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?

  After much deliberation I have come up with a wild hypothesis which,
as a complete layman in physics, I have no idea if it's even close to
correct and the actual explanation:

  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 (and in fact it's one of its
predictions). In GR the distance between two points in space (and thus
the distance between two particles) *can* increase arbitarily faster
than c (what GR forbids is a particle *traveling* between the two
points faster than c, which is a completely different thing). In fact,
the Universe is, it seems, even today expanding faster than c, which is
why the observable Universe is smaller than the whole Universe in existence.
In the beginning, however, the Universe expanded *a lot* faster.

  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.

  I wonder if this explanation is even close to correct.

-- 
                                                          - Warp

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Warp escreveu:
>   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?
> 
>   After much deliberation I have come up with a wild hypothesis which,
> as a complete layman in physics, I have no idea if it's even close to
> correct and the actual explanation:

wrong newsgroups.  Try sci.astro and have old wolves devour your idea.

-- 
a game sig: http://tinyurl.com/d3rxz9

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nemesis <nam### [at] gmailcom> 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

-- 
                                                          - Warp

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Warp escreveu:
> nemesis <nam### [at] gmailcom> 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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Kenneth wrote:
> In other words, does the *relatively*
> vast space inside an atom itself--between the nucleus and its electrons--also
> expand? 

Sure. But then the electrons move closer to the nucleus again.

The math of quantum mechanics all works only if you assume quarks and 
electrons and photons are all mathematical points. So the electrons 
themselves don't expand.

> 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.

Because space expands slowly enough that the stars will fall back together 
again faster than the space is expanding, is what I think they're saying.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:

>
> 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?
>

But energy and mass are equivalent--E=MC^2 and all that--so even before baryonic
matter 'arrived', wouldn't the raw energy content of the universe have exerted
gravity as well? Assuming the laws of nature were the same then (which, upon
further thought, might be a rather large assumption IMO.)

Ken

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Darren New <dne### [at] sanrrcom> wrote:
> Kenneth wrote:
> > In other words, does the *relatively*
> > vast space inside an atom itself--between the nucleus and its electrons--also
> > expand?
>
> Sure. But then the electrons move closer to the nucleus again.

Hmm, don't understand that. You mean, because of the 'set' attractive/repulsive
forces between electrons and nucleus? If so, very interesting--I hadn't thought
of that before. It *would* seem to keep the atom at the same size, regardless of
space expansion. And all of the atom's internal workings the same as well, since
the relative charges and distances haven't changed.
>
> The math of quantum mechanics all works only if you assume quarks and
> electrons and photons are all mathematical points. So the electrons
> themselves don't expand.

Agreed. (The idea of 'point-like' masses--with no spatial extension--is itself a
strange one!)

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Kenneth wrote:
> further thought, might be a rather large assumption IMO.)

I think that's the whole point of the quest for the Higgs, which is the 
particle that imparts mass to matter and energy.  That's why you need 
something awesomely powerful to create it.  Or something like that.

So, yeah, I think it's unclear (certainly to me) at what point general 
relativity kicked in. :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Kenneth wrote:
> Hmm, don't understand that. You mean, because of the 'set' attractive/repulsive
> forces between electrons and nucleus?

I think you're going way beyond what I know. But I'm happy to BS for a 
while. ;-)

Electrons like to be a certain size, as provided for in their wavelength. 
(and by "size" I refer to the amplitude (i.e., probability) cloud.)  So you 
can add a tiny bit of space, and the electron will "shrink" in return, just 
like if you had two balls with a spring between them and you slowly slid the 
two halves of the floor apart, the spring would pull the balls back together.

OK, I'm officially not knowing what I'm talking about. But that's what I 
understood - the mutual attractions between things close enough that the 
expansion of space in the middle (gravity or QED) is what holds smaller 
things together even as the bigger things spread apart.

> Agreed. (The idea of 'point-like' masses--with no spatial extension--is itself a
> strange one!)

Well, that's why I clarified that's what the *math* says. Who knows the 
"reality" of it?

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:
> Kenneth wrote:
> > Hmm, don't understand that. You mean, because of the 'set'
> > attractive/repulsive forces between electrons and nucleus?
>
> I think you're going way beyond what I know. But I'm happy to BS for a
> while. ;-)

Yes, cosmological B.S'ing is FUN!! (Much of what passes for current cosmological
theorizing by 'the experts' seems to me to be so much arcane B.S.--but that's
just me...)

The idea I had (which you kindled) was rather basic: If atomic forces remain
unchanging as intra-atom space expands, and if neutrons/protons/electrons remain
their same sizes too (points!), then it seems logical that the
attraction/repulsion forces at play would keep the atom the 'same size',
regardless of any expansion of space. (Assuming that the forces themselves don't
diminish as space expands.) Or something like that ;-)
>

> OK, I'm officially not knowing what I'm talking about. But that's what I
> understood - the mutual attractions between things close enough that the
> expansion of space in the middle (gravity or QED) is what holds smaller
> things together even as the bigger things spread apart.

I need to read more about that--sounds suitably cool and interesting, and new to
me. I think you had mentioned something similar in a previous post, which piqued
my interest at the time.

One of my own 'heroes of science' is Michael Faraday. Here was a rather typical
guy, no 'scientist' in any academic sense, with no advanced math training (or
any at all??), who nevertheless, by virtue of sheer *curiosity* and a good
experimental bent, came up with fundamental thoughts on electromagnetism--that
no one else before him had even imagined. There are probably thousands like him
in the world today--most of whom, with no scientific 'credentials,' will
probably never be heard from. But it certainly makes me wonder if seemingly
crackpot ideas by non-experts may, in fact, hold the key to the true
understanding of nature. Alas, it was probably easier (and more fruitful) being
a scientist in Faraday's time; practically *any* learned person could be a
natural philosopher, as there was no specialization then--and there were so
*many* things yet undiscovered.

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Kenneth wrote:
> a scientist in Faraday's time; practically *any* learned person could be a
> natural philosopher, as there was no specialization then--

I have read that Leonardo da Vinci was the last human to know essentially 
everything of importance. :-)

 > and there were so *many* things yet undiscovered.

I'm starting to feel the same way about computers. There's very few fields 
where an individual can really invent something useful without knowing how 
to scale it to run on hundreds of computers.

Smart phone apps and games seem the last bastion of where you can invent 
something by yourself and be a success.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:
> 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.

  I have hard time believing that. Space is extremely warped close to the
event horizon of a black hole. For example, at an altitude (from the central
singularity) of 3/2 of the Schwarzschild radius there exists the so-called
photon sphere: This is an area around the black hole where a photon could
orbit the black hole if it was traversing perfectly parallel to the "surface"
of the event horizon. If you were at that distance from the black hole,
it would look like the event horizon is a plane that occupies half of the
Universe. That's how warped the space is close to the event horizon.

  If you get closer to the event horizon than that, the event horizon will
look like it's curling up, engulfing you, and the rest of the Universe
would look like it would get compressed into an ever-shrinking circle
directly above. (When the circle shrinks to zero size, it means you have
touched the event horizon and are forever doomed. From this point forward
every direction points to the singularity. It's like the singularity would
surround you from all sides.)

  And this is completely independently of how big the black hole is.

  If the black hole is rotating (as most/all of them are assume to be),
it gets even weirder. There are now (AFAIR) two photons spheres of
different shapes, and additionally there's a space outside the event
horizon called an ergosphere which has weird physical properties. If
you get inside this ergosphere you will be dragged at a velocity larger
than c (relative to the rest of the Universe) around the black hole, so
I'm assuming it would look really, really weird.

  So I really don't buy the whole "you wouldn't even notice crossing the
event horizon". Maybe if you are completely blinded, you wouldn't (I really
don't know if there are any physical consequences of being close to the
event horizon of a very large black hole).

>  And it's not like you can get outside 
> the event horizon of the universe.

  Since the Universe is expanding faster than c, there's a so-called
cosmological horizon which limits the size of the observable Universe
(observable to us, of course; the observable Universe would naturally
be different in an alien planet on the other side of the Universe).

  However, this horizon is caused by the expansion of the Universe, not
by gravity, and it's always relative to where the observer is to begin
with.

> >   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? :-)

  Current observations seem to indicate that there won't be.

> >   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?

  I think the word "found" is wrong here. It hasn't been measured; it's a
hypothesis. (It could perfectly well be the *correct* hypothesis, but until
it's measured it's just that.)

-- 
                                                          - Warp

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Kenneth <kdw### [at] earthlinknet> wrote:
> 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?

  IIRC the Universe only expands (ie. new space is formed) at intergalactic
space, not inside galaxies. The gravity of galaxies is high enough to stop
(or at least greatly diminish) expansion from happening inside them.

> If it does, then, since essentially *everything* expands equally

  Everything does *not* expand equally. Gravity works against the expansion,
slowing it down (if not even stopping it completely), AFAIK.

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:

>   IIRC the Universe only expands (ie. new space is formed) at intergalactic
> space, not inside galaxies. The gravity of galaxies is high enough to stop
> (or at least greatly diminish) expansion from happening inside them.
> [clip]
> Everything does *not* expand equally. Gravity works against the expansion,
> slowing it down (if not even stopping it completely), AFAIK.
>

So in other words, local gravity effects actually keep local *space* from
expanding? If so, that's a new concept for me; I thought space itself--whatever
it actually *is* ;-) --was sort of 'independent' of gravity, expanding at its
own independent pace, as its own 'entity.' Although, now that I think of it,
"gravity warps space," so what you say isn't so weird after all. Geez, that's
always been a difficult concept to grasp. But is 'new space' actually formed? Or
is it just 'stretched' (whatever *that* concept means)?

Ken

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Warp <war### [at] tagpovrayorg> wrote:

> > I think it was more popular before people found dark energy and thought we
> > were heading for a "big crunch" or something?
>
>   I think the word "found" is wrong here. It hasn't been measured; it's a
> hypothesis. (It could perfectly well be the *correct* hypothesis, but until
> it's measured it's just that.)

Yeah; AFAIU it, 'dark matter' and 'dark energy' are somewhat ad-hoc
postulates--there was a 'hole' in the current cosmological model for awhile,
where certain observations about the universe just didn't match the model; hence
*something* must be missing from it (if it's to better match the observations.)
DM and DA would fill that hole; but whether they truly exist or not is another
matter. The observed effects could be something else entirely, something even
stranger (IMO).

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On 11/18/2010 12:13 PM, Darren New wrote:

> (OK, I see that gravity fell out very early on...)

Gravity, having fallen out in early childhood from its siblings Strong, 
Weak, and the twins Electro and Magneto, remains estranged to this day.

Regards,
John

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Warp wrote:
>   I have hard time believing that. 

It's just what I've heard. Maybe you wouldn't notice the tides if you didn't 
look out the window, is what they meant. (I think I heard it from Sagan or 
Asimov or something like that.)

Your argument is good, tho. Thinking on it, I can't imagine how you wouldn't 
notice. :-)

>   However, this horizon is caused by the expansion of the Universe, not
> by gravity, and it's always relative to where the observer is to begin
> with.

I was talking about overall.  (You may be taking me too seriously. :-)

>> I think it was more popular before people found dark energy and thought we 
>> were heading for a "big crunch" or something?
> 
>   I think the word "found" is wrong here. It hasn't been measured; it's a
> hypothesis. (It could perfectly well be the *correct* hypothesis, but until
> it's measured it's just that.)

For "found" read "found the affects attributed to..."

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Kenneth wrote:
> DM and DA would fill that hole; but whether they truly exist or not is another
> matter. The observed effects could be something else entirely, something even
> stranger (IMO).


Well, there's really convincing evidence for DM, at least. They found two 
galaxies that had crashed together, and the stars were all jumbled up in the 
middle, but the Dark Matter kept going (as indicated by gravitational 
lensing from the DM).

Oh, there it is.  http://www.abc.net.au/science/news/stories/s1720848.htm


-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
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Warp wrote:
>   IIRC the Universe only expands (ie. new space is formed) at intergalactic
> space, not inside galaxies. The gravity of galaxies is high enough to stop
> (or at least greatly diminish) expansion from happening inside them.

FWIW, that's not what I've heard. However, I'm not sure anyone actually 
knows the answer there. :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   IIRC the Universe only expands (ie. new space is formed) at intergalactic
> > space, not inside galaxies. The gravity of galaxies is high enough to stop
> > (or at least greatly diminish) expansion from happening inside them.

> FWIW, that's not what I've heard. However, I'm not sure anyone actually 
> knows the answer there. :-)

  Thinking about it, I can think of one argument of why that would be so:
If space was expanding evenly everywhere, it would mean that there should
be an extra "force" pulling planets away from the Sun, and an even "stronger
force" pulling stars away from thir galaxy's center, and this extra "pulling"
factor would have to be taken into account in orbit equations. But is it?

  (OTOH maybe the expansion inside our solar system is so minuscule that
it basically unnoticeable and doesn't affect orbits in practice...)

  Wikipedia (the always trustworthy source) seems to confirm this idea.
For example at http://en.wikipedia.org/wiki/Metric_expansion_of_space it
says:

"Metric expansion is a key feature of Big Bang cosmology and is
modeled mathematically with the FLRW metric. This model is valid in
the present era only at relatively large scales (roughly the scale of
galactic superclusters and above). At smaller scales matter has
clumped together under the influence of gravitational attraction and
these clumps do not individually expand, though they continue to
recede from one another."

"In addition to slowing the overall expansion, gravity causes local
clumping of matter into stars and galaxies. These stars and galaxies
do not subsequently expand, there being no force compelling them to do
so."

"However the only locally visible effect of the accelerating expansion
is the disappearance (by runaway redshift) of distant galaxies;
gravitationally bound objects like the Milky Way do not expand."

  The page http://en.wikipedia.org/wiki/Hubble%27s_law could perhaps have
more on this, but I can't easily find anything to corroborate either claim,
except perhaps for:

"In systems that are gravitationally bound, such as galaxies or our
planetary system, the expansion of space is a much weaker effect than
the attractive force of gravity."

-- 
                                                          - Warp

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nemesis <nam### [at] gmailcom> wrote:
> Try sci.astro and have old wolves devour your idea.

  I'm reading some of the latest posts there. Over half of the posts are
spam (*sigh*, I still remember the time in the mid-90's when there was
virtually *no* spam in usenet, as incredible as that might sound today)
and most of the rest seems to consist of pseudoscientists writing miles-long
essays on their newest fads and denigrating established theories and known
scientists.

  I'm guessing that if I posted there, nobody would actually answer my
question and instead I would get a few totally useless "the Big Bang
theory is BS" replies.

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:
> nemesis <nam### [at] gmailcom> wrote:
> > Try sci.astro and have old wolves devour your idea.
>
>   I'm reading some of the latest posts there. Over half of the posts are
> spam (*sigh*, I still remember the time in the mid-90's when there was
> virtually *no* spam in usenet, as incredible as that might sound today)
> and most of the rest seems to consist of pseudoscientists writing miles-long
> essays on their newest fads and denigrating established theories and known
> scientists.
>
>   I'm guessing that if I posted there, nobody would actually answer my
> question and instead I would get a few totally useless "the Big Bang
> theory is BS" replies.

yes, lots of loonies (and spam) there.  Still, those are rapidly torn apart by
actual astrophysicists or wannabes with quite some knowledge.  Some interesting
discussions follow from time to time...

sci.astro is much better than alt.astronomy BTW. ;)

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Warp wrote:
> "In systems that are gravitationally bound, such as galaxies or our
> planetary system, the expansion of space is a much weaker effect than
> the attractive force of gravity."

Yeah, I was interpreting that kind of statement as "gravity holds things 
together in spite of the expansion of space trying to pull them apart." On 
the other hand, it could be that the "dark energy" (i.e. vacuum energy) or 
expansion of space or whatever is actually suppressed (in some sense) by the 
presence of normal energy or the presence of curved space.  I don't know at 
this point any more.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> > "In systems that are gravitationally bound, such as galaxies or our
> > planetary system, the expansion of space is a much weaker effect than
> > the attractive force of gravity."

> Yeah, I was interpreting that kind of statement as "gravity holds things 
> together in spite of the expansion of space trying to pull them apart." On 
> the other hand, it could be that the "dark energy" (i.e. vacuum energy) or 
> expansion of space or whatever is actually suppressed (in some sense) by the 
> presence of normal energy or the presence of curved space.  I don't know at 
> this point any more.

  Has it even been hypothesized *why* the expansion of the universe
happens? Or is it just another one of those "it just happens, we don't
really know why" things?

-- 
                                                          - Warp

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Warp wrote:
>   Has it even been hypothesized *why* the expansion of the universe
> happens? 

Dark Energy!  ;-)

Seriously, I think they think it has something to do with zero-point energy, 
i.e., the fact that virtual particles will spontaneously come into existence 
and then annihilate each other again.  I can't really say I understand it 
beyond "it's something about quantum" (as Terry Pratchett would say)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:
> Seriously, I think they think it has something to do with zero-point energy, 
> i.e., the fact that virtual particles will spontaneously come into existence 
> and then annihilate each other again.  I can't really say I understand it 
> beyond "it's something about quantum" (as Terry Pratchett would say)

  Even if that explains the current expansions, would it explain the
initial rapid inflation?

  Seemingly not, as there appears to be a hypothesis for a different particle
that caused the cosmic inflation: http://en.wikipedia.org/wiki/Inflaton

  I don't understand, however, how a particle would explain inflation
(or just the "normal" expansion of the universe), because such a particle
should be bound to the maximum speed limit of c, as any other particle.
How can it cause the universe to expand faster than c?

-- 
                                                          - Warp

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Seriously, I think they think it has something to do with zero-point energy, 
>> i.e., the fact that virtual particles will spontaneously come into existence 
>> and then annihilate each other again.  I can't really say I understand it 
>> beyond "it's something about quantum" (as Terry Pratchett would say)
> 
>   Even if that explains the current expansions, would it explain the
> initial rapid inflation?

I don't think so, no. Certainly not if the whole quantum mess didn't even 
start until after inflation. (I hadn't realized that "inflation" actually 
happened that early and quickly until this conversation.)

>   Seemingly not, as there appears to be a hypothesis for a different particle
> that caused the cosmic inflation: http://en.wikipedia.org/wiki/Inflaton

Damn. Inflation ended when the universe was only one meter across? Yow.

> How can it cause the universe to expand faster than c?

Only if the actual energy turned into space, or something? I have nothing 
buy BS guesses for that. :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Darren New <dne### [at] sanrrcom> wrote:
> >   Seemingly not, as there appears to be a hypothesis for a different particle
> > that caused the cosmic inflation: http://en.wikipedia.org/wiki/Inflaton

> Damn. Inflation ended when the universe was only one meter across? Yow.

  I'm not sure it says that. It says how long it took for the universe
to become 1 meter accross, not that the inflation ended there. (Also this
seems to completely lack a reference, so it could be some editor's BS.)

-- 
                                                          - Warp

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>>>   Seemingly not, as there appears to be a hypothesis for a different particle
>>> that caused the cosmic inflation: http://en.wikipedia.org/wiki/Inflaton
> 
>> Damn. Inflation ended when the universe was only one meter across? Yow.
> 
>   I'm not sure it says that. It says how long it took for the universe
> to become 1 meter accross, not that the inflation ended there. (Also this
> seems to completely lack a reference, so it could be some editor's BS.)
> 

Good point.  http://en.wikipedia.org/wiki/Early_universe#Inflationary_epoch
implies it ended somewhere around 10^-32

http://en.wikipedia.org/wiki/Inflationary_epoch

And of course, they say "then the universe filled up with energy that came 
from potential energy."  I don't know how you store potential energy in a 
"field", so it's either way over my head, or BS. :-)

-- 
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http://io9.com/5694701/does-cosmic-background-radiation-reveal-the-universe-before-the-big-bang

Actually, I think it's clear nobody really has a clue. :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Am 21.11.2010 04:12, schrieb Darren New:
>
>
http://io9.com/5694701/does-cosmic-background-radiation-reveal-the-universe-before-the-big-bang
>
>
> Actually, I think it's clear nobody really has a clue. :-)

And AC said, "LET THERE BE LIGHT!"
And there was light--

Isaac Asimov, "The Last Question"
(http://www.multivax.com/last_question.html)

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Ok, another physics question. Not related to the Big Bang, but I didn't
want to create a new thread.

  It seems that a black hole can be characterized by three (and only three)
quantities: its mass, angular momentum and electric charge. For example the
Reissner-Nordstr?m metric is a solution to the general relativity equations
for a charged, non-rotating black hole.

  I don't understand. Electric charge is mediated by photons. Photons cannot
escape a black hole. How can they mediate anything in this case? A black
hole swallows photons, it doesn't exchange them with anything.

-- 
                                                          - Warp

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And lo On Thu, 18 Nov 2010 15:53:38 -0000, Warp <war### [at] tagpovrayorg> did  
spake thusly:

>   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.

As an aside to some the Big Bang theory is being dropped or at least the  
part where it derives from a singularity is.

There's inflationary theory (or theories) by which a quantum fluctuation  
inflates.

String theory (or the over-riding M-theory) whereby any attempt to  
compress an object beyond the Planck length will result in it expanding.

and Brane theory in which our universe is caused by either a collision or  
merging of two (or more) multi-dimensional 'sheets'.

All remove the need for a singularity.

As for your initial question, the calculations for the Schwarzschild  
radius don't apply to a rapidly expanding mass. As you put it the  
expansion out-runs the gravitational curve.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

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Le 23/11/2010 13:54, Phil Cook v2 a écrit :
> As you put it the expansion out-runs the gravitational curve.

I'm just nuts, and 10 cards short of full deck.


It seems gravitation has always been considered as "attraction between 2
objetcs".

What if, instead, it was just the universe which was repelling, and the
"mass" of the other object was in fact a shield against that repulsion.
(the more energy in the shield, the more protection it provide. and it
is just fine with delta-e=delta-m.c², but as a shield it only divert the
repelling flux: none get created, none get destroyed)

Remember the old joke: Gravity is a myth, the Earth sucks.

Well, in fact, it's just the universe which is blowing instead.

Gravity is a myth, the sky is pressuring you down!

Hence there is no graviton to find for the "fifth" force.
It's just made up from the known ones (the 4 united...)

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Le_Forgeron wrote:
> What if, instead, it was just the universe which was repelling, and the
> "mass" of the other object was in fact a shield against that repulsion.

Already considered and tested. You would weigh less on the "back" of the 
earth than the "front" because the earth was blocking repulsion particles 
that are assumedly not moving along with the earth in its orbit.

Also, the "everything is expanding, so if you jump you don't fall but rather 
the earth and your feet expand towards each other" theory can be trivially 
disproven as well.

> Hence there is no graviton to find for the "fifth" force.
> It's just made up from the known ones (the 4 united...)

I'm pretty sure gravity is one of four, not five. :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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On 23-11-2010 17:12, Darren New wrote:
> Le_Forgeron wrote:
>> What if, instead, it was just the universe which was repelling, and the
>> "mass" of the other object was in fact a shield against that repulsion.
>
> Already considered and tested. You would weigh less on the "back" of the
> earth than the "front" because the earth was blocking repulsion
> particles that are assumedly not moving along with the earth in its orbit.
>
> Also, the "everything is expanding, so if you jump you don't fall but
> rather the earth and your feet expand towards each other" theory can be
> trivially disproven as well.
>
>> Hence there is no graviton to find for the "fifth" force.
>> It's just made up from the known ones (the 4 united...)
>
> I'm pretty sure gravity is one of four, not five. :-)
>

The one who left before they became famous.

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Le_Forgeron <lef### [at] freefr> wrote:
> It seems gravitation has always been considered as "attraction between 2
> objetcs".

  Actually since about 1915 gravitation has been considered a side-effect
of the geometry of spacetime.

-- 
                                                          - Warp

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On 23/11/2010 4:29 PM, andrel wrote:
>> I'm pretty sure gravity is one of four, not five. :-)
>>
>
> The one who left before they became famous.

LOL

-- 
Regards
     Stephen

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On 23/11/2010 12:54 PM, Phil Cook v2 wrote:
> As an aside

As an aside to your aside:

http://www.bbc.co.uk/news/science-environment-11837869


-- 
Regards
     Stephen

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> It seems gravitation has always been considered as "attraction between 2
> objetcs".
>
> What if, instead, it was just the universe which was repelling, and the
> "mass" of the other object was in fact a shield against that repulsion.

The most intriguing thing for me is the speeds of stars relative to the 
centre of the galaxy, they don't follow the expected pattern by simply 
solving the math for orbits:

http://en.wikipedia.org/wiki/Dark_matter_halo

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scott wrote:
> http://en.wikipedia.org/wiki/Dark_matter_halo

"either the halo is composed of weakly-interacting elementary particles 
known as WIMPs, or it is home to large numbers of small, dark bodies known 
as MACHOs."

I really think the scientists need to knock this sort of stuff off. 500 
years from now, people will still be using these names.

For a fun fictional take on the problem, check out Robert Sawyer's 
"StarPlex" novel. :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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