You are speaking of gravitational shielding. The problem is that this would be a violation of the equivalence principle. Thus, it would not sit comfortably with general relativity and Newtonian gravity. The general consensus is that no such shielding is possible.

Maybe there is some loophole here in quantum gravity, but that is getting more speculative .

For laboratory experiments, make them "freely falling", like Skylab and Spacelab.

If you meant something more fundamental than that, continue dreaming :-)

i think that you don't unstand the question, please i need a seroius response about this phenomenon and not obstacles

Thanks for your response but it is not what i search exactely

Elhaouari Kobzili

>i think that you don't unstand the question, please i need a seroius response about this phenomenon and not obstacles

You need to ask clearer questions.

And the phenomena of reducing gravity has never been seen. We have good reasons to think why it cannot happen as pointed out in my earlier reply.

Can you be more specific about which aspect(s) of reduced gravity you are asking about? Providing the context (or A context) may provoke better answers ... OR maybe, describe what is known to you about your problem already (what you think you know...). Add what you think others know. And finally, think about what you don't know. ..

(Although my own experience (solving problems ) tells me that if I can make my questions more specific, define the boundaries more precisely... If I can be specific about the info I don't have even, I will be more than halfway to a solution... OR, at least, to a better problem (one I can solve ...))

Thank you.

At first i wish to know exactely the gravity force come from what to reduce it. The physical representation is it an electromanetic wave

Elhaouari> ... wish to know exactely the gravity force come

Near the surface of the earth, almost all of it comes from the 6 × 1024 kg mass of the Earth.

Elhaouari> what to reduce it

One could try to reduce the mass of the Earth − not a very realistic project. And with unwarranted side effects. One can move closer to the equator, but the effect is very small. Staying at the equator, one could try to make the Earth rotate faster − not a very realistic project. And with unwarranted side effects. One could try to move to the Moon, which have a smaller mass of 7 × 1022 kg. This will reduce the gravity force by a factor of about 1/6.

The most practical solutions mankind has come up with are those already mentioned by Ales and me. Outside bad science fiction movies.

Elhaouari> ...is it an electromanetic wave

Not at all, not even close. But the gravity forces we normally experience have some similarity to electrostatic forces. The gravity force is proportional to the mass of its source (the Earth), while the electrostatic force is proportional the electric charge of its source. Both forces falls off like the inverse square of the distance from its source. An extremely important difference is that unlike electric charges, which come with both signs, all known forms of matter come with positive mass. For this reason one cannot shield gravity forces, as you have already been told.

Elhaouari> i think that you don't unstand the question

I think your question was well understood; what I don't understand is how you could have acquired such grave misunderstandings of nature as you seem to have.

Thanks for your response

Thinking about "reducing" the effects of gravity allows one to probe the limits of what is known, but also, what one knows...

Kralj and others are quick to point out what is known and thought about "popularly" with regard to gravity reduction/shielding (offering a link to Wikipedia)...

Olaussen offers a quick description of the "classic model" and points out limits that, I agree, should be "obvious" to an undergraduate physics student ...

But no matter how simple or complex or difficult or impossible a problem , starting at the beginning of what is known...is usually worthwhile.

One might start with the set of equations characterizing the classical model of gravity. In the classical model, using the classic equations, the "practical" difficulty of shielding the effects of gravity do become obvious .

Unlike Bruce above, I would not say a consensus about gravity shielding outside of the classic models has been reached (or even exists). In fact, several competing "models" of gravity are offered to describe the effects of gravity in many non-classical circumstances. ..for exames, on the event horizon of a black hole or inside a black hole, etc.

Although we know that not one of these models is very well described.

More to the point, not well described for lack of observations (measurements). Consensus is not possible at the point where our knowledge is ...so thoroughly incomplete. (But this is how it works. We offer a model, we describe it, we use such a model for certain problems and until , it is no longer useful... at which time we would add to the model or perhaps, throw out the model and start again... )

I have heard speculations about "gravity bleeding" with regard to (wrt) how a parallel universe might be detected...And such lines of speculation would not, I think, be limited to only detecting (or not) a parallel universe , but also, extended to the detection of dimensions beyond the three...

I think about these kinds of questions (and even encourage wilder speculations...) For examples, I think about how gravity could be conceived if the objects under consideration are smaller than the gravitational exchange particle. And in this case, I ask what gravity would "look like", how would it behave...

OR , in the case only one object existed in the universe, what would happen to it's gravitational-exchange particles ? And along those lines ( of speculation), if we consider a universe that is habited by objects, but none of which exchange gravitational particles, how would that universe behave? (And wrt this universe, we might then ask, what becomes of "space time " itself ? And how might we characterize this ?)

OR, if objects , large or quantum-sized, are located inside of a black hole, how would the gravitational forces betwn those objects be described, both from the perspective of being an observer inside the black hole, but also from the perspective of a third object that is located just outside of the black hole? Naturally this would lead to the question of whether then, a black hole might perform the functions of a "gravitational shield" ?

Or , consider the case that two objects (either very large or very very small ), that awould be both located near a black hole (that is also very large or very very small in "size" ), in an attempted exchange of gravitons, fail in the exchange so that one of the objects' gravitational exchange particles "fall" and /or "disappear" into the black hole...In this case, how would the gravitational equations be written?

I take my "license " (so to speak) (to speculate about such things) from Einstein. Which is appropriate.

After all, he would have to come up in any conversation like this , because any serious discussion would necessarily begin with what is already known.

And such speculations (as I have offered above) would necessarily force my attention to the "basics" of relativity. The current models of relativistic cosmology are referenced in many texts. Stiff math indeed, but what fun is a universe without ...such math?

Yes. If only... Thank you .

Crystal> ... our knowledge is ...so thoroughly incomplete.

Certainly! If we consider the functioning of modern human societies, they would be brought to a very brutal standstill and chaos, if removed for all technology and knowledge based on the fundamental scientific discoveries after (say) 1900. That is mostly quantum physics, but also to some degree special relativity, and to a small degree general relativity (through our dependency on the GPS and similar systems). But none of these developments have rendered Newtonian mechanics and gravity obsolete; and no further development will change that (at least this is what we must hope and pray for).

Crystal> ... speculations about "gravity bleeding" with regard to (wrt) how a parallel universe might be detected...

'Speculations' is indeed the proper word here. Although the possibility of many (say 10500) other universes, with properties very different from ours, has been entertained in f.i. string theories and cosmological inflation models. But, if we should every collide with one such hypothetical parallel universe, which suddenly emerges from some extra-dimensional direction, this would certainly destroy all conditions for life as we know it. This would be the ultimate cosmic catastrophe. In such a scenario, one simply cannot speculate that there will be anyone left to enjoy the detection of some innocent 'gravity bleeding'; that belongs to the categories of dreams and science fiction.

Crystal> [Einstein] would have to come up in any conversation like this , because any serious discussion would necessarily begin with what is already known.

I am not aware of any possibilities of repulsive gravity, or of shielding gravity, within General Relativity. No matter how exotic forms of matter are hypothesised, and no matter which gravitational environment one lives in. It would not even help moving inside the horizon of a black hole.

There apparently are some super-gravity theories which exhibit "anti-gravity" phenomena. But that seems like a misleading description, since it refers to repulsive forces carried by different fields than the gravity field (only related to it by supersymmetry). Anyway, such forces would only manifest themselves on the subnuclear level, with no effect on everyday life.

Theoretically, there exists one interesting (mathematically quite natural and appealing) possibility that the value of the Newton gravity constant depends on the magnitude of some (Brans-Dicke type of) scalar fields. So, by changing the values of such fields one might be able to change the strength of the gravitational force. But that certainly would be extremely difficult, compared to simply moving to the Moon, or building huge gravity free space stations. And certainly extremely dangerous, since that would simultaneously change a lot of other physical parameters, whose current values make life possible.

Cf. here: https://www.youtube.com/watch?v=IFBtlZfwEwM

I (obviously) do not let the physical laws get in the way of my good fun... (to speculate).

While this subject is (also obviously) not my area ...and not either an area in which I am earning a grade or in which I am being paid to solve problems... if I allowed the physical laws of the universe to keep me from thinking about or venturing into a new subject area (for whatever the reason (or the best reason, cause it pleases me...)), I would say nothing.

And I would learn nothing.

The best compliment I ever received from anyone, (and from a scientist (so I value it the more ...)), had nothing to do with my looks, my great sense of irony, my technical-writing or editing skills, nor even my math skills... He said

"You are not afraid to look stupid!"

And in truth, I am not. (In fact, if I didn't feel stupid at least twice a day, I wouldn't know I was alive...)

But the follow-up to this compliment makes the first statement the asset it is.

I am teachable.

wrt my role as a technical writer/editor for example, because writing and editing are two very different tasks (for me) , each very different activities, each requiring very different skill sets... (And I find this true whether it is a fiction or nonfiction I am creating). While in the case of recounting research , describing a method , or discussing a conclusion, I strive to be correct (meaning specifically, to remain w/ in the bounds of what is physically true...), because I see writing as a creative process, donning the editorial hat (to be my own critic) too soon, renders most of my writing, not just unreadable but, not as well developed as it could be. Incomplete.

But to the point, I realized a long time ago (before kids were sorted into groups of being "math/science people" or not by Jr high-school age) that , even the subjects in which I am considered knowledgeable (to be paid to answer ...), and I consider myself expert... I can't even say how often my "expertise" is ...not complete.

In fact, I suspect never to achieve a perfect understanding of anything.

(Which means I will always have something new to learn...)

Thus do I always assume I will not be right. But strive to be.

In answering a question like this, (in a process very similar to that I do when I write), while I do try to confine myself to "a truth straightjacket", I may hit ADD before I check that my answer did not ...shall we say, overshoot either the bounds of reality or just the bounds of the problem posed.

It is a matter of ...matching what I failed to understand in order to reach the false conclusion I did. Which would require me to start fresh.

I probably would have refrained from offering any answer to such a question, if I were in a more formal setting ...

(Or someone was paying me to be less speculative!)

I referenced Einstein for two reasons. One, because I know so little about (probably even Newtonian) gravity, starting at the beginning and working my way forward would include Einstein .

Einstein is not the only person to think difftly than Newton about gravity. But Einstein also came to mind, because... (putting aside the cute, but largely (I would guess) apocryphal stories about him...), we do know he allowed himself to ...speculate.

I don't know what the early drafts of his "miracle " papers looked like before they were published ( in 1905), but I would assume at some point, he threw his ideas out there ... and figured out very quickly which areas required more work.

There is a lot to know.

I don't know about the person who posed this question's level of satisfaction. But I certainly seem to have benefited!

Thank you.

What a question ! I we need really to reconsider the way we think, I think NASA has some answers about this topic

Allam,

you are now going down the route of conspiracy theorist!

If the opening question is about shielding, then this seems very unlikely due to the equivalence principle. If the opening question is about something else, then the answer would depend on the context.

> Accusing and ridiculing someone as being a "conspiracy theorist" is the most reliable way to keep up the conspiracy.

And suggesting NASA is not telling us is perfectly okay and normal.

Thanks for the clarification.

Dear Elhaouari

Practically by any opposite force.

Theoretically by anti-gravity. You need enough antimatter. More “New Concept of Mass”.

The ordinary antimatter is not applicable. It annihilates with matter. You need antimatter to be produced of magnetic monopoles. More “New Concept of Magnetic Monopoles”. The magnetic matter do not affect ordinary matter.

Best regards

Ilgaitis