3 ms·

It might be easier to think about this as “if you are on the moon and point a telescope at a clock on earth, clock hands move slower on earth than on the moon."

It might be easier to think about this as “if you are on the moon and point a telescope at a clock on earth, clock hands move slower on earth than on the moon." This is distinct from "all humans everywhere have a normative experience that the clock hands right next to them move at the same speed.” Or "you never experience falling into a black hole, but you do fall in." You can also watch the movie Interstellar, it has clock hands moving slower in gravity wells as a minor plot point.

alganet 2y ago
You mean the descent into the water planet? If I modify that scene a little bit, it serves to showcase my doubts. 4 astronauts are on orbit around the water planet, but Brand is sick. Cooper, Brand and Doyle go down so Romily can spend 20 years researching a cure. After an hour, Cooper, the sick Brand and Doyle go back to orbit and reunite with Romily. For Romily, 20 years passed and he completed the sythesis for the cure. Romily has "stolen" some information about the future by "walking it" in a relatively different pace, and it was able to share that information with someone that "walked it" in a slower pace. Now, this is for gravity. This was possible because of Gargantua. But gravity is not the only component of the "microseconds per day" formula, there's seems to be more. So I'm interested perhaps in an illustrative scenario where the speed is highlighted (whatever the outcome is, doesn't matter), not the gravity, and there is an attempt at information exchange (don't care if can be successful or not, as long as the example actually explains it).
- pdonis 2y ago
  > I'm interested perhaps in an illustrative scenario where the speed is highlighted That would be something like the standard twin paradox. You could set that up so that, for example, Cooper, Brand, and Doyle go out in their spaceship at very high speed and don't come back until 20 years have passed on Earth, where Romily has spent that time finding a cure. With the right numbers for the speed of the spaceship and the distance it travels out and back, it could be arranged that only an hour would pass for those aboard the ship. The downside of this is that the rocket power you would need to boost the ship to the required speed, and then turn it around and come back and decelerate to land on Earth again, would be huge, way, way beyond what would normally be considered reasonable. The reason a supermassive black hole was used instead in Interstellar was to allow Cooper, Brand, and Doyle to be able to travel at much more reasonable speeds using much more reasonable rockets, and take advantage of the spacetime geometry of the hole to get the extreme time dilation effect. The reason a rapidly rotating hole was used (aside from the fact that we believe most supermassive holes in our universe are rapidly rotating in this way) was that it allows free-fall orbits to exist very close to the hole's horizon that have very large time dilation factors like 1 hour to 20 years, so that a planet in a free-fall orbit could plausibly exist in that region. For a non-rotating hole that is not possible; to get that close to the horizon and get the time dilation factor you would need, you would have to use rockets to "hover" and the rocket power involved would be of the same order of unreasonableness, if not more so, as what would be needed for the "twin paradox" trip I described above.

alganet 2y ago

You mean the descent into the water planet? If I modify that scene a little bit, it serves to showcase my doubts. 4 astronauts are on orbit around the water planet, but Brand is sick. Cooper, Brand and Doyle go down so Romily can spend 20 years researching a cure. After an hour, Cooper, the sick Brand and Doyle go back to orbit and reunite with Romily. For Romily, 20 years passed and he completed the sythesis for the cure. Romily has "stolen" some information about the future by "walking it" in a relatively different pace, and it was able to share that information with someone that "walked it" in a slower pace. Now, this is for gravity. This was possible because of Gargantua. But gravity is not the only component of the "microseconds per day" formula, there's seems to be more. So I'm interested perhaps in an illustrative scenario where the speed is highlighted (whatever the outcome is, doesn't matter), not the gravity, and there is an attempt at information exchange (don't care if can be successful or not, as long as the example actually explains it).

pdonis 2y ago
> I'm interested perhaps in an illustrative scenario where the speed is highlighted That would be something like the standard twin paradox. You could set that up so that, for example, Cooper, Brand, and Doyle go out in their spaceship at very high speed and don't come back until 20 years have passed on Earth, where Romily has spent that time finding a cure. With the right numbers for the speed of the spaceship and the distance it travels out and back, it could be arranged that only an hour would pass for those aboard the ship. The downside of this is that the rocket power you would need to boost the ship to the required speed, and then turn it around and come back and decelerate to land on Earth again, would be huge, way, way beyond what would normally be considered reasonable. The reason a supermassive black hole was used instead in Interstellar was to allow Cooper, Brand, and Doyle to be able to travel at much more reasonable speeds using much more reasonable rockets, and take advantage of the spacetime geometry of the hole to get the extreme time dilation effect. The reason a rapidly rotating hole was used (aside from the fact that we believe most supermassive holes in our universe are rapidly rotating in this way) was that it allows free-fall orbits to exist very close to the hole's horizon that have very large time dilation factors like 1 hour to 20 years, so that a planet in a free-fall orbit could plausibly exist in that region. For a non-rotating hole that is not possible; to get that close to the horizon and get the time dilation factor you would need, you would have to use rockets to "hover" and the rocket power involved would be of the same order of unreasonableness, if not more so, as what would be needed for the "twin paradox" trip I described above.