Physicist: This is a beautiful question, in a small part because it’s an interesting thought experiment with some clever math, but mostly because of all the reasons it couldn’t be done and wouldn’t work. Right off the bat; clearly a hole can’t be drilled through the Earth. By the time you’ve gotten no more than 30 miles down (less than 0.4% of the way through) you’ll find your tunnel filling will magma, which tends to gunk up drill bits (also melt everything).
Jumping into a hole drilled through the Earth. What’s the worst that could happen?
But! Assuming that wasn’t an issue, and you’ve got a tube through the Earth (made of unobtainium or something), you still have to contend with the air in the tube. In addition to air-resistance, which on its own would drag you to a stop near the core, just having air in the tube would be really really fatal. The lower you are, the more air is above you, and the higher the pressure. The highest air pressure we see on the surface of the Earth is a little under 16 psi. But keep in mind that we only have about 100 km of real atmosphere above us, and most of that is pretty thin. If the air in the tube were to increase in pressure and temperature the way the atmosphere does, then you’d only have to drop around 50 km before the pressure in the tube was as high as the bottom of the ocean.
Even worse, a big pile of air (like the atmosphere) is hotter at the bottom than at the top (hence all the snow on top of mountains). Temperature varies by about 10°C per km or 30 °F per mile. So, by the time you’ve fallen about 20 miles you’re really on fire a lot. After a few hundred miles (still a long way from the core) you can expect the air to be a ludicrously hot sorta-gas-sorta-fluid, eventually becoming a solid plug.
But! Assuming that there’s no air in the tube, you’re still in trouble. If the Earth is rotating, then in short order you’d be ground against the walls of the tunnel, and would either be pulverized or would slow down and slide to rest near the center of the Earth. This is an effect of “coriolis forces” which show up whenever you try to describe things moving around on spinning things (like planets). To describe it accurately requires the use of angular momentum, but you can picture it pretty well in terms of “higher things move faster”. Because the Earth is turning, how fast you’re moving is proportional to your altitude. Normally this isn’t noticeable. For example, the top of a ten story building is moving about 0.001 mph faster than the ground (ever notice that?), so an object nudged off of the roof can expect to land about 1 millimeter off-target. But over large changes in altitude (and falling through the Earth counts) the effect is very noticeable: about halfway to the center of the Earth you’ll find that you’re moving sideways about 1,500 mph faster than the walls of your tube, which is unhealthy.
The farther from the center you are, the faster you’re moving.
But! Assuming that you’ve got some kind of a super-tube, that the inside of that tube is a vacuum, and that the Earth isn’t turning (and that there’s nothing else to worry about, like building up static electricity or some other unforeseen problem), then you would be free to fall all the way to the far side of the Earth. Once you got there, you would fall right through the Earth again, oscillating back and forth sinusoidally exactly like a bouncing spring or a clock pendulum. It would take you about 42 minutes to make the trip from one side of the Earth to the other.
The clever math behind calculating how an object would fall through the Earth: As you fall all of the layers farther from the center than you cancel out, so you always seem to be falling as though you were on the the surface of a shrinking planet.
What follows is interesting mostly to physics/engineering majors and to almost no one else.
It turns out that spherically symmetric things, which includes things like the Earth, have a cute property: the gravity at any point only depends on the amount of matter below you, and not at all on the amount of matter above you. There are a couple of ways to show this, but since it was done before (with pictures!), take it as read. So, as you fall in all of the layers above you can be ignored (as far as gravity is concerned), and it “feels” as though you’re always falling right next to the surface of a progressively smaller and smaller planet. This, by the way, is just another reason why the exact center of the Earth is in free-fall.
The force of gravity is 
Holy crap! This is the (in)famous spring equation, F = – kx! Physicists get very excited when they see this because it’s one of, like, 3 questions that can be exactly answered (seriously). In this case that answer is 
Interesting fun-fact: the time it takes to oscillate back-and-forth through a planet is dependent only on the density of that planet and not on the size!
if the hole was drilled exactly from pole to pole rotational forces would be zero. the difficulties posed by this would be insignificant compared to the rest.
In a YouTube video Neil deGrasse Tyson is shown falling through a hypothetical Earth-tunnel:
https://www.youtube.com/watch?v=NOHBDiR5urE
Tyson verbally repeats the predictions of the equations provided by “The Mathematician” (i.e, 84 minute oscillation period, dependent only on density, etc.).
But we DON’T NEED to drill a hole through the EARTH to find out if the equations are correct. It is important to realize that we CANNOT KNOW whether the equations are correct or not until we actually DO a scaled down version of the experiment. As I’ve posted above, such a test is quite feasible.
The STORY of falling through the Earth is so common that even physicists fail to acknowledge its MYTHICAL character. We do not yet have any empirical evidence to back it up.
If we are only interested in ENTERTAINING a mostly rather gullible audience, then we will be satisfied with equations, hand-waving, video simulations and the like. Whereas if we abide by the EMPIRICAL IDEALS of science, then we will set out to actually PERFORM a scaled down version of this experiment that Galileo proposed so long ago.
@ Richard Benish
Two problems with a straight hole from pole to pole is the Earth wobbles on its axis and so there still would be rotational forces. The other problem is convincing the Flat Earth lunatics there is a South Pole.
Sounds just like religion.
I am a third generation driller..so the drilling part I understand. One the rig u would need would have to be about the size of Colorado. For the gear ratio and motor to turn the pipe with weight at let’s say 20 miles ( over 2x the deepest hole drilled) one it would take probably hundred years just to drill that depth for remember when making a hole ur just dispersing the matter to a different area. So getting this material above ground at that depth would I would guess 1ft of hole at 10k would take the material about day and a half to come to the surface.now question of the drill pipe 🙂 ..to withstand that pressure and torque to keep from shaping off well I know of no such materials.
Really, the hole wouldn’t be dug conventionally, everyone knows you would use a particle beam plasma rig.
The gravitational principles that would be revealed by doing a scaled down version of the experiment are the same as what would be revealed by digging a hole through a planet. As the last few posts indicate, the planet idea involves lots of fantastic stuff. Whereas the scaled down version is easily within the scope of feasibility.
So why not just do the scaled down version? It has not yet been done. Galileo proposed the idea 383 years ago. The experiment is not only feasible, it would be cheap compared to many other experimental adventures that physicists sign up for and taxpayers pay for. Why keep the spirit of Galileo waiting any longer?
I just wanted to know how many miles it would be if a hole was drilled through the earth from pole to pole
@ron jamed,
C = 25,000 miles; Earth’s approximate circumference
d = C/π
d = 25,000/π
d= 7961.783439490446 [approximate diameter in miles]
Hail a neutrino taxi; you’ll be there in no time (approximately)
gravity is a straight line in a curved space time therefore the equation
f=-kx is not possible
Talk, talk, talk.
Why not let’s hear what Nature has to say?
A scaled-down version of the experiment is well within our technological grasp.
if a person jumped into the tunnel there wouldn’t be much gravitational force attracting the person falling down because he wouldn’t be attracted by earth’s gravity (at least not to the ground) as he has drilled a tunnel passing through the earth.
I have a related question. Suppose it was not a person passing through the hole, but a small black hole, for example one 100 times the mass of the earth. What then?
Note that the black hole would make its own tunnel, and I think it would be about a meter in size. But instead of the black hole falling through the earth, the earth would oscillate around it, at least it would as long as the planet survived.
Would shmould.
All these guesses need to be checked against Nature.
A scaled down version of the experiment is well within our technological grasp.
Does reality matter? Or do we just do math here?
The configuration may vary. At the bottom of it all, the unanswered question remains: Gravity-induced free-falling radial oscillation–does this happen in physical reality, or is it only in our minds?
We do not yet know, but are entirely capable of finding out. Why don’t we?
Does the 37 or so minutes it is said to do this, to fall through the Earth, account for all of the gravitational differences and nuances throughout the fall and return from the fall during the oscillation, when presuming near the center of the core it is weightless allwhile on the surface is normal gravity?
Hmm
@Michael Fuller
Yup!
You guys should read a book named The Krone Experiment. You will like it.
But if there are rotational forces, wouldnt you just go a little past the core and come back a little past the core forever? Sorry if someone already said this,
So, if we ignore friction and air, but keep the earth rotating and started digging right on the equator… what curve would the hole have to follow so that the jumper always stayed in the middle of the shaft?
Interesting thing is that it would take 42 minutes to go between any two points on Earth if you dug a straight tunnel and were able to slide without friction.
I Am Ready To Fall. Where Is The Hole Then
a question for all you physicists out there, if you drilled a hole into the side of a mountain when you got to the center going sideways, would the air pressure be greater in the middle of the mountain than the outside, assuming you went L to R not up or down from the base?
No – identical. The air pressure is a function of the amount of air pushing down from above and it is isotropic (same in all directions at any single point). Therefore the pressure at any point in a tunnel that is open to the atmosphere is not dependent on rock mass above it but only on the mass of air above it (which is largely dependent on that point’s distance from the edge of the atmosphere.)
You didn’t stipulate conditions: A tunnel with a draft (windy day) will act somewhat act as a venturie; in such a case, the air pressure will be less inside the tunnel than the outside. Any convergence or divergence of the tunnel will cause differences in pressures. Temperature and humidity also changes air density. As a former coal miner that has punched in one side of a mountain and out the other side, I know that differential and equal pressures will exist between the inside and outside of a mine at different times of the day; with either pressure being higher, lower, or equal. Yet coal mines do force airflow with an exhaust fan.`To answer your question correctly, you need to first provide all specific details that determine a correct answer.
So all the theorist ideas aside…..if one fell though the hole in the earth, would you come out on the other side, feet first or head first? Simple question. I would like to know.
Quick answer would be if you got yourself into a fall where you were continually going feet first and not tumbling, then (if you came out, which you wouldn’t) you would come out feet first. If you dived in and managed to stay head first, you would come out head first.
The only thing that would turn you would be inertia (i.e. if you had a tumble going you would keep tumbling) and the force of air on your body. The force of air would be bay far the dominant force in this situation. It would tend to turn you around if you changed your position as you would get different drag forces on different parts of your body.
If you were in a vacuum and you were tumbling, you would just keep tumbling unless you could work out some complex arm rotations that counteracted the angular momentum of your body.
as the above topic if we really jump into the tunnel then after getting deeper and deeper do we come up back to earth surface because of escape velosity or does our earth floats in orbit because of gravity which implies by the tunnel do we enter space? if no what happens to us
Does scientists have proof that the earth’s core is solid?
If earth was cold and solid I think it never could b to drive a tunnel through the earth . The pressure of the earth would crush us in and if you could go through the centre you would stall at the centre gravity would pull back to the centre . Once you track the centre the force of gravity will reverse you will head on a upwards direction it’s an amazing question to answer .
Fergal reid, answer the question please, if you can.
All these answers that I have read here just seem to be excuses.
If you pushed a rod down through the earth, lets say from Glasgow, and aimed at Sydney, would it come up through the ground in Sydney? To me that is logical, but if this is true, then they must be upside down! I’m looking at the globe in my lounge, I don’t care what shape the earth is, just can’t comprehend it. I know you understand
If the Earth is rotating, then in short order you’d be ground against the walls of the tunnel, and would either be pulverized or would slow down and slide to rest near the center of the Earth. This is an effect of “coriolis forces” which show up whenever you try to describe things moving around on spinning things (like planets).
What if you put the tube inside the Earth’s north pole(or any perfect diameter of Earth)?
Would that stop the coriolis forces?
@Ryan
You’re absolutely right: drilling along the poles (Earth’s axis of rotation) would completely fix this problem.
Superman climbing down a ladder of a tube that goes right through the earth from one side to the other. He begins to climb down the ladder on one side of the planet. So when he exits the tube (on the other side of the planet), his feet will come out first, obviously. In other words, when beginning the ladder climb, superman was originally standing upright. But, when he exits the tube at the other side, he basically comes out ‘upside down’.
True, he he would switch as he passed the center of the inner core, but it would be enormously hard to continue climbing, as he’s climbing up. Upside down.
Galileo proposed this idea in 1632. In recent years–especially since the late 1960s–proposals have been made to build a scaled down version and send it in orbit to measure Newton’s constant G. Technical difficulties render the latter proposals infeasible for improving measurements of G made in Earth-based laboratories.
These difficulties don’t mean the experiment would not work as a first approximation, only that the precision would be low compared to measurements of G that have already been done.
Many of the latter measurements were performed with Cavendish balances. If our concern were not to measure G, but to simply demonstrate the oscillatory behavior discussed here, such a balance could be modified for this purpose. The apparatus–both satellite and Earth-based versions–may be called a Small Low-Energy Non-Collider.
Gravity-induced radial motion through the centers of massive bodies has never been observed. The equations in the article pertaining to this behavior have never been tested. They are only predictions. Application of the empirical ideals of science would therefore dictate that we should at last build and operate humanity’s very first Small Low-Energy Non-Collider. However entertaining it may be to speculate on what “would” or “should” happen in the scenarios discussed here, we owe it to the spirit of Galileo to find out by asking Nature and thereby bring his proposal to fruition.
lets for moment get passed the possibility of actually drilling a hole through the earth now lets fill the tunnel with water and place a superman skin diver in the center that could take the pressure. what would the atmospheric pressure be on the diver be. Now move the diver away from the center. also lets make the tunnel at different angels to the equator. I believe that this type of hypocritical situations is crucial to insightful thoughts that led to realistic scientific realities like a Cavendish type of experiment in space as well as electromagnetic and permanent magnetic mass and mass of non ferro magnetic material. I am curious as to any insightful thoughts concerning the hypothetical situations. As well as ship water displacement calculations
The (w)hole idea seems absurd to everyone except Jules Verne.
Ken Baldyga:
“The (w)hole idea” is absurd only with respect to using astronomical bodies as the source masses.
With respect to laboratory sized source masses, by contrast, “The (w)hole idea” is not only not absurd, it is way overdue to be acted upon.
In his recent book on the subject, “Going Underground,” Martin Beech refers to the THOUGHT experiment as a “right of passage kind of problem.” He explains that this is manifest by its ubiquity in elementary level physics and calculus textbooks (not to mention internet forum discussions).
Beech also acknowledges Galileo’s role in discussing the problem. As I’ve argued above, there is no good reason to leave it as a THOUGHT experiment. Physicists owe it to Galileo and themselves to turn it into a real PHYSICAL experiment. A well-received essay on other reasons why we need to at last fill this huge gap in our empirical knowledge of gravity can be accessed here:
http://vixra.org/abs/1612.0341
Better than that. What if you drilled a hole through the earth at a 45-degree angle to the equator. Now fill the tunnel with water and put a skin diver or deep water sub at the center. What would the atmospheric pressure be on the skin diver or sub? Move the skin diver toward the surface either way now what would it be?
Pingback: What Would Happen if We Dig a Hole Straight Through Earth – What If
Pingback: What Would Happen if We Dig a Hole Straight Through Earth | What If Show
Falling only has meaning if there is the expectation that you’re going to hit something. If you fall off a second-story high roof you expect to hit the earth. But if you go through a hole drilled all the way through the earth there is no expectation of hitting anything thus you can’t be falling you would merely be floating or flying but not really falling especially when you pass the middle of the earth and continue to the other side. Eternally traveling back-and-forth?
I only caught sight of this discussion because I indulged in this exact thought experiment in 1983 using, of all things, a programmable HP 41CX which only had if I remember correctly only 150 programmable statements max. Modeled the earth as successive onion slices, subtracting gravity above the variable tunnel explorers’ vicinity and conversely adding mass gravity below.
Bottom lines: Took 3 “casual” months to run. Imagine my smile when this article confirmed the same 42 minute excursion result. Oh, and the max velocity at earth’s center was 18,000 MPH. What a goofball I was forty years ago to do something like that.
Simulations can be fun, tedious, and sometimes enlightening.
Problem is, they are not physical reality.
The fact remains that, even though the experiment was proposed by Galileo in 1632, a scaled-down version is doable with modern technology, and proposals have been on the books since the 1960s, we still do not really know what happens when a test mass is dropped into a hole through the center of a uniformly dense source mass.
Were the spirit of Galileo alive today, someone with the resources to bring his proposal to fruition would surely have done so. Sad state of affairs, I say.
An in depth discussion of these matters can be found here:
https://vixra.org/abs/1612.0341
If a person could place himself in a capsule that protects him from heat, pressure and rotational forces he still would not be able to travel from one side of the earth to the other through a hole. The same force that made him travel in the hole would prevent him from leaving the hole. The capsule would gain great speed and would accumulate mass energy, it would be enough to pass through the center of gravity and travel a great distance but not far enough to reach the other side, the capsule would slow and eventually reverse direction, it would repeat this process until it runs out of energy and would be stuck at the center for ever, like light in a black hole.
I haven’t read through all responses so this may have been asked by someone else.
Would the weight of all of the dirt being pulled out of the earth make the earth spin even more erratic
Until the physics community at last carries out a scaled down version of this experiment, I imagine Galileo rolling in his grave, appalled and unimpressed at how oblivious of physical reality modern “physicists” have become.
So, if we ignore friction and air, but keep the earth rotating and started digging, could we follow a curve so that the jumper always stayed in the middle of the shaft?
Could this be a low-cost/low-energy mode of transportation?
Yes and no. Yes, in theory you could follow that curve. My first approximation sketch of that curve is here: https://www.quora.com/If-a-hole-is-made-right-through-Earth-so-it-reaches-the-other-side-what-will-happen-when-one-jumps-into-it/answer/Robert-Stevenson-47
No, you could not practically perform this experiment. The pressures and temperatures would make it impossible to dig the hole, but even if you could dig it and insulate it, you would need to maintain a vacuum in the hole. That’s because the atmosphere would soidify due to pressure at about 400km down, and there’s still a looooong way to the core after that.