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Author Topic: Hawking Disappoints Science Fiction Fans  (Read 3408 times)
jpark
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on: August 10, 2004, 09:23:43 AM

It seems that Stephen Hawking (e.g. Brief History of Time book fame etc.)has conceded a bet to a peer of his and has retracted some of his earlier views of Black Holes.  He no longer sees them as the ultimate destroyers of matter nor a bridge to a parallel universe via "worm holes".  I think at stake was a book which he will give his US colleague.

Along with this change in view it appears, if I understand correctly, that Black Holes may no longer be regarded as immortal structures and may dissipate over time.  The matter it traps escapes them.

I don't confess to fully understand this - but this seems to have been made possible in part by erratic shifts in the "event horizon" (although that was a stellar sci fi flick many years ago).  The event horizon is the distance from a black hole from which light, nor any matter, can escape.  I guess given the erratic shifts in this boundary, it is possible for matter to escape over time.

"I think my brain just shoved its head up its own ass in retaliation.
"  HaemishM.
daveNYC
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Reply #1 on: August 10, 2004, 09:52:22 AM

The bet was whether or not information is destroied in a black hole.  Hawking now believes that when a black hole evaporates, the information is released, although in a mangled state.
SirBruce
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Reply #2 on: August 10, 2004, 10:34:35 AM

Right.  Hawking already predicted some time back matter could escape black holes, and the so-called "Hawking Radiation" is nearly accepted as fact today.

There are still other methods by which wormhole structures can exist.

Bruce
jpark
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Reply #3 on: August 10, 2004, 12:02:50 PM

Thanks for that correction.

Hawking radiation is interesting - but did not constitute an escape of matter from the black hole - as I understand it - since a matter / anti-matter pair is created on the edge of the event horizon.  One member of the pair escapes, the other falls to oblivion.  I saw this as an anomoly afforded by the curvature of space at the event horizon - since the matter that "escapes" there was not really matter to be "lost" in the first place (born from the free lunch of Heisenberg uncertainty and tunneling).

In other words- borne from a "free lunch" the matter of hawking radiation was not something I saw as contributing to the evaporation of a black hole over time.  Do I understand that correctly?

"I think my brain just shoved its head up its own ass in retaliation.
"  HaemishM.
SirBruce
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Reply #4 on: August 10, 2004, 12:47:03 PM

That's a pop-sci description of the phenomenon which may or may not be an accurate description of what's actually happening on the local level.  But the bottom line is that there's no "free lunch"; the universe can't create new matter that lasts forever.  So for one particle to survive, it must "steal" that energy from the gravitational energy of the black hole itself, which means the black hole will evaporate by the amount of the energy of the escaping particle, even though the escaping particle wasn't really the same particle that was once inside the event horizon.  It just formed as a result of how energy works in a vacuum.

Bruce
daveNYC
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Reply #5 on: August 10, 2004, 12:47:59 PM

I think the matter/anti-matter pair lead to the loss of mass of the black hole due to the mass being created and lost outside the hole was the same as the mass of the particle that eventually went in the hole, and creating the pair took energy from the hole too.  E=MC^2 and all that.
jpark
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Reply #6 on: August 10, 2004, 02:45:59 PM

Quote from: SirBruce
But the bottom line is that there's no "free lunch"Bruce


That's not my understanding - but I could certainly be wrong.  Classically of course you are right and this is taught in physics at its most basic level.  But with the advent of the Heisenberg Unercertainty principal - "free lunch' can be had provided the amount of energy is very small or the time scale very small.

A popular example is our Sun - not quite large enough to generate and sustain fusion.  But it can - because it is close enough - and the difference in the energy required can be obtained through Heisenberg.  In chemical reactions this is also common, where the barrier to activation is very nearly attained - but not quite (enzymes etc.).  In all of this the common term I hear is "tunnelling".

Over large time scales or energy levels there is no free lunch.  But the details - the small dimensions - is where this rule breaks down.   It is an interesting discussion on how macro events can be affected by micro events that violate physical law as we know it on a grander level.

DaveNYC - your comment that the creation of the anitmatter pair in Hawking radiation is the source of the dissipation of the black hole could be right - but again, I have trouble seeing that currently.

The best example of Free Lunch thinking is the recognition that Heisenberg Uncertainty not only has a different dynamic for small time / energy scales - but is affected by the curvature of space.  The curvature of space time at the limit of the event Horizon is thought to mimic in some senses the singularity at the "inception" of the "big bang".  With extreme warps in space time - the amount of energy that can be borrowed, and the time scales - become much larger.  I believe this is where it is thought the intial energy for the universe came from (Alan Guth and his Inflationary Universe?  can't remember).

So I see free lunches in the form of quantum mechanical tunneling in chemistry, our sun and discussion of the early period of our universe.  Because of this - it does not make sense to me that Hawking radiation is the source of the Black Hole's eventual evaporation (Einstein's E=MC2 not withstanding or Newton's Conservation of Mass and Energy).

Again I could be wrong - that's my current understanding.

"I think my brain just shoved its head up its own ass in retaliation.
"  HaemishM.
SirBruce
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Reply #7 on: August 10, 2004, 03:07:02 PM

Those are not free lunches.  Mass and energy are conserved.  It can only be vioalted on small time scales; the debt has to be repaid.  All the examples you cited are temporary effects.

That's the point of Hawking radiation... the repay the debt, the black hole must evaporate, because the particle the escapes is 'permanent".

Bruce
personman
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Reply #8 on: August 10, 2004, 03:36:28 PM

Greene's The Elegant Universe was recently revised (however slightly) and is worth a read.
jpark
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Reply #9 on: August 11, 2004, 09:48:20 PM

Bruce - in exception for the cosmological example, your right.

While theoretical, the explanation of such "borrowing" is last I saw evoked to explain the origin of energy in the universe given the extreme curvature of spacetime prior to expansion.  This would strike me as a non-temporary use of this dynamic?

Personman - not familiar with that book but I will look it up.  One of my favorites here is now rather dated, but a classic and I got to see the author speak at MIT many years ago:

The First 3 Minutes.  By Steven Weinberg.   1977 I think - I forget the publisher (my hotel connection is deathly slow so passing on a Google search to verify).

He won the Nobel prize (jointly) for his work in electroweak unification.  This book was really intended for his peers not lay people, but is accessible.  It is still credited today to be the first book to take big bang cosmology from the "best we have" to a "good theory".

Last comment - I have heard it said that Hawking supports the strong anthropic theory - any one care to explain why he supports this?

"I think my brain just shoved its head up its own ass in retaliation.
"  HaemishM.
Murgos
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Reply #10 on: August 12, 2004, 07:44:52 AM

Because he's fairly religious?  Probably not, but it's amazing how religious people (like my father who is actually usually fairly intelligent) get relativity and relativism confused.  Not like confused over the words but they tend to think in absolutes (which is where the problem is) so if time and distance can be relative they think your saying morality must also be relative.

Stephen Hawking touches on the subject of the strong and weak anthropic theories  in "A Brief History of Time" but I haven't seen anything where he expand upon why.

"You have all recieved youre last warning. I am in the process of currently tracking all of youre ips and pinging your home adressess. you should not have commencemed a war with me" - Aaron Rayburn
personman
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Reply #11 on: August 12, 2004, 07:59:52 AM

Science is incomplete enough that there is still room to find inspirations elsewhere.  The ancients mayhaps didn't understand what they were seeing and their explanations could be pretty cockeyed, but that doesn't mean their intuition is irrelevant.

True I'll take Hawkings over Lucretious anyday, but Lucretious and his mentoree Democratus had valid insight.

Scientism is no less a tool of fanaticism and entrenched bureaucracy than any other "-ism"/"-cy".
SirBruce
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Reply #12 on: August 12, 2004, 09:08:15 AM

The Anthropic Principle (strong or weak) are pretty much as close to a widespread philosophical belief that exists in scientific circles.  It's not surprising, considering it makes a lot of logical sense. :)  Beyond that, you do have a lot of scientists who believe in a Deist-like teleological or cosmological notion of the divine, be they Christian or Jewish or whatever, and it is easy enough to integrate the two beliefs.  I could direct you to my college Phil 402 thesis on this but I don't have an electronic copy of it and besides it contains some errors I need to address someday.

Bruce
Arcadian Del Sol
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Reply #13 on: August 12, 2004, 09:54:34 AM

wow. and my Newtonian thread was too heady??

I gave up trying to understand black holes when the captain somehow ended up INSIDE Maximillian

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jpark
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Reply #14 on: August 14, 2004, 05:56:46 PM

Normally I have a bad memory for details.  When Steven Weinberg gave a talk at MIT more than 10 years ago (hehe dating myself) in the beginning of his talk he made this comment to the assembled:

"Talking about the [strong] anthropic theory is a little like a clergy man who talks about pornography:  it doesn't matter if in the end you come out not supporting the idea because people [in our community] can't help but wonder if you're getting too interested for your own good anyway."

Bruce - not sure I follow your comment.  According the quote above, the weak is widely held among scientists but the strong form is not.  Do you concurr?

Arc - you started this heady stuff :)

I have launched into this for those few who are interested - but if you're new to this stuff and have any questions - fire away.

Cheers.

"I think my brain just shoved its head up its own ass in retaliation.
"  HaemishM.
SirBruce
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Reply #15 on: August 14, 2004, 06:47:39 PM

Yes.  For most scientists, the weak version is almost self-evident.

The Weak Anthropic Principle (WAP): "The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the Universe be old enough for it to have already done so."

In other words, the universe is the way it is because we are here to view it.  Were the universe very much different, we wouldn't be around to measure it.  It's almost a tautology, and really doesn't tell us anything, but is simply a way for us to avoid not having an answer for the fundamental question of why things are the way they are.

There are two "stronger" versions of the Antrhopic Principle which are often intermingled.  Basically, anytime is willing to state something that goes beyond the WAP, they are said to be advocating a strong version.  The two common versions are:

Strong Anthropic Principle (SAP): "The Universe must have those properties which allow life to develop within it at some stage in its history."
 
Final Anthropic Principle (FAP): "Intelligent information-processing must come into existence in the Universe, and, once it comes into existence, it will never die out."

These ideas basically assert, as an article of faith but based upon observation, that there indeed we MUST be here, and the universe is, in a sense, DESIGNED for it to be so.  It borders onto the traditional teleological arguments for design, and to some even suggest the existance of a God, or at least a God-like principle, that is running the show.  Indeed, the FAP suggests a melioristic tendency of the universe; that is, that nature itself is striving towards a goal of a better existance.  This is echoed in modern process theology and runs all the way back to Greek notions of ideal forms.  Many scientists like this because it helps unify their work with other forms of human thought; others dismiss it for the same reasons; i.e. too much "mumbo-jumbo" for their tastes.

Bruce
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