8 ms·

I'm wondering if part of the problem with trying to come up with technology which allows us to propel ourselves vast distances "faster than the speed of light",

I'm wondering if part of the problem with trying to come up with technology which allows us to propel ourselves vast distances "faster than the speed of light", is to do with how we abstract/describe the problem (and the proposed solution) in language. For example; instead of saying "faster than the speed of light", would the problem not be better described using "faster than the speed of causality" ? After all, isn't c really just the speed of Causality in a vacuum? (i.e. the time it takes for a beam of light from a source to be detected at, say, a distance of 500,000 kilometres, is basically the rate at which Causality allows that light to get from the emitter to the detector.) And isn't the speed of Causality, basically like some kind of inertia-like quality of spacetime? (Apologies in advance - I'm trying to describe what's in my head as best I can using... language ;) ) For example - the speed of "light"/Causality through water is slower than the speed of "light"/Causality through a vacuum. (And mea culpa - I am a layman, trying to make sense of all this in as best a way I can. I'm not sure if what I wrote makes any kind of sense (it does in my head))

purple-again 6y ago
I’m as layman as you here but I assume it comes from the line of thought “just because light is contained to only go that fast doesn’t mean matter has to be constrained to only go that fast.” It’s a natural extension of knowing that humans can’t fly. We need only look up to see that constraint didn’t hold up to the rest of time nearly as well as contemporary humans assumed it would. How do we know that some immutable property of space/time causes light to travel at the speed it does rather than the other way around where some immutable property of light causes it to be incapable of traveling any faster (the old strap wings to a human and look now it can fly; so strap X to light and look now it can go faster to!) Again, the extent of my knowledge in this space is from Star Trek not science so please be gentle with my clear level of ignorance.
- scarygliders 6y ago
  > “just because light is contained to only go that fast doesn’t mean matter has to be constrained to only go that fast.” See, I'd try and frame it as "just because Causality constrains light to only go that fast..." and try to think what Causality is. And if Causality is a property of spacetime then how would I go about building a "Causality Engine" in order to alter spacetime in such a way that the speed of Causality can be broken ;) My mind is warped - pun intended.
  - rytill 6y ago
    Isn’t the only reason the speed of causality is the speed of light because light is the fastest thing? And if you were able to go faster than it, that new speed would be the speed of causality?
    - marcosdumay 6y ago
      There is an interesting property of the speed of causality, that it is fixed independently of the observer (as in, any observer will measure the same speed). Our mechanics allow only one such speed, and if you try to use one that doesn't have this property for causality, you'll get all kinds of paradoxes. But it's probably something that can be solved. All said, the reason we assume causality moves at that speed is because it agrees with the experiments.
- jodrellblank 6y ago
  As a blind-leading-the-blind layman answer, if you shove a car forwards it will move slowly (ignore air/tyre resistance and such). The same strength shove hardly moves an artic truck, it wobbles a Ford F-150, it pushes a sedan, it rolls a small sports car, without air resistance and axel friction, it’s only the mass which resists your shoving and determines the speed. and you can imagine waving a magic wand over the car to lower its mass then the same shove pushes it faster and faster. At the mass of a ball bearing the car pings away. Like a tennis racket swing can’t move a car but can move a tennis ball at 100mph. Until there is no mass left, at that point any shove and it skitters away enormously fast. As mass drops the shove pushes it faster. As mass goes to zero, it goes “infinitely” fast. There isn’t any mass left to remove, so the only way you can speed it up from here is to push harder instead... but now as soon as you touch it at all, at any pressure, it skitters away and you aren’t touching it anymore so you can’t push - damnit. The first inkling whisker of a skin cell touching the car and it’s off, the time it takes to “wind up” your shove power is too slow, the massless car is 300,000m away in a thousandth of a second. You can’t keep your hand on it, let alone go faster than it to provide more pushing force! In fact the only way you can move your hand fast enough to keep up with it, so you can keep touching it long enough to give it more push, is if your hand also has no mass. And now your massless hand can’t be pushed by your real muscles for the same reason, once stuff has no mass you can’t get a grip on it. So pushing harder is out. Maybe you can push it faster in a non-mechanical way like electromagnetically? Ok, you send some magnetic waves after it. Photons. They have no mass, so they travel at the same speed as well. They can never catch the car to push it. Like a game of tag where you run behind someone waving your arm at them but never quite able to touch them, you sure can’t push them harder if you can’t ever quite touch them. Nothing can catch up to provide more push. So it can’t go faster than this “infinite” speed. > How do we know that some immutable property of space/time causes light to travel at the speed it does rather than the other way around where some immutable property of light causes it to be incapable of traveling any faster Because the speed isn’t how fast light goes, it’s how fast spacetime lets massless things go through it and light happens to be a massless thing. If mass is what resists movement, and you take all of it away, there isn’t any way to go faster because you can’t take more mass away than all of it. (Wish I’d written this with whacking tennis racket on a car, bowling ball, baseball, ball bearing...) seems easier to imagine.
mybandisbetter 6y ago
I've often thought that "the speed of causality" would be a much better name for it. Interesting you landed on the same.
whimsicalism 6y ago
Your claim is that we've had trouble coming up with technology going FTL because physicists forget that the speed of light is the same as the speed of causality? I'm probably misunderstanding what you're saying.
- scarygliders 6y ago
  It's not really a claim, it was a pondering - a thinking out aloud. And it's more to do with the use of language to describe the problem (how to break the "light barrier") than forgetting something. And the use of language in abstracting/describing solutions to it.
  - krapp 6y ago
    That the speed of light is invariant in a vacuum is a result of Einstein's theory of special relativity[0,1] and Maxwell's field equations[2]. These may be described generally with language like "speed of light" but they were described specifically and tested using math and science. And at this point, these are probably the most thoroughly tested and proven principles in science, since they underpin everything from cosmology to quantum mechanics to chemistry (and by extension biology) and a lot of our modern technology such as satellites (which have to take special relativity into account) and microchip design, for which quantum effects are relevant. [0]https://en.wikipedia.org/wiki/Special_relativity https://en.wikipedia.org/wiki/Special_relativity [1]https://en.wikipedia.org/wiki/Speed_of_light https://en.wikipedia.org/wiki/Speed_of_light [2]https://web.pa.msu.edu/courses/2000fall/phy232/lectures/emwaves/maxwell.html https://web.pa.msu.edu/courses/2000fall/phy232/lectures/emwa...
  - magicalhippo 6y ago
    But physicist don't usually use language when abstracting or describing solutions. They use math. And in the math it's pretty clear what's going on.
    - scarygliders 6y ago
      The initial problem has to be thought of and abstracted in language. It merely gets translated into math after that - math being a tool used to attempt to solve that problem. No one thinks and speaks purely in math. It must be language, then math, then language again to help describe and explain the solution which was found using math.
Misdicorl 6y ago
Separating the terms/ideas may actually be useful to address a common misconception you illustrate here. Light does change speed in water, but causality does not
- whimsicalism 6y ago
  > Light does change speed in water, but causality does not Well, the speed that the photons travel between the water atoms is still c.
- scarygliders 6y ago
  The concept I have in my head if I can describe it well enough, is that the speed of Causality is different in water, than it is in a vacuum. An underwater explosion travels slower in water than it does in a vacuum. That's not just to do with the coefficient of friction of the water. The light from the explosion will take longer to reach you than it would if you and the explosion were in a vacuum. Which leads me to another thought - does that mean that the matter of water is basically just another form of spacetime, in which the speed of Causality is different from the speed of Causality in spacetime in a vacuum?
  - Filligree 6y ago
    Nah. The speed of light is slower in water, yes, which is why Cherenkov radiation exists -- that's basically the photon equivalent of a supersonic shockwave. The speed of causality doesn't change, and it's easy to demonstrate that by throwing particles through it at superluminal speeds; nuclear reactors do it all day long.
    - TeMPOraL 6y ago
      Wait. Isn't that entirely explained by the light being repeatedly absorbed and re-emitted after a short delay? But otherwise travelling at c?
      - emikulic 6y ago
tzs 6y ago
There's an episode of PBS Space Time about this, "The Speed of Light is NOT About Light" [1], which comes pretty close to making the same points you are making. It might be useful to watch this earlier episode, "Are Space and Time an Illusion?" [2], first. There is a later episode (or maybe a couple of them) that go into how interactions with the Higgs field make it so things with mass travel slowed than the speed of causality. To tie back to the warp drive news, they have an episode that would be a good place to start on warp drives, "Is The Alcubierre Warp Drive Possible?" [3]. There's also "Superluminal Time Travel + Time Warp Challenge Answer" [4], and "Will Wormholes Allow Fast Interstellar Travel?" [5]. A non-warp unknown physics drive that comes up a lot also got an episode, "The EM Drive: Fact or Fantasy?" [6]. There is at least one episode covering interstellar travel without using any unknown physics, "5 REAL Possibilities for Interstellar Travel" [7]. The scope of the series is basically anything vaguely connected to astronomy, cosmology, and quantum mechanics, and the episodes are all pretty short (5-12 minutes), so it is a great thing to watch when you've got a short wait for something. Here's the series home page [8], and their YouTube channel [9]. Also on the PBS streaming app, for those who like to get their physics on their big screen TVs. [1] https://www.youtube.com/watch?v=msVuCEs8Ydo https://www.youtube.com/watch?v=msVuCEs8Ydo [2] https://www.youtube.com/watch?v=YycAzdtUIko https://www.youtube.com/watch?v=YycAzdtUIko [3] https://www.youtube.com/watch?v=94ed4v_T6YM https://www.youtube.com/watch?v=94ed4v_T6YM [4] https://www.youtube.com/watch?v=HUMGc8hEkpc https://www.youtube.com/watch?v=HUMGc8hEkpc [5] https://www.youtube.com/watch?v=ldVDM-v5uz0 https://www.youtube.com/watch?v=ldVDM-v5uz0 [6] https://www.youtube.com/watch?v=hqoo_4wSkdg https://www.youtube.com/watch?v=hqoo_4wSkdg [7] https://www.youtube.com/watch?v=EzZGPCyrpSU https://www.youtube.com/watch?v=EzZGPCyrpSU [8] https://www.pbs.org/show/pbs-space-time/ https://www.pbs.org/show/pbs-space-time/ [9] https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g
- mech422 6y ago
  I love these... Though the short length is both a blessing and a bane. Just enough to peak your curiosity, but not long enough to really dig into something.

purple-again 6y ago

I’m as layman as you here but I assume it comes from the line of thought “just because light is contained to only go that fast doesn’t mean matter has to be constrained to only go that fast.” It’s a natural extension of knowing that humans can’t fly. We need only look up to see that constraint didn’t hold up to the rest of time nearly as well as contemporary humans assumed it would. How do we know that some immutable property of space/time causes light to travel at the speed it does rather than the other way around where some immutable property of light causes it to be incapable of traveling any faster (the old strap wings to a human and look now it can fly; so strap X to light and look now it can go faster to!) Again, the extent of my knowledge in this space is from Star Trek not science so please be gentle with my clear level of ignorance.

scarygliders 6y ago
> “just because light is contained to only go that fast doesn’t mean matter has to be constrained to only go that fast.” See, I'd try and frame it as "just because Causality constrains light to only go that fast..." and try to think what Causality is. And if Causality is a property of spacetime then how would I go about building a "Causality Engine" in order to alter spacetime in such a way that the speed of Causality can be broken ;) My mind is warped - pun intended.
- rytill 6y ago
  Isn’t the only reason the speed of causality is the speed of light because light is the fastest thing? And if you were able to go faster than it, that new speed would be the speed of causality?
  - marcosdumay 6y ago
    There is an interesting property of the speed of causality, that it is fixed independently of the observer (as in, any observer will measure the same speed). Our mechanics allow only one such speed, and if you try to use one that doesn't have this property for causality, you'll get all kinds of paradoxes. But it's probably something that can be solved. All said, the reason we assume causality moves at that speed is because it agrees with the experiments.
jodrellblank 6y ago
As a blind-leading-the-blind layman answer, if you shove a car forwards it will move slowly (ignore air/tyre resistance and such). The same strength shove hardly moves an artic truck, it wobbles a Ford F-150, it pushes a sedan, it rolls a small sports car, without air resistance and axel friction, it’s only the mass which resists your shoving and determines the speed. and you can imagine waving a magic wand over the car to lower its mass then the same shove pushes it faster and faster. At the mass of a ball bearing the car pings away. Like a tennis racket swing can’t move a car but can move a tennis ball at 100mph. Until there is no mass left, at that point any shove and it skitters away enormously fast. As mass drops the shove pushes it faster. As mass goes to zero, it goes “infinitely” fast. There isn’t any mass left to remove, so the only way you can speed it up from here is to push harder instead... but now as soon as you touch it at all, at any pressure, it skitters away and you aren’t touching it anymore so you can’t push - damnit. The first inkling whisker of a skin cell touching the car and it’s off, the time it takes to “wind up” your shove power is too slow, the massless car is 300,000m away in a thousandth of a second. You can’t keep your hand on it, let alone go faster than it to provide more pushing force! In fact the only way you can move your hand fast enough to keep up with it, so you can keep touching it long enough to give it more push, is if your hand also has no mass. And now your massless hand can’t be pushed by your real muscles for the same reason, once stuff has no mass you can’t get a grip on it. So pushing harder is out. Maybe you can push it faster in a non-mechanical way like electromagnetically? Ok, you send some magnetic waves after it. Photons. They have no mass, so they travel at the same speed as well. They can never catch the car to push it. Like a game of tag where you run behind someone waving your arm at them but never quite able to touch them, you sure can’t push them harder if you can’t ever quite touch them. Nothing can catch up to provide more push. So it can’t go faster than this “infinite” speed. > How do we know that some immutable property of space/time causes light to travel at the speed it does rather than the other way around where some immutable property of light causes it to be incapable of traveling any faster Because the speed isn’t how fast light goes, it’s how fast spacetime lets massless things go through it and light happens to be a massless thing. If mass is what resists movement, and you take all of it away, there isn’t any way to go faster because you can’t take more mass away than all of it. (Wish I’d written this with whacking tennis racket on a car, bowling ball, baseball, ball bearing...) seems easier to imagine.

mybandisbetter 6y ago

I've often thought that "the speed of causality" would be a much better name for it. Interesting you landed on the same.

whimsicalism 6y ago

Your claim is that we've had trouble coming up with technology going FTL because physicists forget that the speed of light is the same as the speed of causality? I'm probably misunderstanding what you're saying.

scarygliders 6y ago
It's not really a claim, it was a pondering - a thinking out aloud. And it's more to do with the use of language to describe the problem (how to break the "light barrier") than forgetting something. And the use of language in abstracting/describing solutions to it.
- krapp 6y ago
  That the speed of light is invariant in a vacuum is a result of Einstein's theory of special relativity[0,1] and Maxwell's field equations[2]. These may be described generally with language like "speed of light" but they were described specifically and tested using math and science. And at this point, these are probably the most thoroughly tested and proven principles in science, since they underpin everything from cosmology to quantum mechanics to chemistry (and by extension biology) and a lot of our modern technology such as satellites (which have to take special relativity into account) and microchip design, for which quantum effects are relevant. [0]https://en.wikipedia.org/wiki/Special_relativity https://en.wikipedia.org/wiki/Special_relativity [1]https://en.wikipedia.org/wiki/Speed_of_light https://en.wikipedia.org/wiki/Speed_of_light [2]https://web.pa.msu.edu/courses/2000fall/phy232/lectures/emwaves/maxwell.html https://web.pa.msu.edu/courses/2000fall/phy232/lectures/emwa...
- magicalhippo 6y ago
  But physicist don't usually use language when abstracting or describing solutions. They use math. And in the math it's pretty clear what's going on.
  - scarygliders 6y ago
    The initial problem has to be thought of and abstracted in language. It merely gets translated into math after that - math being a tool used to attempt to solve that problem. No one thinks and speaks purely in math. It must be language, then math, then language again to help describe and explain the solution which was found using math.

Misdicorl 6y ago

Separating the terms/ideas may actually be useful to address a common misconception you illustrate here. Light does change speed in water, but causality does not

whimsicalism 6y ago
> Light does change speed in water, but causality does not Well, the speed that the photons travel between the water atoms is still c.
scarygliders 6y ago
The concept I have in my head if I can describe it well enough, is that the speed of Causality is different in water, than it is in a vacuum. An underwater explosion travels slower in water than it does in a vacuum. That's not just to do with the coefficient of friction of the water. The light from the explosion will take longer to reach you than it would if you and the explosion were in a vacuum. Which leads me to another thought - does that mean that the matter of water is basically just another form of spacetime, in which the speed of Causality is different from the speed of Causality in spacetime in a vacuum?
- Filligree 6y ago
  Nah. The speed of light is slower in water, yes, which is why Cherenkov radiation exists -- that's basically the photon equivalent of a supersonic shockwave. The speed of causality doesn't change, and it's easy to demonstrate that by throwing particles through it at superluminal speeds; nuclear reactors do it all day long.
  - TeMPOraL 6y ago
    Wait. Isn't that entirely explained by the light being repeatedly absorbed and re-emitted after a short delay? But otherwise travelling at c?
    - emikulic 6y ago

tzs 6y ago

There's an episode of PBS Space Time about this, "The Speed of Light is NOT About Light" [1], which comes pretty close to making the same points you are making. It might be useful to watch this earlier episode, "Are Space and Time an Illusion?" [2], first. There is a later episode (or maybe a couple of them) that go into how interactions with the Higgs field make it so things with mass travel slowed than the speed of causality. To tie back to the warp drive news, they have an episode that would be a good place to start on warp drives, "Is The Alcubierre Warp Drive Possible?" [3]. There's also "Superluminal Time Travel + Time Warp Challenge Answer" [4], and "Will Wormholes Allow Fast Interstellar Travel?" [5]. A non-warp unknown physics drive that comes up a lot also got an episode, "The EM Drive: Fact or Fantasy?" [6]. There is at least one episode covering interstellar travel without using any unknown physics, "5 REAL Possibilities for Interstellar Travel" [7]. The scope of the series is basically anything vaguely connected to astronomy, cosmology, and quantum mechanics, and the episodes are all pretty short (5-12 minutes), so it is a great thing to watch when you've got a short wait for something. Here's the series home page [8], and their YouTube channel [9]. Also on the PBS streaming app, for those who like to get their physics on their big screen TVs. [1] https://www.youtube.com/watch?v=msVuCEs8Ydo https://www.youtube.com/watch?v=msVuCEs8Ydo [2] https://www.youtube.com/watch?v=YycAzdtUIko https://www.youtube.com/watch?v=YycAzdtUIko [3] https://www.youtube.com/watch?v=94ed4v_T6YM https://www.youtube.com/watch?v=94ed4v_T6YM [4] https://www.youtube.com/watch?v=HUMGc8hEkpc https://www.youtube.com/watch?v=HUMGc8hEkpc [5] https://www.youtube.com/watch?v=ldVDM-v5uz0 https://www.youtube.com/watch?v=ldVDM-v5uz0 [6] https://www.youtube.com/watch?v=hqoo_4wSkdg https://www.youtube.com/watch?v=hqoo_4wSkdg [7] https://www.youtube.com/watch?v=EzZGPCyrpSU https://www.youtube.com/watch?v=EzZGPCyrpSU [8] https://www.pbs.org/show/pbs-space-time/ https://www.pbs.org/show/pbs-space-time/ [9] https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g

mech422 6y ago
I love these... Though the short length is both a blessing and a bane. Just enough to peak your curiosity, but not long enough to really dig into something.