Is the Earth unique in harboring intelligent life? Even ifanother civilization is trying to contact us, it will soonbe too late, according to SETI's Frank Drake, because TV isbeing delivered more and more by cable and satellites, whichdo not leak radio waves into space.
David L. Chandler writes in New Scientist that according toDrake, for ETS, "the Earth is going to disappear" very soon,since these signals "are the strongest signs of our existence."
Traditional TV broadcast antennas put out one megawatt each,and these waves now extend about 50 light years out from oursolar system. But cable and satellite TV is changing allthat. Cable does not leak waves and satellites put out just20 watts per channel, all of it directed straight downtowards Earth. Drake thinks we have only about 100 yearsleft, before the evidence that we exist vanishes from space.
Maggie Fox writes that our solar system may be unique afterall, despite the discovery of at least 120 other solarsystems with planets. Astronomer Mario Livio says, "Maybethese other extrasolar systems?contain only the giantplanets." (Giant planets like Jupiter protect the innerplanets from asteroid impacts that would destroy life). "In(our) solar system the orbits are very circular. Most of thegiant planets observed in extrasolar systems have veryelliptical orbits?If the orbit is very elliptical then theplanet may come very close to its sun at some point and thatdoesn't appear to be very healthy for life."
Livio says that when planets are formed?"dust coagulates andforms small rocks and the rocks combine and form smallbodies and then those bodies form things like Earths. TheEarths collect and accrete gas and then they form giantplanets like Jupiter. That is one model.
"Then there is a second model that has been suggestedspecifically for the formation of giant planets likeJupiter. You start with a gas disk and this disk becomesunstable and it breaks up into large clumps and those clumpsare the things that form giant planets. In that model it isnot obvious at all how planets like Earth may have formed."
It could be that our solar system formed the first way andmost of the others formed the second way, meaning there areno smaller planets that could contain life orbiting in theinterior.
This means the reason we haven't been contacted yet?IF wehaven't?could be that there's nobody else around. Somepeople despair of ever achieving alien contact, while othersare already unlockingalien closets.
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