Let's talk about the rarity of our Earth and how special it is.
How about how it is protected from the dangers of the space, unlike other celestial objects
– the meteors, asteroids, and others.
Although space is full of them, and our Earth can get hit, this happens very rarely, especially
on levels that could be dangerous.
We only hear news of close calls.
Can you tell us about the way our planet is protected?
The atmosphere, the Van Allen Belt, does our solar system have a protection too?
Are we located in a protected part of the galaxy?
A very interesting topic is the situation, the placement of the Earth in the context
that it is.
So the Earth is part of our solar system, the solar system is part of our galaxy, and we
can ask the question, is the Earth occupying a special place?
Is it well protected, for example?
The first thing to point out is that in our galaxy, at the galactic scale, there are very
strong physical effects, for example supernovae, that are occurring.
When a supernova occurs, a massive star explodes, and its energy output briefly matches the energy
output of the entire galaxy.
Now the entire galaxy is 100 billion stars, so it's 100 billion times its normal energy
output.
As such, when that occurs, for many, many light years around it, any possibility of life would
be sterilized.
There would be no possibility of life.
So, and even much farther distances, as these supernovae are going off, there is these galactic
cosmic rays that are a source of potential harm to the Earth.
But our solar system has essentially a magnetic field that is protecting it.
And in particular, there is a solar wind, which is this radiation from the sun, that modulates
or moderates the effect of these galactic cosmic rays.
The solar wind, in that sense, is helpful.
But in another sense, the same thing that the processes that give us the solar wind give
us sometimes dangerous events, like coronal mass ejections, where the sun occasionally has
a big output, then how do we get protected from that?
It turns out, if you look at Venus, Venus is getting, was essentially destroyed as a
habitable planet by the sterilization or stripping of the hydrogen from its atmosphere.
And so all that is now there is carbon dioxide.
At the temperature in the surface of Venus, it's much hotter than your ordinary oven.
So that's why nobody sends spacecraft there, because your electronics will melt after a little
while in Venus.
It's very difficult.
Earth is not like that.
What's going on?
Earth has a magnetosphere.
There is a molten liquid iron core that's spinning inside the Earth.
And the dynamo process essentially generates a magnetic field.
And the magnetic field then modulates and moderates the effect of solar radiation, the solar particle
radiation.
So the Earth is, on the one hand, protected from galactic cosmic rays by the sun, and then
it is protected from the sun by its own magnetosphere.
And so there is this layer after layer of protection for the Earth, just from the standpoint
of particle radiation.
There's also very interesting things going on in this that I could go on, but I think this
part expresses just the levels of protection that the Earth has.