For many decades scientists have been asked about the possibility of extraterrestrial life. Again and again they have been posed these questions:
- Are we alone in the universe?
- Is there life on other planets?
- Is there intelligent life on other planets?
- Do extraterrestrial civilizations exist?
- If everyone in the world threw a deck of cards into the air 1000 times, that would be almost 10 trillion chances for such flying cards to form into a house of cards, but we should not expect that in even one case would the flying deck of cards accidentally form into a house of cards.
- If a billion computers around the world each made a thousand attempts to write an intelligible book by randomly generating 100,000 characters, that would be a total of a trillion chances for an intelligible book to be accidentally generated, but we should not expect that even one of these attempts would result in the creation of an intelligible book.
- If you buy a million tickets in a winner-take-all lottery in which the chance of winning is only 1 in 100 million, you should not expect that any one of those tickets will succeed in winning such a lottery.
- It is not necessarily true that many chances (also called trials) will yield many successes.
- It is not necessarily true that many chances (also called trials) will yield some successes or even one success.
- If the chance of success on any one trial multiplied by the number of trials gives a number less than 1, we should not expect that even one of the trials will produce a success.
- If the chance of success on any one trial multiplied by the number of trials gives a number greater than 1, we should expect that at least one of the trials will produce a success.
The last of these lines verifies that the likelihood of at least one success is slightly greater than 50 percent if there are 1001 trials that have each a chance of success of 1 in 1000.