rights full of checks & balances and so forth. Americans – and Westerners also value freedom and human rights in a way much of the rest of the world – notably Communist China and the Islamic totalitarian theocracies just don’t.

    Life, liberty and the pursuit of happiness.

    We are so lucky to be born in nations that take that for granted.
    That take elections and freedom of expression for granted.
    Isn’t it time we stopped attacking & undermining our own culture and started standing up for it proudly against those who would take those freedoms and rights away and replace them with nastier less free, less ideal ways?

    As for duopoly – that’s just not so. Do the names Ralph Nader and Ross Perot mean anything to you?

    Do you claim that democratic goverment cannot possible lie or practice propaganda?

    Well *all* governments try to spin things and use proganda in their favour -but the extent and the checks & balances & the ways of detecting and countering this are vastly different – especially comparing this between USA Vs North Korea – for …heaven’s.. sake! :roll:

    “The Iraq war was in retrospect a mistake but it sure wasn’t that simple.” Do you deny that official reason to start this war was based on complete lie? And I claim this was known already by deciders.
    “you consider them do you really think the go to war just for the fun of it without good reason like pantomine villains” No, not for fun, but for reasons that have nothing to do with anything what I would consider “good reason”.

    Yes I do indeed deny that your ridiculous (if sadly all too common) allegation of “going to war for a lie” is true.

    I consider there were at least three good reasons why we invaded Iraq (& Australia sent troops there too along with the UK and others don’t forget) :

    1. Saddam was trying to aquire and suspected of developing WMDs which he had a record of using ruthlessly.

    2. Saddam was a regional threat to peace and stability and a state sponser of terrorism.

    3. Saddam was brutally oppressing and slaughtering his own people and there was the hope that removing his regime would create a positive example for other nasty Islamic nations in the vicinity.

    We now know Saddam probably didn’t actually have WMDs and was bluffing – but he had used them in the past and was seeking to aquire them in the future. The invasion prevented this from happening.

    We also know Saddam sponsered terrorism – eg. the Palestinians – & was athreta to our allies liek Arabia and Kuwait. Well we took care of that. Saddam’s regime no longer poses a threat to its neighbours. Some of the Iraqui insurgents still do – but they are mostly Iranian-aided and motivated and that’s another complex story again ..

    We freed the Iraqi people from Saddam. The rest of it hasn’t gone as planned – long story & yes, alot of political & military mistakes contributed there – but that’s still more the Iraqi peoples fault than ours IMHON.

    Lies? Nup, no lies. Some wishful over-optimistic thinking sure. Soem mistaken judegmenst probably but tomake Bush outas some war criminal for doing what he thought was the right thing basedonthe information he had at hand at the time is going too far. I’m no huge fan of Bush’es – but I’m also sensible enough not to make him into a melodrama villain caricature either.

    Clearly we’re not going to see eye-to-eye on such issues. But I hope I’ve given you some cause to think again and to understand why I think as I do.

  52. Dave

    MTU @51:

    “Can’t I voice my opinion?”

    Of course you can – but equally, everyone else can voice theirs. If your opinion is silly, well, others may have (and voice) an opinion on that… them’s the perils of you not living in your own monocracy.

  53. Dave

    MTU @52:

    “The fact that Obama was raised in Indonesia means the nurture / socio-cultural environment part of Obama’s nature /nurture equation was Indonesian. Indonesia is the world’s largest Muslim nation and is a hotbed of terrorism with such things as the Bali bombings which killed many Aussies among other Westerners and the headquarters of the Jemaah Islamiya terrorist group among others. Given Obama lived many of his formative years there it does raise certain legitimate questions over his cultural and political identity and where his sympathies lie. ”

    What sort of stand do you take against, for example, concert tours or sales of recorded music by the likes of Enya, The Corrs or Van Morrison? Never mind whether or not you like those people or their music: they’re from (and grew up in) Ireland, the home of the IRA and other terrorist groups which have killed a few thousand people over the years (including some Aussies) – by your argument, we should assume they’re likely to be implicit if not explicit accomplices in every death caused by an Irish terrorist shooting or bombing. Heck – given that many Americans supported the IRA financially – I should be justified in wanting to see that nation disappear from the planet entirely, and given CIA activity here and there over the years I’d rightly be joined by most of the people on the planet. Using (as I say) your argument, which I think (to put it politely) is specious.

    Isn’t it better to realise that nations as a whole are not reflections of a small number of their more insane inhabitants, and that individuals from a particular country are not always fully indoctrinated robots, automatically sinking to the worst level of that nation? A few nutjobs in Ireland or Indonesia do not make me think worse of those nations as a whole, just as I can read your posts and still think of Australians as a decent bunch of people I’d like to have a beer with.

  54. Messier Tidy Upper

    @54 Dave :

    Isn’t it better to realise that nations as a whole are not reflections of a small number of their more insane inhabitants, and that individuals from a particular country are not always fully indoctrinated robots, automatically sinking to the worst level of that nation?

    I know that – it’s not what I’m saying at all.

    A few nutjobs in Ireland or Indonesia do not make me think worse of those nations as a whole, just as I can read your posts and still think of Australians as a decent bunch of people I’d like to have a beer with.

    Well I’m happy to have a beer with you & I think I’m a decent person too.

    Discussing such issues face to face rather than over the net is probably better – I think you & others are really misunderstanding what I’m saying here.

    I’m not saying *all* Indonesians are bad but there are elements of Indonesian culture – & Muslim culture more broadly – which are very troubling and which are incompatible with Western civilisation & Western values.

    I think President Obama is overly infuenced by his background into overlooking the worse side of Islam and Islamic nations which is not good when we are at war with these people. I think the Western world needs to be led by someone who is unapologetically proud of Western ideals such as equality of everybody incl. women and gays, freedom of expression and all the other good things that have made the West what it is.

    The President of the United States is effectively the leader of the Western world – so I think it is reasonable to have misgivings over Obama seeming to identify with and support the culture and beliefs – some incredibly nasty – of our current enemies. Does that not make sense to y’all?

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »