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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] tag povrayorg> 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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