What is gravity?

[AlexN]

Physics governs all that you've listed there Trevor, Unfortunately, the best physicists have been working on understanding all this since the late 1800's.. And as you can imagine, they are still coming up with more questions than answers..

Dark Energy and Dark Matter are a great example. People are trying to tear these theories apart, or figure out how the theories are incorrect, however without these exotic particles in universe, then our understanding of both the universe, and gravity are pretty inaccurate. Gravity controls universal expansion, its speed is a direct result of both the speed at which it was set into motion by the big bang way back when, and the force of gravity upon the matter. Gravity being based on mass, seems to indicate that if the theories on exotic particles like dark matter and dark energy are incorrect, we should be seeing much greater, faster expansion than we are. Clearly, there needs to be more mass in the universe than we are aware of. Even knowing that there is clearly a lot of black holes we're not aware of, and a lot of netron stars etc that do have a lot of mass, and exert a great deal of gravitational force. However, even when allowing for heaps and heaps of these, there is still not enough mass within the universe to have the rate of expansion as it currently is..

There is another problem, if you introduce dark matter and dark energy, then gravity should not be as weaker force as it is. As I mentioned, gravity is governed by mass. if you introduce more mass, there should be a coresponding increase in gravitational presence..

Unless...

How do we all feel about the notion of parallel/alternate universes? the Multivesrse theory?

Lets assume for a moment that gravity is a single constant force divided between, say, 10 different parallel universes. Then, the force of gravity being so week is a lot more understandable. Obviously, the idea of multiple universes, alternate realities and extra dimensions seems a lot like science fiction. Think though, four hundred years ago, the idea that the earth was not the centre of the universe was considered science fiction... the idea of planets orbiting other stars was considered science fiction... Hell, the idea that the Earth revolved around the sun as opposed to the sun revolving around Earth was considered herecy...

[kinetic (Steve)]

Originally Posted by jjjnettie

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.

Here's my opinion on trying to understand the universe.:

Maybe we just can't or never will.
Our species is (arguably) the result of evolution getting us to
this point of self awareness and knowing our position in the universe.
Maybe just by pure accident or maybe by divine plan.

We are perfectly comfortable looking at the universe from our
perspective.
Our intelligence allows us that. But we start to look further
and question things.

Whales are supposed to be the next species almost as enlightened
as us.
They perceive their world exactly the same way, to the limit their
intelligence allows them.

But, to a whale, concepts such as spaceflight and molecular
structure would be as foreign as wormholes and a unified theory
are to us....
We seem to know there is something just around the corner waiting
for us to know...but something holds us back from that knowledge.
I reckon it's just our intellect.

In 250(?) million years of life, that little window of self awareness
we are at now only occupies a time window of maybe the last 100 years.
Maybe even a few 1000 even (we don't know how they built the pyramids for example!)
Just a blink of an eye when compared to 250 million years.

Maybe we need another few million years to bridge that gap.

And that gets me to the second point.
Where is everyone else!? Why don't we hear from them?

Maybe a civilisation gets itself to this point of self awareness
in a tiny time window of a few hundred/thousand years and then it snuffs out
due to the instinctive aggressive/survival behaviour it carries along like
baggage from the process of evolution.

For two of those time windows to overlap in even just our neck of the woods
of this galaxy, so that we make contact with that civilisation are
probably impossible odds.

Maybe that's why it's so quiet out there?
And why we should look after the place a bit better

Steve

[avandonk]

The Universe gets over infinities by having an indeterminate level at the Heisenberg uncertainty level to bring these concepts into historical perspective. Buckminster was an advocate of this. The concept of an infinitely smooth function as the basis for reality leads to major problems. Fractals can overcome this as it only depends on the number of iterations to get the complexity needed at any scale.

Bert

[avandonk]

Originally Posted by kinetic

Here's my opinion on trying to understand the universe.:

Maybe we just can't or never will.
Our species is (arguably) the result of evolution getting us to
this point of self awareness and knowing our position in the universe.
Maybe just by pure accident or maybe by divine plan.

We are perfectly comfortable looking at the universe from our
perspective.
Our intelligence allows us that. But we start to look further
and question things.

Whales are supposed to be the next species almost as enlightened
as us.
They perceive their world exactly the same way, to the limit their
intelligence allows them.

But, to a whale, concepts such as spaceflight and molecular
structure would be as foreign as wormholes and a unified theory
are to us....
We seem to know there is something just around the corner waiting
for us to know...but something holds us back from that knowledge.
I reckon it's just our intellect.

In 250(?) million years of life, that little window of self awareness
we are at now only occupies a time window of maybe the last 100 years.
Maybe even a few 1000 even (we don't know how they built the pyramids for example!)
Just a blink of an eye when compared to 250 million years.

Maybe we need another few million years to bridge that gap.

And that gets me to the second point.
Where is everyone else!? Why don't we hear from them?

Maybe a civilisation gets itself to this point of self awareness
in a tiny time window of a few hundred/thousand years and then it snuffs out
due to the instinctive aggressive/survival behaviour it carries along like
baggage from the process of evolution.

For two of those time windows to overlap in even just our neck of the woods
of this galaxy, so that we make contact with that civilisation are
probably impossible odds.

Maybe that's why it's so quiet out there?
And why we should look after the place a bit better

Steve

We humans have one advantage. We pass on knowledge by non genetic means. Since the printing press even the knowledge of previous generations are accessible to nearly all in an almost unadulterated form.

Whales and dolphins etc have an aural view of the Universe. They see their world in 3D with the equivalent of sonar. Vision in 3D is our major strength. Why the size of brains is large in all of us is the huge amount of processing needed in both aural and visual methods to get a 3D 'view'. The neural connections are so vastly different that we may never communicate in any meaningful way.

Bert

[marki]

Why do I feel this thread is going to end by posing several thousand more questions then anwers . Bert your mention of the Heisenberg uncertainty principle had me on the floor in stiches. Imagine if you will an ewok who spoke like donald duck with lips. That was my phys chem lecturer at uni, he could never get that out without us plebs lying on the floor in fits of laughter.

Mark

[Robh (Rob)]

Originally Posted by AlexN

How do we all feel about the notion of parallel/alternate universes? the Multivesrse theory?

Lets assume for a moment that gravity is a single constant force divided between, say, 10 different parallel universes. Then, the force of gravity being so week is a lot more understandable. Obviously, the idea of multiple universes, alternate realities and extra dimensions seems a lot like science fiction. Think though, four hundred years ago, the idea that the earth was not the centre of the universe was considered science fiction... the idea of planets orbiting other stars was considered science fiction... Hell, the idea that the Earth revolved around the sun as opposed to the sun revolving around Earth was considered herecy...

I hope that this is not the case and that the Universe is not that convoluted. I'm gambling on some simple missing details that are leading scientists into unnecessarily complex solutions.

Regards, Rob

[avandonk]

Originally Posted by marki

Why do I feel this thread is going to end by posing several thousand more questions then anwers . Bert your mention of the Heisenberg uncertainty principle had me on the floor in stiches. Imagine if you will an ewok who spoke like donald duck with lips. That was my phys chem lecturer at uni, he could never get that out without us plebs lying on the floor in fits of laughter.

Mark

Any sort of Chemistry Lecturer would choke on quoting quantum theory from the thirties. I have worked with many theoretical chemists working on protein structure prediction. They are quite at home with quantum theory as their work is meaningless without it.

If you want to get really pedantic our best calculations can model the hydrogen atom (one proton + one electron) perfectly. We fail with the hydrogen molecule (two protons + two electrons). It is called the multi body problem. With supercomputers the models are better.

The only supercomputer capable of solving protein structure is the molecule itself!

I did not want to elaborate to far as to start to understand the Universe will take every tool at your disposal. Even then you or I will be found to be wanting.
Bert

[marki]

Originally Posted by avandonk

Any sort of Chemistry Lecturer would choke on quoting quantum theory from the thirties. I have worked with many theoretical chemists working on protein structure prediction. They are quite at home with quantum theory as their work is meaningless without it.

Bert

Absolutely, I remember it being a major component of kinetic and thermodynamic units. Protien structure and synthesis is fascinating stuff isn't it . I went back and did a biotech degree in the 90's for fun. Might have to look at doing another one in astronomy me thinks but all this dark matter/dark energy theory pee's me off .

Mark

[AlexN]

Mark, Im studying physics at the moment and I can tell you, when professors start talking about gravity or astro physics, the dark matter/dark energy stuff comes up.. Its impossible to avoid or ignore apparently...

[shane.mcneil]

Well here I was feeling a bit dumb cos I couldn't get my head around gravity. It seems that nobody anywhere has ever been able too. I feel much better. Thanks everyone for your comments.

So am I right in thinking that relativity is currently the working model of gravity even though it is incomplete? All of the discussion on Quantum Gravity seems to be theories and ideas without any verification. Everyone thinks there is a quantum explanation but nobody knows what.

That being the case, gravity as we currently understand it, is not a force of attraction but rather what happens to an object when it moves through the curved space caused by another object. Until someone proves otherwise that is...

[marki]

Originally Posted by shane.mcneil

That being the case, gravity as we currently understand it, is not a force of attraction but rather what happens to an object when it moves through the curved space caused by another object. Until someone proves otherwise that is...

Like I said, has anyone got a rubber sheet and a canon ball .

Mark

[AlexN]

Relativity is the current working model.. Quantum gravity is still infantile, It has not had the time to establish itself like relativity has.. Who knows what the future will hold for quantum gravity, and indeed, perhaps a unified quantum theory of everything..

[avandonk]

Shane back in 1967 (in year twelve) we had to work out what was the gravitational attraction between a 70kg boy and a 55kg girl using the usual formula. As it turned out it was not much.

Bert

[shane.mcneil]

Originally Posted by avandonk

Shane back in 1967 (in year twelve) we had to work out what was the gravitational attraction between a 70kg boy and a 55kg girl using the usual formula. As it turned out it was not much.

Bert

I would have thought the answer would = love. Maybe that's what holds the Universe together.

[marki]

Originally Posted by AlexN

Mark, Im studying physics at the moment and I can tell you, when professors start talking about gravity or astro physics, the dark matter/dark energy stuff comes up.. Its impossible to avoid or ignore apparently...

Alex, start asking some curly questions and watch it disappear. You know you have them on the ropes when they duck into the toilet everytime they see you coming down the hall . I am hoping there will be some "real" clarification from the experiemnts being conducted at the LHC.

Mark

[kinetic (Steve)]

Originally Posted by avandonk

Shane back in 1967 (in year twelve) we had to work out what was the gravitational attraction between a 70kg boy and a 55kg girl using the usual formula. As it turned out it was not much.

Bert

Bert , my experience of this attraction force was slightly different.
Between Yr 10 girls and us Yr 10 boys there was no detectable
attraction at all. Only between Yr 10 girls and Yr 12 boys.
It had me puzzled well into my adult years.

Steve

[AlexN]

Indeed - the LHC could be quite the problem solver with regards to much of physics.. I would love to be a part of that project.. I was wondering if you could build a miniature for home use... an SHC if you will...

[marki]

Sure, with a bottle of hydrogen, a big piece of ali tube turned into a spiral, a few dozen super magnets and a kick ass power supply. put it all in the freezer and the universe is your play thing .

Oh did I mention the oxy? You will need that to ionise the gas on the way in, good luck .

Mark

[sjastro]

Originally Posted by shane.mcneil

Well here I was feeling a bit dumb cos I couldn't get my head around gravity. It seems that nobody anywhere has ever been able too. I feel much better. Thanks everyone for your comments.

A lot of post graduates feel dumb struggling with the mathematics but that is another story.

So am I right in thinking that relativity is currently the working model of gravity even though it is incomplete? All of the discussion on Quantum Gravity seems to be theories and ideas without any verification. Everyone thinks there is a quantum explanation but nobody knows what.

Newtonian theory is still the major contributor to celestial mechanics. General relativity is used where Newtonian theory fails such as planetary orbits near stars, gravitational potentials of neutron stars, black holes etc.

General relativity provides the framework for cosmology.

General relativity is incomplete with regards to the very early history of the Universe where gravity was unified with the strong, weak and electromagnetic forces.

This where Quantum Gravity comes into the picture. Unfortunately Quantum Gravity is a theoretical mess as the mathematics produces infinite solutions for basic interactions between objects.

That being the case, gravity as we currently understand it, is not a force of attraction but rather what happens to an object when it moves through the curved space caused by another object. Until someone proves otherwise that is...

General relativity describes gravity as a "fictitious" force, much like the backward force that pushes you into your car seat as you plant your foot on the accelerator.
Curved space is simply gravitational field lines. An object traveling along the shortest pathway in curved space travels in an inertial frame and doesn't experience gravity as a force.

Regards

Steven

[avandonk]

Originally Posted by kinetic

Bert , my experience of this attraction force was slightly different.
Between Yr 10 girls and us Yr 10 boys there was no detectable
attraction at all. Only between Yr 10 girls and Yr 12 boys.
It had me puzzled well into my adult years.

Steve

So why did we keep banging together?

bert