 They say it all started with a big bang, and white noise on an old TV set helps to show that. That white noise reaches us in the same way that the heat causing global warming does. This heat comes from the greenhouse effect. Now what do the big bang and the greenhouse effect have in common? We'll talk about the link a little bit later, but let's just start with the greenhouse effect. The greenhouse effect is measured every day by instruments like these. And if we look at our nearest neighbor, we can see just what it's capable of. Venus has big, thick clouds so that less sunlight reaches its surface than reaches ours. But its atmosphere is about 95% carbon dioxide. This causes a super-powered greenhouse effect. At the surface, it's hot enough to melt lead. Now how can a simple gas like carbon dioxide be so powerful? The greenhouse effect works like this. We see the sun on a clear day because the gases in our sky are transparent. The sun's rays get to Earth's surface and they warm us up because light is a form of heat. This heat has to go somewhere or we just get hotter and hotter. Earth glows with infrared, a form of light that's invisible to the human eye. Greenhouse gases let through visible light from the sun, but they absorb the infrared from the Earth. They slow down its escape and they keep Earth warmer. We know how to slow down the escape of heat to keep ourselves warmer. It's called a blanket. Even though the blanket itself doesn't give off heat, we still put one on to keep warm. Now the infrared heat given off by Earth is invisible to the human eye. But we can see it with this infrared camera. Let's look at an example with a cup of cold water and a cup of hot water. If we look at them, we can't tell which one is hot. But the camera shows that hot water glows more brightly in the infrared than cold water. A similar thing happens in the atmosphere. Greenhouse gases are special, not just because they absorb infrared, but they also glow in the infrared. The glow from the Earth's surface goes upwards. Greenhouse gases absorb some of this heat and then they glow in every direction, including down towards us. This recycled heat is how the greenhouse effect warms us. We measure it every day here at the University of Reading Atmospheric Observatory. And this is a pergeometer. It has a special window that only allows infrared light through to be measured. Even during a cloudless night, it measures a constant warming greenhouse glow. Even though the greenhouse effect is an observed fact, there is a myth that claims it doesn't exist. This myth misinterprets a law of physics called the second law of thermodynamics. The second law says that even though heat moves in all directions, overall heat moves from hot to cold and not from cold to hot. The myth says that the greenhouse effect doesn't exist because it means heat going from the cooler sky to the warmer surface. But this is a misrepresentation. The greenhouse effect obeys the law. A square meter of Earth's surface sends about 500 watts upwards. So it works like a 500 watt heater. The greenhouse effect sends down about 330 watts of heat. So in total, 170 watts goes from the warmer surface to the cooler sky. Heat overall goes from hot to cold, but the greenhouse effect sends some back to warm us up. The myth misrepresents the second law of thermodynamics. Meanwhile, observatories measure the greenhouse effect every day all over the world. We know it's there. And this is where the Big Bang and Static on an old TV come in. Outer space is very cold. It's about 270 degrees Celsius below freezing. But a tiny part of the static on that TV screen is the remains of electronic noise from the Big Bang. This noise contains energy, so it is heat. And despite being unbelievably cold, some heat has flowed from the frigid outer space to a barmy living room. Now Earth sends a lot more heat into space than the other way round, so thermodynamics is safe. And even though we can't see it, we live under the faint glow of the Big Bang and the much brighter glow of the greenhouse effect. This keeps us much warmer than we'd otherwise be.