Whacky Astronomy

Last week, the Hubble Space Telescope recorded the first visible-light photo of a planet beyond our solar system. It's an inspiring moment. There are surely millions of other worlds in our galaxy, but because "exoplanets" are distant and emit no light, glimpsing them has been a challenge. The photographed planet orbits a star called Fomalhaut, which is close in galactic terms -- 25 light-years away. The planet appears to be three times the size of Jupiter and much farther from its star than Jupiter is from the sun, meaning our type of life is unimaginable there. But at least humanity has finally seen a world beyond the solar system. Separately, astronomers using telescopes in Hawaii obtained an electronically enhanced image of three planets orbiting a star similar to the sun. It is assumed the Milky Way contains vast numbers of stars similar to the sun, but this is the first time one with a system of planets has been observed. The star is 125 light-years distant, and the planets, all gas giants larger than Jupiter, could not support our form of life. Here is the inspirational aspect of the second discovery: The star is young, and its planets appear to be about 60 million years old, versus an age of approximately 4.5 billion years for the Earth. Creation has existed for unfathomable lengths of time, yet stars and planets are still forming, some right in our neighborhood.

Though the planet dubbed Fomalhaut B is nearby in galactic terms, sending a probe there is out of the question. Warp speed, hyperdrive and the rest exist solely in sci-fi -- unless there is something fundamental about physical law that is not yet known, nothing formed of matter can exceed the speed of light. At the highest velocity ever achieved by a manmade object, the 14 miles per second recorded by the New Horizons probe on its way to Pluto, travel to Fomalhaut B would require about 600,000 years. The fastest naturally accelerated complex object ever observed, this neutron star, moves at about one-half of 1 percent of light speed: at that speed, it would take about 5,000 years to reach Fomalhaut B. Since acceleration to half of 1 percent of light speed is known to be possible, we should assume humanity eventually will learn how to do this with large objects. Starships moving at half a percent of light speed could zip around the planets of our solar system like nobody's business. But they still would be worthless for visiting even relatively nearby worlds.

Atom smashers already push individual subatomic particles to 99 percent of light speed, so assume for the sake of argument that large-object acceleration to this velocity will be possible someday. The energy requirement would be unfathomable, but then, the 70,000 pounds of thrust produced by the new F-22 fighter would have been viewed as unfathomable power two centuries ago. At 99 percent of light speed, a trip to Fomalhaut B would require about 25 years, which would seem like only a few years to the ship's crew, owing to time dilation. So if complex objects can be accelerated to somewhere near the speed of light, travel between adjacent star systems might happen someday.

Sadly, so might war. Suppose there's an Earth-like world orbiting Fomalhaut that is inhabited by an advanced society. Their astronomers noted Earth, and centuries ago they sent an automated probe here to keep an eye on us. In 1948, the probe broadcast a radio code signaling humanity had acquired the hydrogen bomb. Traveling at light speed, that message arrived in 1973. Now suppose the advanced world orbiting Fomalhaut is warlike, or merely paranoid. The beings there worry that humanity will acquire the 99 percent stardrive and try to invade their world. They decide to stage a pre-emptive strike while Earth's space technology is still rudimentary. They launch hundreds of large bombs toward Earth at 99 percent of light speed, so we won't even know the bombs are coming.

I don't think this will happen -- I think that although intelligent life will turn out to be present on many worlds, the odds will be against multiple intelligent societies evolving near each other at the same time. Contact with an alien civilization is more likely to come in the form of messages sent from a very great distance than as weapons sent from nearby. But if acceleration to a good percentage of light speed is possible, then relatively nearby worlds could attack each other, and it's a concern. Flip the situation around. Suppose it's a couple of centuries from now and Earth has acquired 99 percent stardrive. We discover that an intelligent species on a planet orbiting Fomalhaut just detonated its first hydrogen bomb, then landed on its moon. We would know that we have a window in which to stage a pre-emptive strike to wipe out life on that world, eliminating any threat to Earth. But if we wait, the life forms there might become advanced enough to strike us. In this situation, how might humanity act?