Hole through center of earth

[@JoaoChimay]

and im here wondering how he writes facing him and it isnt backwards to the camera...

[@lifewhyz]

I was wondering the exact same thing. Then I assumed maybe they just get good at writing backwards. The direction of a drawing wouldn't matter as much as the direction of your spelling. But it's a good question.

[@bobthefly8271]

The camera flips the image, you aren't seeing the letters straight, you're seeing the teacher flipped.

[@jaronchaffinch2034]

But he has an audience.

[@lifewhyz]

@@bobthefly8271 If the camera was flipping him, then the letters would be backwards. And like Jaron said, he has an audience. So if the letters _were_ flipped, that would mean he was writing backwards for _them._

[@lifewhyz]

I'm actually pretty convinced now that he can write backwards. I tried it. It's not that hard. And if you were a professor doing it every day, I'd imagine you'd get used to it.

[@gregonfire1]

You would have to build the tunnel going through earths axis of rotation, otherwise you would hit the side of the tunnel due to the coriolis effect.

[@yoprofmatt]

+Greg Wilson Greg, excellent point! I hadn't considered this one. It becomes a very difficult dynamics problem. Cheers, Dr. A

[@barnenfrom6034]

gregonfire1 u r smart I did not think of that

[@rahuladhikari6990]

True

[@leethediamondninja1210]

@@dish125db hey he is smart keep the mean comment to your self!!

[@billmcginley]

@@dish125db Yeah? I'm sure he knows how to at least spell shovEL.

[@apex2242]

Exact same scenario was shown in an episode of oggy and the cockroaches in which the oggy gose on moving throughout tunnel forever

[@manuboker1]

BEST PHYSICS LECTURES EVER !!!

[@Betehadeso]

Hmmm this really does not make sense to me... first I would've thought that the guy would accelerate toward the center at a slower and slower pace and once there would be stuck, assuming the gravitational pull from either end is equal, secondly how can the guy get to the other side if the gravitational pull is againt him? Or am I isolating this too much?

[@MisterKilogram]

What Prof. Anderson explained is what the bible calls the bottomless pit (Rev. 9: 1-2 & 11, 11:7, 17:8, 20:1 & 3).

[@Parz5467]

BUT WHAT IF TWO PERSONS OF EQUAL MASS JUMPS TOGETHER 1 FROM THE 1ST HOLE AND 2ND FROM THE 2ND HOLE?

[@xyz1024]

Hey professor I know am 9 year late but YOU are RIGHT according to NEWTON gravity law BUT WRONG according to EINSTEIN gravity law

[@stratoskonstantoudakis9245]

i wish i had this type of teacher back in highschool

[@zanick2]

but what would the situation be if there was air resistance, so terminal velocity would be reached after only a few seconds, and be far slower than if the drop was in a vacuum tube? as we know from this physics question that the vacuum tube would allow the path through the earth to take only 42 seconds. so we are talking speeds of 1000s of miles per hour. (8000miles in 42min)

[@psxinformation]

Excellent professor .....I'm from Pakistan.

[@josephdragan7734]

what would be the experienced difference between two vacuum tunnels where one is from north pole to the south pole and the other tunnel is from a spot on the equator to the opposite spot on the equator. That is to ask: how would the earth's rotation affect the result?

[@abhilashsaini8089]

and if we dig a hole ....what would be the effects on earth's rotation ?????

[@yoprofmatt]

abhilash, Great question. Sort of depends on what you did with the dirt. If you dug through from one equator to the other, and piled up the dirt near each hole, the earth's spin would actually slow down a bit (just like the spinning ice skater putting their arms out farther slows them down). If you moved this dirt to the North and South pole, the earth would spin a bit faster (ice skater pulling their arms in). But if you dug from the North Pole to the South Pole (specifically, along the axis of rotation) and left the dirt near the hole, it would have no effect on the earth's rate of spin. But if you moved the dirt to the equator, the earth would slow down (even more than before). Cheers, Matt

[@abhilashsaini8089]

I get it

[@abhilashsaini8089]

thank you ... :)

[@lifewhyz]

What if we displaced the dirt? Sent it off into space, for example?

[@josephdragan7734]

Do we believe that all the interiors of the earth rotate relative to each other as a solid mass or do they spin at different rates as you reach the core?

[@KingLouisII]

Interesting. I'm not a student, came across by accident (thanks KZbin autoplay). A good illustration of this to play with it using the video game Portal. If you put two sides of the portal on the ground, and jump in, you'll experience the shift in gravitational direction explained here. You'll bob up and down forever. Of course you can move out of this loop, because game physics. But the game doesn't take air into account in its physics code. So, although it happens in a second or two, you'll get the same effect illustrated here.

[@yoprofmatt]

Okay, that sounds pretty cool. Now I want to play it. Cheers, Dr. A

[@kishorsonawane5990]

What bout that flat earthers

[@yoprofmatt]

I guess if you did this with a flat earth, dead in the center, you would still bounce up and down. That could be an interesting calculation... Cheers, Dr. A

[@kishorsonawane5990]

Matt Anderson love ur lectures

[@yoprofmatt]

Thanks for the feedback. Cheers, Dr. A

[@derrelllipscomb693]

If the gravity at the center of Earth is zero (cancelled by all the counterbalancing effects of the combined Earth’s mass), then we should also expect to see a ‘vacuum’ at that point too, right? There should also be a gradient of gravity that goes from micro in space to ~1 at the surface of Earth, This might seem quite profound but think about it and let that sink in a bit. Ok, now add your rotation to explore what might actually exist at the center of Earth.

[@stuyvenstein]

Ok, so I have another question regarding this scenario; It is said that orbiting is not perpetual motion, because the emission of gravitational waves drains the energy of the orbital bodies, eventually pulling everything toward the body with the greatest gravitational field (Planets are pulled toward the sun for example) So if this info is correct, can we not say that in the above scenario, the gravitational energy will eventually run out, and while this is happening, the object being pulled back-and forth will slowly start closing the gap until eventually coming to a stop as all energy has been depleted, and there is no longer any gravitational wave emissions?

[@goerizal1]

at the center of the earth, in this scenario, the gravity of the earth's mass above and below him should be equal theoretically so identical opposing forces are pulling him upwards and downwards but his momentum will allow him to fall farther to the other end in a gradually slowing fashion then yoyo back upward to the hole to eventually settle at the center where the opposing gravity from the earth's masses above and below it are equal. please comment on this.

[@ptyptypty3]

no doubt a modified version of the coriolis effect would apply if a tunnel was drilled at the Equator.. Your Tangential Velocity on the surface would cause you to bounce into the Eastern Wall of the tunnel as you descended. But at least we'd know if there really was a HELL down there.. :D :D :) ...

[@ptyptypty3]

speaking of the Equator.. if you were standing at the Equator and were facing EAST.. and then the EARTH instantly stopped Rotating... you would be traveling at about 1,500 mph to the east.. over the ground below your feet.. along with the trees and buildings and oceans.. GO FIGURE....

[@stankfaust814]

Gravity is a general relativistic problem, your newtonian explanation may have had some traction 300 years ago but it fails to explain adequately or even close to accurately what is occuring within a gravity well like the earth if we were to send an observer particle through the center. There are a few key principles to keep in mind when doing a thought experiment like this. 1. This is a question of time and clocks. If I have 3 identical clocks, one in deep space, one on the surface of the earth and one at the center, the one in deep space will be running the fastest (Unaccelerated frame of reference) the clock on the surface will be running slower due to its acceleration of 9.8 m/s2 and the clock at the center will be running much slower than both. why? 2. The earth is a gravity well with its deepest point at the center. It's why all objects fall towards the center as though it were a point mass. General relativity (and its acceleration) do not start or end on on some arbitrary surface of a planet, rather it extends all the way to the center. 3. Matter stratifies by density in a gravity well. Lightest gasses at the top end of the radius from the center and the densest matter at the core. 4. Due to general relativity, A large body in rotation (like the earth) will not rotate uniformly from the surface to the core. It can't. Time runs slower at the core than at the surface and therefore the core will spin faster than the subsequent layers of strata. On the earth, (and every large rotating body in our solar system) this phenomena (core spinning faster than the rest of the body, in spite of immense friction and in the vacuum of space) produces our magnetic field. When you say there is 'zero gravity' at the center of the earth you are profoundly misunderstanding what gravity is and you're apparently teaching it to students who will continue on with the same wrong thinking you used here.

[@Unknown-07-r6d]

Sir what is the potential energy at the centre of the Earth?

[@ryanwendt1449]

This makes complete sense as a mental experiment. Although I believe that going up and down indefinitely would break the second law of thermodynamics. This would theoretically be a perpetual motion machine. Let’s hypothetically say that you find a planet and deprive it of its atmosphere and all the gasses with it. Then, there would be no air resistance which, in your explanation, would mean that he would continue to move indefinitely. This would be creating mechanical energy from nothing henceforth breaking the preservation of energy theorem. Can someone please explain?

[@yoprofmatt]

Excellent question. We are not violating conservation of energy because the mechanical energy of the person falling comes from the gravitational potential energy of the earth-person system. When the person is moving fastest, its all mechanical energy. When they come to a stop, its all potential energy. (Just like a spring). With regards to perpetual motion, in fact if there is indeed no dissipation of energy at all (no air resistance, no other source of friction, no loss of energy due to sound or gravity waves or anything else), then it would, in fact, be a perpetual motion machine. The person would go up and down forever. (Of course, getting rid of ALL drains on energy is basically impossible.) However, a perpetual motion machine doesn't do us much good, because as soon as you try to extract some of that energy, the motion starts to decay. And therefore the motion of your machine is no longer perpetual. Keep up with the physics! Cheers, Dr. A

[@va9733]

But can we make that type of tool for drill which sustain that high temperature

[@billmcginley]

Hypothetically, how would air pressure at the center of the earth change as you descend?

[@zanick2]

if there is 0 gravity at the center, then there would have to be a vacuum, or would it be a vacuum? hmmm!

[@ramez2775]

Why does the force of gravity decrease as you get closer to the center? Fg = m1m2/R^2 means that as R gets smaller, gravitational force should get bigger. I'm confused why you said it gets smaller as the person approaches the center. You didn't explain why.

[@sreeramsr5035]

It doesnt work like that. There is a separate equation to derive the acceleration caused due to gravity at a certain depth which goes like g'=9.8(1-d/R). Here 'd' is the depth of the hole and R is the radius of the earth. So basically at the centre, R and d becomes equal resulting in g'=9.8(1-1). And hence g' (the acceleration due to gravity at a certain depth) equates to 0. Also, as you are moving down, your 'd' increases which would decrease the value of d/R and subtracting with 1 would give u a lower value compared to the value of g on surface of the earth.

[@ufoengines]

The Gravity Train guys say you can get through the earth this way in 42 minutes. Also the old flick "The Trans Atlantic Tunnel " on You Tube says we had this tunneling tech back in the 1930's! ( True or not, It's a hoot and a half to watch) .The Gravity Train guys also say you don't have to go directly through the earth but just digging shallower tunnels will work as well. Patent 2511979, 3109554, 672256 .

[@luckycharms7232]

You would eventually level out in the center like a pendulum.

[@dumbweeb9865]

We, could probably make a giant clock. Gives me an erection just thinking about it.

[@pradeepvijay1607]

Whether it's amplitude is constant

[@DoubleFaceReal]

Guys , but im thinking , if you cut the hole trough all the earth and you jump in it, what is exactly pulling you down ? i mean there is nothing under you, should you be pulled on the the heaviest side ? , and what if they are equal , would you be able to float in the middle like a magnet trough a copper coil ?

[@UnintendedSheep]

I knew that if a person jumps from one side of the earth, he would keep accelerating downward until that person reaches the center of the earth and then he would slowly decrease in speed until he ends up in the other side of the earth. However, I thought that as time passes he would slow down to the point where this person reaches a speed of zero as well. My thinking towards this is that there is a gravitational pull on either side of the earth that is pointing toward the center of the earth (The core), so if he is being pulled by this force in all sides, would this person (As time passes) be stopped in the core of the earth? As demonstrated by the figure drawn by the professor, I would have expected this person to stop at some point and not continue to fall infinitely.

[@UnintendedSheep]

never mind, seems that people in the comments has agreed with me as well, I guess my idea is true?

[@srinivasanmohan5038]

Dear Prof Matt, I would like to disagree with the argument that the man jumping into the tunnel will keep moving up and down indefinitely. The reason for the acceleration and force to become zero at the center is due to cancellation of the gravity from both sides. In my view, what might happen if someone jumps into the center of earth is that the acceleration due to gravity which is greater at the surface of the earth, will keep reducing towards the center and hence he keeps decelerating (due to force from the opposite side gravity also trying to push him upwards). Free body diagram at any point in his path will explain the phenomenon clearly. So when the person reaches the center, he will have no zero acceleration from both the sides, and he will kind of levitate at the center with downward acceleration (from top of earth) pushing him downwards and upward acceleration (from bottom of earth), pushing him upwards. Both gets cancelled, and he levitates.Hence my argument and disagreement on the solution provided in this video.I might be wrong, if so, please correct my understanding.

[@DumpTown]

No no no no no.

[@chillbeanjosh6778]

the acceleration is alot and at the center the gravity is weak so it wont stop him the center but maybe if it goes on long enough he might stop at the center

[@willj4ck]

"will keep reducing towards the center and hence he keeps decelerating" -> this is wrong. the acceleration amount decreases but he still has acceleration, not deceleration. initial acceleration, let's say 10 m/s2, at first quarter, he has 5 m/s2 which is still positive acceleration, and at the center, he has 0 acceleration with maximum speed. just after he pass through the center, he starts decelerating and deceleration amount increases. when he reach the other side, he has max deceleration with 0 speed and then starts accelerating towards center again.

[@KarthikRajanellai]

great ... but if I claiming down in big ladder and after crossing centre of earth do I feel claiming claming up

[@leo_z0710]

I thought you will get stuck in the center

[@yoprofmatt]

Mr KZbin, Eventually yes, since friction or air resistance ultimately slows you down. Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@rajithakaru]

What about the reverse gravity made from the mass above him as he travels downwards?

[@Nerd_Nonsense]

So the path we will follow through tunnel will be parabola. Cause parabola is the only shape in which we can go back and forth and zero curvature at the centre due to which zero force at the centre of parabola or earth. So instead of straight line tunnel it is actually a curved path (parabola) but y we are seeing it as a straight line tunnel. So this is what we called space time bending.

[@leethediamondninja1210]

There is a black hole size of a grain of sand so yea it pulled the planet together and created gravity

[@yoprofmatt]

Lee TheDiamondNinja, Great comment, thanks. You're making me think! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@leethediamondninja1210]

@@yoprofmatt thanks for the website I always wanted to learn more about space thanks so much, I'm going to subscribe to you

[@kkeen6264]

Do u come out feet 1st or head 1st if u jump in feet 1st ,?

[@marcot5386]

I say you will start to decelerate to such degree nearing the centre that when you pass the centre and continue you won't carry the equivalent velocity to take you the equivalent distance to the opposite surface, and therefore eventually you will continue to shed velocity back and forth and end up finally stuck in the middle, When you are passing through the centre 1st time there is a refreshed start velocity of your journey, you will be carrying less speed than accumulated falling from the surface,

[@DoomFinger511]

For those wondering how he writes on the glass backwards, he isn't. The video is mirrored. In real life the students can see it because it's being projected on a screen above him in reverse so they can read it. He made a video showing this: kzbin.info/www/bejne/i6PXfZehjbWFhLM

[@robvilletto3146]

He floats in middle.

[@mankushsaini1590]

hello sir I have a question that what will happen if i put a turbine at centre and fill the hole with water ..

[@abdulmunim5851]

🤣🤣🤣 Its Alternate answer should be what if turbine generates excess of energy and accelerates the Planet to displace from its orbit .Lol Somehow if it's supposed to be possible then how would you control that large quantity of energy?

[@stevenho2311]

I've always considered gravity to be the effect of one mass on another but in this scenario at the bottom of the hole there is nothing so you are not being pulled by any object? Consider another hypothetical scenario where the earth was split vertically in two and separated by a small gap. Here the gravitational pull would be between these two halves so what would happen if you climbed into this gap? Wouldn't the gravity of both halves acting on you cancel out?

[@unavailableusername9694]

I think you almost answered your first question with your second. In this scenario the bottom of the hole is the center of the earth, the center of earth's gravity. Gravity would be in equilibrium, therefore you would experience zero gravity. However once you fell past it you would begin to decelerate, and the gravity vector would increase as you approach the surface on the other side. Without air resistance you would be moving very fast through the center so that zero gravity thing wont mean shit as you'll pass the center point doing mach something or other and your senses wont have time to realise it. With air resistance you would never exceed terminal velocity as the gravity vector only decreases once you fall below the surface. In either case, conservation of energy would seem to predict you eventually stopping in the center, and floating there. In the case of the split earth, I would think you would still be drawn to the center of gravity, which would be the center point between the two halves if they are close, but they would also have to have exactly the same mass. A difference of a percent or two on a planetary scale is huge, and might cause you to skid along one side or the other on your way to the middle. Ouch.

[@MrBenu95]

When you finish your first "journey", will others see you falling or climbing out of the hole?

[@yoprofmatt]

Benu Liakoz, Great comment, thanks. You're making me think! I guess they would see you climb out and then immediately falling back in. You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@Caprah]

@@yoprofmatt Imagine two points on the globe at exactly the same elevation. Now lets say the distance between them is 111km. lets say the elevations of these two points are both 1000m above sea level. Now if you would imagine a straight line of sight between these two points, you would in fact be cutting through 242m of earth curvature height at the middle between these points. so the middle point on that straight line of sight would have an elevation of 242m less. How would water behave if this line of sight was to be a tunnel / tube? Imagine this line of sight to be a road on which we can travel. imagine this line of sight to be a water canal How can one be traveling in a straight line of sight between same elevations but change elevation magically to and from the center point? This argument stands to be the case for any length of road long enough to have curvature. How do I understand that if it was a water canal, the sides of the canal have to be 242m high in the middle to contain the water? Remember that we are moving from and to the same elevations in a perfect straight line

[@behnamasid]

Futuristic way of creating free energy.

[@yoprofmatt]

Bingo. Cheers, Dr. A

[@deiselgas]

If all radioactive decay ceased, would all earth's heat escape to space or would the core remain hot purely due to compression?

[@nate2187]

Seems to me the closer you get to the center, the less gravity due to more mass existing more and more in every direction, until you get to the center where there is no gravity since it cancels out. Hence, compression becomes less and less the closer you get to the core. I would think the center of the earth has to be super cold because there's no sunlight either and any radioactive decay is occurring in the crust and isn't enough to heat the mantle and core of the earth to the high degrees of temp taught in most textbooks.

[@eliswickman2803]

Would the air in the tunnel be thinner closer to earth’s center, just like the atmosphere gets thinner the further away from earth you go? And if so, how thin would it get? Would you still be able to breathe or would it be closer to the outer layers of the atmosphere?

[@yoprofmatt]

Elis, Good question, and one I hadn't thought about before. In fact, the air would be even thicker at Earth's center, since you have a larger column of air above you (the radius of the earth plus the height of the atmosphere). Even though gravity gets weaker as you descend from the earth's surface, it is still pulling towards earth's center, meaning that the entire column of air has weight. This could, actually, be a pretty big number since earth's radius is much greater than the height of the atmosphere. I'll have to think about how to exactly calculate this and then I'll try to make a follow-up video. Thanks again for the great question. Cheers, Dr. A

[@sunnysharmi495]

When you are on the surface of the earth u experience gravity of 9.8m/s2......that means when come to to other side of the earth through a hole on to the surface u can actual feel gravity of exactly 9.8 .....if some one helps u to grab out of the hole u can easily come out of the hole

[@yoprofmatt]

I agree. Cheers, Dr. A

[@valeriofabrizi613]

What happens if you make a hole through the Earth? In the most realistic case, you´d end up creating two volcanoes which magma chamber has a straight-lined shape. Anyway, nice video :)

[@va9733]

But hw can u make hole through out tool cant sustain temperature 1st

[@steffenleo5997]

Great videos Prof Anderson...👍👍

[@av4787]

If we dig a hole, we are technically also cutting the earth in half. What would happen at that point?? Any answers???

[@mustafakhan940]

What if you dug a U-shape instead that just touched the core of the Earth, then came back out to form a semi-circle?

[@yoprofmatt]

Mustafa Khan, Great comment, thanks. You're making me think! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@chalkwitch471]

Wow! The ultimate Bungie jump!

[@yoprofmatt]

And without the bungie! Cheers, Dr. A

[@husseinhayek3945]

Why do gravity pull us towards the center if gravity is a curvature in space time ???

[@matte6352]

Haidar Hayek3 because the earth has mass

[@MrGamerfreak17]

My question is.. How did he write on the board from what presumably looks to be backwards from his position.

[@yoprofmatt]

+Jack Gronenthal Jack, this is the most popular question. You can uncover the secret at learningglasssolutions.com Cheers, Dr. A

[@eshubitcoin9458]

What if we install hyperloop it can accelerate a lot of speed and push into the space

[@skyefairy7119]

thanks I always been wondering this.

[@siyonasingh5421]

Thanks !! Isn't the force from down large enough for the person to never reach the bottom of the earth and to remain at the centre of the earth. Why doesn't the person remain at the centre because both the forces are acting at the centre of the earth ?

[@ajeyrathod1347]

The momentum is high enough to push him beyond the centre of earth but considering all dissipation forces he would be set in oscillation for some time eventually stopping at the centre point of earth

[@jesterlex5786]

I have never taken that class and I predicted his shit tf am I doing i should be in the fucking nasa

[@bobbybrady8]

So with the air resistance, does he eventually just stop in the middle then? If he keeps losing speed he would start to not see the ends of the tube and resistance would keep him further and further away from the openings (closer to the center). Like a bouncing ball that can bounce through glass but eventually has to settle in the middle.?????

[@DumpTown]

The thought experiment is hypothetical - as stated explicitly in the first 10 seconds of the presentation - and ignores air resistance. Good grief.

[@derpeth2101]

Ok, but what if you modify the hypothetical experiment to include air resistance?

[@hendryparker6237]

u forgot coriolis effect professor

[@Constantinesis]

Isnt this just a kind of linear pendulum?

[@yoprofmatt]

Yes, I suppose it is. Cheers, Dr. A

[@frankjeschke2471]

Harmonic oscillation

[@carultch]

@@frankjeschke2471 It would be simple harmonic oscillation, if you accept the approximation of a uniform density Earth. Because the restoring force would be proportional to the distance from the equilibrium position. The period of this oscillation would be about 84 minutes, for a round trip returning to your origin. Notice how close this is to the orbit period of the ISS, which is 92 minutes? A surface level circular orbit would also be 84 minutes if it were possible, and there is a mathematical relationship between this thought-experiment oscillation, and orbits in general. In reality, Earth is not uniform, and is much denser the deeper you check. This would skew the oscillation pattern away from a sine wave, steepening the zero-crossing parts, and flattening the turning points.

[@yassermustafa4860]

What if the tunnel does not pass through the center of the earth? does the period stay the same?

[@yoprofmatt]

If the tunnel doesn't go through the center, then you can't fall straight through. You would hit the sides. In fact, our current tunnels on Earth (like a car tunnel) don't go through the center, and you're sort of stuck to one side of the tunnel (the road). Cheers, Dr. A

[@diamondgulamhusein6637]

yes.The period will remain the same.

[@victorliebenberg2803]

Great teaching

[@abdelmoneim3796]

Just like shooting a bullet to the sky It will fall back at same speed

[@okienationoutdoorstheblake835]

You would come out of the whole at the same height as you went in. So his entire body would come out the other side. Not just his head and shoulders as the professor suggests.

[@ryanwendt1449]

Allen Blakey I think he was estimating the effects of air resistance as this mental experiment was about earth.

[@sambitghosh6811]

Is acceleration due to gravity always taken negative

[@yoprofmatt]

Just depends on your coordinate system. Gravity is always pointing towards the center of the planet or star. Typically when we do physics problems on a small scale, like the motion of a baseball, we are sitting on the surface of the earth (which appears to be pretty flat). If you draw a Cartesian coordinate system on the surface of the earth with "up" being positive, then gravity will point "down" or negative. Cheers, Dr. A

[@XSnipersArmyX]

LOL me and my friend had the same question while we were drinking beer. Mind Blowing

[@yoprofmatt]

Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@aka1944blue]

if some one jumps in the other side as you have jumped in your side, Does that mean you pass in the middle so you are going down as he is going up. Is that a paradox. How can you fall down when he is falling up.

[@yoprofmatt]

Correct. Of course there's no real up or down, there is only radially outward or radially inward. Cheers, Dr. A p.s. If Dr. Anderson and Dr. Einstein jump into the whole from opposite sides, then that's a paradox!

[@sameervyas8375]

Would it do SHM (assuming idealistic situation)

[@yoprofmatt]

Evil Assassin, Yes, since the force is linear with distance from the center of the earth. Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@francescaa8220]

What happens if it’s the exact same situation but the tunnels off centre

[@yoprofmatt]

Francesca A, Excellent question. First point: we are assuming the earth is not rotating. That changes things. Second point: If the hole is off center you will hit the wall, since the force is always directed towards earth's center. Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@vscs7415]

Soo with this we can put a coil and throw a magnet then boom we have electricity forever?

[@mankushsaini1590]

and also its assumed that when water is there then their is no air

[@navaniganavaneethan3152]

awsome teaching

[@yoprofmatt]

Navaniga Navaneethan, Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@Betehadeso]

I just did a quick check on Quora and it seems I am right and this man's hypothetical answer is incorrect :-/ curious to know what you guys think...

[@rajbagwe3732]

I don't know much, about these things, but I think the person should stop at the centre after many ups and downs. Once the person goes down, it should cause the centre of gravity of earth do move down a little bit... This means that while going back up again, the acceleration due to gravity must be a little bit lower. This effect would eventually cause the person slow down so much that he would be practically vibrating near the centre...

[@mefeyz]

Is there any depth of the earth, in between the surface and the center, where the gravitational force becomes zero again?

[@carultch]

No, there are no points inside the Earth, other than at the center itself, where the gravitational field is zero.

[@mirfanessot298]

💯💯💯💯💯💯❤️❤️ Sir you have unique way

[@yoprofmatt]

Appreciate that. Hope you're finding these useful. Cheers, Dr. A

[@infinxtezen7260]

This kinda blew my mind

[@yoprofmatt]

INFINXTE ZEN7, Great comment, thanks. You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@ashneetkaur7125]

What will happen if we pass a ball through the hole?

[@bibekshrestha9295]

what it we can catch his leg and pull him out from other side?

[@yoprofmatt]

That's called human fishing. You get to keep him. Cheers, Dr. A

[@holdencaulfield4152]

Is it possible to make this stuff to another planet and then we would gain an unlimited power? 😮

[@qiutyeet4810]

wound't he also disintegrate from the heat or maybe gravity it gone entirely?

[@Betehadeso]

in the previous video it was hypothetically put forward : how about if there was no issue like heat etc...

[@GAMESTERVISION]

Conservation of energy weeks make him stablize eventually at the center

[@zanick2]

no

[@Alextm899]

Nop he ..... he will vanish. Never come out from the other side. And if you dig this hole humanity will be lost the planet terra will no more exist.

[@Kenn_zou]

forget the explanation. did he just wrote those words in reverse on his perspective?😅

[@surajsugunan3368]

what if the hole made through " y " axis?

[@yoprofmatt]

Not sure what you mean by "y" axis, but any axis that does not go through the spinning axis (roughly North and South pole) will lead to the object hitting the walls of the tunnel as it falls. Cheers, Dr. A

[@joebill48]

the jumper would slow down gradually and come to rest at the absolute center of the earth where he would be weightless. this is due to the gravitational pull of the mass of the earth pulling back on him from where he started gradually negating the force downward. this can be proven by going into a deep mine and comparing surface weight and weight at the bottom of the mine. also note that the jumper is not pulled sideways in the tube because of the balanced pull from the sides which stays constant. the bad news is that the inner core is hotter than the surface of the sun. my question is wouldn't the lack of gravity at the center make it liquid not solid?

[@DumpTown]

So many misconceptions here it's impossible to know where to begin.

[@jimpringle1634]

@@DumpTown the key is that acceleration approaches 0 as you near the center. Velocity is a separate value.

[@BakeAnCake]

Why am i watching these videos at 4am

[@HydroluisDrainage]

lets to test it )

[@NVRLTLLTHATRUTH]

There is no center of this flat ASS EARTH......

[@9xlog387]

Ain't there a movie about this?

[@yoprofmatt]

There is of course Jules Verne's "Journey to the Center of the Earth" and the 2008 movie of the same name. Maybe not as entertaining as my little stick figure drawings, though. Cheers, Dr. A

[@mr.scientist7205]

It's actually a foolish question 😑😑😑

[@deepakalexkollam703]

If I drill a hole through the center of the earth and to an occasion . then the water come through the hole? is that oscillate? consider the water is continues .

[@DumpTown]

Good grief.

[@surendrakverma555]

Good

[@yoprofmatt]

Thanks

[@lydiajoseph6029]

😂😂😂 Imagining such a situation

[@yoprofmatt]

Higgs Boson, Thanks for the comment, and keep up with the physics! You might also like my new website: www.universityphysics.education Cheers, Dr. A

[@abdulmunim5851]

hmm what is your purpose of writing Higgs Boson here?

[@rajbagwe3732]

[REDACTED]

[@Peter_1986]

If there were no energy loss anywhere, then the person would convert his potential energy with respect to the Earth's centre into kinetic energy, and then that energy would be converted back to potential energy when he reached the other side, and this would have continued forever. However, all real scenarios involve energy loss, so he would eventually stop in the centre.

[@rajbagwe3732]

@@Peter_1986 Yup, that was a younger 9th grade me who had absolutely no idea what he was talking about. Omg I am so embarassed with what I have written in that comment. Sorry for wasting your time with that. I am studying advanced physics now in 12th grade btw.

[@aleksandardonski2670]

Dear Mr. Anderson, I saw with pleasure your video and I understand your explination. However I have a question for which I still can not find an answer (although I asked several people). I shall try to explain my question. Although it is impossible in practice to dig a hole through the Earth, let's imagine that some person can dig a hole and pass to the other side of the Earth. I have read that if someone will start digging in China, he will appear in Argentina. So let's imagine a person starting to dig a hole in China. Normaly, he will stand on the ground (on his legs). Now let's imagine that one day he will appear in Argentina. My question is: in what position will be his body when he will appear in Argentina? You suggest that he will come out of the ground with his legs toward the sky in front of the people there standing around him. This means that somewhere during his digging he will change the position of his body (he will start digging with his legs toward the ground and he will finish the digging with his legs toward the sky). Also, if he will come out in Argentina with his head toward the sky, this again means that somewhere, while digging through the Earth, the position of his body will be changed - he started digging with his legs on the ground and he will appear on the other side with his head toward the sky (which means that in some point of his digging, instead to dig in the ground, he will dig toward the sky, which again means completely opposite position of his body). So my question is why, where and when will his body position be changed (upside down) during his digging through the Earth? Regards, Aleksandar Donski

[@yoprofmatt]

Good question. It's at the center of the earth. Imagine a person digging in China, feet first, all the way to the center. Another person digging in Argentina would also dig, feet first, all the way to the center (by symmetry). (Note that the gravitational force gets weaker and weaker until it is zero at the center.) Thus they would meet feet to feet. If the hole above the Argentina digger was now filled in, he/she would have to climb and dig, hands first, as if it was the roof of a cave. Cheers, Dr. A

[@aleksandardonski2670]

@@yoprofmatt Thank you for your reply Dr. Anderson. I think it will be good this to be explained with some animation as well (or drаwing as it is in your video). For us laics it is not easy to understand and imagine… For example, lets’ imagine a ball large as a building made of rubber. If someone will fire a bullet in it, that will pass through the center, the bullet will appear on the other side in the same position (with its’ “peak” forward) as it will enter the ball. But regarding the Earth it is not a case. If we imagine a bullet shaped capsule with a man in it that will dig a hole (with its’ “peak” toward the ground), I understand that when it will arrive in the center, the gravitation will be zero and they will float, but for me it is hard to imagine graphic how will this capsule continue digging after passing through the center, i.e. how and when exactly it will change its’ position and continue digging, this time, with its’ “peak” toward the sky until it will appear on the other side. Regards, A. D.

[@ahcrapohunkx9951]

This is a little too simple, or at least too short. Idk what is wrong with the class... leads to a lot of questions. Wouldn't there be issues of time displacement, and wouldn't it be impossible to actually reach the exact center causing some kind of infinite acceleration or at least rotation on the man when near it? Lets say he slowed down enough to reach the center, wouldn't it cause him to spin, wouldn't that spin be nearly infinitely increasing, and wouldn't him leaving that spin cause a time displacement? If he was able to travel straight through in a vehicle that kept a constant speed, wouldn't there be time displacement there too just because he passed along a serious gravitational bend? How would it be different than traveling around the earth in a space ship?

[@alphad3rp630]

Wouldn't the person not come even close to reaching the other side due to terminal velocity? I would assume that in comparison to the length of the hole in the Earth that a person would hit terminal velocity pretty early, giving them not nearly enough speed to reach the other side.

[@genkins23]

i think he will slow down then fall to the upperside then falls down again till he is stuck in the middle in the core

[@DumpTown]

What causes terminal velocity? Air resistance. The thought experiment is hypothetical - as stated explicitly in the first 10 seconds of the presentation - and ignores air resistance.

[@joelwhitbread6387]

Perpetual motion

[@progaming-sm1kx]

Don't you think the man might just float and stay stuck in the centre instead of moving like that?

[@DumpTown]

No.

[@jorgejimenez4325]

Yes he would stay stuck as the oscillations shrink until he is in suspension at the center of the earth

[@kskillerstudios3163]

Thanks for this video sir... Thank you so much