Faint young Sun paradox

Imagine you have a pet plant named Sunny that needs sunlight to survive. However, the amount of sunlight it needs changes over time. When Sunny was a baby plant, it needed a lot of sunlight to grow strong and healthy. But as it grew older, it needed less sunlight.

Now, scientists have been studying the sun - the big ball of flaming hot gas in the sky that gives us sunlight - and they've discovered something strange. When the sun was really young, it wasn't as bright as it is now. In fact, it was much fainter.

This is a problem because Earth has been around for a long time - billions of years, in fact. And if the sun was much fainter back then, it means that the Earth should have been too cold for life to exist. But the evidence shows that life did, in fact, exist on Earth back then.

So this paradox - this confusing problem - is called the faint young sun paradox. Scientists are trying to figure out why life survived on Earth when the sun was so much less bright than it is now. Some possible explanations are that the Earth had more greenhouse gases in its atmosphere, which helped keep it warm, or that the sun's brightness increased suddenly at some point in its history.

It's still a mystery, but scientists keep studying and learning more every day!