I understand that as the distance between the planet and the body increases, the gravity decreases, but how can they still just 'float away'?
20601
Well, this question has been puzzling me for kinda long time, many people believe that orbiting astronauts feel weightless because they are "beyond the pull of Earth's gravity"...How far from the Earth would a spacecraft have to travel to be truly beyond the Earth's gravitational influence? If a spacecraft were really unaffected by Earth's gravity would it remain n orbit? If so, what is the real reason for weightlessness in orbit?
114702
Newtons law of gravity for two particles of mass $m_1$ and $m_2$  is:     $G\frac{m_1.m_2}{r^2}$.    Supposing that the particles are point particles then gravitional attraction will bring them closer together, and in fact infinitesimally closer together. Now in Newtons time there was no theory, as far as I am aware of inter-atomic forces that would have kept these two particles apart, so the gravitional attraction is asymptotically infinite. This is nonsensical, and either one can say that point particles cannot arbitrarily approach one another, or that particles can never be point particles and must have extension - this in fact includes the previous solution, as the notional point positions of the centre of mass of a particles with extension cannot obviously approach one another.  In Classical Mechanics, would this have counted as evidence of either particles cannot be point masses; or of some then unknown repulsive force that acts at very small distances.  What does the historical record show?
101347
Imagine we have cup A with 50&nbsp;g of water and cup B (smaller in width than A) with 100&nbsp;g of water. Now put cup B into cup A. If the width of both cups are of comparable size then the cup with 100&nbsp;g of water floats. It does not touch the bottom of cup B.   Now think about  of flotation. It says that the weight of displaced liquid = weight of the floating object. However in this case the bottom cup has only 50&nbsp;g of water. How can an object float without displacing water equal to its own weight? Am I not applying Archimedes principle correctly or because of both things beings of comparable size Archimedes principle does not apply?
83168
For years I have been very fascinated by the "mystery" aspect of gravity. Functionally, we understand it for our applications, but in my (limited to my 3 quarters of undergrad general physics) understanding, we don't know why it exists or how the "pull" works.   To provide an example of what I mean: there has to be some "measurable material" of gravity between, say, the earth and the moon -- some kind of 'graviton' (not that it needs to be a particle or anything, I have zero claims as to the nature of how gravity does what it does). The [butchered] saying of "pluck a flower and move the furthest moon" originates because gravity in theory, has an infinite range (right?) and moving a flower on earth could maybe move an atom on Jupiter ever so slightly.  Anyway, similar to how we had "very good" hypotheses about the existence of Higgs boson that the LHC 99%+ confirmed, do we have any "very good" hypotheses in regards to the fundamental way how gravity does what we have long-known it to do?
24219
As far as we know, the particles of dark matter can interact with each other only by gravitation.  No electromagnetics, no weak force, no strong force.  So, let's suppose a local slight concentration of dark matter comes about by chance motions and begins to gravitate.  The particles would fall "inward" towards the center of the concentration. However, with no interaction to dissipate angular momentum, they would just orbit the center of the concentration and fly right back out to the vicinity of where they started resulting in no increase in density.  Random motions would eventually wipe out the slight local concentration and we are left with a uniform distribution again.     How does dark matter form lumps?
7117
When I'm rotating, I feel centrifugal force. But if I were the only one in the universe and rotating, wouldn't I just kinda be still (since I'm not rotating with respect to anything) or would there just be a force pulling me out? What if there were another person a billion miles away, this should not change anything, right?
58640
Gravitational wave is produced by change in gravitational field, . If something is moving away from me at constant speed, its gravitational field will vary. But why only accelerating bodies produce GW?
17142
I had a recent conversation with my girlfriend, who is a physics grad student. She was kind enough to listen to me rant about an idea concerning escape velocity. Unfortunately, I am still thinking about this question, but don't want to bother her with it.  My thought is that we shouldn't actually need to reach 11km/sec to leave the earth's gravity. Instead of this, can we simply apply enough force to overcome earth's gravity without reaching that speed? How we would do this is not a part of my question.  Orbital altitude is $99$ miles. Travelling $60$ mph straight up should get you there in $1.65$ hours, granted you have enough force to push. I know some of the simpler math like $F=ma$, but that didn't help me understand.  I browsed some articles about space elevators and couldn't find my answer.  Then I thought about a regular elevator and the fact that it has enough force to move it away from the earth successfully. Even if the elevator moved at $1$ nanometer/sec, it would still move away from the Earth, overcoming the minute pull of gravity at that altitude.  If you missed it, my question was:  can we simply apply enough force to overcome Earth's gravity without reaching that speed?  Edit: In another example, let's say we could drive a car from here to low Earth orbit. As long as we had enough torque, we should be able to overcome gravity, much like a pickup truck pulling a bunch of lumber. Is that correct?
5603
The idea that as you move through the earth you get a symmetric cancelling of gravitational acceleration which approaches zero acceleration due to gravity at the center of the earth makes a lot of sense I think. I also think that is a pretty easy idea to understand physically.  On the other hand, I am just beginning to study and understand the general relativistic explanation for gravity and I'm wondering how this same idea is explained using general relativity. That is, what is the explanation for why gravitational acceleration decreases (linearly if I'm not mistaken) as you approach the center of the earth using general relativity? Specifically, I would like to understand what is going on with the curvature of spacetime in this scenario? Is it becoming less curved? Some math would be appreciated in answers!
92359
My possibly mistaken understanding is that  changes with time, whereas a  is, well, constant.  What about gravitational clumping? Detecting relative motion?
62664
Consider the experiment in .  The experiment includes using a ruler as a lever, with an inflated balloon on one side and a balloon which is not inflated on the other.  The aim of the experiment is to show that air has mass.  I have seen many kids performing similar experiments.  But, if the air pressure inside the balloon is equal to that outside, then the buoyant force will cancel out the weight of the air inside the balloon, won't it?
70325
When there is a film of water in between an object and the tabletop it rests on, it is difficult to pull the object directly upward. However, when you slide the object, it comes off easily. What is the physics behind this?
19205
The following is written in my textbook as the reason for weightlessness felt in satellites:     The gravitational pull is counterbalanced by the centripetal force.   This introduces two problems:   For satellites orbiting around Earth, gravity is, in fact, the centripetal force. If the gravitational pull and centripetal force on a satellite are both in the same direction, then how do they cancel each other out?
95049
If an object is, say, 100 cm. from a wall, and I move the object halfway to the wall and stop, then the distance is reduced to 50 cm. If I continually move the object by one half of the remaining distance and stop, and keep repeating this procedure, why is it that the object eventually makes contact with the wall (on a macroscopic level at least), considering that no matter how infinitely small the remaining distance is, I can theoretically cut that distance by half, and thus never reach the wall. Does the Planck distance, the theoretically smallest unit of distance, have anything to do with this? And if so, how does any object get "around" that infinitely small Planck distance in order to move at all?
24928
According to General Relativity I am being accelerated upwards by planet earth while writing this question. But a curious person on the the other side of the planet relative to me would have the same experience. That means we are accelerated in opposite directions, although earths diameter do not seem to increase. How can this be?
55258
If I remember well, they said that it can't, but I do not know why.  Yes, I meant if gravity can be shielded using something like a Faraday cage (or something else?).  Thank you.
90871
I've recently been contemplating things like artificial gravity in a rotating space ship (for example, the ) and learning about the Coralis effect and other interesting fictitious forces that appear in rotating reference frames.  It occurred to me that, if you were living on a space station spun for artificial gravity, it might be possible to become weightless in such an environment by travelling fast enough against the spin of the ship. My friend, who I was discussing this with, thinks otherwise, that you would actually be under more g's as you tried to gain the speed to lift off from the inner edge of the ship.  In terms of concrete numbers, say the ship is 4 kilometers in radius (as an O'Neill Cylinder would). At this size, the rate of rotation to generate 1g in centrifugal force (the artificial gravity) is under 0.5 rpm. If a vehicle travels on the inside of the cylinder against the spin fast enough, eventually the vehicle would cease moving when looked at from a static reference frame. I would think at this point, the vehicle could simply push off from the edge of the cylinder and float towards the center of the station. Is this correct?  Furthermore, would this method of "getting into air", as it were, be easier than it would be to counteract real gravity on Earth (with things like planes that generate lift with their wings)?