Did UFOs attack fighter planes in June of 1969? Find out on this Moment of Science.
The theory behind this legend goes like this: Daytime is bright, due to the sun. If you view a sunless piece of sky through a long tunnel, there should be no way for the sunlight to get into your eyes. Therefore, you should see stars.
Now, at sunset, the lowest mile or so of the atmosphere is filled with things like vehicle exhaust, dust, smoke, and water vapor, and all these pollutants scatter light.
If you look at the horizon at sunset–exactly as the last sliver of sun disappears–you might see a flash of brilliant green blaze across the sky.
In his book Cosmos, the late scientist Carl Sagan talks about the way in which the earth is regularly struck by material from outer space. These collisions with space debris can be minor–as in a shooting star on a summer night–or amazingly destructive, as in the collision that probably killed off the dinosaurs. Thankfully, the [...]
To really behold the stars these days, you have to travel far from cities and towns to escape urban glow. The magnificent sight of the Milky Way, for example, can now only be seen in rural areas. But why do we shine light up into the sky in the first place? We need light shining down on streets and walkways–not up into the sky!
You can see this more easily by imagining what would happen if the earth were flat. The moon would still travel in a horizontal line above the ground; but because it’s also falling, it would come closer and closer to the flat earth until it collided.