Is Gravity More Than Just a Force? Exploring the Possibility of a Unified Theory

[LizardKing23]

this is just a thought I've been toying around in my head for the past 6 minutes after reading one of the posts.

gravity warps space and time. commonly recognized fact. but, this feature of gravity is exclusive to gravity. the strong and weak forces, and electromagnetism do not display this characteristic. in a unified theory, wouldn't these forces, at some point, have to share this characteristic? and if this is true, wouldn't a unified theory be impossible UNLESS gravity was thought of as a completely separate entity? is gravity something more than just the fourth force? i am not suggesting deistic influence or advance civilizations messing with us, I am just wondering if we're thinking about gravity all the wrong way.

food for thought.
enjoy.

 

[misskitty]

Yummy...I love food for the brain.

There must be some other place in the universe that exhibits the gravity thing your talking about. It's interesting that strong, weak, and EM do not display this. There must be some reason we haven't found or discussed yet as to why this is. I think you might be on to something with the impossible unified theory IF it were true and gravity were a separet entity all together. However, what would gravity be a separet entity from? This poses a new query to throw into the mix. As well as how would this affect the current calculations we use to learn about the universe? I would think some of the theories concerning gravity may have to be adapted to compensate for gravity being a separted entity.

 

[quasar987]

this is just a thought I've been toying around in my head for the past 6 minutes after reading one of the posts.

gravity warps space and time. commonly recognized fact. but, this feature of gravity is exclusive to gravity. the strong and weak forces, and electromagnetism do not display this characteristic.

The relativity gurus of this forum will tell you it is not gravity that bends space, it is not even matter, it is the energy stress-tensor (or something like that)... in other words, it is energy.

But it is well known that a photon curves space-time as well, for it carries an energy hf... But a photon is but an electromagnetic wave. Hence the energy contained in the oscillating electric and magnetic fields curves space-time. So the feature of curving space is not exclusive to gravity (or MATTER).

 

[inquire4more]

The relativity gurus of this forum will tell you it is not gravity that bends space, it is not even matter, it is the energy stress-tensor (or something like that)... in other words, it is energy.

But it is well known that a photon curves space-time as well, for it carries an energy hf... But a photon is but an electromagnetic wave. Hence the energy contained in the oscillating electric and magnetic fields curves space-time. So the feature of curving space is not exclusive to gravity (or MATTER).

Well, ok, but a photon does possesses some mass. I agree that a stress tensor gives the measure of the, well, the stress, on a region of space-time due to other, surrounding regions, affecting curvature, but it still seems to me that it is matter that warps space-time. If one of the relativity gurus is around, I'd be interested to know their thoughts. How does the stress tensor differ from this relativistic stress-energy tensor?

 

[quasar987]

Photons have no mass.

As a demonstration, consider the following two relations derived directly from the Lorentz transformations:

$$\vec{p}c^2 = \vec{v}E$$

$$E^2 - (pc)^2 = (mc^2)^2$$

v = c in the first one gives pc = E. This last result in the second equation give

$$0 = (mc^2)^2 \Leftrightarrow m = 0$$

 

[AntonVrba]

this is just a thought..., I am just wondering if we're thinking about gravity all the wrong way.

food for thought.
enjoy.

yes that is food for thought, gravity might be something completely deifferent than what we thought up till now- but then many new theories need to be developed - a long slow progress.

 

[inquire4more]

Photons have no mass.

As a demonstration, consider the following two relations derived directly from the Lorentz transformations:

$$\vec{p}c^2 = \vec{v}E$$

$$E^2 - (pc)^2 = (mc^2)^2$$

v = c in the first one gives pc = E. This last result in the second equation give

$$0 = (mc^2)^2 \Leftrightarrow m = 0$$

Hmmm...I cannot argue with the math. I'm going to have to read a little on this and give it some thought, and you have, most definitely, given me something to think about, quasar.

 

[inquire4more]

$$\vec{p}c^2 = \vec{v}E$$

Here then, $$\vec{p}$$ represents momentum? Or did I miss by a mile here? If so, does this differ in some way from momentum as it is treated classically?

 

[quasar987]

I was hoping you wouldn't ask. :tongue2:

The relativistic momentum is defined as

$$\vec{p} = \frac{m\vec{v}}{\sqrt{1-(v/c)^2}}$$

But for a photon, this relationship explodes because v = c makes the denominator 0.

However, it had been discovered by Einstein a few months prior to the publication of his first paper on special relativity that the energy of a photon is directly proportionnal to its frequency: $E = h\nu$. So this, together with $pc^2 = vE$, allows us to give a special definition of momentum to photons:

$$p = \frac{h\nu}{c}$$

 

[inquire4more]

Sorry to be a bother about this quasar, but do you know where I could go to find out exactly how Einstein arrived at $E = h\nu$? I'm not disputing the validity, but it might help me to understand the why, if only I can see the how.

 

[Crosson]

is gravity something more than just the fourth force?

In General Relativity, gravity is not a force. That is, it does not even remotely resemble a force in highly relativistic situations.

 

[quasar987]

I don't know where to go about finding this but I can tell you that he figured that out in trying to explain the photoelectric effect. The photoelectric effect is the observation that when a photon collides with an elektron, the photon is "absorbed" and the elektron's kinetic energy is augmented by an amount exactly equal to...you guessed it, $h\nu$.

 

[Sempiternity]

"Force is an illusion, a by-product of warped space-time." - Michio Kaku

 

[misskitty]

The relativity gurus of this forum will tell you it is not gravity that bends space, it is not even matter, it is the energy stress-tensor (or something like that)... in other words, it is energy.

But it is well known that a photon curves space-time as well, for it carries an energy hf... But a photon is but an electromagnetic wave. Hence the energy contained in the oscillating electric and magnetic fields curves space-time. So the feature of curving space is not exclusive to gravity (or MATTER).

Quasar, how does a photon curve space-time ? I don't know much about them because I have just started to study them.

 

[misskitty]

Photons have no mass.

As a demonstration, consider the following two relations derived directly from the Lorentz transformations:

$$\vec{p}c^2 = \vec{v}E$$

$$E^2 - (pc)^2 = (mc^2)^2$$

v = c in the first one gives pc = E. This last result in the second equation give

$$0 = (mc^2)^2 \Leftrightarrow m = 0$$

Being a high school student who does not yet posess the required mathematical background to comprehend what you just typed...what does this mean?

 

[misskitty]

In General Relativity, gravity is not a force. That is, it does not even remotely resemble a force in highly relativistic situations.

Not to sound like a complete moron , but my GR background is like my knowledge of photons. How is it that gravity is not a force? Gravity is the attracting force between matter. How does that work?

 

[misskitty]

Sorry to be a bother about this quasar, but do you know where I could go to find out exactly how Einstein arrived at $E = h\nu$? I'm not disputing the validity, but it might help me to understand the why, if only I can see the how.

This might help; I believe the paper concerning this was published with the math in 1920. That might narrow down your search. I don't remember who published it though, sorry.

 

[quasar987]

Quasar, how does a photon curve space-time ? I don't know much about them because I have just started to study them.

I can't give a better explanation than what I have said earlier. Energy curves space. Photons have energy. Hence, they curve space.

 

[quasar987]

Being a high school student who does not yet posess the required mathematical background to comprehend what you just typed...what does this mean?

I start from two equations of relativity to show that the mass of a particle moving at speed c (i.e. a photon) has no mass.

 

[misskitty]

I can't give a better explanation than what I have said earlier. Energy curves space. Photons have energy. Hence, they curve space.

Ah, fair enough. I think we need to find one of the relativity gurus ...lol. I can accept that explanation. So if energy curve space, does energy curve everything, in small amounts, or just space?

 

[misskitty]

I start from two equations of relativity to show that the mass of a particle moving at speed c (i.e. a photon) has no mass.

Makes sense. Does anything that moves at the speed of light not have mass?

 

[quasar987]

Not to sound like a complete moron , but my GR background is like my knowledge of photons. How is it that gravity is not a force? Gravity is the attracting force between matter. How does that work?

Another user, who goes by the name of 'infidel' wrote in another thread:

Einstein said there really is no 'force' of gravity. Mass warps spacetime into curves. Particles (or planets) move in as straight a line as they can in warped spacetime. This results in the appearance of a force.

So you could imagine that when you got enegy, or mass (which is but a big chunk of energy), space is BENT around it into a 4th dimension! And the motion of bodies passing nearby seems distorted by what would appear to be a force going in (1/r²), but actually they are only following a straight line in the 4 dimensional space.

 

[misskitty]

Cool. That fourth dimension would be time. Right?

 

[quasar987]

Ah, fair enough. I think we need to find one of the relativity gurus ...lol. I can accept that explanation. So if energy curve space, does energy curve everything, in small amounts, or just space?

Good question. What it means to "curve space" is that it will curve everything, not just void. Near a black hole, space is VERY curved and you could literally get diformed (ellongated like a spagetti) if you wander to close :)

 

[quasar987]

Makes sense. Does anything that moves at the speed of light not have mass?

This is what is implied by those equations, yes.

(I got to get off the computer now, cya)

 

[misskitty]

Very curved would be an understatement! :shocked:

 

[µ³]

Not to sound like a complete moron , but my GR background is like my knowledge of photons. How is it that gravity is not a force? Gravity is the attracting force between matter. How does that work?

I think I can provide a better general relativity explanation. Imagine you and a friend are standing next to each other and you both go exactly north. As you got further and further north you start getting closer together until you are finally in the exact same spot when you are in the north pole. If you did not know the Earth was spherical, you might think that there was a "force" pulling you together. This is the same thing with relativity. However one must note with this analogy that stress-energy does not just curve space but space-time and consequently masses in space (or more generally, stress-energy) curves space-time in such a way that it acts like a force at non-relativistic magnitudes.

 

[inquire4more]

Cool. That fourth dimension would be time. Right?

Whenever spaces, in general, are curved, they MUST be curved into a higher dimension. So if 4-dimensional space-time is curved, it cannot be curved in the fourth dimension, it would require the use of at least a fifth dimension. If we're only speaking of three spatial dimensions, they would be curved into a fourth dimension, but nothing (that I am aware of, someone interject if I am wrong; I'm speaking mathematically, not physically here) stipulates that they must be curved into a dimension of time.

 

[Tainted_Mint]

I don't get it.

If gravity isn't a regular "force", then why are they(scienists) saying that there is a gravity www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0028976.html[/URL](graviton)?