That's called the "Cosmic Microwave Background". (CMB)
It was discovered in 1965, and its discoverers were awarded
the Nobel Prize in Physics in 1978.
Yes. Even greater. Air resistance or drag becomes harder the faster an object goes. This is why when cars reach their max speed they don't accelerate as fast, because they are pushing harder against the wind. If I take a tennis ball and shoot it down a bottomless pit, a 400 kph, the drag will slow the ball down till it reaches terminal velocity.
"The total distance traveled divided by the time it takes to travel the distance"
That's actually a pretty good definition of average speed. <em>(A)</em>
