Is Speed of Light Human Travel Possible?

[Chakah]

There's only one kind of infinity, and that's infinity. There's no infinity+1, nor infinity-1.

How many kinds of infinity are there?



http://vihart.com/how-many-kinds-of-infinity-are-there/

[WowIsDead64]

What you should do - is throw Theory of relativity away, cuz it's based purely on classic physic and it's relation between energy and momentum is actually just a direct consequence of applying wave equation to matter wave. Therefore maximal speed depends purely on properties of wave - front velocity, phase velocity and group velocity. Currently it's known, that phase velocity and group velocity can be higher, than speed of light, but front velocity can't - it's limitation of "environment", where matter wave is propagating. Currently this "ether" lies beyond our control - we can't change it's properties.

Relation between energy/velocity and momentum in classic and theory of relativity:

[Chakah]

Or rather, do you think it will be possible for humans to travel at light speed any time in the near future?
@Eleccybubb thoughts?

Maybe. Depends on your definition of 'near' for starters. The speed of light is a real limit, but there could be ways to cheat. Lots of difficult engineering/physics advances are required before we get there.

I can't believe this thread has made it to 9 pages without anyone linking this video:

[Garnier Fructis]

You are contradicting yourself. Something can hypothetically correlate with something else faster than the speed of light would allow. That leaves room for doubt. Hence - we are not 100% on the whole "c" is the limit. There are also other theoretical works that we can not replicate yet with our technology, but that are sound mathematically, like Scharnhorst effect, which allows a photon to travel faster than the "c" constant. Same goes for quantum tunneling.
All I am saying is that there is room for doubt in both: "c" as a numerical value that we know of (it might be larger), and that there might be conditions when other particles can travel faster than photons.

No, I'm really not. Entanglement effects things across huge distances because in essence those things were never separated to begin with. It doesn't contradict the speed limit, because if you were to change something at point A and it effected a change at point B, nothing at point B can discern this in less time than it would take a photon to travel from A to B. So no information can be communicated faster than the speed of light, even with entanglement.

In fact you don't even need quantum to have 'things' moving faster than light. Shadows can 'move' faster than light. It doesn't violate the speed limit for similar reasons.

Quantum tunneling falls basically into the same category as entanglement, in that information isn't communicated faster than light.

Scharnhorst effect is interesting but untestable. I will say that when you write "we can not replicate yet with our technology", you're presupposing that this effect actually exists. It might. It also might not.



Look, I'm not saying we are 100% on c. There's unknown physics, so we absolutely can't be sure. But trying to support it with various quantum mechanical effects is dubious, especially since much work has been done over the decades to resolve apparent FTL violations.

[cubby]

Or rather, do you think it will be possible for humans to travel at light speed any time in the near future?
@Eleccybubb thoughts?

Current physics says speed of light is not possible. So 99.99999%C is max. However, many other theoretical workarounds could push humans to actually move faster than the speed of light.

[haxartus]

It's always slower in local scale. Otherwise it'll violate causality.

It's funny how people think they are qualified to talk about the speed of light, while not understanding exactly how causality works.

Any travel, faster than the speed of light in vacuum, essentially would allow the traveler to travel back in time. This is why it is regarded that faster than light travel is impossible, not because someone measured it and decided that that's the fastest it could go.

[WowIsDead64]

No, I'm really not. Entanglement effects things across huge distances because in essence those things were never separated to begin with. It doesn't contradict the speed limit, because if you were to change something at point A and it effected a change at point B, nothing at point B can discern this in less time than it would take a photon to travel from A to B. So no information can be communicated faster than the speed of light, even with entanglement.

In fact you don't even need quantum to have 'things' moving faster than light. Shadows can 'move' faster than light. It doesn't violate the speed limit for similar reasons.

Quantum tunneling falls basically into the same category as entanglement, in that information isn't communicated faster than light.

Scharnhorst effect is interesting but untestable. I will say that when you write "we can not replicate yet with our technology", you're presupposing that this effect actually exists. It might. It also might not.



Look, I'm not saying we are 100% on c. There's unknown physics, so we absolutely can't be sure. But trying to support it with various quantum mechanical effects is dubious, especially since much work has been done over the decades to resolve apparent FTL violations.

Interesting thing - for wave there is no "future" and "past", cuz wave can always be split into waves, that are infinite in space in time, via Fourier transform and interact continuously. So... Entanglement can be just a consequence of waves, knowing, what will happen in advance.

[apepi]

Even if we can go as fast as the speed of light, the problem is about trying to be able to slow down and not dying from it. Those are the two problems, to be able to go at the speed of light and being able to slow down from that.

[WowIsDead64]

Problem with speed of light - is problem with simple fact, that energy is actually means "how fast time goes", i.e. speed of time. So, energy = speed in time and momentum = speed in space. Simple fact, that this two are related, cuz they're actually just a frequency and wavelength of some wave - means, that increase of speed in space will always mean increase of speed in time and speed in time will always be higher due to addition of mass to it. And as <speed> = <speed in space>/<speed in time> - <speed> will never exceed some constant. In order to make it happen - mass should be imaginary number due to E^2 - p^2 = m^2 equation.

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P.S. Hey guys! Is there anybody good at math and physics here to explain, how does this equation

turn into
(q = e, n can be omitted)
according to principle of least action (i.e. Fermat's principle in case of wave)?

All articles tell, that
(Lagrangian function)
but don't explain or prove it.

[Danuru]

There's a shit ton more issues than simply "bending spacetime". While not ruled out as impossible, the Alcubierre drive makes some seriously problematic assumptions. The only reason the Alcubierre drive is entertained is because it is an ADM formalism that maintains consistency with the laws of relativity.

Never said it was perfect. However, we do not know for certain that an Alcubierre Drive is impossible, while we do know accessing the infinite amount of energy required to conventionally break the "light barrier" is. And that was my point: Improbable will always be more likely than impossible.

[Paperfox]

Only in books and movies, and even then the warp engine (or whatever it's called) will only work as long as the plot says it will.

OT: Do you realize that we don't even know what the speed of light actually is. The devices we use to measure it are the same ones we created. Even Einstein alluded to this.

[WowIsDead64]

There's a lot of mathematical consequences that demand c to be a speed limit. I say this because philosophical consequences aren't universally convincing.

It's possible - it just requires phase velocities of matter waves to be, OMG, below c. They're commonly higher than c, due to w^2 - (c * k)^2 > 0, i.e. vp = w/k > c. And for other types of waves there is nothing special or strange in this situation - it's 100% possible and even common.

I just don't think, that travelling back in time wouldn't actually happen in case of v > c. All effects of theory of relativity actually happen due to Doppler effect. In case of v > c supersonic effect would most likely happen - i.e. sonic boom.

Static object:

v < c:

v = c - it's light:

v > c:


Theory of relativity simply assumes, that in order to be detected at the edge of wavefront by external observer, so v will still be equal to c in observer's frame of reference and "v = c in all frames of reference" law won't be broken, while it's actually in front of it, system should travel back in time. But bremsstrahlung due to sonic boom is more possible - Cherenkov radiation.

[Adam Jensen]

Then reduce the mass to 0.

And we have no way of knowing how to do that without destroying the object, or how to exceed C. Photons go at C. They don't go faster, or slower.

[WowIsDead64]

And we have no way of knowing how to do that without destroying the object, or how to exceed C. Photons go at C. They don't go faster, or slower.

Reducing mass to 0 isn't enough - it would only provide v = c. Mass should become imaginary number, so m^2 < 0 and (c * k)^2 > w^2. We talk about hypothetical Tachyon here.

[dadev]

Problem with speed of light - is problem with simple fact, that energy is actually means "how fast time goes", i.e. speed of time. So, energy = speed in time and momentum = speed in space. Simple fact, that this two are related, cuz they're actually just a frequency and wavelength of some wave - means, that increase of speed in space will always mean increase of speed in time and speed in time will always be higher due to addition of mass to it. And as <speed> = <speed in space>/<speed in time> - <speed> will never exceed some constant. In order to make it happen - mass should be imaginary number due to E^2 - p^2 = m^2 equation.

- - - Updated - - -

P.S. Hey guys! Is there anybody good at math and physics here to explain, how does this equation

turn into
(q = e, n can be omitted)
according to principle of least action (i.e. Fermat's principle in case of wave)?

All articles tell, that
(Lagrangian function)
but don't explain or prove it.

First one seems like the Dirac equation with a 4-vector potential. Then the electric component is dropped, and the second seems a bit wrong as there should be a cross with velocity (rather than dot), and it makes it just the time average solution for the Dirac equation above (just apply Ehrenfest's theorem), which is obviously a charged particle in a magnetic field. And the last one is just the negative energy density of the magnetic field, or alternatively the principal eigenvalue of Maxwell's stress tensor for the same field.
Not sure what more can be said about those...

[God Save The King]

According to some basic principles of physics, speed of light travel isn't reachable. It will take an infinite amount of energy to reach it. But going almost the speed of light is plausible, at least nothing in our understanding of physics says we cannot.

[Protean]

I think you mischaracterize Warp here by quite a bit. The idea of a warp drive is more similar to the creation of a direct wormhole and not so much to a hyperspace drive. You do not go to a different universe (not sure what that would even imply), you just compress the space in front of you, by "putting" large amounts of energy (and thus mass) in it that contracts it, pass through the contracted space and then let it expand again after you are through.

- - - Updated - - -



What about it? Things can move apart faster than the speed of light, this does not violate that there is no information transfer faster than light.

Except it's possible to make something that moves faster than the speed of light. You basically point a laser at the moon and if you rotate it fast enough the dot will move across the moon's surface faster than light can travel the same distance, were you standing on the spot where the laser hits and shining a flashlight in the direction it is going.

[Uzkin]

All articles tell, that
(Lagrangian function)
but don't explain or prove it.

Formally, Lagrangians are not "proven" or "derived" in Lagrangian mechanics; they are postulated. Their form is justified if their insertion into Euler-Lagrange equations leads to the "correct" equations of motion.

The Lagrangian you gave above is a part of the full Lagrangian density of electromagnetic field; specifically, the part which corresponds to magnetic field. It represents (the negative of) the energy density of magnetic field, a result which is of course well known in the classical theory of electromagnetism. As such, it is not surprising that such a term should occur in the Lagrangian density function. As long as the Lagrangian density leads to the Maxwell equations its form is justified.

Edit. Oops, I see dadev already answered this.

[Elim Garak]

Except it's possible to make something that moves faster than the speed of light. You basically point a laser at the moon and if you rotate it fast enough the dot will move across the moon's surface faster than light can travel the same distance, were you standing on the spot where the laser hits and shining a flashlight in the direction it is going.

Nope. It doesn't move faster than light. Because it's not the spot that moves - it's the laser source. Nothing moves faster than light in that case. The spot is not a real physical object - it's just the place at which the laser points.

Just have two lasers pointing in OPPOSITE directions. But only one is turned on at the same time. Then switch... BAM! look at that speed, because the spot is at the opposite side a light second away. How did it get there so fast? it didn't.

[Garnier Fructis]

Interesting thing - for wave there is no "future" and "past", cuz wave can always be split into waves, that are infinite in space in time, via Fourier transform and interact continuously. So... Entanglement can be just a consequence of waves, knowing, what will happen in advance.

I've studied basically all of the topics you just mentioned at one level or another and I can't make heads or tails of what you're writing here.