I believe it's you who are missing the point. Acceleration is irrelevant, it's how it's transmitted that matters. You feel gravity because the ground prevents you from falling exerting an opposite force, that is transmitted mechanically along your body.

There is no difference between free falling and no gravity except in monster gravitational fields like the one close to an event horizon where differential gravity (tide) could torn you apart. In any other situation you can safely assume that all the points in an object are pulled uniformly.

I'm also not asking about what our brains are conditioned to feel. I am simply asking - is the constant acceleration of orbit fundamentally different than no acceleration, even if both would feel the same?

No-one has answered that in a compelling way.

Because to be clear - in one, no forces are being applied and in another, there are forces being applied (how else would you change directions?).

Brain can't feel without senses input.

is the constant acceleration of orbit fundamentally different than no acceleration...?

NO.

how else would you change directions?

You don't. You keep going straight, space is deformed by gravity.

But even if you look at it like in classical mechanics, the effect is applied uniformly to every particle of your body, so it makes no difference.

Ask yourself this: how do you feel gravity right now?

Ok but why?

>You don't. You keep going straight, space is deformed by gravity.

Yeah, and if gravity weren't deforming the space, objects otherwise in orbit would move differently. That's just changing the mechanics (presumably in an attempt to appear more knowledgeable?) to avoid the question of why two wildly different scenarios (no forces vs. offsetting forces) are the exact same.

>But even if you look at it like in classical mechanics, the effect is applied uniformly to every particle of your body, so it makes no difference.

Again, my question is why in your model is the uniform application of a force the same as no application of a force?

>Ask yourself this: how do you feel gravity right now?

You don't have a sense for your own weight? I do and I don't know how to describe that feeling beyond that.

If I were in a true extremely low gravity situation (like deep space) I would feel differently.

O_o

Again, my question is why in your model is the uniform application of a force the same as no application of a force?

Tha's not my model, it's Einstein's.

Orbit is free fall. It’s equally correct to describe a falling object’s weightlessness as moving as fast as gravity.

> get why this 'feels' like weightlessness/0G, but does it actually have that impact when it comes to physical manufacturing

No, it’s the first postulate of Einstein’s theory of special relativity [1]. Free fall and the absence of gravity are as indistinguishable as acceleration and the its presence.

[1] https://en.m.wikipedia.org/wiki/Postulates_of_special_relati...

In a curved orbit, that may be true at points, but for an extended object, tidal forces come into play:

https://en.wikipedia.org/wiki/Tidal_force

For example, it was very hard to replicate the moon's gravity when training pilots to land on the moon. How do you 'fake' a different gravity on Earth? It's pretty hard to do: https://www.youtube.com/watch?v=aw8kRZEvh_s

EDIT: to your question about centripetal force, either you experience acceleration or you don't. Since gravity is in equilibrium with centripetal force relative to movement around Earth you shouldn't get acceleration from this. However, you will get micro g's from rotation of the station itself, etc.

If there is no acceleration, then how are objects changing direction?

Also I should add, it is confusing thinking about 0g, because obviously bodies in a gravity well are experiencing a gravitational force. Really we're talking about 0 acceleration, where g is the acceleration due to gravity. In orbit this g acceleration is cancelled out by centripetal acceleration to produce 0 acceleration, or free fall.

If it were not for the force of gravity, an object in motion would move in the direction of its instantaneous velocity. It does not do that, it instead accelerates toward the center of the gravitational body.

>In orbit this g acceleration is cancelled out by centripetal acceleration to produce 0 acceleration, or free fall.

But again, they do not "cancel out," otherwise how is the instantaneous velocity constantly changing direction?

https://en.wikipedia.org/wiki/Shot_tower

Throw a ball parallel to the ground. Now throw it faster. It will land farther away than last time, right? Keep throwing it faster and faster and the ball will keep landing further and further away from you. Eventually, you throw it so fast that the ball flys through the air, all the way around the earth and lands back at your feet from behind you. You've just completed a single orbit around the earth. Keep throwing it faster and faster until the ball flies past you forever without touching the ground. This is a little hard to imagine because this speed is tremendous and something no one can really experience on earth.

The ball is constantly falling away from that direction you threw it originally due to gravity. Gravity is always acting on the ball and is always acting on any satellite in space as well. Gravity doesn't change that much for how high satellites fly. However the speed of the ball is just so such that it will never change from the height you originally threw it from.

Catch the ball out of the air and throw it just a little faster this time. The ball will still orbit but will pass over your head this time. The speed of the ball dictates the orbit altitude. Mass also factors in as well but not much for something so small. Grab it out of the air and keep throwing it faster and faster and eventually, the speed is able to overcome gravity and the ball leaves Earth's gravity entirely.

In Low Earth Orbit, there is just enough atmosphere to provide some minor air resistance that will actually slow down that ball you threw. As the ball slows, the orbit altitude decreases. As the altitude decreases, the atmosphere gets thicker and air resistance increases which makes the ball slow even more. It gets so slow that it can't maintain an orbit any more so it lands on the surface. If you attach a small rocket engine to the back of the ball, you can occasionally turn it on to maintain the exact speed you need for that orbit. If you use the rocket engine to make the ball go faster, you can raise the orbit. Rotate the ball 180deg and now you can use the rocket engine to slow the ball to lower the orbit.

Astronauts in space constantly have gravity on them but they are moving at such high speeds that gravity is not able to change their altitude. They are always "falling" just like the ball but never land. They float around inside their spacecraft because those too are falling constantly.