Avi Loeb

Well, that's the risk that we pose to ourselves.

It's sort of like a self-inflicted wound.

We can shoot ourselves in the foot if we use nuclear weapons.

But we could also be impacted by our cosmic power

and the dinosaurs obviously realized that after a giant rock.

There could be exploding stars that could affect the earth.

I also wrote a paper last year about the fact that the solar system was presumably a few million years ago was passing through a very dense cloud of gas.

And that cloud of gas compressed

The solar wind, you know, the solar wind is flowing out of the sun.

There is an outflow, and it meets the ambient medium, the interstellar medium, at a distance that is about 100 times the Earth-Sun separation.

That's where Voyager is.

So Voyager just crossed that boundary recently.

And then...

However, if we are to cross through a very dense cloud of gas, that region where the solar wind is confined by the ambient medium is...

will shrink to a scale smaller than the orbit of the earth around the sun.

And then we will not be protected as much as we are right now from energetic particles.

So a few million years ago, we calculated there could have been a situation where we pass through a dense cloud of gas and that compressed the solar wind and we lost protection on earth.

Another interesting paper that I just published a few months ago had to do with a star that is seen passing by, and we show that this particular star may have passed very close, I mean, within a thousand times the Earth-Sun separation, and in that case, it could have sent

comets that collided with Earth at a much higher rate than usual.

So that could explain why a few million years ago, there was a change in the climate on Earth.