<p>Particles are generated and destroyed all the time. This is obvious for photons, but also holds for massive particles. Today most particles are stable and long-living, but shortly after the big bang the universe was so hot that particle generation and destruction were in some equlibrium and <em>all</em> particles participated in this process (for photons this continued until the epoch of re-ionisation at redshift $z\sim1000$. There is definitely no particle around today that existed all the time since $t=0$.</p>

CC BY-SA 3.0
2014-08-28T18:15:32.213Z
2014-08-28T18:15:32.213Z
Walter
<p>If you trace two particles' world line backwards in time, according to current theory, both objects should converge at big bang.</p>

<p>Would both objects arrive there simultaneously?</p>

<p>Another way of asking the question:</p>

<p>Is there any evidence that supports the idea that new matter is "introduced" into the universe as a continuous stream, as opposed to everything coming from a singularity both in time and space?</p>

<p>The analogy would be from the inside of a black hole. For each particle in that singularity, they would all have a world line that starts at the same spacial coordinate, but the particles would not be "introduced" into the black hole simultaneously. You can argue that time stops having meaning in a black hole, but that's only true for an "outer observer" in my reasoning.</p>

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2014-08-27T17:09:29.753Z
It seems like the answer is in your first sentence. Both objects originated at the same point in "time". To address the second part: introducing new matter into the universe would violate the law of conservation of energy. You would of course be right to object that the big bang introduced new matter and energy into the universe, but that period in history is still not well understood - though many have, and still are, trying.
HDE 226868
CC BY-SA 3.0
2014-08-28T20:40:26.170Z
@hde226868 It depends on your perspective on the universe. I believe "our" universe is simply the center of a black hole in a much older and larger universe. New energy can certainly be introduced into such a "sub universe", without violating the law of conservation of energy. You can of course argue that I'm not talking about the "grand universe" then - but for all intents and purposes we can't exit this black hole I believe we're inside. Thus, for us it will be the universe.
frodeborli
CC BY-SA 3.0
2014-08-28T20:42:28.327Z
I would argue that you're talking about fringe science and any statements to that effect would be off-topic.
HDE 226868
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2014-08-28T20:51:54.513Z
Apologies; looking back, that sounded overly snarky.
HDE 226868
CC BY-SA 3.0
2014-08-28T22:19:49.460Z
@HDE226868 There are many observed effects that I believe can be explained by such a "sub universe". For example accelerating universal expansion, isotropy of cosmic background radiation, big freeze seems a natural consequence,
frodeborli
CC BY-SA 3.0
2014-08-28T22:23:11.200Z
It doesn't matter, this doesn't relate to the question. And how did you draw those conclusions?
HDE 226868
CC BY-SA 3.0
2014-09-01T18:30:45.120Z
@HDE226868 It seems obvious that at crossing the event horizon an object is "spaghettified" recursively until you're left with the tiniest of particles, or perhaps some energy/particle hybrid. Eventually that particle will reach the center of the singularity, and the spaghetification will be working internally on the particle more than externally. This will look like universal shrinking, which I believe is indistinguishable from an accelerating universal expansion - leading to a big freeze. In any direction, you're looking at the center of the black hole we originally entered - leading to CBR.
frodeborli
CC BY-SA 3.0
2014-09-01T19:19:19.240Z
Finally; I fully adopt the notion that time and space is exactly the same. This implies that also physical distance is four dimensional, allowing us to observe particles as not being at the same "spot" i.e. have a physical shape - while another observer may see it as a singularity.
frodeborli
CC BY-SA 3.0
2014-09-01T19:41:15.227Z
This makes no sense, and all stems from the theory that we're all inside a black hole.
HDE 226868
CC BY-SA 3.0
2014-09-13T23:19:44.093Z
Incidentally - and rather ironically - see this question: http://astronomy.stackexchange.com/questions/6305/is-it-possible-that-a-ultra-large-portion-of-the-space-we-live-in-is-already-ins. I think this supports my point.
HDE 226868
<space-time><big-bang-theory><general-relativity>
World line coordinate finiteness
frodeborli
# World line coordinate finiteness

(Asked by: username_0 on 2014-08-27)

If you trace two particles' world line backwards in time, according to current theory, both objects should converge at big bang.

Would both objects arrive there simultaneously?

Another way of asking the question:

Is there any evidence that supports the idea that new matter is "introduced" into the universe as a continuous stream, as opposed to everything coming from a singularity both in time and space?

The analogy would be from the inside of a black hole. For each particle in that singularity, they would all have a world line that starts at the same spacial coordinate, but the particles would not be "introduced" into the black hole simultaneously. You can argue that time stops having meaning in a black hole, but that's only true for an "outer observer" in my reasoning.

**Tags:** space-time, big-bang-theory, general-relativity

> **Comments:**
> **username_1**: It seems like the answer is in your first sentence. Both objects originated at the same point in "time". To address the second part: introducing new matter into the universe would violate the law of conservation of energy. You would of course be right to object that the big bang introduced new matter and energy into the universe, but that period in history is still not well understood - though many have, and still are, trying.  
> **username_0**: @username_1 It depends on your perspective on the universe. I believe "our" universe is simply the center of a black hole in a much older and larger universe. New energy can certainly be introduced into such a "sub universe", without violating the law of conservation of energy. You can of course argue that I'm not talking about the "grand universe" then - but for all intents and purposes we can't exit this black hole I believe we're inside. Thus, for us it will be the universe.  
> **username_1**: I would argue that you're talking about fringe science and any statements to that effect would be off-topic.  
> **username_1**: Apologies; looking back, that sounded overly snarky.  
> **username_0**: @username_1 There are many observed effects that I believe can be explained by such a "sub universe". For example accelerating universal expansion, isotropy of cosmic background radiation, big freeze seems a natural consequence,  
> **username_1**: It doesn't matter, this doesn't relate to the question. And how did you draw those conclusions?  
> **username_0**: @username_1 It seems obvious that at crossing the event horizon an object is "spaghettified" recursively until you're left with the tiniest of particles, or perhaps some energy/particle hybrid. Eventually that particle will reach the center of the singularity, and the spaghetification will be working internally on the particle more than externally. This will look like universal shrinking, which I believe is indistinguishable from an accelerating universal expansion - leading to a big freeze. In any direction, you're looking at the center of the black hole we originally entered - leading to CBR.  
> **username_0**: Finally; I fully adopt the notion that time and space is exactly the same. This implies that also physical distance is four dimensional, allowing us to observe particles as not being at the same "spot" i.e. have a physical shape - while another observer may see it as a singularity.  
> **username_1**: This makes no sense, and all stems from the theory that we're all inside a black hole.  
> **username_1**: Incidentally - and rather ironically - see this question: http://astronomy.stackexchange.com/questions/6305/is-it-possible-that-a-ultra-large-portion-of-the-space-we-live-in-is-already-ins. I think this supports my point.  

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## 1 answers

### Answer by username_2 on 2014-08-28. Score: 2

Particles are generated and destroyed all the time. This is obvious for photons, but also holds for massive particles. Today most particles are stable and long-living, but shortly after the big bang the universe was so hot that particle generation and destruction were in some equlibrium and *all* particles participated in this process (for photons this continued until the epoch of re-ionisation at redshift $z\sim1000$. There is definitely no particle around today that existed all the time since $t=0$.


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