Spacechem random oxides1/7/2024 But once the tube is filled with carbon dioxide, the infrared image of the flame disappears, because the CO2 in the tube absorbs and scatters the heat from the candle in all directions, and therefore blurs out the image of the candle. When the tube is filled with ambient air, the camera picks up the infrared heat from the candle clearly. Here’s a video of a similar experiment:Ī more logistically challenging experiment that Smerdon recommends involves putting an infrared camera and a candle at opposite ends of a closed tube. You’ll also want to make sure that you use the same style of bottle for each, and that both bottles receive the same amount of light from the lamp. He recommends checking the bottle temperatures with a no-touch infrared thermometer. “If you expose them both to a heat lamp, the CO2 bottle will warm up much more than the bottle with just ambient air,” he says. How can I see for myself that CO2 absorbs heat?Īs an experiment that can be done in the home or the classroom, Smerdon recommends filling one soda bottle with CO2 (perhaps from a soda machine) and filling a second bottle with ambient air. That means they can absorb a wider range of wavelengths - including infrared waves. But greenhouse gases like CO2 and methane are made up of three or more atoms, which gives them a larger variety of ways to stretch and bend and twist. Smerdon says that the reason why some molecules absorb infrared waves and some don’t “depends on their geometry and their composition.” He explained that oxygen and nitrogen molecules are simple - they’re each made up of only two atoms of the same element - which narrows their movements and the variety of wavelengths they can interact with. Those ranges don’t overlap, so to oxygen and nitrogen, it’s as if the infrared waves don’t even exist they let the waves (and heat) pass freely through the atmosphere.īy measuring the wavelengths of infrared radiation that reaches the surface, scientists know that carbon dioxide, ozone, and methane are significantly contributing to rising global temperatures. For example, oxygen and nitrogen absorb energy that has tightly packed wavelengths of around 200 nanometers or less, whereas infrared energy travels at wider and lazier wavelengths of 700 to 1,000,000 nanometers. That’s because molecules are picky about the range of wavelengths that they interact with, Smerdon explained. Oxygen and nitrogen don’t interfere with infrared waves in the atmosphere. (Hold your hand over a dark rock on a warm sunny day and you can feel this phenomenon for yourself.) These infrared waves travel up into the atmosphere and will escape back into space if unimpeded. When sunlight reaches Earth, the surface absorbs some of the light’s energy and reradiates it as infrared waves, which we feel as heat. Credit: A loose necktie on Wikimedia Commons Greenhouse gases like carbon dioxide and methane absorb the infrared energy, re-emitting some of it back toward Earth and some of it out into space. Simplified diagram showing how Earth transforms sunlight into infrared energy.
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