Quote:
Originally Posted by lene1949
But if there were intelligent life elsewhere, why shouldn't they visit earth, if they have the means to do so...  |
That is two very big "ifs"-- IF there is intelligent life elsewhere, and IF they have the means to do so.
When I say that there is likely life elsewhere, I mean any form of life, even the equivalent of a bacterium or even simpler. I mean a little green slime, not Little Green Men. Intelligent, technological life is going to be much less common than single-celled and simple life. The second question is "the means to do so." Neglecting any science fiction fantasies that we have some fundamental misunderstanding of physics and that in the future someone will discover a reasonably easy way around that pesky light speed barrier, interstellar travel is staggeringly slow and difficult. Space is big. Really big. You just won't believe how vastly hugely mindboggingly big it is. I mean you may think it's a long way down the road to the chemist, but that's just peanuts to space. (It isn't plagiarism when I expect people to catch the reference.) Any species that happened to be advanced enough to travel interstellar distances is not going to be so unsophisticated as the clumsy buffoons believed in by UFOers.
There used to be a nice site where you could plug in the acceleration and mass of a ship and it would give you the travel time (including deceleration to the destination starting at the half-way point), relativistic mass, and amount of energy needed. That calculator looks to be
gone Here is a less elegant one that won't give you the staggering energies involved, and I'm not sure if in "velocity" they calculate a steady velocity or acceleration at that rate (it was clear in the old calculator) but it will give you an idea time frames:
http://orimath.com/oritutorial/RelCalc01.html
Plugging in the speed of our fastest interstellar craft (Voyager 1) of about 17.5 km/s, reaching Proxima Centari's distance of 4.2 light years would take nearly 72,000 years. Manage to get it going 1,000 times faster? It'll still take 72 years. Of course, if you could get the ship to 0.99999 light speed, the travel time from the reference frame of the traveler would be just under a week-- but the ship's mass (from the POV of an outside observer) would have increased by more than 200 times. Good luck finding a reaction mass for that!
If you haven't before, take a look into the ideas of the
Fermi Paradox and the
Drake Equation.