3. Earth, No Ordinary Rock (1)

Do you believe in aliens? Do you believe in UFOs? Do you believe life exists on other planets?  Many surveys indicate perhaps as many as 60% of Americans believe in life on other planets. Why? Well, it could be due to a constant diet of science fiction in the movies and on TV, such as Star Wars, War of the Worlds and Star Trek, but, also because of the strong popular belief of the 1990s that the universe had to be full of alien life.

Just an Ordinary Rock?

Cosmologist, scientist and author Dr. Carl Sagan, himself an atheist, was a strong believer in extraterrestrial life. He played a leading role in NASA’s Mariner, Viking, Voyager, and Galileo spacecraft expeditions in the 1970-1990 period.  He also introduced the universe to the public via his mega-hit television series Cosmos as well as through his many popular science publications.

One of Sagan’s best known statements is about our planet earth. Contemplating a Voyager picture taken in 1990 of earth at a distance of four billion miles (the well known Pale Blue Dot picture) he wrote:

“There is nothing unusual about earth. It is an average, unassuming rock that’s spinning mindlessly around an unremarkable star in a run-of-the-mill galaxy – a lonely speck in the great enveloping cosmic dark.”[1]

On the surface his point makes logical sense. Why would it be unique? If earth formed 4.6 billion years ago, as scientists claim, what makes it unique? The universe is full of planets, many the same size and composition as earth, so if we are just a rock on which life happened to evolve, there must be oh so many other planets like us where too life chanced to evolve.

A few numbers make this case even stronger. earth is part of our solar system, one of the nine (or is it eight, now that we’re uncertain about Pluto) planets that orbit the sun. Our sun is part of a large collection of stars in our galaxy, which we call the Milky Way galaxy. In the Milky Way alone, there are an estimated one hundred billion (100,000,000,000) stars. That is about 15 stars for each person on earth. And just like the sun, many of these stars have planets in orbit. If there are so many planets, just in our galaxy alone, chances seem very good for finding life!

Go beyond the Milky Way, and the numbers soar even farther beyond the limits of our imagination. In the total universe the number of stars is estimated to be in the order of ten billion trillion – 10 with a whopping 22 zeroes! So it is safe to say at least that many planets (10²²), or about one trillion planets for every person who has ever lived on earth. How can we be so arrogant to think the earth could be unique? Some scientists estimate as many as ten trillion (10¹³) advanced civilizations. Sagan set this number at one million for our Milky Way galaxy alone![2]

In the last decade our knowledge of the universe has grown exponentially. Observations via satellite telescopes, our advancing knowledge of forces at work in space, growing insights into the complexity of living cells, and a better understanding of the required conditions for life to exist has lead to a new branch of science called astrobiology. This disciple studies the possibility of life in the universe by combining insights from astronomy, biology and geology . Application of this recent knowledge to our planet earth has given us a fresh look at how unique our home planet really is.

What would E.T. look like?

What would alien life look like? To scientifically explore the likelihood of life on other planets we must define criteria for this life. What properties would alien life exhibit?

If we would believe Hollywood , then “everything goes.” Aliens could dramatically differ from earth life in many, many ways. Some might have acid in their veins, breathe toxic gasses, require extreme hot or cold temperatures; life can be very different from ours. Wait – is that realistic?

We need to realize that all the laws of nature on earth are the same throughout the universe. The same is true of chemistry and biology, the table of elements and characteristics of solids, liquids and gasses such as water and oxygen.

Therefore life elsewhere would be subject to the same “rules” as life on earth. Given these laws of nature we know our kind of life is the only type of life possible. Any life anywhere in the universe would require the same building blocks and demand the same conditions that make life possible on our planet.

Simply said – if E.T. exists and there is life on other planets, it will be quite similar to life as we know it: carbon based (complex organic molecules built from combinations of carbon, oxygen, hydrogen and nitrogen) with specific restrictions on gravity, presence of water, atmosphere, temperature, size, etc. In other words, any planet that supports life would have to be similar to earth, very similar. And E.T. would not be that different from us!

Next: (2) Exhibit #3: Rare Earth

 

back to: 2. Studying the Big Bang
(1) Just an Ordinary Rock?	(2) Exhibit #3: Rare Earth
(3) Likelyhood of other Habitable Planets	(4) Exhibit #4: Designed for Discovery
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