Originally posted by skep
I'm taking # 6 since it is so simple and the assumption of fundies is so inept it should be easy even for you to see the error. I am counting on an honest appraisal fom you. "Time, whatever that is, will tell" if I get it.
The Second law of T D has not one but two parts. Fundies ignoe the second and qualifying postulation related to ambient atmosphere and glom onto a misunderstanding of the first part. Your assumption is simply bad science. If people bend confirmed scientific theory to their own interprettion what we have is not science...but religion. Bend all you want because misunderstanding and ignorance changes only the safety of innocents but they do not change reality.

Originally posted by edsinger
Scientific Fact No. 10 - Radio Silence from Space Proves Evolution is Wrong

Mars is not the only place that shows no signs of life. The entire universe lacks any sign of life. There are no radio signals that can be related to intelligent life forms. None of the billions of galaxies has been found to emit any intelligent radio signals. Scientists have been pointing every type of radio telescope possible into space for several decades in hopes of finding an intelligent signal. No signs of life beyond Earth have been found. We are alone.

Visiting another civilization on a distant world would be fascinating, but at present is beyond human capabilities (see Project Orion and Project Daedalus for some attempted solutions).

However, it is perfectly within reach to develop a communications system using a powerful transmitter and a sensitive receiver, and use it to search the sky for extraterrestrial worlds whose citizens have a similar inclination as terrestrials. A basic assumption of SETI is the that of "Mediocrity" [1]: the idea that humanity is not exotic in the Cosmos but in a sense "typical" or "medium" when compared with other intelligent species. This would mean that humanity have enough similarity with other intelligent beings that communications will be mutally desirable and understandable. If this basic assumption of Mediocrity is correct and other intelligent species are present in any number in the galaxy at our technological level or above, then communications between the two worlds should be inevitable.

SETI is still no trivial task. The Milky Way galaxy is 100,000 light years across, and contains a hundred billion stars. Searching the entire sky for some far-away and faint signal is an exhausting exercise.

Some further simplifying assumptions beyond Mediocrity are useful to reduce the size of the task. One is to assume that the vast majority of life-forms in the galaxy are based on carbon chemistries, as are all life-forms on Earth. While it is possible that life could be based around atoms other than carbon, carbon is well known for the unusually wide variety of molecules that can be formed around it.

The presence of liquid water is also a useful assumption, as it is a common molecule and provides an excellent environment for the formation of complicated carbon-based molecules that could eventually lead to the emergence of life.

A third assumption is to focus on Sun-like stars. Very big stars have relatively short lifetimes, meaning that intelligent life would not likely have time to evolve on planets orbiting them. Very small stars provide so little heat and warmth that only planets in very close orbits around them would not be frozen solid, and in such close orbits these planets would be tidally "locked" to the star, with one side of the planet perpetually baked and the other perpetually frozen.

About 10% of the stars in the Milky Way galaxy are Sun-like, and there are about a thousand such stars within 100 light-years of the Sun. These stars would be useful primary targets for interstellar listening. However, we know of only one planet where life exists, our own. There is no way to know if any of the simplifying assumptions are correct, and so as a second priority the entire sky must be searched.

Searching the entire sky is bad enough. To find a radio transmission from an alien civilization, we also have to search through most of the useful radio spectrum, as there is no way to know what frequencies aliens might be using. Trying to transmit a powerful signal over a wide range of wavelengths is impractical, and so it is likely that such a signal would be transmitted on a relatively narrow band. This means that a wide range of frequencies must be searched at every spatial coordinate of the sky.

There is also the problem of knowing what to listen for, as we have no idea how a signal sent by aliens might be modulated, and how the data transmitted by it might be encoded. Narrow-bandwidth signals that are stronger than background noise and constant in intensity are obviously interesting, and if they have a regular and complex pulse pattern are likely to be artificial.

However, while studies have been performed on how to send a signal that could be easily decoded, there is no way to know if the assumptions of those studies are valid, and deciphering the information from an alien signal could be very difficult.

There is yet another problem in listening for interstellar radio signals. Cosmic and receiver noise sources impose a threshold to power of signals that we can detect. For us to detect an alien civilization 100 light-years away that is broadcasting "omnidirectionally", that is, in all directions, the aliens would have to be using a transmitter power equivalent to several thousand times the entire current power-generating capacity of the entire Earth, ruining their own planet by doing so.

It is much more effective in terms of communication to generate a narrow-beam signal whose "effective radiated power" is very high along the path of the beam, but negligible everywhere else. This places the transmitter power within reasonable ranges, the problem being now of having the good luck to coincide with the path of the beam, with the possibility approaching to zero as distance increases.

Such a beam might be very hard to detect, not only because it is very narrow, but because it could be blocked by interstellar dust clouds or garbled by "multipath effects", the same phenomenon that causes "ghosted" TV images. Such ghosts occur when TV transmissions are bounced off a mountain or other large object, while also arriving at our TV antenna by a shorter, direct route, with the TV picking up two signals separated by a delay.

Similarly, interstellar narrow-beam communications could be bent or "refracted" by interstellar clouds to produce multipath effects that could obscure the signal. If interstellar signals are being transmitted on narrow beams, there is nothing we can do at this end to deal with this problem other than to be alert.