Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

Which layer of the atmosphere extends farthest into space?

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere

The correct answer is: Thermosphere

The thermosphere is the layer of the atmosphere that extends farthest into space. This layer begins above the mesosphere and can reach altitudes of up to 600 kilometers (about 370 miles) or more, transitioning into the exosphere, which is often considered the outermost layer of Earth's atmosphere. The thermosphere is characterized by a significant increase in temperature due to the absorption of high-energy solar radiation, resulting in temperatures that can soar above 2,500 degrees Celsius (4,500 degrees Fahrenheit). However, this temperature is not felt in the same way as we experience it at lower altitudes, because the air is extremely thin at those heights and does not contain enough particles to conduct heat effectively. Understanding the structure of the atmosphere helps in various fields, from meteorology to space exploration, where knowledge about different layers and their properties is crucial. The other layers, such as the troposphere, stratosphere, and mesosphere, are located below the thermosphere and do not extend as high into space.