This is by no means correct in any way. I do consider it to be a "real" science question though. It's simply the questions of someone who can't sleep at night. If anyone knows of an existing theory similar to this or knows of material that's relevant (bonus points for video) then feel free to post it.

The main question is this: If a rubber ducky displaces water in a full fish tank (overflow), do we displace matter / space / whatever as well? Initially, I would say no simply because we are already in the universe so far as we know. If a rubber ducky is already in a fish tank, then moving it around shouldn't really displace more water other than moving the water around (no overflow).

So, allow me to look at this another way. You have a fish tank full of water. You empty every drop of water into a bunch of water bottles. Initially the water bottles were full of air. As you add the water, air is displaced from the water bottle and in put into the fish tank (in a closed system). In the end, you 'basically' have a fish tank full of air and several water bottles full of water.

Take that a step further. An astronaut fills a tank full of air on earth. He goes into space and we now have this little 'bubble' in the vacuum of space. His suit and the tank took air from earth, so what would fill the gap? Does the atmosphere deflate ever so slightly whenever we go into space?

Take that yet another step further. You have a water bottle full of water. You tilt it upside-down and release about 100ml of water. Water comes out of the bottle and into our fish tank. Air from the fish tank is put back into the water bottle. So, if we go back to our astronaut, he goes out into space taking some air from earth with him. The atmosphere deflates ever so slightly and space / matter from the other end of the universe is displaced ever so slightly???!?

So basically, do we displace space / matter within the entire universe just by moving?
Keep in mind I realize that sounds absolutely bonkers, I'm not trying to justify this theory. I'm trying to explain my confusion and get someone to explain why this isn't the case.

...An astronaut fills a tank full of air on earth. He goes into space and we now have this little 'bubble' in the vacuum of space. His suit and the tank took air from earth, so what would fill the gap? Does the atmosphere deflate ever so slightly whenever we go into space?

Yes. If you remove a given mass (a tank full of air, yourself, and your rocketship) from the planet to outside of it's gravity well, the planet will be left that much lighter.

Nothing would be 'displaced' by your arrival in space because space is a near-perfect vacuum with a density of something like 1 hydrogen atom per cubic meter. The force of Earth's gravity and magnetosphere are what keep the atmosphere from sloughing off to be agglomerated into other planets, or of they weren't there, being blasted out into interstellar space by the solar wind.

If you're interested in the physics of vacuums and plenums you should check out things like phenomena such as zero point energy and the Casimir effect. The quantum scale is where the really weird stuff happens.

when matter is displaced it moves through space. What do you mean by displacing space?

Well modern physics dictates that the force of gravity actually warps space, which is why planets fall into rotation around stars, and moons around planets. So every piece of matter warps space to some degree, whether it's relevant or not is another story.

As for the OP's last question, well yes and no. Not in the sense that dropping a stone into bucket of water displaces the water, but yes in the sense that our bodies have their own gravitational force, however slight it may be, and that force does in fact warp space around us a very, very small amount. When you drop a stone into a bucket of water, the stone occupies space that cannot be filled with water, so the volume of the stone is the volume of water displaced. But it is not the volume of our bodies that warps space, it's the force of gravity. So if we had a very, very small object with a very, very large mass, we'd end up with a huge warping of space, even though the object itself is small.

Nobody really knows what space is but it is not displaced the same way air or water is. When you move about in air or water the fluid moves because your volume cannot occupy the same area as the fluid. Space does not behave this way.

Put another way: air and water are both atomic matter. Space is not. The geometry of space/time is distorted by mass like BlackSun says but space itself is not displaced by a moving atomic volume like you. Space does not behave like atomic matter.

The question of just what space is and how mass distorts it is at the cutting edge of physics at the moment. There are tons of competing theories but no good data. All we know about space is that it is slightly energetic, it is distorted by mass, and that it is growing.

there is no net gain or loss of energy in the system, ergo energy cannot be created or destroyed, so there is no displacement in one sense

in the other sense to convert energy from one form to another does cause a type of displacement
there can be mass displacement, energetic displacement and temporal displacement among others.

Temporal displacement? Do you mean how gravity slows down time, or something else?



(Whoops, didn't notice this is kind of a zombie thread.)

If the ducky is separate from the water and introduced to it, displacement occurs, but what if the ducky is not distinct from the water?

Temporal displacement, I mean that potential can be mass, energy or space-time and be interconverted. Cavitation is an example of time-space displacement caused by energy and matter transition.

The presence of mass & its movement of any kind creates subtle ripples in the curvature of space. So I would say yes, space is "displaced". How it's displaced is one of the biggest questions of science as has been said. But it's not classical displacement like particulate mass as said. If you go to space with that bottle, for one the earth loses mass equal to your weight.

But it's not correct to say anything is "lost" or "gained" or "displaced". All that's happened is that the energy density of space has moved from one concentrated glob (you on earth) to one massive glob (Earth) and one small glob (you + bottle). Space and matter are fundamentally connected anyway and we're still questioning how so.

One important connection of relativity is that a mass undergoing acceleration is equivalent to a heavier inert mass; that is to say acceleration is gravity in some specific way. This all basically suggests that the energy density/distribution of space is what we should be looking at.


"So basically, do we displace space / matter within the entire universe just by moving?"

Yes, because to accelerate in any direction you have to displace mass-energy in the opposite direction. A rocket thruster or a solar sail are direct examples. With wheeled vehicles, this isn't as obvious but the energy displacement occurs as friction/heat where the tires meet the road.