Size of the universe
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01-07-2013, 01:39 PM
Size of the universe
Can someone help me understand this? It's huge. Not interested in an appeal to religion as part of the answer.

If the Big Bang was under 14 billion years ago, how is it that there are stars and galaxies that we can observe that are more than 28 billion light years away? First off, the light hasn't had enough time to reach us. Secondly, how did we have enough time to get that far away from each other. Wouldn't we each have to be traveling faster than light to achieve this?

I'm confident science has the explanation. I'm not confident of my ability to understand it. Dr. Cooper? Dr. Hofstadter? Anyone?
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01-07-2013, 01:43 PM
RE: Size of the universe
(01-07-2013 01:39 PM)TwoCultSurvivor Wrote:  Can someone help me understand this? It's huge. Not interested in an appeal to religion as part of the answer.

If the Big Bang was under 14 billion years ago, how is it that there are stars and galaxies that we can observe that are more than 28 billion light years away? First off, the light hasn't had enough time to reach us. Secondly, how did we have enough time to get that far away from each other. Wouldn't we each have to be traveling faster than light to achieve this?

I'm confident science has the explanation. I'm not confident of my ability to understand it. Dr. Cooper? Dr. Hofstadter? Anyone?

Here is a good starter on this topic.

http://twistedsifter.com/2012/10/putting...rspective/

As to the stars that are 28 billion light years away that is because of expansion. They are moving away from us, and us from them. Think of it like this you get into a car and drive at 60 mph to the east for 30 mins your brother gets into his car (parked next to yours) at the same time and drives at 60 mph to the west for 30 mins. Even though you have only been driving for 30 mins you are now 60 miles away from each other.

(31-07-2014 04:37 PM)Luminon Wrote:  America is full of guns, but they're useless, because nobody has the courage to shoot an IRS agent in self-defense
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01-07-2013, 01:54 PM
RE: Size of the universe
Yeah 28 = 14 x 2

Also we are seeing them as they where not as they are. Looking back toward the center of the universe is like looking back in time.

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01-07-2013, 01:54 PM
RE: Size of the universe
I get that: That's why I picked 28 billion miles as a marker.

See, my brain can't wrap itself around this:

If I go in one direction at the speed of light for 14 billion years, and you go in the opposite direction for 14 billion years, how can we be MORE than 28 billion light years apart?

Also, how does space expand? What does that even mean? I can't wrap my head around it.
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01-07-2013, 01:58 PM
RE: Size of the universe
http://scaleofuniverse.com/

Insufferable know-it-all.Einstein
Those who were seen dancing were thought to be insane by those who could not hear the music - Friedrich Nietzsche
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01-07-2013, 02:04 PM
RE: Size of the universe
(appeal to religion? you... can read the site logo at the top of the screen, right? Tongue)

We can't actually see anything 28 billion light years away. Or 90 billion or whatever.

That figure is an extrapolation; what we can see, at the limits, are things as they were ~14 billion years ago. If we then assume they've continued to move (as closer, ie more contemporaneous objects have) then they're that far away now (insofar as there is a "now" - which is to say, there really isn't).

Not that 'age' and 'distance' are particularly useful terms either, as our intuitive understanding of them goes, on a cosmological scale...
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01-07-2013, 02:05 PM
RE: Size of the universe
(01-07-2013 01:54 PM)TwoCultSurvivor Wrote:  I get that: That's why I picked 28 billion miles as a marker.

See, my brain can't wrap itself around this:

If I go in one direction at the speed of light for 14 billion years, and you go in the opposite direction for 14 billion years, how can we be MORE than 28 billion light years apart?

Also, how does space expand? What does that even mean? I can't wrap my head around it.

Some Galaxies are actually moving away from us faster than the speed of light, that does not mean that they are not moving faster than the speed of light, but that we are also moving in the opposite direction at insane speeds....Also expansion is accelerating (which is super weird, 'dark energy' is the best explanation we have for this right now).

Think of space as a giant expanding balloon, and all the galaxies are on the skin of the balloon moving outward from the center point as it inflates.

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01-07-2013, 02:07 PM
RE: Size of the universe
(01-07-2013 01:54 PM)TwoCultSurvivor Wrote:  I get that: That's why I picked 28 billion miles as a marker.

See, my brain can't wrap itself around this:

If I go in one direction at the speed of light for 14 billion years, and you go in the opposite direction for 14 billion years, how can we be MORE than 28 billion light years apart?

Also, how does space expand? What does that even mean? I can't wrap my head around it.

Where are you getting 28 billion light years from? A quick google search and it seems the furthest solar system we have found is only 13 billion light years away.

http://www.dailymail.co.uk/sciencetech/a...Earth.html

(31-07-2014 04:37 PM)Luminon Wrote:  America is full of guns, but they're useless, because nobody has the courage to shoot an IRS agent in self-defense
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01-07-2013, 02:07 PM
RE: Size of the universe
(01-07-2013 01:54 PM)TwoCultSurvivor Wrote:  I get that: That's why I picked 28 billion miles as a marker.

See, my brain can't wrap itself around this:

If I go in one direction at the speed of light for 14 billion years, and you go in the opposite direction for 14 billion years, how can we be MORE than 28 billion light years apart?

Also, how does space expand? What does that even mean? I can't wrap my head around it.

Because your intuitive non-physics-educated understanding of what time and distance mean is not accurate on a relativistic scale. Isn't modern physics fun?

The classic metaphor for expanding space is to consider a two-dimensional universe, shaped like a sphere. Ie, a balloon. Consider two points drawn on it. Inflating the balloon makes those two points seem farther apart (on the surface of the balloon), even if they haven't really 'moved'.

It's not just that you're going the speed of light in one direction, and someone else is going the speed of light in the other - your relative velocity is still only ever c.

Stephen Hawking's books (a Brief History of Time, the Universe in a Nutshell) are still my go-to general audience introductions to modern physics. Have you read those, or anything like them?
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01-07-2013, 02:09 PM
RE: Size of the universe
(01-07-2013 02:07 PM)Revenant77x Wrote:  Where are you getting 28 billion light years from? A quick google search and it seems the furthest solar system we have found is only 13 billion light years away.

They're farther than that, in the sense of the question,

"If they were to stop their relative motion this instant, and I were to travel between them, how far would I have to travel?"

has an answer substantially greater than ~13 billion light years.

(01-07-2013 02:05 PM)ridethespiral Wrote:  ... we are also moving in the opposite direction at insane speeds...

Ah! We're moving away from each other at, at most the speed of light. That's the definition of relativity!

(01-07-2013 02:05 PM)ridethespiral Wrote:  Think of space as a giant expanding balloon, and all the galaxies are on the skin of the balloon moving outward from the center point as it inflates.

Balloons! Called it...
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