LIGO discovers gravitational waves

| 118 Comments

A friend of mine, a theoretical physicist, has been telling me for over 30 years that we will never discover a magnetic monopole, proton decay – or the graviton. So far, he appears to have been correct, but now scientists at LIGO have detected a gravitational wave that resulted from the collision and amalgamation of 2 black holes. The news was so exciting that the server at Physical Review Letters supposedly crashed earlier today. I got a copy of the article but, as Shakespeare might have put it, much of it was written in Greek. The 2 graphs, shown in the Times article, look mighty convincing, though.

The graviton, if it exists, is the quantized particle that carries the gravitational field, much as the photon carries the electromagnetic field. I am not, alas, a theoretical physicist, so I do not know whether a gravitational wave necessarily implies a graviton. Unless I am mistaken, any classical (nonrelativistic) wave such as an electromagnetic wave or even a sound wave can be quantized, but I have no idea whether a (relativistic) gravity wave can necessarily be quantized. Perhaps some reader can shed light on the question.

In the meantime, I give my friend a tentative score of 2.5/3: No one has yet definitively discovered a magnetic monopole, and the lifetime of the proton has not been definitively measured.

Like a commenter on an earlier thread, I am very curious indeed to hear the creationists’ reaction to this stunning news.

118 Comments

Here is a good article by Emanuele Berti explaining the history and discovery.

A lot more is about to come out in the next few weeks.

This has been one of those research projects that has attracted my attention for most of my career. I would loved to have been part of such an experiment; but its development over the years has been one of those experiments that always seemed tantalizingly within reach but kept slipping just “over the horizon” in terms of technological feasibility.

No one has yet definitively discovered a magnetic monopole …

I remember back in 1982, I think, that Blas Cabrera at Stanford picked up a signal in his superconducting lead balloon that was thought to be the expected signal for a magnetic monopole. However, he was never able to reproduce the signal; and in subsequent years other attempts failed to turn up a monopole.

Finally the NSF stopped taking proposals for the search; probably for budgetary reasons. Nowever, some wag concocted a fake letter of rejection from the NSF to a monopole research proposal which said, “We are no longer funding proposals for monopole searches because Dirac has determined that in order for quantum mechanics to be true, there needs to be only one monopole in the universe; and that monopole passed through a detector in the lab of Blas Cabrera at Stanford in 1982.”

Well, I’m not a particle physicist, but —- de Broglie believed in the symmetry of nature strongly enough to posit that since light waves are also particles, then all particles should also be waves. And he was right. So, in my view, following de Broglie: if there are gravitational waves then there are associated gravitons, and since the gravitational waves move at the speed of light, the gravitons must be massless. “Discovering” the graviton, I guess, is a different thing and maybe will never happen. I guess we’d have to get evidence of quantization of gravitational waves (but surely they are?? — everything is).

I am very curious indeed to hear the creationists’ reaction to this stunning news.

Then why are there still light waves?

Glen Davidson

From that article by Berti:

By assuming that a graviton with mass would modify the phase of the waves, they determined an upper bound on the particle’s mass of 1.2×10−22 eV∕c2, improving the bounds from measurements in our Solar System and from observations of binary pulsars. These findings will be discussed in detail in later papers.

Compare this with estimates of the neutrino mass, which are on the order of 0.320 ± 0.081 eV/c2 (sum of 3 flavors).

Maybe the black holes collided during Noah’s Flood? :)

When the creationist responses start in the next few days they will show the following characteristics -

1) They will be wrong in contradictory ways. Some will deny and attack the discovery. Others will pretend to understand and support the physics but will falsely claim that gravity waves are “a problem for evolution” or “a problem for materialism” (combining the straw man claim that science has something to do with philosophical materialism with misunderstanding of and false claims about this discovery).

2) Creationists will not challenge other creationists, no matter how much they contradict each other.

If gravitational waves are actually ripples in space-time itself, would they be constrained to travel no faster than the speed of light?

If gravity turns out to be quantized,can space-time be far behind?

OTOH, I have no idea how quantized space-time could be reconciled with the observed rotational symmetry of the universe.

Happy Darwin Day! from author “et. al. # 500 +_ 50”, (There are about 1000 authors on our discovery paper.)

This is a once in a lifetime moment for us gravity wavers. Perhaps lost in the buzz is that multiple discoveries have been made. First, the direct detection of gravitational waves. Second, the direct detection of a close binary pair of blackholes (that ‘eat’ each other to become a 60 solar-mass black hole. Third, a confirmation of Einstein’s equation in the extreme “strong gravity” limit. Fourth, the confirmation of the numerical calculation of waveforms for binary blackholes, starting from Einstein’s equation.

As for gravitons, they will never be discovered this way. These waves are very classical, meaning they contain maybe 10^50 (?) or so gravitons, if they have the expected quantum values, and so their presence or absence is undetectable.

Scott F said:

If gravitational waves are actually ripples in space-time itself, would they be constrained to travel no faster than the speed of light?

An interesting and very good question.

Let’s see if this can be explained in layman’s terms without any math whatsoever; a rather difficult task in my opinion.

Basically it comes down to the fact that clocks are physical systems whose sequences of events must travel in a “spacetime manifold” and be compared at spatial locations in that manifold. in order to measure speed. Time and space are interlocked for us; we are embedded in that spacetime manifold and can’t get out of the game.

The speed of anything in the universe is determined by clocks and lengths. Clocks are physical systems that produce sequences of physical events taken as standard markers against which other phenomena are compared as temporal events. Lengths are set out in some sort of grid in space. Information about these events has to travel and be compared at specific locations within this spacetime.

Anything that traverses between two points in space and compared one-to-one with events coming from a “clock” will have these measurements “conspire” (this is where the math is) to have an extreme upper limit of the speed of light. Events coming from clocks have to traverse space in order to be compared locally at each point in space with other events. Space and time are intricately intertwined.

In other words, we are embedded in a spacetime in which the physical systems and lengths we use to measure speeds will behave according to special and general relativity. The speed of light is the upper limit in that spacetime.

Also, in that spacetime, accelerating anything with mass up to the speed of light takes infinite energy.

A simple, shorter, but more mathematical answer would be that there are a number of “four-vectors” in relativity that are invariant under Lorentz transformations from one reference frame to another. For example, (Δr)2 - (cΔt)2 , where (Δr)2 is the square of the spatial interval between events, remains constant in all inertial reference frames. Space and time measurements are interlocked in this way.

A more complete answer involves the concept of spacetime being locally Lorentzian; and that tells us the mathematical structure of spacetime in relativity and how space and time are interconnected so as to conspire to produce speed measurements having the upper speed limit being c, the speed of light for massless particles.

Other spacetimes have been and are still being explored; but so far, we have Einstein’s special and general relativity determining how things get “measured out.”

Warren Johnson said:

Happy Darwin Day! from author “et. al. # 500 +_ 50”, (There are about 1000 authors on our discovery paper.)

This is a once in a lifetime moment for us gravity wavers. Perhaps lost in the buzz is that multiple discoveries have been made. First, the direct detection of gravitational waves. Second, the direct detection of a close binary pair of blackholes (that ‘eat’ each other to become a 60 solar-mass black hole. Third, a confirmation of Einstein’s equation in the extreme “strong gravity” limit. Fourth, the confirmation of the numerical calculation of waveforms for binary blackholes, starting from Einstein’s equation.

As for gravitons, they will never be discovered this way. These waves are very classical, meaning they contain maybe 10^50 (?) or so gravitons, if they have the expected quantum values, and so their presence or absence is undetectable.

Congratulations!

What struck me was the amount of detail that this presented. I was expecting that there would be a report with little more than “we found evidence that there is such a thing as gravitational waves”. And, of course, that the first one showed up so soon. This sounds like it is promising to be a real astronomical observatory.

Warren Johnson said:

Happy Darwin Day! from author “et. al. # 500 +_ 50”, (There are about 1000 authors on our discovery paper.)

This is a once in a lifetime moment for us gravity wavers. Perhaps lost in the buzz is that multiple discoveries have been made. First, the direct detection of gravitational waves. Second, the direct detection of a close binary pair of blackholes (that ‘eat’ each other to become a 60 solar-mass black hole. Third, a confirmation of Einstein’s equation in the extreme “strong gravity” limit. Fourth, the confirmation of the numerical calculation of waveforms for binary blackholes, starting from Einstein’s equation.

As for gravitons, they will never be discovered this way. These waves are very classical, meaning they contain maybe 10^50 (?) or so gravitons, if they have the expected quantum values, and so their presence or absence is undetectable.

Ye gods, I forgot to write a note saying that today was Darwin’s birthday! Must be Craft disease.

I want to echo Mr. TomS’s congratulations and also thank you for the amplification.

Regarding gravitons: I am not obsessed, and I certainly realized that this wave was not a single graviton. But I still wonder, given all the difficulty marrying quantum mechanics and general relativity, do we nevertheless presume that the gravitational field can in principle be quantized? Or is it possible that my friend is right, and there are no gravitons?

Mike Elzinga said:

Scott F said:

If gravitational waves are actually ripples in space-time itself, would they be constrained to travel no faster than the speed of light?

An interesting and very good question.

Let’s see if this can be explained in layman’s terms without any math whatsoever; a rather difficult task in my opinion.

Basically it comes down to the fact that clocks are physical systems whose sequences of events must travel in a “spacetime manifold” and be compared at spatial locations in that manifold. in order to measure speed. Time and space are interlocked for us; we are embedded in that spacetime manifold and can’t get out of the game.

The speed of anything in the universe is determined by clocks and lengths. Clocks are physical systems that produce sequences of physical events taken as standard markers against which other phenomena are compared as temporal events. Lengths are set out in some sort of grid in space. Information about these events has to travel and be compared at specific locations within this spacetime.

Anything that traverses between two points in space and compared one-to-one with events coming from a “clock” will have these measurements “conspire” (this is where the math is) to have an extreme upper limit of the speed of light. Events coming from clocks have to traverse space in order to be compared locally at each point in space with other events. Space and time are intricately intertwined.

In other words, we are embedded in a spacetime in which the physical systems and lengths we use to measure speeds will behave according to special and general relativity. The speed of light is the upper limit in that spacetime.

Also, in that spacetime, accelerating anything with mass up to the speed of light takes infinite energy.

A simple, shorter, but more mathematical answer would be that there are a number of “four-vectors” in relativity that are invariant under Lorentz transformations from one reference frame to another. For example, (Δr)2 - (cΔt)2 , where (Δr)2 is the square of the spatial interval between events, remains constant in all inertial reference frames. Space and time measurements are interlocked in this way.

A more complete answer involves the concept of spacetime being locally Lorentzian; and that tells us the mathematical structure of spacetime in relativity and how space and time are interconnected so as to conspire to produce speed measurements having the upper speed limit being c, the speed of light for massless particles.

Other spacetimes have been and are still being explored; but so far, we have Einstein’s special and general relativity determining how things get “measured out.”

Thanks, Mike. Okay. I’m cool with “four-vectors”, and invariant relationships under certain transformations. I’m assuming a Lorentz transform is a particular kind of (probably) reversible shift of reference frames.

The question was motivated by the notion that motion within space is limited, but that space itself (as in the Big Bang) can expand faster than the speed of light. I think you answered it, but it was more of a question of, if a gravity wave is, not a motion within space-time, but a motion of space-time, whether that effect of deforming space-time was also velocity limited.

I’m also envisioning the layman’s notion of mass “deforming” the shape of space-time. You “experience” the acceleration of gravity because of the shape of the space-time that you pass through around the massive object. For example, if a massive object were to come into existence suddenly (an analog of dropping a rock into a pond), would you experience the gravity of that object before you saw the light from that object, or would the gravity (i.e. the deformation of the surrounding space-time) and the light “arrive” at your location at the same instant?

If I understand your explanation, the light and the gravity wave (the change in the deformation of space-time) would arrive at your location at the same instant (more or less).

Scott F said:

The question was motivated by the notion that motion within space is limited, but that space itself (as in the Big Bang) can expand faster than the speed of light. I think you answered it, but it was more of a question of, if a gravity wave is, not a motion within space-time, but a motion of space-time, whether that effect of deforming space-time was also velocity limited.

As I mentioned, it is a bit difficult to explain in layman’s terms. I’m still challenging myself to see if it is possible to explain without the math. The math is more direct and understandable; but not helpful for the layperson.

But we are limited by the fact that we measure physical events - whether light pulses from a clock or lengths, or momentum and energy, etc. - all of which are embedded along with ourselves in that spacetime. We are stuck with it; and it is the interrelationships among those temporal and spatial events that we measure. It is the local structure of spacetime - for us, rather “flat” and “Lorentzian”- that determines those interrelationships. We simply cannot measure anything physical that travels faster than light; none of our physical processes and tools behave that way. That seems to be an experimental fact.

This is not to say that we cannot envision other spacetime manifolds and dimensions and design experiments to look for the predicted effects as observed from within those geometries. But, as far as we know now, Einstein’s relativity and spacetime manifold appear to be what we are “swimming in;” or, at least, what we can sense with our best instruments, which are all physical. We are integrated into the very “fabric of that Matrix.”

Why should this minor physics thing be relevant to creationists? why does the author of the thread think it is? what is his prediction creationists would be dismayed by this? I saw on a ID blog about this and its welcome. In fact they said it confirmed Einstein or something. I don’t follow physics stuff like this and don’t know why its a surprise. However it seems cool to prove the simple working order of the universe at this level. Just like a thinking creator would do it! Biology is more complicated and so the greater intellectual challenge anyways. Creationists know that!

Robert Byers said:

Why should this minor physics thing be relevant to creationists? why does the author of the thread think it is? what is his prediction creationists would be dismayed by this? I saw on a ID blog about this and its welcome. In fact they said it confirmed Einstein or something. I don’t follow physics stuff like this and don’t know why its a surprise. However it seems cool to prove the simple working order of the universe at this level. Just like a thinking creator would do it! Biology is more complicated and so the greater intellectual challenge anyways. Creationists know that!

Perhaps you have heard of Jason Lisle who used to work for Ken Ham but now works at the Institute for Creation research? He is a YEC; as you may know.

He has a “PhD” in astrophysics, yet completly mangles physics at even the high school and undergraduate level. He can’t do basic orbital mechanics, and he has a completely bizarre “theory of relativity” that he claims allows the universe to be 6000 years old. It totally conflicts with all experimental evidence; but he doesn’t seem to notice.

So why do you claim that ID/creationists don’t care, or are not surprised? Why would people like Lisle and Granville Sewell get basic physics so wrong all the time? Did you know that William Dembski also mangles physics? Did you know that Dembski was never even considered for the 2013 Nobel Prize in chemistry?

If you don’t know anything about physics, why do you think this is less important than biology?

Evidentally you don’t care about things you don’t know; and don’t bother to know about things you don’t care about. Why is that good?

Matt Young said:

Regarding gravitons: I am not obsessed, and I certainly realized that this wave was not a single graviton. But I still wonder, given all the difficulty marrying quantum mechanics and general relativity, do we nevertheless presume that the gravitational field can in principle be quantized? Or is it possible that my friend is right, and there are no gravitons?

Your friend is right. Essentially all physicists expect that gravity ought to be quantized, just like light and matter, BUT, every attempt to combine quantum mechanics with general relativity has run into intractable mathematical problems. A real mystery of physics.

Robert Byers said:

Why should this minor physics thing be relevant to creationists? why does the author of the thread think it is? what is his prediction creationists would be dismayed by this? I saw on a ID blog about this and its welcome. In fact they said it confirmed Einstein or something. I don’t follow physics stuff like this and don’t know why its a surprise. However it seems cool to prove the simple working order of the universe at this level. Just like a thinking creator would do it! Biology is more complicated and so the greater intellectual challenge anyways. Creationists know that!

Astronomers, physicists, chemists, and geologists all agree that biologists know what they are doing. We all respect the biologist’s superior knowledge of life, and accept their consensus: modern evolution theory is correct. We all honor Darwin as a great scientist, one of the few from so long ago that is still a pleasure to read. The anti-Darwinists are a very tiny minority, mostly not actual scientists.

As Mike Elzinga suggested above, we all agree that the “creation science” of Answers in Genesis is really science fiction contradicted by accepted science at every turn.

For example, astronomers agree that the universe is MUCH older than the 6000 years that Ken Ham allows. We know it to be about 14 billion years old. And we know that the earth is about 4 billion years old.

Scott F said:

The question was motivated by the notion that motion within space is limited, but that space itself (as in the Big Bang) can expand faster than the speed of light. I think you answered it, but it was more of a question of, if a gravity wave is, not a motion within space-time, but a motion of space-time, whether that effect of deforming space-time was also velocity limited.

I have had a long interest in metaphors that become obstacles to learning; and this is one that I have often wondered about but haven’t tracked as closely as I have others.

I suspect that the rubber sheet metaphor could be taken too literally when picturing spacetime as a stretchable membrane in space, or as a volume of rubber material. I think the issue is somewhat like that of picturing electromagnetic waves like distortions in a “luminiferous ether;” something has to distort as a wave is transmitted.

When that ether gets stripped away, all that remain are Maxwell’s equations and the constituitive relations that arise with the interaction of light with matter. There is no need for an ether.

Similarly, in relativity, what an observer can measure locally is what is important; and those measurements appear to be determined by the special theory of relativity. This is an experimental fact that could have been otherwise; such as Newtonian physics, which it is not.

I’m also envisioning the layman’s notion of mass “deforming” the shape of space-time. You “experience” the acceleration of gravity because of the shape of the space-time that you pass through around the massive object. For example, if a massive object were to come into existence suddenly (an analog of dropping a rock into a pond), would you experience the gravity of that object before you saw the light from that object, or would the gravity (i.e. the deformation of the surrounding space-time) and the light “arrive” at your location at the same instant?

If I understand your explanation, the light and the gravity wave (the change in the deformation of space-time) would arrive at your location at the same instant (more or less).

If an observer is in free-fall, his local environment is Lorentzian (provided there are no tidal forces of any significance over the dimensions of the observer). So in a “uniform” gravitational field, the only way you would feel a “gravitational force” would be to have some other non-gravitational force keeping you from free-falling. You could also look outside your lab at some other reference points in space and time. But without external references outside your lab, you would not necessarily be able to distinguish between a force accelerating you and gravity pulling on you as you sit on a planet that keeps you from falling any further.

So if a uniform gravitational force suddenly appeared at your location, and you were just sitting out in space, you would not feel anything. If you looked at the light, however, you would become aware of it gradually becoming blue-shifted as your speed increased toward the source of gravity and light.

I said -

When the creationist responses start in the next few days they will show the following characteristics -

1) They will be wrong in contradictory ways. Some will deny and attack the discovery. Others will pretend to understand and support the physics but will falsely claim that gravity waves are “a problem for evolution” or “a problem for materialism” (combining the straw man claim that science has something to do with philosophical materialism with misunderstanding of and false claims about this discovery).

2) Creationists will not challenge other creationists, no matter how much they contradict each other.

Robert Byers said -

Why should this minor physics thing be relevant to creationists? why does the author of the thread think it is? what is his prediction creationists would be dismayed by this? I saw on a ID blog about this and its welcome…

Which led to to do a quick check and…

PREDICTION CONFIRMED.

Check out the article and comments section. Warning, don’t read the comments too soon after eating.

http://www.uncommondescent.com/phys[…]ly-detected/

Mike Elzinga said:

Scott F said:

If gravitational waves are actually ripples in space-time itself, would they be constrained to travel no faster than the speed of light?

An interesting and very good question.

Let’s see if this can be explained in layman’s terms without any math whatsoever; a rather difficult task in my opinion.

Basically it comes down to the fact that clocks are physical systems whose sequences of events must travel in a “spacetime manifold” and be compared at spatial locations in that manifold. in order to measure speed. Time and space are interlocked for us; we are embedded in that spacetime manifold and can’t get out of the game.

The speed of anything in the universe is determined by clocks and lengths. Clocks are physical systems that produce sequences of physical events taken as standard markers against which other phenomena are compared as temporal events. Lengths are set out in some sort of grid in space. Information about these events has to travel and be compared at specific locations within this spacetime.

Anything that traverses between two points in space and compared one-to-one with events coming from a “clock” will have these measurements “conspire” (this is where the math is) to have an extreme upper limit of the speed of light. Events coming from clocks have to traverse space in order to be compared locally at each point in space with other events. Space and time are intricately intertwined.

In other words, we are embedded in a spacetime in which the physical systems and lengths we use to measure speeds will behave according to special and general relativity. The speed of light is the upper limit in that spacetime.

Also, in that spacetime, accelerating anything with mass up to the speed of light takes infinite energy.

A simple, shorter, but more mathematical answer would be that there are a number of “four-vectors” in relativity that are invariant under Lorentz transformations from one reference frame to another. For example, (Δr)2 - (cΔt)2 , where (Δr)2 is the square of the spatial interval between events, remains constant in all inertial reference frames. Space and time measurements are interlocked in this way.

A more complete answer involves the concept of spacetime being locally Lorentzian; and that tells us the mathematical structure of spacetime in relativity and how space and time are interconnected so as to conspire to produce speed measurements having the upper speed limit being c, the speed of light for massless particles.

Other spacetimes have been and are still being explored; but so far, we have Einstein’s special and general relativity determining how things get “measured out.”

I’m no physicist but I have noted the following -

1) None of physics is actually completely intuitive to the typical human brain despite the fact that we live in it; before Galileo uniform acceleration due to gravity did not seem intuitively obvious, the Earth seems flat and the Sun seems to travel around the Earth unless you make a significant effort to overcome biases, etc.

2) However, physics through the nineteenth century is generally amenable to “intuitive understanding” when expressed either in mathematics, or in English language summary of what the mathematics shows.

3) To understand physics beyond that level, it seems to be about learning the math. The math still makes sense but English language attempts to explain what the math means increasingly come across as bizarre, incomprehensible, counter-intuitive, etc.

It’s an interesting philosophical question, whether math is some sort of Platonic reality thing, or whether it’s just a set of approximations of how physical systems, including purely model physical systems, behave.

My advice to anyone who wants to be a physicist is “pound math, early, often and to as advanced a level as you can get.”

harold said:

My advice to anyone who wants to be a physicist is “pound math, early, often and to as advanced a level as you can get.”

I think your assessment is quite accurate. It is easy to forget all the stages one has gone through to become proficient in any particular area of physics. I think the same applies to other areas of science also; e.g., I find it difficult to think like a biologist or chemist.

If modern science were intuitively obvious, it would have been understood at least as early as the ancient Greeks.

That link you provided to Uncommonly Dense is quiet revealing of the emotional self-defensiveness of wannabe scientists who have failed miserably and want to blame the scientific community. They have retreated into a belief that they are superior because they have discovered that all scientists are wrong.

Robert Byers and others The two black holes collided and produced that gravitational wave around 1.3 billion years ago.

Just seen. The thoughts of Albert Mohler (as posted at Sensuous Curmudgeon). Some might find this edifying. https://baptistnews.com/ministry/pe[…]ove-anything

What if the gravitational waves show signs of something to add to dark matter and dark energy, another unsuspected major component of the universe?

I attended a symposium on the discovery of gravitational waves yesterday at Kenyon College. Two members of the Kenyon physics department are members of the LIGO team, Dr. Madeline Wade and Dr. Leslie Wade. My mind was boggled going into the symposium, and remains boggled.

It was fun to hear about the early reactions and read some of the team emails from that time. It was also enlightening to hear about the exhaustive analyses that allowed discarding alternative explanations for the detection, alternatives that ranged from environmental noise to the malicious faking of the signal.

ashleyhr said:

Just seen. The thoughts of Albert Mohler (as posted at Sensuous Curmudgeon). Some might find this edifying. https://baptistnews.com/ministry/pe[…]ove-anything

The whole “worldview” song and dance is just projection of their faults onto scientists.

Here’s why…

I have NO predisposition to believing the universe isn’t 6000 years old. I certainly hold no ideology that requires the universe to be 13.8 billion years old. I go with the evidence, as logically interpreted by trained scientists by almost every possible cultural background. If the evidence showed a 6000 year old universe, that’s what I’d accept.

This guy, on the other hand, will say it is 6000 years old, whatever the evidence shows. One of us is willing to accept the evidence and the other has a “worldview” that obliges him to deny the evidence.

That link you provided to Uncommonly Dense is quiet revealing of the emotional self-defensiveness of wannabe scientists who have failed miserably and want to blame the scientific community. They have retreated into a belief that they are superior because they have discovered that all scientists are wrong.

I suspect that the personality structure predates and is largely responsible for their failure in science. The social competence required for a science career are pretty modest, but you do have to be mentally secure enough to accept feedback, and acknowledge that other people can have good ideas, too.

ashleyhr said:

Just seen. The thoughts of Albert Mohler (as posted at Sensuous Curmudgeon). Some might find this edifying. https://baptistnews.com/ministry/pe[…]ove-anything

Mohler claims:

“When we look at what was announced yesterday, we come to it with the full affirmation of all that is revealed in Scripture and of everything Scripture tells us about creation. And we come to understand that a world that is corrupted and affected by sin will actually give us — even through the scientific method — false data that can lead people to false conclusions.

“And we also understand that we are fallen, fragile, fallible thinkers and so as we look at this, if we’re operating from a basically secular worldview, if we believe the universe is going to have to tell us the story all on its own, then there’s no way we’re going to come up with the right story.”

Mohler is asserting that his brand of religion has the monopoly on Absolute Truth and the secular world is wrong because of sin. This is nothing more than typical, arrogant religious bigotry propped up with prideful ignorance.

Mohler’s “religion” is repulsive.

Steve C said:

For less exotic sources of gravitational waves, such as a pair of neutron stars merging to form a black hole, an accompanying electromagnetic signal is quite probable. LIGO is set up to quickly notify optical astronomers when something is seen, and there’s a lot of interest in “multimessenger” astronomy.

That “a pair of neutron stars merging to form a black hole” could be “less exotic” than something else. :-) That’s rich. Or, mind boggling, or something. :-)

Steve C said:

TomS said:

Am I correct in understanding that the changes which are measured in the devices are not the “length” but rather the speed or acceleration or something else related to the change of length? It seems rather implausible that one can measure to a small fraction of the dIameter of proton.

It is a measurement of length (really change of length), just a very clever one, using interference of light. LIGO is an interferometer, designed so that when two beams of light are combined at a detector, they are precisely out of phase. As a result, they exactly cancel (the crests of one wave line up with the troughs of the other.) If one of the beams is shifted even a fraction of a wavelength, the cancellation is no longer exact, and the detector picks up a signal. There’s enough power in the system that even a very small shift away from exact cancellation gives a visible signal. (When it reaches design sensitivity, the instrument should be able to see shifts of a part in 10^{23}.)

I was curious about that. Wouldn’t the “yard stick” or measuring device (in this case, a beam of light) also be effected by the distortion of space-time? Just as I asked the question, the answer became obvious. Yes!

In fact, what is being measured is not a “change in length”, but in a difference in change in length. That’s why you need the perpendicular beams of light. The gravity wave doesn’t change the dimensions of space time uniformly. It changes the “size” of space time in one direction only, perpendicular to the wave front. As the wave front passes, objects in one direction change in length, but objects perpendicular to that do not.

I suppose it might be possible that if the wave front came in parallel to the plane defined by the two perpendicular beams of light, that the detector wouldn’t see them. Or, perhaps if it was in the same plane, but the direction of propagation was at 45 degrees to the right angle of the detector, that the legs might be deflected identical amounts. In either case, it seems to suggest that the detector would have varying sensitivity to the direction of the wave front.

Of course, this is just uninformed guess work.

Scott F said:

Steve C said:

TomS said:

Am I correct in understanding that the changes which are measured in the devices are not the “length” but rather the speed or acceleration or something else related to the change of length? It seems rather implausible that one can measure to a small fraction of the dIameter of proton.

It is a measurement of length (really change of length), just a very clever one, using interference of light. LIGO is an interferometer, designed so that when two beams of light are combined at a detector, they are precisely out of phase. As a result, they exactly cancel (the crests of one wave line up with the troughs of the other.) If one of the beams is shifted even a fraction of a wavelength, the cancellation is no longer exact, and the detector picks up a signal. There’s enough power in the system that even a very small shift away from exact cancellation gives a visible signal. (When it reaches design sensitivity, the instrument should be able to see shifts of a part in 10^{23}.)

I was curious about that. Wouldn’t the “yard stick” or measuring device (in this case, a beam of light) also be effected by the distortion of space-time? Just as I asked the question, the answer became obvious. Yes!

In fact, what is being measured is not a “change in length”, but in a difference in change in length. That’s why you need the perpendicular beams of light. The gravity wave doesn’t change the dimensions of space time uniformly. It changes the “size” of space time in one direction only, perpendicular to the wave front. As the wave front passes, objects in one direction change in length, but objects perpendicular to that do not.

I suppose it might be possible that if the wave front came in parallel to the plane defined by the two perpendicular beams of light, that the detector wouldn’t see them. Or, perhaps if it was in the same plane, but the direction of propagation was at 45 degrees to the right angle of the detector, that the legs might be deflected identical amounts. In either case, it seems to suggest that the detector would have varying sensitivity to the direction of the wave front.

Of course, this is just uninformed guess work.

As I understand it (my 5 quarters of lower division Physics were nearly 50 years ago), LIGO is basically a super-sensitive version of the Michelson-Morley experiment.

Scott F said:

I suppose it might be possible that if the wave front came in parallel to the plane defined by the two perpendicular beams of light, that the detector wouldn’t see them. Or, perhaps if it was in the same plane, but the direction of propagation was at 45 degrees to the right angle of the detector, that the legs might be deflected identical amounts. In either case, it seems to suggest that the detector would have varying sensitivity to the direction of the wave front.

Of course, this is just uninformed guess work.

You are correct in that there are directions and waveforms that are more easily detectable than others for a single Michelson interferomenter detector.

One of the reasons for having two or more identical detectors placed large distances apart is to be able to use the time differences and different orientations of the detectors to overcome that problem. When you have detectors spread out over the surface of the earth, they will be oriented differently with respect to the wave that sweeps over them during any given detection. The time differences and slightly different responses then provide more data about the direction from which the gravity wave came and also allow a more detailed analysis of the type of wave; which, in turn allows a more detailed analysis of the event that produced the wave.

W. H. Heydt said:

As I understand it (my 5 quarters of lower division Physics were nearly 50 years ago), LIGO is basically a super-sensitive version of the Michelson-Morley experiment.

The Michelson interferometer is one of the simplest and most useful interferometers used in scientific and technological measurements. It is ideal for this particular experiment because it directly compares changes in length in perpendicular directions.

As an aside here, this measurement gets at the heart of why creationist Jason Lisle’s “relativity” is so bogus. The Michelson interferometer doesn’t measure waves going away compared to waves coming toward a point in space; it measures perpendicular directions in space for various locations of the detector at all orientations of the detector in space. Thus the original Michelson-Morley experiment not only placed the interferometer on a rotating platform, the entire experiment sits on a rotating Earth which is also orbiting the Sun. So the experiment compares directions at various locations and all orientations.

Optical Coherence Tomography is one of many examples of where the Michelson interferometer is used.

Scott F said:

Steve C said:

TomS said:

Am I correct in understanding that the changes which are measured in the devices are not the “length” but rather the speed or acceleration or something else related to the change of length? It seems rather implausible that one can measure to a small fraction of the dIameter of proton.

It is a measurement of length (really change of length), just a very clever one, using interference of light. LIGO is an interferometer, designed so that when two beams of light are combined at a detector, they are precisely out of phase. As a result, they exactly cancel (the crests of one wave line up with the troughs of the other.) If one of the beams is shifted even a fraction of a wavelength, the cancellation is no longer exact, and the detector picks up a signal. There’s enough power in the system that even a very small shift away from exact cancellation gives a visible signal. (When it reaches design sensitivity, the instrument should be able to see shifts of a part in 10^{23}.)

I was curious about that. Wouldn’t the “yard stick” or measuring device (in this case, a beam of light) also be effected by the distortion of space-time? Just as I asked the question, the answer became obvious. Yes!

Not quite – the effect on light is a bit different. One way to think about this is to remember that an interferometer doesn’t really measure the wavelength of light, it measures the phase, or the time of arrival. Light always travels at the speed of light, so if the distance it travels is stretched, the time also increases, and the phase shifts.

A crude analogy: suppose you measure the height of a shelf by dropping a rubber ball and timing how long it takes to bounce back up to (nearly) the height it started. If you double the height of the shelf, the ball will take much longer to bounce up. If you also double the size of the ball , that will have much less of an effect.

In fact, what is being measured is not a “change in length”, but in a difference in change in length. That’s why you need the perpendicular beams of light. The gravity wave doesn’t change the dimensions of space time uniformly. It changes the “size” of space time in one direction only, perpendicular to the wave front. As the wave front passes, objects in one direction change in length, but objects perpendicular to that do not.

That’s mostly true, and it’s definitely important that we’re comparing two different lengths. I think it’s clearer, though, if you also think of this as measuring the travel time for light rather than thinking of light as a ruler. It’s the difference in travel times along the two arms that produces the phase shift.

(Technically, the wave changes distances in both directions. But it has opposite effects in perpendicular directions – it will first stretch one arm and shrink the other, then shrink the first and stretch the other, etc.)

I suppose it might be possible that if the wave front came in parallel to the plane defined by the two perpendicular beams of light, that the detector wouldn’t see them. Or, perhaps if it was in the same plane, but the direction of propagation was at 45 degrees to the right angle of the detector, that the legs might be deflected identical amounts. In either case, it seems to suggest that the detector would have varying sensitivity to the direction of the wave front.

That’s basically correct. The sensitivity is direction-dependent, and it’s maximum if the wave comes in perpendicular to the plane defined by the interferometer arms. Ultimately, when we have more detectors spread around the world, this may help in determining the direction of the source of a wave.

If you want more details, there’s a nice article by Peter Saulson in the American Journal of Physics, Am. J. Phys. 65, 501 (1997); http://dx.doi.org/10.1119/1.18578. There’s also a slightly more technical article at http://arxiv.org/abs/gr-qc/0702079, by Valerio Faraoni.

Many years ago, I remember an on-line debate between Tom van Flandern (now deceased, who was a genuine astronomer that got a little crazy in his later years) and Steve Carlip. Tom insisted that the Earth in its orbit around the Sun, was held in place by the force of gravitational attraction pointing to the true position of the Sun and not the optical image of the Sun. He concluded that the speed of gravity must therefore be infinite, or nearly so. No amount of explanation about static fields and reference frames could convince old Tom - he could not be persuaded that static fields don’t propagate at infinite speed.

Steve Carlip taught everyone about quadrapole fields (like gravity) and why we might expect them to propagate at the speed of light, rather than some other speed. He explained that gravity doesn’t propagate at the speed of light, but more precisely, changes in gravity propagate at the speed of light.

Someone asked Steve what would happen to the Earth if the Sun suddenly winked out of existence. First, Steve explained that the Sun can’t suddenly wink out of existence. Such things don’t happen in our Universe. But, if it did, then that change in gravity should propagate toward the Earth at the speed of light. The Earth would remain in its orbit for about 8 minutes before heading into Outer Space on a tangent trajectory.

That’s the story I remember, and I’m sticking to it.

Many thanks to Steve Carlip.

There is another concept that gets mentioned only occasionally; and that is the case where a sufficiently massive star with planets collapses into a black hole.

If there were simply a collapse without a giant burst of energy as a result of the “swallowing” of another object that tipped it over the threshold, the orbiting planets would not experience any change. The same mass that was the star is simply concentrated into a smaller radius.

However, collapsing into a black hole is usually a bit more complicated because before the collapse there is some process , e.g., nuclear fusion, that is producing an outward flow of energy that keeps material of the star from collapsing inward.

After the “nuclear fuel” runs out, fusion stops and collapsing begins with the result that a huge shockwave of rebounding material flows outward producing shockwave-fused elements that are heavier than the material that was fused within the star. Any orbiting planets would be destroyed and the gravitational field at the locations of the planets would be less because of the loss of material that gets blown off during the collapse. The remainder of the collapsing star, whether it goes to a neutron star or a black hole, will be less than that of the original star.

Isaac Newton was the first to calculate that the gravitational field of a spherical object could be taken as a point mass at the center of the object.

And while we are on this subject, you may have noticed that the two black holes that spiraled into each other had a total mass that was larger than the final black hole. This is the general rule in condensing matter; merging and bonding particles have less mass after they bind than before. This is what totally inelastic collisions are all about; and we can’t have condensing matter unless energy is spread around into the surrounding medium or space. In the case of merging black holes, most of that energy (mass) goes off in the form of gravitational waves.

This notion of the spreading around of energy is what ID/creationists never get. They think the second law of thermodynamics means that things come all apart and that entropy is disorder. All of ID/creationism’s calculations of the “improbability” of the formation of complex molecules are based on a profound ignorance of what a totally inelastic collision means.

Physics students in high school learn about elastic and inelastic collisions; and this is usually a point in the course in which the instructor or textbook gives a little “look-ahead” into the broader meanings of these concepts. In chemistry, high school students learn about endothermic and exothermic reactions and the conditions under which such reactions occur. Most students of chemistry have done the electrolysis of water and then get to ignite the gasses they collect. This is where they get introduced to the fact that it takes an input of energy to take compounds apart and energy comes out when compounds are formed.

Watching molten metal solidify, and feeling the heat coming off, is a dramatic demonstration of energy being spread around in order for atoms to bond into a solid.

Kids in middle school learn about the phases of matter; solid, liquid, gas, plasma.

As I look back on what is taught in the basic sciences in middle school and high school, I still find it amazing that students coming from sectarian backgrounds and becoming ID/creationists show absolutely no awareness of these concepts; and I am referring especially to the PhDs among them.

I remember wrestling with the notion of an event horizon. How could a black hole have any gravitational effect or electric charge outside the event horizon if all that mass and charge were inside? If gravity were mediated by gravitons traveling at the speed of light, how could they get outside the event horizon to be felt by ponderous objects on our side of it?

I had to ask a physicist. He explained to me that from a great distance, all the matter that goes inside the event horizon appears piled up just outside it, red shifted and apparently frozen in time. The mass and charge are there, on the surface of this “frozen star”, as Oppenheimer called it. (Yes, that Oppenheimer, of atomic bomb fame.)

Just inside the event horizon, because photons cannot get across it and get back outside, the event horizon (an imaginary surface) propagates outward at the speed of light. The properties of space-time are very different far from the black hole, at the event horizon, and inside it. Part of the difficulty is that physicists don’t know what exact set of equations they should use to model space-time in the vicinity of such strong gravity. I have read that time becomes space-like, and space becomes time-like, inside the event horizon. It all depends on the equations one uses to describe space-time.

Such mathematical physics is far beyond creationists, but it doesn’t stop them saying all scientists are wrong, except themselves.

Well, if it’s changes in gravity that propagate at the speed of light, instead of the gravity itself, then what’s “inside” the black hole doesn’t have to get out for it to exert gravitational force. The space-time is already curved, so to speak.

I’m a bit fuzzy on how that applies to electric charge if the black hole has a net charge.

Oh, here’s a thought, combining prong’s latest with Mike’s latest.

So, gravity (or changes in gravity) propagate at the speed of light. But light can’t escape a black hole. Yet, gravity (or the hypothetical graviton) can escape a black hole. I was just reading that in the 1/5 of a second it took for the two black holes to coalesce, about 3 solar masses were converted to and radiated away as gravitational energy in that 1/5 of a second, radiating about 50 times the energy of all the electromagnetic radiation of the rest of the entire universe in that fraction of a second.

Hmm… So, if light can’t escape a black hole, but gravity waves can, meaning that energy can escape a black hole, what (if anything) does that tell us about the nature of… nature?

It’s enough to stretch one’s mind, presumably in the direction of the gravity wave. :-)

Henry J said:

Well, if it’s changes in gravity that propagate at the speed of light, instead of the gravity itself, then what’s “inside” the black hole doesn’t have to get out for it to exert gravitational force. The space-time is already curved, so to speak.

I’m a bit fuzzy on how that applies to electric charge if the black hole has a net charge.

It also has a magnetic field too, doesn’t it?? Certainly neutron stars (pulsars) do, IIRC.

Apologies to all the actual physicists out there with all this ignorant neophyte flailing about, but it really is great fun to learn about such things.

It also has a magnetic field too, doesn’t it?? Certainly neutron stars (pulsars) do, IIRC.

Sure, if it has an electric force. Electric charge in motion + relativity effects -> magnetic force.

Scott F said:

It’s enough to stretch one’s mind, presumably in the direction of the gravity wave. :-)

What is quite remarkable is that much of this is self-contained in Einstein’s field equations which are expressed in a four-dimensional space-time.

It is difficult trying to visualize what these are saying; and most physicists, with the possible exception of Stephen Hawking who seems to see in higher dimensions, project out onto paper two dimensions of space and one dimension of time in order to work out what is going on. But that still doesn’t capture the entire picture.

Also, Einstein’s field equations are highly non-linear, with strong feedback between the amount of mass/energy density of space-time and the curvature of space-time. The physics is in those equations, but trying to visualize higher dimensions is a bit difficult. I keep trying, but my puny mind is only successful at doing this when I dream. I wake up and my ability to visualizing higher dimensions immediately evaporates.

One can look at the history of the development of relativity and get some understanding - from, say, special relativity - of the trend toward this kind of thinking. But the leap that Einstein took, though it was built on a lot of understanding that came before, was that of a genius. Nevertheless Einstein struggled to get there; and a lot of other folks then pitched in to start working out the implications. General relativity is a big field when one includes all the experimental activity that is being done to check out the theory.

But a theory that joins quantum mechanics with gravity still appears to be a ways off in the future. Interesting times.

Mike Elzinga said: I keep trying, but my puny mind is only successful at doing this when I dream. I wake up and my ability to visualizing higher dimensions immediately evaporates.

But are you sure you’re actually visualizing it in your dream, or are you only dreaming that you’re able to do it? When I was a kid I was often able to fly in my dreams ;-)

Just Bob said:

Mike Elzinga said: I keep trying, but my puny mind is only successful at doing this when I dream. I wake up and my ability to visualizing higher dimensions immediately evaporates.

But are you sure you’re actually visualizing it in your dream, or are you only dreaming that you’re able to do it? When I was a kid I was often able to fly in my dreams ;-)

Dreams are quite bizarre at times. Not only can I fly, I sometimes seem to be able to tunnel through space and time.

Once, after a major operation, I was still on the effects of pain meds and had a nightmare that I was being persued by people trying to kill me. I tried to hide by morphing into a large sheet of metal and slide myself under the bed of a pickup truck; but they found me and started twisting the truck about its axis. I woke up in panic.

Scott F said:

Oh, here’s a thought, combining prong’s latest with Mike’s latest.

So, gravity (or changes in gravity) propagate at the speed of light. But light can’t escape a black hole. Yet, gravity (or the hypothetical graviton) can escape a black hole. I was just reading that in the 1/5 of a second it took for the two black holes to coalesce, about 3 solar masses were converted to and radiated away as gravitational energy in that 1/5 of a second, radiating about 50 times the energy of all the electromagnetic radiation of the rest of the entire universe in that fraction of a second.

Hmm… So, if light can’t escape a black hole, but gravity waves can, meaning that energy can escape a black hole, what (if anything) does that tell us about the nature of… nature?

It’s enough to stretch one’s mind, presumably in the direction of the gravity wave. :-)

Actually Scott, the gravitons don’t escape the black hole. The gravitational effects of the black hole are felt by distant objects because all the mass inside the black hole (close up) is piled up just outside the event horizon (viewed from far away). So all the charge, and all the mass, continue to interact with our Universe. From afar, time for that matter seems to come to a standstill, or so I have read, so it never crosses the event horizon and enters the black hole.

At the event horizon, it appears that space-time itself is being sucked into the black hole at the speed of light. If that is indeed true, what happens to the zero-point energy of all that space-time. Is it also sucked inside? (How could it not?)

And does that energy drive the expansion of a new Universe formed out of all the matter and energy that collapsed initially into the black hole in our Universe? How could we ever know?

Is that what drives the expansion of our Universe? The black hole, in another Universe, from which we were formed?

It’s mind-bending. Physicists don’t need drugs, they have reality, black holes and all.

I wish I had another lifetime to study it, and become fluent in the equations of space-time.

prongs said:

Scott F said:

Oh, here’s a thought, combining prong’s latest with Mike’s latest.

So, gravity (or changes in gravity) propagate at the speed of light. But light can’t escape a black hole. Yet, gravity (or the hypothetical graviton) can escape a black hole. I was just reading that in the 1/5 of a second it took for the two black holes to coalesce, about 3 solar masses were converted to and radiated away as gravitational energy in that 1/5 of a second, radiating about 50 times the energy of all the electromagnetic radiation of the rest of the entire universe in that fraction of a second.

Hmm… So, if light can’t escape a black hole, but gravity waves can, meaning that energy can escape a black hole, what (if anything) does that tell us about the nature of… nature?

It’s enough to stretch one’s mind, presumably in the direction of the gravity wave. :-)

Actually Scott, the gravitons don’t escape the black hole. The gravitational effects of the black hole are felt by distant objects because all the mass inside the black hole (close up) is piled up just outside the event horizon (viewed from far away). So all the charge, and all the mass, continue to interact with our Universe. From afar, time for that matter seems to come to a standstill, or so I have read, so it never crosses the event horizon and enters the black hole.

Oh, no way. Seriously? I had not heard that one before. I was under the impression that all the matter just continued to scrunch down to the singularity, maybe getting turned into energy in the process.

But “time” for a photon is also at a standstill. Yet, the photon still moves relative to the rest of the universe. Wouldn’t matter continue on “into” the singularity?

And, here’s a thought. If angular momentum is also conserved, and all that mass with all that angular momentum is scrunched down to a singularity, how fast would the singularity (with a radius of zero) have to be spinning to conserve that same angular momentum? If the radius of the “singularity” were zero, then the angular momentum would disappear. Right? Presumably, the outer edge of the singularity could not be rotating faster than the speed of light, right? Would the conservation of angular momentum set a limit on how small the spinning singularity could be?

Nuts!!

At the event horizon, it appears that space-time itself is being sucked into the black hole at the speed of light. If that is indeed true, what happens to the zero-point energy of all that space-time. Is it also sucked inside? (How could it not?)

Doesn’t that contradict what you said above, that the “stuff” piles up on the event horizon? Not trying to be picky, I’m just trying to understand.

And does that energy drive the expansion of a new Universe formed out of all the matter and energy that collapsed initially into the black hole in our Universe? How could we ever know?

Is that what drives the expansion of our Universe? The black hole, in another Universe, from which we were formed?

It’s mind-bending. Physicists don’t need drugs, they have reality, black holes and all.

I wish I had another lifetime to study it, and become fluent in the equations of space-time.

Scott F said: Oh, no way. Seriously? I had not heard that one before. I was under the impression that all the matter just continued to scrunch down to the singularity, maybe getting turned into energy in the process.

This is all AIUI, but…

1. In its frame of reference, it does (continue on its way). In our frame of reference, it appears fixed. Just like with special relativity a fast-moving object appears frozen to us but to the moving object, time is passing normally.

2. Regardless of what happens inside each BH, its motions will warp spacetime outside of the event horizon too, and it’s that warping that we detect. Another example would be rotational frame dragging; another effect “of” the BH which changes the space outside of the event horizon.

But “time” for a photon is also at a standstill. Yet, the photon still moves relative to the rest of the universe.

3. The standard Lorentz transformations only work for particles with mass. For photons and other massless particles - which travel at c - I don’t think concepts like time dilation apply in the same way. There are equations that govern their motion and responses in high gravity fields, but I would be careful about trying to analogize their ‘viewpoint’ to that of (for example) a moving person; the analogy may not hold up.

And, here’s a thought. If angular momentum is also conserved, and all that mass with all that angular momentum is scrunched down to a singularity, how fast would the singularity (with a radius of zero) have to be spinning to conserve that same angular momentum? If the radius of the “singularity” were zero, then the angular momentum would disappear. Right? Presumably, the outer edge of the singularity could not be rotating faster than the speed of light, right? Would the conservation of angular momentum set a limit on how small the spinning singularity could be?

Nuts!!

4. I’m going more out on a limb here, but I believe prongs’ comment addresses this question: in our external frame of reference, the infalling black hole mass never reaches the singularity in any finite amount of time, so “what happens when it does” is not a problem.

At the event horizon, it appears that space-time itself is being sucked into the black hole at the speed of light. If that is indeed true, what happens to the zero-point energy of all that space-time. Is it also sucked inside? (How could it not?)

4. Energy is not strictly conserved under general relativity, so it wouldn’t be a problem. But even ignoring that, black holes radiate via quantum vacuum fluctuations in a way that obeys all the classical laws of thermodynamics. Also IIRC, this was the discovery/theory that put Stephen Hawking on the map; his demonstration that BHs can obey thermodynamics and his theory on how they do so is his big contribution to science.

And does that energy drive the expansion of a new Universe formed out of all the matter and energy that collapsed initially into the black hole in our Universe? How could we ever know?

5. We can’t know for sure, but I believe the notion that BH’s are ‘white holes’ in other universes is largely rejected by the physics community at this time, and relegated to science fiction. Mainstream physicists don’t believe the energy or mass has to go “somewhere” else for the system to work. Instead, as we understand them, black holes very slowly dissolve via quantum mechanical processes, so all their contained energy eventually makes it back into our universe.

It’s mind-bending. Physicists don’t need drugs, they have reality, black holes and all.

Agreed. :)

Hmm that was supposed to be a substantive reply but only one character made it through. I’ll try again later.

eric referenced:

Physicists don’t need drugs, they have reality, black holes and all.

Reality is stranger than fiction .… and also more interesting.

The next 100 years will be very interesting. Wish I could see them.

prongs said:

eric referenced:

Physicists don’t need drugs, they have reality, black holes and all.

Reality is stranger than fiction .… and also more interesting.

The next 100 years will be very interesting. Wish I could see them.

Yeah, I don’t think I’d like to live forever, but I’d sure like to see how things turn out. :-)

eric said:

2. Regardless of what happens inside each BH, its motions will warp spacetime outside of the event horizon too, and it’s that warping that we detect. Another example would be rotational frame dragging; another effect “of” the BH which changes the space outside of the event horizon.

Would it be possible, in principle, to tell anything about the inside of the BH by the nature of the changes outside the event horizon? Kind of like we do gravitational mapping of the inside of the Earth and other celestial bodies? Or would the event horizon essentially smear out or hide any kind of internal details like that?

And, here’s a thought. If angular momentum is also conserved, and all that mass with all that angular momentum is scrunched down to a singularity, how fast would the singularity (with a radius of zero) have to be spinning to conserve that same angular momentum? If the radius of the “singularity” were zero, then the angular momentum would disappear. Right? Presumably, the outer edge of the singularity could not be rotating faster than the speed of light, right? Would the conservation of angular momentum set a limit on how small the spinning singularity could be?

Nuts!!

4. I’m going more out on a limb here, but I believe prongs’ comment addresses this question: in our external frame of reference, the infalling black hole mass never reaches the singularity in any finite amount of time, so “what happens when it does” is not a problem.

Well… Hmm… What about the two black holes that coalesced to start this thread? Did one of them get “stuck” at the surface of the other, or vice versa? Do the equations that predicted the gravity waves predict what happens when the two black holes meet? Or do the solutions break down when one singularity meets another?

And of course, the mass of the star that initially collapsed to form that black hole would presumably be well below the event horizon.

The American Physical Society has put up a policy analysis based on the statements made by a House Republican during a scientific briefing of the LIGO discovery.

Lamar Smith’s (R - TX) introduction of a bill in the House of Representatives - a bill specifying that the NSF should fund only research that is “in the national interest” - appears to demonstrate the underlying hostility toward and ignorance of basic science among Republicans.

Such a bill would not only have prevented LIGO from even getting a start, it would have prevented the funding of the kind of work that Michael Faraday did.

One gets the impression that the Republican Party thinks that the only “research” that should be funded is the kind of research that will put far more money in their pockets right now than they spent on the research. No matter how many technological spin-offs from basic research they have around them and can hold in their hands, these characters never seem to be able to make the connection; even when it is repeatedly pointed out to them.

Scott F said:

prongs said:

eric referenced:

Physicists don’t need drugs, they have reality, black holes and all.

Reality is stranger than fiction .… and also more interesting.

The next 100 years will be very interesting. Wish I could see them.

Yeah, I don’t think I’d like to live forever, but I’d sure like to see how things turn out. :-)

I’d like to hear about the existence of a different life form.

The reconciliation of QM with GR.

The relationship between P and NP.

Understanding the Indus Valley Script.

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This page contains a single entry by Matt Young published on February 11, 2016 9:38 PM.

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