I live in California, by the way.
No. You’ll die on the way.
If you mean what’s opposite to california, get a globe & a knitting needle. Just looking at a map (which is a bad way of doing it), I’d guess somewhere between Australia and Madagascar.
No.
If you start from 40[sup]o[/sup]N, 120[sup]o[/sup]W (which is about where San Francisco is), and dig straight down, you’ll come out at 40[sup]o[/sup]S, 60[sup]o[/sup]E, which is in the Indian Ocean, near Madagascar. If you dig straight through the center from the northern hemisphere, you have to come out in the south, and all of China is in the north.
If you started from Beijing and dug straight down, btw, you’d emerge somewhere near Buenos Aires.
Also, if you dig straight down, you’ll stop when you get to the center of the earth. Then you’ll have to dig up.
Well if you dig straight ‘down’ you will hit the molten centre of the earth and die but let us assume (in the spirit of the original question) that you have the right equipment to enable you to survive.
You still wont make it. The centre of the earth is the earth’s centre of gravity (duh) when you get close to the centre the gravity down there will be waaaaay stronger than up here. You will end up being pulled to the molten centre and gravity will prevent you from swimming out.
Best not to try it.
>> when you get close to the centre the gravity down there will be waaaaay stronger than up here
Try again
Okay, it hasn’t taken us long to get off-topic here 
. What is the gravity situation at the exact centre - are you weightless (equal force being exerted from all directions)?
ObOP: Sublight has the right idea, use south latitude instead of north latitude, or vice versa, and just add or subtract 180 degrees in longitude.
I’m pretty sure that there is a thread somewhere (the last week?) where you can find the gravity situation at the center of the Earth. It’s probably in a highjack of a question about falling through a hold drilled all the way through the Earth. Cecil answered one of those.
Gravity doesn’t increase or decrease much as you go down–it pretty much stays the same until the core-mantle boundary, then it decreases to zero at the center.
Believe me, China is the opposite of Ohio. It took my dog 15 minutes in my yard to dig there. She is a 3 lb. poodle and is now litter box trained so she can no longer go outside and bother those people.
How could you possibly think you’d end up in the same hemisphere?
There’s two ways to look at this:
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Digging straight through the center of the earth and noting your location when you emerge. IOW, noting your starting location’s polar opposite.
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Digging from one side of the earth to the other as if you slicing through the top of it, thus avoiding the center of the earth. Well, someone doing this experiment on the equator would, by necessity, have to go through the center of the earth. But you get the idea. Your latitude would stay the same, only your longitude would differ. (This would be why the OP thought she’d be in the same hemisphere). I don’t have a globe handy, and I don’t feel like looking up lines of longitude right now, but I’m guessing someone digging from SoCal to the opposite side of the northern hemisphere would wind up in northern India. YMMV
I asked this a couple years ago, and the only response was for somebody to call me a nerd and somebody else to say “who cares”, but it still bugs me, so I’ll bring it up again:
Why does the perception of digging through the earth from the US bringing you out in China persist? Where did it start? A moment’s thought will make you realize that the antipodal point has to be in the opposite hemisphere. Specifically, the US is reflected onto the Indian Ocean.
True, it’s usually being used as a gag, most often in cartoons, but it’s a remarkably persistent one. Modern cartoons often overturn or take a new twist on stock gags from “classic” era, but they STILL have characters dig through the Earth and come out in China.
I can also see that it’s difficult to wax comic about characters popping up in the middle of the ocean, as opposed to someplace like China, allowing them to draw funny pictures of China and Chinese guys. But why not at least Australia, which is far closer to accurate, and allows funny drawings of aborigines or guys with corks around their hats saying “G’day Mate”?
OK so what if I dropped a neutron star fragment at that spot - where would it pop up.
Perhaps originally from the psychology equating China with the most remote, exotic place on Earth in relation to the US - using the “mysterious Orient” in symbolic terms. I doubt anyone ever meant the term literally; simply as a figure of speech.
But if you start digging from the US directly toward China, while your hole won’t be perfectly straight down, it will be at a pretty steep angle. If you keep the hole straight, you’ll even be digging “straight down”, in even one of the literal senses.
Do any of the global Dopers have similar expressions? Do Aussies dig “straight down to England”, for instance?
I didn’t see rastahomie’s article before that post.
I suppose you could argue for your case 2), but unless you are at the equator, it means you are conceptually digging at a slant and not “straight down”.
India is south of much of the continental US. Your technique maps the US largely onto a large number of other political entities in central Asia as well, including Pakistan, Afghanistan, Several republics of the former Soviet Union, and … Western China.
Well, why do people think that falling raindrops have points on the back? (They actually look like spheres.) Why do they think that gravity in outer space is zero? (At the altitude of the space shuttle, gravity is only 15% less than gravity at sea level.)
These are “memes” or infectious ideas. Once the number of people “infected” with an idea becomes large, that idea becomes part of the unexamined assumptions of concensus reality (they attain the status of “common sense.”) But why? I think it’s because most humans habitually use a common mental shortcut. They make the unwarrented assumption of “that many people CAN’T be wrong.” It’s a herd-following instinct that keeps individuals safe. But it can lead entire “herds” off cliffs (the spread of Urban Legends, the power of corporate groupthink, the power of cults, whole countries turning into psychopaths during WWII.)
This thing about falling through to China is essentially an Urban Legend of physics/geology.
Ignorance is not the problem in the world. It’s the things people “know” that aren’t so. - Will Rogers
GASP! You’re thinking for yourself! BLASPHEMY! In some situations you’ll risk your career or even your life if you blatently go against group opinion like that.
And the existence of this “herd-mind” or “groupthink” phenomenon shows why it’s so incredibly important to teach Critical Thinking. This doesn’t really occur, at not least in schools in the USA where conformity is rewarded, and where anyone who dares to question Teacher gets a bad grade.
I think that’s wrong, but I can’t find a ref.
Last I heard, gravity increases slightly as you go down, since the crust is low density. But then a few (tens? hundreds?) miles deep the gravity starts continuously decreasing. Yes, it starts decreasing faster at the core/mantel boundary, but the change isn’t all that much. Only if the core was MUCH heavier than the mantel would gravity stay somewhat constant on the way down.
Why bother, it’s better and FASTER to get a helicopter and hover above the ground and let the Earth spin around until you get to the other side. It’ll only take 12 hours.
Actually, if you dig down from California you really will reach China!
At the top of a tower of that height, gravity would be about .85 g, as you note. But nobody’s ever been to the top of such a tower. The only way anyone’s ever gotten to the altitude of the Space Shuttle is in orbit, and in a very real sense, gravity is zero in orbit.
As for the “hole to China”, I suspect that Australia wasn’t used because Australia has a very similar culture and society to the United States (or, for that matter, England, or even most of Europe). They speak a European language, they wear the same sort of clothes, they have a similar physical appearance, they eat the same foods (except for Vegemite), etc. Australia may be geographically closer to antipodal to the U.S., but China is about as opposite as you can get culturally.
If the Earth were at a uniform density, then gravity would decrease linearly as you went down: i.e., halfway to the core, gravity would be half as strong. As it is, the Earth is not a uniform density: The core is much denser than the rest. This leads to the approximate gravity profile described by RM Mentock. Note that “stays pretty much the same” is consistent with “increases slightly”.