Wednesday, August 12th, 2009

Another Galaxy

A few days ago I heard a report on the radio discussing the music that was sent out on the voyager spacecraft. The craft are on their way to another galaxy according to the person on the radio.

Well I giess strictly speaking that is true but at the speed they are travelling it will take them billions of years before they even get to leave this galaxy in order to start their intergalactic trip – and that assumes that they are not shot down by Klingons before they get that far (as portrayed in the movie Star trek 5).

The problem is that people are always getting confused between stellar systems and galaxies. Our particular stellar system is called the solar system since the star at the centre of the system (our sun) is sometimes called Sol. Our galaxy is often referred to as the milky way galaxy since the densest part of the galaxy visible to us was first called the milky way. Our stellar system contains one star (some contain two or even three) but galaxies contain millions of stars. Every star you can see in the sky (with rare supernova exceptions) is in our milky way galaxy.

The only reason the voyager spacecraft are headed for another galaxy is that once they had made the visits to the planets that are within the solar system their planned journey was complete and the direction that they head outward into our galaxy was pure chance. The record of music and other materials on the craft were placed there on the basis that it effectively cost nothing to put them there and in the remote chance that something does find the craft many billions of years from now the finder will at least have some record that at one time we existed.

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