Archive for The Hitch Hiker’s Guide to the Galaxy

What to do if you find yourself inside the horizon of a black hole

Posted in The Universe and Stuff with tags , , , on May 7, 2019 by telescoper

Consider how lucky you are that life has been good to you so far.

Alternatively, if life hasn’t been good to you so far – which, given your current circumstances seems more likely – consider how lucky you are that it won’t be bothering you much longer.

That was the advice given to Ford Prefect by The Hitchhikers Guide to the Galaxy when he looked up `What do if you find yourself in a crack in the ground underneath a giant boulder you can’t move with no hope of rescue’. It seems fairly general advice to me, though. If you want more specific advice on what to do if you find yourself inside the horizon of a black hole then you can find it in an interesting paper on the arXiv with the abstract:

In this methodological paper we consider two problems an astronaut faces with under the black hole horizon in the Schwarzschild metric. 1) How to maximize the survival proper time. 2) How to make a visible part of the outer Universe as large as possible before hitting the singularity. Our consideration essentially uses the concept of peculiar velocities based on the “river model”. Let an astronaut cross the horizon from the outside. We reproduce from the first principles the known result that point 1) requires that an astronaut turn off the engine near the horizon and follow the path with the momentum equal to zero. We also show that point 2) requires maximizing the peculiar velocity of the observer. Both goals 1) and 2) require, in general, different strategies inconsistent with each other that coincide at the horizon only. The concept of peculiar velocities introduced in a direct analogy with cosmology, and its application for the problems studied in the present paper can be used in advanced general relativity courses.

It is advertised as a `methodological paper’ and I don’t know if they are planning experimental studies of this problem. I imagine might be difficult to secure funding.

The Total Perspective Vortex

Posted in The Universe and Stuff with tags , , on October 30, 2012 by telescoper

Vortices are swirling around in my mind these days. Not only because of Hurricane Sandy, but also because I’ve got to prepare a couple of lectures about vorticity in fluid mechanics to give next week. Anyway, all that reminded me of this classic sequence from the original radio series The Hitchhiker’s Guide to the Galaxy, by the late great Douglas Adams. I particularly agree with the conclusion “that if life is going to exist in a Universe of this size, then the one thing it cannot afford to have is a sense of proportion”.