6 replies to this topic

[ameldedic2]

Does anyone actually know how fast one would need to travel (if possible) to speed up time in space relative to earth?

[JohnDoe1234]

Well, you would want to "slow" time relative to earth (assuming the patients were in the space ship) and I'm not sure how to calculate the speed or energy required, but it is certainly much more energy-expensive than cyronics not to mention way beyond our capabilities... but hey... you wouldn't have to worry about ice crystals dehydrating your cells [tung]

[jaydfox]

In order to slow time to half the rate it's passing back on earth, one would need to achieve a speed of 86.6% of the speed of light, or about 173,000 km/s, or a little under 400 million MPH.

We're not going to have technology to accomplish that with a human-sized cargo any time soon, especially if the acceleration has to be kept low enough to avoid crushing a person. Even at five times earth's gravity, it would take several months to get up to that speed.

I suspect we'll be able to successfully revive cryonics patients before we'll propel a human being to any significant fraction of the speed of light, but it's hard to say for sure at this point.

[maestro949]

Major adjustments to gravitational forces would likely wreak havoc on our finely tuned biology. We would probably need to make some serious genetic alterations to survive.

[jaydfox]

Maestro, interestingly enough, what prometheus is talking about is gravitational potential, not the strength of the local gravitational field. For example, the strength of gravitational pull at the earth's surface is 9.8 m/s^2, or 1g. The escape velocity from earth's surface, with respect to earth's gravity, is 11.2 km/s. That's a measure of gravitational potential, roughly speaking.

If you could stand on a platform located high above the sun, as far as the earth is from the sun, with the sun below your feet, then the strength of the gravitational field would be about 0.006 m/s^2 (or about 0.6 cm/s^2), or about 0.0006g, yet the escape velocity would be about 42 km/s, nearly four times the gravitational potential we experience from earth's gravity.

As another example, if you lowered that platform to be just about 3 million km above the surface of the sun, you would experience about 1g, the strength of gravity at the earth's surface. Assuming you could shield yourself from the immense solar radiation, solar wind, and magnetic fields, etc., the gravity would be quite bearable. The gravitational potential would be much larger than on earth, however, with an escape velocity of about 267 m/s. So the strength would be the same, but the potential would be 25 times more. It's because the gravitational field is larger, so you're deeper in a gravity well.

Taken to larger extremes, you could find yourself in a gravitational field that has the strength of earth's gravity, quite hospitable to life, but a gravitational potential approaching an escape velocity of the speed of light (e.g., near the surface of a very, very, very large black hole). In such a case, time for you would slow to a crawl relative to the outside universe.

I don't foresee us every using gravity the "old fashioned" way to slow time. We're talking about black holes as massive as our galaxy and then some.

However, as prometheus alludes to, it may be possible in the future to bend the rules (as we currently understand them) in our favor, obviating the requirement for so much mass. For me, it's far too speculative to think of it as anything more than a mental exercise in mathematics.