In the greenhouse effect, the gases of which our atmosphere is composed absorbs the thermal energy that the Earth radiates and reflects some of it downwards again, towards the Earth, effectively trapping heat inside the atmosphere. As light arrives from the sun, more and more thermal energy is trapped, increasing the temperature of the planet.
You've probably heard a lot about the greenhouse effect recently and the greenhouse effect is a is a very good thing for the earth if it wasn't for the greenhouse effect we would be on a freezing cold planet -20 degrees Celsius would be our average temperature. It's these greenhouse gases that keep us warm and allow life to be sustainable on earth, so the greenhouse effect is basically the ability of the earth to capture the energy that comes from the sun and prevent it all from just being reflected out to space.
If we didn't have these Greenhouse gases capturing this energy, we'd be a cold planet like, like Mars but if we have too many greenhouse gases we'd become a very, very hot planet like Venus which is got an average temperature well over 100 degrees Celsius the boiling point of water so let's look at how the Physics behind the greenhouse effect.
So the sun, when the sun is shinning on earth, most of the light coming to earth is in a form of visible light right? It appears white but we know its got all the colors of the rainbow in that spectrum and the wavelengths there are fairly short and they can get through all the molecules fairly quickly. Now the sun is very hot so these are stronger wavelengths and they're a little bit shorter okay but when the that energy is reflected away from the earth, it's reflected back as longer wavelengths the earth is cooler and it's producing these longer wavelengths out and those many of those are in the range of the infrared what we call heat, what we feel is heat so fortunately we don't loose all that heat energy because we have some gases in here that help capture that heat and make the earth the right temperature right average temperature about 13 degrees Celsius which is in the mid 50's a comfortable range.
So what are some of those gases? Well the main gas is actually water vapor, now this is part of the normal water cycle we're not producing excess water vapor all we do is condenses and it evaporates but there are others you've probably heard of carbon dioxide which is produced by plants and animals but its also produced by burning fossil fuels and putting excess carbon dioxide into the air. Another one is methane and Ozone again those are both oops Ozone, O z o n e Ozone, these are produced by humans what we call anthropogenic gases and the concern is as we produce more and more of these greenhouse gases we're actually going to be capturing too much of this infrared radiation and instead of it leaving the earth and having the earth maintain a stable temperature the earth's temperature will actually start to increase and scientists have noted a very small but significant increase in the earth's average temperature over the last century so that's what we do to what we call the greenhouse Effect.