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Faster than light travel and time travel are both fundamentally impossible in our universe and can't be achieved. I'm sure we'll learn all sorts of cool things

Faster than light travel and time travel are both fundamentally impossible in our universe and can't be achieved. I'm sure we'll learn all sorts of cool things looking for ways in. The reality is these will sadly live only in science fiction. There are plenty of things that are fundamentally impossible in our universe, faster than light travel being one of them.

ctoth 5y ago
"Heavier-than-air flying machines are impossible." -- Lord William Thomson Kelvin, British mathematician and physicist, president of the British Royal Society, 1895. Edit: See https://news.ycombinator.com/item?id=27816225 https://news.ycombinator.com/item?id=27816225 for a discussion of the paper that launched this whole topic. Edit 2: The actual paper you want is this one by the author of OP, the first one is referring back to this: https://arxiv.org/abs/2006.07125 https://arxiv.org/abs/2006.07125
- stevebmark 5y ago
  "Inertia is a property of matter" - fundamental unchangeable property of the universe
  - lolsal 5y ago
    ...so far.
- heavenlyblue 5y ago
  What about perpetual motion machines though? :)
- BurningFrog 5y ago
  Scientifically speaking, the fact that someone was wrong in the past, doesn't mean someone else is wrong now, even if they use a similar sentence structure. PS Yes, I am fun at parties, if I ever get invited to one again!
  - xupybd 5y ago
    You're technically correct but missing the point. Past hubris is a warning that we are capable of similar hubris. What we can say is our current model of the universe does not allow for any practical travel beyond the speed of light.
    - cirrus3 5y ago
      Valid warnings also don't mean anything.
    - deleted 5y ago
      [deleted]
    - krapp 5y ago
      We can also say that our current model of the universe is orders of magnitude more accurate, so it's more likely that we're correct about the speed of light - something which has been experimentally tested and verified by hundreds if not thousands of people - than the opinion of one particular Lord Kelvin regarding the viability of aircraft. It's just as hubristic to assume that science is as ignorant now as it always has been.
      - xupybd 5y ago
        Yes but we do have theories that suggest getting from point A to point B faster than light could be possible. We just have to do some things that appear impractical such as bend spacetime.
        bashinator 5y ago
        If FTL were possible, don’t you think there’d already be evidence of the time travel? First thing I’d do with FTL is travel back to the earliest habitable epoch in the Universe and start building galaxy-sized Dyson spheres.
        xupybd 5y ago
- klyrs 5y ago
  Which ignored the obvious and prevalent heavier-than-air flying birds. We have no such examples to point at with FTL travel.
Datenstrom 5y ago
I am not familiar with this field but extraordinary claims require extraordinary evidence and I am not aware of any evidence absolutely ruling out the possibility. From my understanding we are still unsure about very fundamental aspects of physics and the universe so there are certainly unknown unknowns left which could dramatically change our understanding of everything.
- munchler 5y ago
  > extraordinary claims require extraordinary evidence I think you've got the sign on your skepticism reversed. The burden of proof is very much on those who claim that FTL travel is possible. From Wikipedia: The special theory of relativity implies that only particles with zero rest mass (i.e., photons) may travel at the speed of light, and that nothing may travel faster. As of the 21st century, according to current scientific theories, matter is required to travel at slower-than-light (also STL or subluminal) speed with respect to the locally distorted spacetime region. Apparent FTL is not excluded by general relativity; however, any apparent FTL physical plausibility is currently speculative. See https://en.wikipedia.org/wiki/Faster-than-light https://en.wikipedia.org/wiki/Faster-than-light
  - sgjohnson 5y ago
    I don’t think that anyone made the claim that FTL travel is possible; they merely said that there’s still so much we don’t know about the universe, so definitely ruling something out is a bit rash. With our current understanding of the universe, yes, indeed, FTL travel is not possible. But it’s naïve to think that our understanding of universe won’t change.
  - sokoloff 5y ago
    The burden of proof for people making that claim is on the person making that claim. The burden of proof for making the claim that it’s “fundamentally impossible” is likewise on the person making that claim. For all we know, our understanding of the universe could be at a stage of analogous to “there are four elements: earth, air, fire, and water”. Many things that we enjoy daily were once “fundamentally impossible”.
madaxe_again 5y ago
Plenty of current physics allows for the possibility - even special relativity allows for it. Personally, I think that the “speed of light” is a misleading misnomer. It’s the speed of information propagation in flat space - and even that’s a misnomer, as speed is a very human concept, as is time, as is space. For all we know we’re waddling around in flatland, thinking that what we perceive is what is. More likely than not, most everything we know isn’t even wrong. To borrow Haldane - “Nature is not only queerer than we suppose, it is queerer than we can suppose.”
teaearlgraycold 5y ago
Not sure if it matters too much from an individualistic perspective. Near light-speed travel will allow a person to go anywhere instantaneously, they'd just have to contend with leaving the time and space they know behind them.
- amelius 5y ago
  > Near light-speed travel will allow a person to go anywhere instantaneously Only if you ignore the enormous acceleration/deceleration forces needed for this.
  - cedricd 5y ago
    Surprisingly it's not that much. At a constant 1G acceleration you could travel across the galaxy (100k light years) in 12 years (from your reference frame)[0]. I definitely agree that such travel would require enormous amounts of energy. [0]: https://en.wikipedia.org/wiki/Space_travel_under_constant_acceleration https://en.wikipedia.org/wiki/Space_travel_under_constant_ac...
  - sgjohnson 5y ago
    also, "instantaneously" is a stretch on a galactic scale. 299792000 m/s isn't as fast as it sounds if you need to cross the entire galaxy. Time dilation doesn't matter here.
- mulmen 5y ago
  Only for sufficiently small values of anywhere. Even near-light-speed communication in fiber optics has detectable and significant delay just in crossing a continent. A trip made physically by humans every day. Near-light-speed travel to the Moon would take a few seconds. Near-light-speed travel to Mars would take longer than my drive to the grocery store. These are not "instantaneously."
  - krapp 5y ago
    OK. Only Pluto in a few hours, Mars in a few minutes, and the moon in less time it would take for me to reach the toilet from my living room. Not literally instantaneous, but still practically instantaneous at the scale of the solar system.
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yumraj 5y ago
> Faster than light travel and time travel are both fundamentally impossible in our universe and can't be achieved. That may very well be, and true in our lifetime, but given how little we know about a lot of things, and that in many cases we don't even know what we don't know, I would hesitate in making an absolute statement.
- deleted 5y ago
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- willis936 5y ago
  It's been proven rather thoroughly though. Look at Kip Thorne's body of work. His book: Black Holes and Time Warps is accessible. c0 is the speed of light only incidentally. It is the speed of causality first. You can warp spacetime but you can't change the speed limit. You might think there would be a hypothetical way to cheat it from some unknown phenomenon, but then any occurrence of that phenomenon would destroy itself in zero time.
senectus1 5y ago
Doesn't the concept of Wormholes, folding space or Warp engines bypass FTL blocks? You're essentially relocating from one location to another by bypassing the distance... Leaving this universe long enough to travel a comparatively smaller distance/time in another then pop back into our universe a long long way but short amount of local time later. Sure you dont travel FTL but you do arrive in the location Faster than light would take to travel in mundane space.
- mannerheim 5y ago
  I believe all of those violate causality, at least if you have more than one of them (more than one pair in the case of wormholes).
  - senectus1 5y ago
    Causality might very well be locked to this universe/space. I mean its all just sci-fi at the moment. But lots of things we take advantage of today was at one time in the past as well. I prefer to be optimistic about potential breakthroughs.
kingcharles 5y ago
Well, technically time travel forward is easy. And to say that backwards time travel isn't possible at this point doesn't make much sense. We don't even have a clear understanding of what time is, or why it goes forwards. And the singularity should be around the corner, and that might present a computerized solution to emulate reverse time travel.

ctoth 5y ago

"Heavier-than-air flying machines are impossible." -- Lord William Thomson Kelvin, British mathematician and physicist, president of the British Royal Society, 1895. Edit: See https://news.ycombinator.com/item?id=27816225 https://news.ycombinator.com/item?id=27816225 for a discussion of the paper that launched this whole topic. Edit 2: The actual paper you want is this one by the author of OP, the first one is referring back to this: https://arxiv.org/abs/2006.07125 https://arxiv.org/abs/2006.07125

stevebmark 5y ago
"Inertia is a property of matter" - fundamental unchangeable property of the universe
- lolsal 5y ago
  ...so far.
heavenlyblue 5y ago
What about perpetual motion machines though? :)
BurningFrog 5y ago
Scientifically speaking, the fact that someone was wrong in the past, doesn't mean someone else is wrong now, even if they use a similar sentence structure. PS Yes, I am fun at parties, if I ever get invited to one again!
- xupybd 5y ago
  You're technically correct but missing the point. Past hubris is a warning that we are capable of similar hubris. What we can say is our current model of the universe does not allow for any practical travel beyond the speed of light.
  - cirrus3 5y ago
    Valid warnings also don't mean anything.
  - deleted 5y ago
    [deleted]
  - krapp 5y ago
    We can also say that our current model of the universe is orders of magnitude more accurate, so it's more likely that we're correct about the speed of light - something which has been experimentally tested and verified by hundreds if not thousands of people - than the opinion of one particular Lord Kelvin regarding the viability of aircraft. It's just as hubristic to assume that science is as ignorant now as it always has been.
    - xupybd 5y ago
      Yes but we do have theories that suggest getting from point A to point B faster than light could be possible. We just have to do some things that appear impractical such as bend spacetime.
      - bashinator 5y ago
        If FTL were possible, don’t you think there’d already be evidence of the time travel? First thing I’d do with FTL is travel back to the earliest habitable epoch in the Universe and start building galaxy-sized Dyson spheres.
        xupybd 5y ago
klyrs 5y ago
Which ignored the obvious and prevalent heavier-than-air flying birds. We have no such examples to point at with FTL travel.

Datenstrom 5y ago

I am not familiar with this field but extraordinary claims require extraordinary evidence and I am not aware of any evidence absolutely ruling out the possibility. From my understanding we are still unsure about very fundamental aspects of physics and the universe so there are certainly unknown unknowns left which could dramatically change our understanding of everything.

munchler 5y ago
> extraordinary claims require extraordinary evidence I think you've got the sign on your skepticism reversed. The burden of proof is very much on those who claim that FTL travel is possible. From Wikipedia: The special theory of relativity implies that only particles with zero rest mass (i.e., photons) may travel at the speed of light, and that nothing may travel faster. As of the 21st century, according to current scientific theories, matter is required to travel at slower-than-light (also STL or subluminal) speed with respect to the locally distorted spacetime region. Apparent FTL is not excluded by general relativity; however, any apparent FTL physical plausibility is currently speculative. See https://en.wikipedia.org/wiki/Faster-than-light https://en.wikipedia.org/wiki/Faster-than-light
- sgjohnson 5y ago
  I don’t think that anyone made the claim that FTL travel is possible; they merely said that there’s still so much we don’t know about the universe, so definitely ruling something out is a bit rash. With our current understanding of the universe, yes, indeed, FTL travel is not possible. But it’s naïve to think that our understanding of universe won’t change.
- sokoloff 5y ago
  The burden of proof for people making that claim is on the person making that claim. The burden of proof for making the claim that it’s “fundamentally impossible” is likewise on the person making that claim. For all we know, our understanding of the universe could be at a stage of analogous to “there are four elements: earth, air, fire, and water”. Many things that we enjoy daily were once “fundamentally impossible”.

madaxe_again 5y ago

Plenty of current physics allows for the possibility - even special relativity allows for it. Personally, I think that the “speed of light” is a misleading misnomer. It’s the speed of information propagation in flat space - and even that’s a misnomer, as speed is a very human concept, as is time, as is space. For all we know we’re waddling around in flatland, thinking that what we perceive is what is. More likely than not, most everything we know isn’t even wrong. To borrow Haldane - “Nature is not only queerer than we suppose, it is queerer than we can suppose.”

teaearlgraycold 5y ago

Not sure if it matters too much from an individualistic perspective. Near light-speed travel will allow a person to go anywhere instantaneously, they'd just have to contend with leaving the time and space they know behind them.

amelius 5y ago
> Near light-speed travel will allow a person to go anywhere instantaneously Only if you ignore the enormous acceleration/deceleration forces needed for this.
- cedricd 5y ago
  Surprisingly it's not that much. At a constant 1G acceleration you could travel across the galaxy (100k light years) in 12 years (from your reference frame)[0]. I definitely agree that such travel would require enormous amounts of energy. [0]: https://en.wikipedia.org/wiki/Space_travel_under_constant_acceleration https://en.wikipedia.org/wiki/Space_travel_under_constant_ac...
- sgjohnson 5y ago
  also, "instantaneously" is a stretch on a galactic scale. 299792000 m/s isn't as fast as it sounds if you need to cross the entire galaxy. Time dilation doesn't matter here.
mulmen 5y ago
Only for sufficiently small values of anywhere. Even near-light-speed communication in fiber optics has detectable and significant delay just in crossing a continent. A trip made physically by humans every day. Near-light-speed travel to the Moon would take a few seconds. Near-light-speed travel to Mars would take longer than my drive to the grocery store. These are not "instantaneously."
- krapp 5y ago
  OK. Only Pluto in a few hours, Mars in a few minutes, and the moon in less time it would take for me to reach the toilet from my living room. Not literally instantaneous, but still practically instantaneous at the scale of the solar system.

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yumraj 5y ago

> Faster than light travel and time travel are both fundamentally impossible in our universe and can't be achieved. That may very well be, and true in our lifetime, but given how little we know about a lot of things, and that in many cases we don't even know what we don't know, I would hesitate in making an absolute statement.

deleted 5y ago
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willis936 5y ago
It's been proven rather thoroughly though. Look at Kip Thorne's body of work. His book: Black Holes and Time Warps is accessible. c0 is the speed of light only incidentally. It is the speed of causality first. You can warp spacetime but you can't change the speed limit. You might think there would be a hypothetical way to cheat it from some unknown phenomenon, but then any occurrence of that phenomenon would destroy itself in zero time.

senectus1 5y ago

Doesn't the concept of Wormholes, folding space or Warp engines bypass FTL blocks? You're essentially relocating from one location to another by bypassing the distance... Leaving this universe long enough to travel a comparatively smaller distance/time in another then pop back into our universe a long long way but short amount of local time later. Sure you dont travel FTL but you do arrive in the location Faster than light would take to travel in mundane space.

mannerheim 5y ago
I believe all of those violate causality, at least if you have more than one of them (more than one pair in the case of wormholes).
- senectus1 5y ago
  Causality might very well be locked to this universe/space. I mean its all just sci-fi at the moment. But lots of things we take advantage of today was at one time in the past as well. I prefer to be optimistic about potential breakthroughs.

kingcharles 5y ago

Well, technically time travel forward is easy. And to say that backwards time travel isn't possible at this point doesn't make much sense. We don't even have a clear understanding of what time is, or why it goes forwards. And the singularity should be around the corner, and that might present a computerized solution to emulate reverse time travel.