Posts by David Webb

Allen telescope array begins alien hunt

Distance <= 500 light years

The NYT articles says that the million stars are within 500 light years.

"

Dr. Shostak calculated that the full Allen array would be able to detect a signal from as far as 500 light years that is only a few times more powerful than what can now be sent by the Arecibo radio telescope, a 1,000-foot-diameter dish in Puerto Rico that is the world’s largest (although it is in danger of being shut down to save money). That translates to about a million stars, which he said was getting into a promising number. Dr. Shostak described the expanded search as looking for the needle in the proverbial haystack with a shovel instead of a spoon.

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so the signals would be at most 500 years old.

Martian ice swaps poles every 25,000 years

Mars Tilt

According To MSN encarta

"

A major difference between Earth and Mars is the stability of the tilt of the planet’s axis. Due to gravitational effects of the Moon, Earth maintains a relatively stable 23.5 degree tilt on its axis, with only a slight wobble (obliquity) between about 22.1° to 24.6° over a timescale of millions of years. Without a large moon, and being closer to the strong gravitational pull of Jupiter, Mars has a much more dramatic wobble to its axis, resulting in a tilt that may shift from 0 degrees to 60 degrees and causing major climate shifts over time, between massive ice ages and relative warm periods. When the tilt of Mars is nearly vertical, the polar caps may expand almost to the equator. At its greatest tilt, one pole is warmed almost directly by the Sun, likely releasing the deposits of frozen water and gas into the atmosphere.

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see

http://encarta.msn.com/encyclopedia_761566582_5/Mars_(planet).html#p71