What is gravity?

[shane.mcneil]

I've been reading up on gravity, wondering exactly what it is. I thought it was a simple question but seems it's not.

From what I understand, Newton imagined gravity as a force of attraction of some kind, but he didn't know what exactly.

Einstein "corrected" Newton's physics with relativity and said that gravity is a result of the geometry of the universe and not a force.

But relativity doesn't work on the quantum level and so they believe there must be a quantum explanation for gravity which leads it back to being a force. Hence the graviton.

Am I getting any of this right? Does anyone know exactly what gravity is?

Regards

Shane

[mswhin63 (Malcolm)]

I was watching a program Catalyst which talk a little about the theory of gravity, mostly though it talks more about confirming Einteins theory of special relativity.

To me it was a basic explanation, take a look;

http://www.abc.net.au/catalyst/stories/2594259.htm

[jjjnettie (Jeanette)]

The illusive Unified Theory eh.
I'm just a checkout chick, and it hurts my little button brain thinking about stuff like this.
But doesn't the fact that gravity can bend light, take it down to the quantum level?

[shane.mcneil]

Thanks for that. I did see that story. From what I understand relativity works very well in the universe at large but it fails when applied to the atomic level. So, many believe there is more to it???

[shane.mcneil]

Originally Posted by jjjnettie

The illusive Unified Theory eh.
I'm just a checkout chick, and it hurts my little button brain thinking about stuff like this.
But doesn't the fact that gravity can bend light, take it down to the quantum level?

Um I'm not sure. The bending of light is described by relativity. An object bends spacetime (we call that gravity) and so light traveling through that spacetime will be "bent". That's how they confirmed relativity. By looking at star positions during a solar eclipse. They demonstrated that the sun was bending the light from stars that where behind it. Einstein didn't like Quantum Theory.

[jjjnettie (Jeanette)]

He spent most of his youth as a free thinker, only to end up like all those professors he disliked. Stuck in a rut. Not allowing himself to think outside the square.

[shane.mcneil]

Yeah, maybe that's the problem now. We have dark matter that no one really seems to know what it is. Dark energy that is the same. Relativity almost works. And Quantum Theory though really weird, almost works too.

I can't help but think there is something profound that we are missing, rather than just a simple "we can merge this together".

[multiweb (Marc)]

Originally Posted by mswhin63

I was watching a program Catalyst which talk a little about the theory of gravity, mostly though it talks more about confirming Einteins theory of special relativity.

To me it was a basic explanation, take a look;

http://www.abc.net.au/catalyst/stories/2594259.htm

Great video. You have to give it to these guys for their tenacity in all their ordeal. Having the technology to make such a precise Gyro system and measurement intrumentation is one thing but what totally blows my socks off is Einstein Theory still being proven right. This bloke had a truly amazing mind. How do you even start thinking about that kind of stuff. Wow..

[marki]

Right then, whose got a rubber sheet and canon ball . Truth is no one is really sure what causes gravity. It is one of the greatest mysteries of our time. There are lots of theories out there but all they can really conclude is that gravity sucks. Where is Carl when you need him, sure he would have lots to say about this.

Mark

[Robh (Rob)]

There are those more qualified to respond but here's my viewpoint.

Gravity is the name given to the attractive force generated by matter. The more the matter, the greater the force. So, I guess the real question is why does matter produce this force? Gravity is believed to act at the speed of light and possibly be messaged by a particle called the graviton. There are even experiments underway to see if gravity waves exist.
Locally, our measurements of this force say that it varies as the inverse square of the distance from a massive body. So here on Earth, Newton's Laws work fine. Massive bodies bend or warp space-time so that, on a larger scale, the laws need modifying according to Einstein's General Relativity. Observations of the speed of stars on the outer edges of galaxies have led to the dark matter hypothesis. However, dark matter may not exist. It is possible that gravity works differently at distance to what we expect and the equations need modifying (MOND). On a quantum level, we don't know how gravity fits in.
In Physics, theory can be generated from observation and measurement (Newton and the falling apple) and sometimes by modelling and testing predictions (Einstein and GR). String Theory has attempted to produce a quantum theory of gravity without success as yet. Maybe, we just aren't smart enough!

Regards, Rob

[marki]

Originally Posted by Robh

String Theory has attempted to produce a quantum theory of gravity without success as yet. Maybe, we just aren't smart enough!

Regards, Rob

But which string theory are we talking about Rob.

Mark

[renormalised (Carl)]

I'm right here, Mark

Just been offline for a few days

I'll make comment on this later, it's getting rather late now. However, I'll leave you with this...speaking about dark matter and energy. Has anyone ever considered that the micro-fluctuations of spacetime at the quantum level, generating virtual particle pairs, is what is causing galaxies and such to have the anomalous rotation curves we see. Remember, these particle, whether they're virtual or not (unless they're force carriers such as photons, gravitons etc), have mass. Now what acts as the carrier particle for mass...the Higgs boson. The Higgs actually is much heavier than the particles it gives mass to (it's some 100-1000 times heavier than a proton). No matter how fleeting the Higgs might last for, it still must interact with spacetime and create an effect. No matter how fleeting the creation of virtual particle pairs is, how fleeting their existence and how fleeting the creation of mass is...you only have to look at how big space is to see that the effects produced are going to add up. These virtual particle aren't just being produced in extreme situations like black hole event horizons. They're a consequence of the "frothy" nature of spacetime, everywhere.

Anyway, it's something I feel they need to consider...that there's a lot more out there that needs to be factored into their equations before they go trying to find something really exotic. The answer to the problem might be sitting right under their noses and they're too busy trying to be smart to see the answer.

More to come later

[Robh (Rob)]

Originally Posted by marki

But which string theory are we talking about Rob.

Mark

Hi Mark.
I'll pick one ... bosonic string theory. Now I have reached my level of incompetence!
However, what Carl says is quite interesting. Look forward to the experiments of the Large Hadron Collider at CERN to see if they can confirm the existence of the Higgs boson. Exciting stuff!

Regards, Rob.

[TrevorW]

Simply put it's the force that keeps your bum pointing in the right direction

just imaging the sh.. we'd be in without it

[Kevnool (Kev)]

Put a beer up to your mouth and pour it in and let gravity take over.

Cheers Kev.

[AlexN]

I would recommend that anyone interested in gravity buy the book "gravity from the ground up" its expensive... It cost me $140.. It was worth every penny.. although it does seem to pose more questions than it answers. For me, I like that... It gives me a start for my own research as opposed to giving me an answer...

Gravity is not the hard part to understand, its getting your head around why gravity is how it is.. and furthermore, Quantum Gravity... Talk about food for thought...

[TrevorW]

What about

Universal
Galactic
Solar
Planetary
Molecular
Atomic
Black Holes

all have different strenghts and interelate

[jjjnettie (Jeanette)]

Originally Posted by shane.mcneil

I can't help but think there is something profound that we are missing, rather than just a simple "we can merge this together".

And we'll find out what that "something" is, hopefully sooner than later.
Won't that just rock the foundations of physics. It will open our eyes in so many different ways. I hope I'm around when it happens.

[avandonk]

Originally Posted by renormalised

I'm right here, Mark

Just been offline for a few days

I'll make comment on this later, it's getting rather late now. However, I'll leave you with this...speaking about dark matter and energy. Has anyone ever considered that the micro-fluctuations of spacetime at the quantum level, generating virtual particle pairs, is what is causing galaxies and such to have the anomalous rotation curves we see. Remember, these particle, whether they're virtual or not (unless they're force carriers such as photons, gravitons etc), have mass. Now what acts as the carrier particle for mass...the Higgs boson. The Higgs actually is much heavier than the particles it gives mass to (it's some 100-1000 times heavier than a proton). No matter how fleeting the Higgs might last for, it still must interact with spacetime and create an effect. No matter how fleeting the creation of virtual particle pairs is, how fleeting their existence and how fleeting the creation of mass is...you only have to look at how big space is to see that the effects produced are going to add up. These virtual particle aren't just being produced in extreme situations like black hole event horizons. They're a consequence of the "frothy" nature of spacetime, everywhere.

Anyway, it's something I feel they need to consider...that there's a lot more out there that needs to be factored into their equations before they go trying to find something really exotic. The answer to the problem might be sitting right under their noses and they're too busy trying to be smart to see the answer.

More to come later

Not to mention quantum entanglement that must be nearly everywhere by now considering all the particle interactions since the big bang. If there is some sort of dying off (inverse square or even fractal law with each interaction) effect in 'strength' of QE after each particle interaction it would explain why it hangs around crowds (galaxies) of 'normal' matter. It may even ultimately explain gravity.

So here we have two proven phenomena open to measurement.

1. Quantum Entanglement.
2. Virtual Particles.

I still find it hard to imagine that all my desires for bright shiny things is governed by the fleeting existence of invisible particles.

By the way the only thing that can explain quantum entanglement is that the bits of separated matter produced after the interaction are still the same entity as far the resultant bits are concerned. This also brings into the whole scenario the concept of time. If you are a bit confused don't worry. It is hard enough to put these esoteric concepts into words let alone understand them.

Bert

[sjastro]

Originally Posted by renormalised

I'm right here, Mark

Just been offline for a few days

I'll make comment on this later, it's getting rather late now. However, I'll leave you with this...speaking about dark matter and energy. Has anyone ever considered that the micro-fluctuations of spacetime at the quantum level, generating virtual particle pairs, is what is causing galaxies and such to have the anomalous rotation curves we see. Remember, these particle, whether they're virtual or not (unless they're force carriers such as photons, gravitons etc), have mass. Now what acts as the carrier particle for mass...the Higgs boson. The Higgs actually is much heavier than the particles it gives mass to (it's some 100-1000 times heavier than a proton). No matter how fleeting the Higgs might last for, it still must interact with spacetime and create an effect. No matter how fleeting the creation of virtual particle pairs is, how fleeting their existence and how fleeting the creation of mass is...you only have to look at how big space is to see that the effects produced are going to add up. These virtual particle aren't just being produced in extreme situations like black hole event horizons. They're a consequence of the "frothy" nature of spacetime, everywhere.

Anyway, it's something I feel they need to consider...that there's a lot more out there that needs to be factored into their equations before they go trying to find something really exotic. The answer to the problem might be sitting right under their noses and they're too busy trying to be smart to see the answer.

More to come later

You are only seeing an effect over the period of time the virtual particles are in existence. The effects don't "add up" otherwise the conservation of mass and energy is violated.

The point is that virtual particles pop in and out of existence in very short period of time. (Try calculating the time it takes for a photon traveling at the speed of light to go from one "side" of a proton to the other to appreciate the time frames involved).

The fact is that a vacuum which is in a lowest quantum energy state doesn't gain energy despite the appearance (and disappearance) of virtual particles.

Steven