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How many earth-like planets are thought to exist in the universe?

Answer 1

Extrapolation from current estimates suggests upwards of #10^20# Earth-like planets in the universe.

Depending on how one defines "Earth-like," current estimates based on data from the Kepler mission suggest that there are somewhere between 1 and 50 billion "Earth-like" planets in the Milky way alone.

Let's take the low end of that estimate (#1xx10^9# planets).

If there are more than 100 billion (#10^11#) galaxies in the universe, and each is similar to the Milky Way (some are larger, some are smaller, but as an estimate it works), then each of those galaxies would also have a billion Earth-like planets.

The total number then is #10^11# galaxies times #10^9# planets / galaxy:

#10^11*10^9=10^20#

#100,000,000,000,000,000,000#

That is a LOT more sand grains than there are likely on all of Earth's beaches combined.

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Answer 2

Leah Abbate

There may be billions of Earth-like planets in the universe, according to estimates.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.