how does a greenhouse work a science with bobert video short

Just what is a greenhouse? (greenhouse building) A greenhouse is a building that is built out of glass. Glass is used because it lets the visible rays of the sun to pass through which is then absorbed by plants and other colored or black surfaces inside the greenhouse. When visible light is absorbed it gets converted to heat. (movie Dr Smith) Have you ever touch a white and a black surface that has been out in the sun? The white surface reflects the visible rays. that ‘s why it looks so bright. The black surface absorbs all the sun’s visible rays converting all this energy to heat. This can be seen with Dr. Smith’s IR thermometer. These two objects have been out in the sun. The black one is A LOT hotter as measured by the IR thermometer. The table, plants, and other surfaces in a greenhouse absorb visible light during the day. The visible light is converted to heat and then emitted by the objects. However, the greenhouse is surrounded by glass and glass is an insulator! (animated arrows visible light through glass and heat squiggles trying to get out but blocked) Glass lets visible light through but blocks heat. (pinball sound) So heat builds up (pinball) inside a greenhouse due to the light transmission properties of glass.

A greenhouse is similar to how our atmosphere works. Our atmosphere is 78% nitrogen and 21% oxygen. What is strange is neither of these gases can block heat. Heat passes right through them. (model n2 and O2 and heat squiggle passes right through.) So that means the remaining 1% of our atmospheric gases must be doing all the work when it comes to blocking heat like a pinball machine. (? and squiggles get blocked!) In fact, these remaining gases are terrific at blocking heat! Heat blocking gases in our atmosphere are carbon dioxide, water vapor, methane, nitrous oxide, and ozone. Of these heat blocking gases, the EPA reports that it is mostly carbon dioxide (image).

(phet) This animation may help us see what is going on in our atmosphere when it comes to the greenhouse effect. The yellow dots are sunlight and the red dots are heat coming from Earth’s surface. Earth’s last ice age peaked about 18,000 years ago. Carbon dioxide levels were much lower then they are today, roughly 30% lower. so the pinball effect on heat from carbon dioxide didn’t occur as much as it does today. A lot of heat escaped our atmosphere 18,000 years ago. If we look at the animation set for today, we can see that the pinball effect on heat by carbon dioxide occurs much more often due to the higher concentration of carbon dioxide. In fact, today scientists believe each photon of heat released from Earth’s surface is blocked (pinball sound) at least once before finally escaping into space. That definitely was not the case 18,000 years ago.