asd2791 Posted March 8, 2017 Share Posted March 8, 2017 Question: if there was a tunnel from the north pole to the south pole, then we threw anything in that tunnel, where will this thing go ?!!! Is that thing will come out from the other side? or will stop in the middle? Link to comment Share on other sites More sharing options...
Bender Posted March 8, 2017 Share Posted March 8, 2017 Air drag will slow it down considerably, so it won't come out the other side. Your object would also melt. However, if you managed to pull the tunnel vacuum, and you manage to avoid the object hitting the sides of the tunnel, your object would get close to the south pole. However, the south pole is 2,835 metres above sea level, while the North pole is at sea level, with the ice only a couple of metres thick. This means that your object would be almost 3 km short. Reversed, dropping an item in at the South pole, it would shoot out the North pole at considerable speed. Link to comment Share on other sites More sharing options...
Raider5678 Posted March 8, 2017 Share Posted March 8, 2017 Air drag will slow it down considerably, so it won't come out the other side. Your object would also melt. However, if you managed to pull the tunnel vacuum, and you manage to avoid the object hitting the sides of the tunnel, your object would get close to the south pole. However, the south pole is 2,835 metres above sea level, while the North pole is at sea level, with the ice only a couple of metres thick. This means that your object would be almost 3 km short. Reversed, dropping an item in at the South pole, it would shoot out the North pole at considerable speed. There's an interesting video on that too. Link to comment Share on other sites More sharing options...
Strange Posted March 8, 2017 Share Posted March 8, 2017 Reversed, dropping an item in at the South pole, it would shoot out the North pole at considerable speed. Although, in both cases, it would fall back again and oscillate about the mid-point. With air resistance it would eventually stop in the middle. (This ignore imperfections, the rotation/precession of the Earth, the heat at the centre, etc.) An interesting point is that it would take the same time to fall through and out the other side as an object in orbit (at the same starting altitude). 1 Link to comment Share on other sites More sharing options...
Lazarus Posted March 8, 2017 Share Posted March 8, 2017 Question: if there was a tunnel from the north pole to the south pole, then we threw anything in that tunnel, where will this thing go ?!!! Is that thing will come out from the other side? or will stop in the middle? My math professor described what he called the Wexler mail system. With frictionless holes through the earth between cities around the world, you could drop your letter in a hole and not only would it come out on the other side of the earth, the time it takes is the same for all holes. Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted March 8, 2017 Share Posted March 8, 2017 Frictionless is the key. It can't avoid the sides...the darn Moon makes sure of that. Link to comment Share on other sites More sharing options...
asd2791 Posted March 9, 2017 Author Share Posted March 9, 2017 Certainly the assumption exclude air, Friction, heat, and sea level. The question is about the behavior of gravity . It seems that the correct view is: in the end it will stop in the middle. Link to comment Share on other sites More sharing options...
Bender Posted March 9, 2017 Share Posted March 9, 2017 Certainly the assumption exclude air, Friction, heat, and sea level. The question is about the behavior of gravity . It seems that the correct view is: in the end it will stop in the middle. Not if you exclude air and friction Link to comment Share on other sites More sharing options...
asd2791 Posted March 10, 2017 Author Share Posted March 10, 2017 I think get thus: Link to comment Share on other sites More sharing options...
Strange Posted March 10, 2017 Share Posted March 10, 2017 I think get thus: Not if you exclude friction and air resistance. Link to comment Share on other sites More sharing options...
zapatos Posted March 10, 2017 Share Posted March 10, 2017 Not if you exclude friction and air resistance. For the same reason planets continue to orbit? Link to comment Share on other sites More sharing options...
Strange Posted March 10, 2017 Share Posted March 10, 2017 For the same reason planets continue to orbit? Exactly. Although that raises an interesting question about whether tidal forces or general relativistic effects (frame dragging?) need to be ignored as well. Link to comment Share on other sites More sharing options...
DrKrettin Posted March 10, 2017 Share Posted March 10, 2017 I had a question about the first response to the OP: However, if you managed to pull the tunnel vacuum, and you manage to avoid the object hitting the sides of the tunnel, your object would get close to the south pole. However, the south pole is 2,835 metres above sea level, while the North pole is at sea level, with the ice only a couple of metres thick. This means that your object would be almost 3 km short. Reversed, dropping an item in at the South pole, it would shoot out the North pole at considerable speed. I had always understood that the physical centre of the earth was not quite the same as the gravitational centre, and that there was a 20 km difference. I can't find any reference to this - but if correct, this might alter the response above. Link to comment Share on other sites More sharing options...
Janus Posted March 10, 2017 Share Posted March 10, 2017 For the same reason planets continue to orbit?And assuming you could put an object in orbit around the Earth at just above the surface, it would complete 1 orbit in the same time as the dropped object would take to complete a round trip.(Under ideal conditions: Spherical Earth of uniform density, no friction or air resistance, etc.) Link to comment Share on other sites More sharing options...
Strange Posted March 10, 2017 Share Posted March 10, 2017 (Under ideal conditions: Spherical Earth of uniform density, no friction or air resistance, etc.) And the "object" was a spherical cow of near zero mass. Link to comment Share on other sites More sharing options...
Bender Posted March 11, 2017 Share Posted March 11, 2017 I had always understood that the physical centre of the earth was not quite the same as the gravitational centre, and that there was a 20 km difference. I can't find any reference to this - but if correct, this might alter the response above. It would indeed alter the response if the difference was along the North-South axis. I would be surprised if it is that large, because I would think only the crust can cause such a difference and the influence of the crust is rather limited. I could be wrong. Link to comment Share on other sites More sharing options...
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