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Author Topic:   Size of the Universe
Rrhain
Member
Posts: 6351
From: San Diego, CA, USA
Joined: 05-03-2003


Message 4 of 22 (493481)
01-09-2009 3:12 AM
Reply to: Message 1 by Hoof Hearted
01-08-2009 7:00 PM


Hoof Hearted writes:
quote:
Of course the answer was 'Inflation'.
Incorrect. It isn't "inflation." Rather, it is "expansion." The inflationary period of the universe was a brief moment. However, the universe is still expanding. That means that if you start on one edge of the universe and head toward the other, the other edge is getting further away from you as you travel and thus you will have crossed a longer distance to reach the other side than what was when you first started.
Thus, a photon that started the journey nearly 14 billion years ago to reach us would have had to have crossed 78 billion light years to reach us due to the expansion of the universe. Thus, 78 + 78 = 156 billion light years across.
And getting bigger all the time.
Universe Measured: We're 156 Billion Light-years Wide!

Rrhain

Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

This message is a reply to:
 Message 1 by Hoof Hearted, posted 01-08-2009 7:00 PM Hoof Hearted has replied

Replies to this message:
 Message 5 by Hoof Hearted, posted 01-09-2009 3:36 AM Rrhain has replied
 Message 7 by cavediver, posted 01-09-2009 5:58 AM Rrhain has not replied

  
Rrhain
Member
Posts: 6351
From: San Diego, CA, USA
Joined: 05-03-2003


Message 14 of 22 (493595)
01-09-2009 4:42 PM
Reply to: Message 5 by Hoof Hearted
01-09-2009 3:36 AM


Hoof Hearted responds to me:
quote:
If a photon started its journey 13.7 billion years ago, how can it travel across 78 billion light years of space in that time?
I'm sorry. I was a bit unclear. Again, the universe is expanding. Not only is your destination receding from you, your point of origin is, too. Thus, assuming a static universe, the light traveled nearly 14 billion light years. But because the universe expanded while the light was traveling, that point of origin is now 78 billion light years away. The photon covered every point in between, but the points weren't always so close.
quote:
Yes the Universe is expanding, but it is expanding at sub-light speeds
That doesn't matter. It is still expanding. Light is fast, but the universe is huge. It still takes a long time to get across it.
quote:
My logic tells me that less 13.7 billion light years of expansion would have occured in the 13.7 billion years since the end of the inflation period.
Then you need to put that logic aside. The expansion is occurring everywhere at once. You can't think of it in three-dimensional terms. Space doesn't work like that. You're assuming a fixed frame of reference and as we have long since learned from relativity, there is no such thing.
quote:
So at the end of the inflation period, the universe must have been at least 128 billion light years across.
Incorrect. As the article pointed out, a million years after the Big Bang, the universe was 1000 times smaller than it is now, which if the calculations are correct, would put it at 150 million light years across.
quote:
So photons from the edge of the observable universe must have travelled across more than 64 billion light years of space to reach us. How can light travel this distance in less than 13.7 billion years?
Because when they started, the universe wasn't that big. During the journey, the universe expanded. There's a thought experiment that can help you visualize it, but not completely because it, too, assumes a fixed frame of reference:
Assume you're on one end of a rubber sheet, trying to get to the other side. You start walking at a constant rate toward it. As you walk, the sheet stretches, pulling the two ends further and further apart. It is going to take you much longer to reach the other end.
quote:
Obviously there is an error in my logic somewhere.
It's because you are assuming a static frame of reference to measure against. There is no such thing. And with space itself expanding everywhere at once, distance and time cannot be measured linearly.

Rrhain

Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

This message is a reply to:
 Message 5 by Hoof Hearted, posted 01-09-2009 3:36 AM Hoof Hearted has not replied

Replies to this message:
 Message 15 by DevilsAdvocate, posted 01-09-2009 10:34 PM Rrhain has not replied

  
Rrhain
Member
Posts: 6351
From: San Diego, CA, USA
Joined: 05-03-2003


Message 17 of 22 (493644)
01-10-2009 4:10 AM
Reply to: Message 16 by fallacycop
01-10-2009 3:10 AM


fallacycop writes:
quote:
Do you have any idea where the 156 billion figure came from? did they just pull that one out of their asses?
No. They actually did calculations and reached the conclusion that the edge of the universe is 78 billion light years away. Well, since we're just as far away from one edge as the other, that gives a figure of 156 billion lights years across.
Neil Cornish is an astrophysicst as Montana State University:
the starting point of a photon reaching us today after travelling for 13.7 billion years is now 78 billion light-years away
While I certainly respect cavediver's opinion, he is confusing the results of the study for his own ideas of what they were studying. That is, he is confusing the size of the universe with the size of the observable universe.
Indeed, the edge of the observable universe is about 46 billion light years away. The results of this study are not about the edge of the visible universe but rather the edge of the universe. The two are not the same.
The finding by Neil J. Cornish, David N. Spergel, Glenn D. Starkman, and Eiichiro Komatsu as published in Physical Review Letters, "Constraining the Topology of the Universe" is that the universe has a lower bound of 24 gigaparsecs distance in every direction:
The first year data from the Wilkinson Microwave Anisotropy Probe are used to place stringent constraints on the topology of the Universe. We search for pairs of circles on the sky with similar temperature patterns along each circle. We restrict the search to back-to-back circle pairs, and to nearly back-to-back circle pairs, as this covers the majority of the topologies that one might hope to detect in a nearly flat universe. We do not find any matched circles with radius greater than 25. For a wide class of models, the nondetection rules out the possibility that we live in a universe with topology scale smaller than 24 Gpc.
They think that if we get a better map of the anisotropy, they could extend it out to about 28 Gpc.
And more importantly, note that the discovery is not technically the size of the universe. Instead, it is a lower bound on the size of the universe. The universe could easily be larger...it just can't be smaller than 24 Gpc.

Rrhain

Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

This message is a reply to:
 Message 16 by fallacycop, posted 01-10-2009 3:10 AM fallacycop has not replied

Replies to this message:
 Message 18 by cavediver, posted 01-10-2009 5:16 AM Rrhain has not replied

  
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