Imagine that we live in the midst of a hyperdense globular cluster, surrounded by a galaxy's worth of matter packed carefully into a sphere a few light-years across. Such an extraordinary vantage point has a gravitational redshift approaching infinity — it's on the verge of becoming a black hole! — but nowhere are there any extreme forces. We climb up and down ladders, float in balloons, take interplanetary rocket rides, and live perfectly normal lives. Our society thrives on an ordinary planet circling an ordinary sun.
But looking up, we see the rest of the universe moving millions of times faster! Our world is in a time machine, plunging into the future at a tremendous rate. We watch alien civilizations flower and die, stars evolve, and galaxies whirl. We do so through protective instrumentation, of course, since ordinary light is blueshifted into gamma ray wavelengths as it falls down upon us.
How to engineer this gargantuan artifact? Let mass density outside our central solar system fall off inversely with distance. Then the local acceleration is a constant; we can make it a comfortable one gee, a normal Earth gravity. (The inverse-square law of Newton is counterbalanced by a growing amount of mass.) To keep us from cooking we had better use mostly cold material ... dead neutron stars, small planets, stellar-mass black holes, whatever. We must take care to synchronize orbits so that objects don't collide, and we have to keep interstellar gas or dust away. Assembling our cluster will liberate huge amounts of gravitational binding energy, plenty to cover the costs of bringing the masses together.
The result is a cosmological observatory — perfect for impatient astronomers who want to personally see the evolution of the universe to its ultimate end. And when the show's over we can fold our tent, collapse into a singularity, and leave behind only a tidy supermassive black hole a few light-minutes across. Neat!
Saturday, September 11, 1999 at 19:29:21 (EDT) = 1999-09-11
(correlates: AllSunsets, BindingEnergy, DiggerWasp, ...)