What is the nature of gravity?

Is it a result of space/time curvature as general relativity suggests?

Or is it a quantum field? If it is a field, what is the nature of the carrier (graviton)? Vibrating strings, spin networks, etc.?

Perhaps something else entirely?

"I don't know" option is required. That would be the honest answer of everyone, I think.

Or perhaps you should ask which of those listed is the best known model of gravity?
Or maybe which are good models of gravity? In that case, you'd have to include Newton's universal law of gravitation, and make it a multi-select poll.

Personaly i do not have a gut feeling for Quatum loop or String or even warped space time, I am waiting to see if gravitational radiation is/not
detected, if it is i will have to change my view.

There are two types of precession, caused by the space-time warping, predicted by GR, and have been tested by the Gravity Probe B experiment. While there is still some work on the frame dragging results, the geodetic precession is obvious and is considered to be confirmed to within 1%. There have been other test of these that confirmed them to lesser degrees of accuracy.

Wilgory

There are two types of precession, caused by the space-time warping, predicted by GR, and have been tested by the Gravity Probe B experiment. While there is still some work on the frame dragging results, the geodetic precession is obvious and is considered to be confirmed to within 1%. There have been other test of these that confirmed them to lesser degrees of accuracy.

Wilgory


Do you think that detection of gravity waves will be the clincher?

GPb has had problems to say the least, if the experiment were to be repeated with the same results that would be good enough for me.

fishtail,

When it comes to physics and cosmology I am a follower and don't feel qualified to speculate. If I had to guess, I would say the next step will be a minor extension of General Relativity or a completely new and revolutionary find like that made by Einstein. There is rapid progress happening in cosmology and the potential of a major breakthrough with Cern coming on line. These are exciting times, scientifically speaking, and I can hardly wait for the GPB results to be finalized. With all the theories out there I would not try to say which is more correct, even if i was qualified to try. I will have to be content with what comes out of the research and observations. In the coming years there are many experiments that I hope will help us solve some of the mysteries of the universe. I've been waiting most of my life(40+ years) for a theory of everything and lately have had my doubts about it ever happening. Even if we never get a TOE, there is much we can still learn about the universe.

I'm interested in any thoughts you might have about the direction things are going. What do you think.

Wilgory

I think we need to forget about a TOE and concentrate on the cosmological constant/dark energy, we need to make small steps, i would be very happy
if any of the unknown parts of the universe were found, i mean DE is 70%?
an yet we have no idea what it is, we exist in the less than 1% of the known
stuff of the universe, i think cosmology is wide open to discovery and am willing to bet on major changes or a total stagnation.

wilgory , i know a lot of scientists will howl at this, but we do not have a
ruler to measure the universe with, some will say SNs are a ruler ,but how
can that be, we are only (measuring) one thing in our local enviroment,
an enviroment that is no way fixed AFAIK as yet to the universe as a whole.

Ik weet het niet.

Space-time curvature can't be fundamental because it breaks down at large masses and small distances---i.e. at the beginning and inside a black hole. Space-time curvature can ONLY be an effective description, and so GR MUST be an effective theory.

BenTheMan,

Do you consider the distance to the Gravity Probe B satellite is a great diatance from the earth. Even though the effects are small the gyroscopes have detected the curvature caused by the mass of the earth.

Also, are you saying that you know what goes on inside a blackhole. As there can be no observation I believe we can only speculate about the interior of blackholes. Although It's over my head I've read enough to know that there is no consensus on the physics involved.

Its obvious your education in these matters is more complete than mine so please keep your responses as simple as possible.

Thanks for you consideration,

Wilgory

fishtail,

It seems there is another ruler that has confirmed the distances derived from SN redshifts. Heres a PDF file that is easy to read.

http://cmb.as.arizona.edu/~eisenste/acousticpeak/acoustic.pdf

For more info, search for "baryon acoustic oscillations" and you will find many sites with the technical stuff.

Wilgory

Do you consider the distance to the Gravity Probe B satellite is a great diatance from the earth. Even though the effects are small the gyroscopes have detected the curvature caused by the mass of the earth.

I'm not saying that GR isn't right---that's CLEARLY not the case. But think of it like this. Suppose you have a picture that you printed out in your laser printer of a duck. If you look at the duck from a normal distance, it looks just like a duck. But if you look at it closer and closer, you'll see not a duck but a bunch of yellow dots.

This is like GR. If you look at big distances, gravity looks like curvature of space-time. But if you look at the universe at smaller and smaller distances, the curvature picture breaks down.

This is what ``effective theory'' means.

You mean there is a background space-time?

Yeah that's what GR is, or at least the way I understand it.

Well I thought that GR says gravity is all there is, gravity is actually space-time.

temur,

Currently, all that can be said, is that mass causes a warping of space-time, which is the cause of gravity. There is a theoretical particle, called the graviton, that would be the "force carrier" for gravity. It is still hypothetical, but the search is on. As is the search for gravity waves. The graviton would be similar to the photon, and have both the properties of a wave and particle.

We should not get ahead of ourselves. It is easy to do, with people that want to sell magazines or attract people to their website, sensationalizing the stories about what is happening in Quantum Physics and Astrophysics.

Hopes this helps.

Wilgory

temur,

Currently, all that can be said, is that mass causes a warping of space-time, which is the cause of gravity. There is a theoretical particle, called the graviton, that would be the "force carrier" for gravity. It is still hypothetical, but the search is on. As is the search for gravity waves. The graviton would be similar to the photon, and have both the properties of a wave and particle.

We should not get ahead of ourselves. It is easy to do, with people that want to sell magazines or attract people to their website, sensationalizing the stories about what is happening in Quantum Physics and Astrophysics.

Hopes this helps.

Wilgory
The graviton is a postulated particle of quantum field theory, not General Relativity. The graviton is a replacement mechanism for the curved spacetime of GR.

2inquisitive,

The goal is to unite the quantum fields and General Relativity. This might happen by quantifying gravity. Curved space as the cause of gravity can't be totally replaced because the gyroscopes used in the gravity probe b experiments have detected that curvature. If gravity is caused solely by particle attraction, the the gyroscopes would not have reacted the way they did. Which is why gyroscopes were used, and why the experiment is considered a test of General Relativity, and not just a test of gravity.

Wilgory

How about "general relativizing" quantum theory? Is there anything in this direction?

temur,

Good question. I've never heard or thought about that process. If the field theories and GR are united, I think both will be modified in some way. Quantum Physics is a whole lot farther over my head than GR. While GR is said to be counter-intuitive, it is said that nobody really understands quantum physics. Just the difference in the way time is thought of is a major stumbling block. In GR, time is considered to be a dimension, while in quantum physics it is considered a measurement of change. I read a lot of debate about this and have no idea how this difference might be resolved. I think time might be the one problem that is insurmountable. As I said in an earlier post, I follow the science, not do it. This is getting off topic so I apologize to everyone and will stop here.

Wilgory

2inquisitive,

The goal is to unite the quantum fields and General Relativity. This might happen by quantifying gravity. Curved space as the cause of gravity can't be totally replaced because the gyroscopes used in the gravity probe b experiments have detected that curvature. If gravity is caused solely by particle attraction, the the gyroscopes would not have reacted the way they did. Which is why gyroscopes were used, and why the experiment is considered a test of General Relativity, and not just a test of gravity.

Wilgory
temur stated in an earlier post that in General Relativity, curved spacetime was gravity. You responded to him about the search for the graviton. I informed you that the graviton was not a part of GR, but quantum field theory instead. Understand now? The pole options are the first option for GR, or the second option for Quantum field theories/String theories for the graviton. Yes, everyone is aware of many different ongoing attempts to unify GR and particle theories. So far, all attempts to detect either the theorized gravity waves of GR, or the gravitons of particle theories, have both been unsuccessful. The upcomming LISA experiment will be an attempt to differentiate between GR and various scalar-tensor theories such as Brans-Dicke theory. And of course, the LHC will search for the graviton of particle theories, in addition to the Higgs boson, etc.

General Relativity is Background Independent.

There are no actual "gravitons" in terms of particles travelling between masses, because gravity is a geometrical pseudoforce. The graviton is best considered as an accounting unit for calculation. In addition there are no "gravity waves", because there has to be some mass/energy stress associated with it. However you can have gravity tides, which is perhaps a better way of thinking about it. There's nothing to say these can't be rapid.

Hi Farsight,
In the GR model, gravity waves do have energy associated with them.They carry energy away from their source.
This page (http://www.astrophysicsspectator.com/topics/generalrelativity/GravitationalWaves.html) says:

the binary pulsars PSR1913+16 and PSR J0737-3039 have orbits that are decaying in the way expected if they were losing energy to gravitational radiation.

I also recall reading that when two black holes merge, a large percentage of their mass-energy is radiated away as gravity waves, but don't rely on that because I can't find a source.

It's terminology, Pete. Interpretation. You can't have mass/energy without gravity, and vice-versa. In this respect a photon is a "gravity wave".

What is the nature of gravity?

Is it a result of space/time curvature as general relativity suggests?

Or is it a quantum field? If it is a field, what is the nature of the carrier (graviton)? Vibrating strings, spin networks, etc.?

Perhaps something else entirely?


Gravity is expansion energy from the beginning of time ie. that we see far out in space. It moves to us in the speed of light

This explains the 1a star explosion variations.

When you move your hand (electrical impulses), it's the same principle as when a planet attracts something (because electromagnetism = gravity), but because of our body's structure we can lead the energy in much greater freedom.

Like all mass, human bodies physically attract objects by default, but it's not visible because we're parts of earth's attraction. However, when we learn to focus better we no longer need to use nature's unconscious attraction, we can move physical things with our thoughts like we now can use our hands. We can levitate our body and fly like the-people-before-us-who-did-not-need-airplanes did.

So... the nature of gravity is thoughts, feelings (love, attraction), telekinesis.

It's all about the number value an object holds.

I put something else.

Gravity is a word, used for over 500 years, to describe TWO fundamentally different sets of mechanics.

Can we please throw Newton out of the window once more and get on with some real science, instead of trying to get a single (rather bizarre) model to fit TWO different things!!!!
(Pretty please)

kaduseus

I have a strong suspicion about how gravity works but I am not allowed to say it in detail on this forum. So I checked Other. You can find my thoughts about it by visiting my web site links in my profile. Basically it derives from the quantum nature of electromagnetics.

Looks like this thread has run out of science!