A little more than a week ago scientists discovered a gamma ray burst from outer space lasting 10 seconds with a redshift of 8,2. It is calculated that the source is more than 13 billion lightyears away, probably an explosion of a star. Because of the finite speed of light, observing a lightsource 13 billion lightyears away also means observing an explosion that happened 13 billion years ago, only about 600 million years after the birth of the universe (according to the big bang theory).
At first i just thought it was cool that we are able to observe this kind of stuff. After a while I gave it some more thought: How is it that we are able to observe light from an explosion that happened more than 13 billion years ago? To answer this question, assuming the most popular theories of physics (and my knowledge of it) and the method of measurements are correct, I thought of the following:
During the first couple of million years the universe had to be expanding at a rate tremendously faster than the speed of light. If this wasn’t the case then the light of the explosion would have passed our location in the universe a couple of billion years ago (because of the limited side of the universe at an age of 600 million years) and we never would have been able to see it. After a while the expansion rate had to slow down, or the light wouldn’t be able to catch up to us, and we again wouldn’t be able to see it. Recent observations show that the galaxies surrounding us are moving away from us at an increasing rate, indicating that the expansion of the universe is accelerating again?
I don’t know if what I’m saying is correct, cause I don’t have a background in physics. But I think this observation can cause more interesting thoughts and a nice discussion. And maybe a person with a background in physics can shed some light onto this.
What this means to us, is that its completely impossible to reach the expanding end of the universe, because it expands faster than the speed of light, therefore when we got there so much more would be created already
We use standard general relativity to illustrate and clarify several common misconceptions about the expansion of the Universe. To show the abundance of these misconceptions we cite numerous misleading, or easily misinterpreted, statements in the literature. In the context of the new standard Lambda-CDM cosmology we point out confusions regarding the particle horizon, the event horizon, the ``observable universe'' and the Hubble sphere (distance at which recession velocity = c). We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light. We explain why this does not violate special relativity and we link these concepts to observational tests. Attempts to restrict recession velocities to less than the speed of light require a special relativistic interpretation of cosmological redshifts. We analyze apparent magnitudes of supernovae and observationally rule out the special relativistic Doppler interpretation of cosmological redshifts at a confidence level of 23 sigma.
If i'm understanding you correctly this might be related to how the expansion of the universe works. IIRC the universes expansion doesn't work "outwardly" per se. It's not related to outwards motion, but instead the expansion of space itself. As such, the percieved "speed" at which we move away from other objects in the universe is greater the further away from it we are since space "expands" equally everywhere. I might be terribly wrong about this tho. If i am, someone please correct me : ]
On May 06 2009 18:25 omninmo wrote: "the birth of the universe" ... humans are so vain. animals are born. existences is and never was not. you want cosmic? learn about 大道
I think he was just referring to the big bang as a birth, which it was in a way. Even if existence has always been, this last 14 billion years was the product of one big bang. Sounds like a birth to me.
On May 06 2009 18:10 D10 wrote: What this means to us, is that its completely impossible to reach the expanding end of the universe, because it expands faster than the speed of light, therefore when we got there so much more would be created already
That's why scientists are no longer trying to achieve the speed of light per se because travelling anywhere with just the speed of light will still have a journey that outlasts human lifespan.That's why they are now more curious on faster than light theories and time warp/worm hole theories.
On May 06 2009 18:10 D10 wrote: What this means to us, is that its completely impossible to reach the expanding end of the universe, because it expands faster than the speed of light, therefore when we got there so much more would be created already
That's why scientists are no longer trying to achieve the speed of light per se because travelling anywhere with just the speed of light will still have a journey that outlasts human lifespan.That's why they are now more curious on faster than light theories and time warp/worm hole theories.
Actually because of timedilatation you can travel a great distance during a human lifetime. If you have a powersource that manages to let you accelerate with 1 g during your whole lifetime, you can travel more than 13 billion lightyears.
Could anyone recommend me some good books about these theories (string theories, multiple universes), serious and "easy" enough for a beginner ? I'd really like to learn more about that eventho my physic background is rather weak.
On May 06 2009 19:05 yejin wrote: Could anyone recommend me some good books about these theories (string theories, multiple universes), serious and "easy" enough for a beginner ? I'd really like to learn more about that eventho my physic background is rather weak.
On May 06 2009 19:05 yejin wrote: Could anyone recommend me some good books about these theories (string theories, multiple universes), serious and "easy" enough for a beginner ? I'd really like to learn more about that eventho my physic background is rather weak.
I second this.
I've read "stars and falling apples" by ulf danielsson. I think it was really good and easy accessible by people without a background in physics. It covers the different theories (including relativity, and string) and other things about the universe and explains them with good and understandable examples. Also i liked "a brief history of time", by stephen hawking
On May 06 2009 19:05 yejin wrote: Could anyone recommend me some good books about these theories (string theories, multiple universes), serious and "easy" enough for a beginner ? I'd really like to learn more about that eventho my physic background is rather weak.
EPT
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