The latest discovery of the BICEP2 shed new light on negative gravity. Nevertheless it's still a theoretical assumption and there are no experiments that prove it. What is the probability that two types of such gravity (attraction and repulsion) exist?
No, BICEP2 doesn't have anything to do with negative gravity. It has to do with inflation, a totally different effect. Gravity, as described by the metric tensor, is always attractive. The reason is that this describes spin 2 excitations and even spins mediate attractive interactions only.
No, BICEP2 doesn't have anything to do with negative gravity. It has to do with inflation, a totally different effect. Gravity, as described by the metric tensor, is always attractive. The reason is that this describes spin 2 excitations and even spins mediate attractive interactions only.
Dear Stam
The new observations from BICEP2 ruled out some of inflation theories while support other at least according to some researchers. One of the theories that arises again is the Big Bang Inflationary theory. As explained by Alan Guth that this theory needs
negative gravity particles to justify Inflation process as a triggering particles for inflation. But this is the weak point no such particles have proven to be found yet.
No, inflation does not need ``negative gravity particles''. A perfectly normal scalar field is all that is required. Cf. the review: http://arxiv.org/pdf/astro-ph/9508078v3.pdf
Dear Stam
in the mensioned paper there is a phrase
" Itispossible,therefore,thattheproblem couldberesolvedifthecosmicexpansionwasnon–adiabaticforsomefinitetimeinterval t∈[ti,tf]duringtheearlyhistoryoftheuniverse"
As I understand if it non adiabatic then there must be outside force affecting on it because it is impossible to lose or gain from outside the universe space which is supposed to be vacuum, what do you think?
That's the motivation for inflation, that implies the introduction of a new ingredient. One way to describe this new ingredient is by a scalar field. It turns out that this can be a physical scalar field. By the way, as Friedmann and de Sitter showed, in the 1920s, Einstein's equations can describe an expanding universe. What inflation does is describe a universe, where expansion was very rapid, much more than could be accounted by Einstein's equations alone, even with a cosmological constant-that we, now, know is non-zero and positive.
The mysetry with Inflation is the Big Bang force is not enough to accomplish it so it needs such assumtions of non adiabatic process which may refer to outside force
that helps in accomplishing it.
Actually there several more reasons that indicate that a period of very rapid expansion took place-read the review, it's very well written.The issue is how to describe this process quantitatively. It turns out that a scalar field is sufficient. The question then arises, how to determine its potential (cf. the review)-and how does this scalar fit into the description of the other fields we know. This we do not understand yet-perhaps the new runs of the LHC will provide hints.
I suggest the paper " Polarization and anisotropy induced in the microwave background by cosmological gravitational waves" by A. G. Polnarev in Soviet Astrophysics Vol. 29 pag. 607 to understand the rule of General Relativity and QM.
Instead of calling it negative gravity, see how a light ray can block gravitational effect or if the object is over the light ray, its weight increase. The experiment is well described in GRAVITYFORCES.COM.
It's not *possible* to ``block'' (or ``screen'') the gravitational field, for the simple reason that gravity couples to all forms of energy through the energy-momentum tensor--that's what the equivalence principle means. The only (to date, hypothetical) way to do this would occur if *other* fields, besides the metric tensor, were necessary, to specify spacetime, i.e. if the Einstein-Hilbert action would depend, not only on the metric, but, also, on other fields. The scalar-tensor theories of Brans-Dicke type, however, don't introduce repulsion, since the scalar has spin-0 and, thus, mediates attractive interactions.
To mediate repulsive interactions, these fields need to be spin-1 fields. Such fields can occur in supergravity theories. But these spin-1 fields are *not* electromagnetic.
They were first studied by Joël Scherk in the paper
``Antigravity: A Crazy Idea?'' http://inspirehep.net/record/142417
hI
I am sorry to disaqree with you. Maybe in the past no one could block gravity. Since 2009, it was done with a torsion pendulum and a 1.5 watt red laser laminar beam. The paper was published in PHYSICS ESSAYS IN Dec 2011.
Also a gravity control panel 4 feet by 4 feet was built and using 945 watts of light giving 63000 lumen, it was discovered that over 0.1% of the weight of a 200 g mass was reduced when placed under the panel or increased when placed over the panel.
If you want a demonstration, it could be arranged easily.
Things are changing and facts prevade over theories.
Louis
These effects don't have *anything* to do with ``blocking'' gravity. Of course it's possible to apply a force on an object, in order to cancel the force due to ``gravity'', in this case the attraction of the Earth. But this doesn't ``block'' gravity in the sense that it doesn't affect the equality of the inertial mass of the object, as the measure of its response to an external force and the gravitational mass, the measure of its interaction with other forms of matter. And it doesn't result into a repulsive force between two masses. In the static limit of course it's possible to cancel gravitational attraction by other forces and Scherk's article reviews this situation.
Hi
In this case, there were no other forces to cancel the force caused by gravity.
Each person can have its own belief and I respect that. But light did block gravitaional attraction, no matter what you say. Before saying its not possible it would be wise to look closely at the results and then make up your mind. Facts are more important than theories, said Einstein.
Cher Stam
Viens en vacance au Canada cet été; il me fera plaisir de te recevoir et tu pourras commencer l'expérience toi-même.
Bienvenue , Louis
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