Positive Energy Warp Drive from Hidden Geometric Structures • Hacker News Board

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#41

Post by nine_k » Tue, Jul 13, 2021, 3:02 AM UTC

gary_0 wrote: post #30

px43 wrote: post #27

Earlier quoted context omitted.

> turn their FTL ship around I feel like this is the part that would probabally be hard (ie not possible) when going faster than light, assuming such a thing is possible. Also whatever magical space warp it is that lets you go that fast could presumably also obscure your ability to see yourself in the distance.

"Turning around" is just stopping at some point (ie. some inertial reference frame) and then accelerating in the opposite direction with your FTL drive. You have all the time in the world to do this maneuver because you're already effectively in the past: https://physics.stackexchange.com/a/54242

There's no absolute coordinate system in space, so there's no way to "stop". You can only change your velocity relative to some other object, e.g. your past self in the example. What counts is acceleration / deceleration.

Slowing down to reach the speed of light might be as hard as speeding up to reach it; I remember it played a role in the theory of tachyons, hypothetical FTL elementary particles which could not be slowed down.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#42

Post by tobmlt » Tue, Jul 13, 2021, 3:03 AM UTC

SmellTheGlove wrote: post #2

This sounds pretty amazing, but I also have no real idea what I'm reading. > A modest numerical analysis is carried out on a set of example configurations, finding total energy requirements four orders of magnitude smaller than the solar mass. Can someone smarter than me say whether this is within the (reasonable-ish?) realm of matter-antimatter reactions? Like Star Trek!? 4 orders of magnitude less than the sun's ma…

The paper also gives recommendation for a starting point for some finite element modeling and optimization for field configurations requiring less energy than that, improving other properties and such. (FEM modeling to search the irrotational sector of the Hamiltonian constraint...) They mentioned this with a fair amount of enthusiasm - sounding like there may be room to optimize.

I wonder what the gradients look like.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#43

Post by jack_pp » Tue, Jul 13, 2021, 3:04 AM UTC

cletus wrote: post #39

The lesson we should really take here is the power of wishful thinking. People dearly want to believe in FTL travel. Without it, the Universe just seems so vast, empty and distant. The truth is it is and it isn't. It's only really that on our current time scales. Not to be a broken record (there's some new variation on some old idea like every week it seems), but I'm firmly in the camp that believes FTL isn't possibl…

Isn't there evidence starting to surface that we have actually detected alien contact?

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#44

Post by samplatt » Tue, Jul 13, 2021, 3:05 AM UTC

akiselev wrote: post #5

SmellTheGlove wrote: post #2

This sounds pretty amazing, but I also have no real idea what I'm reading. > A modest numerical analysis is carried out on a set of example configurations, finding total energy requirements four orders of magnitude smaller than the solar mass. Can someone smarter than me say whether this is within the (reasonable-ish?) realm of matter-antimatter reactions? Like Star Trek!? 4 orders of magnitude less than the sun's ma…

The first paper detailing the Alcubierre drive required exotic particles with negative mass to achieve a spacetime bubble (soliton) which is an issue since particles with negative mass have never been observed. The next big paper figured out how to do it with regular matter and it brought the requirements down to the energy equivalent of four solar masses. That would put it squarely into the realm of a type II or III…

>It'd be able to enter warp once.

...why once? Are you assuming all matter+antimatter is destroyed in the single trip? If you have x amount of critical material, could you not warp for half the distance of the "fuel" in your "tank" and then come back?

IANAPhyicist. I'm assuming that if we have the ability to contain and harvest energy from a matter/antimatter reaction then we also have the ability to stop it & start it at will.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#45

Post by jchrisa » Tue, Jul 13, 2021, 3:05 AM UTC

nine_k wrote: post #38

sigmoid10 wrote: post #15

Earlier quoted context omitted.

General relativity actually tells us nothing about whether causality is absolute. You can easily make up spacetime configurations that violate causality and still conform to general relativity. It's just that most people believe that causality should be protected, because... well it would be really weird if it wasn't. But it's just a conjecture and not like a theorem or anything.

AFAICT, GR is symmetric in relation of the direction of time, as are most other important physical theories. What may add the arrow of time is the second law of thermodynamics: a statistical evolution of a system is not symmetric. I wonder now how a violation of causality could either circumvent of contradict the second law.

This is the content I visit the orange site for. Thanks.

To add something substantive, my question to the thread is: anyone here have thoughts on how these questions relate to McTaggart's unreality of time? https://en.wikipedia.org/wiki/A_series_and_B_series

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#46

Post by mcswell » Tue, Jul 13, 2021, 3:07 AM UTC

krapp wrote: post #6

Yeah... using Euler geometries to generate warp fields always seems like the obvious solution at first, until you wind up stranded in hyperspace with gimbal lock. That's why you need to use quaternions.

Don't worry, your R2 unit can fix it.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#47

Post by IdiocyInAction » Tue, Jul 13, 2021, 3:07 AM UTC

jack_pp wrote: post #43

cletus wrote: post #39

The lesson we should really take here is the power of wishful thinking. People dearly want to believe in FTL travel. Without it, the Universe just seems so vast, empty and distant. The truth is it is and it isn't. It's only really that on our current time scales. Not to be a broken record (there's some new variation on some old idea like every week it seems), but I'm firmly in the camp that believes FTL isn't possibl…

Isn't there evidence starting to surface that we have actually detected alien contact?

You mean that UAP stuff? Occam's razor says this is probably some electronic countermeasure stuff by the US or something.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#48

Post by AnimalMuppet » Tue, Jul 13, 2021, 3:08 AM UTC

javajosh wrote: post #29

a1369209993 wrote: post #28

Earlier quoted context omitted.

> SR is 2 assertions, really: first, that the laws of physics are invariant in all reference frames, and second (and far stranger), that the speed of light is invariant in all reference frames. Technically that's only one assertion (that is, the second is a strict subset of the first).

No, it isn't. Light is unique in this way.

Correct. In a bit more detail:

Here's the grid coordinate system for the streets in my town. One intersection is (0, 0). But in the grid system used by the next town over, that same intersection is (100, 200). And that's fine - we're just shifting the origin, which changes all the numbers.

The same thing happens with velocity. If I'm on the ground, "stationary" means that you're not moving with respect to the ground. If you're in an airplane, "stationary" means that you're sitting in your seat, and you see me on the ground moving toward the back of the plane at 550 MPH. And that's still fine - we just shifted the origin of velocity.

Light is unique in that, when you shift the origin of velocity, it's speed is still the same number. No other velocity transforms that way.

(Well... light isn't quite unique. The speed of light is unique in that way. But gravitational waves also travel at the speed of light.)

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#49

Post by solarengineer » Tue, Jul 13, 2021, 3:11 AM UTC

cletus wrote: post #39

The lesson we should really take here is the power of wishful thinking. People dearly want to believe in FTL travel. Without it, the Universe just seems so vast, empty and distant. The truth is it is and it isn't. It's only really that on our current time scales. Not to be a broken record (there's some new variation on some old idea like every week it seems), but I'm firmly in the camp that believes FTL isn't possibl…

What if we're the first species to explore FTL? What if the Universe is vast enough that FTL-capable specifies are busy in other parts of the Galaxy or the Universe?

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#50

Post by godelski » Tue, Jul 13, 2021, 3:13 AM UTC

Everyone always talks about FTL travel for spacecraft, but there's also an interesting perspective from weapons side (and this a reason to be a bit careful and think about some ethics as we move along). A FTL kinetic weapon would be devastating. If it comes with a collapsing warp bubble then there's basically a gamma ray "gun" that travels right in front of your mass that is traveling at tremendous speeds. You look at impacts on the ISS and you can see how much damage a small object does[0]. This is also especially important when trying to develop such a device for travel as you'll probably be sending small objects before a spaceship, or rather a "bullet". Where that object ends up may be in serious danger.

Edit: And as others are pointing out, communication. There's a whole slew of technologies that could be improved/invented if you can move things/information FTL.

[0] https://www.esa.int/Safety_Security/Space_Debris/Hyperveloci...