What effects would going very deep into a planet would have?

[WhiteWeasel]

I'm talking mohole deep and beyond. I know atmospheric pressure would go up, but what other effects it would have? Would it affect other things like gravity?

[Awaras]

Pressure goes up, temperature goes up, gravity gradually decreases the lower you go, because more and more of the Earht's mass is above you, pulling you in the other direction.

[WhiteWeasel]

How far would you have to fall to experience 1/3 normal gravity?

[Awaras]

No idea, to be honest... :/

[Scotius]

And when you reach center of the planet you are stuck there. So no, no tunnel to Australia or Chinese Syndrome

[Captain Sierra]

Well, no. You would have picked up speed as you descended. The core of the planet is the point at which the mass on either side of you is equal so passing it gravity effectively reverses. As you go up, gravitational acceleration increases and so does your rate of decelleration. You would basically get almost to the other side, only to be pulled back. That oscillation would continue for a long time until you eventually come to rest in zero g at the planet's center.

[lajoswinkler]

That is, if there was a tunnel filled with air at constant pressure, which is a completely impossible, imaginary situation.

If we're discussing regular planets, then in all cases it's growing temperature and pressure, but certain planets like gas giants show very interesting phase transitions.

Gravity weakens towards the center.

[Captain Sierra]

REgardless of the evenness of the air. Assuming there is atmosphere, there will be drag and going all the way through is impossible. ON an airless planet, it is in fact doable under teh assumption that you don't hit the walls and slow down.

[1001sd]

Vsauce made that video about (almost(?)) the same subject.

[MBobrik]

The main effect would be getting boiled to death before any other effects could affect you.

[Captain Sierra]

This is all hypothetical. We can afford to ignore the molten magma at the earth's core.

[Dunbaratu]

After a bit of depth under the planet's surface, the simplified single-point mass model of describing a planet's gravity that we're all used to from really basic introductory physics really breaks down and isn't sufficient any more to describe the situation. If the Earth was a uniform density of mass throughout, then the moment you drop below the surface you start weighing less because some of the mass is above you. BUT, actual Earth is not evenly distributed. The mass is a lot denser at the core than on the surface. This makes it so that you do actually get heavier as you go down for a little bit, because the effect of being closer to the dense core (smaller 'r' in the gravity equation) is larger than the effect of having some of the less dense mass of the crust now above your head. The boundary where your weight stops increasing and starts decreasing as you descend is actually down near the bottom of the Earth's crust.

Although once you start taking that into account you have to also take into account other inconvenient things like the molten mantle. Not only is heat a problem but there's the really basic difficulty of digging a tunnel in liquid.

[jwenting]

And when you reach center of the planet you are stuck there. So no, no tunnel to Australia or Chinese Syndrome

hence those tunnels (and yes, studies have been done) would not go through the center of the earth but at an angle, shallow curves through the crust.

Of course not being able to tunnel through the mantle is another very good reason for that.

That said, such tunnels would be impossible as well, as they'd have to cross plate boundaries and those plates tend to move rather quickly in places.

[nhnifong]

It's possible to pass right through the earth if you're a neutrino.

[CaptainKipard]

So "The fall" from Total Recall is nonsense then?

[WhiteWeasel]

So "The fall" from Total Recall is nonsense then?

And the pore from Freefall too?

http://en.wikipedia.org/wiki/Freefall_(novel)