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Warp escreveu:
> nemesis <nam### [at] gmail com> wrote:
>> wrong newsgroups. Try sci.astro and have old wolves devour your idea.
>
> There's no sci.astro in this news server, and questions about
> astrophysics have been presented here before, so it's not like it's
> something unheard of... :P
But you're just asking the wrong specialists. Most of your answers will
be of the kind "dunno" or "beats me"... :p Mine: "WTF?"
You should get more meaningful answers there:
https://groups.google.com/group/sci.astro
--
a game sig: http://tinyurl.com/d3rxz9
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Warp wrote:
> This has puzzled me for a while, and I can't find an answer.
>
> There was a time during the beginning of the Universe, when all the
> energy in the Universe was compressed into a space smaller than its own
> Schwarzschild radius. This should mean that this energy could not escape
> that radius, and would have quickly collapsed back into a singularity
> (or whatever is happening inside a black hole). However, that didn't
> happen. Why? How did all the energy escape its own event horizon?
Possibly one of these answers:
1) Because gravity wasn't a separate force from the others.
(OK, I see that gravity fell out very early on, but particles had no mass
anyway. I don't know if they mean rest mass, but...)
http://en.wikipedia.org/wiki/Grand_unification_epoch
2) It never did, and that's why the universe is close to flat. (I.e., we're
still inside the event horizon of the big bang.)
3) Because the big bang didn't start all in the same "place".
(This one apparently has been OBE, but it used to be postulated that
> In the beginning, however, the Universe expanded *a lot* faster.
That too. Look up "inflation". That's exactly what happened.
http://en.wikipedia.org/wiki/Inflation_%28cosmology%29
> Gravity, on the other hand, can only propagate at speed c because it's
> also bound by the same law as any particle. Thus because the Universe was
> expanding way faster than c, the gravity wave which all the energy was
> producing was lagging behind. Thus the gravity well necessary for the event
> horizon to form did simply not have time to propagate fast enough to
> "enclose" the energy existing at that point. Thus an event horizon never
> formed, and all the energy got distributed beyond its Schwarzschild radius.
That's what this picture is all about:
http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation
Basically, the "dots" are how far light would have traveled in the time
between the time the universe became cool enough to be transparent and now.
> I wonder if this explanation is even close to correct.
It's not bad, as I understand it. :-) It certainly has a lot of the pieces
right. It's probably close enough that someone who actually knows the answer
could explain it to you without your head exploding.
But I suspect it's the giant FTL "inflation" or some other wonkiness of
pre-first-microsecond space-time that means the "singularity" wasn't all
that singular.
--
Darren New, San Diego CA, USA (PST)
Serving Suggestion:
"Don't serve this any more. It's awful."
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Le 18/11/2010 18:13, Darren New nous fit lire :
> Warp wrote:
>> This has puzzled me for a while, and I can't find an answer.
>>
>> There was a time during the beginning of the Universe,
>
> Possibly one of these answers:
You forget: Was there a beginning of the Universe ?
It's not because there is a road that can be followed that there is a
start of the road.
So far they have theory about the very first "instant" of the Universe,
yet, nothing about the initial setting and before.. (if that can even
make sense)
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Le_Forgeron <jgr### [at] freefr> wrote:
> Le 18/11/2010 18:13, Darren New nous fit lire :
> > Warp wrote:
> >> This has puzzled me for a while, and I can't find an answer.
> >>
> >> There was a time during the beginning of the Universe,
> >
> > Possibly one of these answers:
> You forget: Was there a beginning of the Universe ?
> It's not because there is a road that can be followed that there is a
> start of the road.
> So far they have theory about the very first "instant" of the Universe,
> yet, nothing about the initial setting and before.. (if that can even
> make sense)
Well, my question was not about time zero, when the initial singularity
(or whatever it was that was there) started expanding, or the ultimate
question of where did everything come from. I was just asking about moments
after the expansion started. After all, the Universe was smaller than the
Schwarzschild radius of all the energy in the Universe for a "significant"
amount of time after the start. (Of course "significant" relatively speaking.
I have no idea whatsoever what kind of timescale we are talking about, but
wouldn't be surprised if it was measured in nanoseconds or the like.)
--
- Warp
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Darren New <dne### [at] sanrrcom> wrote:
> 2) It never did, and that's why the universe is close to flat. (I.e., we're
> still inside the event horizon of the big bang.)
I have never quite understood that hypothesis, for at least two reasons:
1) Spacetime inside an event horizon is pretty weird, and the spacetime
we currently reside in isn't (relatively speaking, at least).
2) All spacetime geodesics inside an even horizon point towards the
singularity. (Ok, in a rotating black hole it's more complicated than
that, but in principle I suppose it's the same.) We are not moving towards
a singularity; we are expanding, hence moving *away* from any possible
"central point" of the Universe. That kind of contradicts the idea.
Of course I am no physicist, and I have zero knowledge of the GR
equations, so I could be completely off track with this. My point is,
however, that I just don't understand how that hypothesis could be even
worthy of consideration.
> But I suspect it's the giant FTL "inflation" or some other wonkiness of
> pre-first-microsecond space-time that means the "singularity" wasn't all
> that singular.
I have read somewhere that it's considered that even if the entire
Universe was concentrated in a singularity at the beginning, it's hard
to say anything about its nature because anything prior to the first
unit of planck time did not obey any current laws of nature (in other
words, laws of nature break up when we go back in time more than one
planck time unit after it all started).
--
- Warp
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On 18-11-2010 16:53, Warp wrote:
> This has puzzled me for a while, and I can't find an answer.
have you tried google?
E.g. for "schwarzschild radius universe" some answers, not sure if the
are correct and I even don't understand some of those (not necessary in
that order).
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Warp <war### [at] tagpovrayorg> wrote:
>
> I have read somewhere that it's considered that even if the entire
> Universe was concentrated in a singularity at the beginning, it's hard
> to say anything about its nature because anything prior to the first
> unit of planck time did not obey any current laws of nature (in other
> words, laws of nature break up when we go back in time more than one
> planck time unit after it all started).
>
I think that's the fundamental limiting factor as to how (if ever) we will ever
understand 'the beginning.' Most cosmological theories I've read about limit
themselves to the period 'immediately following' the genesis of the
universe--something like 1^-43 second afterward. In fact, AFAIK, it's *at* the
point of singularity where Einstein's gravity equations break down (as well as
who-knows-what else); until an answer can be found to that little conundrum,
we're essentially searching in the dark.
Of course, any and all science is built upon basic tenets; in the case of
cosmology, it would seem to be 1) the red-shift/distance relationship, and 2)
that most physical processes (including time and gravitational force) haven't
changed their 'qualities' over the course of the previous billions of years. But
what if these aspects of nature *have* changed? (I've read that very precise
tests have actually been done to see if some of these qualities change or not
with the passage of time; so far, no important changes have been seen--but how,
for example, does one actually measure a change in the passage of time itself?)
Cosmology is a fascinating subject that I find myself thinking about all the
time--as a layman, of course ;-) What fundementally bothers me about current
theories is that, we as humans may not have evolved sufficient intelligence to
truly understand what's going on. My own feeling is that we are still
cave-dwellers, in a manner of speaking, scratching pictures on cave walls in an
attempt to understand the most profound questions of nature. Sure, mathematics
(as a language of logic) is currently our tool of choice; but it all makes me
wonder if we are, in fact, using the correct 'language' to do so. (Not that I
have any alternative idea!) Perhaps something like, sqrt(Christmas tree)/pow(my
mother's mustache, pi) = the 'true' nature of gravity ;-P
The history of science is full of examples of scientific theories that seemed
correct *at the time* (because they more-or-less agreed with observation and
experiment.) But better theories always come along, which relegate old theories
to the dustbin (or else build a better framework upon them.) Perhaps the Large
Hadron Collider at Cern will clarify some things about the fundamental nature of
matter--but I have a feeling it will produce more questions than answers. Every
time we go looking deeper into the mysteries of nature, we come up with more
mysteries. Which, of course, is how science progresses!
Ken
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Warp wrote:
>> You forget: Was there a beginning of the Universe ?
Yes, there was. :-) There might not have been anything *before* that, but
there was definitely a beginning, according to all modern theories and lots
of evidence.
> After all, the Universe was smaller than the
> Schwarzschild radius of all the energy in the Universe for a "significant"
> amount of time after the start. (Of course "significant" relatively speaking.
I'm wondering if the fact that baryogenesis happened well after inflation
had anything to do with it. Basically, there wasn't any mass until after the
universe was big enough?
> I have no idea whatsoever what kind of timescale we are talking about, but
> wouldn't be surprised if it was measured in nanoseconds or the like.)
http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang
10^-32 seconds after the start, you're done the FTL expansion phase.
--
Darren New, San Diego CA, USA (PST)
Serving Suggestion:
"Don't serve this any more. It's awful."
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Warp wrote:
> 1) Spacetime inside an event horizon is pretty weird, and the spacetime
> we currently reside in isn't (relatively speaking, at least).
It's only weird if the event horizon is small. A galaxy-sized black hole,
you could fall into and not notice. And it's not like you can get outside
the event horizon of the universe.
> 2) All spacetime geodesics inside an even horizon point towards the
> singularity. (Ok, in a rotating black hole it's more complicated than
> that, but in principle I suppose it's the same.) We are not moving towards
> a singularity; we are expanding, hence moving *away* from any possible
> "central point" of the Universe. That kind of contradicts the idea.
Unless there'a big crunch? :-)
> Of course I am no physicist, and I have zero knowledge of the GR
> equations, so I could be completely off track with this. My point is,
> however, that I just don't understand how that hypothesis could be even
> worthy of consideration.
I think it was more popular before people found dark energy and thought we
were heading for a "big crunch" or something?
>> But I suspect it's the giant FTL "inflation" or some other wonkiness of
>> pre-first-microsecond space-time that means the "singularity" wasn't all
>> that singular.
>
> I have read somewhere that it's considered that even if the entire
> Universe was concentrated in a singularity at the beginning, it's hard
> to say anything about its nature because anything prior to the first
> unit of planck time did not obey any current laws of nature (in other
> words, laws of nature break up when we go back in time more than one
> planck time unit after it all started).
Basically, yes. Plank time and plank length are the quantums of quantum
mechanics, so there *isn't* anything smaller than that. It's like asking for
half a bit of information.
--
Darren New, San Diego CA, USA (PST)
Serving Suggestion:
"Don't serve this any more. It's awful."
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Warp <war### [at] tagpovrayorg> wrote:
> At the beginning the Universe expanded much more rapidly than c
> (and in fact, that's still happening today). This is not against general
> relativity, as it fully allows this... [etc.]
Something I've always wondered about (and which I've never been able to find an
answer to, in any layman's science book) is this: If space expands (not just the
space *between* objects, but space itself), then at what scale, what microscopic
level, does this process cease? If at all? In other words, does the *relatively*
vast space inside an atom itself--between the nucleus and its electrons--also
expand? If it does, then, since essentially *everything* expands equally, how is
the 'expansion of space' to be measured? (Other than, "Space must be expanding
because the cosmological red-shift relationship shows that it's happening." Or,
"because Einstein's equations say so.")
I find that every time I read about this particular subject, the explanation
seems to be different than the *previous* explanation I've read. :-/ One
particularly vexing explanation is this one (which seems kind of dubious): That
the space between galaxy *clusters* expands, but the space between the galaxies
*in* the cluster doesn't--"because local gravity effects overwhelm the greater
cosmic expansion." That may well be true--from a simple observational
standpoint--but it's no real answer to the more basic question, IMHO.
Ken
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