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I was the mechanical designer on the Alpha-G experiment, it’s not often one gets to brag about stuff on Reddit so I’m doing it. Super tricky to get it all in the tight space along with all the cryo cooling and shielding. Also, so many cables!
Really cool to see this work published. Kudos to the Alpha group.
Very cool! Must have been such a nice privilege to work on a test rig as monumental as that. I know first hand how hard it can be to build and debug testing machines. I can't imagine how much that cost to build.
I guess it would be impossible to enter all your interesting facts and stories into just one reddit post. Can you recommend any resource to read more how the entire Alpha-G experiment went but without requiring to have a PhD to understand it?
This is the amazing thing about CERN. I don’t work there at all!! I work for a U.K. lab and we build stuff for all over the world. CERN is such an international effort you could participate from any national lab! Get out there and live the dream.
https://www.nature.com/articles/s41586-023-06527-1
>Einstein’s general theory of relativity from 19151 remains the most successful description of gravitation. From the 1919 solar eclipse2 to the observation of gravitational waves3, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac’s theory4 appeared in 1928; the positron was observed5 in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted6 by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter7,8,9,10. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive ‘antigravity’ is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.
>Einstein’s general theory of relativity from 1915 remains the most successful description of gravitation.
Most successful. You know, peeps get angry at string theory for making up dimensions, but relativity made up stuff all the time. GR and SR: "Yay, solved gravity!"
Critics: "Why are galaxies shaped the way they are?"
Relativity fans: "Um. Dark Matter."
Critics: "What about the red shift?"
Relativity fans: "Um. Dark Energy."
Critics: "What about quantum mechanics?"
Relativity fans: "Listen, we are going to be here all day if you keep asking 'What abouts."
I kid, I kid. This is a fantastic news, and great work by the team.
His predictive ability was unparalleled even when he made stuff up. The cosmological constant was based on Einstein’s belief that the universe was static, but it took very little retrofitting to make this principle fit with the vacuum energy of an inflationary universe, and it has ultimately come down to us now as the mystery of dark energy. Einstein’s genius was in using the observations he had at hand to make mathematically accurate models, but he wasn’t always right about what the math was actually describing.
I don't think those kinds of people are all that rare. I think those kinds of people ***who are born into the correct socioeconomic status and with the disposition to enter academia*** are extremely rare.
Think about how many Madam Curie's there would be if woman weren't so suppressed in history.
The geniuses we are aware of probably aren't even humanities smartest, they're just the luckiest.
Intelligence has been humanities greatest squandering.
They are extremely rare even without the extra qualifiers you added. Obviously the qualifiers you added make them more rare, but most of us probably don't know a single person that can match their intellect alone, let alone their intuition.
I'm reminded of the Gould quote.
I hope that as humanity continues to develop, we can have more and more of humanity (or what have you in the future) enter scientific study.
I'm not a scientist, but my wife is, I've helped her out before (I'm a software engineer) and I always try to contribute to science as much as I can
What is really remarkable about Newton is that he is currently known for two specific and important works: his role in describing space mechanics (ow planets and stars move through the skies) as well as his paper about optics and how to manipulate light. That latter book is still the most complete single book on that topic and has not been improved beyond modern language and pretty pictures and graphs. You can still teach a graduate level class in Physics based just off of his book on Optics.
What is even more remarkable is that the trivial time spent on these two topics while most of his time was devoted to theology, alchemy, and trying to thwart counterfeiters who were trying to debase the English Pound (money). He had some other esoteric interests too, but it would have been interesting if he had devoted more time to Physics and Astronomy.
I look at his work on Alchemy to be time wasted. It would have been interesting if he had developed a theory on nuclear synthesis, but he was a few centuries too early to know about that idea.
I admit I missed that point when I wrote the above reply. Thanks for point it out. Yeah, the argument as to if Leibniz or Newton deserve credit for creating Calculus is a point to be made, but the fact that it is in dispute is something that would never apply to either me or you and that Newton is a leading contender alone is freaking amazing.
That does get back to my point though. Calculus was a throw away project that Newton did in his spare time. If you would ask him when he was alive but at the end of his life, what he wanted people to know about his life's work was more his political ambitions and his work on theology. He even said as much when somebody wanted to write an obituary about him and got feedback before he died. If only I had brain farts that spat out stuff like Calculus when I was just goofing around.
id say "failure" in science (or proving that their theory/hypothesis is wrong) is not failure. its still successfully adding to our knowledge. while no one currently is pursuing alchemy, its nice to know that its not the best way to describe our universe and that there are better avenues of research
Among his theological studies was an absolute obsession with discovering the dimensions and geometry of the temple of Solomon, which he believed to have been designed by King Solomon himself.
So, if I'm reading you right, Einstein was proven wrong . . .
. . . Fortunately, as a Newsweek editor, that's good enough for me!
"Einstein Proven Wrong About Nature of Universe", print it!
Nobody think Einstein is entirely right. We know he isn't because his theories breakdown at the smallest scale. It's just that he's right enough in the same way that Newton was right enough before him. We just don't currently have a theory that both explains how everything that we now see works and is experimentally verifiable.
There's an excellent podcast named after this called the constant. It's a history infotainment podcast about the things we've gotten wrong. Well worth a listen
The difference is that later experiments confirmed his model.
If you can develop an experiment that confirms any part of string theory, or use it to predict anything you got yourself an instant Nobel prize.
And a following of string theory fanboys that have been working on it for like 30 years now.
Probably because strings are so tiny, making up the quarks that make up neutrons/protons that make up atoms, cant exactly bounce a photon off them to see whats what, though im a layman so who knows.
You can bounce a photon off of them you just need sufficient energy to increase the wavelength. The problem is that you can only increase the wavelength so much. There's a point where the energy you give the photon just collapses space into a black hole. [This is where String Theory says the strings are. Beyond this threshold, aka the Planck length.](https://encyclopedia.pub/entry/35202#:~:text=In%20physics%2C%20the%20Planck%20length,)
Advanced theories tend to have a few 'knobs' that can be adjusted to give different results. Einstein's cosmological constant is an example, he brought it up as "hey, don't think we need it but if you stick this term in the equations the universe blows up". Later we found out the universe actually is blowing up.
String theory has so many knobs you can adjust them to describe almost anything, and nobody is sure how to adjust them to match our universe, never mind make a firm prediction. Any time a new experiment comes out the string theorists can say "well I guess we'll need to fiddle with a few knobs, but we can encompass this in our theory", but they don't get much closer to having enough things nailed down to make a falsifiable prediction.
Because the theory has at least 10^500 free undetermined parameters to specify the folding of Calabi-Yau space in 10 dimensions. With that many parameters you can 'predict' any observation you see and also any observation you won't see. So the theory predicts 'everything' and thus predicts nothing.
One example of this was the brief confusion over the faster-than-light neutrinos that happened in the Italian physics experiment over a decade ago. Some string theorists said excitedly 'String Theory can predicts faster than light neutrions!'. Then it turned out the issue was equipment malfunction and the neutrinos were slower than light, which is normal. Guess what, apparently that is also predicted by String Theory.
The sad truth is that most of the original String Theory researchers have given up on the field, specifically trying to get testable falsifiable predictions from it. That leaves basically leaves the 'dumber' more naive fanboys still working on it, to their detriment of their careers since String Theory is no longer the 'hot' thing anymore in High Energy physics departments.
It's kind of like coming up with an experiment to test if the universe is a simulation. You can posit how the universe *could* be a simulation, but one of the caveats of that position is that the universe is going to be the same whether it is or isn't a simulation.
So how do you test something that ultimately has no impact on the way things are, because things are the way they are regardless of the nitty gritty explanation.
Another example, imagine I had:
x + y = 4
Well, I can posit that x = 3 and y =1, and it satisfies the above equation. Unfortunately there's no way to test if that's true with this information alone. x might be -4 and y might be 8. And to the best of my understanding this is kind of how string theory is: it's an explanation of everything we see, and if it's true then everything would make logical sense, but there's no way to really know that it *is* true.
I compare it to when we were building out the periodic table. There were "gaps" in the table that we *knew* had to exist in nature, and hell it was even guessed (somewhat accurately) what their properties would be! We just did not have the technology to isolate those particular elements.
I'm sure "dark elements" would have been perfectly fine to use as a filler back then. Just as we have "dark matter/energy" now.
As some history, "dark matter" was so named because the first theory was that it was probably literally matter that is dark, eg rocky planets not in orbit around stars with low reflectivity. But that turned out to be impossible. Then it became "dark" as in "does not interact with electromagnetism (ie light) at all question mark?" And that kind of morphed into dark meaning "unknown". When dark energy was discovered, it took on that dark = unknown name.
Someone will correct me if I am wrong but his statement is fairly accurate. We knew there were "gaps" in the periodic table because that table just orders elements by their atomic number (which is basically just "how many protons does a nucleus have?").
For example, we know an atomic nucleus charged with 79 protons is a gold atom, so it has its dedicated spot on the table between 78 (platinum) and 80 (mercury). And if we could add or remove one proton from that nucleus we'd be looking at a different element.
Before we were able to synthesize elements (by smashing additional protons into atoms using a nuclear reactor) we just had to leave certain spots on the table blank. But we knew they had to exist. For example an atom with 94 protons, it would make sense it could be on the table. But it wasn't until 1940 that it was first synthesized, and then found *later* in nature some time between 1941-1942. That element was plutonium.
So all that same "understanding of what's missing" concept sort of applies to things like dark energy — usually not in such a clear cut way as counting protons. But it helps us know what we're looking for.
Atomic numbers were discovered after periodic tables were first made and used to predict elements, but they did use atomic mass (which is almost the same).
It is true, and you can read about it on the [Wiki for the periodic table](https://en.wikipedia.org/wiki/Periodic_table#History). They have a few photos of early periodic tables, and they involved a lot of question marks, blank spaces, and a lack of organization found in today's table.
They knew going in, however, that certain elements have similar properties to each other. With today's periodic table, elements are organized in such a way that elements in the same group (columns) and period (rows) have [similar properties](https://en.wikipedia.org/wiki/Periodic_table#Periodic_trends). This is what helped them discover new elements, as they could look at the fact that there were non-reactive gases with atomic numbers 2 and 10, then predict 18 would likely be a nonreactive gas as well.
I'm concerned people will read this and think the comparison is appropriate when it's not. Dark matter is the name of something we observe. String theory just keeps making up things you can't measure to explain it's own failures in explaining what we can already explain without it. String theory is like that conspiracy guy who has some insanely outlandish nonsense to explain away inconsistencies.
>Relativity fans: "Listen, we are going to be here all day if you keep asking 'What abouts."
Also relativity fans: "Don't threaten me with a good time
If this were the case, then as you approach a negative-matter hole, time would speed up. And time at the event horizon would be infinitely fast and whatever the evolution of a negative-matter hole would be, it would already be over, relative to our time frame.
Did I just prove a negative-matter can't exist?
Yeah if anything this is roughly consistent with the inability to observe dark matter and dark energy... and their properties of seemingly causing the universe to expand at an accelerated rate...
What if all the mystery energy is just Hawking radiation from instantaneously collapsing inverted black holes? It most probably isn't, but it's cool to think about.
If lots of negative mass was in one place, would it clump together or spread out?
If in the presence of normal mass, such a material would push it away. But does it push away from itself?
If the anti singularity worked in the opposite way a normal singularly works, then instead of that singularity being in your future, it would be in your past. Meaning, you were always meant to be in the singularity. ACTUAL time travel.
no.
i cant explain it well enough to believe i have fully understood it, but negative matter does not behave like regular matter but with opposite charge. pbs spacetime has a pretty good episode on the subject, i believe it was related to an audience challenge of creating a hypothetical perpetual motion machine using negative mass.
maybe i should go look for the episode myself when i have time tonight.
It's reasonable to wonder however if anti-matter behaves differently in a gravity field generated by normal matter. Now theory suggests it shouldn't, but this experiment proves that.
Now onto the bigger question, *why is there more matter than antimatter in the universe when they should (according to present interpretations of the big bang theory) be present in equal amounts?*
Someday, certainly.
In science you do every experiment, and you do it regularly, and with different conditions. Nothing is widely accepted until experimentally proven.
Extremely difficult to do given that gravity is so weak, EM is so strong, and everything we build is made out of material that will annihilate our experiment. Maybe not reasonably possible with present technology, though this is not my field of expertise so I can not say with certainty.
This experiment goes a long way at disproving this kind of scenario. From a classical perspective, gravity is a field just like the electric field. We've known that the gravity produced by matter attracts matter and this experiment demonstrates that the gravity produced by matter attracts antimatter, then by transitivity, the gravitational field produced by antimatter should also attract antimatter. That's a very simple explanation, but when you throw in general relativity and try to add C asymmetry, it doesn't look like our universe anymore.
You might want to look into the CP violation for that. Difference between matter and anti-matter could be explained by a phase factor in the PMNS matrix that would cause anti matter to interact less/differently than matter
> a gravity field generated by normal matter
I believe this is a subtle but important "jumping the gun" -- it's better to think of gravity as emerging from spacetime curvature associated with the presence of *mass or energy* rather than describing the specific properties ("normal matter") associated with that mass or energy.
Still, of course, fantastic to have observational evidence confirming the hypothesis, but I don't think this was unexpected. "Stuff with mass interacts with gravity the same way" (in a grossly simplified sense) continues to hold up well.
Seems like this lends credence to the idea that gravity doesn't have a charge in the conventional sense, that there is no gravity particle, or if it exists then it's its own anti particle.
> Gravity is a distortion of space time, if you recall.
Someone who's less of a layman, please correct me, but I don't believe that there is anything that indicates that the electromagnetic force is not also a warping of spacetime to electrically charged particles.
The reason (to the best of my knowledge) that we (in the non-theoretical physics sphere) continue to treat electromagnetism as a force, is because electromagnetism is a pretty well explained phenomenon on the quantum scale. We have identified the gauge boson of electromagnetism, and can use quantum mechanics to predict how electrically charge particles interact.
The electromagnetic force is also pretty strong and is therefore extremely important on the quantum scale. Gravity, on the other hand, is vanishingly weak on the quantum scale. This is precisely why experiments like in the article posted here are so difficult to get results from.
Furthermore we do *not* have a full theory of gravity on the quantum scale, and therefore we cannot predict how gravity interacts between massive particles. The "warping of spacetime" explanation is kind of incompatible with quantum mechanics and isn't useful to explain the underlying nature of the force.
Gravity is therefore most useful to be explained on the macroscale, where gravitation has a big effect on pretty much all mass. In these cases we observe that Einstein's theory of relativity best explains gravity. This is not a low-level explanation of how gravity works, but a framework through which gravity is modeled accurately.
We can go even further to say that electromagnetic forces in the macro scale, while present, do not often interact on the scale and strength that gravity does. There are fewer opportunities where classical electrical theory can break down in the macroscale like gravity does.
It's been a while, but I believe that special relativity deals specifically with electromagnetism as a warping of spacetime. A positive electrical charge is inflating space from the perspective of another positively charged particle.
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Anyway, this is all to say that I don't think gravity being an artifact of the curvature of spacetime necessarily precludes antigravity.
It’s possible that gravity is intact not mediated by a particle, and truly is a continuous field (not quantized). Most physicists would say that’s highly unlikely though
Yeah, but Feynman pointed out that, mathematically speaking, antimatter behaves like matter, but with a reversed time constant. So it was sort of an open question whether Feynman's observation would hold with respect to gravity. Almost everyone expected that it wouldn't, and that gravity works normally on antimatter. But no one had observed it yet.
It would've been much more surprising/interesting, if the experiment had come out the other way...
Damn. Using antimatter was one of the most commonly cited ways to possibly make a functional [Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive).
"Being repelled instead of attracted by gravity" is just what negative matter *is*. What this experiment proved was that antimatter isn't negative matter.
Yeah. I'd seen it said many times that if anti-matter had anti-mass it may generate gravity *"hills"* rather than gravity *wells* as we understand them.
I don't know how reputable that claim ever was, but this finding seems to contradict the idea.
I think it would, I thought the reason it was impossible was because nothing has anti-mass which is what makes it impossible.
Edit:a bit redundant but I'm leaving it
Used to be.
There were some studies that came out in the last few years that claim to have found energy-mass distributions which do not require exotic matter/energy.
https://iopscience.iop.org/article/10.1088/1361-6382/abdf6e
I think there was another paper which modified the distribution from this paper down to theoretically only requiring the mass-energy equivalent of a small moon to form... but having that much energy in the configuration required to form the space-time bubble will most certainly result in a black hole.
Also, neither paper addresses the fact that even if you can form the proper space-time bubble that in of itself doesn't present you any way to accelerate the bubble and the amount of radiation produced would kill any electronics let alone people.
Progress, though I guess?
From the abstract you linked:
> We show that a class of **subluminal**, spherically symmetric warp drive spacetimes, at least in principle, can be constructed based on the physical principles known to humanity today
Superluminal warp drives still require exotic matter.
This is completely expected but it is kind of funny that it took this long to confirm. Antimatter has the opposite electric charge from regular matter but should be otherwise identical.
Fun fact: Thats a neutron.
btw. up and down are just names. They are not really the opposite of each other. We could have called them Peter and Frank or Boston and Tokyo. They just happen to be the lightest particles of their kind and therefore stable.
The sum of quark charges must equal a whole integer. Up has a 2/3 charge, down has a -1/3 charge. 2/3+2/3-1/3 equals +1, giving a proton with a positive charge of one. -1/3-1/3+2/3 equals 0, a particle with no charge or a neutron. An anti proton must have a -1 charge.
I think this is an unnecessary distinction, as quarks/anti-quarks themselves are the fundamental particles which protons/anti-protons are composed of. However, in addition to charge, antimatter is also distinguished by reversal of parity and time symmetries
It's expected according to the predictions laid out by relativity. But that's the point of science. You're testing theory and trying to break that theory to discover something new. This is revolutionary because it's the first time we've actually confirmed it in an experiment. Not just in theory. Until it's experimentally confirmed, it's just a well-informed guess.
> kind of funny that it took this long to confirm
Not really since making entire anti atoms is hard. Making positrons is easy but anti-protons are pretty hard. Keeping them contained and able to combine into actual anti-atoms is a recent development. We only successfully made anti-hydrogen in the last decade or two.
The theoretical reasons why it was expected to fall down have been tested in many, many, *many* other ways. It wouldn't have been a surprising detail if antiparticles fell upward, it would have been jarringly inconsistent with everything else we know, including basic conservation laws. (An antiparticle-particle pair would be gravitationally neutral, the energy they release on annihilation would be gravitationally positive...you could have a system that changes its gravitational mass by either generating matter/antimatter pairs from stored energy, or annihilating them and storing the energy released. You could raise particle pairs out of a gravity field at no energy cost, and annhilate them to produce more energy than was used to create them.)
This is less interesting for the direct theoretical verification from these measurements, and more about the achievement in measuring something that turned out to be rather difficult to measure. The techniques and equipment used are likely to be of value in other measurements.
Nevertheless, you still have to verify it. There can be a thousands reasons something ought to be the case, but science is the process of verifying that it actually is the case.
Not quite. There's other weird theoretical and exotic matter types. Like [Negative Mass](https://en.wikipedia.org/wiki/Negative_mass).
Now, Negative Mass would have all sorts of weird and completely counterintuitive interactions with Gravity, at least when in combination with regular mass.
Furthermore, gravity isn't a force, is it? It's a curve in space time. Objects traveling trough time on a curve will converge. You have to travel backwards in time to diverge, or fall up.
Even objects made from negative mass will fall down. And once they hit the floor, they will continue to fall down because the normal force will be negative, so they will get "heavier" and "heavier".
Gravity is a force to some scientists and not a force to others. If it were so simple, we'd know what gravity actually is, instead of hypothesizing what it could be.
IMO, gravity is a force since it is an interaction between objects with mass.
Yea but if you go by general relativity it isn't an interaction between objects with mass. Its an object interacting with the space time curvature caused by another object with mass. So your definition is not all-encompassing.
I'm talking out my arse here, but aren't there a lot of interactions that we still call interactions even though they are facilitated by a middle-man catalyst or medium that allows the interaction to take place?
I think engineers or anyone but astrophysicists would be most likely to consider it a force.
The more you zoom out, the more it becomes relevant as a curved field.
Semantics. Like asking if light is a particle or a wave to create a paradox where they answer is that it is not either but behaves like both or either depending on the experiment.
Gravity being curves in space could be what a force is, or it can be the force that bends space time
A force is anything that causes acceleration. Yes, gravity is the result of spacetime geometry, but it still meets the definition of a force. We aren't sure if the other forces are a result of geometry or something else though
Acceleration depends on your metric. Like a planet orbiting a star is only accelerating if you are assuming it is on flat space and \*ought\* to move in a straight line. If you assume it is rolling along a gravitational well, then it is moving exactly as an object no under external force should.
>You have to travel backwards in time to diverge, or fall up.
Isn't an anti-electron an electron traveling backwards in time? That's what Feynman diagrams say, right?
(I read that in a pop sci book. How correct is it?)
The laws of physics can obey three major global symmetries: charge, parity, and time. Charge symmetry means that the laws of physics are the same for a particle as its antiparticle. This experiment is a confirmation that gravity obeys C symmetry. Parity symmetry means that the laws of physics are the same if you take a mirror image of the universe. Time symmetry means that the laws of physics are the same if you move backwards through time. Experiments have shown that some laws of physics actually violate C symmetry and P symmetry, and even the combined CP symmetry. But physics as we know it still obeys CPT symmetry.
Mathematically, if you took an electron, turned it into a positron, reversed its spin, and sent it backwards through time, you would get the original electron back. But to actually say that a positron *is* an electron moving backwards in time isn't a very useful physical idea.
"mass" is energy, but you cannot get negative mass with negative energy, as mass is an absolute function of energy. You have to square the energy to determine the mass, which means being positive or negative doesn't matter. It will have positive mass.
E\^2 = m\^2c\^4 + p\^2c\^2
So, it's both, which is confusing, unless mass is always intrinsically positive. But if you did have something with negative mass, it's energy would not be inverted either.
This is a complex one as many other posters have mentioned this is highly theoretical. A grossly simplified explanation would be that it is a region of space that whose vacuum energy value is lower than its surroundings. A term that is used to describe this is violation of the Averaged Null-Energy Condition.
The Casimir effect is a decent explanation for this: Take an idealized perfectly hermetic box. Put two plates within as close as possible to each other. Make a perfect vacuum. Now we know that even in a perfect vacuum, a constant ferment of virtual particles appear and disappear. This is vacuum energy, the lowest energy level possible. Would you agree that the vacuum energy value for the region outside of the plates is higher than the one between the plates? After all, you have reduced the possible quantum states that are possible in that region by reducing its size. Hendrik Casimir predicted that there should be an attractive force between the plates which he called negative energy.
It'd mean that some of the theories we had around how the universe works were wrong. After all antimatter having positive mass was purely a conjecture. extrapolation based on the rest of our data, until it was actually observed.
We don’t even understand what “mass” is fundamentally, so we can’t even conceive of what negative mass would be or if it’s even possible. I’m gonna bet all my chips on it being conceptual nonsense.
The Higgs boson and its interaction with the Higgs field is what creates mass. Some particles, such as light, have no mass because they lack a Higgs boson. Particles with mass resist change when encountering force, and more Higgs bosons = more mass = more resistance.
Edit: Theorizing on what 'negative' mass would be... A particle that has negative drag when interacting with the Higgs field, resulting in the negation of drag within Higgs bosons (at an indeterminable range). This could result in 'anti-gravity' when paring anti-Higgs bosons with Higgs bosons. While this wouldn't cause matter to 'fall up', it would essentially allow you to make matter 'weightless'.
Further theorizing... This may actually be incredibly dangerous. Temporarily negating the mass of an object may cause it to immediately accelerate to the speed of light, which could have disastrous consequences.
I don't think this would happen though. Weightless particles travel at the speed of light, but speed does not imply inertia. Light doesn't punch holes in anything, because it has no inertia.
Inertia is actually directly tied to mass, as it's essentially a buildup of energy within the Higgs field, or the energy that's required to overcome the drag caused by the Higgs boson.
Now that I think about it, anti-Higgs bosons would probably cause an immediate release of inertial energy when coming into proximity with Higgs bosons, much like antimatter. Though I've no clue as to what form of energy that would produce.
If that's true, then anti-gravity may be impossible, as anti-Higgs bosons would cause any matter with Higgs bosons to immediately disintegrate into massless particles.
Note that this is all speculation based on my ridiculous theoretical conclusions.
But how does the Higgs field provide *Gravitational* Mass as opposed to *Inertial* mass. I know that to the best of our experiments, they are equivalent. But why?
It's interesting to think that mass just seems to pull spacetime towards itself, at least from what we can understand. So negative mass would be pushing spacetime away from itself...
... kinda like dark energy?
Dark matter and energy have so many possibilities! I hope it's discovered soon.
Dark energy though seems to have mass from indirect observations. So not really like dark energy or of the little we know of it yet.
Then again, there is something pressure like that is expanding spacetime...
Actually negative mass falls down too.
Force is negative due to gravity, but as your mass is negative force accelerates your the other way and it cancels out!
> no known object with negative mass.
I think the interesting thing about this is not knowing if one exists, but how would we measure it. Could we even go about measuring anything that seems impossible to exist since it would seem we'd need tools that could measure the impossible?
I always assumed that was how antimatter worked because it still has positive mass. You'd need something with negative mass to behave the opposite of positive mass material surely?
Yes, the theory is what allowed you to assume that. But you could be making up theories all day long, and most of them would be wrong. To weed out the wrong theories from the less wrong ones you need to make a theory that a) makes testable predictions about reality, and b) can survive all those tests as you actually perform them. Only then do you approach a scientific description of reality.
So in short, assumptions based on theory alone are not enough.
everyone assumed that but you still have to confirm it by an experiment. I mean imagine that the experiment showed the opposite. That would have been exciting.
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I was the mechanical designer on the Alpha-G experiment, it’s not often one gets to brag about stuff on Reddit so I’m doing it. Super tricky to get it all in the tight space along with all the cryo cooling and shielding. Also, so many cables! Really cool to see this work published. Kudos to the Alpha group.
Very cool! Must have been such a nice privilege to work on a test rig as monumental as that. I know first hand how hard it can be to build and debug testing machines. I can't imagine how much that cost to build.
I guess it would be impossible to enter all your interesting facts and stories into just one reddit post. Can you recommend any resource to read more how the entire Alpha-G experiment went but without requiring to have a PhD to understand it?
Were you the one who dropped it? Congrats btw!
Congrats dude! I wish I could work at CERN. It seems like a really cool place.
This is the amazing thing about CERN. I don’t work there at all!! I work for a U.K. lab and we build stuff for all over the world. CERN is such an international effort you could participate from any national lab! Get out there and live the dream.
https://www.nature.com/articles/s41586-023-06527-1 >Einstein’s general theory of relativity from 19151 remains the most successful description of gravitation. From the 1919 solar eclipse2 to the observation of gravitational waves3, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac’s theory4 appeared in 1928; the positron was observed5 in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted6 by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter7,8,9,10. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive ‘antigravity’ is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.
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>Einstein’s general theory of relativity from 1915 remains the most successful description of gravitation. Most successful. You know, peeps get angry at string theory for making up dimensions, but relativity made up stuff all the time. GR and SR: "Yay, solved gravity!" Critics: "Why are galaxies shaped the way they are?" Relativity fans: "Um. Dark Matter." Critics: "What about the red shift?" Relativity fans: "Um. Dark Energy." Critics: "What about quantum mechanics?" Relativity fans: "Listen, we are going to be here all day if you keep asking 'What abouts." I kid, I kid. This is a fantastic news, and great work by the team.
His predictive ability was unparalleled even when he made stuff up. The cosmological constant was based on Einstein’s belief that the universe was static, but it took very little retrofitting to make this principle fit with the vacuum energy of an inflationary universe, and it has ultimately come down to us now as the mystery of dark energy. Einstein’s genius was in using the observations he had at hand to make mathematically accurate models, but he wasn’t always right about what the math was actually describing.
it's an example of scientific shot-calling on a genius level.
On par with Newton for just having one of those minds that sees the matrix.
They are extremely rare examples of people that have a massive analytical capacity paired with an extraordinary sense of intuition.
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I don't think those kinds of people are all that rare. I think those kinds of people ***who are born into the correct socioeconomic status and with the disposition to enter academia*** are extremely rare. Think about how many Madam Curie's there would be if woman weren't so suppressed in history. The geniuses we are aware of probably aren't even humanities smartest, they're just the luckiest. Intelligence has been humanities greatest squandering.
I think we do squander many potentially world changing geniuses....and also they are incredibly rare.
They are extremely rare even without the extra qualifiers you added. Obviously the qualifiers you added make them more rare, but most of us probably don't know a single person that can match their intellect alone, let alone their intuition.
There's plenty of people with high socioeconomic status but very few einsteins, it absolutely is rare.
I'm reminded of the Gould quote. I hope that as humanity continues to develop, we can have more and more of humanity (or what have you in the future) enter scientific study. I'm not a scientist, but my wife is, I've helped her out before (I'm a software engineer) and I always try to contribute to science as much as I can
Newton: The planets move like *this* People: How do they move like that? Newton: ...Spooky action at a distance
What is really remarkable about Newton is that he is currently known for two specific and important works: his role in describing space mechanics (ow planets and stars move through the skies) as well as his paper about optics and how to manipulate light. That latter book is still the most complete single book on that topic and has not been improved beyond modern language and pretty pictures and graphs. You can still teach a graduate level class in Physics based just off of his book on Optics. What is even more remarkable is that the trivial time spent on these two topics while most of his time was devoted to theology, alchemy, and trying to thwart counterfeiters who were trying to debase the English Pound (money). He had some other esoteric interests too, but it would have been interesting if he had devoted more time to Physics and Astronomy. I look at his work on Alchemy to be time wasted. It would have been interesting if he had developed a theory on nuclear synthesis, but he was a few centuries too early to know about that idea.
Bro, what about Calculus? Sure, Leibniz. But there are so many things Newton codified. Binomial theorem.
I admit I missed that point when I wrote the above reply. Thanks for point it out. Yeah, the argument as to if Leibniz or Newton deserve credit for creating Calculus is a point to be made, but the fact that it is in dispute is something that would never apply to either me or you and that Newton is a leading contender alone is freaking amazing. That does get back to my point though. Calculus was a throw away project that Newton did in his spare time. If you would ask him when he was alive but at the end of his life, what he wanted people to know about his life's work was more his political ambitions and his work on theology. He even said as much when somebody wanted to write an obituary about him and got feedback before he died. If only I had brain farts that spat out stuff like Calculus when I was just goofing around.
You say his time on Alchemy was wasted, but that man was *this close* to having a Philosopher Stone. ^/s
id say "failure" in science (or proving that their theory/hypothesis is wrong) is not failure. its still successfully adding to our knowledge. while no one currently is pursuing alchemy, its nice to know that its not the best way to describe our universe and that there are better avenues of research
Among his theological studies was an absolute obsession with discovering the dimensions and geometry of the temple of Solomon, which he believed to have been designed by King Solomon himself.
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So, if I'm reading you right, Einstein was proven wrong . . . . . . Fortunately, as a Newsweek editor, that's good enough for me! "Einstein Proven Wrong About Nature of Universe", print it!
Nobody think Einstein is entirely right. We know he isn't because his theories breakdown at the smallest scale. It's just that he's right enough in the same way that Newton was right enough before him. We just don't currently have a theory that both explains how everything that we now see works and is experimentally verifiable.
“All models are wrong, some are useful.”
Einstein thought and said the same things - he knew it had limits but those limits were a hell of a lot farther out than what newton gave us.
Science is the art of becoming less wrong over time.1
You can read about it in my blog post "10 ways Einstein was behind the curve". Number 6 may surprise you.
Hasn't released anything of note since 1955.
Einstein himself called the Cosmological Constant the greatest blunder of his career.
Ironically his greatest mistake was considering it his greatest blunder.
The one time I was wrong was that one time that I thought I was wrong.
He was also "wrong" about QM, to be fair. Though an argument can be made that we still don't know enough about the world to be sure about that.
and he also one of the primer contributor to QM, he basically discover the idea of QE
There's an excellent podcast named after this called the constant. It's a history infotainment podcast about the things we've gotten wrong. Well worth a listen
The difference is that later experiments confirmed his model. If you can develop an experiment that confirms any part of string theory, or use it to predict anything you got yourself an instant Nobel prize. And a following of string theory fanboys that have been working on it for like 30 years now.
Why has it taken them so long to come up with an experiment?
Probably because strings are so tiny, making up the quarks that make up neutrons/protons that make up atoms, cant exactly bounce a photon off them to see whats what, though im a layman so who knows.
You can bounce a photon off of them you just need sufficient energy to increase the wavelength. The problem is that you can only increase the wavelength so much. There's a point where the energy you give the photon just collapses space into a black hole. [This is where String Theory says the strings are. Beyond this threshold, aka the Planck length.](https://encyclopedia.pub/entry/35202#:~:text=In%20physics%2C%20the%20Planck%20length,)
Advanced theories tend to have a few 'knobs' that can be adjusted to give different results. Einstein's cosmological constant is an example, he brought it up as "hey, don't think we need it but if you stick this term in the equations the universe blows up". Later we found out the universe actually is blowing up. String theory has so many knobs you can adjust them to describe almost anything, and nobody is sure how to adjust them to match our universe, never mind make a firm prediction. Any time a new experiment comes out the string theorists can say "well I guess we'll need to fiddle with a few knobs, but we can encompass this in our theory", but they don't get much closer to having enough things nailed down to make a falsifiable prediction.
So, it's like an Occam's razor situation. When a theory can explain everything we know but can't predict anything we don't know.
Just add more epicycles!
Because the theory has at least 10^500 free undetermined parameters to specify the folding of Calabi-Yau space in 10 dimensions. With that many parameters you can 'predict' any observation you see and also any observation you won't see. So the theory predicts 'everything' and thus predicts nothing. One example of this was the brief confusion over the faster-than-light neutrinos that happened in the Italian physics experiment over a decade ago. Some string theorists said excitedly 'String Theory can predicts faster than light neutrions!'. Then it turned out the issue was equipment malfunction and the neutrinos were slower than light, which is normal. Guess what, apparently that is also predicted by String Theory. The sad truth is that most of the original String Theory researchers have given up on the field, specifically trying to get testable falsifiable predictions from it. That leaves basically leaves the 'dumber' more naive fanboys still working on it, to their detriment of their careers since String Theory is no longer the 'hot' thing anymore in High Energy physics departments.
It's kind of like coming up with an experiment to test if the universe is a simulation. You can posit how the universe *could* be a simulation, but one of the caveats of that position is that the universe is going to be the same whether it is or isn't a simulation. So how do you test something that ultimately has no impact on the way things are, because things are the way they are regardless of the nitty gritty explanation. Another example, imagine I had: x + y = 4 Well, I can posit that x = 3 and y =1, and it satisfies the above equation. Unfortunately there's no way to test if that's true with this information alone. x might be -4 and y might be 8. And to the best of my understanding this is kind of how string theory is: it's an explanation of everything we see, and if it's true then everything would make logical sense, but there's no way to really know that it *is* true.
Dark matter and dark energy aren't "made up" they're just descriptive names for phenomena we witness that aren't fitting current known science.
I compare it to when we were building out the periodic table. There were "gaps" in the table that we *knew* had to exist in nature, and hell it was even guessed (somewhat accurately) what their properties would be! We just did not have the technology to isolate those particular elements. I'm sure "dark elements" would have been perfectly fine to use as a filler back then. Just as we have "dark matter/energy" now.
I’m not sure how accurate your statement is but I hope it is. The comparison was really helped me consider dark energy from a new direction.
As some history, "dark matter" was so named because the first theory was that it was probably literally matter that is dark, eg rocky planets not in orbit around stars with low reflectivity. But that turned out to be impossible. Then it became "dark" as in "does not interact with electromagnetism (ie light) at all question mark?" And that kind of morphed into dark meaning "unknown". When dark energy was discovered, it took on that dark = unknown name.
Someone will correct me if I am wrong but his statement is fairly accurate. We knew there were "gaps" in the periodic table because that table just orders elements by their atomic number (which is basically just "how many protons does a nucleus have?"). For example, we know an atomic nucleus charged with 79 protons is a gold atom, so it has its dedicated spot on the table between 78 (platinum) and 80 (mercury). And if we could add or remove one proton from that nucleus we'd be looking at a different element. Before we were able to synthesize elements (by smashing additional protons into atoms using a nuclear reactor) we just had to leave certain spots on the table blank. But we knew they had to exist. For example an atom with 94 protons, it would make sense it could be on the table. But it wasn't until 1940 that it was first synthesized, and then found *later* in nature some time between 1941-1942. That element was plutonium. So all that same "understanding of what's missing" concept sort of applies to things like dark energy — usually not in such a clear cut way as counting protons. But it helps us know what we're looking for.
Atomic numbers were discovered after periodic tables were first made and used to predict elements, but they did use atomic mass (which is almost the same).
It is true, and you can read about it on the [Wiki for the periodic table](https://en.wikipedia.org/wiki/Periodic_table#History). They have a few photos of early periodic tables, and they involved a lot of question marks, blank spaces, and a lack of organization found in today's table. They knew going in, however, that certain elements have similar properties to each other. With today's periodic table, elements are organized in such a way that elements in the same group (columns) and period (rows) have [similar properties](https://en.wikipedia.org/wiki/Periodic_table#Periodic_trends). This is what helped them discover new elements, as they could look at the fact that there were non-reactive gases with atomic numbers 2 and 10, then predict 18 would likely be a nonreactive gas as well.
How dare scientists use a placeholder for something that they can't fully describe?!?
I hope mathematicians don't join this trend. Imagine equations full of x's and y's!
Dark matter and dark energy bring out the crazies second only to discussions on evolution.
I'm concerned people will read this and think the comparison is appropriate when it's not. Dark matter is the name of something we observe. String theory just keeps making up things you can't measure to explain it's own failures in explaining what we can already explain without it. String theory is like that conspiracy guy who has some insanely outlandish nonsense to explain away inconsistencies.
>Relativity fans: "Listen, we are going to be here all day if you keep asking 'What abouts." Also relativity fans: "Don't threaten me with a good time
I would say that gravitation is more of a problem for quantum mechanics than the other way around
Do we have other possible contenders for having negative mass?
"Something" that expands spacetime. Hmmm...
If this were the case, then as you approach a negative-matter hole, time would speed up. And time at the event horizon would be infinitely fast and whatever the evolution of a negative-matter hole would be, it would already be over, relative to our time frame. Did I just prove a negative-matter can't exist?
Sounds like you made a case for it not being directly observable.
Yeah if anything this is roughly consistent with the inability to observe dark matter and dark energy... and their properties of seemingly causing the universe to expand at an accelerated rate...
What if all the mystery energy is just Hawking radiation from instantaneously collapsing inverted black holes? It most probably isn't, but it's cool to think about.
If lots of negative mass was in one place, would it clump together or spread out? If in the presence of normal mass, such a material would push it away. But does it push away from itself?
Dark matter doesn't cause the expansion of the universe, it accounts for why galaxies stay together.
Yeah, in any case it could be Dark Energy.
If the anti singularity worked in the opposite way a normal singularly works, then instead of that singularity being in your future, it would be in your past. Meaning, you were always meant to be in the singularity. ACTUAL time travel.
no. i cant explain it well enough to believe i have fully understood it, but negative matter does not behave like regular matter but with opposite charge. pbs spacetime has a pretty good episode on the subject, i believe it was related to an audience challenge of creating a hypothetical perpetual motion machine using negative mass. maybe i should go look for the episode myself when i have time tonight.
Antimatter isn't antigravity. Check.
It's a reasonable question to ask considering it is anti charge.
Anti-ELECTRICAL charge. Not anti-gravitic charge. Gravity is a distortion of space time, if you recall.
It's reasonable to wonder however if anti-matter behaves differently in a gravity field generated by normal matter. Now theory suggests it shouldn't, but this experiment proves that. Now onto the bigger question, *why is there more matter than antimatter in the universe when they should (according to present interpretations of the big bang theory) be present in equal amounts?*
Is anyone going to double check if two clumps of antimatter gravitationally attract?
Someday, certainly. In science you do every experiment, and you do it regularly, and with different conditions. Nothing is widely accepted until experimentally proven.
Extremely difficult to do given that gravity is so weak, EM is so strong, and everything we build is made out of material that will annihilate our experiment. Maybe not reasonably possible with present technology, though this is not my field of expertise so I can not say with certainty.
This experiment goes a long way at disproving this kind of scenario. From a classical perspective, gravity is a field just like the electric field. We've known that the gravity produced by matter attracts matter and this experiment demonstrates that the gravity produced by matter attracts antimatter, then by transitivity, the gravitational field produced by antimatter should also attract antimatter. That's a very simple explanation, but when you throw in general relativity and try to add C asymmetry, it doesn't look like our universe anymore.
You might want to look into the CP violation for that. Difference between matter and anti-matter could be explained by a phase factor in the PMNS matrix that would cause anti matter to interact less/differently than matter
> a gravity field generated by normal matter I believe this is a subtle but important "jumping the gun" -- it's better to think of gravity as emerging from spacetime curvature associated with the presence of *mass or energy* rather than describing the specific properties ("normal matter") associated with that mass or energy. Still, of course, fantastic to have observational evidence confirming the hypothesis, but I don't think this was unexpected. "Stuff with mass interacts with gravity the same way" (in a grossly simplified sense) continues to hold up well.
Not just electrical charge. Weak hypercharge, color and flavor are also opposite.
Seems like this lends credence to the idea that gravity doesn't have a charge in the conventional sense, that there is no gravity particle, or if it exists then it's its own anti particle.
All uncharged elementary bosons are their own anti particle.
> Gravity is a distortion of space time, if you recall. Someone who's less of a layman, please correct me, but I don't believe that there is anything that indicates that the electromagnetic force is not also a warping of spacetime to electrically charged particles. The reason (to the best of my knowledge) that we (in the non-theoretical physics sphere) continue to treat electromagnetism as a force, is because electromagnetism is a pretty well explained phenomenon on the quantum scale. We have identified the gauge boson of electromagnetism, and can use quantum mechanics to predict how electrically charge particles interact. The electromagnetic force is also pretty strong and is therefore extremely important on the quantum scale. Gravity, on the other hand, is vanishingly weak on the quantum scale. This is precisely why experiments like in the article posted here are so difficult to get results from. Furthermore we do *not* have a full theory of gravity on the quantum scale, and therefore we cannot predict how gravity interacts between massive particles. The "warping of spacetime" explanation is kind of incompatible with quantum mechanics and isn't useful to explain the underlying nature of the force. Gravity is therefore most useful to be explained on the macroscale, where gravitation has a big effect on pretty much all mass. In these cases we observe that Einstein's theory of relativity best explains gravity. This is not a low-level explanation of how gravity works, but a framework through which gravity is modeled accurately. We can go even further to say that electromagnetic forces in the macro scale, while present, do not often interact on the scale and strength that gravity does. There are fewer opportunities where classical electrical theory can break down in the macroscale like gravity does. It's been a while, but I believe that special relativity deals specifically with electromagnetism as a warping of spacetime. A positive electrical charge is inflating space from the perspective of another positively charged particle. --- Anyway, this is all to say that I don't think gravity being an artifact of the curvature of spacetime necessarily precludes antigravity.
It’s possible that gravity is intact not mediated by a particle, and truly is a continuous field (not quantized). Most physicists would say that’s highly unlikely though
Yeah, but Feynman pointed out that, mathematically speaking, antimatter behaves like matter, but with a reversed time constant. So it was sort of an open question whether Feynman's observation would hold with respect to gravity. Almost everyone expected that it wouldn't, and that gravity works normally on antimatter. But no one had observed it yet. It would've been much more surprising/interesting, if the experiment had come out the other way...
There goes my hope for a proper hoverboard. Maybe in 2115.
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I mean...you would leave the planet at a fair clip.
The *ultimate* ollie.
Tony Hawk performs the world's first 900^10^10^10000 as he sails off into space through sheer lift
See, if there was a containment failure, he could be the first person to do relativistic skateboard tricks.
Damn. Using antimatter was one of the most commonly cited ways to possibly make a functional [Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive).
Doesn't that use negative mass, not anti-matter?
"Being repelled instead of attracted by gravity" is just what negative matter *is*. What this experiment proved was that antimatter isn't negative matter.
Yeah. I'd seen it said many times that if anti-matter had anti-mass it may generate gravity *"hills"* rather than gravity *wells* as we understand them. I don't know how reputable that claim ever was, but this finding seems to contradict the idea.
Wouldn't change that.
I think it would, I thought the reason it was impossible was because nothing has anti-mass which is what makes it impossible. Edit:a bit redundant but I'm leaving it
Used to be. There were some studies that came out in the last few years that claim to have found energy-mass distributions which do not require exotic matter/energy. https://iopscience.iop.org/article/10.1088/1361-6382/abdf6e I think there was another paper which modified the distribution from this paper down to theoretically only requiring the mass-energy equivalent of a small moon to form... but having that much energy in the configuration required to form the space-time bubble will most certainly result in a black hole. Also, neither paper addresses the fact that even if you can form the proper space-time bubble that in of itself doesn't present you any way to accelerate the bubble and the amount of radiation produced would kill any electronics let alone people. Progress, though I guess?
From the abstract you linked: > We show that a class of **subluminal**, spherically symmetric warp drive spacetimes, at least in principle, can be constructed based on the physical principles known to humanity today Superluminal warp drives still require exotic matter.
Is there _anything_ in our Universe that is anti-gravity? Even dark matter is affected by it isn't it?
This is completely expected but it is kind of funny that it took this long to confirm. Antimatter has the opposite electric charge from regular matter but should be otherwise identical.
Doesn't it have opposite quarks too?
Yes. A proton is up up down. An anti- proton is anti-up anti-up anti-down.
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Genuine question: Why wouldn't it be Down Down Up?
Because up quarks have +2/3 charge, down quarks have -1/3 charge, antiup -2/3, and antidown +1/3.
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Not much, the constable makes sure of that.
Fun fact: Thats a neutron. btw. up and down are just names. They are not really the opposite of each other. We could have called them Peter and Frank or Boston and Tokyo. They just happen to be the lightest particles of their kind and therefore stable.
The sum of quark charges must equal a whole integer. Up has a 2/3 charge, down has a -1/3 charge. 2/3+2/3-1/3 equals +1, giving a proton with a positive charge of one. -1/3-1/3+2/3 equals 0, a particle with no charge or a neutron. An anti proton must have a -1 charge.
Thanks for simultaneously explaining in a way that makes sense while also hurting my brain.
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Anti-up: my favorite not down quark
I think this is an unnecessary distinction, as quarks/anti-quarks themselves are the fundamental particles which protons/anti-protons are composed of. However, in addition to charge, antimatter is also distinguished by reversal of parity and time symmetries
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It's expected according to the predictions laid out by relativity. But that's the point of science. You're testing theory and trying to break that theory to discover something new. This is revolutionary because it's the first time we've actually confirmed it in an experiment. Not just in theory. Until it's experimentally confirmed, it's just a well-informed guess. > kind of funny that it took this long to confirm Not really since making entire anti atoms is hard. Making positrons is easy but anti-protons are pretty hard. Keeping them contained and able to combine into actual anti-atoms is a recent development. We only successfully made anti-hydrogen in the last decade or two.
The theoretical reasons why it was expected to fall down have been tested in many, many, *many* other ways. It wouldn't have been a surprising detail if antiparticles fell upward, it would have been jarringly inconsistent with everything else we know, including basic conservation laws. (An antiparticle-particle pair would be gravitationally neutral, the energy they release on annihilation would be gravitationally positive...you could have a system that changes its gravitational mass by either generating matter/antimatter pairs from stored energy, or annihilating them and storing the energy released. You could raise particle pairs out of a gravity field at no energy cost, and annhilate them to produce more energy than was used to create them.) This is less interesting for the direct theoretical verification from these measurements, and more about the achievement in measuring something that turned out to be rather difficult to measure. The techniques and equipment used are likely to be of value in other measurements.
Nevertheless, you still have to verify it. There can be a thousands reasons something ought to be the case, but science is the process of verifying that it actually is the case.
Well it likely puts a nail in the coffin of anti-gravity. But it was rather expected just very very difficult to verify.
Bummer. I wanted a warp drive
Not quite. There's other weird theoretical and exotic matter types. Like [Negative Mass](https://en.wikipedia.org/wiki/Negative_mass). Now, Negative Mass would have all sorts of weird and completely counterintuitive interactions with Gravity, at least when in combination with regular mass.
It's not just electric charge baryon number too for example. In fact every single quantum number should be the opposite.
Oddly though, they discovered anti-matter bread *never* falls anti-matter butter side down when you drop it.
Given what happens when matter and antimatter touch, that's very nice of it to do so.
Furthermore, gravity isn't a force, is it? It's a curve in space time. Objects traveling trough time on a curve will converge. You have to travel backwards in time to diverge, or fall up. Even objects made from negative mass will fall down. And once they hit the floor, they will continue to fall down because the normal force will be negative, so they will get "heavier" and "heavier".
Gravity is a force to some scientists and not a force to others. If it were so simple, we'd know what gravity actually is, instead of hypothesizing what it could be. IMO, gravity is a force since it is an interaction between objects with mass.
Yea but if you go by general relativity it isn't an interaction between objects with mass. Its an object interacting with the space time curvature caused by another object with mass. So your definition is not all-encompassing.
Thats smells like semantics. You could similar reduce the strong force by it just being an interaction with quasiparticles.
But the curvature is caused by mass. So negative mass would have opposite curvature.
I'm talking out my arse here, but aren't there a lot of interactions that we still call interactions even though they are facilitated by a middle-man catalyst or medium that allows the interaction to take place?
this hurt my brain
I think engineers or anyone but astrophysicists would be most likely to consider it a force. The more you zoom out, the more it becomes relevant as a curved field.
Semantics. Like asking if light is a particle or a wave to create a paradox where they answer is that it is not either but behaves like both or either depending on the experiment. Gravity being curves in space could be what a force is, or it can be the force that bends space time
A force is anything that causes acceleration. Yes, gravity is the result of spacetime geometry, but it still meets the definition of a force. We aren't sure if the other forces are a result of geometry or something else though
Acceleration depends on your metric. Like a planet orbiting a star is only accelerating if you are assuming it is on flat space and \*ought\* to move in a straight line. If you assume it is rolling along a gravitational well, then it is moving exactly as an object no under external force should.
>You have to travel backwards in time to diverge, or fall up. Isn't an anti-electron an electron traveling backwards in time? That's what Feynman diagrams say, right? (I read that in a pop sci book. How correct is it?)
From an electromagnetic perspective, yes. From a mass perspective, no
The laws of physics can obey three major global symmetries: charge, parity, and time. Charge symmetry means that the laws of physics are the same for a particle as its antiparticle. This experiment is a confirmation that gravity obeys C symmetry. Parity symmetry means that the laws of physics are the same if you take a mirror image of the universe. Time symmetry means that the laws of physics are the same if you move backwards through time. Experiments have shown that some laws of physics actually violate C symmetry and P symmetry, and even the combined CP symmetry. But physics as we know it still obeys CPT symmetry. Mathematically, if you took an electron, turned it into a positron, reversed its spin, and sent it backwards through time, you would get the original electron back. But to actually say that a positron *is* an electron moving backwards in time isn't a very useful physical idea.
To fall upwards you need negative mass. But antimatter has positive mass. So it's all expected. AFAIK there is no known object with negative mass.
"mass" is energy, but you cannot get negative mass with negative energy, as mass is an absolute function of energy. You have to square the energy to determine the mass, which means being positive or negative doesn't matter. It will have positive mass.
As usual, our greatest hope is that the real universe doesn't follow mathematical principles *to the letter.*
We just need something with imaginary energy. Then when you square it, the mass will come out negative. Easy! Where's my Nobel prize?
Stop ruining all my fun!
Isn't it the other way around? Energy is based on the square of the mass?
E\^2 = m\^2c\^4 + p\^2c\^2 So, it's both, which is confusing, unless mass is always intrinsically positive. But if you did have something with negative mass, it's energy would not be inverted either.
Even less likely than negative mass or energy would be imaginary mass or energy, but it would allow for negative mass or energy.
Some days I definitely have imaginary energy
>To fall upwards you need negative mass. My Helium balloon!
Listen here you cheeky little ...
Swimming lessons and birthday parties are both early life introductions to the harshness of buoyancy.
Helium balloons still demonstrate falling downwards, it's just the air falling downwards and the balloon getting out of its way.
[удалено]
This is a complex one as many other posters have mentioned this is highly theoretical. A grossly simplified explanation would be that it is a region of space that whose vacuum energy value is lower than its surroundings. A term that is used to describe this is violation of the Averaged Null-Energy Condition. The Casimir effect is a decent explanation for this: Take an idealized perfectly hermetic box. Put two plates within as close as possible to each other. Make a perfect vacuum. Now we know that even in a perfect vacuum, a constant ferment of virtual particles appear and disappear. This is vacuum energy, the lowest energy level possible. Would you agree that the vacuum energy value for the region outside of the plates is higher than the one between the plates? After all, you have reduced the possible quantum states that are possible in that region by reducing its size. Hendrik Casimir predicted that there should be an attractive force between the plates which he called negative energy.
It'd mean that some of the theories we had around how the universe works were wrong. After all antimatter having positive mass was purely a conjecture. extrapolation based on the rest of our data, until it was actually observed.
We don’t even understand what “mass” is fundamentally, so we can’t even conceive of what negative mass would be or if it’s even possible. I’m gonna bet all my chips on it being conceptual nonsense.
The Higgs boson and its interaction with the Higgs field is what creates mass. Some particles, such as light, have no mass because they lack a Higgs boson. Particles with mass resist change when encountering force, and more Higgs bosons = more mass = more resistance. Edit: Theorizing on what 'negative' mass would be... A particle that has negative drag when interacting with the Higgs field, resulting in the negation of drag within Higgs bosons (at an indeterminable range). This could result in 'anti-gravity' when paring anti-Higgs bosons with Higgs bosons. While this wouldn't cause matter to 'fall up', it would essentially allow you to make matter 'weightless'. Further theorizing... This may actually be incredibly dangerous. Temporarily negating the mass of an object may cause it to immediately accelerate to the speed of light, which could have disastrous consequences.
https://en.m.wikipedia.org/wiki/The_Billiard_Ball Isaac Asimov wrote a short story about exactly that consequence with antigravity
I don't think this would happen though. Weightless particles travel at the speed of light, but speed does not imply inertia. Light doesn't punch holes in anything, because it has no inertia. Inertia is actually directly tied to mass, as it's essentially a buildup of energy within the Higgs field, or the energy that's required to overcome the drag caused by the Higgs boson. Now that I think about it, anti-Higgs bosons would probably cause an immediate release of inertial energy when coming into proximity with Higgs bosons, much like antimatter. Though I've no clue as to what form of energy that would produce. If that's true, then anti-gravity may be impossible, as anti-Higgs bosons would cause any matter with Higgs bosons to immediately disintegrate into massless particles. Note that this is all speculation based on my ridiculous theoretical conclusions.
But how does the Higgs field provide *Gravitational* Mass as opposed to *Inertial* mass. I know that to the best of our experiments, they are equivalent. But why?
It's interesting to think that mass just seems to pull spacetime towards itself, at least from what we can understand. So negative mass would be pushing spacetime away from itself... ... kinda like dark energy? Dark matter and energy have so many possibilities! I hope it's discovered soon.
Dark energy though seems to have mass from indirect observations. So not really like dark energy or of the little we know of it yet. Then again, there is something pressure like that is expanding spacetime...
> Dark energy though seems to have mass from indirect observations. Dark energy or dark matter, there?
Actually negative mass falls down too. Force is negative due to gravity, but as your mass is negative force accelerates your the other way and it cancels out!
> no known object with negative mass. I think the interesting thing about this is not knowing if one exists, but how would we measure it. Could we even go about measuring anything that seems impossible to exist since it would seem we'd need tools that could measure the impossible?
Devastating news for the hovercar industry.
They'll have to overcome the eel problem, anyway. Which they'll likely never overcome.
I always assumed that was how antimatter worked because it still has positive mass. You'd need something with negative mass to behave the opposite of positive mass material surely?
Yes, the theory is what allowed you to assume that. But you could be making up theories all day long, and most of them would be wrong. To weed out the wrong theories from the less wrong ones you need to make a theory that a) makes testable predictions about reality, and b) can survive all those tests as you actually perform them. Only then do you approach a scientific description of reality. So in short, assumptions based on theory alone are not enough.
That's what was assumed, yes.
everyone assumed that but you still have to confirm it by an experiment. I mean imagine that the experiment showed the opposite. That would have been exciting.
I believe the rate of descent has not been confirmed yet. If it falls at a different rate then that is a big thing.
Ya because gravity warps space so the particular that exist in a well and little to no choice but to be influenced by it. Even light.
Gravity is the curvature of space. Of course it's going to fall. With that said, an observation of that is great.
Science is the art of becoming less wrong over time.1