Hello Mr. Nye. Happy Tuesday. My name is Billy.
I’m a big fan and I have a question about climate change. If the photons from the sun
are trapped in our atmosphere by our greenhouse gases then how come those same greenhouse
gases don’t block photons from the sun from ever entering our atmosphere? Is there some
sort of weird cosmic one-way road sign? Thank you. Billy. Billy. Billy. You have chanced on like
the most important idea right now in climate science. When you say photons from the sun
come in through the atmosphere, that is absolutely true. And they go through out through the
atmosphere but not all of them get out at the same energy. Now here’s the strange thing
about light and electromagnetism. Now bare in mind we are humans trying to understand
nature and if we can’t get our heads around this it’s our problem. But basically, if you
do experiments on waves of lights or electricity, electromagnetic waves you will find waves.
If you do experiments on photons of light or electromagnetism you will find particles.
You can either detect particles or waves. So both of these ideas have helped us in physics
understand nature. So here’s what happens. Light from the sun comes in at wavelengths
that our eyes detect very well. It hits the earth and is reradiated, the energy is absorbed
by the atoms of soil, of bridges, of the ocean, of ice and reradiated or sent back out again
at a longer wavelength, it’s a little longer. And I don’t know if you know this but you
probably do, what we, you and I call heat is the same thing as light at a wavelength
longer than we see with our eyes. There are a lot of animals that see these wavelengths,
but that’s not our issue. You’ve seen it with night vision goggles, those cool images. So
light from the sun passes through the atmosphere; hits the earth; all these different materials
and is reradiated at a longer wavelength that carbon dioxide, methane and some other gases
hold in. The visible light at the faster wavelength goes through, the heat at the longer wavelength
does not go through to a limited extent, to a significant extent. And that’s how the earth
is warm enough for us to live. And because we put so much extra greenhouse gas via various
species in the atmosphere, the world is getting warmer faster than it’s ever gotten before.
It’s a great question Billy. That is the essence of this. Passes through at one wavelength,
starts to go back out at a longer wavelength that is held in by the greenhouse gases. This
is the fundamental idea in climate science. Carry-on!