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Author Topic: Does the universe have an edge, and what's beyond it?  (Read 30210 times)

Offline socratus

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Does the universe have an edge, and what's beyond it?
« Reply #25 on: 07/10/2008 23:31:55 »
You're doing it again - assuming space is infinite. It's not difficult to explain how stars and galaxies formed; but they did not form from "an infinite vacuum".

Initially, the universe was too hot for matter to form. As the universe expanded, it cooled. It reached the point where elementary particles could appear. Those particles joined to become forms of hydrogen. Gravity pulled massive clumps of this hydrogen together in areas of anisotropy - wrinkles in spacetime that hadn't been totally equalised by inflation - and galaxies formed.

Within the hydrogen clouds, stars started to form. At first, gravity-powered stars formed. As those stars condensed further, they reached the point where nuclear reactions could take place to become stars as we know them today.

There; and not a single mention of infinity  :D
==========================
Thank you, for explaining.
More details:
http://en.wikipedia.org/wiki/Star_Formation
=====================


 

Offline Juggernaught

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Does the universe have an edge, and what's beyond it?
« Reply #26 on: 30/12/2008 11:15:28 »
Wow.  I am still trying to wrap my head around this.  LEEe you mentioned that the universe is now 42 billion light years large.  One of the biggest questions (from what I hear) is trying to explain how that can be if the universe is only measured at 14 billion years old.

I believe the universe is growing.  It is growing into nothing (the stuff rocks dream of). Will it collide with other universes eventually?  I doubt it.  How do you collide into another universe when the very thing you are growing into is supposedly infinite?

I am definitely no fan of infinite when it comes to our universe.  A growing and collapsing universe must still be finite.  It is an event.  Adding an event to an already infinite number of events ... well would be impossible.  A continuously expanding Universe.. same.  It had a starting point.  I dunno.  It is 5:15 in the morning here.  Just my .. I wouldn't even say 2 cents worth :)
 

Offline DoctorBeaver

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Does the universe have an edge, and what's beyond it?
« Reply #27 on: 30/12/2008 12:10:39 »
Some estimates put the size of the universe at 125 billion light years across. A lot of people have trouble understanding how that can be if the universe is only 13.5 billion years old and nothing can travel faster than light - I didn't get it at first either. The obvious assumption is that the universe cannot be more than 27 billion light years across (13.5 billion years expanding in all directions). This, however, is not what happened.

"Things" are not moving apart due to their own movement; space itself is expanding. In the very early universe (10-35 to 10-33 seconds) this expansion caused a 100-fold increase in size. This brief event is known as "inflation". Nothing was actually moving through the universe (not even light), so the universal speed limit of light was not violated.

Nobody is entirely sure what happened at 10-35 seconds to start inflation, or at 10-33 seconds to stop it. There are various theories, but as far as I am aware each has holes in it (maybe someone has more knowledge of some of those theories and can respond). The driving force behind inflation may have been the same force that is now causing the acceleration in the rate of expansion of the universe, or it may have been something totally different.

It has to be said, though, that some physicists do not go along with the inflation theory. There are certainly problems associated with it. and scientists such as Martin Bojowald are investigating other theories.

As for your question about the universe colliding with another, that depends how you define universe. There are theories that postulate our universe being 1 of many in a "multiverse". Others suggest that our universe is a 3-dimensional brane suspended in a higher dimensional bulk and that the Big Bang was caused by 2 of these branes coming together.
« Last Edit: 30/12/2008 12:14:35 by DoctorBeaver »
 

Offline @@

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Does the universe have an edge, and what's beyond it?
« Reply #28 on: 30/12/2008 21:25:52 »
this is where im troubled,the multiverse idea, in my book the universe is everything, all the stars, all the galaxies, all the clusters and yes all the multiverses and all the branes as well. the word universe should encompase all of the above
 

Offline DoctorBeaver

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Does the universe have an edge, and what's beyond it?
« Reply #29 on: 30/12/2008 22:59:13 »
this is where im troubled,the multiverse idea, in my book the universe is everything, all the stars, all the galaxies, all the clusters and yes all the multiverses and all the branes as well. the word universe should encompase all of the above

The problem is in the definition. It used to be thought that our universe had to be the only 1, so "universe" came to mean everything there could possibly be. Now, however, we know that the laws of physics allow for other "universes". As a result, most physicists now use "universe" to mean a self-contained spacetime and all its contents.
 

Offline yor_on

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Does the universe have an edge, and what's beyond it?
« Reply #30 on: 30/12/2008 23:02:29 »
How do you think here?
If we have a universe created at the BB with an approximate size of the one we are seeing now.
And then allow it to be expanding but not as 'fast' as that first 'inflationistic' moment was.
If so you will find galaxies forming all around us separating them self by 'vacuums' expansion.
But the size is of course also defined by what light sources we can see.
As for now I believe the distance is around 13.5 billions lightyears.
http://en.wikipedia.org/wiki/Universe

But we can by better technology 'reach' farther out (back in time), but not farther than what weak 'light' might have reached us.
http://helios.gsfc.nasa.gov/qa_sp_pr.html#ageuniv

As for how you get this size to 64 whatever I just don't know?
No inflation and instead an expansion?
Sorry, you can 'see' that BB and inflation as a 'thumbprint' in the 'sky' looking at our universe.
If you like I will try to link to that too.
« Last Edit: 30/12/2008 23:04:05 by yor_on »
 

Offline DoctorBeaver

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« Reply #31 on: 30/12/2008 23:05:08 »
The earliest we can possisbly see is the horizon of last scattering. That occured about 300,000 years after the Big Bang when the universe became cool enough for photons to move freely. We see that horizon as the cosmic microwave background.
 

Offline yor_on

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Does the universe have an edge, and what's beyond it?
« Reply #32 on: 30/12/2008 23:20:25 »
Background radiation is one way to describe the age, but that's defined by theory as this radiation exist all around us. not caring for lights speed.
Am I right?

What we do have defining our universe is the speed of light.
 

Offline DoctorBeaver

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« Reply #33 on: 31/12/2008 00:01:56 »
The CMBR is most definitely subject to the speed of light. It is composed of photons so it must be.

I'm not sure what you mean by "What we do have defining our universe is the speed of light.". Do you mean that the speed of light defines the size of the universe? If so, then that is not necessarily true. During the period of inflation the universe expanded much faster than the speed of light1. If, however, you mean our visible universe, then you are correct.

1. There is a popular misconception about the speed of light. What is limited is the transfer of information. There is nothing to stop superluminal speeds so long as no information is involved.
 

Offline Mr. Scientist

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Does the universe have an edge, and what's beyond it?
« Reply #34 on: 31/12/2008 04:17:59 »
The CMBR is most definitely subject to the speed of light. It is composed of photons so it must be.

I'm not sure what you mean by "What we do have defining our universe is the speed of light.". Do you mean that the speed of light defines the size of the universe? If so, then that is not necessarily true. During the period of inflation the universe expanded much faster than the speed of light1. If, however, you mean our visible universe, then you are correct.

1. There is a popular misconception about the speed of light. What is limited is the transfer of information. There is nothing to stop superluminal speeds so long as no information is involved.

Doctorbeaver,

Could you tell me, did you say this yourself:

''1. There is a popular misconception about the speed of light. What is limited is the transfer of information. There is nothing to stop superluminal speeds so long as no information is involved.''

Because i am working on my own model of information, quantum information moving faster-than-light... because if that qoute wasn't your own, i would like to know who did say it.

Thanks ;)
 

Offline Soul Surfer

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Does the universe have an edge, and what's beyond it?
« Reply #35 on: 31/12/2008 09:41:32 »
The generalised expansion of space allows bodies to be moving apart at speeds greater than the velocity of light.  This just means that no communication can take place between these bodies.  The bodies themselves are not moving faster than light just at normal intergalactic relative velocities of hundreds of miles a second it is the space between them that is expanding.

To visualise what is going on It is best to think first of an indefinitely large static universe with stars and galaxies all moving around under the influence of gravity each with ther own motions and then overlay it with a generalised expansion of space.

It is also important to remember One critical rule of gravity.  For a uniformly distributed medium of indefinate extent (ie no edges anywhere near) the net gravitational field is zero because the gravitational effects of all the bodies around effectively cancel themselves out.
 

Offline Mr. Scientist

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Does the universe have an edge, and what's beyond it?
« Reply #36 on: 31/12/2008 09:44:53 »
Ah i see. He was talking about tangible signals, such as electromagentic and gravitational.

Thanks
 

Offline yor_on

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« Reply #37 on: 31/12/2008 12:44:07 »
Well :) my view what this that under that first stage of 'inflation' when the universe expanded FTL you got this radiation more or less uniformly.
But how that may tell us the age I'm not sure on?

My thought was that to see our universe (age/size) we would need what 'light/wavelengths' that may reach us from 'light-sources' created after our universe's birth.
Even though there might be light not even reaching us depending on that inflationary phase (and later expansion)

It might be possible to define our 'age' by the background radiation?
But that will hang on what experimental evidence you can create for your hypothesis i think.
http://en.wikipedia.org/wiki/Big_bang#Cosmic_microwave_background_radiation

--------------------

But yeah, What you write about FTL is correct.
Although I'm not sure what it might do.

If you can find some way to connect it to that inflation our Universe experienced I would become very interested though:)

For those not getting DB:s idea here
"1. There is a popular misconception about the speed of light. What is limited is the transfer of information. There is nothing to stop superluminal speeds so long as no information is involved."

You can read Guest_carbonlife explanation at.
http://www.physforum.com/index.php?showtopic=6487&st=0&#entry89788
And as it goes into entanglement he wrote another interesting piece here.
http://www.physforum.com/index.php?showtopic=15781&st=0&#entry228640

Yep, he is very clear on those subjects I think
« Last Edit: 31/12/2008 13:16:26 by yor_on »
 

Offline DoctorBeaver

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« Reply #38 on: 31/12/2008 23:07:26 »
Ah i see. He was talking about tangible signals, such as electromagentic and gravitational.

Thanks

Any kind of information.
 

Offline Mr. Scientist

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Does the universe have an edge, and what's beyond it?
« Reply #39 on: 02/01/2009 07:02:47 »
Ah i see. He was talking about tangible signals, such as electromagentic and gravitational.

Thanks

right. well, i don't believe that. I think certain types of quantum information my travel at superluminal speeds, but i will keep my speculations out of this.

Any kind of information.
 

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Does the universe have an edge, and what's beyond it?
« Reply #39 on: 02/01/2009 07:02:47 »

 

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