It's never wrong to confirm by experiment, but there was never really any doubt among professional physicists that antimatter falls down. Similar doubts are expressed about the feasibility of the warp drive by Alcubierre himself: https://twitter.com/malcubierre/status/362011821277839360
Even among people who hold out hope that a warp drive is physically possible (as opposed to merely mathematically possible), I don't think anyone ever suggested that antimatter was a candidate for the negative mass required by the equations. It's always been some kind of unobtainium.
I can give an example. If something moves back in time, it interacts as if it has negative mass relative to us, who move forward in time. Of course nothing moves back in time but tachyons which exist only on paper. The worlds of things moving forward in time and backward in time never meet because they are just two different solutions to the same equation and we have absolutely no evidence that the second world exists. Inverted matter from Tenet should have received negative mass but we most likely will never see it because time may be an illusion likewise to rotation.
Well, i think some trouble lies in that things with 0 mass are already defined here. Light has 0 mass, and anything with 0 mass must move at the speed of light since it has no inertia to stop it. What other point of reference can we use when 0 has been so solidly defined?
No, the gravitational analogue of voltage is the gravitational potential energy. We can freely shift them by constants because absolute potentials are unobservable: only potential differences have physical consequences. Mass, like charge, is directly observable.
As I understand it, dilithium crystals control the matter/antimatter reaction somehow. Zephram Cochrane's first flight used a ship powered by a nuclear reactor, I think.
The warp field is made with an array of "warp coils" which apparently require the large amount of energy from the matter/antimatter reaction to create a subspace distortion field that allows warp travel. What is subspace? It's never adequately explained, but sometimes monsters come out of it and kidnap you to a pocket dimension where they rearrange your organs.
Antimatter is only used because, when combined with matter, it has a higher energy density than anything else known, including fusion. That part is completely within known physics. The "dilithium" is used somehow to control the matter-antimatter reaction; they have nothing to do with the warp field. Why the writers came up with this I don't know, but it does make for a convenient plot device sometimes when they have some problem with dilithium mines on some distant planet. Like various hard-to-acquire materials today, there are political problems caused by the scarcity of dilithium, and this comes up in many episodes. And, conveniently, dilithium somehow can't be replicated by the regular matter replicators.
The warp field is created by the warp nacelles. How? Who knows.
Dilithium is a mediator for a deuterium/antimatter reaction that generates the fantastic amounts of power required. The warp field is generated by some sort of coils in the nacelles.
It always seemed like a reasonable, but still big, assumption that antimatter behaved the same way under gravity. Anti-particles have opposite charge, so maybe it could have made sense that they have opposite "gravitational charge"? But also gravity doesn't have "charge".
So yeah, agreed. A good thing to confirm, even if (especially if) they expected the result to be unexciting.
Not a big assumption at all. Gravity is believed to be a property of space as opposed to a property of matter. That is, a satellite orbiting around the Earth is really going in a straight line but space is curved.
Seen that way it’s just insane that any kind of matter could fall up. See
> a satellite orbiting around the Earth is really going in a straight line but space is curved.
This is not quite how it works, I think. The gravity of the Earth isn't high enough to cause space to curve around in a circle, and the path of the satellite depends on its orbital velocity. If it fired a rocket forwards to reduce speed, it would fall towards the Earth, but that's not due to a change in space curvature.
The paths taken by light will follow the curvature, however. That would give a very small deflection for light passing near the Earth.
The gravity of Terra is exactly enough to cause the curved orbit. You are just missing how shallowly curved it really is, by squashing out the time part of spacetime. In 4 dimensional spacetime, the circle is (to simplify a little) really a helix, because it does not return to its starting point, and it's very stretched out along the time axis. (Or very narrow along the space axes, depending from how one choses one's units.) The curvature only looks greater because you are discounting how much greater length of time it extends across in order to do all of that curving that gets it all of the way around Terra.
The curvature is quite small but is responsible for orbital motion in the steady state condition. I don't think the parent comment was suggesting that space would "curve into a circle" unless you are implying something else specifically.
All ideal orbits, with no other forces involved, are equivalent to geodesics. However that only applies in true free fall. Actual orbits decay due to tiny non-ideal characteristics which have a cumulative effect or stochastic "butterfly effect"-like characteristic over long periods of time. For example in the ideal case, as soon as a satellite fires maneuvering thrusters, it is not following a geodesic for the time that the rockets are active. After the maneuver is completed, a new steady state condition can be calculated piecewise and then it's following a geodesic again. Another example is the ideal state of a satellite being in a low orbit that decays due to friction with the atmosphere, for which there are good estimates but not exact predictions. Due to the friction, there is a tiny acceleration (which happens to become larger over time) and this makes it follow something that starts close to a geodesic but deviates from it.
The quantity coupled to the curvature is the stress-energy tensor. In local coordinates, this can be represented as a (1+n)x(1+n) matrix where n is the number of spatial dimensions, with components given by
[mass density, mass flux = momentum density]
[energy flux, stress]
Photons are massless, but still carry momentum and energy, so they do gravitate.
A negative mass particle would repel a positive mass particle but be attracted by a positive mass particle so the two would accelerate to ever increasing speeds but the positive and negative kinetic energy would cancel out so energy would still be conserved.
If photons had mass they would attract each other as well.
Gravitational lensing is pretty strong proof that photons follow the curvature of space affected by a gravitional field. If photons had mass themselves they would not follow straight lines in free space but they'd clump together over astronomical distances and long periods of travel. Though there is a way to get them to act in unison which gives some pretty odd effects:
Photons do interact with each other gravitationally. It's not as simple as just attracting each other - the Newtonian limit doesn't work here - but parallel photon beams going in opposite directions, for instance, will be deflected towards each other.
But photons traveling in (almost...) the same direction (such as the photons that arrive at some destination after gravitational lensing do not gravitationally attract.
I thought photons also contributed to the curvature of spacetime because they have momentum (and thus energy). I would expect it to be a pretty miniscule contribution, though.
Hm... just an interested layperson here but would that not require some kind of mechanism by which the photon sheds some of that momentum? Which would seem to be pretty hard if it really is an 'elementary' particle. Unless 'photon === graviton' and you find photons shedding other photons!
I'm a layman as well, but I think photons can effectively lose energy in various ways, one of them being the well-known redshift effect. And one of the main causes of redshifting is photons climbing out of a gravitational well (this is called a gravitational redshift).
However, whether that translates to a loss in momentum is a bit more fuzzy and I really can't tell whether it does or doesn't. Although I'm far from being a physicist, so hopefully someone more knowledgeable chimes in to enlighten us...
But I'm curious: what is your reasoning for asking whether photons have a mechanism to lose momentum as a consequence of them affecting the curvature of spacetime? It's not at all obvious to me the relationship between these two concepts.
> However, whether that translates to a loss in momentum is a bit more fuzzy and I really can't tell whether it does or doesn't.
Yes, redshifted photons lose momentum. Momentum (really the stress-energy tensor) is conserved locally, and along trajectories that preserve the metric, but global momentum conservation in GR isn't even well-defined.
If they don't lose momentum then there is no interaction (in order for any kind of interaction you need to lose some energy). Momentum is pretty much all a photon has and it could conceivably toss off much lower energy photons to shed that momentum.
If you treat GR as a gauge theory, and plug local Poincare symmetry into Noether's theorem, the corresponding conserved current and charge you get out are the stress-energy tensor and 4-momentum. It's not exactly the same situation as typical examples of gauge theories, since you need to impose some extra geometric conditions to pick out the Einstein field equations, but I think it's close enough that 4-momentum could reasonably be called gravitational charge.
It does not. Time-reversal is antiunitary, so you when you apply it to p_0 = i d/dt, you pick up one -1 from i and another from d/dt, and they cancel out.
If antimater particles were time reversed then I could see how they could have negative energy and thus antigravity. That's not at all how any observed particles behave though.
I don't think anybody expects a wrap driver to be possible. It's just one of those odd things where the math says something, and it's well work looking at just in case. (Just like negative mass matter is something that nobody expects to exist, but likes to appear on equations here and there.)
That said, I don't follow it closely, but didn't somebody recently worked out one that works without negative mass matter?
>That said, I don't follow it closely, but didn't somebody recently worked out one that works without negative mass matter?
Yes. There was recently a few papers published showing that a static warp field is mathematically possible without negative energy. However, the field doesn't move or impart acceleration on its own. The best you can do is drag the warp field behind your ship with normal thrusters. Such a field seems to be pretty useless right now, but maybe that research will lead to something else in a few years
Perhaps not useless, but definitely not as convenient as we hope warp technology will be someday. Could such a device be used as a way to improve thruster efficiency? If you can drag a large enough warp bubble with conventional thrusters, and it "slopes" space in front of you, could it make moving in the direction of the slope easier so you use less fuel?
I don't remember the details, but they explored some different field geometries which were more useful, but required an impossible amount of energy. Like, more energy than the entire universe.
The static warp field doesn't allow you to go faster than light because it doesn't move relative to the generator. You can drag the field around at sublight speeds but that's about it.
Though IIRC they played around with some different geometries that did move, but the energy required was many times more than the entire universe contains.
Without reading any of the mathematics, I propose the warplev equivalent of maglev trains. We build a long train of these devices that we then turn on and off at the right times in order to propel something. It's genius and I will be making a wikipedia page, .io domain, and putting up an Angelist RUV.
There are generally speaking, two interpretations in scifi. I don't really understand the physics, so apologies if I get it wrong.
1. Better known as the "Alcubierre Drive", Compress space infront of you and expand the space behind. Essentially inching forward like the inch worm. (If we presume that visually, the inch worm stays in the hunched position and slides forward because our eyes cannot see it's movement)
Doing this smoothly in theory lets you accelerate and decelerate infinitely.
2. Warp space infront of you to create gravity, and pull you forward. Essentially, you make a pot hole in space time, and "fall" into it. This is basically the same Alcubierre Drive, but without the expansion at the rear.
2.1: One version holds that pothole at a specified distance infront of the ship.
2.2: The other version creates the pothole, then removes it before you reach it.
I've often wondered about option 2, but wouldn't that be very risky if you were near something/someone and you created a large gravitational field?
Also, if this was common and you had lots of ships warping the gravity field then would that not be some kind of space pollution?
I know space is big and all that, but this seems like an irresponsible option.
Yes actually, it would be. It would also depend on whether you have fine control over the size of the spacetime pothole. It is also possible that the larger nearby gravity well would pull on the pothole.
I like to think that concepts such as "you must be at the edge of the solar system to initiate faster than light travel" or "cannot initiate faster than light within the gravity well of planet" originate here.
I have nothing to backup that theory of course.
As for space pollution, I never really thought of that. But considering some of our observation tools observe 'gravitational waves'? I could imagine another "starlink and light pollution is getting in the way of space observation" situation.
It's pretty much what it says on the tin. A field which warps nearby space into a different shape.
What that means is complicated to explain, but the gist of a warp drive is that you expand space behind you and compress space in front of you. The normal space in between gets pushed forward, ideally at speeds faster than light. There's lots of good explainers on YouTube if you want to learn more.
I always liked the neat dodge of hyperspace proposed by Larry Niven. Idea was that humans never noticed it in their experiments, because they always ran their tests on Earth, too close to a gravity well, where it resolved to a singularity. At this point I believe the hands on the other foot. It's not the speed of light - but causality itself - that's not allowed to be broken by the universe.
The author directly addresses this sentiment in the concluding paragraph:
> Although there are physicists who wonder “Why did we even need to do this experiment; we all knew that antimatter has positive mass,” that sentiment is absolutely foolish. We must remember — and I say this as a theoretical physicist myself — that physics is 100% an experimental science. We can be confident in our theory’s predictions only insofar as we can test and measure what it predicts; as soon as we step outside of the realm of what’s been validated by experiment, we run the risk of stepping outside the realm of where our theory is valid. We just learned that Einstein’s general relativity passed another test, the antimatter test, and with it, our greatest science-fiction hope for achieving warp drive has completely evaporated.
"Why do we need to measure the speed of light coming from a moving source. We all know that the velocity of all objects compounds with the velocity of their emitter"
Agreed, though also I really appreciate this sort of "obvious" experiment, because the incentives really aren't set up to encourage it and we've been surprised often enough over the centuries that Actually Double Checking is probably something we should do more of.
(there's a parallel here to 'more negative results' and 'more replications')
>Also dying with this measurement is another sci-fi hope: artificial gravity that works without rotation or acceleration. If antimatter truly anti-gravitated, then simply by building a spacecraft’s floor out of normal matter and its ceiling out of antimatter, we could create a spacecraft that had its own built-in, automatic system for artificial gravity.
I've never heard this idea, but that sounds hilariously dangerous.
Doesn't that proposal merely ~halve the amount of mass required?
I'm in an office right now that has a ceiling made out of normal matter (gypsum, fiberglass, steel, and tar, probably a couple thousand kg overhead) and a floor also made out of normal matter (carpet, concrete, iron, silicon, oxygen, and a bunch of other stuff adding up to 6x10^24 kg), which generates artificial gravity at 1g. It happens to be rotating at 1/1440 RPM, but that's only a 0.2% reduction in the acceleration.
Sure, if antimatter caused anti-gravitational forces, you could have achieved the same gravitational acceleration I experience in my office using one 3x10^24 kg sphere of antimatter overhead and one 3x10^24 kg sphere of matter beneath, but that's still not a Starship Enterprise, much less an X-wing, with artificial gravity generators. You're still stuck at:
F = G x m_matter / r^2 + G x m_antimatter / r^2
F = 4 x pi / 3 x G x density x radius_matter + 4 x pi / 3 x G x density x radius_antimatter
with planet-sized masses and radii for both.
And I'm not sure that "hilariously" is a sufficient modifier for the danger level when standing in a 3m gap between planet-sized spheres of matter and antimatter.
How big as mass? After some calculations on a slide rule:
> “I’m almost afraid to answer. You would need a good sized asteroid, of lead, to get anywhere at all.”
> “Asteroids have been moved before this.“
> “Yes, but what is to hold it up? No, Chief, there is no conceivable source of power, or means of applying it, that would enable you to hang a big planetoid over a particular spot on the Earth’s surface and keep it there.”
But wait, what about something dense, like core material from a dwarf star?
> “All we would need for that would be a ship capable of going light-years in a few days, some way to mine the interior of a star, and a new space-time theory.”
> “Oh, well, skip it."
Oh, yeah. In this space-age future where people can travel across the Solar System, they also use punched cards.
And hilariously useless even if you wave away the costs and catastrophic dangers. Yes, you can have a floor of normal matter and a ceiling of antimatter and produce... like... maybe 0.00001 m/s^2 of gravity?
Ludicrous barely begins to describe the idea. It would have to be a mass on the order of magnitude of a moon that you would have to a) create and b) carry with you so that you would feel some gravity. Why not just build a rotating ring instead? No one in scifi was even entertaining this idea afaik.
> No one in scifi was even entertaining this idea afaik.
Yeah, this is the first I've heard of it too. If it's not rotation it's usually left unexplained, and when it's not it's usually something along the lines of an artificial gravity generator that pulls things towards it, like in Star Trek the floors contain "gravity plating" that does that on a small scale.
Note: armchair reply, I don't know enough astro whatnots to substantiate this take:
That implies that you can actually move the black hole; a black hole producing 1G requires it to be as heavy (or, to have as much attraction) as the earth itself. It would be a lot more compact - a black hole as heavy as the earth is about the size of a ping pong ball - but if my intuition is correct, would require as much force to move as it would to move the earth.
Yep, F=ma. For a given force, if mass is big then the acceleration must be small.
Also, I feel compelled to mention that to get an Earth–like gravitational field near the event horizon of a non–spinning black hole, it needs to mass more than the whole galaxy. It would be about a light–year across, iirc, and if you built a shell around it (which would not be easy) then the surface area would be so large as to beggar description.
Small black holes are not very earth–like because of the extreme tidal forces. Trying to stand on that ping–pong ball would be extremely uncomfortable.
An "antimatter black hole" is just a black hole. There might still be something behind the event horizon to annihilate with, there might not, the question might be meaningless, but in any case you're not getting anything back out again.
What happens when an antimatter black hole collides with an equal mass matter black hole? Does the total mass convert to energy? If so what happens to the gravitational effects?
No, an antimatter black hole is literally just a black hole. They're the same thing.
> Does the total mass convert to energy? If so what happens to the gravitational effects?
Energy density and mass density are the same thing too. A kilogram of hydrogen next to a kilogram of antihydrogen gravitates in exactly the same way as ~10^17 joules of equivalently distributed photons. The only difference is that the photons won't stay equivalently distributed for long.
I asked my particle physicist buddy about this and he pointed me here[1]. It sounds like you're giving the "classical" answer, but it's an area of open discussion. He thinks it could conceivably emit energy as gravitational waves.
The no-hair theorem very likely goes through semiclassically as well, at least where global symmetries like baryon number are concerned, but yes, ultimately no one knows for sure what the story is for the undiscovered true theory of quantum gravity.
You'll push the black hole with precisely the same momentum (in the opposite direction) as you yourself got from whatever device was pushing the matter towards the black hole.
I know there are a lot of hopes for warp travel, but doesn't it make more sense to decouple (most of) space travel from moving matter?
To do this you need to decouple consciousness from bodies, which isn't possible with humans given that our consciousness grows along with our brains and everyone's structures are unique. But it is possible with artificial intelligence. Once consciousness has been digitized, you can beam it at the speed of light to a receiver.
You still need to physically install the receiver somewhere, which is why I said only most of space travel could be non-physical. But once that receiver is in place, you can beam information to it and construct bodies onsite at minimal cost.
This just seems like the kind of space travel the universe prefers, since it minimizes action. Energy is for travel, and matter is for staying put.
The stupendous amounts of energy required for warp travel just seem wasteful, when instead of adapting the universe to life we could adapt life to the universe.
> But it is possible with artificial intelligence. Once consciousness has been digitized, you can beam it at the speed of light to a receiver.
That may not remain true. The ability to serialize consciousness does not come for free, it requires extra wiring to carry all information out of the system or to stream it in, which is an intrinsic inefficiency. All other things kept equal, a brain's performance ceiling is higher if you only locally connect the units/neurons that need to be connected and nothing else, but in doing so you give up digitizability. It is entirely possible that future AI, in order to be performant enough, will lose the ability to be transmitted in the way that you describe.
A lot of people seem weirdly aggrieved by the limit of the speed of light. It's not really the reason we can't go to space -- if you had magic energy density you could go to the stars in as little time as you wish, due to relativity. (Weird stuff happens when you try to come back, but nobody ever seems to care about that anyway.)
I think people hear "Einstein said you can't go faster than the speed of light" and think, "Surely I can figure out how to be smarter than Einstein". It appears to be parallel to the ones who get cranky when being told that Newton says you can't make a perpetual motion machine.
I suspect that they don't spend as much time thinking about the brain-in-a-box version is that it opens up too many scenarios that are hard to think about. If you decouple consciousness from bodies, who are you? Why not make multiple copies? Why go anywhere at all, when you could just stick the sensors there?
People really want the cowboys in space, and get aggrieved that somebody told them they can't. So they focus on overcoming a limit that seems like it can be solved just by thinking really hard, and leave the engineering details to the peons with calculators.
Agreed. Thing is we can still have our cowboys in space. The solar system is insanely huge and can be traversed in human time scales with technology based on known physics. The baseline world of The Expanse (minus the alien stuff) is entirely feasible.
Interstellar travel is entirely possible too as long as you are okay with it being effectively a one way trip. Suspended animation is probably possible; we can do it to some animals and individual organs. So you go to sleep for a very long time and wake up in another star system. It would make the most sense to send a bunch of robots to build yourself a settlement first. Or alternatively send sentient AI which would find it much easier than humans to simply turn itself off for the duration of the trip.
We need to let go of the "Ship full of brave men" meme of space exploration.
It'll have to be robots, probably very small robots, some kind of solar sail / exogenous energy source (or maaaaaybe fusion?), and probably either a copy of some human's consciousness in a machine, or a bunch of fertilized frozen embryos, or both.
And even then only after a lot of gene / tree bombing of the target planet to have any hope of making it liveable.
A very believable theory is that this is how life on earth started - another ancient civilization shooting the building blocks of life everywhere and hoping something sticks. (panspermia?)
But while this is cute, given the inexorable passage of time and entropy, any evidence that life was planted by ancient aliens has long gone. If it was e.g. a spaceship or meteor, it's been swallowed up by the earth and into the mantle by now.
Unless there's a new source - like aliens making contact - it will remain unknowable.
Yeah - I don't think it's so clever that nobody has thought of it. It just seems obvious when you look enough into how hard inter-stellar travel will be.
But making machines that operate for 100 years seems doable if we try.
how are you so sure that anyone else besides you is actually conscious ? you might be the only conscious being in the universe. the whole universe is yours. you've already traveled the entire thing.
I'm conscious too but that's in my own universe, running in parallel to yours.
the "once consciousness has been digitized" step would have many hurdles of similar complexity to meet before simplistic 21st century manipulation techniques would ever apply.
> how are you so sure that anyone else besides you is actually conscious ? you might be the only conscious being in the universe. the whole universe is yours. you've already traveled the entire thing.
Because other's express things that I in my wildest dreams couldn't have imagined.
I think solipsism dies when epistemic humility comes into the picture.
i never really get the notion people sometimes have that consciousness arises from a specific, physically identifiable structure in the brain, where a person actually seems to have a "self", looking out of their eyes from inside their heads, and furthermore is "atomic" in that sense; it can't be split in half (because which half would the "self" be present in then?), yet there can exist no structure that produces the same output without the "they are looking out of their eyes from inside their heads" part.
"self looking outside of my head" strikes me as so completely paradoxical that explanations such as each consciousness is its own universe seem just as plausible as any other. it does not mean the person you are talking to is not conscious, just that their consciousness is playing out in a parallel copied universe.
In the past, this was understood to be the soul and you are correct when you describe it as atomic, though depending on which tradition is describing the soul it can have further attributes. My username is based on such a tradition -- the Nous (pronounced like noose) is considered the eye of the soul. Extrapolating that further, we focus the eye of our soul on whatever we want to, which can be ourselves, worldly aspirations, or spiritual aspirations.
This would be considered the free will we are given at the basest level - we get to choose what we focus our soul on, and that can be changed at any moment. Such a tradition would say that since we are a body/soul composite, whatever we focus our soul on, our body willingly and immediately focuses on as well, for good or ill.
If I was never exposed to the idea that the brain is where all our thinking occurs and believed instead that the brain was an organ for cooling the blood and the real center of my “soul” was my liver or something: Would I still feel like my “self” is in my head looking out my eyes?
I actually really enjoyed some of Sam Harris' "Waking Up" meditation series for this. Not a usual activity for me. However, I greatly enjoyed reflecting on the notion of "there is no self."
Yes the "self" is an illusion, but at least for me, there's an emergent illusion/whatever of "hey im inside this head looking out", which we claim arises from a physical brain structure. if this structure were divided in some way, does my current "self" vanish and two new consciousnesses arise? do those new consciousnesses have memory, so one is on one side of the room, the other is on the other ? at what point is my current "self" no longer viable such that it vanishes?
edit: looks like HN is throttling me again. hmm but not edits. well that's fun
I see your thought on emergence of self. Almost like self is equivalent to consciousness. Without a notion of self, you are part of a larger system with will.
Stemming the claim that there is no free will, I know the argument, but don't agree to it as what we observe (that people make choices at least some of the time) goes against claimed theory (that our choices are random chemistry-driven outcomes based on state of the world). I'm not terribly deep in the area, though, and welcome correction or thoughts.
Speed of light limit is a big problem though. How do you explore the universe if you can't catch up with it? Even with a googol of human lifeforms running as AI spread out across it in a mesh, it is still expanding too fast!
> Once consciousness has been digitized, you can beam it at the speed of light to a receiver.
You may be interested in Philip K Dick's experiences. He believed himself (and humanity) to be receivers for information being transmitted across space.
If we're going to imagine breaking the laws of physics and changing our understanding of metaphysics, as a goal.. then moving an object past the speed of light seems to be more likely than identifying what consciousness is, successfully separating it from it's source and then inserting it in a recepticle, across the other side of the universe.
Stupendous amounts of energy would be beneficial to have for literally everything humans do... whether or not we use the tech on space travel.
We have lived (as a species) through cavemen, industrial revolution to the atomic bomb and somehow you're coming to the conclusion that technology progress has to take a weird bend into uploading people to the internet, as if computers havent capped out on that already?
We have never really cared what the universe prefers. We'd still be living 'in harmony with nature' (so to speak) if we genuinely cared what the universe prefers.
I'd rather be the guy who tore up Einstein's map, than some internet electron.
I'm not sure how we can verify that empirically. Current LLM AI will hallucinate about the feelings it "has" and argue why it is a person, but only because it was trained on human language. The more human we make something seem, the more we blur the line until we might have a day where people upload their consciousness permanently without knowing if "they" will wake up inside the computer or just some copy of themselves that answers all the "don't kill me, I'm a real person" questions will wake up in the computer.
Human software is still intrinsically tied to human hardware, so this seems like it would be far easier to create zombies than true humans, even if the checksum matches after an interstellar transmission.
From a "future harm" perspective, if I have a full, functional backup of me somewhere, who's to say someone doesn't hack it down the line and torture copies of me? What's stopping an AI from torturing my backup because I didn't help fund AI research?
Me never getting uploaded in the first place - that's what's stopping it :)
Well can you prove you're conscious? I'm just gonna assume you're not otherwise. That's the kind of benefit of the doubt we'll be giving AI apparently.
Why would you put an AI on another planet? It's easier to transfer images and other data back here for everyone and everything to perceive.
> construct bodies onsite at minimal cost
That requires a bit more than a receiver. You'd have to build a robot factory, which requires energy production which requires mining which requires heavy machinery, which etc.
Driving on Mars is incredibly slow in part because the signal has to get to and from us for every decision. And if communication is blocked for any reasons, the vehicle is stuck.
> the signal has to get to and from us for every decision. And if communication is blocked for any reasons, the vehicle is stuck
Curiosity and Perseverance have a limited form of autonomy to work around that, as both can AutoNav: the former alternating standstill thinking and movement, the latter "thinking while driving".
That by itself isn't all that clever, since any half versed roboticist can do the same with some trial and error.
What's seriously impressive about it is that it works in real time on an absolute brick of a 233 MHz PowerPC from the 90s. Like, an ESP32 probably outperforms it.
Apparently the Perseverance Mars Rover has some self-driving capability:
With the help of special 3D glasses, rover drivers on Earth plan routes with specific stops, but increasingly allow the rover to "take the wheel" and choose how it gets to those stops. Perseverance's auto-navigation system, known as AutoNav, makes 3D maps of the terrain ahead, identifies hazards, and plans a route around any obstacles without additional direction from controllers back on Earth. [1]
The mission has used AI not just for driving the rover, but also landing and targeting instruments. [2]
>Perseverance's auto-navigation system, known as AutoNav, makes 3D maps of the terrain ahead, identifies hazards, and plans a route around any obstacles without additional direction from controllers back on Earth.
...in spite of this autonomy, Perseverence has a few major problems. It is famous for the severity of it's road rage and intolerance for human drivers, bicyclists, parked emergency vehicles, and pedestrians. Tests show a disturbing tendency toward "eliminating the human element" from it's driving environment to simplify route planning. The lengths the system will go to to achieve this were a major frustrator in early development, and initially attracting the interest of [REDACTION] for [REDACTION] due to [REDACTION] with an effective [THE REDACTION MACHINE IS BROKEN, FURTHER INQUIRIES SHOULD BE ROUTED THROUGH TOM].
Mission planners at NASA found the risk involved with deployment to the Red Planet agreeable, but note that any ongoing colonization efforts will involve having to put the system down for the safety of any eventual colonists.
That's a slightly extreme route planning optimisation, but reminded me of UPS removing left turns (in Right Hand Side driving countries like US) from their route planning to save fuel, lives, C02 emissions [1]
Once established, perhaps, but microchips aren't easy to build. You'd have to send a lot of infrastructure before you could create AI brains on another planet.
This is a good argument for transhumanism. People seem to have a problem with the speed of light since without FTL, unmodified humans cannot meaningfully travel interstellar distances - and pop culture entertainment has surreptitiously sold us on this, if only because otherwise the timeframes and types of bodies involved would not be "relatable" anymore for the common types of drama we consume.
> Once consciousness has been digitized, you can beam it at the speed of light to a receiver.
In principle yes, however, the energy required is still dramatic and bandwidth would probably still be a problem. It seems to me the default option would be to physically send non-aging transhumans, or virtualized/uploaded brains, or people in stasis (or a combination of these) using non-relativistic speeds.
I was a Traveller once, then I suffered a qbit flip in transmission the checksums couldn't compensate for. Now, I just love Coca-Cola brand Mango Fantastic soda, and hunting indigents for sport!
The whole article feels like a strawman, I wasn't aware anyone was presuming antimatter could lead to the negative energy required for the warp drive metrics...
Antimatter is not negative mass or energy. The experiment verifying it falls down wasn't surprising
At this rate it is going to be easier to simply emulate the entire universe (aka Devs) and just travel virtually around space-time that way. Then we can just stay home and eat cheese puffs.
Even mathematically it doesn’t make any sense: we would need to go to a causally disconnected region of spacetime to be able to go faster than the speed of light, but that’s just not feasible. Once you go to that causally disconnected region of spacetime, the only outcome is to go to a singular point in space (even though you can go back and forth in time, theoretically at least) : if that sounds familiar to you, it’s because it is well represented into the movie «interstellar» and indeed he goes to a region causally disconnected to ours: a black hole.
Or that the only thing standing between humanity and the ability to build space craft capable of colonizing other planets is getting the right numbers to plug into a ‘gravity equation’?
Having been sold on the movie by people telling me the science was “realistic”… the reality was disappointing.
> getting the right numbers to plug into a ‘gravity equation’
Those are what I like to call "load-bearing" numbers. :)
There's so much science daydreaming in what passes for the science press that people think all of our problems will be solved once the smart people (or quantum computers) find the magic formula and those elusive load-bearing numbers.
Half the people here understand physics, and the sheer impossibility of the task due to the relative magnitudes involved, and have resigned themselves to "we better learn to live on this ball together as it's all we're ever going to have". The other half daydream about magical solutions that marvel movies tell us exist, we're just waiting for an Elon Musk or Tony Stark to discover it and then humanity enters a golden age.
It's been really weird seeing all these warp drive and antigravity people crawling out of the woodwork in response to this result.
I have never heard of antimatter proposed for anything other than an energy source/storage. Not even in the oldest SciFi stories. Where did this idea even come from? It seems to have just appeared from nowhere as a way to feel bad about an otherwise inconsequential result.
Not weird, just irrational. If warp drives were possible, aliens might be traveling to us before we'd invent them. That doesn't seem to be the case. There are a lot of explanations for that, including a few that involve conspiracy theories where this did in fact happen but we are being kept in the dark about it. But the easiest one would be that it hasn't happened because it isn't possible. Faster than light travel not being possible, it's unlikely for there to be a coincidence of any other intelligent species to exist within tens/hundreds of light years of our tiny little corner of the universe exactly at the moment where we hit enlightenment, steam machines, and rocketry in the time frame of about 250 years. Never say never of course but it does sound astronomically unlikely when you put it like that.
In the absence of any nearby aliens to travel to, what exactly is the value of traveling at warp speed to some desolate bit of universe? We'd get nowhere a lot faster is about the most positive thing you could say about that. Most sci-fi is premised on the notion that we're not alone and that there is this wealth of interactions (good and epically bad) to be had on the far side of any worm hole that we travel through at warp speed. But we have zero proof of that nor a way to travel in such a fashion. Or even the confirmation of the possibility of being able to do so. Fantasy and reality are not really aligned here.
Theoretical warp physics -- the real kind, like Alcubierre, not the Wesley Crusher kind -- proposes that a source of negative mass would be critical to the creation of a warp field.
Antimatter as part of an energy storage system for propulsion is still a good idea. They'll just have to look elsewhere for that property, or modify the theory to work on different principles. Eric Lentz is working in that direction and doesn't think negative mass/energy is needed.
>Theoretical warp physics -- the real kind, like Alcubierre, not the Wesley Crusher kind -- proposes that a source of negative mass would be critical to the creation of a warp field.
Well, yes, that's always been the crucial missing component from Alcubierre's design, but I've never seen anyone suggest antimatter would have negative mass or energy before now. The talk has always been about some hypothetical exotic matter
I don't understand this result. How would this experiment be able to detect the "antigravity" of antimatter? If the Earth is curving space time in one direction and then antimatter is curving space time in the opposite direction, would not relative impact of the antimatter be so negligible to be undetectable? We are talking about the ability to "unbend" space time of what a particle or two relative to the mass of the earth? So what if it falls, that just means its barely unbending space time.
To use an analogy, Let's say I am on the Amazon river (fastest river according to google). You want to detect which way I was swimming. Would you even be able to detect the marginal effects of me swimming upstream relative to the massively more impactful force from the river?
I am sure the problem here is me, so if someone can correct my thinking.
You're making a very interesting distinction between the experimental result, which is that antimatter follows the same space-time curve as normal matter, and the dashed hope of warp drives, which is that antimatter causes the same space-time curve as normal matter.
However, if antimatter were to create a negative curvature but follow positive curvature, then you would be able to put a lump of normal matter next to a lump of antimatter, connect the two together, and the whole mechanism would spontaneously accelerate forever, breaking the laws of conservation of energy and momentum. For that reason, I think this experiment also gives us high confidence that antimatter causes exactly the same space-time curvature as normal matter, even though we haven't gathered enough antimatter to see it creating a normal space-time curvature. In essence, gravity is symmetrical.
To my understanding, the researchers released antimatter particles with detector plates above and below them. The particles started out traveling in random directions. Some of the particles hit the top, some hit the bottom. They saw that more particles hit the bottom than the top.
If the particles had "anti-gravity", they'd be repulsed by the large mass of the earth (instead of attracted), and you'd have expected more to hit the top plate than the bottom plate.
The researchers also added a magnet to the top designed to cancel out the downward force from gravity, and they hit the top and bottom plate at even rates.
Positrons react with electrons to produce a distinctive pair of 511 keV photons travelling in opposite directions in the frame of reference of their collision.
There's also a much more complex mess that happens when protons react with antiprotons.
> To use an analogy, Let's say I am on the Amazon river (fastest river according to google). You want to detect which way I was swimming. Would you even be able to detect the marginal effects of me swimming upstream relative to the massively more impactful force from the river?
Definitely yes! If you're even a reasonably competent swimmer you should be able to outswim the Amazon and make headway upstream at most points.
I'm not sure what this says about your analogy, but I would think the measurement devices are millions of times more sensitive than needed to detect which way you were swimming.
I tried with Beastmaster and Swampmonster with First Wife, but I'm not Elon Musk so it didn't fly. I might be able to sell Zefram Cochrane, though. Do you think it'll matter if Cochrane is his middle name? :D
Can you cite this? All I see is that BigThink is owned by FreeThink [0], and FreeThink appears funded by Bedrock Capital and MaC Venture Capital [1], neither of which I can tell are associated with the Charles Koch Foundation [2][3].
That said, I've spent ~5 minutes on this, so I certainly missed something.
Why did they think it would have negative gravitational attraction? I always thought it would be attractive mass and didn't realize that was to be proven.
EDIT: now that I think about it, what are the implications for the "arrow of time" arguments?
> Why did they think it would have negative gravitational attraction?
They didn't. There are very strong theoretical reasons (among them, CPT symmetry) to expect antimatter to gravitate normally. But it's still good to actually check.
We truly live in the universe with most boring set of physical laws.
Hard light speed cap, no anti-gravity, entanglement can’t be an information channel, no warp drives. It’s like we got stuck on the “no fun” setting hahaha.
90-something-percent of the novel was spent following some frustrating character or just otherwise not going anywhere, just for all the interesting things to happen in basically the epilogue, and for every novel to have some frustrating deus-ex-machina be wheeled out at the last second, because of reasons, I guess? It all felt frustrating and pointless. It was like the fiction equivalent of that person who goes “nah space marines would win because uhm actually they have the xyz”.
Maybe I just have low standards for literature, I didn't realize so many people disliked the books but on r/scifi and here on HN people really dislike the Three Body Problem series.
I liked it but after the first 50 pages of book one I realized "Oh, this is anime". I think that having consumed a lot of anime in my teenage years I have more tolerance for story arcs that overstay their welcome, but make up for it with epic twists/payoff. I think that these expectations make it more palatable.
I mourn that the sectoral conflict has resulted in yet more violence. People can live pluralistically -- it's been proven many times over to work well and in the best interest of all people involved.
That said, it's pretty far removed from a conversation on antimatter.
> If any sort of mechanism could exist for circumventing the limitations of conventional travel through spacetime — limitations set by the speed of light — it must involve leveraging the curvature of spacetime to create such a “short-cut” between two otherwise disconnected points. Perhaps the most famous instance in all of fiction to leverage this was the idea of “warp drive” as developed by the Star Trek franchise.
Did Star Trek actually originate the warp drive idea? I always assumed some scientist somewhere originated it first, then the ST writers picked up on it and used it in their world-building. But kind of mind-blowing if it was the ST writers who originally conceived it.
> By expending a vast amount of energy, the idea was that space could be severely curved, and in some sense, compressed. As the space ship moved through the compressed space, it would take this long-sought-after short-cut, enabling very rapid travel over great distances, without causing the outside Universe to age rapidly relative to the crew.
There are conflicting conceptions of warp drive accelerating time outside the warp bubble (or decelerating it inside the bubble). Star Trek’s warp drives obviously don’t accelerate external time (or slow internal time). But in Cixin Lui’s Three Body Series, curvature propulsion (aka warp drive) does slow internal warp bubble time. Which is correct?
Side note: re-watched ST2 and 3 recently and switched to french audio for a bit for giggles and nostalgia: warp speed got translated to "exponential hyper-atomic".
The controversial scientist Bob Lazar, the guy who made Area 51 a household name, put out a video when he first went public that, regardless of whether you think he's full of shit or not, is pretty interesting and better than most sci-fi in terms of explaining how an advanced vehicle might travel without propulsion and not be limited by the speed of light [0].
His premise is that the strong nuclear force is a purely attractive sub-force of gravity that affects spacetime in the same way, and that there are heavier elements that were created in star systems with much more energy than our sun and its predecessors. These stable, high atomic weight elements (specifically element 115, which was synthesized and added to the periodic table much later) have large nuclei past a certain size threshold, in which the strong (gravitational) force reaches nonlinearly beyond the nucleus and can be amplified and focused (somehow?) into a gravitational wave that distorts spacetime. He claims that antimatter annihilation, also fueled by the same element, is the source of power for that amplification.
Real physics requires ten simultaneous partial differential equations for the gravity, and 17 space filling complex-valued fields for the particles in the standard model, and they don't even work right with each other.
Interesting to me, sure, but I'm enough of a nerd than in the team building exercise today where we all had to write a one-word summary of ourselves on a post-it note in secret, then guess which post-it corresponded to which person, even though we were all nerds and I wrote "nerd" on my post-it, everyone else immediately knew it was mine without any debate.
It's not like you or I are actually going to do anything based on our limited understandings of particle physics, so fortunately it's irrelevant. But I'm not one of those people who says every year that we understand everything (until next year when some updates come out and they reiterate their position).
Contemplating why anything exists at all is much more interesting than inaccessible and incomplete particle physics anyway.
The only thing that real physics is good for is telling enthusiastic people that "ackchyually that's not possible because of these equations I won't bother explaining, trust me bro". Made up stuff wins every time.
My understanding as a non-physicist is that the specific requirement for a warp bubble Alcubierre-style is negative mass. Now this negative mass is theorized to come from some form of exotic matter, which could but doesn’t have to be antimatter. The jury is still out on this one.
As a fan of space travel, it seems the prospect of a warp drive is still not budging much from 0 chance. But that’s okay, we’re also not worse off where we started.
I'm glad they settled this one; however, to my knowledge nobody thought Anti-Matter meant "Anti-gravity" w/rt Alcubierre warp drive. That's not what they meant by 'exotic matter.' But ok. sure. There was doubt that exotic matter could exist at all, and nobody had doubts that anti-matter could exist. I think there is something lost in the translation here. (No I'm not saying that warp drive still must be possible, I just think people, including the article writers, are conflating things.)
Well, yeah, anti-matter is not negative matter, it's more like mirror-matter. Negative energy and negative matter probably doesn't exist in our universe. Negative matter would require an anti-photon that could in theory cause energy to be destroyed if it interacted with a regular photon.
There are four types of matter, of which two are theoretical: positive-matter, positive-anti-matter, negative-matter, negative-anti-matter. Only the first two exist in our universe as far as we know.
The Tsar Bomba (5.3YW) managed about 2% of the power output of the Sun (384YW) - admittedly not for very long though...
So Teller's Sundial design was aimed at 10Gt so ~200 times more than the Tsar Bomba as tested.
So Sundial's peak power output would perhaps have been roughly 1RW?
Edit: Maybe you power the Warp drive with a sequence of Sundials.... in a sort of Orion like approach? :-)
Edit2: So about a billion Sundials a second and you're good to go?
Edit3: Usual upper limit of yield per mass is about 6Mt per t - so a Sundial would be about 1500t. So that would be burning about 1.5 Tt of bombs a second?
> The Tsar Bomba (5.3YW) managed about 2% of the power output of the Sun (384YW)
TIL
You know what's even more amazing/frightening? There is no power limit for hydrogen bombs. You could take a bomb like the Tsar Bomba or Castle Bravo and use that as a blasting cap to trigger an even larger fusion stage. ... and on, and on, in a vast nested turducken of kaboom.
One of the ideas to deflect a planet killer asteroid would, if we had time, be to land there and build a base and assemble such a mega-bomb deep underground.
One of the ideas to deflect a planet killer asteroid would, if we had time, be to land there and build a base and assemble such a mega-bomb deep underground.
Problem: Giant-sized asteroid on collision course with Earth
Solution: Build giant bomb and nuke it
Problem: 843 medium-sized radioactive asteroids on collision course with Earth
From what I read the goal would be to pulverize it into pieces small enough that the majority would burn up or at least be significantly attenuated by the atmosphere, as well as impart enough delta-V to send some fraction of the mass on a new trajectory that would miss Earth.
> John Wheeler once calculated that if one took all the heavy water in all the oceans of the world, one could build a hydrogen bomb that would compress matter at the center so much that a black hole would be created
Possibly the largest artificial one, but pair instability supernova turn several solar masses of hydrogen all the way up into nickel-56 in a few seconds:
Edit: Just remembered that Isaac Arthur has spoken about artificially inducing a Type Ia supernova to synthesise heavy elements, and why sufficiently developed civilisations may want to do this at this scale.
Honestly, this does sound like an intimidatingly high amount of energy, but look at the progress of computational power since, say, 1973, 50 years ago. If the same advances in physical control of energy had taken place, who knows where we'd be today
I'm not sure how many USD/GFLOPS you could get in '73, but in '84 they were Cray X-MP/48 costing $15,000,000 / 0.8 GFLOPS (inflation adjusted $600B/TFLOP); today we get RX 7600 costing $269/21.5 TFLOPS ($12.51/TFLOP).
If energy prices changed that much while spending per year remained constant, your usage would go up by a factor of about 48 billion. This might happen if we develop Von Neumann probes and disassemble a planet to turn it into energy collecting satellites, and some not-even-crazy estimates suggest this is indeed possible over 50 years.
The problem with that comparison is that we are not even close to the theoretical limits for computational density, while we are quite close to the limits for efficiency in things like turbines.
Anything involving a Carnot cycle is a rather primitive usage of energy, so I'm not surprised that turbines are close to their peak efficiency since humans have been using them for at least a century now.
More modern forms of energy usage will skip the whole heat-cycle skip and just directly produce electricity from some other energy source. We're still in early stages of much of that; just look at how much PV (solar) efficiency has improved in the last few decades. And we've barely even looked at what we can do with nuclear power[1].
PV has increased from a <10% percent efficiency in the 80s to 25-30% now for commercially available panels. They can grow another 3.3x in efficiency at most, hardly comparable to the doubling every few years that semiconductors have had.
The wikipedia link you provided contains the following snippet:
> and can achieve efficiencies of up to 90% instead of 40-45% attainable by efficient turbine-driven thermal reactors.
A doubling of efficiency is extremely nice, don't get me wrong. But after you get to 90% there is simply not much further to go. On the other hand, semiconductor production has probably not even reached 1% of what is achievable. Non-flat structures are still seen as incredibly advanced, let alone true 3D chip manufacturing.
Bulk energy production will never see improvements comparable to those found in semiconductor manufacturing, simply because the systems don't have nearly as much "efficiency space" left to grow into.
I never claimed that energy production would increase in efficiency the way semiconductor production has. I just pointed out that anything based on the Carnot cycle is going to be horribly limited and should be considered an old-fashioned way of generating energy.
Was this really its best hope? I still have my fingers crossed for an Alcubierre drive using antimatter as an energy source.
Hasn’t work been done in this area recently? I remember seeing an article saying it might technically be possible with a hilariously large energy source, but I don’t know if that has been disproven.
Antimatter was to be used to generate the energy required, by annihilation of regular matte, not the antigravity itself. "Exotic matter" is undefined as of yet in that it could still exist as something else. Some people are confusing the two ideas, even though some (few) people probably did actually think anywhere would anti-gravitate, as it were.
We still don't know if regular matter is gravitationally repelled by antimatter. If so, we'd have violation of conservation of momentum and some interesting things might be possible. But I'm not holding my breath ;-)
Start with a big planet. Orbit a gas giant, burn most of it for fuel to get up to sufficient speed that your relativistic mass exceeds that of what is left (and to stop yourself zooming off in the meantime) and then pull the remainder along with you.
One of the questions in physical cosmology is, "why is there so little antimatter/matter mixing in the cosmos?". We can measure the mixing by looking for the annihilation spectrum (e.g. e+ e- -> 511 keV/c^2, which for distant extragalactic sources should redshift with the expansion of space). We can produce lots of e+ (positrons) and other antimatter here in laboratories, and so have a fair chunk of the total annihilation spectrum. We also have the spectra of lots and lots of galactic objects (stars, neutron stars, and so forth) and spectra from extragalactic events large (neutral hydrogen clouds) to small (supernovae). There is essentially no sign of known matter-antimatter interaction.
Our galaxy and other members of its cluster are, to high confidence, made essentially entirely of matter.
We have not yet totally precluded distant isolated galaxy clusters made essentially of antimatter, but the cosmic ray spectrum (we see lots of particles that originate at cosmological distances) puts increasingly strong constraints on the distribution and density of such galaxies: there aren't many in total, there's no dense blob of them. The oldest galaxies that we can obtain spectra are also closer together, and each non-observation of annihilation spectral lines puts ever-tighter constraints on other old galaxies' antimatter/matter mix. It is fairly safe to bet that there is simply no significant blob of antimatter in the observable universe, and that what antimatter there is comes from nuclear decays and high-energy astrophysical processes, and all of this antimatter quickly annihilates spatially near where it's produced.
However, that raises a trio of questions. (1) Did some process strongly disfavour the production of antimatter in the early universe, when hydrogen and helium was being produced in abundance? (2) if (1) is true, what is the nature of that process, and how could we see it experimentally? (3) if (1) is not true, where did all the antimatter go? There is an inversion of (3) as well: why didn't the disappearing antimatter take all the matter with it too?
The above is the essence of "the missing antimatter problem" or "the matter-antimatter asymmetry problem" or "baryon asymmetry" <https://en.wikipedia.org/wiki/Baryon_asymmetry> (that last name is for technical reasons, including that there are lots of antineutrinos, anti-photons (which are just photons), and (somewhat complicatedly) anti-gluons and antiquarks [endnote 1] in our universe) and there is a substantial academic literature by experimentalists and theorists.
A family of that literature explores the idea of segregation: matter and antimatter had similar abundances but were driven apart by some process in the early universe. The result is that there will be large (observable-universe-size-or-bigger) regions dominated by antimatter, and large regions (like ours) dominated by matter. But what is the nature of the process?
A subfamily exploring that last question considers the possibility that the segregating interaction is gravitational; a sub-sub-family considers that a change of sign of quantum spin can generate a gravitational difference. One approach to this is to treat quantum spin as a generator of the spin tensor in a modification of General Relativity in which the spin tensor generates the torsion tensor. In General Relativity there is no spacetime torsion at all, so in "semiclassical gravity" where one adds quantum fields to General Relativity (e.g. as in Stephen Hawking's famous 1974 "Black hole explosions?") matter and antimatter gravitate identically. Introducing non-vanishing spacetime torsion can change the nature of black holes enough that black hole evaporation could be very different. And if one couples particle spin to torsion, one could distinguish a black hole created by significant antimatter from a black hole created by practically no antimatter, and we would expect that to show up in the spectra of active galactic nuclei (generated by supermassive black holes) and in the gravitational wave detections of black hole mergers and black hole-neutron star collsions.
Apart from the lack of observational support (which one could sidestep by saying that there is basically no antimatter available to large black holes because it was all chased out of the observable universe by spacetime torsion effects), this quantum spin = spacetime torsion approach runs into a number of theoretical problems. The anti-hydrogen experiment that's the subject here adds a further problem that would need solving. Why would antimatter-matter gravitation today work differently from antimatter-matter gravitation in the early universe? If they work the same, then this experiment makes it unlikely that gravitational repulsin from torsion could solve the missing antimatter problem via early segregation.
This antihydrogen result also imperils proposals for theories of quantum gravity wherein quantum spin (other than that of the graviton or its string equivalent) is gravitationally relevant (but not necessarily arising in that family of string theories especially to solve the missing antimatter problem, i.e., "our theory has a gravitational spin-antispin term in the action which we don't mind because maybe it's too small to matter or maybe if it's big at high energies (like in the hot dense early universe) it can solve a big problem like the missing antimatter problem", essentially).
"The standard shorthand, “the proton is made from two up quarks and one down quark”, is really a statement that the proton has two more up quarks than up antiquarks, and one more down quark than down antiquarks. To make the glib shorthand correct you need to add the phrase “plus zillions of gluons and zillions of quark-antiquark pairs.” Without this phrase, one’s view of the proton is so simplistic that it is not possible to understand the LHC at all." (for which see a later followup, <https://profmattstrassler.com/articles-and-posts/largehadron...>)
We can do a lot of stuff with energy in various forms but gravity is just from mass which is quite difficult to control. Essentially we suck at fission and fusion at meaningful scales and we have a very narrow capability as well. I mean, to destroy mass equivalent to Mars in a short time frame is a cosmically cataclysmic nuke, then to not waste that energy, so you efficiently capture it and recreate the mass elsewhere in one huge fusion reaction. Maybe I talked past you and just daydreamed about Dr Manhattan stuff, maybe what it takes to emit gravity at will at some location, is much more difficult than just redirecting it which I dont have the tools to daydream about.
