Faint Young Sun Paradox

There are two things.

One is the astrophysical expectation that during the main sequence lifetime of earth, Sun’s output would be only 70% as intense at 2 billion years back as it is currently.

The second thing is that, if this were true, then all the surface waters of earth should have been frozen 2 billion years ago.

But there are lots of geological evidences that show that earth had liquid water in its early history. What goes wrong?

This is called Faint Young Sun Paradox.

Why Earth avoided the deep freeze is a question that has puzzled scientists for so many years.

Recently, the researchers have given a new explanation to Faint Young Sun Paradox. They have recently put forward a theory that Earth would have to be 6 or 7 percent closer to the sun than it is now. It’s a few million miles, but from an orbital mechanics standpoint, it’s not that far. The question is what could make a planet move from one location to another?" Professor proposes that Earth may have migrated from the sun over time through a process called planet-planet scattering, which occurs when one planet or more is ejected from its orbit, an increase in orbital separation occurs, or when planets collide.