How is it that we engineer vehicles in space to travel for millions of miles at absurdly fast speeds? When we can only have vehicles on earth (jets) travel for thousands of miles at lower speeds? Why is the gap SO BIG?

Question

We can send vehicles/rovers to space and have them travel at very high speeds for millions of miles to other planets. But vehicles on earth (jets/planes) have significantly shorter range and speed. Why is this? ELI5

In: Physics

Answer 1

Wave your arms in the air quickly. Do it for about a minute. Now fill a bathtub or go to a pool. Do the same thing for a minute with your arms underwater. Did you feel that you used a lot more energy in the pool or tub?

Why do you think you feel more tired after doing the same thing in the pool? Did the water “resist” your arm movements more?

Air has resistance too and we mostly don’t notice it at the speeds humans can move unaided. However compared to space, air resistance in our atmosphere makes a huge difference to how fast we can make vehicles or objects travel.