Physics Concepts and Definitions

How many other planets in our galaxy could sustain life?
Answered by Dr. Michio Kaku
  • Dr. Michio Kaku

    Dr. Michio Kaku

  1. Dr. Michio Kaku Theoretical Physicist and Author


    Sometimes I get asked the question, "Professor, the universe is so big. Are we alone?" I don't think so. In fact, we now have some numbers that substantiate that. The Hubble Space Telescope orbiting in outer space right now has given us the first census of planets in the galaxy that may have life on them. It turns out that out of every 200 stars you see at night, one of those stars can have a planet in the habitable zone, the Goldilocks Zone -- not too close where the oceans would boil, not too far from where the oceans would freeze but just right to have liquid oceans. Why liquid oceans? Because water is the universal solvent. It dissolves most things including the organic materials of life like DNA.

    Think about it. Our galaxy contains billions of stars. This means that perhaps 500 million planets in our own backyard, in our own Milky Way Galaxy may have planets carrying liquid oceans and perhaps even life. In the future, when you look at the night sky, you will have an existential shock knowing that here, there, there, there are twins of the Earth. When you look at the night sky, you will always wonder is anyone looking back.

    More answers from Dr. Michio Kaku »

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