Why do sunsets look red?

During the evening, when the sun is near the horizon we may see a beautiful sunset.  The reds and oranges of a sunset are caused by the filtering action of the sky.

Sunlight, as we know, is made of many colors.  We can see the colors that make up sunlight when we look at a rainbow.  As sunlight passes through the atmosphere, the different colors are scattered by the air.

During the day, when the sun is directly overhead, its rays do not have to travel through as much of the atmosphere to reach the earth.  The sunlight is scattered in such a way that we see more of the blue rays.  But at sunset, when the sun is low in the sky, the light rays must travel through much more of the earth’s atmosphere to reach the viewer.

As a result, the shorter blue rays are soon scattered out and we can see more of the longer orange and red rays of sunlight – and we have a reddish sunset.  The red color of sunrise is caused the same way. – Dick Rogers

How does a blimp stay in the air?

A blimp is an airtight bag that is able to rise in the air because it is filled with light gases.  A blimp is a small, balloon-like airship.  Unlike the heavier-than-air airplane, the blimp remains aloft because it is lighter than air.  

It needs only small motors to push it forward.  Blimps are descendants of the simple balloon. The blimp's lift comes from a lighter-than air gas that raises the blimp in the same way a balloon is lifted.

A balloon rises because the gas inside the balloon is much lighter than the air round it, and so it floats in the atmosphere, in much the same way a ship floats on water.  The gas inside the blimp expands and fills out the blimp.  Its gasbag has no framework inside, and collapses when the gas is taken out.

Some airships, such as the dirigible, have an inside framework that supports the sides, and do not depend on the pressure of the lifting gas to maintain their shape.  During World War II, blimps protected ships by spotting enemy submarines.  

They were also used for observation, photographing enemy positions and for rescues at sea and on land.  Today, blimps with signs painted on their sides are used mostly for advertising and sightseeing. – Dick Rogers