Re: Set the controls for the heart of the Sun

Eliezer S. Yudkowsky (
Fri, 22 Aug 1997 14:08:19 -0500

Carl Feynman wrote:
> The center of the Sun is far denser than ordinary lead. The bomb, at zero
> pressure, has about the density of silicon. It is true that on its way down
> it will encounter layers denser than this, but by the time it gets there, it
> will be under much more pressure, and will be compressed to be much smaller,
> so it will still be denser than the surrounding gas. In fact, it will
> always be at least several times denser than the medium it is faling through.
> This is provided that it is not substantially hotter than its surroundings,
> since being hotter makes it expand and reduces its density. While it's
> dropping, it will be heated by compression, but the medium around it is also
> heated by compression, so as long as the bomb is cooler at the surface it
> will stay cooler all the way down. So it is important to deliver it to the
> surface of the Sun in a way tha leaves it no hotter than the Sun itself.
> That means that it has to be placed rather gently on the surface of the Sun,
> rather than being dropped in at orbital velocity (200 km/sec). Forrest
> Bishop's message suggested doing this by halting an orbiting bomb in its
> orbit using a gravitational slingshot manuver. Unfortunately, this won't
> work because such manuvers are limited in their delta-v to the escape
> velocity for the bodies concerned, which for planet-size objects are only
> tens of kilometers per second. I was imagining using mass drivers on the
> bomb to bring it suddenly to a halt by catching a bunch of mass going the
> other way in the same orbit. I'm not sure it's feasible; there's a lot of
> waste heat.
> --CarlF

Okay, here's my idea:

Take a large, but not too large, sheet of ice. Attach a block of ice to one
side of the sheet. Frozen inside this block is the bomb. Now, send this into
the sun, with the bomb on the side facing away.

The sheet of ice acts as a lightsail. As the bomb gets close to the sun, the
lightsail evaporates while slowing the fall. Ideally, the lightsail should
disappear at about the same time the bomb touches the "surface" of the sun.

Some additional notes:

If ice evaporates too fast, we can use a metal of some other melting point instead.

If we put a fast-evaporating core of material, either into the light sail or
the bomb box, then when the lightsail finally evaporates, the material will
puff up, kick the bomb back for a final slowdown, and act as an insulating
vapor cushion.

All that ice helps keep the bomb cool.

We can spin the whole circular lightsail to keep it from turning away.

--       Eliezer S. Yudkowsky

Disclaimer:  Unless otherwise specified, I'm not telling you
everything I think I know.