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Episode of The Universe (WMAP)

  1. Jun 1, 2009 #1
    Episode of "The Universe" (WMAP)

    Hi everyone. Sorry if this is the wrong place to post this, but I have no idea exactly where to ask this.

    What was the name of the episode of "The Universe" where they talk about the WMAP and how the measurements are indicative of a flat universe. My friend wants to watch that, but I can't find it anywhere. Silly Question, I know. :biggrin:

    Thanks.
     
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  3. Jun 1, 2009 #2

    marcus

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    Re: Episode of "The Universe" (WMAP)

    I found a 9-part thing called Beyond the Big Bang, that apparently was run on the History Channel. I watched a little and it was about the Background Radiation.
    It was on YouTube, I think.
    Try this:


    I also found this, it is not a commercial program but it is pretty decent.
    Nobelist George Smoot talking about the Cosmic Background Radiation
    http://www.revver.com/video/832724/the-history-and-fate-of-the-universe-part-8-of-9/
     
    Last edited by a moderator: Sep 25, 2014
  4. Jun 1, 2009 #3
    Re: Episode of "The Universe" (WMAP)

    Thanks, but sadly, this isn't it. The episode I'm talking about is where they shot light beams off the WMAP and added up the angles to find out whether the universe was flat or not. The angles added up to 180 degrees, so they concluded it was flat.

    I watched the link and they don't talk about that, but thanks all the same.

    Does anyone know what episode it was?
     
  5. Jun 1, 2009 #4

    chroot

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    Re: Episode of "The Universe" (WMAP)

    Uh, what? WMAP is a very precise microwave antenna... it does not shoot any beams of light or measure any angles...

    - Warren
     
  6. Jun 1, 2009 #5
    Re: Episode of "The Universe" (WMAP)

    No, I mean the map itself. They did something where they took light beams and shot them off the map and added up the angles. I'm no expert on this. Anyway, my friend and I are curious to see it.
     
  7. Jun 1, 2009 #6

    marcus

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    Re: Episode of "The Universe" (WMAP)

    To me that sounds like an analog way of taking a Fourier transform. It could be a very clever way of getting the power spectrum of the CMB sky map.

    Was this program on the History Channel? Or was it Science Channel?
    Was it associated with any names that one could use as keyword for search?

    What I understood from your post was there is a History Channel series called Universe and this is somehow part of that. Personally I never watch commercial television so you have to say everything twice and very clearly.
     
  8. Jun 1, 2009 #7
    Re: Episode of "The Universe" (WMAP)

    It was the History Channel... yes, the show is called "The Universe"... and for keywords, I don't know what to tell you. That's just it, anything that you would associate with the WMAP I have already searched for, and nothing comes up. I looked through the episode logs, and none of the episodes seem to specialize on this. However, I am 100% sure that it was the Universe on History Channel. My guess is that what I am looking for was thrown into a random episode, maybe even one that is from the most recent season.
     
  9. Jun 1, 2009 #8
    Re: Episode of "The Universe" (WMAP)

    I believe that you are looking for an episode of The Universe from the History Channel entitled "Parallel Universes". It may be from Season 3 Episode 2 and apparently was first shown on 11/18/2008. Just go to history.com and search for the two-word term Parallel Universes. This episode is split into five video parts and should be on the far right side of your search screen.

    I found an article and subsequent discussion about this at the site below where they talk about the laser beams being bounced off-of the WMAP. Just search for the word beams and you should see some of these comments.

    http://asymptotia.com/2008/11/18/tales-from-the-industry-xxv-parallel-universes/

    I hope this helps.
     
  10. Jun 1, 2009 #9
    Re: Episode of "The Universe" (WMAP)

    Yep, it is in Part 1 (of the Five Parts) as I am now watching it as I type this.
     
  11. Jun 1, 2009 #10
    Re: Episode of "The Universe" (WMAP)


    You're right, that's it. Thanks a million. :smile:
     
  12. Jun 1, 2009 #11
    Re: Episode of "The Universe" (WMAP)

    I guess now, to go along with this, my next question is simply this. Is this a justifiable test? Does this "beam test" really tell us the truth? I have read some blogs about it and some obviously think it's 'ridiculous', but they never say why.
     
  13. Jun 2, 2009 #12

    Chalnoth

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    Re: Episode of "The Universe" (WMAP)

    Well, it's not actually true that WMAP alone shows us that the universe is very nearly flat. It turns out that it is possible to fit the WMAP data to a very non-flat universe. In order to say that the universe is flat with WMAP, we have to use nearby data. The CMB data that WMAP looks at, which is at a redshift of z=1090, when compared with nearby data at around z=1, gives us a huge lever arm with which to test the curvature of the universe.

    The most accurate way we do this today is by comparing the average size of fluctuations on the CMB with the typical separation between nearby galaxies. You see, these fluctuations in temperature on the CMB are the seeds of structure formation. While the relationship between these fluctuations and the separation between galaxies is not trivial, by comparing the size of these early temperature fluctuations with the much later distribution of structure in the universe, we get a very accurate measurement of the curvature.
     
  14. Jun 2, 2009 #13
    Re: Episode of "The Universe" (WMAP)

    Thanks.

    Also, (sorry, I have a lot of questions on this), I listened carefully to what they were saying in the video, and they specifically said "We shot laser beams to the farthest reaches of space". This makes no sense to me. If they shot beams to the farthest reaches of space, it would take quite a while for them to get back to us. What exactly do they mean by this, because there must be something I'm missing?
     
  15. Jun 2, 2009 #14

    Chalnoth

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    Re: Episode of "The Universe" (WMAP)

    Yeah, that makes no sense whatsoever. It was probably discussed as a hypothetical situation, not anything directly related to how the measurement was performed.

    The basic idea is that you can figure out if space is flat by building a triangle out of geodesics (the lines made by moving objects, which could include a laser beam). If you make such a triangle, and the interior angles add up to 180 degrees, then you live in flat space. If the angles are larger or smaller, then that indicates curvature.

    You can imagine, for example, drawing a triangle on the surface of a sphere: its angles will always add up to more than 180 degrees. For instance, for the extreme case where we build a triangle with one point at the north pole, and the other two points 90 degrees away from one another at the equator, then the angle at each vertex of the triangle will be 90 degrees: the angles add up to 270.

    Observing the CMB is the mathematical equivalent of "drawing" a triangle in laser beams across the universe. Of course, we're not actually firing lasers, just taking advantage of light rays that are already out there. And we need to compare multiple such experiments to make sure we understand the sources of these light rays. But hopefully this gives you an idea of why observing the "triangle" drawn out by the CMB is so helpful in constraining the curvature: because the CMB is so far away, it traces out a tremendously large triangle, which can be used to constrain the curvature very accurately.

    The triangle in question, by the way, is given by the average distance between the hot and cold spots on the sky (or something very like this that would take longer to explain...), as well as the lines between us and the CMB that make up the other two sides of the triangle. If we know the angle here at Earth (as given to us by WMAP), and the distance to the CMB (which is given to us by combining WMAP with nearby observations), we get an accurate picture of the dimensions of this triangle, which tells us that the universe is very, very flat.
     
  16. Jun 2, 2009 #15
    Re: Episode of "The Universe" (WMAP)

     
  17. Jun 2, 2009 #16

    Chalnoth

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    Re: Episode of "The Universe" (WMAP)

    It was probably an unfortunate confluence of the scientists attempting to explain what was going on and the editors who know that the public sees scientists who properly qualify their statements as using 'weasel words'.

    Well, I tried to explain it in the above post, but perhaps I'll try again.

    First, when we observe the CMB, we see a series of hot and cold spots. If we look at the average angular size of these hot and cold spots on the sky, we get a very specific angle (around 2 degrees). Since we are observing the universe at a very young era, this 2 degree separation represents a very large physical separation. We make use of other information, both from the CMB and other experiments, combine it with theories about how the early universe behaves, in order to get a handle on the true physical separation that this 2 degree angular separation represents.

    The basic idea is that in the very early universe, quantum fluctuations set up minuscule oscillations in the matter that was around at that time. As the expansion slowed down from inflation, these oscillations became sound waves that traveled through the plasma of the early universe, and they bunched up at what is known as the "sound horizon": the total distance a sound wave could travel since inflation ended. So the physical size of these fluctuations depends upon two things: the speed of sound in the fluid of the early universe, and how much time passed between inflation and the emission of the CMB. These two things, in turn, depend upon the contents of the universe (though fortunately for us, dark energy has little to no impact, so we only have to make use of the much more well-understood normal matter, radiation, and dark matter for these calculations).

    So, with just the CMB, then, we have a superb picture as to the angle, as viewed from Earth, of the average separation between these hot and cold spots. The CMB itself also provides us with a pretty accurate picture of the physical distance at the emission of the CMB. That's two parts: the nearby angle, and the length of the far side of the triangle. Not enough to say the universe is flat, but it's a start.

    Nearby experiments correlating the nearby properties of the universe with the CMB give us a third piece of information about this abstract triangle: the length of the sides of the triangle that stretch from us to the CMB. They also help to further constrain the contents of the universe, giving us an even clearer picture as to the length of the far side. Put all together, the dimensions of this abstract triangle tell us that the universe is very, very flat.
     
  18. Jun 2, 2009 #17
    Re: Episode of "The Universe" (WMAP)

    Unfortunately this issue seems quite common with pop-sci documentaries (especially when it comes to cosmology). It's a shame, but I think alot of these shows that are supposed to educate are actually responsible for the spread of misconceptions. Things such as equating the BB to an explosion in space, the concept of the universe having an "edge", the entire pre-BB universe being the size of a proton (when I assume they mean the observable universe), that all galaxies are moving away from eachother (when the opposite is true that they are actually clustering together), etc. etc. ...

    The remedy is probably to always be skeptical of what you hear on TV, and trust the wise people here at PF! :smile:
     
  19. Jun 2, 2009 #18
    Re: Episode of "The Universe" (WMAP)

    Yah, you're right. :smile:

    I thought antimatter had negative mass for the longest time because of something I inferrred from a documentary on black hole evaporation. Now, and because I'm here, I know the truth.
     
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