171–180 of 234 posts
Earlier quoted context omitted.
Also, it doesn’t take too much acceleration to make that trip. Comfortable earthlike 1g (~ 10m/s/s) is enough to build up a decent speed in a very reasonable time. Energy is the issue though.
You need to spend equal amounts of energy and time on both acceleration and deceleration. It doesn’t help to go fast if you can’t stop at where you are going.
Earlier quoted context omitted.
Also, it doesn’t take too much acceleration to make that trip. Comfortable earthlike 1g (~ 10m/s/s) is enough to build up a decent speed in a very reasonable time. Energy is the issue though.
It's a fantasy as long as you are still living under the tyranny of the rocket equation.
I think a lot of people assume that this means you couldn't go more than a few (~100) light-years in your lifetime... But this is not actually correct. Counter-intuitively you can theorically go any number of light-years (essentially) in your lifetime, as long as you are able to approach the speed of light because when you do so the distance is dilated and hence you're covering far more ground within your reference f…
You can even do so without going near the speed of light if you build a very massive ship and utilize time dilation of gravity. Arvin Ash has a cool video on this that is probably too complicated to describe in a HN comment: https://www.youtube.com/watch?v=PA66ah9b0U4
Earlier quoted context omitted.
If distances are dilating, why isn't that /less/ ground?
The distance doesn't dilate; time does. The distance contracts . E.g., to a photon moving at 1c, the whole universe has a contracted length of 0 meters, and it crosses the whole universe instantly. To us, observers at and the photon takes to cross the whole universe. By the time the photon's 0-second journey across the entire universe has finished (whatever that means), we're all extremely old. :D This is the time di…
Since the universe expands with >1c, I wonder if the photon actually crosses the whole universe. And if not, how it would look like from the prespective of the photon?
Earlier quoted context omitted.
Also, it doesn’t take too much acceleration to make that trip. Comfortable earthlike 1g (~ 10m/s/s) is enough to build up a decent speed in a very reasonable time. Energy is the issue though.
Yep. At 1g you could literally go to the edge of the visible universe in less than 50 years (assuming you are targeting the edge as defined at time of departure).
The simplest way I could ever wrap my head around this, is to understand that everything travels through spacetime at the same speed. There is no travelling faster or slower, just crossing the graph at a different angle.
Can a thing with no mass ever go less than the speed of light? Does it have a concept of time?
Sure, light is slowed down when it travels through different substances. That's why we have refraction.
I think a lot of people assume that this means you couldn't go more than a few (~100) light-years in your lifetime... But this is not actually correct. Counter-intuitively you can theorically go any number of light-years (essentially) in your lifetime, as long as you are able to approach the speed of light because when you do so the distance is dilated and hence you're covering far more ground within your reference f…
My favorite general relativity paradox: A runner is running with a 20m pole at a sufficient velocity so that a stationary observer sees the pole having length 10m. The runner runs through a barn which is 10m long. And two people outside shut the doors simultaneously so that the runner is completely enclosed in the barn for a moment. But from the runner's perspective, the barn has length 5m long. What does she see hap…