Have you ever thought about where the vegetables you eat are coming from when it is too cold to grow them outside? They might have been shipped from a different country to your town—or they may have been grown locally in a greenhouse. Greenhouses are large houselike structures that are usually made mostly of glass (or clear plastic). How can they protect plants from the cold? In this activity you will find out—and create some extra heat from the sun.


Plants cannot grow everywhere. Their environment has to provide the right conditions for them to survive. Specifically plants need water, air, sunlight and suitable temperatures. In winter months cold temperatures are often a limiting factor for plant growth. This is why the ancient Romans created artificial environments so that they could grow their vegetables all year. Today many vegetables, especially tomatoes, are grown in greenhouses, which cover the plants inside.


你有没有想过,当你吃的蔬菜太冷,不能在外面种植的时候? 它们可能是从一个陌生的国度运到你的城镇,又或者它们是在温室里种植的成果 温室是通常由玻璃(或透明塑料)制成的大型房屋式结构。 那么它们如何保护植物免受寒冷? 在这项活动中,你会发现并创造一些来自太阳的额外的热量。


植物不能生长在任意的地方,它们的生长环境需要给它们提供恰当的条件以供存活。 特别的是,植物需要水, 空气,阳光和适宜的温度。 在冬季,寒冷的温度往往是植物生长的限制因素。 这就是古罗马人创造人工环境的原因,这样他们就可以全年种植蔬菜。 今天很多蔬菜,尤其是西红柿, 生长在庇护着植物的温室里。


Greenhouses work based on a physical principle called “the greenhouse effect.” In a greenhouse sunlight—which is made up of different wavelengths, some of which are in the visible and infrared spectrum—shines through the transparent glass or plastic roof and walls. Only the light in the visible spectrum can penetrate into the greenhouse whereas incoming infrared light, which is also known as heat radiation, is blocked by the glass or plastic. Inside the greenhouse the visible light is absorbed by the plants and soil and is converted into heat, which is then emitted by the plants and soil in form of infrared radiation. Because that heat radiation is blocked by the glass, most of it cannot escape, and the temperatures inside the greenhouse will steadily increase. Even in the winter, temperatures in a greenhouse can be warm enough for vegetables to grow. Want to see for yourself? Take a thermometer and explore the greenhouse effect in this activity! How high do the temperatures get in your “greenhouse”?




Two small outdoor thermometers
Glass jar with lid, big enough to fit one thermometer
A sunny workplace (outdoor or indoor)
Timer or stopwatch


  • Find a work area that will have direct sunlight (no shadows) for at least 30 minutes.
  • Take both thermometers and place them next to each other in the sun. Make sure that no shadows are cast onto the thermometers throughout the activity.


  • Set your timer to five minutes and read the temperatures of both thermometers once the five minutes are over. How high is the temperature? Do both thermometers show about the same temperature?




  • 找一个至少有30分钟阳光直射(没有阴影)的工作区域。
  • 拿上两支温度计,然后把它们并排放在阳光下。保证在活动中没有阴影投到温度计上。


  • 倒计时五分钟,五分钟结束时,读取两支温度计上的温度。温度有多高?两支温度计显示的温度一样吗?
  • Put one of the thermometers inside the glass jar and close its lid. Place it next to the other thermometer again and make sure it is still fully exposed to the sun. How are the conditions inside the glass jar different from the conditions outside of it? What do you think will happen to the temperature inside the jar?
  • Let both thermometers sit in the sun for about 20 minutes, then read the temperature again. Did the temperatures change? How? Are the temperatures the same inside and outside the jar? If not, which thermometer shows the higher temperature?
  • For a better comparison calculate the temperature difference between the beginning and end of your test for each thermometer. (That is, the temperatures in the beginning versus those after 20 minutes). By how many degrees did the temperature change on each thermometer? Is the temperature difference higher inside or outside the jar?Can you explain your results?
  • Extra: Do you think your results will be similar when you place your thermometers in the shade? Repeat the activity but this time put both of the thermometers (inside and outside the glass jar) in a shady spot. Do you get the same results? How do your final temperatures after 20 minutes compare with your results in the sun?
  • Extra: Instead of just reading the temperatures in the beginning and at the end, make a time series and write down the temperatures every five minutes for about 20 to 30 minutes. How is the increase in temperature over time different inside the jar compared with outside? Which thermometer shows a faster temperature increase?
  • Extra: Does the greenhouse effect work with other materials besides glass? Instead of a glass jar, try one of the thermometers in other kinds of containers. Make sure the containers are transparent so the sunlight can shine through. Does plastic work as well as glass?
  • Extra: Have you heard about the greenhouse effect before in the context of climate change? Earth itself is similar to a greenhouse, which traps heat from the sun. Because of this we experience the warm temperatures that we have on our planet. Do some research to find out more about how this works. How is the greenhouse effect in a greenhouse related to Earth’s greenhouse effect?
  • 把一支温度计放进玻璃罐然后盖上盖子。 将它再次放在另一支温度计旁,并且保证它仍然完全暴露在阳光下。玻璃罐内部的条件与外界条件有什么不同?你觉得罐子里的温度会怎么样?
  • 把两支温度计放置于太阳下约二十分钟 ,然后再次读取温度。温度变化了吗?如何变化?罐子里面和外面的温度一样吗?如果不同,哪支温度计显示更高的温度?
  • 为了更好的比较,计算测试中每支温度计开始到结束之间的温差。(即开始时的温度对比二十分钟后的温度)每支温度计的温度变化了多少度?罐子里面还是外面的温差更高?你能解释你的结果吗?
  • 额外的:当你把温度计放在阴凉处时,你认为结果会相似吗?重复实验,但这次把两支温度计(玻璃罐里面和外面的)都放在阴凉的地方。你得到同样的结果吗?20分钟后的最终温度与你在太阳下测量的结果相比如何?
  • 额外的:不仅仅读取开始和结束时的温度,而是做一个时间序列,在大约20至30分钟里每隔五分钟记一次温度。这段时间玻璃罐里面和外面的温度升高有什么不同?哪支温度计显示更快的温度上升?
  • 额外的:除了玻璃之外,温室效应还能靠其他材料奏效吗?不用玻璃罐,而是在其他类型的容器中试一个温度计。确保容器是透明的以便于阳光能透过。塑料和玻璃效用一样吗?
  • 额外的:此前在气候变化的背景下你可曾听说过温室效应?地球本身就类似于温室,吸收来自太阳的热量。正因为如此,我们在地球上感受到温暖。做一些研究,以了解更多这方面的工作原理。温室中的温室效应与地球的温室效应有什么关联?

Observations and results

As long as both thermometers are exposed to the same conditions, they should show the same temperature. There may be some slight variations between different thermometers, but they should not differ more than one or two degrees. Once you place one thermometer inside the glass jar, you place it in an artificial environment. Inside the jar the heat that is generated from the sunlight energy is unable to escape—glass does not allow heat radiation to pass through. Because the heated air inside the jar is trapped, there is also no airflow possible. This means the warm air cannot mix with colder air to cool it down. As a result, the temperatures inside the glass jar should have continued to increase over time. The actual temperature depends on how sunny it was at your workplace.




After 20 minutes you should have observed that the temperature inside the glass jar was significantly higher than that outside the jar. Although the temperature also increases outside the jar, the thermal energy generated by the sunlight escapes through the air when not trapped. Also, cool air from the surroundings can mix with the hotter air around the unenclosed thermometer, which slows the temperature increase outside the jar. Finally, you might have noticed the temperatures inside the glass jar can get pretty high. To avoid this in a real glasshouse, temperatures are often controlled by means of ventilation or even cooling.