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Consider my example below. Example: 1. A man standing on grass(point) on earth surface. 2. He jumped. 3. And returned back, and he could find the same grass(point) under his foots. Right?

If earth is spinning, when he is on air (on jump) and return back to the earth surface, the grass(point) should be moved right or left side based on rotating direction of earth Right. But it did not happen on real scenario.

Newton told that as "Gravity". and the definition would be the force that attracts a body towards the centre of the earth, or towards any other physical body having mass.

But from my example the man attaching with a earth surface by some force due to not only of earth's massive body, but also for it's spinning.

Because If gravity only about to mass means the man return back to earth surface is OK, but how could he feel like settle down on same place on earth surface that he stood before he jumps.

I am really curious about the answer.

Qmechanic
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Saravanan
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  • Essentially a duplicate of http://physics.stackexchange.com/q/48287/2451 , http://physics.stackexchange.com/q/80090/2451 , http://physics.stackexchange.com/q/137191/2451 , http://physics.stackexchange.com/q/1193/2451 and links therein. – Qmechanic Aug 04 '15 at 18:13
  • Suppose you are traveling on a bus at 30 mph, and you are standing up. Now you jump straight up. Where do you land? The man on the grass is also on a bus, that is traveling 1000 mph to the east. In fact he is traveling 70,000 mph to get around the sun in 1 year. In fact he is traveling 5 times that around the center of the galaxy. Who knows how fast the galaxy is traveling, relative to others? – Mike Dunlavey Aug 04 '15 at 18:20
  • @Mike Dunlavey I cannot get your point clearly. Could you please read the comments I added with the Jahan claes and tell me if I am wrong about my intuition. Thanks. And as it give some additional info, it is not a duplicate question. – Saravanan Aug 05 '15 at 05:09
  • @Saravanan: 1) You are courageous to try to write this much English when it is not your first language. 2) Still, I am having difficulty understanding your intuition. I understand a person doing a vertical jump and landing in the same place relative to a moving earth. You seem to see a difficulty with this, and I do not. – Mike Dunlavey Aug 05 '15 at 12:20
  • @Mike Dunlavey: Did you read comments attached with Jahan's answer below. In conclusion, From your comments also I can only understand that there is a force(caused by earth spin) only attaching objects with earth. Since we are attach with earth we are also spinning (travelling) in earth speed. So only he could come back to his previous state. Right? So here I cannot see any definition of gravity(obj in higher mass pulls mass in lower). The man came down because he attracted or pulled force caused by earth spin. Is it correct? – Saravanan Aug 05 '15 at 13:27
  • @Saravanan: The man coming down is not caused by spin. It is caused by attraction between earth and man. There are two things working here: Newton's first and second laws. The first law is why the spin/speed does not matter. The second law is why he comes down after going up. – Mike Dunlavey Aug 05 '15 at 16:08
  • 1.What would happen if you stand(at circular platform) near to the train which is moving in circular track?Won't you feel like you yourself pushed towards train?2. Black hole is spinning very fast so it will pull even a light particle towards it,accept?.But all are saying black hole is spinning very fast as it has more gravity,but for me it is not true.While spinning at some constant rotating rate there is sudden change in atmospheric pressure on it's surroundings with respect to the spinning rate. continueing in next comments. – Saravanan Aug 05 '15 at 19:38
  • Similarly object near to earth(or black hole) in low atmospheric pressure, more or less will feel like flying pushed towards earth.So for our movement to any direction, we need same energy or force in space, Right? but you will feel the difference in energy or force while you make movement in upward direction than your side movement. because you are trying to detach with earth. If you have some more amount of energy and force you can travel in upward direction, but at one point you will be detached with earth atmosphere,so you will not be spinning with earth.So your time will vary. Continue.. – Saravanan Aug 05 '15 at 20:01
  • When will you come to earth you will feel different in time (The time when you not attached with earth, earth could complete it's rotation to sun or spinning itself which is consider as TIME in earth) also in evolution growth(Your atmospheric changes). This might be the reason for TWINS PARADOX. But they are telling if you travel at light speed,when you returned to earth you will feel time dilation,that I am not able to accept, is it possible?...continuing in next comment – Saravanan Aug 05 '15 at 20:21
  • Then about gravity definition The object more in mass will pull the object less in mass- Then I will take a rock 10 times more mass than me in space ship in space travel and throw it on space. Do you think I can settle on that rock safely in space?. Please correct me if I am wrong? – Saravanan Aug 05 '15 at 20:22

1 Answers1

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What you have to realize is, both the man and the ground beneath him are travelling at the same speed. What that means is, yes, the ground underneath the man is travelling east very quickly, but the man is also travelling east just as quickly.

The gravitational force causes the man to come back down, but it has nothing to do with making sure he stays over the same point on the earth's surface. He will ALREADY stay over the same patch of earth, due to his speed eastward.

Jahan Claes
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  • Folks please understand my question clearly and erase the existing definition about gravity prior to answer it. To return back to the same place (on grass here) there are two consideration 1. Mass 2. The man always attaching with the spinning earth with force due to spinning. even the man is in air he is attached still with that force..and he will be ditached when he travel crossing the limit of the force due to spinning. Everything seems to be perfect here without gravity.. I cannot agree the definition of gravity here. – Saravanan Aug 04 '15 at 19:38
  • @Saravanan I think the important thing to understand is that gravity has nothing to do with pulling the man eastward. Perhaps a simpler example: if you're on a fast-moving train and jump, you'll land in the same place you jumped from. Gravity doesn't make you "stay with the train" at the same spot you jumped from. It's just that you already had the same velocity as the train when you jumped! Thus, nothing needs to give you velocity in order to stay in the exact same spot. – Jahan Claes Aug 04 '15 at 19:51
  • For me it seems gravity is not at all be a force. Why?Which makes me to think like this. 1. we should not stand near to running train. ok. Now you yourself assume that train track as circle. people stand near to moving train at platforms. What would happen now? people standing in circular platform will feel like they are attracted by train, in this case Right? Now assume train moving circular path is EARTH and people around that is standing in SPACE. Example in my question same as like this, Right. – Saravanan Aug 05 '15 at 04:48
  • The man is on air(while he jumps)is still attaching with a spinning earth.Since he is a movable object he could jump.Even he is able to jump, he is sill within a force that is similar like distance between running train and people in platform.That force caused by spinning earth, but when he crossed that boundary of that force,he will feel earth is spinning but he is in rest that is similar like people stand far to the running train.So conclusion is we are attached with the earth not only relative of MASS but also relative to the earth spinning.As def for gravity failed here,its not a force – Saravanan Aug 05 '15 at 05:05
  • Here is a link that added value for my intuition. Einstein also felt difficult while relating his relativity theory to the newtoniam gravity and felt that there is no force as GRAVITY actually. According to Einstein E=mc^2, we need energy E to move object with mass m to a light speed c(velocity limited to light speed here). Newton also state that F=ma, we need force F to move object with mass m to some acceleration a. Both left some points here which is important here.I will continue this scenario with next comment. – Saravanan Aug 05 '15 at 10:00
  • From their statements they are telling same thing with different name ENERGY AND FORCE. So according to me, 1. The movement of Direction -Object on earth can feel easy while they make movement in left or right or front or back so energy or force needed here is less. But when the Object make movement in top, it will not be that much easy(because the object is already attached with the force see my train example in above comments) 2. And distance between object and attached reference-If the distance is more,at one time obj will detach from the attached reference. – Saravanan Aug 05 '15 at 10:19
  • So energy or force needed will be differ based on the 2 points mentioned in above comments plus mass with respect to force caused by it's attached frame or object. In other words we can say, direction and distance will affect the Energy or Force. And I mentioned the reasons also in above comments. Please correct me if I am wrong :). And I have still more facts that make me to feel I am Correct about it(there is no force as gravity). – Saravanan Aug 05 '15 at 11:55