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.
The warp field is created by the warp nacelles. How? Who knows.
The technical term is exotic matter. I think a better name would be Goshwoodentbeeneetium.
Like with voltages. One can be positive or negative if you swap "ground".
So yeah, agreed. A good thing to confirm, even if (especially if) they expected the result to be unexciting.
Seen that way it’s just insane that any kind of matter could fall up. See
https://en.wikipedia.org/wiki/Equivalence_principle
anti-matter falling up would be as crazy as superluminal neutrinos (which I have to admit I almost want to believe)
https://en.wikipedia.org/wiki/Negative_mass
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.
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:
https://news.mit.edu/2018/physicists-create-new-form-light-0...
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.
This is not true, elastic scattering is very common.
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.
[mass density, mass flux = momentum density]
[energy flux, stress]
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.
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.
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.
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
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.
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.
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.
https://en.m.wikipedia.org/wiki/Alcubierre_drive
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 know space is big and all that, but this seems like an irresponsible option.
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.
> 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"
(there's a parallel here to 'more negative results' and 'more replications')