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Lesson 1 Energy Flow in Global Systems

  Conclusion

It starts with the sun.


© NASA, via Wikimedia Commons
D1.16 Net radiation budget of Earth
All energy on Earth originates with the sun. Once that energy reaches Earth, it can be absorbed by particles in the biosphere to be used in photosynthesis or converted into thermal energy or it can be reflected back into space. No matter what happens with the energy when it first reaches Earth, it is eventually re-emitted or reflected back into space. The amount of energy that reaches Earth is always equal to the amount of energy that is sent back into space.

The biosphere itself consists of all living things found on Earth as well as their environments. The biosphere can be split into the atmosphere, hydrosphere, and lithosphere. While we can classify different parts of the biosphere into those three parts, it is important to remember that all three parts of the biosphere are constantly interacting and mixing together. Parts of the hydrosphere are found in the lithosphere and in the atmosphere, and parts of the lithosphere can be found in the atmosphere and the hydrosphere.

In the next lesson, we will start to look at how solar energy is used to create climate and biomes within the biosphere.
D1.18 All parts of the biosphere interact

  Interactive Activity

Molecules and Light © PhET


This simulation will help you understand the absorption and reflection of solar radiation by different gases in the atmosphere. This simulation will focus on infrared radiation—the part of solar radiation that is converted to thermal energy.


  1. Click on the play icon to open the simulation. The simulation can also be found at https://phet.colorado.edu/sims/html/molecules-and-light/latest/molecules-and-light_en.html
  2. Make sure the flashlight is set to infrared (the rest should be greyed out) and carbon monoxide is highlighted.
  3. Set up an observation table in your notes similar to the one below.

    Gas Reflected Absorbed

  1. Turn on the flashlight by moving the slider to the right.
  2. Observe what happens to the particles of gas and the infrared light. What does it mean when the particles start to move?

    The particles have absorbed the infrared radiation and converted it to thermal energy. Remember, thermal energy is the kinetic energy of particles; the more the particles move, the hotter they are.
© pHet
D1.19 Flashlight
  1. What is happening when the infrared radiation changes direction?

    The infrared radiation is being reflected.
  2. Record carbon monoxide in your chart and check off if the radiation was reflected, absorbed, or both.
  3. Change the gas to nitrogen and observe what happens. Record your observations in your chart.
  4. Complete step 8 for each gas in the list.
  5. Please return to the top of this page and click on analysis to complete the analysis questions.
Here is a completed observation chart.

Gas Reflected Absorbed
carbon monoxide (CO) yes yes
nitrogen (N2)
no no
oxygen (O2)
no no
carbon dioxide (CO2)
yes yes
water (H2O)
yes yes
nitrogen dioxide (NO2)
yes yes
ozone (O3)
yes yes

  1. Which gases did not react to the infrared light?

    nitrogen and oxygen
  2. Why is this significant?

    Our atmosphere is mostly made up of nitrogen and oxygen. Since infrared radiation is the radiation that is converted to thermal energy, this shows that without clouds (water vapour), atmospheric dust, and other items or substances in the atmosphere, all the heat would reach Earth’s surface and all of the thermal energy emitted from Earth’s surface would be lost back to space. It also shows the importance of the other gases found in our atmosphere, even though they are present in very small amounts. These gases help to capture some of the infrared radiation coming in from space and being re-emitted by Earth, playing a big part in keeping Earth’s temperature stable.
  3. According to the net radiation budget, 48% of the incoming solar radiation is absorbed by Earth’s surface. Explain what this does to the particles that make up Earth and how this helps to keep Earth’s surface warm.

    You will use this answer in your Formative Assessment D1.