# Is there such thing as the lowest point in outer space?

What would happen if you went out in outer space and all of a sudden, there was no gravitity? Suppose you fall down, what would be at the lowest point in the space? Is there such thing? Or, would you fall down forever?

You would not “fall down” in the normal sense. You would be subject to gravitational pull from nearby planets and stars. Depending on your initial position and velocity, you might end up falling into a planet or star. There is no specific point in the universe towards which all matter is falling into. In fact, on a macroscopic scale, we think that the universe is isotropic and homogeneous - i.e. it’s identical in every direciton and every position.

You wouldn’t fall without gravity. You’d kind of float. If someone pushed you in one direction, you’d keep going in that direction forever.

Gravity can’t go away. Even if all the mass in the observable universe were instantly turned into energy, gravity would remain the same. Mass and energy are two aspects of the same thing, or totally interchangable, not sure which.

You would, probably, be fried by all the radiation fairly quickly though.

Concepts of up, down, top, bottom which seems so intuitively obvious on the Earth’s surface have no real meaning in space.

I think I remember Mork saying that the way to get to his home planet of Ork involved going past Pluto and hanging an “up.”

I thought a person floated in space BECAUSE of the lack of gravity?

Gravity IS the force that makes an object “fall”.

If you go way out in the middle of intergalactic nowhere as least ballistics gets a lot easier: everything travels in a straight line.

But of course you can experience this right in your own neighborhood! For a few hundred million dollars go up in orbit and you get (nearly) the same thing. Everything in your spaceship is traveling along the same path and is immune (from you inside perspective) of the force of gravity.

Yes, but gravity doesn’t just ‘stop’ once you get a certain distance from Earth (or any other mass) - it gets less and less noticeable, perhaps to the point that it is no longer worth considering in calculations, but you’re never out of range of gravity.

The reason that astronauts appear to be in ‘zero G’ is that they are in orbit; effectively constantly falling toward the Earth at the same rate as the spaceship they are in. If you somehow managed to build a spaceship that could ‘hover’ at orbital height (but without actually moving in an orbital trajectory), there would be very noticeable gravity in your spaceship - not as much as on the ground far below, but still quite a bit.

(my ‘yes but’ was to t-keela)

Wouldn’t you have a Coriolis effect in orbit that would screw up your trajectories?

No I don’t think so. Coriolis effects arise from different tangential velocities in the same frame of reference. If I get quick dibbies on a non-rotating spaceship then there should be no Coriolis effect.

If you were in a void, with a force that kept accelerating you in a certain direction indefinitely, you’d never get to a “bottom”… you’d eventually find yourself back at the same point you started at, though.

It’s the tidal force that makes your spaceship a non-ideal reference frame.

Well that’s exactly what I mean. If you’re in an orbiting spaceship, and you’re moving in it, you and the ship have different tangential velocities, right? I guess the tidal force makes more sense, though.

Did I forget to mention that it was differentially smal spaceship?

Heck, I can get you zero G for 5\$. Follow me to the playground, we’re gonna climb to the top of the monkey bars, then you’re gonna close your eyes. Pay in advance.

Very true, I said lack of, meaning diminished. I realize as long as the universe contains objects w/ mass there will be some gravity. These forces work with and against each other. I might even dare say that the weak gravitational forces that are experienced in space may not actually be due to the lack of gravity. Rather it is from the equalization of opposing forces.

It is less confusing though, for most to say lack of gravity…isn’t this what we’ve been taught all these many years?

The lack of gravity, in response to part of the OP, would not result in your falling to the “bottom” of the universe.

The main point of the OP was questioning the idea about the “bottom” of the universe, or the “lowest point”, so to speak. to this I would respond…in simplistic terms, one could say there is a bottom. At least from your point of view, there is a top and bottom because there are “edges” to this expanding universe.

The problem though is, even if you could fall to the bottom…the universe is expanding faster than you can fall. So, in essence you could never hit bottom, so to speak.

Even though the universe is expanding, there is no center and no edges. Every point in space could legitimately consider itself the “center” of the universe.

Here’s the usual explanation/analogy. Imagine that you are a two-dimensional person. You live on a flat surface. The surface certainly seems flat in two-dimensional space. But it is curved in three dimensions, in fact, your universe is a giant sphere, like a balloon. No point on the surface of the sphere is the center, no point is an edge. If the balloon is inflated, every point on the balloon expands away from every other point. To an observer on the balloon, it appears that every point in the universe is expanding away from them, but that they are standing still. The surface of the balloon is finite, but it has no edge and no center.

Well, our universe could be considered similar, except a three-dimensional balloon surface, curved and expanding in a four dimensional space. Instead of a plane, our universe is a volume, flat in three dimensions but curved in four. If this makes no sense, then perhaps you should just remember that there is no edge. There is no top, there is no bottom. If you were in intergalactic space, you wouldn’t fall anywhere, you’d just keep coasting along at whatever speed you started with. You’d be gravitationally attracted to every body in the universe, but they would be so far away that the forces they exert on you would be nearly impossible to measure.

But if you were suddenly transported to space near our sun…say halfway between Earth and Mars…gravity would definately affect you. The graviational pull of the Sun would affect you tremendously. But what would happen to you? That would depend on your velocity when you arived at that point in space. If you were in a dead stop relative to the Sun, you’d simply slowly fall into the Sun. At first you’d fall slowly, but you’d get faster and faster and faster. If you were traveling at the same speed you were traveling on Earth, you’d go into orbit around the Sun. An orbit can be thought of as continously falling toward a body, but always missing. For a circular orbit, you have to have a sidways vector exactly equal to the force of gravity at your distance. So bodies close to the Sun have to have a high speed, or they will fall into the sun, like Mercury. Bodies far away from the Sun, like Pluto, have to have a very slow speed, since the Sun’s gravity is very weak out there. If Pluto’s speed were greater, it would fly away from the Sun, if it were slower it would fall towards the Sun. It would either go into a (more) elliptical orbit, hit the Sun, or fly off into interstellar space.

So by these arguments, if we consider three-dimensional space as analagous to a two-dimensional surface, then wouldn’t the event horizon of a black hole be the “lowest point” in the universe?

No Terrifel, because for a start an object falling into a black hole still has a way to fall (into the singularity). Using your method of detirming the lowest piont in the universe, I would say it was probably at the singularity of the most massive black hole in the universe, as approaching this point an object will lose more GPE than approaching any other point.