Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: syhprum on 01/02/2018 14:10:12

Title: Is it possible to build a gravity shield?
Post by: syhprum on 01/02/2018 14:10:12
To shield from gravity would in my opinion require something as massive as a Neutron star which would of course generate its own gravity which would make experimentation difficult to say the least.
If the gravitational field is mediated by Gravitons it is postulated that they are much less massive than Neutrinos which are rather lite and take a lot of stopping.
let me hear your views.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 01/02/2018 14:30:24
A few years ago, I recall reading about a team of researchers who claimed they had achieved a small fraction of 1% weight reduction in a small mass, as a result of gravity shielding,  I can't find the link/reference at present; but, as far as I'm aware, this result has not been replicated. 

I have a feeling that gravity shielding would run into conflict with the equivalence principle. 
Title: Re: Is it possible to build a gravity shield?
Post by: Janus on 01/02/2018 16:47:31
To shield from gravity would in my opinion require something as massive as a Neutron star which would of course generate its own gravity which would make experimentation difficult to say the least.
If the gravitational field is mediated by Gravitons it is postulated that they are much less massive than Neutrinos which are rather lite and take a lot of stopping.
let me hear your views.
Add to this that gravity would be mediated by virtual gravitons.  Consider this: nothing, including gravitons, can escape the event horizon of a black hole,  yet virtual gravitons ( assuming gravity can be brought into the QM fold), have no trouble mediating the gravity of the Black hole.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 01/02/2018 17:15:02
 
Quote from: Janus
Consider this: nothing, including gravitons, can escape the event horizon of a black hole,  yet virtual gravitons ( assuming gravity can be brought into the QM fold), have no trouble mediating the gravity of the Black hole.

If mass distorts spacetime, and that distortion is gravity, surely, nothing has to escape from the BH in order for its gravity to be felt.
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 01/02/2018 17:18:15
This implies that the field should be considered as independent of the force carrier.
Title: Re: Is it possible to build a gravity shield?
Post by: Bored chemist on 01/02/2018 20:48:37
If the gravitational field is mediated by Gravitons it is postulated that they are much less massive than Neutrinos which are rather lite and take a lot of stopping.
The electromagnetic field is mediated by photons which are massless. But they are  relatively easy to stop.

I think the big problem with a gravity shield is that if I put one under one side of a wheel it becomes unbalanced + starts to turn.
I can connect the wheel to a generator and get free energy from it...


Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 01/02/2018 20:58:11
If the gravitational field is mediated by Gravitons it is postulated that they are much less massive than Neutrinos which are rather lite and take a lot of stopping.
The electromagnetic field is mediated by photons which are massless. But they are  relatively easy to stop.

I think the big problem with a gravity shield is that if I put one under one side of a wheel it becomes unbalanced + starts to turn.
I can connect the wheel to a generator and get free energy from it...

That sounds like a good kitchen science experiment. When do we start .... ?
Title: Re: Is it possible to build a gravity shield?
Post by: Bored chemist on 01/02/2018 21:06:13
When do we start .... ?
When someone invents a gravity shield.
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 01/02/2018 21:24:33
Oh you are so negative! You remind me of gravitational potential.
Title: Re: Is it possible to build a gravity shield?
Post by: syhprum on 02/02/2018 01:46:45
I don't think getting free energy is a problem it sounds rather useful (it could run my bitcoin computer).
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 02/02/2018 07:24:26
I don't think you realise the gravity of the situation.
Title: Re: Is it possible to build a gravity shield?
Post by: syhprum on 02/02/2018 09:58:05
Although there are practical difficulties in doing the experiment that JeffreyH suggests it is quite easy to perform if Photons are substituted for Gravitons.
When half of the paddle wheel is iluminated it will rotate due to the momentuam of the incoming Photons and it is easy to see that the energy comes from the source of the Photons.
If we perform the same experiment with Gravitons there is a problem where does the energy come from, a body producing gravity cannot be considered to be radiating energy so does this prove that a gravity shield is not possible in theory as well as the practical difficulties in making one. 

Title: Re: Is it possible to build a gravity shield?
Post by: evan_au on 02/02/2018 10:22:21
Just go into orbit - then you are in microgravity.

That's nearly as good, isn't it?
Title: Re: Is it possible to build a gravity shield?
Post by: syhprum on 02/02/2018 15:49:12
The problem is that the shield must be of a low mass otherwise it will generate it's own gravity whereas if you take the example of what is required to stop Neutrinos it would seem that something very massive is required.
Title: Re: Is it possible to build a gravity shield?
Post by: Janus on 02/02/2018 17:54:12
If the gravitational field is mediated by Gravitons it is postulated that they are much less massive than Neutrinos which are rather lite and take a lot of stopping.
The electromagnetic field is mediated by photons which are massless. But they are  relatively easy to stop.

I think the big problem with a gravity shield is that if I put one under one side of a wheel it becomes unbalanced + starts to turn.
I can connect the wheel to a generator and get free energy from it...



Again, the electromagnetic field is mediated by virtual photons.  Photons are quanta of electromagnetic radiation( light waves for example).  Gravitons would be the quanta of Gravitational radiation( the Gravitational waves detected by LIGO). 
Photons cannot escape the event horizon, yet a black hole can have a charge and thus an electromagnetic field which is mediated by virtual photons.    Likewise, gravitational waves/ gravitons cannot escape the event horizon,  but the BH still has a gravitational field that would be mediated by virtual gravitons. 
 
As far the energy consumption goes,  I see three possibilities:
1. The most likely is that a gravity shield is not possible.
2. It must be actively maintained, which means that you would have to supply the energy needed to "cancel out" the gravity acting on any mass within its effective region.  That energy input would be the equivalent of accelerating the mass up to escape velocity (~ 63,000,000 joules per kilogram of mass at sea level).
3. If it is not what is creating the shield that provides the energy,  it would have to be supplied during the passing from the non-effected area to the effected area.  In other words, if you tried to take a 1 kg mass and move it from a non-shielded zone into the shielded zone, it would require  63,000,000 joules on your part to do so.
Title: Re: Is it possible to build a gravity shield?
Post by: petelamana on 02/02/2018 20:32:30
Let's shift gears a bit.  Consider gravitational waves.  Would it be theoretically possible to emit a cancelling gravitation wave, thereby cancelling gravity out in the region where they collide?
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 02/02/2018 20:39:22
Quote from: Jeffrey
This implies that the field should be considered as independent of the force carrier.

Thinking about this raises some questions in my mind.

Popular explanations of gravity, according to GR, tend to follow this pattern:

1) Visualise empty space (spacetime?).
2) Introduce a mass.
3) The mass causes spacetime to warp.
4) The warping of spacetime = gravity.
The question this seems to leave open is: What is the source of the energy that warps spacetime?

Perhaps there is another way to look at it.

1-2) As above.
3) The mass gives rise to gravitational force (GF).
4) This GF is best described (mathematically) in terms of spacetime curvature.
The wording of the question in the first scenario may change, but the question remains unanswered.
Three other questions must be added.
1) Is spacetime actually curved?
2) What would curved spacetime look like?
3) Is what we describe as curvature simply the imposition of directionality on spacetime?
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 02/02/2018 21:18:42
There are two things here. The speed of the force carrier and the speed of the field. When the source of the field moves its velocity is always less than c. Therefore the speed of the field through spacetime must be also less than c. However a force carrier always travels at c in a vacuum. The field is still the source of the curvature and therefore when accelerating with the source mass it causes gravitational radiation. This is a subtle point.
Title: Re: Is it possible to build a gravity shield?
Post by: Janus on 02/02/2018 21:49:49
Let's shift gears a bit.  Consider gravitational waves.  Would it be theoretically possible to emit a cancelling gravitation wave, thereby cancelling gravity out in the region where they collide?
No, because gravitational waves are not responsible for gravity.  They carry information about changes in the gravitational field.   Thus if you were to induce a change in the gravitational field at some point, then the information of this change would propagate at c to other points of the field as a gravitational wave.  To create a second cancelling wave, you would have to induce another change in the field. For this to cancel out the first wave entirely, it would have to cancel out the initial change in the field.    You might be able to arrange to gravitational waves to intersect at a point in such a way that they cancel out at that point.  But that just means that that point doesn't measure or detect the distant changes in the field that created the waves.  Thus its local field strength simply remains the same and it is not subject to any change in gravity. 
Title: Re: Is it possible to build a gravity shield?
Post by: opportunity on 03/02/2018 12:56:28
To shield from gravity would in my opinion require something as massive as a Neutron star which would of course generate its own gravity which would make experimentation difficult to say the least.
If the gravitational field is mediated by Gravitons it is postulated that they are much less massive than Neutrinos which are rather lite and take a lot of stopping.
let me hear your views.


If gravity is a wave of some type of description we're beginning to hear about more often (not sure which link to add here), something of course we haven't fully understood in contemporary science, wave-properties on that new front of ideas could ensue, much like with electromagnteic waves and how standing waves there can localise effects. I say "could". A far more detailed analysis of any functionality of what we oberve as gravitational waves would need closer examination. The best approach I'm thinking is to first properly understand how gravitaional effects could emerge from the atom as a wave-property function. In an environment such as the atom for instantance, on that level, I'm thinking "time" and it's association to quanta is a more useful tool-basis than "space". Let's face it, an atom defines a "succesful" event of space that is "self-contained" for lack of a better term. It's an atom; the features within that entirety of space revolve around the "timing" of every part of that space that makes it an atom.....so why don't we examine the timing of those spatio-temporal angles of reference in that spatial construct called an atom? "In" the atom, why not make "time" "the" priority? Is it implausible to suggest that a new way of understanding time on that level could better describe gravity, let alone the strong nuclear force?

You're initial question though is interesting. Like, "imagine trying to resist the gravity of this planet.....one would need something beyond the size of this planet conviently packaged into the size of something held in front of us". And even then it would need to be something that ignores the effect of the gravity of the planet else collapse into it. That's either nuts or the wrong way of thinking how gravity works. Why understand a concept that can't be useful according to certain ways of approaching the idea?

Do you think "gravitons" fix this?

Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 03/02/2018 20:47:41
A gravity shield is not to shield against gravitons. You would need to cancel the effects of the gravitational field. Since the field is generated by matter it would require cancelling whatever it is about matter that generates the field in the first place. This would be like trying to cancel the charge of a particle by cancelling its electromagnetic field. The fascination with gravity shielding is linked to the idea of anti-gravity as some magical way of enabling space travel. If you are in deep space with little strength in the gravitational field the technology would become useless. That is if the magic elves allow us to discover it.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 03/02/2018 21:19:39
Quote from: Jeffrey
There are two things here. The speed of the force carrier and the speed of the field.

Jeffrey, sometimes your answers remind me of the joke about a mother visiting her newly married daughter.  Tasting something the daughter had cooked she said:  It’s very nice, but I don’t like it. 

At times I’m tempted to say: That’s a very good answer, but I don’t see what it answers.
Possibly I need to take things in smaller “bites”.  Let's start with the field.

You refer to “The speed of the force carrier [no problem there] and the speed of the field”.
My understanding is that a field is something that permeates all of space, so what is the significance of its “speed”, and in relation to what? 
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 03/02/2018 21:30:28
The field is centred on a object. This object is the source of the field. If the source object is moving through space, then since it is the source of the field, the field must also be moving. This has to happen to preserve the inverse square nature of the electromagnetic and gravitational fields. Otherwise the radial nature of the field is destroyed. The speed of the field is independent to the speed of say the photon or graviton. It is also independent of the speed of propagation of the field itself. This has to be so since this is the mechanism of red and blue shift.
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 03/02/2018 21:32:30
In order to shield against something you must first understand its nature.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 04/02/2018 18:15:32
Quote from: Jeffrey
The field is centred on a object. This object is the source of the field. 

E.g. an Earth-size object moving freely through space.  The gravitational force it generates permeates space. 
The strength of the force obeys the inverse square rule.

Quote
If the source object is moving through space, then since it is the source of the field, the field must also be moving.

Locally, the strength of the field varies as the object moves.  To an extent that varies with distance from the object, the strength varies throughout the field, but can this be equated with any overall movement of the field? 

When the object was at position A, the field occupied all of space, as it does when the object is at position B.
Title: Re: Is it possible to build a gravity shield?
Post by: Bored chemist on 04/02/2018 19:15:07
Which part of "it's a "free energy machine and therefore impossible" are people struggling with?
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 04/02/2018 19:35:09
Quote
Which part of "it's a "free energy machine and therefore impossible" are people struggling with?

The part that says: "I wish this could be".  This leads to looking everywhere for it and never, quite, giving up.

Its a bit like the "Universe from nothing idea".   
Title: Re: Is it possible to build a gravity shield?
Post by: Colin2B on 05/02/2018 09:15:10
Locally, the strength of the field varies as the object moves.  To an extent that varies with distance from the object, the strength varies throughout the field, but can this be equated with any overall movement of the field? 
It depends what you mean by moving. Sound waves propagate in air by variation of air pressure, but the air doesn’t move forwards with the wave.
We can talk about the value of the field varying at points in spacetime, but that doesn’t imply the field itself is moving. However, we talk about eg water waves, moving so we also talk about lines of force, pressure etc moving, just important to remember what is really happening.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 05/02/2018 12:17:58
Quote from: Colin
It depends what you mean by moving. Sound waves propagate in air by variation of air pressure, but the air doesn’t move forwards with the wave. We can talk about the value of the field varying at points in spacetime, but that doesn’t imply the field itself is moving.
.
That’s what I was thinking.  I was trying to square that with Jeffrey’s mention of the speed of the field.

Quote
However, we talk about eg water waves, moving so we also talk about lines of force, pressure etc moving, just important to remember what is really happening.

Obviously, there is vertical movement of the water, but no forward movement.  The fact that water waves may break does complicate things a bit, but in general the water doesn’t move.  We can talk about the speed of the waves, but not the speed of the water.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 06/02/2018 17:29:56
Returning to the questions in #16;

What is the source of the energy that warps spacetime?
Does the source object lose energy in causing spacetime to curve?
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 06/02/2018 18:50:13
Returning to the questions in #16;

What is the source of the energy that warps spacetime?
Does the source object lose energy in causing spacetime to curve?

No because if the source object is in an inertial frame or reference it can only be losing rest energy. This would eventually lead to all the rest energy vanishing. This would remove all the rest mass. We know this does not happen so the energy of the field must be independent of the energy of the source.

NOTE: If the object is in an accelerating frame it will lose kinetic energy by emitting gravitational radiation.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 06/02/2018 20:38:11
Quote
No because if the source object is in an inertial frame or reference it can only be losing rest energy. This would eventually lead to all the rest energy vanishing. This would remove all the rest mass. We know this does not happen so the energy of the field must be independent of the energy of the source.

This is, more or less, the position from which I started, a few years ago.  Then, I was asking myself, and others, how, for example, the Earth could hold the moon in orbit for millions of years without, apparently, losing mass.  Eventually, I got that sorted. 

I’m still left with the question: If, as you suggest, the energy of the field must be independent of the energy of the source, where does that energy of the field come from?
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 06/02/2018 20:54:06
You could ask where does the energy of the source come from? It is there in the form of mass, some of which derives from the Higgs field and the rest from binding energy. This is neglecting electrons. The point is it persists with no apparent source apart from itself. Why should the field be any different? The field has a potential value which only becomes energy when it interacts with particles. It also persists and has no apparent source other than itself. That is just the way it is.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 07/02/2018 14:03:25
Quote from: Jeffrey
You could ask where does the energy of the source come from?

Been there – done that. Possibly traces back to the BB.  Tracing gravity back to the BB is, obviously, a related topic, but could be a distraction here.

 
Quote
  The field has a potential value which only becomes energy when it interacts with particles. It also persists and has no apparent source other than itself. That is just the way it is.

Are you saying that the gravitational field exists throughout space, but becomes observable only it interacts with mass?
Title: Re: Is it possible to build a gravity shield?
Post by: jeffreyH on 07/02/2018 17:51:38
It all depends upon what you mean by observable. If there are no particles in the field at all then nothing happens. The field just has potential. It is like if there is no charge moving through an electromagnetic field nothing happens. Note that I said particles rather than mss in respect to the gravitational field. Since energy Is a better term when considering massless particles interacting with the field.
Title: Re: Is it possible to build a gravity shield?
Post by: Bill S on 07/02/2018 20:40:56
Perhaps I should have said “potentially observable/detectable”? 

The essential thing I was trying to clarify was whether or not the field exists independently of the presence of matter/energy.  One often finds the assertion that the presence of mass (which I interpret as mass/energy) creates gravity.  The more I try to understand this, the more inclined I am to see the situation as one in which the gravitational field exists all the time, and becomes activated by the presence of mass/energy; rather than there being no gravitational field present until mass/energy enters the picture.
Title: Re: Is it possible to build a gravity shield?
Post by: kpvats on 22/04/2018 08:19:03
Well, it is difficult to answer yes/no, but different aspects can be considered -
I would prefer to call it inversion of gravity rather than shielding. There is no such thing as anti gravity as that would even in theory, require a negative mass.
1) Can there be a object/sheet kind of shield - No.
2) Can there be a mechanism - Probably yes. I do not mean fake impressions like em levitation, gyroscopic motion, centrifugal force and so on.
3) It appears to violate law of conservation of energy - There can be ways around it - energy remains conserved in a sling shot maneuver, and in a similar manner, it could be in case of a gravity modification mechanism too. It may take energy from kinetic energy of earth. We can also say we would not know where the energy came from rather than saying conservation is violated.
4) Would it violate equivalence principle - No, Because it is altering the gravitational field, and not the gravitational. mass.
5) Does General Relativity prohibit gravity shielding - Not really. GR mainly gives us is how the space curvature evolves. Natural outcome of set of tensors present in space/energy is one way (inward or say downward) curvature of space and that is what GR deals with. GR (per my knowledge) does not talk about two way curvature, or in other words, it does not talk about possibility or impossibility of inversion of that one way curvature.

I personally think inversion drive is possible.