“On the Heat in the Sun’s Rays”
Eunice Foote, “On the Heat in the Sun’s Rays,” 1856. The American Journal of Science and Arts via Google Books.
Document Text |
Summary |
| Circumstances affecting the Heat of the Sun’s Rays by Eunice Foote | |
| My investigations have had for their object to determine the different circumstances the affect the thermal action of the rays of light that proceed from the sun. | I am investigating how different air qualities affect the heat of the sun’s rays. |
| Several results have been obtained.
First. The action increases with the density of the air. And is diminished as it becomes more rarified. The experiments were made with an air-pump and two cylindrical receivers of the same size, about four inches in diameter and thirty in length. In each were placed two thermometers, and the air was exhausted from one and condensed in the other. After both had acquired the same temperature they were placed in the sun, side by side, and while the action of the sun’s rays rose to 110 in the condensed tube, it attained only 88 in the other. I had no means at hand of measuring the degree of condensation or rarefaction. The observations taken once in two or three minutes, were as follows: [SEE GRAPH IN ORIGINAL] |
I have made several discoveries. First: air density makes the temperature rise. As the air becomes less dense, the temperature cools.
To run my experiment I used an air pump attached to two tubes. Each tube had a thermometer inside. I used the pump to make the air in one tube more dense than the other. I made sure both tubes were the same temperature, and then I placed them in the sun. The temperature rose to 110 degrees in the tube with the dense air. It only reached 88 degrees in the other tube. There was no tool for measuring exactly how dense the air was in each tube. I checked the thermometers every two to three minutes, and recorded the following: [SEE GRAPH IN ORIGINAL] |
| This circumstance must affect the power of the sun’s rays in different places, and contribute to produce their feeble actions on the summits of lofty mountains.
Secondly. The action of the sun’s rays was found to be greater in moist than dry air. In one of the receivers the air was saturated with moisture-in the other it was dried by the use of chloride of calcium. Both were placed in the sun as before and the result was as follows: [SEE GRAPH IN ORIGINAL] |
This shows that air conditions must affect the temperature of the sun’s rays in different parts of the world. This is why the sun feels so weak on the top of high mountains.
Second, I found that the amount of moisture in the air raised the temperature. I filled one tube with moist air and one tube with dry air. I placed both in the sun and this is what I discovered: [SEE GRAPH IN ORIGINAL] |
| The high temperature of moist air has frequently been observed. Who has not experienced the burning heat of the sun that precedes a summer’s shower? The isothermal lines will, I think, be found to be much affected by the different degrees of moisture in different places.
Thirdly. The highest effect of the sun’s rays I have found to be in carbonic acid gas. One of the receivers was filled with it, the other with common air, and the result was as follows: [SEE GRAPH IN ORIGINAL] |
Many people have experienced that moist air feels hotter. This means that areas of the earth with moist air will have higher temperatures.
Third, I discovered that the sun rays are strongest when they pass through carbon gas. I filled one tube with carbon gas and with plain air and this was the outcome: [SEE GRAPH IN ORIGINAL] |
| The receiver containing the gas became itself much heated-very sensibly more so than the other-and on being removed, it was many times as long in cooling.
An atmosphere of that gas would give to our earth a high temperature; and if as some suppose, at one period of its history the air had mixed with it a larger proportion than at present, an increased temperature from its own action as well as from increased weight must have necessarily resulted. On comparing the sun’s heat in different gases, I found it to be in hydrogen gas, 104; in common air, 106; in oxygen gas, 108; and in carbonic acid gas, 125. |
The tube with the gas in it became hotter and took longer to cool than the one with plain air in it. If our atmosphere were full of carbon gas, the earth would get much hotter. If the atmosphere fills with this gas, we will see the average temperatures on earth rise.
I ran the experiment with hydrogen, common air, oxygen, and carbon. Each gave a different result. |
Eunice Foote, “On the Heat in the Sun’s Rays,” 1856. The American Journal of Science and Arts via Google Books.
Background
To produce the steam that powered the new technologies of the Industrial Revolution people burned fossil fuels at a rate unprecedented in human history. The short term effects of this increase were obvious. Cities were covered in a layer of soot. Air quality around factories was so poor that people developed deadly lung diseases. But it was not until 1856 that scientist Eunice Foote proved that burning fossil fuels could cause catastrophic damage to the entire world.
About the Document
Amateur scientist Eunice Foot conducted some of the first experiments to determine how different gases affected air temperature. She found that extra carbon dioxide caused a sharp increase in air temperatures. She realized that if the carbon dioxide level in Earth’s atmosphere grew too high, it would cause a sharp increase in the planet’s temperatures. In short, she accurately predicted the current climate crisis 100 years before the wider public began to take it seriously.
But at the time, women were not welcome in public speaking forums. Women who did speak publicly faced ridicule and sometimes violence. Because of this, Eunice decided not to present her findings to the scientific community herself. She allowed imminent scientist Joseph Henry to present on her behalf at the 1856 Annual Meeting of the American Association for the Advancement of Science. Joseph shared that Eunice was the person who ran the experiments, but his presentation was not recorded in the conference records. Later that year, Eunice published her findings in The American Journal of Science and Arts under her own name. But even this did not bring her the recognition she deserved. When John Tyndall published his own findings demonstrating why gases like carbon dioxide raised atmospheric temperatures, he did not credit Eunice as one of the scientists who laid the foundation for his work.
Vocabulary
- Industrial Revolution: The era of American history marked by the rise of factories and mechanical inventions that transformed daily life.
- fossil fuel: Fuels that occur naturally, like coal or gas.
- atmosphere: The layer of gases that surround Earth.
Discussion Questions
- What conclusion does Eunice Foote draw in this article? Why is this moment in scientific history important?
- What hurdles did Eunice face as a woman scientist?
- Why is it important to acknowledge the forgotten contributions of women scientists?
Suggested Activities
- The most remarkable thing about this story is that it proves the scientific community has known about the dangers of carbon dioxide emissions for 170 years. Ask students to research the current status of climate change initiatives in the U.S. and then write a short essay imagining how Eunice Foote would feel about the current state of affairs.
- Eunice Foote and her husband both signed the Declaration of Rights and Sentiments in 1848. After analyzing this source, ask students to read the Declaration and then discuss why Eunice might have supported the fight for women’s equality.
For more women and STEM in the Industrial Revolution, see First Lady of American Astronomy and Life Story: Elizabeth Cogley.
Themes
SCIENCE, TECHNOLOGY, AND MEDICINE
