Scientists do experiments here on Earth to better understand the physics of distant worlds. We’re going
to simulate the different atmospheres and take data based on the model we use.

Each planet has its own unique atmospheric conditions. Mars and Mercury have very thin atmospheres, while Earth has a decent atmosphere (as least, we like to think so). Venus’s atmosphere is so thick and dense (92 times that of the Earth’s) that it heats up the planet so it’s the hottest rock around. Jupiter and Saturn are so gaseous that it’s hard to tell where the atmosphere ends and the planet starts, so scientists define the layers based on the density and temperature changes of the gases. Uranus and Neptune are called ice giants because of the amounts of ice in their atmospheres.


  • 4 thermometers
  • 3 jars or water bottles
  • Plastic wrap or clear plastic baggie
  • Wax paper
  • Stopwatch
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5 Responses to “Atmospheres”
  1. Aurora says:

    Great questions!

    1. Substances are USUALLY more dense the colder they become. Water is the most dense at 4 deg C (otherwise ice would sink and that’s a problem if you’re a glacier), not zero.

    Venus’ atmospheric pressure is 90atm, and the Earth is only 1 atm, so that’s a big difference. There’s a lot more pressure in the atm on Venus than on the Earth.

    Venus is also the hottest planet. Sunlight passes through the cloud layers and gets trapped by that thick atmosphere, so the heat builds up to really high temperatures.

    2. Temp and pressure are related, but they are also two different things. Did you get to the experiment about the ping pong balls representing the energy of the molecules? Its in the Ideal Gas section of the High School level in Chemistry.

    Think of a room full of ping pong balls bouncing all around on their own off the floor, ceiling and walls. Now make them bounce around twice as fast (raise the temperature) – what change does the wall feel? More hits per second, right? That’s pressure. As temperature increases with gases, the pressure will also increase. If you make the room smaller and hold the temperature constant, now the balls hit the walls more frequently again, making the pressure and temperature go up with a volume decrease.

    You can independently change one (temperature, pressure, and volume) and watch how they affect the others.

    If heat rises, why are mountaintops usually cold? The top floor of a house is usually warmer than the downstairs, right?

    As air rises, the pressure decreases, which lowers the temperature. As warm air rises, it cools off due to lower pressure. Also down near the surface of the earth, heat gets trapped by an insulating layer of air, and the higher up you go, the atmosphere loses heat faster than it is warmed by the sun (or ground) so it also gets colder.

    Hope this helps!


  2. AmyCrafton says:

    Question 1: Cold air/liquid is more dense and sinks because the molecules are closer together. Warm air/liquid rises because the molecules are further apart thus less dense. Is this correct? It is also my understanding that because Venus’s atmosphere is more dense it is one of the hottest planets. Does this information contradict my previous statement?

    Question 2: Venus Atmosphere is Dense. I know from experience that a thicker i.e denser blanket retains more heat. Cold air is also dense, yet it is cold. Why is this?

    Thank you.
    Amy, Avery and Julia C

  3. Danielle Goodnight says:

    Why are the “Lesson Sections” in the upper right of this screen titled “Astronomy…” when this page is “Atmospheres”?

  4. Aurora says:

    What specifically about your experiment didn’t work? What did you expect to happen, and what actually happen/didn’t happen? (I am not understanding a temperature reading of “H”.) It’s a little hard to troubleshoot without more information since I’m not right there with you. Tell me everything!!

  5. Yesenia Valverde says:

    Hi Aurora,
    My experiment didn’t work. We are experiencing a heat wave. My Thermometers all read H’. Any ideas on how to get a better reading while we are in a heatwave?

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