Question 1 of 15
In which layer does nearly all weather occur?
Why: The troposphere holds most of the atmosphere's water vapour and virtually all clouds and storms.
Question 2 of 15
Which layer contains the ozone layer?
Why: Stratospheric ozone absorbs most incoming ultraviolet radiation, which is what warms the layer.
Question 3 of 15
What is unusual about temperature in the stratosphere?
Why: Ozone heating creates a temperature inversion, which makes the stratosphere very stable and smooth for flying.
Question 4 of 15
Where do most meteors burn up?
Why: The mesosphere is dense enough to create friction heating but high enough that few meteors survive it.
Question 5 of 15
Which is the coldest layer of the atmosphere?
Why: The mesopause at the top of the mesosphere can reach about minus 90 degrees Celsius.
Question 6 of 15
In which layer do auroras occur?
Why: Charged particles excite gases in the thermosphere, producing the glowing curtains of the aurora.
Question 7 of 15
What is the boundary at the top of the troposphere called?
Why: Thunderstorm anvils flatten out at the tropopause because the stable air above resists further rising.
Question 8 of 15
Roughly what fraction of the atmosphere's mass sits in the troposphere?
Why: Around 75 to 80 percent of atmospheric mass is in the lowest layer, compressed by gravity.
Question 9 of 15
What is Earth's atmosphere mostly made of?
Why: Nitrogen makes up about 78 percent and oxygen about 21 percent of dry air.
Question 10 of 15
Where is the jet stream found?
Why: Jet streams flow near the tropopause, which is why airliners cruise at that altitude to use or avoid them.
Question 11 of 15
What are noctilucent clouds?
Why: These rare electric-blue clouds form near 50 miles up and glow after sunset when lit from below.
Question 12 of 15
At what altitude is the Karman line, often used as the edge of space?
Why: The Karman line sits at 100 kilometres, roughly 62 miles, near the top of the thermosphere's lower reaches.
Question 13 of 15
Why can the thermosphere be thousands of degrees yet feel cold?
Why: Individual molecules move very fast, but there are far too few of them to warm an object.
Question 14 of 15
Which layer is the outermost?
Why: The exosphere fades gradually into space, with atoms so sparse they rarely collide.
Question 15 of 15
Why does air pressure fall with altitude?
Why: Pressure at any level reflects the weight of all the air stacked above it, so it drops as you climb.