As I mentioned in my post of two weeks ago, I said I had a lot of questions to ask, and I thought I’d ask a few of them today. Instead of a post asking inane questions about a whole bunch of different items, this time I thought I’d throw out a question or two about moving around in outer space. What is movement anyway? How do you define movement? Let’s take a look at movement in its simplest form. Suppose you’re in outer space with nothing around, no stars, no planets, no galaxies, no gas or dust that could condense to form something. No stray electrons or protons whirling around, no graviton particles, no Higgs bosons, not even a neutrino zipping by at the speed of . . . well, at whatever speed neutrinos zip by at. Nothing at all. Totally and completely and absolutely bare of other material. Just you, in a space suit, well protected against the total vacuum of outer space. (And in this case, I mean total.) How you got there isn’t the question, and we’ll disregard that for the present. You’re all alone.
Now, how do you know if you’re moving or not? What information do you have that tells you if you are moving? Are you moving straight ahead? Or to your left? Or right? Up? Down? Is there even an “up” or “down” at all? Seems to me you can’t tell. There’s no way to know if you’re moving or stationary. In fact, it doesn’t even matter. If there is nothing around, there is no movement. Clearly, movement is relative. You move only in relation to other objects around you. If there is nothing around, you’re not moving. Outer space is so huge and immense, you could be moving and never go anywhere. There is no “edge” to outer space. You can’t stop at the edge and turn around.
But suppose you had a rocket engine strapped to your back. Just a small rocket, nothing too big. We don’t want you to get injured here, in outer space with no way to get medical attention. Let’s say you start that rocket engine. How do you know if you’re moving? In this case, I assume you would feel the acceleration produced by the engine. But if you turn that rocket engine off, it seems to me you will feel that you’ve stopped. Dead. Cold. Are you still moving? Did you accelerate up to nothingness? The engine speeded you up, but in the absence of other objects, you wouldn’t know if you’re still moving. Some rocket.
In another scenario, suppose you had two small rockets that you could hold in each hand. You hold them at arm’s length, one pointed forward, one pointed backward, and ignite them. That would make you spin in place. At least you would spin if you were here on Earth. The real question I have is, would you feel any spin? Would you get dizzy? If you turned the rockets off, how would you know if you were still spinning? Would you still feel centrifugal force? How do you spin if there are no other objects around? I’m not sure myself. What do you think?