What if We’ve Completely Misunderstood Our Place in the Universe?
By Annalee Newitz
A Harvard astronomer has a provocative hunch about what happened after the Big Bang.
Our universe is about 13 billion years old, and for roughly 3.5 billion of those years, life has been wriggling all over our planet. But what was going on in the universe before that time? It’s possible that there was a period shortly after the Big Bang when the entire universe was teeming with life. Harvard astronomer Avi Loeb calls this period the “habitable epoch,” and he believes that its existence changes how humans should understand our place in the cosmos.
We have one snapshot of life in the early universe, taken about 400,000 years after the Big Bang. This image is known as the Cosmic Microwave Background (CMB), and it’s what astronomers see when they aim their telescopes at the farthest edges of space, capturing light that has been traveling through the universe for billions of years—and from billions of years ago. Remember, light takes a while to reach Earth (it travels at only 186,000 miles per second), so the starlight you see in the sky at night is often thousands of years old. The CMB is a lot older than that. It’s from the time when the universe hadn’t yet developed stars. . . .
. . . And that’s when things get interesting. These days when astronomers discover a planet, the news is usually accompanied by the disappointing report that it’s not in a “habitable zone,” which is to say the exact orbit required to keep water in a liquid state. If the planet is too close to its star, all the water has boiled away; if the planet is too distant, the water is frozen solid. Given that life as we know it requires water, most astronomers assume that life could only develop on a planet in its solar system’s habitable zone.
But in the early universe, as Loeb speculates in a paper published in Astrobiology late last year, everything would have been a habitable zone. 10 to 20 million years after the Big Bang, the universe was still bathed in that warm gas we saw in the CMB, but it had cooled down to a temperature that would keep water liquid no matter where it was relative to its star. The ambient temperature of the universe would provide enough heat to turn an ice giant like Neptune into a water giant. That’s why Loeb has dubbed this era the “habitable epoch.” . . .
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