[Jabbles]

Perhaps someone here can explain something that has annoyed me since I saw Inception. Falling (accelerating under gravity) is meant to "wake you up". Whilst falling you feel weightless - almost by definition (if you and the weighing machine are accelerating in sync, you apply no pressure to it). For some reason falling causes the loss of gravity in the dream world, and there's that whole scene about "recreating gravity". But since falling is indistinguishable from being weightless, what is stopping the dreamers from waking up? And why does weightlessness only go one level down?

http://en.wikipedia.org/wiki/Weightlessness

[rdtsc]

> Whilst falling you feel weightless - almost by definition (if you and the weighing machine are accelerating in sync, you apply no pressure to it).

Ah but how often do have a chance to feel weightless? Unless you are on a space station, bungee or parachute jumping? So the feeling of weightlessness itself is pretty startling.

Also it is the moment from when you are standing on something and get pushed over the edge and then all of the sudden you are falling that is quite startling.

Think back on a dream of you falling. Everyone has those. For me, it is always the weightlessness that is shake me up and wakes me.

[ars]

Feeling weightless feels EXACTLY like falling. It does not feel like floating.

[joeguilmette]

I disagree. I have around a thousand skydives. The only time I feel a sense of falling is when acceleration is involved. When acceleration is involved, weightlessness is not.

When jumping out of an aircraft you are already going around 100mph, close to terminal velocity. There is not a pronounced sensation of falling. It feels more like laying on your stomach in water, it a bit windier.

When jumping out of a stationary object, the feeling of falling is quite pronounced until you stop accelerating. A hot air balloon or helicopter produces this effect (and is pretty damn fun). While I've never done it, BASE jumping provides a similar sensation.

[ars]

Why do you disagree? You are describing EXACTLY what I said.

Did you typo and mean to write agree?

When you hit terminal velocity you are no longer in free fall, I would expect it to feel like pressing lightly on something - which is what you describe.

To be in free fall you have to be accelerating (that's why it's called free fall and not zero gravity), and again that's what you describe.

This is not a correct sentence: "When acceleration is involved, weightlessness is not." In fact it's exactly the oppose of that.

You can't have zero gravity near the earth - the earth has gravity, and you can't get away from it. Instead you accelerate at exactly the same speed as the acceleration from gravity. In order not to hit the ground due to your acceleration you move in a big circle and keep missing the ground.

The reason you don't keep getting faster and faster is that you keep accelerating in a different direction, your average is zero, but you are always accelerating, just in different directions (and you make sure to always put the earth in the right place to match your acceleration).

People on the space station feel like they are falling the entire time. Presumably they get used to it after a while, but that's what it feels like.

[joeguilmette]

You said feeling weightless feels like falling.

I don't know where you get the idea that being weightless feels like falling. Astronauts always feel like they're falling? Do you have a source for that?

They dive bomb a 747 to simulate zero g to train astronauts. I've done it is smaller planes. It feels like your are weightless - floating a pool. It does not feel like you're falling, like you just fell off a roof or a hot air balloon. When you fall, your stomach drops. You go from 0mph to fast.

When skydiving you do not feel like you're falling. Sometimes you get little stomach drop when you leave the plane (the 30mph increase in speed) but after you hit terminal you feel weightless and the sensation of falling is gone - you are no longer accelerating.

Now, we call this state freefall and you say freefall is the state prior to this, when you are accelerating towards terminal. I don't know the physics behind it, nor do I have a grasp on the nomenclature as you do.

That said, I have felt it with my body many thousands of times.

When you jump off something that isn't moving you feel like you're falling because you're accelerating (like a rollercoaster). When you hit terminal you no longer feel like you're falling, you feel weightless, an entirely different sensation, similar to laying in a pool. You have no sense that you are moving at all, let alone at 120mph.

I have never been in space, but I've been in zero g bouncing around the inside of a plane and I can tell you it in no way feels like falling. At all. Not even a little. No way astronauts feel like they're falling the whole time they're in space. They probably feel - weightless :)

[natep]

Because it's not the falling, it's the jolt of landing. When in free fall, you are not actually accelerating. In terms of landing, though, it doesn't matter if you hit the ground or if, say, the bottom of an elevator hits you.

[Jabbles]

I haven't seen the film since it came out, so I may be mistaken. Didn't Cobb demonstrate to Ariadne that you wake up when you sense yourself falling? By tipping Arthur's chair over as he was dreaming? Arthur (if it was that character) didn't fall on the floor, there was no jolt. Also, doesn't the van land in the water, and no one wakes up?

[natep]

According to the Inception Wiki, we're both right.

> One method used to awaken from a dream within a dream is called a "kick", which is the sensation of falling, hitting water, or a sharp jolt that can startle the sleeper awake.

Although I still think it's terribly inconsistent, if the details matter. There's too many different kicks with too many subtle differences and similarity for me to go into in a reasonable-length post.

[natep]

OK downvoters, you're right. In the movie, they explain that a kick is the feeling of falling. So why didn't Cobb wake up when he was falling towards the water, but after he fell in? My guess is that the water invaded the dream and he drowned, and exited the dream via death. But they called that a kick, too. As we've seen, the movie is hardly straightforward. And if one of you had bothered to comment "they say in the movie that it's the feeling of falling" then I wouldn't have had to rewatch half the movie.