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OT: Re: Is Space Really Empty
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David Spain
Dec 17, 2012, 4:08:03 PM12/17/12
to
On 11/16/2012 10:52 AM, h v mohanlal wrote:
> Space is supposed be a perfect vacuum and that is the reason why all
> heavenly bodies are in perpetual motion by orbiting one or the other
> bodies. In a perfect vacuum there is absolutely no friction. The only
> objects that do not seem to orbit are the super massive Black-Holes at
> the center of all galaxies.
>
Well not really. Space-time at the margins can be quite odd.
For example, at the edge of the event horizon of a black hole, "a
virtual particle" can instantaneously pop into existence when its
"virtual twin" falls into the hole.
At the distances or intervals shorter than the Plank distance/interval,
it is conjectured that Space-Time might actually disappear altogether,
churned up in a sort of "quantum foam".
BTW, even co-orbiting bodies will not do so forever. Eventually, even in
the "vacuum" of space given enough time they will collide. Even super
massive black holes are not immune from the influences their gravitation
can have on each other. However, the current conjecture is that it
appears the expansion of the Universe will out-run this collapse.
Leaving (I suppose) "universes" of singleton black holes that radiate
via Hawking radiation (see 1st paragraph above) back to ?
Dave
PS: This would be better posted in sci.space.science
> Space is supposed be a perfect vacuum and that is the reason why all
> heavenly bodies are in perpetual motion by orbiting one or the other
> bodies. In a perfect vacuum there is absolutely no friction. The only
> objects that do not seem to orbit are the super massive Black-Holes at
> the center of all galaxies.
>
Well not really. Space-time at the margins can be quite odd.
For example, at the edge of the event horizon of a black hole, "a
virtual particle" can instantaneously pop into existence when its
"virtual twin" falls into the hole.
At the distances or intervals shorter than the Plank distance/interval,
it is conjectured that Space-Time might actually disappear altogether,
churned up in a sort of "quantum foam".
BTW, even co-orbiting bodies will not do so forever. Eventually, even in
the "vacuum" of space given enough time they will collide. Even super
massive black holes are not immune from the influences their gravitation
can have on each other. However, the current conjecture is that it
appears the expansion of the Universe will out-run this collapse.
Leaving (I suppose) "universes" of singleton black holes that radiate
via Hawking radiation (see 1st paragraph above) back to ?
Dave
PS: This would be better posted in sci.space.science
Brian Gaff
Dec 20, 2012, 11:21:31 PM12/20/12
to
I think though we have to remember that much of this is only predicted by
theories and actually testing it out is hardly possible at the moment.
I think what many of us have problems coming to terms with is that space
is empty but is stretching, Obviously in this context empty merely means
that there is nothing that interacts strongly with the matter we see.
Brian
--
>From the Bed of Brian Gaff.
The email is valid as bri...@blueyonder.co.uk
Blind user.
"David Spain" <nos...@127.0.0.1> wrote in message
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theories and actually testing it out is hardly possible at the moment.
I think what many of us have problems coming to terms with is that space
is empty but is stretching, Obviously in this context empty merely means
that there is nothing that interacts strongly with the matter we see.
Brian
--
>From the Bed of Brian Gaff.
The email is valid as bri...@blueyonder.co.uk
Blind user.
"David Spain" <nos...@127.0.0.1> wrote in message
news:irudnXN16at3FVLN...@giganews.com...
David Spain
Jan 1, 2013, 1:25:23 AM1/1/13
to
On 12/20/2012 11:21 PM, Brian Gaff wrote:
> I think though we have to remember that much of this is only predicted by
> theories and actually testing it out is hardly possible at the moment.
> I think what many of us have problems coming to terms with is that space
> is empty but is stretching, Obviously in this context empty merely means
> that there is nothing that interacts strongly with the matter we see.
>
> Brian
>
If we run the clock forward fast enough and long enough on our current model of the universe the existence of matter becomes
> I think though we have to remember that much of this is only predicted by
> theories and actually testing it out is hardly possible at the moment.
> I think what many of us have problems coming to terms with is that space
> is empty but is stretching, Obviously in this context empty merely means
> that there is nothing that interacts strongly with the matter we see.
>
> Brian
>
impossible. The universe will simply run out of energy. Unless we conjecture that some kind of ultra super duper massive black hole
can radiate back to triggering another big bang on its own. Problem is there doesn't appear to be any way in the given model to
create such a beast. And the physics of singularities are indeterminate anyway.
To paraphrase from Dr. E: "God doesn't care about the end of the Universe and won't say why."
Dave
Brian Gaff
Feb 3, 2013, 3:26:14 PM2/3/13
to
So then, would the energy in the universe go negative making matter just fly
into its component parts as the negative energy overwhelms the current
forces. If so then where is all this energy coming from. As it cannot be
destroyed, I can see it can be very defuse but surely in order for matter to
stop existing there has to be something opposite or the current forces must
be diminishing.
Brian
--
>From the Bed of Brian Gaff.
The email is valid as bri...@blueyonder.co.uk
Blind user.
"David Spain" <nos...@127.0.0.1> wrote in message
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into its component parts as the negative energy overwhelms the current
forces. If so then where is all this energy coming from. As it cannot be
destroyed, I can see it can be very defuse but surely in order for matter to
stop existing there has to be something opposite or the current forces must
be diminishing.
Brian
--
>From the Bed of Brian Gaff.
The email is valid as bri...@blueyonder.co.uk
Blind user.
"David Spain" <nos...@127.0.0.1> wrote in message
David Spain
Feb 5, 2013, 10:21:09 PM2/5/13
to
On 2/3/2013 3:26 PM, Brian Gaff wrote:
> So then, would the energy in the universe go negative making matter just fly
> into its component parts as the negative energy overwhelms the current
> forces. If so then where is all this energy coming from. As it cannot be
> destroyed, I can see it can be very defuse but surely in order for matter to
> stop existing there has to be something opposite or the current forces must
> be diminishing.
>
> Brian
>
No official "postulates" from anything I've read, however I have a
> So then, would the energy in the universe go negative making matter just fly
> into its component parts as the negative energy overwhelms the current
> forces. If so then where is all this energy coming from. As it cannot be
> destroyed, I can see it can be very defuse but surely in order for matter to
> stop existing there has to be something opposite or the current forces must
> be diminishing.
>
> Brian
>
personal purely conjectured favorite. And that is that the so-called
"ground-state" quantum vacuum energy is positive.
Dave
David Spain
Feb 6, 2013, 10:29:15 AM2/6/13
to
the one we experience today. There may be little if any "free matter" in
existence, having been previously swallowed into the nearest black hole.
What we are really talking about is the evolution of a black hole.
Perhaps known physics can only meaningfully discuss the dissolution of
normal space time as the evaporating membrane surrounding an event
horizon. The end state universe is beyond strange.
Dave
Brian Gaff
Feb 8, 2013, 8:10:33 PM2/8/13
to
So then, in the end does a black hole have a finite 'size' beyond which
another big bang has to occur, releasing all that energy again.
Brian
--
>From the Bed of Brian Gaff.
The email is valid as bri...@blueyonder.co.uk
Blind user.
"David Spain" <nos...@127.0.0.1> wrote in message
news:w6KdnXdMSJG06I_M...@giganews.com...
another big bang has to occur, releasing all that energy again.
Brian
--
>From the Bed of Brian Gaff.
The email is valid as bri...@blueyonder.co.uk
Blind user.
"David Spain" <nos...@127.0.0.1> wrote in message
David Spain
Feb 11, 2013, 8:00:47 AM2/11/13
to
On 2/8/2013 8:10 PM, Brian Gaff wrote:
> So then, in the end does a black hole have a finite 'size' beyond which
> another big bang has to occur, releasing all that energy again.
>
> Brian
>
>
Well given current state of cosmology, from what I've read I'd have to conclude no.
> So then, in the end does a black hole have a finite 'size' beyond which
> another big bang has to occur, releasing all that energy again.
>
> Brian
>
>
It would have been a 'neat' way to close out a cyclical universe, but given the speed of expansion vs. contraction due to gravity
current theory says expansion wins out. That means black holes that are far enough apart will never collapse together due to
gravity, since expansion will drive them apart first, far enough that gravity cannot be felt between them I would presume. That
means no singular black hole would ever become massive enough to trigger another big bang upon 'evaporation' due to Hawking
radiation. If we assume this universal expansion is THAT powerful, it's not hard to imagine what it would ultimately either rip
apart a black hole or absorb and dissolve its 'explosion' in the absence of space time itself. Or perhaps it opens up another
universe of different dimensions and pitches the black hole into a white hole in that other dimension. Hard to prove that
experimentally...
OTOH if an experimentalist can prove non-zero ground-state vacuum energy, there would no doubt be a Nobel Prize in Physics lurking
there for such a clever scientist.... Need a goal?
Dave
Peter Fairbrother
Feb 11, 2013, 1:17:13 PM2/11/13
to
On 11/02/13 13:00, David Spain wrote:
> OTOH if an experimentalist can prove non-zero ground-state vacuum
> energy, there would no doubt be a Nobel Prize in Physics lurking there
> for such a clever scientist.... Need a goal?
Hasn't that been done? Casimir effect? It is standard model.
> OTOH if an experimentalist can prove non-zero ground-state vacuum
> energy, there would no doubt be a Nobel Prize in Physics lurking there
> for such a clever scientist.... Need a goal?
-- Peter Fairbrother
David Spain
Feb 11, 2013, 8:42:39 PM2/11/13
to
effect is that it measures "resonances" or fluctuations in the vacuum
energy between closely spaced parallel plates and can actually measure
an attractive or repulsive force between them. But there are other
interpretations that don't invoke ZPE to explain the effect. Therefore
it does not establish a definitive existence of vacuum energy, nor does
it establish a value for the ground state vacuum energy.
A non-zero ground state vacuum energy would imply a form of
'anti-gravity' the pervades the universe and drives its expansion. At
least that is my understanding of the situation. And although the former
has been proved by a Nobel Prize winning experiment the latter still
awaits its Nobel (my bias is showing)...
The Casimir effect, if it truly is observing ZPE, is pretty astounding.
Almost (but not quite IMHO) as weird as the locally intuitive 2nd Law of
Thermodynamics is when considered at the cosmological scale....
Dave
David Spain
Feb 11, 2013, 8:42:49 PM2/11/13
to
On 2/11/2013 1:17 PM, Peter Fairbrother wrote:
http://arxiv.org/pdf/hep-th/0503158v1.pdf
I haven't read through this in depth, but if you want to discuss Jaffe's
paper further I will attempt a full read and give you my two cents
(literally about what my knowledge here is worth)...
Dave
Greg (Strider) Moore
Feb 11, 2013, 8:43:20 PM2/11/13
to
>"Brian Gaff" wrote in message news:kf38fv$9oi$1...@dont-email.me...
Well part of the problems (as I see them, someone correct me if I'm wrong)
is that the larger a black hole is, the longer it takes to evaporate, to the
point that the largest would take longer than the expected life of the
universe. That said, I suppose if they still exist, so would the universe,
so not really sure how works. :-)
But I could see it evaporating so slowly that the particles would spread out
"infinitely" and by the time it does fully evaporate, there basically would
be such a low density that basically the definition of the word universe
ceases to have any meaning.
Also, if particles are far enough that they never interact, what happens to
"time". Can time even exist if nothing is happening. (i.e. if there is no
way to measure the movement between particles (since they're too far away to
interact) there can be no concept of a clock and according to some theories
time simply ceases to exist.
>So then, in the end does a black hole have a finite 'size' beyond which
>another big bang has to occur, releasing all that energy again.
>
>Brian
>
--
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net
David Spain
Feb 13, 2013, 7:23:03 PM2/13/13
to
On 2/11/2013 8:43 PM, Greg (Strider) Moore wrote:
>> "Brian Gaff" wrote in message news:kf38fv$9oi$1...@dont-email.me...
>
> Well part of the problems (as I see them, someone correct me if I'm
> wrong)
ok :-)
>> "Brian Gaff" wrote in message news:kf38fv$9oi$1...@dont-email.me...
>
> Well part of the problems (as I see them, someone correct me if I'm
> wrong)
> is that the larger a black hole is, the longer it takes to
> evaporate, to the point that the largest would take longer than the
> expected life of the universe. That said, I suppose if they still
> exist, so would the universe, so not really sure how works. :-)
>
universe or that of one that ends at zero energy with a local
super-cluster black hole there really isn't anything left surrounding
the event horizon we'd recognize as a Universe....
> But I could see it evaporating so slowly that the particles would spread
> out "infinitely" and by the time it does fully evaporate, there
> basically would be such a low density that basically the definition of
> the word universe ceases to have any meaning.
>
'evaporate' uniformly. The process is non-linear and actually speeds up
as the hole looses mass. Current theory claims that once the mass of
hole shrinks to Planck mass the dissolution would complete nearly
instantly in a violent burst of Gamma. But there are still missing
theoretical pieces to that model, I'll admit. But the current thinking
is that it does not end quietly.
http://en.wikipedia.org/wiki/Hawking_radiation
See bullet items and end of para. on Black Hole Evaporation.
> Also, if particles are far enough that they never interact, what happens
> to "time". Can time even exist if nothing is happening. (i.e. if there
> is no way to measure the movement between particles (since they're too
> far away to interact) there can be no concept of a clock and according
> to some theories time simply ceases to exist.
>
everything else is a near zero energy universe. It becomes quantized and
virtual. It winks in and out of existence along with all other virtual
'particles'. I've always considered time to be a scalar unit, without
individual form. It's a vector under differentiation but is itself
without reality. It can only be a measure or characteristic of a 'real'
phenom, the most fundamental probably being the photon.
Much of the thinking about end-state universe is unfortunately still
dominated (even in the early 21st century) by classical Newtonian
concepts of space and time.
We have to stop thinking about the vacuum of space as being empty. To
directly address the original topic of this post, under current quantum
theory the answer is no. Space is never really empty. Recently there has
been a better experiment than the one performed by Casimir et al back in
the late 40's, that seems to more directly address the issue known as
the 'Dynamic Casimir' effect. (As terrible nomenclature, since the
Casimir Effect is often stated as proof of the existence of vacuum
energy when it really isn't, but use of the concept (vacuum energy)
provided a calculation 'convenience' for explaining the phenomena at the
time.)
I refer to the work done by Wilson et al. at Chalmers University of
Technology in Goteborg Sweden and reported in Nature on 17 November
2011. A summary of this work can be found here:
> http://www.sciencedaily.com/releases/2011/11/111118133050.htm
and if you want the details and are willing to spend USD $32 a on
reprint, here:
> http://www.nature.com/nature/journal/v479/n7373/full/nature10561.html#/affil-auth
Dave
David Spain
Feb 13, 2013, 7:23:21 PM2/13/13
to
> I've always considered time to be a scalar unit, without individual
> form. It's a vector under differentiation but is itself without
> reality. It can only be a measure or characteristic of a 'real'
> phenom, the most fundamental probably being the photon.
Sorry, this is a confused (stupid) statement. What I meant to say was
> form. It's a vector under differentiation but is itself without
> reality. It can only be a measure or characteristic of a 'real'
> phenom, the most fundamental probably being the photon.
that time, although scalar, has a preferred direction. Let's leave
differentiation out of it....
My apologies to mathematicians everywhere...
Dave
David Spain
Feb 13, 2013, 7:23:37 PM2/13/13
to
David Spain wrote:
> and if you want the details and are willing to spend USD $32 a on reprint, here:
>
>> http://www.nature.com/nature/journal/v479/n7373/full/nature10561.html#/affil-auth
Or save yourself the USD $32 thanks to link provided by an MIT
> and if you want the details and are willing to spend USD $32 a on reprint, here:
>
>> http://www.nature.com/nature/journal/v479/n7373/full/nature10561.html#/affil-auth
Technology Review article to arXiv:
> http://www.technologyreview.com/view/424111/first-observation-of-the-dynamical-casimir-effect/
> http://arxiv.org/abs/1105.4714
Dave
David Spain
Feb 14, 2013, 8:56:05 AM2/14/13
to
On 2/11/2013 8:42 PM, David Spain wrote:
> On 2/11/2013 1:17 PM, Peter Fairbrother wrote:
>> On 11/02/13 13:00, David Spain wrote:
>>
>>> OTOH if an experimentalist can prove non-zero ground-state vacuum
>>> energy, there would no doubt be a Nobel Prize in Physics lurking there
>>> for such a clever scientist.... Need a goal?
>>
>> Hasn't that been done? Casimir effect? It is standard model.
>>
>>
>> -- Peter Fairbrother
>>
>
> I don't think they are the same. One interpretation of the Casimir effect is that it measures "resonances" or fluctuations in the
> vacuum energy between closely spaced parallel plates and can actually measure an attractive or repulsive force between them. But
> there are other interpretations that don't invoke ZPE to explain the effect. Therefore it does not establish a definitive existence
> of vacuum energy, nor does it establish a value for the ground state vacuum energy.
>
That's as applied to the original experiment by Casimir. But hey, theoretical physics is not my day job. Further research shows that
> On 2/11/2013 1:17 PM, Peter Fairbrother wrote:
>> On 11/02/13 13:00, David Spain wrote:
>>
>>> OTOH if an experimentalist can prove non-zero ground-state vacuum
>>> energy, there would no doubt be a Nobel Prize in Physics lurking there
>>> for such a clever scientist.... Need a goal?
>>
>> Hasn't that been done? Casimir effect? It is standard model.
>>
>>
>> -- Peter Fairbrother
>>
>
> I don't think they are the same. One interpretation of the Casimir effect is that it measures "resonances" or fluctuations in the
> vacuum energy between closely spaced parallel plates and can actually measure an attractive or repulsive force between them. But
> there are other interpretations that don't invoke ZPE to explain the effect. Therefore it does not establish a definitive existence
> of vacuum energy, nor does it establish a value for the ground state vacuum energy.
>
there were plenty of other experiments performed from 1958 on that actually DO demonstrate the "Static Casimir" effect and don't
bring up all the Van Der Waals and fine structure issues of Casimir's experiment.
A good summary of these I have subsequently discovered can be found here:
> http://iris.lib.neu.edu/cgi/viewcontent.cgi?article=1001&context=physics_diss
You learn something new every day....
However I'm still waiting to learn if ground state vacuum energy has been proven to be zero or non-zero....
Dave
Steve Willner
Feb 15, 2013, 4:31:04 PM2/15/13
to
In article <RoGdnfCHxLeSLobM...@giganews.com>,
> http://en.wikipedia.org/wiki/Hawking_radiation
> Current theory claims that once the mass of hole shrinks to Planck
> mass...
Current theory is known to be inadequate in this regime; there is no
theory of quantum gravity. However, a black hole of 1 kg mass
evaporates in about 8E-17 s. For other sizes, the time goes as M^3,
but this is an entirely classical (i.e., general relativity but no
quantum mechanics) calculation, so it won't be valid at very small
masses. (It should be fine at 1 kg and indeed several orders of
magnitude smaller.)
--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123 swil...@cfa.harvard.edu
Cambridge, MA 02138 USA
David Spain <nos...@127.0.0.1> writes:
> Black holes do not 'evaporate' uniformly. The process is non-linear
> and actually speeds up as the hole looses mass.
Yes. There's a formula in the Wikipedia article you cite:
> Black holes do not 'evaporate' uniformly. The process is non-linear
> and actually speeds up as the hole looses mass.
> http://en.wikipedia.org/wiki/Hawking_radiation
> Current theory claims that once the mass of hole shrinks to Planck
Current theory is known to be inadequate in this regime; there is no
theory of quantum gravity. However, a black hole of 1 kg mass
evaporates in about 8E-17 s. For other sizes, the time goes as M^3,
but this is an entirely classical (i.e., general relativity but no
quantum mechanics) calculation, so it won't be valid at very small
masses. (It should be fine at 1 kg and indeed several orders of
magnitude smaller.)
--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123 swil...@cfa.harvard.edu
Cambridge, MA 02138 USA
Alain Fournier
Feb 19, 2013, 6:17:13 PM2/19/13
to
On 02/15/2013 4:31 PM, Steve Willner wrote:
> In article <RoGdnfCHxLeSLobM...@giganews.com>,
> David Spain <nos...@127.0.0.1> writes:
>> Black holes do not 'evaporate' uniformly. The process is non-linear
>> and actually speeds up as the hole looses mass.
>
> Yes. There's a formula in the Wikipedia article you cite:
>> http://en.wikipedia.org/wiki/Hawking_radiation
>
>> Current theory claims that once the mass of hole shrinks to Planck
>> mass...
>
> Current theory is known to be inadequate in this regime; there is no
> theory of quantum gravity. However, a black hole of 1 kg mass
> evaporates in about 8E-17 s. For other sizes, the time goes as M^3,
> but this is an entirely classical (i.e., general relativity but no
> quantum mechanics) calculation, so it won't be valid at very small
> masses. (It should be fine at 1 kg and indeed several orders of
> magnitude smaller.)
>
Could you elaborate a little, or give a pointer to where I could get
> In article <RoGdnfCHxLeSLobM...@giganews.com>,
> David Spain <nos...@127.0.0.1> writes:
>> Black holes do not 'evaporate' uniformly. The process is non-linear
>> and actually speeds up as the hole looses mass.
>
> Yes. There's a formula in the Wikipedia article you cite:
>> http://en.wikipedia.org/wiki/Hawking_radiation
>
>> Current theory claims that once the mass of hole shrinks to Planck
>> mass...
>
> Current theory is known to be inadequate in this regime; there is no
> theory of quantum gravity. However, a black hole of 1 kg mass
> evaporates in about 8E-17 s. For other sizes, the time goes as M^3,
> but this is an entirely classical (i.e., general relativity but no
> quantum mechanics) calculation, so it won't be valid at very small
> masses. (It should be fine at 1 kg and indeed several orders of
> magnitude smaller.)
>
more details? I get that the Schwarzschild radius of a 1 kg black hole
is about 1.5x10^-27 meter. I don't know how one can say that quantum
effects should be small for anything of that size?
I'm not saying that your claim that classical model should be fine
for several orders of magnitude smaller than 1 kg is false. I am
saying that I am ignorant of physics in that domain and I would like to
learn some.
Alain Fournier
Steve Willner
Feb 21, 2013, 7:26:14 AM2/21/13
to
In article <G8OdnUFPDpNGm7nM...@ulaval.ca>,
I've heard experts speak but may have misunderstood or mis-remembered
what they said.
> I get that the Schwarzschild radius of a 1 kg black hole
> is about 1.5x10^-27 meter. I don't know how one can say that quantum
> effects should be small for anything of that size?
Usually it's the mass, not the size, that matters for quantum
effects, but see above about "no expert." The point I was making was
that the decay time for such a small black hole is very short. If
there are quantum effects, they may lengthen or shorten the decay
time, but it would be surprising if quantum effects made such small
black holes last a macroscopic amount of time.
I didn't find any really good sources in a quick web search, but you
may have better luck. One note of interest is that people have been
looking for black hole decays at the LHC, so far without success.
Alain Fournier <alain.f...@crulrg.ulaval.ca> writes:
> Could you elaborate a little, or give a pointer to where I could get
> more details?
I should have put in a disclaimer that I am no expert in this area.
> Could you elaborate a little, or give a pointer to where I could get
> more details?
I've heard experts speak but may have misunderstood or mis-remembered
what they said.
> I get that the Schwarzschild radius of a 1 kg black hole
> is about 1.5x10^-27 meter. I don't know how one can say that quantum
> effects should be small for anything of that size?
effects, but see above about "no expert." The point I was making was
that the decay time for such a small black hole is very short. If
there are quantum effects, they may lengthen or shorten the decay
time, but it would be surprising if quantum effects made such small
black holes last a macroscopic amount of time.
I didn't find any really good sources in a quick web search, but you
may have better luck. One note of interest is that people have been
looking for black hole decays at the LHC, so far without success.
Alain Fournier
Feb 21, 2013, 4:09:51 PM2/21/13
to
On 02/21/2013 7:26 AM, Steve Willner wrote:
> In article <G8OdnUFPDpNGm7nM...@ulaval.ca>,
> Alain Fournier <alain.f...@crulrg.ulaval.ca> writes:
>> Could you elaborate a little, or give a pointer to where I could get
>> more details?
>
> I should have put in a disclaimer that I am no expert in this area.
> I've heard experts speak but may have misunderstood or mis-remembered
> what they said.
That disclaimer probably holds more for me than for you. I have never
> In article <G8OdnUFPDpNGm7nM...@ulaval.ca>,
> Alain Fournier <alain.f...@crulrg.ulaval.ca> writes:
>> Could you elaborate a little, or give a pointer to where I could get
>> more details?
>
> I should have put in a disclaimer that I am no expert in this area.
> I've heard experts speak but may have misunderstood or mis-remembered
> what they said.
attended any physics class at university level. Though I have read some
in my spare time (but I did like physics in high school, thanks Mrs
Kunderlik you were a great teacher).
>> I get that the Schwarzschild radius of a 1 kg black hole
>> is about 1.5x10^-27 meter. I don't know how one can say that quantum
>> effects should be small for anything of that size?
>
> Usually it's the mass, not the size, that matters for quantum
> effects, but see above about "no expert."
principle dx dp > h/(2pi) [dx = uncertainty of position, dp =
uncertainty of momentum]. And since momentum depends on mass...
> The point I was making was
> that the decay time for such a small black hole is very short. If
> there are quantum effects, they may lengthen or shorten the decay
> time, but it would be surprising if quantum effects made such small
> black holes last a macroscopic amount of time.
evaporate in less than 8x10^-17 sec because of quantum effects. But I
don't know. My (naive) line of reasoning is the following:
Imagine that you want to add stuff into the black hole, so you hold the
black hole steady, let's say a speed of 0 plus or minus 1x10^-8 m/s.
Then by Heisenberg Uncertainty principle, you don't know the position
of the black hole within a few Schwarzschild radii, therefore you don't
know where to add the stuff. If you allow for more uncertainty to its
velocity (and therefore momentum) you can (theoretically) locate the
black hole to within its Schwarzschild radius. But with such
uncertainty in its velocity, it can move one Schwarzschild radius in
1.5x10^-27 m/(10^-8 m/s)= 1.5x10^-19 seconds. Therefore, you only have
that amount of time during which you know the position of the black hole
within one Schwarzschild radius and you need to add the mass you want
to add within that time or remeasure the position of the black hole. If
the uncertainty principle says that mass has to be added in a time
frame of 1.5x10^-19 seconds, or it probably won't be added at the right
spot, then I see no reason why mass that is already there will still be
in the right spot in 1.5x10^-19 seconds, and the black hole would
evaporate in that time. Note that this is not just a measurement
problem. It's not that we can't measure the position of the black hole.
It's truly that the position of the black hole probably isn't within
it's Schwarzschild for more than 1.5x10^-19 seconds, or at least that is
my understanding of this.
Alain Fournier
Steve Willner
Feb 26, 2013, 10:20:25 PM2/26/13
to
In article <FbydnSu3upnVFLvM...@ulaval.ca>,
gravity. However, I repeat that I'm no expert. Existing knowledge
constrains some properties of quantum gravity, so maybe something
could be said about this question after all.
Given the difficulty of making a 1 kg black hole, I don't see much
practical need for an accurate answer. :-)
Alain Fournier <alain.f...@crulrg.ulaval.ca> writes:
> I was rather thinking the other way, that a 1 kg black hole would
> evaporate in less than 8x10^-17 sec because of quantum effects.
My _guess_ is that no one can say, absent a proper theory of quantum
> I was rather thinking the other way, that a 1 kg black hole would
> evaporate in less than 8x10^-17 sec because of quantum effects.
gravity. However, I repeat that I'm no expert. Existing knowledge
constrains some properties of quantum gravity, so maybe something
could be said about this question after all.
Given the difficulty of making a 1 kg black hole, I don't see much
practical need for an accurate answer. :-)
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