4 ms·
The lesson here is an idea, no matter how implausible, can have legs as long as people want it to be true. That particular idea here is FTL travel (or communica
by cletus 4y ago
The lesson here is an idea, no matter how implausible, can have legs as long as people want it to be true. That particular idea here is FTL travel (or communication).
Nearly all of these ideas spring from a basic inability to understand the domain of a function. The domain is the set of values for which the function is defined. Any other values are undefined f(x) = 1/x for example has a domain of anything but 0.
So what happens is that people plug negative values into quantities like mass without any basis for what negative mass is and then use that as a basis for [insert FTL system here]. Why stop there? Why not use imaginary masses?
There is no negative mass. There is no negative energy. The domain of velocity is [0,c].
Even if you ignore that, no one goes far enough to calculate the energy requirements of, for example, "folding space" or creating a wormhole. If you do the math, it turns out you need to convert a significant portion of a stellar mass into energy.
The future isn't Star Trek nor Star Wars no matter how much you want it to be.
- tsimionescu 4y agoThe article here actually presents a warp drive that doesn't require negative mass/energy, but also doesn't move at speeds greater than c. It's interesting because it seems to be permitted by all of the laws of GR and also build-able from known materials, and it could represent a new mode of propulsion. It's also important to remember that space has expanded far faster than the speed of light in the past - c is only a limit for the speed that matter or energy can move at, it's not a limit for how space-time can change shape. We know this because the observable universe is ~93 billion light-years in size, but only ~13 billion years old - so it's size has grown faster than c. I'm with you on the idea that none of this means practical controlled faster-than-light travel will ever exist, though. Jury's still out on slower-than-light folding-space drives, though.
- cletus 4y agoDoesn't this warp drive depend on negative energy density (whatever that means) or has the fundamental flaw from out-of-domain values shifted in this version to something else?
- tsimionescu 4y agoThe article claims not: > 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. I'm no physicist to be able to evaluate the claim more deeply, but it is a published peer-reviewed article. The more famous Alcubierre drive, the one that can go faster than light, does require negative energy density.