Layers of Atmosphere II and Altitudes

• The density of molecules is so low in the thermosphere that one gas molecule can go about 1 km before it collides with another molecule.
• The thermosphere is above the mesosphere.
• The mesosphere occasionally has clouds called noctilucent clouds.
• Aurora: A solar flare as a violent explosion of magnetic energy on the sun.
• In the aurora, the charged particles energize oxygen and nitrogen gas molecules, causing them to light up. Each gas emits a particular color of light.
• The exosphere is above the thermosphere, and it is the outermost layer of our atmosphere.
• There is no real outer limit to the exosphere, the outermost layer of the atmosphere; the gas molecules are so scarce that there are no more.
• Density: The mass of a substance per unit volume. The pull of gravity is stronger closer to the centre, at sea level. Air is denser at sea level, where the gravitational pull is greater.
• Vigorous: characterized by forceful and energetic action or activity
• Gas molecules can move freely, and if they are uncontained, as they are in the atmosphere, they can take up more or less space.
• When gas molecules are cool, they are sluggish and do not take up as much space. With the same number of molecules in less space, both air density and air pressure are higher.
• When gas molecules are warm, they move vigorously and take up more space. Air density and air pressure are lower.
• Warmer, lighter air is more buoyant than the cooler air above it, so it rises. The cooler air then sinks, because it is denser than the air beneath it.
• A change in temperature with distance is called a temperature gradient