3 ms·

It only becomes "more difficult" as measured by people not onboard the spaceship. For people onboard, time effectively speeds up for the rest of the universe, s

It only becomes "more difficult" as measured by people not onboard the spaceship. For people onboard, time effectively speeds up for the rest of the universe, so that there is no brick wall to your acceleration. Therefore, it's also possible to time travel into the future, but not into the past.

est31 7y ago
Not really, even if you have optimal rocket fuel, you still have huge fuel demands: http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/r...
hnews_account_1 7y ago
That is not how it works from what little I know. Neither the spaceship, nor the outside observers will EVER see it hit the speed of light. That is the only constant thing they agree on. All of relativity hinges on this point. The Lorentz transformation is based on the fact that the speed of light is constant for all observers whether they're "stationary" or moving at 0.999999999c . So even at very high fractions of light speed, you know for a fact that you haven't hit light speed because when you turn on your spaceship's lights, the photons will look like they're travelling away from you at the speed of light (due to the own time dilation and length contraction you experience). This is why when you're calculating the actual value of time dilation, it considers what fraction of speed of light you're traveling. Because if you were the traveler, time dilates and length contracts EXACTLY enough to make light appear to travel at 1c (regardless of your own speed).
- Retric 7y ago
  https://en.wikipedia.org/wiki/Lorentz_transformation https://en.wikipedia.org/wiki/Lorentz_transformation Time dilation is only 1/2 the story. The other half is distance measurements get distorted. People in the spaceship see the same maximum velocity of objects they pass aka c. However, if a huge measuring tape with say light year tick marks passing them they are going to measure it’s speed at say .99 c and the time between tick marks is X. Alternatively, at .999c they would get a new time period Y. However the difference between X and Y is not simply .999/.99 but rather a more complex relativistic adjustment. However, this is only important for people on the spaceship. For people staying home the it takes 3.5x the energy to hit .999c vs .99c yet it’s only shaving 1% off the observed travel time. Which is unlikely to be considered worth it by just about any civilization baring significant changes to the laws of physics.
  - hnews_account_1 7y ago
    > Time dilation is only 1/2 the story. The other half is distance measurements get distorted. Yes, that's why I mentioned length contraction. They're results of the same transformation I believe. So they're directly related. Same as mass and every other supposed "constant" in newtonian mechanics.

est31 7y ago

Not really, even if you have optimal rocket fuel, you still have huge fuel demands: http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/r...

hnews_account_1 7y ago

That is not how it works from what little I know. Neither the spaceship, nor the outside observers will EVER see it hit the speed of light. That is the only constant thing they agree on. All of relativity hinges on this point. The Lorentz transformation is based on the fact that the speed of light is constant for all observers whether they're "stationary" or moving at 0.999999999c . So even at very high fractions of light speed, you know for a fact that you haven't hit light speed because when you turn on your spaceship's lights, the photons will look like they're travelling away from you at the speed of light (due to the own time dilation and length contraction you experience). This is why when you're calculating the actual value of time dilation, it considers what fraction of speed of light you're traveling. Because if you were the traveler, time dilates and length contracts EXACTLY enough to make light appear to travel at 1c (regardless of your own speed).

Retric 7y ago
https://en.wikipedia.org/wiki/Lorentz_transformation https://en.wikipedia.org/wiki/Lorentz_transformation Time dilation is only 1/2 the story. The other half is distance measurements get distorted. People in the spaceship see the same maximum velocity of objects they pass aka c. However, if a huge measuring tape with say light year tick marks passing them they are going to measure it’s speed at say .99 c and the time between tick marks is X. Alternatively, at .999c they would get a new time period Y. However the difference between X and Y is not simply .999/.99 but rather a more complex relativistic adjustment. However, this is only important for people on the spaceship. For people staying home the it takes 3.5x the energy to hit .999c vs .99c yet it’s only shaving 1% off the observed travel time. Which is unlikely to be considered worth it by just about any civilization baring significant changes to the laws of physics.
- hnews_account_1 7y ago
  > Time dilation is only 1/2 the story. The other half is distance measurements get distorted. Yes, that's why I mentioned length contraction. They're results of the same transformation I believe. So they're directly related. Same as mass and every other supposed "constant" in newtonian mechanics.