Life in our Galaxy

The Milky Way galaxy as seen from Earth via a special camera. (NASA)

If we do assume that Earth has been visited by extra-terrestrial beings and we do accept they have not originated in our own solar system, then we must consider other stars in our galaxy. There are a hundred star systems within twenty-one light years of Earth (A light year is a measure of the distance a light beam can travel in one year). Several of these are considered good candidates to have planets and could be the home port for a visiting UFO.

Earth's solar system lies in the "Milky Way" galaxy. A galaxy is a group of stars that number in the billions. Galaxies may be one of several shapes, but typically appear as flat spinning discs (perhaps 10,000 light years thick) with trailing arms. Between galaxies are immense voids empty of stars. You can see our galaxy at night by looking for a wide band thick with stars stretching across the sky. What you see is the edge of the disc. When we accept that our visitors are from our galaxy, but not our solar system, we are faced with a problem. Travel to even the closest of other stars in our galaxy is a considerable trip. A ship going at the speed of light would take over eight and a half years to make a round trip to Alpha Centauri, the nearest star. Even that schedule seems optimistic as the laws of physics, as we understand them today, would not permit a spaceship to go that fast.

As a spaceship is accelerated it's mass increases. If a spaceship is accelerated to near the speed of light, it mass increases to near infinity. The more mass there is the more energy is needed to accelerate it and as the ship approaches the speed of light the energy needed becomes greater than the amount of energy in the universe.

It is possible, though, to accelerate a well designed spaceship to some significant fraction of the speed of light. Say ten or fifteen percent. A spaceship traveling at that speed could make the trip to the nearest star in forty years. Trips to, or from, the stars most likely to be populated would take about a century. While this might be acceptable for unmanned, one way explorations, a round trip would be longer than a human life. (On the other hand there is no proof that visitors from the stars would be limited to human life spans.)

If they were limited to a life span like ours there are still some strategies they could employ to travel the distance. (These are the same approaches, suggested by authors Eugene Mallove and Gregory Matloff, that we would use to travel to another star).

A "World" Ship - A journey could take hundreds of years and generations would be born and die on the spaceship before the destination was reached.

Extended Life - A modification to the crew, rather than the ship, would allow the crew to live the necessary hundreds or even thousands of years need to reach a destination.

Suspended Animation - Putting the crew in an artificial hibernation to extend their lives during the voyage.

Slowing Time - If a ship approached some significant portion of the speed of light, time slows down. This makes the trip seem shorter for the crew.

These strategies suggest a one-way trip. The crew, employing any but the "World Ship" approach, upon returning home after an extended voyage might find themselves greeted by their own grown great grandchildren. Their civilization would be several generations further along than when they left it and all their friends dead. Volunteers for such an expedition might be few.

Is there a way of traveling faster than the speed of light? Current theory says no. The same theory, though, does suggest their might be "shortcuts" though space. So called "wormholes" might allow a ship to disappear from space in one location and reappear in another a thousand light years away. They might even permit intergalactic travel or travel across time.

Such wormholes, if they do exist, most likely are fleeting, small tunnels that may not allow objects larger than a few atoms to pass. And they would only appear under the most exotic conditions. The technology that would allow the creation of a wormhole on demand that would be large enough to conduct a spaceship seems to be the realm of science fiction. If an actual "hyperspace" drive based on this principle is possible, it is hundreds, if not thousands, of years in the future.

A spiral galaxy.