“Humanity has won its battle. Liberty now has a country.” -Marquis de Lafayette
There's so much science to talk about in any given week here at Starts With A Bang! It's sometimes hard to choose, but one particular topic stole the show this past week: black holes. Sure, we took on other things, too, but we didn't even talk all that much about the biggest discovery of all: LIGO's direct detection of a third pair of merging black holes! If you had doubts after one, and they were allayed after two, then three should hammer home that these are real, robust and common. There are a lot of nuances to talk about, so expect more ahead! In the meantime, here's a look back at the past week of stories:
- What does the edge of the Universe look like? (for Ask Ethan),
- Surprise! The Universe has a third way to form black holes (for Mostly Mute Monday),
- Is there really a cosmological constant? Or is dark energy changing with time? (an interesting look at a cosmic mismatch, by Sabine Hossenfelder),
- Nothing escapes from a black hole, and now astronomers have proof,
- Break the Standard Model? An ultra-rare decay threatens to do what the LHC can't, and
- What will the death of the Milky Way look like?
That was all my say, of course. What about yours? Let's dive in to what you had to add -- and what I can help out by clarifying, adding or delivering some bonus science to -- on this edition of our comments of the week!
Tweets from Evergreen State College and Professor Weinstein tell two very different stories.
From Denier on some disturbing political trends: "Please be careful with even handed statements like that. In your profession, especially in the Pacific Northwest, adopting a position any less screechy than outright vilification to paint the center and right as jackbooted Nazis can end your career. I’m sure you’re familiar with the Bernie-voting Biology Professor teaching about 2 hours up the road from you who dared to blaspheme by stating that it was wrong to discriminate based on skin color, and now is in fear for his life because students have labeled him as “anti-black”."
It's important to remember that no matter where you are on the political spectrum, there are going to be people forgetting the cardinal rule to freedoms of all types: your freedoms end when they infringe upon another's. Your freedom of anything -- of speech, of right to own property, to punch the air in front of your face -- end where another person's freedom, autonomy, right to exist, etc., begin. You don't get to banish someone from your campus, your city or your country because of their race, religion, perspectives or even their bigotry.
That said, less than two hours up the road from me, there are actual jackbooted Nazis marching today to spread a pro-Nazi message of fear, oppression, persecution and violence. I hope you are at least as vocal in your opposition of that as you are in your opposition to the students' treatment of Professor Weinstein.
The three valence quarks of a proton contribute to its spin, but so do the gluons, sea quarks and antiquarks, and orbital angular momentum as well. Image credit: APS/Alan Stonebraker.
From Elle H.C. on sea quarks: "The waves that the wings of a helicopter make are not wings, they are waves, even if these waves can ‘hit’ you hard.
So it does not seem correct to talk about the multitude of possible quark-formations."
No, deep inelastic scattering tells you what you actually hit. You can tell what the mass, charge, and even the lepton/baryon family is of the particle you hit. In your helicopter analogy, you don't hit wings or waves; you hit particles. Those may be helicopter blade particles, they may be air particles, they may be particles of other material in the air, but they are particles. Inside the proton, you can hit valence quarks, sea quarks, or gluons, and you can tell them apart. I am less interested in what seems correct to you than what the experimental data indicates. You can know.
Image credit: SpaceX / Elon Musk.
From eric on Mars plans: "I would think that a natural intermediate step would be to land automated heavy construction vehicles on the planet. Use them to build pits, walls, underground tunnels, etc. If you can’t safely land them, then you can’t safely land humans that would require the same tonnage. And if you can land them, then you should land them months or years before the humans arrive anyway, so that some basic environmental protection structures are already in place when the humans arrive."
We can always argue over how far we should go in an automated fashion before we send humans. I agree with you about some of these things. I would like to see us land heavy payloads softly, safely, accurately, and repeatably on Mars before we land crewed spacecraft there. But as far as having the protection structures already in place? I don't think that's necessary, particularly if it's easier to construct them with trained astronauts in situ than with a fully robotic/remote approach.
But no, I don't think we're far off from one another here, either.
Image credit: Mars One / Bryan Versteeg.
And from Sean T on what to fear if we fail: "You are absolutely correct: to accomplish the goal, an attempt must be made. I just fear that a single attempt may be all that we get, and that an expensive failure might well make a further attempt impossible politically."
Whenever we encounter setbacks, we have two ways to respond: to redouble our efforts and try again, or to give up out of fear and frustration. Believe it or not, I believe this is entirely a marketing problem, not a scientific one. If we can sell the idea of humans on Mars as something that's valuable enough, we'll go again even if we fail the first time... or the first few times. But we shall see.
From Narad on the Forbes not working problem: "I’m loathe to invoke this site, as the denizens generally have no idea what they’re talking about (e.g., the “solution” to everything always involves “repair permissions”), but the Forbes problem is not unknown."
It looks like this is a problem that occurred with some recent updates to both Forbes and Safari. Yes, there is probably a fundamental problem at play, and Forbes is exactly as committed to solving it as you'd expect. (They're aware of it, and that's the information I got.) If you can, use Chrome or Firefox, and things should load up just fine.
Artist's impression of a black hole. What goes on outside the black hole is well understood, but inside, we run up against the limits of fundamental physics... and potentially, the laws governing the Universe itself. Image credit: XMM-Newton, ESA, NASA.
From fred on what happens inside an event horizon: "Is it necessary that once escape velocity exceeds the speed of light that whatever lies behind the curtain must be a singularity as predicted by the maths?"
Only if all of physics is correct. If particles cannot be exchanged faster than the speed of light, then there would be no way to exert an "outward" force on anything inside the event horizon. And if you can't exert an outward force, there is no way to fight gravitational collapse down to a singularity. So it's only "necessary" to form a singularity if we take our current understanding of fundamental particle physics as correct. Of course, whether a "singularity" is actually something else in nature would require quantum gravity, but the "hard, solid object made of particles" interpretation has this problem regardless of quantum gravity.
Artist's logarithmic scale conception of the observable universe. Galaxies give way to large-scale structure and the hot, dense plasma of the Big Bang at the outskirts. This 'edge' is a boundary only in time. Image credit: Wikipedia user Pablo Carlos Budassi.
From PJ on what the edge of the Universe looks like: "Nicely & simply laid out, Ethan."
Thank you. I like the idea of an edge in time; after all, time is a dimension too. It seems like there's an incredible science fiction story in that idea... both in the past and in the future.
By the way, I thought I'd drop a little teaser for all of you here: you know that my first book, Beyond The Galaxy, is available everywhere (and up to 4.8 stars on Amazon), and that my second book, Treknology, is coming out in October and can be pre-ordered today. But what you haven't heard is that I'm currently planning my third book now (and yes, there's an idea for the fourth in the works, too), and it's going to be my first attempt at writing a book with no pictures. (To keep costs as low as possible, ostensibly.) I'm currently shopping agents for it, as it's a very different type of book, so if you have any recommendations, feel free to reach out!
The visible/near-IR photos from Hubble show a massive star, about 25 times the mass of the Sun, that has winked out of existence, with no supernova or other explanation. Direct collapse is the only reasonable candidate explanation. Image credit: NASA/ESA/C. Kochanek (tOSU).
From anneb on direct collapse black holes: "From the article, direct collapse is described as very plausible. However, during the collapse of the gas cloud, there must be a phase where nuclear fusion ignites a star."
Be very careful with words like 'must' in this context. For cases where you have objects under, say, a few hundred solar masses, yes, you will form a star where nuclear fusion ignites. That star may then undergo a variety of cataclysmic events that form a black hole, not all of which will result in a supernova. I'd be curious to learn if a "supernova impostor," like the type of event Eta Carinae underwent, could give rise to a black hole; perhaps in the next few hundred or thousand years, Eta Carinae itself will get another chance!
But in the case of much larger objects, you may not need fusion at all to get a direct collapse black hole. I don't think it's a necessary assumption, and I don't think anyone knows where the mass threshold is. But I wouldn't rule it out entirely, not just yet.
Although we've seen black holes directly merging three separate times in the Universe, we know many more exist. Image credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet).
From John on direct collapse and gravitational waves: "If the hypothesized direct collapse also left a distinct gravity wave signature that current and/or planned instruments could record, that would provide additional, independent corroboration."
I wish that were a good plan. Unfortunately, if you want to create a large-amplitude signal, you need a large mass moving rapidly through a rapidly changing gravitational field. The spherically symmetric nature of direct collapse makes that virtually impossible, and hence gravitational wave signatures from an event like this are expected to be very small in magnitude. (This is expected to be the case for supernovae, too.) However, neutron star "quakes," which correspond to pulsar timing "glitches," could be an example of a short-period transient signal that shows up in gravitational waves. The next generation of LIGO-like detectors might get there.
Additional details of interest provided by Michael Kelsey: "However, a spherically symmetric which undergoes an asymmetric explosion (i.e., one with a quadrupole moment) can generate gravitational waves.
In fact, one of LIGO’s search targets are the supernovae believed responsible for gamma-ray bursts, because the favored model of those involves a residual toroidal accretion disk which could have a sufficiently large quadrupole moment to emit GW."
The history of the Universe tells the story of a race between gravitation and expansion, until about six billion years ago, when dark energy becomes important. Image credit: NASA / GSFC.
From Frank on dark energy and energy conservation: "I think Dark Energy keeps increasing or even staying constant goes against conservation of energy/information because unit volume of spacetime must have constant amount of zero-point energy."
It's difficult to remember that in General Relativity, not only is global energy not conserved, it isn't defined. We can ad hoc a definition, as Sinisa Lazarek reminds us that I and Sean Carroll have pointed out, but that is not robustly true. If you must think of energy conservation for the Universe, you would do well to remember the Work-Energy theorem, and that Work is the "dot product" of a Force and a Distance. If you push outwards -- in the same direction -- as an expanding object, you do positive work; if you pull inwards -- in the opposite direction -- as an expanding object, you do negative work.
Your comment indicates that you have no problem with that second option for the Universe: the expansion is outward, gravity pulls inwards, and you do negative work on the expanding Universe. But what if the sign is reversed? Is energy conservation any less good? No. My point is that all of the viable options for dark energy are still valid, and your local notions of energy conservation are insufficient for restricting the physical options for global properties of dark energy. It could still increase or decrease in strength, but the evidence favors a constant value.
Against a seemingly eternal backdrop of everlasting darkness, a single flash of light will emerge: the evaporation of the final black hole in the Universe. Image credit: ortega-pictures / Pixabay.
From John on escaping a black hole: "“Nothing Escapes From A Black Hole, And Now Astronomers Have Proof”
Not even information?"
I had no idea that my title for this article -- which is about how an object getting swallowed by the event horizon doesn't have anything spit out again from inside on observable timescales -- would cause so many people to go 10^70-something years in the future and worry about black hole decay! I re-read the article and I don't think there's any ambiguity, so to clarify, on long enough timescales, black holes do decay away entirely, but that is still not anything (matter or energy) crossing from inside the horizon to outside.
If event horizons are real, then a star falling into a central black hole would simply be devoured, leaving no trace of the encounter behind. (If not, there would be some radical emissions outside the horizon with a 'splat'.) Image credit: Mark A. Garlick/CfA.
From Michael Kelsey on what was constrained, and how: "If black holes “don’t exist” (i.e., if there is some other simple compact object, like a super duper neutron star, which can provide the necessary gravitating mass in a small space), then there should/would be evidence for a surface of emission from such a compact object."
The alternative to an event horizon, which requires modifying General Relativity, would be a hard-surface at a radius greater than the radius of a predicted event horizon. The lack of evidence from Pan-STARRS indicates that the hard surface idea is heavily disfavored.
Image credit: KECK / UCLA Galactic Center Group / Andrea Ghez et al.
From Paul Dekous on the possibility that a black hole is not mass: "If a Galaxy is like a school of fish that swims around in loops, stirring up SpaceTime, than at the center of that whirlpool the friction and compression is the most intense, the distance between the top side going in the opposite direction of the bottom side is the smallest."
That's a cute analogy, but that's not what we observe. If anything like what you were describing were happening to space, then the orbits of stars would be perturbed from this classical, Keplerian path in a way other than classical GR predicts (i.e., precession of the perihelion of the orbits). There's a mass there, which theory and observation agree on, for our black hole and for many others.
In other words, we can rule out your idea.
From Michael Mooney on my self-contradictions: "The last reversal/ contradiction (from evaporating black holes to Friday’s headline) took 10 days. The switch only took two days this time. The rate of change Ethan’s opinion on black holes is accelerating!"
I have been writing about science on the internet for nearly ten years now, and one of the extraordinary lessons I've learned is there is nothing I can state, no matter how clearly, how supported by evidence, or how universally-agreed-upon, that won't result in me being told I'm wrong -- and, quite often, how awful I am in addition -- by someone. So what can I say to everyone who's done this?
The Milky Way, as we know it today, hasn't changed much in billions of years. But give it enough time, and eventually everything will disappear. Image credit: ESO/S. Guisard.
I see you. I recognize that you're doing your best to understand the world and Universe around you, and that sometimes you run into aspects of it that are challenging. Not only challenging to understand, but sometimes challenging to your own self-identity. The Universe gives us many difficult aspects to grapple with, and we don't always succeed at putting them into sensible order in our minds.
Well, don't give up. Keep trying. Keep challenging yourself, because that's what being alive is. Until it's time to die -- and that time is not yet here -- there's always more to learn, for all of us. Good luck on your journey, and I'll be here to share it with you if you still want to come along with me.
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If some stars are collapsing into a BH directly w/o exploding, could it be because spinning rates of those stars are lower than some threshold value? (Maybe that threshold also differs based on mass of the star.)
@Frank #1: Good physics intuition there!
As near as I can tell from a cursory search (via scholar.google.com and reading abstracts :-), that does indeed seem to be the underlying assumption/model. For example, one 2006 paper (https://academic.oup.com/mnras/article/370/1/289/1026607/Formation-of-s…) says, "Self-gravitating gas in dark matter haloes can lose angular momentum rapidly via runaway, global dynamical instabilities ...".
If you have such a system, it's supported only by gas and radiation pressure, and can end up in an unconstrained infall if sufficiently massive.
"precession of the perihelion of the orbits"
True.
But the idea of a whirlwind is still tempting if you look at the leafs going round in the following clip being pretty constant/consistent, caused by the boundaries of the setting and thus external limitation rather than an internal mass:
https://youtu.be/e_28Q_TTrBI
BTW a few extra remarks; why aren't those orbits more coplaner like the planets in our solar system, should't those stars align much more if there was indeed a massive object tying everything together?
How far can a BH pull on stars, isn't there a steep drop off, and how can it pull on SpaceTime if nothing can come out of a BH, shouldn't the 'gap' be detached from the grid?
"The alternative to an event horizon, which requires modifying General Relativity, would be a hard-surface at a radius greater than the radius of a predicted event horizon."
I am unclear on why it cannot be a solid core with radius smaller than event horizon? Couldn't it be even a liquid core? (If liquid it could even be same radius with event horizon, which I believe still not ruled out by observations.)
I think Ethan probably meant a solid code made of known particles would have a radius greater than the event horizon.
@Ethan wrote:
Ethan, this is just flat out incorrect. No part of that is even remotely true. Not only are you wrong but in addition you're also really awful. Like, on a 1 to 10 awful scale you're totally a 12.
@Ethan wrote:
I was having fun above telling you about your incorrectness, but if I understand quantum gravity correctly I see some problems in how you've phrased things. Please do tell me where I'm in error.
If Classical Physics held true all the way down you'd be right on the money but Quantum Gravity is the probabilistic movement of particles and has nothing to do with the warpage of space-time. With Quantum Gravity there is a direct outward path through space from the center to the horizon. No mass containing particle can escape a black hole because the probability of movement inward from the horizon to the center is 100% for all such particles.
The avenue opened by Quantum Gravity is that virtual particles can travel outward from the center just as if there were no gravity at all. They are just standing waves with no mass or energy of their own and so aren't affected by gravity..
My hope is that telescopes will get good enough to take an accurate inventory of the matter around a black hole in hopes it will become possible to deduce there is not enough matter in the accretion disc to account for the strength of the magnetic field driving its polar jets. I would love to see proof of virtual photons escaping in the form of an electromagnetic field.
If that is the case then game on. Information can be conveyed against the gravitational gradient and a super-dense ball can exist inside a black hole.
Ethan:
" I re-read the article and I don't think there's any ambiguity, so to clarify, on long enough timescales, black holes do decay away entirely, but that is still not anything (matter or energy) crossing from inside the horizon to outside."
The ones that are still "eating" will keep growing more massive. Who knows when their next meal will approach to within the gravitational field?
For black holes to "decay away entirely," the the proof you cited that "nothing escapes" must be ignored
. I see that you are perfectly comfortable with this proven falsification of "evaporation." (No problem tolerating cognitive dissonance, as with "well proven" cases of shrinking objects, depending on whom you ask... with no physics to verify it in the physical world.)
"I'll keep trying to explain the different aspects of black holes, and you are free to interpret the information I put out there however you like."
Thank you for the willingness to keep trying. Try to explain how mass inside a black hole escapes the inescapable gravity well... in Plain English... without math or imaginary particles immune to gravity.
" ...there is nothing I can state, no matter how clearly, how supported by evidence, or how universally-agreed-upon, that won't result in me being told I'm wrong."
Have you ever admitted that you were wrong?
Show us the evidence for Hawking radiation, not just speculative quantum theory with no evidence... or "tunneling" in cases which are not black holes.
(Not that I expect a reply anymore.)
@Paul Dekous #4: Several more corrections for you.
"why aren’t those orbits more coplaner like the planets in our solar system,"
Because they didn't form from a single collapsing cloud, the way the planets in our solar system did.
"should’t those stars align much more if there was indeed a massive object tying everything together?"
Not at all. The orbital plane is determined by the velocity vector of the hitherto _independent_ star as it gets captured. Picture something like a lacrosse player catching a ball in a net at the end of his stick. As the ball come in, the stick will swing backwards in the direction of the ball, defining an "orbital plane."
Since each one of those stars was captured independently, from some random direction in a big sphere, there's no reason for their orbits to be coplanar.
"How far can a BH pull on stars,"
All the way to infinity. F = GMm/r^2. Newton is your friend at large distances.
"isn’t there a steep drop off,"
No there isn't. F = GMm/r^2.
"and how can it pull on SpaceTime if nothing can come out of a BH,"
That's just word salad. Gravity is distortion of spacetime. The curved space around a black hole started out there before the black hole was (i.e., the original mass distribution formed the curved space around it; see again F = GMm/r^2). As the mass distribution collapses, the curved spacetime becomes visible outside of its surface. Once that collapse passes the event horizon, the curvature is already there. Nothing has to "come out".
"shouldn’t the ‘gap’ be detached from the grid?"
More word salad.
There is an interesting coordinate discontinuity at the event horizon, but it's not a true singularity. If you have the necessary mathematical background (basically, first year graduate level in physics or engineering), then you can take a look at the derivation of the Schwarzchild solution.
At the event horizon, there's a coordinate change where the coordinate which is radial outside changes phase, to become timelike (inward becomes futureward) inside the event horizon.
@Michael Kelsey #10,
On those stars not being coplaner:
"Because they didn’t form from a single collapsing cloud, the way the planets in our solar system did."
Galaxies form in the same way:
"This effect is due to conservation of angular momentum, and it's true for galaxies, too. This galaxy began life as a humongous ball of slowly rotating gas. Collapsing in upon itself, it spun faster and faster until, like pizza dough spinning and stretching in the air, a disc started to form."
--
"isn’t there a steep drop off?
No there isn’t. F = GMm/r^2."
Ok, M and m are the masses of the two objects, BH vs. orbiting star, but looking at the flip-side, away from the supposedly BH there are billions of stars masses as well making up the galaxy and pulling. Ironically a supermassive black hole has thousands to billions of solar masses just the same.
Is it that one BH curving those stars round into orbit, or are it those billions of stars on the outside, that make up the Galaxy, pulling those stars in the middle around like the leafs in a whirlwind.
Anyway lets agree that a star can be hooked and swing around a BH, but than it needs to be flying in from somewhere far away almost like a comet around the Sun, but also comets are coplaner while some of those in the clip should have had a perpendicular route.
@Paul Dekous #11: You quoted, "This effect is due to conservation of angular momentum, and it’s true for galaxies, too. This galaxy began life as a humongous ball of slowly rotating gas. Collapsing in upon itself, it spun faster and faster until, like pizza dough spinning and stretching in the air, a disc started to form.”
Did you notice the fourth word from the end? "Disc". That is the outer _DISK_ of a typical spiral galaxy, which is _outside_ the galactic bulge. The "bulge" is a nearly spherical accumulation of stars at the center of the galaxy, surrounding the black hole. "Spherical" means "non-coplanar".
You then wandered into a naive attempt at Machian philosophy, "are it those billions of stars on the outside, that make up the Galaxy, pulling those stars in the middle around like the leafs in a whirlwind."
I encourage you to look up Gauss' Law and go from there. It applies to gravitation just as well as to electrodynamics.
@Michael Kelsey #12,
Thanks for the term 'bulge'.
But look:
"Many bulges have properties more similar to those of the central regions of spiral galaxies than elliptical galaxies. They are often referred to as pseudobulges or disky-bulges. These bulges have stars that are not orbiting randomly, but rather orbit in an ordered fashion in the same plane as the stars in the outer disk. - https://en.wikipedia.org/wiki/Bulge_(astronomy)
So, hey, there are also disky-bulges!
Also thanks for the lead on Machian philosophy, there are some neat ideas about inertia.
I'm sure that some Bishop Berkeley will liven things up quite a bit.
@Narad #14,
Mh, I saw his name pop up as a predecessor on the Mach's page. Now I looked again, turnes out he's the guy after whom the named Berkeley in California … well what do you know.
https://en.wikipedia.org/wiki/George_Berkeley
"Berkeley argued against Sir Isaac Newton's doctrine of absolute space, time and motion in De Motu (On Motion), published 1721. His arguments were a precursor to the views of Mach and Einstein."
… and Paul Dekous' swimming fish. ?
Ethan,
A wave is like a Spring, a compressed spring is harder, but it is still the same spring, moving along or against the grain. So what you're measuring could be different compression states of the same spring, and not different particles.
And neither is completely analogous to the physics equations that govern subatomic particles.
When your analogy/metaphorical understanding predicts one behavior, and the physics/math predicts another, the physics/math wins. And it's fine in that case to say you don't understand. Analogies, metaphors, and qualitative discussions can only take you so far. You will never predict the behavior of subatomic particles with high accuracy by likening them to waves or springs or goats or anything else. To predict their behavior to high accuracy, you eventually have to learn to use, manipulate, and solve the actual equations that physicists attribute to them. Even that isn't perfect, but it's immensely more accurate than "like a wave" or "like a spring."
Eric,
I wasn't predicting anything. I was making a suggestion of how to interpret the results.
Ethan:
"... proving that nothing escapes from inside a black hole once you’ve been swallowed."
” I re-read the article and I don’t think there’s any ambiguity, so to clarify, on long enough timescales, black holes do decay away entirely, but that is still not anything (matter or energy) crossing from inside the horizon to outside."
Nothing escapes, but they still evaporate.
To be very clear... Ethan says that black holes do eventually "evaporate"... but he also says (and many physicists agree, me too, not a physicist)) that we have proof that nothing escapes from inside a black hole. (See the details of his post on that.)
In the field of psychology, "cognitive dissonance is the mental discomfort (psychological stress) experienced by a person who simultaneously holds two or more contradictory beliefs, ideas, or values." (Link available on request.)
I wonder if Ethan is feeling any mental discomfort over this round of contradictory statements. I'll probably never know, as he avoids addressing his own contradictory beliefs... and he considers me just a crank! (relativity critic just for openers.)
MM #19 If an accountant can get a handle it in concept, I have every confidence in the world you can too. Seriously, that profession is based almost entirely on 4th or 5th grade level math. How hard can it really be? Keep trying, we're all pulling for you. Well, I am, at any rate. I try to be optimistic.
MM
Like usual, the problem is with your understanding, not with the physics. There is no problem at all with the statement that black holes can evaporate AND nothing can escape from them. The problem is (once again) that you are trying to apply common sense intuition to a situation where such intuition fails and math is needed.
To see why it's not a contradiction, consider a black hole. If you were not aware, black holes can be electrically charged. Let's assume we have a black hole that is positively charged. If I told you that some time in the future, this same black hole would lose its electrical charge entirely, would this contradict the notion that nothing can escape it? It may seem so at first glance; how could the positive charge escape? However the solution is that the black hole could have gained negatively charged matter sufficient to neutralize the existing positive charge, thus becoming electrically neutral.
Now, here's where your intuition is insufficient. Something very similar is what occurs when a black hole evaporates. We are taught (and our intuition tells us) that there is no such thing as "negative mass". However, the mechanism of Hawking radiation, whereby a virtual particle pair forms with an event horizon separating them, gives rise to a situation that is far from intuitive. The math of quantum physics tells us that in such a situation, the virtual particle formed outside the event horizon should behave as an ordinary particle, with ordinary (positive) mass. The virtual particle forming inside the event horizon, though, behaves as though it has negative mass. Since it cannot escape and since it is forced to fall into the singularity, this negatively massed particle can "cancel" the positive mass that's already inside the black hole. Enough of these events (combined with a slow enough accretion of nearby normal matter) can cause a black hole's entire mass to be neutralized by the negatively massed virtual particles and hence evaporate.
This is (AFAIK) a purely theoretical prediction. I don't believe we have observed Hawking radiation experimentally, and likely we won't any time soon. Such events are very rare and the flux of radiation from such events would likely be well below the noise level for any imaginable method of measurement. However both QM and GR, upon which this phenomenon is based, are PERFECT at accounting for observational results. There is no reason to believe that they got it wrong WRT Hawking radiation. Hawking radiation may turn out to be nonexistent, but based on current knowledge and past records of the underlying theories, it's a good bet that Hawking radiation is real and that BH's do (eventually) evaporate.
Sean T,
If I misunderstand, so do some physicists who don't buy it. Here is an example:
http://gizmodo.com/no-scientists-didnt-just-create-negative-mass-or-def…
" 'Physicists created a negative effective mass', trusty physics debunk-blogger Sabine Hossenfelder writes in her Backreactions blog. Not a negative mass. Dropping the “effective” makes an enormous difference. And no, this lab-made atomic arrangement, similar to some other cold physics things we’ve covered before, does not explain black holes, the expanding universe, or any other weird phenomena of the cosmos."
The piece goes into detail on how the much-heralded/ published "discovery of negative mass" misinterprets the experimental results.
Btw, the "transcendence of common sense" which physicists and mathematicians are so proud of does not make mass vanish from within a black hole. Mass does not evaporate, and it still doesn't escape from black holes. Neither does light or other "mass-less" particles of radiation.
You wrote, " this negatively massed particle can “cancel” the positive mass that’s already inside the black hole."
"Cancel?" Like in math when a negative and a positive sign cancel each other? Math can not destroy mass.
" Enough of these events (combined with a slow enough accretion of nearby normal matter) can cause a black hole’s entire mass to be neutralized by the negatively massed virtual particles and hence evaporate."
And how is neutralized mass not still mass? Even I know that neutrons for instance have no charge but do have mass.
"This is (AFAIK) a purely theoretical prediction. I don’t believe we have observed Hawking radiation experimentally, and likely we won’t any time soon."
Not soon. Not ever. It is fantasy dressed up in math and called physics.
A physicist was asked (on a Q&A site), "Where does Hawking radiation go? Ans: "Nowhere. It stays in Hawking's head."
Yes pretty much. Two wavefunctions can interact in such a way that they 'cancel'. This is most obvious in the wavelike patterns photons can leave in a two-slit experiment, but can occur in other cases too.
Mass is destroyed all the time. If you don't think so, what's your explanation for the broad 511 keV peak in pretty much every gamma spectra ever taken?
eric,
As I understand it, when for instance an electron collides with a positron they *say* they "destroy each other" and call it annihilation radiation. Mass can clearly be converted to energy and dissipated, but that only *changes the form* of each. Neither quanta ceases to exist.
Neither does a "neutralized" particle, just because it has no +or- charge.
What sort of dressing do you prefer with your word salad?
MM,
You are very good at making assertions that a layperson would think sound very reasonable, but for which evidence is lacking. "Math cannot destroy mass" is one such. What is your evidence that mass cannot be destroyed? It is true that in MOST situations, mass is not destroyed, assuming that your definition of mass is really that of energy as used in physics. In MOST situations, energy cannot be destroyed. The situation near the event horizon of a black hole is quite atypical, however, and the rules that apply elsewhere simply do not hold there. You need the math to determine what the rules are in this situation, not just your unsubstantiated statements of intuition and/or common sense.
As for how neutralized mass is not mass, grant the assumption that negative mass exists. If an equal amount of negative mass and positive mass exists in a region of space, how much mass would an observer measure in that region? The answer can only be zero, much like the situation where there is an equal amount of negative and positive electrical charge in a region. Why is that confusing, other than that it is not something you'd ordinarily encounter. You have no problem with calling the neutron an uncharged particle despite the fact that it is composed of quarks that have equal and opposite charges. (Before you argue otherwise, this is experimentally confirmed. The magnetic moment of the neutron would not exist otherwise). Why would you not call a region of space with equal and oppositely signed masses a massless region?
Sean T,
Mass is energy in form. It can be redistributed but not destroyed, as in "cease to exist" in any form.
There is no evidence for black holes losing mass. The "rules" to which you refer regarding "the situation near the event horizon of a black hole" are all speculation, not known laws or "rules." All the evidence shows everything close to a bh being sucked in and nothing (even light) escaping.
I do not " grant the assumption that negative mass exists." See my link in #22.
Mass attracts mass, regardless of charge, and neutrons have mass but no overall charge, i.e.," neutral neutrons" as compared with positively charged protons. Their quark composite does not make them massless.
" Why would you not call a region of space with equal and oppositely signed masses a massless region?"
Seriously? A region WITH MASSES of opposite charge is MASSLESS? A blatant and obvious internal contradiction.
Suffering from cognitive dissonance?
Of course it's speculative. The conclusions of scientific theories that are not yet experimentally confirmed always are. That's not a negative. However the underlying theories have time and time again, even in the face of similar unsubstantiated statements such as what you make (e.g. "Time cannot pass at different rates for different observers because time is absolute), proven to be accurate when compared to experiment. You can personally take the predictions of GR and QM any way you want, but physicists WILL take such predictions seriously (not all of them of course, but the majority will). Seriously, but provisionally of course. If there is evidence that these predictions are wrong, then the physics community will behave accordingly. So far, though, the jury's out; there's no experimental evidence either in favor of or opposed to Hawking radiation. Therefore, the established theories will be taken seriously and thus so will Hawking radiation.
Your last post is chalk full of unsubstantiated statements. They ARE true for the most part, but you cannot seem to grasp that the event horizon of a black hole is not "the most part"; it's a whole different animal. "mass attracts mass, regardless of charge". "Mass can be redistributed but not destroyed" -- these are unsubstantiated statements in the region of a BH event horizon; they need to be shown to be true, not just assumed.
Finally, you admit that neutrons are chargeless, but physics tells us charges cannot be destroyed any more than masses can. You are aware, are you not, that the neutron actually is composed of charged components. Does that not mean that the neutron is charged? How could these component charges be destroyed? I admit, the idea of negative mass IS speculative, but ALL ideas in science are speculative at one time or another. If we only took seriously well-established science, then science could never advance. It may well turn out that the whole notion surrounding Hawking Radiation is completely wrong. We have to work to find that out, though. We just cannot, as you do, make some unwarranted assumptions and proclaim that it's false.
Just a historical aside:
If you had lived at various times in the past statements like "That heavy rock that you cannot lift is really mostly empty space", "The earth is really moving very rapidly through the universe despite the fact that you feel like you're standing still", "The stars are really very similar to our sun", "The continent that you are standing on is moving relative to the other continents", or "all the living organisms on the earth have a common ancestor" would have all been statements that you would have sneered at much the same way as you sneer at the idea of negative mass. Science does not advance by sneering at statements that seem silly; it advances by taking them seriously, working out their consequences and testing the universe to see if we can find evidence for them.
MM:
Do you understand that Hawking radiation converts the mass of a black hole into energy and dissipates it?
eric,
Do you understand that you are stating as a fact a theory with not only no evidence to support it but with recent evidence to falsify it?
"The anchor's been dropped but the crew keeps on rowing...
The breathing has stopped but the hair keeps on growing."
Jason Webley, troubadour.
Sean T,
So, you completely ignored your contradiction, that A region WITH MASSES of opposite charge is MASSLESS.
Btw, guilt by association with previous misconceptions in science is no argument at all.
Btw, I NEVER SAID what you quoted me as saying: "... similar unsubstantiated statements such as what you make (e.g. “Time cannot pass at different rates for different observers because time is absolute)"
(Aside)
Time is an agreed convention based on the "elapsed time" for movement of objects through space. Clocks tick at different rates after exposure to different forces... acceleration to different speeds and gravity differences. The day and year remain the standards for time as Earth rotates and orbits.
MM,
You were the one who referred to the neutron as chargeless. The neutron is NOT chargeless in the sense of containing no electrical charges. It is chargeless in precisely the same sense as equal and opposite masses being massless. Why can you grasp the idea in the case of electrical charge, but not in the case of mass? Undoubtedly, it's due to your experience and intuition. Those, necessarily, were formed here on earth. On earth, I agree, the idea that oppositely charged masses can cancel is absurd; there appears to be no such thing as negative mass. But, that's on earth, not at a black hole's event horizon. GR tells us that it's different there. Of course, there's no experimental evidence for this particular prediction of GR, but GR has been right time and time again, even when its predictions are extremely different from our intuition and experience.
BTW, what exactly is the difference between "time is absolute" as I wrote on the one hand and "The day and year remain the standards for time as the Earth rotates and orbits". They both are stating basically the same thing, and both are unwarranted assumptions that don't match the experimental evidence. Further, no forces are needed to "make clocks tick at different rates". The velocity of the clock relative to the spatial location of the two events whose duration is being measured is all that's needed for two clocks to give different times. That is as it must be. If you see two observers moving relative to one another, how can you determine which one was accelerated in the past and which one hasn't been? An observer moving at an appreciable fraction of light speed relative to you will indeed measure a longer time interval for a given event than you will. How do you know that this observer has accelerated to get to that speed, though, and that it's not you that has decelerated to get to your speed? Don't forget, we have velocities relative to all kinds of objects in the universe that we are completely unaware of. If it is you that decelerated rather than your counterpart who accelerated, why isn't your clock the one ticking more slowly?
Sean T.
You persist in talking nonsense such as "equal and opposite masses being massless." I confronted your contradiction and yet you deny that it is a contradiction. That conversation is over for my part.
You, and SR's "time dilation" in general ignore the history of each clock in order to claim that they "measure time" differently as they "pass through time" (not an entity) at different velocities. First, they don't "measure" anything (like a thermometer measures temperature or a barometer measures atmospheric pressure.) They just "tick" differently in the specific cases I cited above.
There is nothing "absolute" about the natural phenomena of Earth's rotation (one standard day) and its orbit (one standard year) now standardized to extreme precision by atomic clocks. The standard day and year as above (and their arbitrary sub-divisions) are not affected by clocks ticking at different rates.
That's enough of your hijacking this thread to promote the standard error of reification of time as well as "massless mass."
I'm out.
So "chargeless charge" is okay, but "massless mass" is not? The two are perfectly analogous, yet you're okay with one not the other. Why is that?
"I’m out."
Oh, if only you were telling the truth this time.
MM: I wasn't asserting Hawking radiation as some sort of philosophically absolute fact. I was pointing out that Hawking described a process that has the net result of converting mass into black body radiation. So you shouldn't have a problem with a BH's mass disappearing, because it's being converted into energy and you evidently accept that matter can be converted into energy.
It does bring up some questions about efficiency though. If a BH converting mass into black body radiation is thought of as an engine, what's it's efficiency, and what's the waste product? If it continues to convert mass to black body radiation with 100% efficiency (so long as it is supplied with mass), does that mean it's a type of perpetual motion machine?
And this is precisely the sort of Bad Fazzm that leads one to start babbling about how the Higgs field accounts for telepathy.
To recap Ethan's contradictory statements on black hole "evaporation" (via Hawking radiation) vs "nothing escapes a black hole":
First, Ethan denied the contradiction in reply to me, saying:
” I re-read the article and I don’t think there’s any ambiguity, so to clarify, on long enough timescales, black holes do decay away entirely, but that is still not anything (matter or energy) crossing from inside the horizon to outside.”
(They "decay away," but no matter or energy "crosses from inside the horizon to outside.")
From the two posts on the subject... all written by Ethan:
Title: Ask Ethan: What Happens When A Black Hole's Singularity Evaporates?
"One of the most puzzling things about Black Holes is that if you wait around long enough, they’ll evaporate completely."
"Given enough time, a black hole will decay away completely."
Title:
Nothing Escapes From A Black Hole, And Now Astronomers Have Proof
"In the meantime, we should celebrate the new evidence we have, and recognize what it means: when something falls into a black hole, there is no bounce-back, shattering, or ejecta from within. Once you slip past the event horizon, you're destined to fall all the way into the central singularity. As far as black holes go, there really is a point of no return."
Illustration caption "Inside a black hole (nothing escapes")
' proving that nothing escapes from inside a black hole once you’ve been swallowed."
Denial of the contradiction or "ambiguity" doesn't make it go away." On to several new subjects each week and let the above get buried in the archives and forgotten.
Helluva way to run a science forum.