Tuesday, December 10, 2013

15 Million Years After the Big Bang, Everywhere in the Universe was in the Habitable Zone

One of the key questions for astrobiologists is where in the universe life might have taken hold. Their standard approach is to look for places that are warm enough to keep water in liquid form and so allow chemistry similar to our own.

That’s given rise to the idea of circumstellar habitable zones—regions around stars that are not too hot and not too cold but just right for liquid water. Goldilocks zones as they are sometimes called.

But in recent years, planetary geologists have pointed out that various other mechanisms might keep planets and moons warm enough for liquid water. For example, tidal heating can generate considerable heat. This is the squeezing and squashing of a body as it moves through a powerful gravitational field and the process that maintains a salty ocean beneath the ice on Jupiter’s moon Europa. Radioactive decay also generates heat and keeps the interior of our planet warm.

Now Abraham Loeb at Harvard University in Cambridge says there is another mechanism that creates a Goldilocks zone but in this case the zone is in time rather than in space. He says this mechanism would have created a Goldilocks zone that filled the entire universe for a few million years soon after the Big Bang. If he’s right, that means life could have evolved some 10 billion years before it cropped up on Earth.

The key phenomenon in Loeb’s reasoning is the cosmic microwave background radiation, the afterglow of the Big Bang which fills the universe with light.

This radiation was once blazing hot. But as the universe has expanded, the wavelength of this light has increased and become less energetic. Today, it is freezing with a temperature of around 3 Kelvin.

Loeb points out that as it cooled, at some point this radiation must have once been amenable to life. Indeed, it would have been warm enough to maintain water in liquid form on a planet, regardless of its distance from its parent star.

And Loeb has calculated exactly when. He says the cosmic microwave background radiation would have had a temperature of between 273 and 300 Kelvin (between 0 and 30 degrees C) about 15 million years after the Big Bang and this would have lasted for several million years. That would have allowed “the chemistry of life to possibly begin when the Universe was merely 15 million years old,” he says.

That’s an exciting possibility but one that comes with a number of caveats. The first is the question of whether planets could have formed at all at this stage of the universe.

link.

1 comment:

Anonymous said...

This is a cute notion but it's pretty hard to take it seriously. 15 million years for heavy element synthesis /and/ terrestrial planet formation /and/ the rise of life? Hum.

That said, he touches on an interesting point: there was a long period where the CMB was warm enough to be a factor in planetary evolution. Very very old planets might show traces of this period, which would be pretty cool.


Doug M.