Since gravity is several orders of magnitude weaker than the rest of the fundamental forces, the force of gravity acting on a single particle is almost *nonexistant. Since there is still a lot left for us to learn about gravity, is it possible that the force is fundamentally undetectable on a quantum scale? Does the Planck distance even correctly apply to this type of situation?
107402
With the announcement of the detection of gravitational waves, questions about the implications proliferate.  Some relate to the possible existence of gravitons.  The analogous relationship between gravitons/gravitational waves and photons/electromagnetic waves is frequently mentioned.  The detection of individual photons required experiments of very low intensity light, yet their existence was inferred (prior to their actual detection) by Planck and Einstein (among others) using the properties of experimental black body radiation and the photo-electric effect.  If the prospects for detection of gravitons requires similar study of very low intensity gravitational waves, then those prospects are very dim indeed. My question: are there similar indirect "experimental" methods for inferring the existence of gravitons?
102087
Please refrain from quoting general relativity. I'd like to know whether the exchange of virtual Higgs bosons, which are responsible for giving particles their masses, can produce an attractive force between particles.  You may mention other virtual particles such as the graviton if it is helpful. This is really confusing me because I kept wondering how the momentum is transferred by the virtual particle presuming a virtual Higgs boson or a virtual graviton (theoretically).
117508
Consider a man with mass 50kg.   When he jumps from a 2 meter height, the total force is $F=ma$ ie (mass * gravity), but nothing happens to him. When he jumps from a 50 meter height, the total force is (mass * gravity ) same, but he dies.   Why is this happening?
83340
This question is actually related to my earlier question ("").  The fact that objects move a lot in the universe and that the universe is expanding, can imply that gravity is a repulsive force that increases with distance.. so the farthest objects repel us more.  This can still explain several existing observations, e.g., why does the apple fall?   Motion is the result of such repulsion. Two objects unlucky enough not to be moving relative to each other get squished due to the repulsion of the rest of the universe  around them. The earth repels the apple less than the stars so it is pushed towards the earth.   Furthermore, it can explain the expanding universe without the need for dark energy.  This could be demonstrated in a thought experiment. If we take a lot of same-charge particles (with small mass) such as electrons and lock them in a large box at a low enough temperature. The mutual repulsion of the particles may cause similar motion as if due to gravitational attraction.   Another experiment would be to measure the slight changes in our weight during day and night when the sun and earth align (if their masses are large enough to detect the feeble change in repulsion).   [EDIT: the question in the original form may not have been clear. It is "can we model".. with a yes/no answer and why (not). If downvoting, please justify.
13916
The GPS is a very handy example in explaining to a broad audience why it is useful for humanity to know the laws of general relativity.  It nicely bridges the abstract theory with daily life technologies!  I'd like to know an analogous example of a technology which could not have been developed by engineers who didn't understand the rules of quantum mechanics.  (I guess that I should say quantum mechanics, because asking for a particle physics application could be too early.)  To bound the question:   No future applications (e.g. teleportation). No uncommon ones (for, who has a quantum computer at home?). A less frequently-cited example than the laser, please. If possible, for sake of simplicity, we'll allow that the quantum theory appears in form of a small correction to the classical one (just like one doesn't need the full apparatus of general relativity to deduce the gravitational red-shift).
118043
Let's say that we want to measure the gravity force in 1D, 2D, 3D  and higher spatial dimensions.   Will we get the same force strength in the first 3 dimensions and then it will go up? How about if we do this with Electromagnetic force?   I've include the Electromagnetic force just to see if I can find an analogy to the gravity force behavior.
37926
I was just reading a . It was a trivial question, obviously there is no force felt. But then it got me thinking.  Suppose you had a hollow sphere that was massive enough that outside of it, it became a black hole. It's not hard to imagine a situation where the magnitude of the force of gravity at the surface (while strong) is equal to the magnitude of the force on the particles of the sphere due to some phenomenon involving one of the other 3 forces (just so I can allow this hollow sphere to continue being hollow).  Obviously, I don't have to do the integral to know that any object inside the hollow would experience no net gravitational force due to the shell. However, being a few months short of General Relativity, I am curious to know whether there would be any effects from Gravity observed.  Would an observer inside experience any time dilation? There may not be any net force due to gravity, but one cannot deny that there are still some fairly powerful gravitational fields present that happen to superimpose to zero. Furthermore, (assuming a relatively massless observer) would they have access to any of the information that was "lost" in the black hole? If so, then if they were long-lived enough for the black hole to be able to evaporate around them, does this mean that not only would the black hole radiate that information, but it would also store a copy of it in the hollow?  I want to apologize in advance. I know this question seems a bit more like a discussion than a Q&amp;A thing.  To be clear, I am asking: In my scenario, would there be any effects of gravity on things in the hollow? And would information lost in the black hole be accessible to the hollow (which is essentially its own isolated bubble of the universe)? A good answer can address these two questions. If you want to add in your own opinions/contribute to a discussion about it, that'd be a bonus.
43959
Recently, I have heard of extensions of the double slit experiment that propose to use a bacterium as the particle. I've also heard that the double slit experiment, in principle, would still show an interference pattern if it were done with a human or a car, as long as there is no observer.  This made me wonder: if this is true, and I exist in a superposition, do I have a mass which exists in several locations at the same time and with an associated weight of 200lbs in each of my superposition locations?  If that were true and a fact, wouldn't that account for the missing mass which we attribute to dark matter? Also, even if on some other level this is true about particles only, wouldn't this be where we would find a link between quantum mechanics and gravity, linking it with relativity?  Forgive me if this is a silly question as I am almost 63 years old and have been almost 50 years out of school, but I just love to read and think about science and learn as much as I can.
51986
Inspired from the commentary on  question.  How far apart do two objects have to be for the gravitational force between them to be negligible? By negligible  I mean, that it could never be measured rather than a technical limitation that results in a measurement/force of zero and/or the accuracy of the measurement is too imprecise to be of use.  Basically when is the force to small to ever be measured, now or in the future? Is there a limiting distance?
48547
Do massless particles have a meaning in Newtonian mechanics? Do they have a physical interpretation? Because we don't have an equation of motion for massless particles, we don't have a gravitational potential. We could have electric potential but then we lack the equation of motion. I don't see how they can be a physical object, but I would love to hear from you about this.
103640
For instance, for a two-body system, there will always be a point in-between the two in which the forces of gravity completely cancel, and if I were there then I would experience no net force. I believe there is also a point, or a region, for three body systems as well. Assuming we treat the stars or planets as simply point-masses, will there always be, for any number of objects, a point, or a region, of equilibrium? Or no?
122606
Ok,this is a silly question. But for quite long I have been thinking about this. What is gravitation all about?? My book directly writes since force of gravitation is directly proportional to the masses and inversly proportional to the square of the distance ie. $$F = G\frac{M_1 . M_2}{r^2}$$ . So is this gravitation all about? What is the cause of it? The book then says     We are not in the scope in classical approach so as to discuss the cause of this. However,as a matter of fact that if there are more than one mass,then there is gravitation as it is their fundamental property.( Cause of gravitation can be attributed to exchange of non-classical particles between the masses) .    Then it ended the talkings. What are those non-classical particles? Why and how are they exchanged? So far I have studied physics , I never found such weird phenomenon like this. I want to know what is the cause of gravitation and what is the cause of exchange of those so-called non-classical particles? And how do they do it?
78986
I would like to know if light is affected by gravity, also, I would like to know what is the correct definition of gravity:  "A force that attracts bodies with mass" or "a force that attracts bodies with energy, such as light"?  Is light massless after all?
48333
Has there been any experiments, or are there any references, demonstrating gravity between atoms? If so, what are the key experiments/papers? Or if not, what is the smallest thing that has actually experimentally been shown to be affected by gravity?  I don't know of specific papers demonstrating gravity between larger objects, but I can vaguely remember learning about them in my classical physics class as an undergraduate. However, I have never heard of experiments demonstrating gravity at atomic or subatomic levels.  I don't have a physics background so it's not obvious to me, so just looking to see the actual research/evidence behind it, so I can start to try to imagine how gravity works at a quantum level.
59889
I am something of a dilettante in physics, so please forgive me if the answer to this question is painfully obvious. The question is simple, can something that theoretically has no mass exert a force. I have been tossing around this and other similar questions in my head for a while now and have not really found any concrete answers to my inquiry. I am thinking about how light seems to be able to push objects but yet has no mass, however I expanded the question to be more encompassing in hopes of further learning.
505
In many physics divulgation books I've read, this seems to be a commonly accepted point of view (I'm making this quote up, as I don't remember the exact words, but this should give you an idea):      is not a result of our lack of proper measurement tools. The fact that we can't precisely know both the position and momentum of an elementary particle is, indeed, a property of the particle itself. It is an intrinsic property of the Universe we live in.   Then this video came out:  (skip to , if you're already familiar with the uncertainty principle).  So, correct me if I'm wrong, what we may claim according to the video is:     the only way to measure an elementary particle is to make it interact with another elementary particle: it is therefore incorrect to say that an elementary particle doesn't have a well defined momentum/position before we make our measurement. We cannot access this data (momentum/position) without changing it, therefore it is correct to say that our ignorance about this data is not an intrinsic property of the Universe (but, rather, an important limit of how we can measure it).   Please tell me how can both of the highlighted paragraphs be true or how they should be corrected.
8539
Wikipedia lists the  as a hypothetical particle. I wonder whether graviton is indeed hypothetical or does its existence directly follow from modern physics? Does observation of gravitational waves amount to the discovery of graviton or could there be gravitational waves not composed of gravitons?