7 ms·

So that's it, then? Some thing, say, a million light years away from another thing is in practice entirely inaccessible to civilizations existing on that other

by piker 8y ago

So that's it, then? Some thing, say, a million light years away from another thing is in practice entirely inaccessible to civilizations existing on that other thing, requiring a minimum of a million years to reach?

BartBoch 8y ago
As always, soon we will discover another way, or there will be a different theory that will allow bending the rules.
- lupire 8y ago
  Not always. Faster than light travel has never been bent.
  - BartBoch 8y ago
    Well, we are able to research FTL for only a few decades. Give it a few more due to complexity. Few ages ago people thought that the world is flat... Also, there are theories of FTL: https://en.wikipedia.org/wiki/Faster-than-light https://en.wikipedia.org/wiki/Faster-than-light
    - smoyer 8y ago
      And suddenly people think the earth is flat again ... we need to keep science more relatable to the general population and that starts with being realistic. I'm not arguing with your idea ... just that it should start with a caveat ... "there are no current theories that support FTL but we're hoping ..."
    - psionides 8y ago
      They didn't really, that's a common misconception: https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth
    - earenndil 8y ago
      > Few ages ago people thought that the world is flat... Ah, no they didn't. Scientific consensus has been the earth is round for thousands of years.
      - craftinator 8y ago
        As the word 'age' is used in the original comment, a likely synonym is 'millenia', so you are in aggreement with the poster.
  - jcoffland 8y ago
    Shadows can move faster than light.
    - saagarjha 8y ago
      Shadows are an abstract concept (namely, the absence of light), not a physical thing.
      - smoyer 8y ago
        I would argue that shadows are a very physical effect.
    - TotempaaltJ 8y ago
      That's an interesting assertion... Why would shadows be able to move faster than light?
      - virgilp 8y ago
        It's perfectly correct and does not contradict physics. Think about it in the opposite direction - say you have a perfect laser, with perfect pointing ability. You pick two planets that are far away from each other but at roughly the same distance from Earth, and make an angle of 10 degrees with it; it will take you a few seconds to "move" the laser 10 degrees and thus move the spot from one planet to the other - in the process making the spot "travel" millions of light years in a few seconds. However, the light itself has not traveled at faster-than-light speeds (it still takes a lot of years for the light from your laser pointer to reach any one of those two planets).
        jdmichal 8y ago
        There's two possible interpretations here. The implication of "shadows travel faster than light" is that information about the lack of light is faster. This interpretation is false. In your thought experiment, the information of the lasers moving still only travels at speed of light, even if the actual movement took only a fraction of that time. So the "shadow" on Earth reacts at the speed of light to changes in the source. However, if the idea is that a laser that is continuously lit can "sweep" a path, such that the laser dot appears to move faster than light could travel that same path... Then of course that's trivially true. The light is traveling the radius of the arc, not the length.
maxerickson 8y ago
According to physics as we currently understand it, yes.
swebs 8y ago
On the bright side, due to time dilation, you can still make the trip in your lifetime.
- zspade 8y ago
  If by the bright side you mean you would only make it there it there as pure energy. Mass is converted to energy as it approaches C (Light Speed). Though getting mass to actual light speed would require infinite energy, so that point is moot. Let's say you get to 96% C. You would experience 28% of the journey. Taking into account the the time to speed up and slow down from C, you're looking at over 290k years from the perspective of the passengers. At 99% C, you would experience over 14% of the journey (About 142k years).
  - saagarjha 8y ago
    > Mass is converted to energy as it approaches C (Light Speed). Uh, I think it's the other way around: the energy you pump in becomes additional mass.
    - stcredzero 8y ago
      Look at my sibling comment to yours. Relativistic mass is mostly just a pedagogical fiction.
  - stcredzero 8y ago
    Mass is converted to energy as it approaches C (Light Speed). Not so much. https://www.youtube.com/watch?v=LTJauaefTZM https://www.youtube.com/watch?v=LTJauaefTZM Try this thought experiment. Let's say you had a magic Bussard Ramjet rocket which scoops up energy and reaction mass from space and can accelerate forever. There are no special reference frames. So what happens if the rocket accelerates then shuts off its engine at the point where the "relativistic mass," as measured by an un-accelerated observer, should make the rocket disappear behind an event horizon? From the POV of people on the rocket, they accelerated, then stopped accelerating. From the observer's POV, the rocket turned into a black hole? One reference frame now seems "privileged" or different somehow. How do we square this with relativity? Also, what happens if the rocket turns around, then decelerates? Wouldn't that constitute them returning from inside of an event horizon? The answer, is that "relativistic mass" is actually just a pedagogical fiction. (EDIT: Also, a lot of the redonkulousness in the thought experiment sneakily comes from rockets that can magically accelerate without worrying about where the fuel and energy come from. If you worked out how much fuel and reaction mass would be needed by a real rocket to perform such a feat, you'd get "unphysical" amounts of matter.)
nkrisc 8y ago
Well, theoretically they could load their civilization up on a giant ship and move their civilization there over the course of a million years. Likelihood of success? Probably not great, but possible.
- xvector 8y ago
  Everyone is missing the obvious solution. If we're talking about tech this fantastical, the best idea is to ditch our ephemeral biological bodies, jump onto a synthetic medium, and call it a day. Hit pause so the journey takes a fraction of a second, or spend 1000Y in a VR - do whatever you want. I don't see a future where we're this advanced yet still content with our frighteningly fragile bodies.
  - nkrisc 8y ago
    Perhaps it's because building a giant ship that can carry countless generations of inhabitants many light years is really more of just an engineering problem. All the challenges (of which there are plenty) all have reasonably known solutions. There's not really all that much novel technology required. Just better tech than we have, and a lot of it, to be sure. Uploading a consciousness into a computer and have it remain "you"? That's completely foreign to what we know today. I'm not saying it's categorically impossible; to your point, if a civilization has advanced to the point where the above is ship is feasible, surely they must have picked this up along the way? Maybe, but maybe not. We don't even know if it is possible. But keep a shitload of people alive in space for a long time? Sounds plausible, even if it is enormously difficult.
    - p1esk 8y ago
      Or we can relax the requirement that “it remains you”, and be content with the idea of cloning the mind. This should be somewhat easier to achieve.
      - throwawaymath 8y ago
        If you are okay with that, you no longer need to upload anything, and your problem becomes one of imitation rather than continuity. You can dispense with the philosophical question of identity entirely and obviate away the problem of interfacing with a mind. Find a way to decompose an individual's personality into progressively more granular dimensions of behavior. Model stimulus -> response reactions as transformations. Sample enough responses from each type of behavior, make linear approximations of the transformations until you achieve a 1:1 simulacra, and derive a basis for the response basis. Your human mind will be a matrix representation of the map between the stimulus and response spaces. As unrealistic as all of that sounds, it still sounds significantly easier to me than uploading (or even interfacing with) a mind.
nine_k 8y ago
This depends on what do you mean by 'inaccessible'. Going there and back again, and telling your pals how things are 1000LY away is likely impossible. Expanding your civilization to more and more habitable celestial bodies, slowly but relatively surely, is entirely possible. This is how e.g. plants colonize vast spaces, being limited by the speed of their growth often by inches per lifetime. (You should also consider the amount of resources the plats dedicate to it, and their success rate.)
- therein 8y ago
  But aren't there massive gaps where an intermediate celestial body to perform this jump on will be simply too far away for traditional space travel?
  - jessriedel 8y ago
    Probably not. On the timescales of millions of years, the only thing that really matter is whether it's physically possible, and it looks physically possible to colonize other galaxies. http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spr... I'd be pretty surprised if the jump between galactic groups is much worse.
- harimau777 8y ago
  I get what you are saying, but it seems like the plant approach is mostly useless to humans. If the people on opposite sides of a galactic civilization are so far away that they cannot meaningfully interact, then it seems like that's no different than the other person not existing from their perspective.
  - parksy 8y ago
    Depends on the definition of useless or meaningful. If meaningfulness only extends to immediate political, social, economic or technological interactions then maybe an organic colonisation seems useless, I guess. Unlike plants, through the power of electromagnetic communications and a culture based on shared knowledge, humans will know the others exist, even though that interaction will be slow with likely little-to-no-influence on their local evolution. There would be huge cultural meaning even despite the lack of immediacy. Imagine living in a world where you know that there are other humans like you in space, living on other worlds light-years away. You might not be able to communicate immediately, but you know that they are there, and the universe is not so empty to you. You could look to the night sky and reminisce on your great(*n) grandpronoun whose progeny have built a thriving colony among the stars. Entire institutes would exist dedicated to collating and outlining the historical expansion of mankind among the stars, even if that knowledge takes centuries or millennia to accrue. Also we can not say those other humans may as well not exist, because there is no telling what each new colony will go on to achieve. Their cultural, scientific and philosophical development independent of the influence of Earth's history and challenged by new environments could yield new perspectives, ways of thinking and practical inventions whose value far outweighs the large delay in communications. If we're talking galactic scale, then the creatures who ultimately wind up on the other side of the Milky Way two hundred thousand years from now would likely bear only a passing resemblance to the humans who expanded from Earth. However barring a catastrophic event that erases their knowledge of their history, they would owe their existence in their history books to this tiny planet. Finally, the fear that we are the only planet with human life would be vanquished, so even if we all died from pollution or meteorite, we'd know that somewhere the legacy of our species (and selected companion lifeforms) would continue, which I don't think is useless or meaningless either.
airstrike 8y ago
You're correct, at least according to Kurzgesagt https://www.youtube.com/watch?v=ZL4yYHdDSWs https://www.youtube.com/watch?v=ZL4yYHdDSWs
krapp 8y ago
>So that's it, then? Some thing, say, a million light years away from another thing is in practice entirely inaccessible to civilizations existing on that other thing, requiring a minimum of a million years to reach? "We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far." -- H.P. Lovecraft, 'Call of Cthulhu' We're just a random species of ape too smart for its own good, only here to ponder the universe at all because an asteroid happened to wipe out the dinosaurs 65 million years ago. The universe doesn't owe us anything. At least we have telescopes and science fiction, though. The dinosaurs didn't have either.

by piker 8y ago

BartBoch 8y ago

As always, soon we will discover another way, or there will be a different theory that will allow bending the rules.

lupire 8y ago
Not always. Faster than light travel has never been bent.
- BartBoch 8y ago
  Well, we are able to research FTL for only a few decades. Give it a few more due to complexity. Few ages ago people thought that the world is flat... Also, there are theories of FTL: https://en.wikipedia.org/wiki/Faster-than-light https://en.wikipedia.org/wiki/Faster-than-light
  - smoyer 8y ago
    And suddenly people think the earth is flat again ... we need to keep science more relatable to the general population and that starts with being realistic. I'm not arguing with your idea ... just that it should start with a caveat ... "there are no current theories that support FTL but we're hoping ..."
  - psionides 8y ago
    They didn't really, that's a common misconception: https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth https://en.wikipedia.org/wiki/Myth_of_the_flat_Earth
  - earenndil 8y ago
    > Few ages ago people thought that the world is flat... Ah, no they didn't. Scientific consensus has been the earth is round for thousands of years.
    - craftinator 8y ago
      As the word 'age' is used in the original comment, a likely synonym is 'millenia', so you are in aggreement with the poster.
- jcoffland 8y ago
  Shadows can move faster than light.
  - saagarjha 8y ago
    Shadows are an abstract concept (namely, the absence of light), not a physical thing.
    - smoyer 8y ago
      I would argue that shadows are a very physical effect.
  - TotempaaltJ 8y ago
    That's an interesting assertion... Why would shadows be able to move faster than light?
    - virgilp 8y ago
      It's perfectly correct and does not contradict physics. Think about it in the opposite direction - say you have a perfect laser, with perfect pointing ability. You pick two planets that are far away from each other but at roughly the same distance from Earth, and make an angle of 10 degrees with it; it will take you a few seconds to "move" the laser 10 degrees and thus move the spot from one planet to the other - in the process making the spot "travel" millions of light years in a few seconds. However, the light itself has not traveled at faster-than-light speeds (it still takes a lot of years for the light from your laser pointer to reach any one of those two planets).
      - jdmichal 8y ago
        There's two possible interpretations here. The implication of "shadows travel faster than light" is that information about the lack of light is faster. This interpretation is false. In your thought experiment, the information of the lasers moving still only travels at speed of light, even if the actual movement took only a fraction of that time. So the "shadow" on Earth reacts at the speed of light to changes in the source. However, if the idea is that a laser that is continuously lit can "sweep" a path, such that the laser dot appears to move faster than light could travel that same path... Then of course that's trivially true. The light is traveling the radius of the arc, not the length.

maxerickson 8y ago

According to physics as we currently understand it, yes.

swebs 8y ago

On the bright side, due to time dilation, you can still make the trip in your lifetime.

zspade 8y ago
If by the bright side you mean you would only make it there it there as pure energy. Mass is converted to energy as it approaches C (Light Speed). Though getting mass to actual light speed would require infinite energy, so that point is moot. Let's say you get to 96% C. You would experience 28% of the journey. Taking into account the the time to speed up and slow down from C, you're looking at over 290k years from the perspective of the passengers. At 99% C, you would experience over 14% of the journey (About 142k years).
- saagarjha 8y ago
  > Mass is converted to energy as it approaches C (Light Speed). Uh, I think it's the other way around: the energy you pump in becomes additional mass.
  - stcredzero 8y ago
    Look at my sibling comment to yours. Relativistic mass is mostly just a pedagogical fiction.
- stcredzero 8y ago
  Mass is converted to energy as it approaches C (Light Speed). Not so much. https://www.youtube.com/watch?v=LTJauaefTZM https://www.youtube.com/watch?v=LTJauaefTZM Try this thought experiment. Let's say you had a magic Bussard Ramjet rocket which scoops up energy and reaction mass from space and can accelerate forever. There are no special reference frames. So what happens if the rocket accelerates then shuts off its engine at the point where the "relativistic mass," as measured by an un-accelerated observer, should make the rocket disappear behind an event horizon? From the POV of people on the rocket, they accelerated, then stopped accelerating. From the observer's POV, the rocket turned into a black hole? One reference frame now seems "privileged" or different somehow. How do we square this with relativity? Also, what happens if the rocket turns around, then decelerates? Wouldn't that constitute them returning from inside of an event horizon? The answer, is that "relativistic mass" is actually just a pedagogical fiction. (EDIT: Also, a lot of the redonkulousness in the thought experiment sneakily comes from rockets that can magically accelerate without worrying about where the fuel and energy come from. If you worked out how much fuel and reaction mass would be needed by a real rocket to perform such a feat, you'd get "unphysical" amounts of matter.)

nkrisc 8y ago

Well, theoretically they could load their civilization up on a giant ship and move their civilization there over the course of a million years. Likelihood of success? Probably not great, but possible.

xvector 8y ago
Everyone is missing the obvious solution. If we're talking about tech this fantastical, the best idea is to ditch our ephemeral biological bodies, jump onto a synthetic medium, and call it a day. Hit pause so the journey takes a fraction of a second, or spend 1000Y in a VR - do whatever you want. I don't see a future where we're this advanced yet still content with our frighteningly fragile bodies.
- nkrisc 8y ago
  Perhaps it's because building a giant ship that can carry countless generations of inhabitants many light years is really more of just an engineering problem. All the challenges (of which there are plenty) all have reasonably known solutions. There's not really all that much novel technology required. Just better tech than we have, and a lot of it, to be sure. Uploading a consciousness into a computer and have it remain "you"? That's completely foreign to what we know today. I'm not saying it's categorically impossible; to your point, if a civilization has advanced to the point where the above is ship is feasible, surely they must have picked this up along the way? Maybe, but maybe not. We don't even know if it is possible. But keep a shitload of people alive in space for a long time? Sounds plausible, even if it is enormously difficult.
  - p1esk 8y ago
    Or we can relax the requirement that “it remains you”, and be content with the idea of cloning the mind. This should be somewhat easier to achieve.
    - throwawaymath 8y ago
      If you are okay with that, you no longer need to upload anything, and your problem becomes one of imitation rather than continuity. You can dispense with the philosophical question of identity entirely and obviate away the problem of interfacing with a mind. Find a way to decompose an individual's personality into progressively more granular dimensions of behavior. Model stimulus -> response reactions as transformations. Sample enough responses from each type of behavior, make linear approximations of the transformations until you achieve a 1:1 simulacra, and derive a basis for the response basis. Your human mind will be a matrix representation of the map between the stimulus and response spaces. As unrealistic as all of that sounds, it still sounds significantly easier to me than uploading (or even interfacing with) a mind.

nine_k 8y ago

This depends on what do you mean by 'inaccessible'. Going there and back again, and telling your pals how things are 1000LY away is likely impossible. Expanding your civilization to more and more habitable celestial bodies, slowly but relatively surely, is entirely possible. This is how e.g. plants colonize vast spaces, being limited by the speed of their growth often by inches per lifetime. (You should also consider the amount of resources the plats dedicate to it, and their success rate.)

therein 8y ago
But aren't there massive gaps where an intermediate celestial body to perform this jump on will be simply too far away for traditional space travel?
- jessriedel 8y ago
  Probably not. On the timescales of millions of years, the only thing that really matter is whether it's physically possible, and it looks physically possible to colonize other galaxies. http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spreading.pdf http://www.fhi.ox.ac.uk/wp-content/uploads/intergalactic-spr... I'd be pretty surprised if the jump between galactic groups is much worse.
harimau777 8y ago
I get what you are saying, but it seems like the plant approach is mostly useless to humans. If the people on opposite sides of a galactic civilization are so far away that they cannot meaningfully interact, then it seems like that's no different than the other person not existing from their perspective.
- parksy 8y ago
  Depends on the definition of useless or meaningful. If meaningfulness only extends to immediate political, social, economic or technological interactions then maybe an organic colonisation seems useless, I guess. Unlike plants, through the power of electromagnetic communications and a culture based on shared knowledge, humans will know the others exist, even though that interaction will be slow with likely little-to-no-influence on their local evolution. There would be huge cultural meaning even despite the lack of immediacy. Imagine living in a world where you know that there are other humans like you in space, living on other worlds light-years away. You might not be able to communicate immediately, but you know that they are there, and the universe is not so empty to you. You could look to the night sky and reminisce on your great(*n) grandpronoun whose progeny have built a thriving colony among the stars. Entire institutes would exist dedicated to collating and outlining the historical expansion of mankind among the stars, even if that knowledge takes centuries or millennia to accrue. Also we can not say those other humans may as well not exist, because there is no telling what each new colony will go on to achieve. Their cultural, scientific and philosophical development independent of the influence of Earth's history and challenged by new environments could yield new perspectives, ways of thinking and practical inventions whose value far outweighs the large delay in communications. If we're talking galactic scale, then the creatures who ultimately wind up on the other side of the Milky Way two hundred thousand years from now would likely bear only a passing resemblance to the humans who expanded from Earth. However barring a catastrophic event that erases their knowledge of their history, they would owe their existence in their history books to this tiny planet. Finally, the fear that we are the only planet with human life would be vanquished, so even if we all died from pollution or meteorite, we'd know that somewhere the legacy of our species (and selected companion lifeforms) would continue, which I don't think is useless or meaningless either.

airstrike 8y ago

You're correct, at least according to Kurzgesagt https://www.youtube.com/watch?v=ZL4yYHdDSWs https://www.youtube.com/watch?v=ZL4yYHdDSWs

krapp 8y ago

>So that's it, then? Some thing, say, a million light years away from another thing is in practice entirely inaccessible to civilizations existing on that other thing, requiring a minimum of a million years to reach? "We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far." -- H.P. Lovecraft, 'Call of Cthulhu' We're just a random species of ape too smart for its own good, only here to ponder the universe at all because an asteroid happened to wipe out the dinosaurs 65 million years ago. The universe doesn't owe us anything. At least we have telescopes and science fiction, though. The dinosaurs didn't have either.