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[ti:Are There Strangers in Space?]

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[00:01.47]Lesson 43

[00:03.56]Are there strangers in space?

[00:12.47]What does the 'uniquely rational way' for us to communicate with other intelligent beings in space depend on?

[00:22.11]We must conclude from the work of those who have studied the origin of life,

[00:26.87]that given a planet only approximately like our own, life is almost certain to start.

[00:34.34]Of all the planets in our solar system, we are now pretty certain the Earth is the only one on which life can survive.

[00:43.34]Mars is too dry and poor in oxygen, Venus far too hot, and so is Mercury,

[00:50.89]and the outer planets have temperatures near absolute zero and hydrogen-dominated atmospheres.

[00:58.38]But other suns, start as the astronomers call them, are bound to have planets like our own, and as is the number of stars in the universe is so vast,

[01:08.11]this possibility becomes virtual certainty.

[01:12.33]There are one hundred thousand million starts in our own Milky Way alone,

[01:17.34]and then there are three thousand million other milky ways or galaxies, in the universe.

[01:23.88]so the number of stars that we know exist is now estimated at about 300 million million million.

[01:33.03]Although perhaps only 1 percent of the life that has started somewhere will develop into highly complex and intelligent patterns,