Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Chrismalta on 01/10/2008 20:00:05
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Christopher Bianco asked the Naked Scientists:
Today I came across this report about an explosion originating near the edge of the universe, seen by an orbiting NASA telescope. The burst of gamma rays is the farthest such event ever detected.
I just can't understand the edge of universe? Does the universe has a real edge and what's beyond it??
Thanks
Chris Bianco from Malta
What do you think?
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They probably meant the edge of the visible universe. Since light travels at a finite speed, it can only have traveled a certain distance in the 14 billion years the universe has been around. The light which can reach us defines a giant sphere (radius = 14 billion parsecs) around the earth. If something is further away than that, its light won't have reached us yet.
Since light-speed is the speed limit for everything in the universe, nothing from beyond this region will have reached us yet, and so we don't know what's beyond it. Most scientists tend to believe in the cosmological principle, which says that the universe is pretty much the same everywhere, at least on large scales. Therefore, it should be basically the same outside our visible universe as it is inside.
There's a lot more details here: http://en.wikipedia.org/wiki/Observable_universe
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They probably meant the edge of the visible universe. Since light travels at a finite speed, it can only have traveled a certain distance in the 14 billion years the universe has been around. The light which can reach us defines a giant sphere (radius = 14 billion parsecs) around the earth. If something is further away than that, its light won't have reached us yet.
Since light-speed is the speed limit for everything in the universe, nothing from beyond this region will have reached us yet, and so we don't know what's beyond it. Most scientists tend to believe in the cosmological principle, which says that the universe is pretty much the same everywhere, at least on large scales. Therefore, it should be basically the same outside our visible universe as it is inside.
There's a lot more details here: http://en.wikipedia.org/wiki/Observable_universe
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Does the universe have a real edge and what's beyond it??
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Let us suppose that the universe is “a giant sphere
(radius = 14 billion parsecs) around the earth. “
Is it possible to universe to be “a giant sphere
(radius = 14 billion parsecs) around the earth. “ ?
NO !!! Why?
Because the detected material mass of the
matter in the Universe is so small (the average density
of all substance in the Universe is approximately
p=10^-30 g/sm^3) that this mass cannot turn the universe
into sphere. So, the Universe as whole is flat infinite space.
Then we have question:
“ Does infinity space have any physical parameters?”
My answer is : “ Yes, the Infinite Universe has one
physical parameters. It is T=0K. Because after “ big bang”,
we must take in calculation that T=2,7K expands and therefore
T=2,7K is temporary parameter and with time it will go to T=0K.
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Correct in principle; but aren't the maths a bit awry? 1pc = 3.26 light years. Therefore the edge of the visible universe is 14billion/3.26 parsecs, not 14 billion parsecs.
Socratus - I assume your 2.7K refers to the CMBR. Surely, that can't ever reach 0K as that would imply zero energy level and QM says that is impossible.
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Correct in principle; but aren't the maths a bit awry? 1pc = 3.26 light years. Therefore the edge of the visible universe is 14billion/3.26 parsecs, not 14 billion parsecs.
The extra distance is due to the expansion of the universe. I didn't discuss that detail since it's a bit tricky to grasp. The light has been traveling at c, but the space between us and those distant stars has stretched. Your numbers are right if the universe is static.
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Socratus - I assume your 2.7K refers to the CMBR. Surely, that can't ever reach 0K as that would imply zero energy level and QM says that is impossible.
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Classic physics says that we can't reach 0K.
We can’t reach T= 0K !!!
But not the Nature ( micro particles ) itself !!!
The Nature ( micro particles ) can reach T= 0K !!!
Therefore Quantum theory says that vacuum ( even T= 0K )
is continuum with NO Zero Energy level !!!
That is reason that “ virtual particles “ can exist in Vacuum.
And QT says that from these “ virtual particles “ the real particles
can be born.
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Correct in principle; but aren't the maths a bit awry? 1pc = 3.26 light years. Therefore the edge of the visible universe is 14billion/3.26 parsecs, not 14 billion parsecs.
The extra distance is due to the expansion of the universe. I didn't discuss that detail since it's a bit tricky to grasp. The light has been traveling at c, but the space between us and those distant stars has stretched. Your numbers are right if the universe is static.
Are you sure about that? 3.26 light years is 3.26 light years. If 2 objects are 3.26 light years apart and the space between them expands, then they are now more than 3.26 light years apart. A parsec is still 3.26 light years.
Having it the way you stated would be like having an elastic ruler. You could stretch it and measure 3cm, but it wouldn't really be 3cm, it would be more.
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I'm not sure I follow you. What I was trying to get across was that if the universe wasn't expanding, the furthest things we could see would be 14 billion light years away. The numbers I give are answers to the question, "How far away from us (currently) is the most distant object we can see?" In a universe that wasn't expanding, the answer would be 14 billion light years. However, since the universe is expanding as the light is traveling, the space between us and that object has expanded since it emitted that light, and so it is actually 46 billion light years (14 parsecs) away.
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Let's see if I understand you correctly. What you are saying is that although the light we see was emitted 14 billion years ago, the object that emitted it is now 42 billion light years away due to the expansion of the universe. Is that what you mean?
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Yes, that's basically it.
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OK. I misunderstood at first.
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Heh - yeah - the furthest stuff we can see is now ~42 billion light years away, but the photons we see only originated ~13-14 billion light years away. Of course, they ended up traveling a lot further than that to reach here, so it depends on how you define it - it could be the distance between us and (a) the object's current distance, (b) the object's original distance, or (c) just the total distance traveled by the photon [;D]
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LeeE - Stop confusing the issue even more! [:P]
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jp
46 billion light years (14 parsecs) away.
??
1pc is only 3.26ly, actually. You mean 14 billion pc, I think.
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jp
46 billion light years (14 parsecs) away.
??
1pc is only 3.26ly, actually. You mean 14 billion pc, I think.
Yeah, I dropped a billion somewhere. Good catch. :)
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PAH... what's a billion here & there between friends!
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14 or 14 billion: you'd be no nearer to the edge.
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1.
quote author=DoctorBeaver
PAH... what's a billion here & there between friends!
2.
quote author=sophiecentaur
14 or 14 billion: you'd be no nearer to the edge.
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Nice.
It only remains to understand what infinity is.
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We've a long way to go yet.
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We've a long way to go yet.
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It is pity. Is our intellect really so poor ?
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We've a long way to go yet.
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It is pity. Is our intellect really so poor ?
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Our knowledge is
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We've a long way to go yet.
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It is pity. Is our intellect really so poor ?
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Our knowledge is
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Sorry, another paradoxical question:
How can Infinity have its Edge ?
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It can't
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It can't
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It can’t.
It can’t, because this question seems paradoxical:
“How can Infinity have its Edge ? “
It sounds like two mutually exclusive of terms;
“infinity and edge”, “infinity and finite ”, “ infinity
and limit”…..etc. And I wanted to ask: “How does
infinity connect with concreteness ? ”
I took this idea from German philosopher Georg. Hegel .
On his opinions it is possible to know the connection between
the infinite and the concrete, and to know about this connection
not only with quantity, but also with quality. And he wanted
to find rational and scientific explanation of this connection.
And you wrote:” It can’t. “. ( It cannot be.)
Okay. I ask this question in other way: “ How can from
Infinite Vacuum space the local stars formations appear ?”
I don’t think that this question is paradoxical.
I think this question is unsolved process in our Universe.
Can this process be ?
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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]
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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]
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Thank you, for explaining.
More details:
http://en.wikipedia.org/wiki/Star_Formation
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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 :)
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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 ;)
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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.
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Ah i see. He was talking about tangible signals, such as electromagentic and gravitational.
Thanks
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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
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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
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Ah i see. He was talking about tangible signals, such as electromagentic and gravitational.
Thanks
Any kind of information.
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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.