Interstellar Travel Could a spacecraft make the journey to that other civilisation in a reasonable time? How long would it really take to make that visit? The currently fastest spacecraft speeds are around 20 km per second. For example, Voyager 1 is now moving outwards from the solar system at a speed of 16 km per second. At this rate, assuming that it was on the correct course, it would take 85,000 years to reach the nearest star - 3,000 human generations! How fast? Could we go faster? In principle yes, provided we stick within the upper limit given by Einstein's special theory of relativity: 300,000 km per second, i.e. the speed of light and 20,000 times faster than the current speed of our Voyager spacecraft. Even assuming that we could reach a speed of 1/10th of the velocity of light, it would still take a minimum of 40 years or so to reach our nearest star and if you allow for acceleration an deceleration probably nearer to 100 years. The costs of accelerating a craft to speeds approaching that of the velocity of light become prohibitively expensive and even a speed of one tenth of this is pretty daunting. Travelling fast and far - and for a long time! What seems to be a more realistic possibility is that a civilisation, perhaps driven by the need to escape a planet which has become inhospitable for life, might sent out craft at a speed of 1% of that of light - still 200 times faster that our fastest spacecraft - which could reach nearby planetary systems in around 1000 years. (They would have to hope that such planets can be found!) A crew of perhaps 1000 colonists might build up their numbers until they too might send out further spacecraft after, perhaps, a further 500 years. In this way, one original civilisation could eventually colonise all the habitable planets in the Galaxy, taking about 20 million years to do so. This is a very short time compared to the age of the Milky Way galaxy, effectively "instantaneous", and some people argue that since, at yet, no colonising spacecraft has apparently reached our Earth, then no other advanced civilisations have arisen in our Galaxy! Travel is expensive In summary, whilst relatively fast interstellar travel, say at up to one tenth of the velocity of light, is not impossible, it is exceedingly expensive, requiring enormous energy resources. It may not be the best way to communicate with a foreign civilisation, and certainly not the fastest one, at least to start with! Perhaps we should look at a cheaper and faster method of communication. The obvious medium to use is that of electromagnetic radiation. It is possible (if not trivial), relatively cheap and certainly fast - you cannot beat the speed of light!