[ExI] The Size of the Universe

[Lee Corbin]

I Just thought I'd follow up my exposition of Guth's marvelous
presentation (see below)  with some of Tegmark's remarks
from his great http://it.arXiv.org/abs/astro-ph/0302131 :

    "The farthest you can observe is the distance that light
    has been able to travel during the 14 billion years since
    the big bang expansion began. The most distant visible
    objects are about 4x10^26 meters away."

Remember this handy trick:  there are 10^16 meters per lightyear.

    [Tegmark adds the following in a footnote at this point]
    "After emitting the light that is now reaching us, the
    most distant things we can see have receded because
    of the cosmic expansion, and are now about 46 billion
    light years away."

(I corrected his figure slightly to agree with the most recent
sources.) Therefore the *diameter* of our visible universe
is 92 billion lightyears.

Still---the unwashed (all over the web) continue through their
benightedness to insist on the simplistic figure of 13.7 lightyears
for the radius---as if no expansion were taking place. Beware!

The central truths here 

   1. We see things that are 46 billion light years away.

   2. They were about 45 million light years away when,
      at 300,000 AB, they sent out photons that are
      finally arriving here today. [See Guths figures 
      and explanations in the addendum to this post]

That's a factor of about 1000! Those objects are about one
thousand times further away now than when they sent their light
to us 13.4 billion years ago (i.e., when the universe became
transparent .3 billion years after the big bang). So the usual
size given by people for the visible universe is way off.

The first four pages of Tegmark's article are fairly easy to
follow (if you remember the trick above for converting
meters to lightyears).

The first page is mostly what I said above, but with more detail

The second page is a gorgeous depiction of the four levels.
Print it out and tape it to your refrigerator.

Level One: our own infinite universe (i.e., our bubble, both
of which I have christened "Bruno", after the first modern man,
or "Lucretius Bruno" to give them both credit. They claimed
that space was infinite and had infinitely many suns, and
Bruno was burned at the stake for so saying so.[note A]

Page three describes the uniformity of structures bigger than
about 300,000,000 million lightyears, a small fraction of 
our Hubble volume (i.e. visible universe). After that, it looks
uniform. Therefore since 300,000,000 goes into 46 billion
about 150 times, there are about 150x150x150, or about
four million homogeneous volumes that we can see inside
our Hubble Volume (our visible universe). So it's pretty absurd
to think that we are sitting in the middle of all that there is.
(Picture our *visible* universe being tiled by millions of 
homogeneous patches, to say nothing of what lies beyond.)

Writes Tegmark at the bottom of page 3:

     Barring conspiracy theories where the universe is
     designed to fool us, the observations thus speak
     loud and clear: space as we know it continues far
     beyond the edge of our observable universe,
     teeming with galaxies, stars, and planets.

Lee

[A] For a good essay on Bruno please see
http://www.spaceandmotion.com/Philosophy-Giordano-Bruno.htm

Also there you will find

    http://members.aol.com/pantheism0/brunphil.htm

    "Fantastic site on Giordano Bruno pantheist philosophy.
    From the great Roman poet Lucretius, Bruno took two of
    his central ideas: an infinite Space with infinite worlds,
    and matter that was made up of discrete atoms combining
    in different ways to make up all the diversity we see."

So Lucretius and Bruno saw the truth first. I now put forth
the suggestion publicly, that the official name of our universe,
our Level One infinite universe, our Level Two bubble be
henceforth "Lucretius Bruno".

Lee


----- Original Message ----- 
From: "Lee Corbin" <lcorbin at rawbw.com>
To: "ExI chat list" <extropy-chat at lists.extropy.org>
Sent: Thursday, September 25, 2008 1:15 PM
Subject: Re: [ExI] Who's stealing our universe?


> BillK points to the interesting
> 
>> Another article interviewed the scientists involved in
>> this discovery and apparently they were quite surprised
>> by theses unexpected findings.
>> <http://www.space.com/scienceastronomy/080923-dark-flows.html>
> 
> The "science writer" responsible for this outrage should
> be prosecuted. Thanks for bringing this thought-criminal
> to the attention of the committee, Bill.
> 
> Some excerpts:
> 
>    When scientists talk about the observable universe, they don't
>    just mean as far out as the eye, or even the most powerful
>    telescope, can see. In fact there's a fundamental limit to how
>    much of the universe we could ever observe, no matter how
>    advanced our visual instruments. The universe is thought to have
>    formed about 13.7 billion years ago.
> 
> Yes, I'm sure he read that somewhere, or someone mentioned it to him.
> Okay. But then
>                                       So even if light started
>    traveling toward us immediately after the Big Bang, the farthest
>    it could ever get is 13.7 billion light-years in distance. There
>    may be parts of the universe that are farther away (we can't know
>    how big the whole universe is), but we can't see farther than
>    light could travel over the entire age of the universe.
> 
> The writer has no understanding whatsoever how the expansion of
> the universe plays into this. At 300,000 AB [1], photons got free
> when the universe became transparent to light, and some of them
> started heading right at us, but got yanked further away from us
> by inflation.  The poor photons knew where they were headed,
> but to them the space between them and their target really blew up.
> 
> The best explanation is to be found in the book written
> by the originator of inflation, Mr. Alan H. Guth [1]
> himself, "The Inflationary Universe". On pages 182 - 184
> he describes what went on.
> 
> That number, 300,000, is very important in what
> follows.
> 
>    "At 300,000 years, the horizon distance was about
>    900,000 light years. [Here Guth means that two
>    photons starting out "nearby", i.e. within a tiny
>    fraction of an inch at the Big Bang and aimed
>    right at us but coming from opposite directions,
>    would already have each been yanked back 900,000
>    ly because of the stupendous inflation expansion.]
> 
>    "If the universe were static, the horizon distance
>    would have been about 300,000 light years [since
>    in *that* case we would have had only time to get
>    ones aimed at us from that distance, since that
>    was the age of the universe]. In an expanding
>    universe, however, photons can make extra progress
>    during the early period, when the universe was
>    small, so the horizon distance is larger than one
>    would expect."
>    
> Note that what Guth is saying is very tricky. Read the
> above at least as much as to understand what scientists
> mean by the terms, and how they use them, as to try
> to understand what is being said. Guth goes on:
> 
>    "If we consider two photons arriving *today* [italics
>    added] from opposite directions in the sky, then we
>    can use the mathematics of the Big Bang theory to 
>    trace back the trajectories to 300,000 AB. The 
>    calculation, which takes into account the expansion
>    of the universe, shows that the photons were emitted
>    from two points [at the time] about 90,000,000 ly
>    apart. Let A and B label the two points at which
>    these two photons were emitted [one to the left of
>    us 45,000,000 ly and the other to the right of us
>    45,000,000 ly]. The uniformity of the cosmic background
>    radiation temperature implies that the temperature
>    was the same at points A and B (to an accuracy of
>    one part in 100,000), yet they were separated from
>    each other by  about 100 times the horizon difference
>    [at the time]."
>    
> So he's saying, in effect, "now how the hell could that be? There
> is no goddam way that they could be at the same temperature
> unless something weird is going on---because ninety *million*
> light years at only 300,000 AB makes that look impossible.
> How could their temperatures have been reconciled? How 
> could they have "known" each other thermodynamically?"
> 
>    "Since nothing travels faster than light, in the
>    context of the standard big bang theory [get ready
>    for his inflation!] there is no physical process
>    that can bring these two points to the same 
>    temperature by 300,000 years after the big bang."
>    
> So, he says in a footnote here, "The rate of separation,
> therefore, was much larger than the speed of light", and
> explains why your mind should not be blown by this.
> 
> In a caption to the diagram, he then goes on like
> this (thank God for a little redundancy!).
> 
>     "The Horizon Problem of the Standard Big Bang Theory".
>     [paraphrased by me, since you cannot see the diagram]
>     The diagram shows a picture of the universe at 300,000
>     years after the big bang, when the cosmic background 
>     radiation was released. At the center of the diagram is
>     the matter that will eventually become the Earth. At the
>     left is point A, where one is headed towards us from the
>     left. At point B on the right is where the leftward moving
>     photon is coming at us from the right. They are only at
>     90,000,000 light years away from each other!
> 
>     "The "horizon distance", however, was only 900,000 ly.
>     The points A and B were separated from each other by
>     about 100 times the distance that light could have traveled
>     since the Big Bang."
> 
> So that science writer is clueless about how the terms are
> used, and how inflation actually provided for a far, far
> vaster universe than the little thing that we can see. Our
> "horizon distance" of course, has never caught up to
> what was propelled away so long ago.
> 
> Now, of course, it *could* be that we are exactly at
> the center of all there is, and that indeed our "bubble"
> only goes out as far as we can see. What is the $&%$!
> chance of that? Can you just picture some aliens 10
> billion light years from here saying, "Oh, gee, there must
> be something special about that point off yonder at the
> center, since we are so close to the edge of the bubble."
> 
> The writer and one scientist go on:
> 
>    They discovered that the clusters were moving nearly 2 million
>    mph (3.2 million kph) toward a region in the sky between the
>    constellations of Centaurus and Vela. This motion is different
>    from the outward expansion of the universe (which is accelerated
>    by the force called dark energy).
> 
>    "We found a very significant velocity, and furthermore, this
>    velocity does not decrease with distance, as far as we can
>    measure," Kashlinsky told SPACE.com. "The matter in the
>    observable universe just cannot produce the flow we measure."
> 
> Well, duh! Do these guys think that the observable universe is
> all that there is? Or that maybe just beyond the edge of what
> we see, it all becomes Very Different? What a coincidence
> that we are at the exact center of normalcy. Yes, I understand
> that they have evidence of something outside our visible 
> universe, but it is *not* outside our bubble, which is probably
> infinite.
> 
> The inexperienced science writer now tries his own hand at
> explaining:
> 
>    A theory called inflation posits that the universe we see is just
>    a small bubble of space-time that got rapidly expanded after the
>    Big Bang. There could be other parts of the cosmos beyond this
>    bubble that we cannot see.
> 
> No, the universe that we can see is not any "bubble" as the term
> is commonly used. Again, if it were, wouldn't that be a fantastic
> coincidence that we're right at the center of it. Perhaps the ancient
> anthropomorphism and mankind needing to be at the center of the
> universe is sneaking back into his thinking.
> 
>    In these regions, space-time might be very different, and likely
>    doesn't contain stars and galaxies (which only formed because of
>    the particular density pattern of mass in our bubble). It could
>    include giant, massive structures much larger than anything in our
>    own observable universe. These structures are what researchers
>    suspect are tugging on the galaxy clusters, causing the dark flow.
> 
> I *hope* that the science writer has just consulted his own imagination
> here. OF COURSE the universe just contains stars and galaxies right
> outside our visible universe. It may be that some of it is grouped
> weirdly, and that's what they've found. But the *uniformity* of our
> universe begins at only about 300,000,000 light years, much, much
> smaller than the visible universe. Tegmark said *specifically* that
> all the small scale variations wash out when you get up to about
> 300,000,000 light years, and then it's uniform after that (or at least
> that was what was thought until now). But that does not change
> the fact that the very little patch we live in, some 300,000,000
> light years in diameter, is more or less regularly repeated right up
> to the edge of the visible universe, i.e., picture the visible universe
> (at which we are indeed at the center of) as being tiled by very,
> very similar patches all the way out to 42 billion light years away,
> i.e., more than 42x3 = 120 similar patches in each of the three
> directions. 
> 
> And because of inflation, the radius of the observable universe
> turns out to be, when they did all the calculations, about three
> times the 13.4 billion years that light has been in straight line
> motion (i.e., 300,000 AB), or 42 billion light years. Hence
> our visible universe has a diameter of 84 billion light years.
> 
> Yet in one direction, well, they've seen something odd. Could be,
> I suppose.
> 
> The science writer then actually quotes this person Kashlinsky
> (I dare not say guy, because "Alexander" could be a woman's
> name these days.)
> 
>    "The structures responsible for this motion have been pushed so
>    far away by inflation, I would guesstimate they may be hundreds of
>    billions of light years away, that we cannot see even with the
>    deepest telescopes because the light emitted there could not have
>    reached us in the age of the universe," Kashlinsky said in a
>    telephone interview. "Most likely to create such a coherent flow
>    they would have to be some very strange structures, maybe some
>    warped space time. But this is just pure speculation."
> 
> Dr. K. is giving one a bad idea of how inflation works, and is
> contributing to the incredibly antiquated notion that we are
> at the center. Nothing was pushed away!  Or, if you must speak
> that way, we were just as pushed away as was it. Instead, 
> the *space* between galaxies was expanded, nothing got
> pushed. And then he ends with "But this is just pure speculation".
> Science writing, I fear at it's worst.
> 
> I just hope that they don't have an affirmative action program for
> Poles or Russians or whatever the hell he or she is, and that we
> can depend on his or her words---so long as we understand that
> he or she is still in the process here of explaining what the speed
> of light is to that inexperienced science writer.
> 
> Lee
> 
> 
> [1] "At 300,000 years AB", (i.e. After Bruno, the
> name of our universe, which, so far as I know, I was
> the first person to have named, as I was notified in
> a couple of emails from people I had never heard
> of back a few years ago, or, if you wish, After Bang,
> or After Beginning)
> 
> [2] Alan Guth explains in his book that the acronym
> GUT for "Grand Unified Theories" is not faithful to
> the  Greek roots of the word "theory", where "th" is
> represented by the single letter [theta], i.e., that the
> proper acronym is really GUTH.