Thread: Gravity: does it distort or attract?

I'm a little confused as to the nature of gravity.

I often read about how it's a force of attraction between bodies with mass. From what I understand of General Relativity though, what we percieve as gravity is the distortion of space and time near a massive body. So a body moving through the distorted space/time doesn't change its' path it's the space/time that curves.

So which is it, is gravity a force of attraction or distortion?

Originally Posted by DarcgreY

I'm a little confused as to the nature of gravity.

I often read about how it's a force of attraction between bodies with mass. From what I understand of General Relativity though, what we percieve as gravity is the distortion of space and time near a massive body. So a body moving through the distorted space/time doesn't change its' path it's the space/time that curves.

So which is it, is gravity a force of attraction or distortion?

Let me pose a few questions and see, if from that, you can answer your own question;

1. Does light (a photon) have mass?
2. Does gravity influence ("bend") light?

What's your conclusion now?

Cheers,
william

Photons have mass and light is bent by gravitational fields.

I'm still not sure whether that's because light is following the curved space/time near a massive object or whether it's being attracted towards a massive object.

Photons have mass and light is bent by gravitational fields.

wow so close but not close enough. Photons DONT have mass, and is bent by gravity

its bent becuase it follows a straight line in 4D wich to us seem bending thou to gravity

I thought they'd determined that the photon had a tiny mass, but maybe I'm confusing it with the neutrino. It's hard to keep up with all these particles.

So the answer is, what we see as the effect of gravity is caused by the distortion of space/time?

yes

Originally Posted by DarcgreY

I'm a little confused as to the nature of gravity.

So is the whole of the rest of mankind, nobody understands it yet...

For something with mass to travel the speed of light require infinite energy as the theory of relitivity goes.

Light does travel, funnily enough, at the speed of light. (aka Light travels as fast as itself)

Lightbulbs do not expend infinite energy (aka all the energy in the universe) to turn on. Thus Light does not expend infinite energy.

Particles with Mass cannot occupy the same space at the same time.

White light is a large spectrum spread of light at the same time. Radio waves are light at a different frequency. Your radio can pick up the local radio station without the areal of the radio going dark and invisible. Thus radio waves (which is really just light at low frequency) and light (light at middle frequency) can exist in the same space at the same time

Thus Light has no mass.

Gravity attracts Mass.


The most obvious conclusion based on all the above assumptions would be that light is unaffected by gravity and does not change course from a straight line even when effected by gravity.

However light does bend from gravitational influence.

Assuming all the above assumptions are correct (and I think all of these are scientificly verifiable, maybe give or take a few)

Is that the straight line through space that light takes is bent... yes, the straight line is bent.

Try this: Draw a straight line on a piece of paper with a rule/r.

Fold crinkle the paper up and put some folds in it in uneven positions. make it messy.

is the line straight looking now? And yet we know that Rulers are straight and that the line was produced by a ruler. Just like we know light has no mass and so the path light takes is always a straight line/ray.

In the case of paper, we know the paper bent... in the case of space, well - :wink: I'll leave the statement of the obvious conclusion to you.

Of course this only works if the assumptions are true that:
Gravity Effects Mass
Gravity does not effect No mass
Light can exist in the same space as other light.
Light has no mass
Light bends near gravity (black holes prove this, along with gravitaional lensing from less massive objects like - the sun, galaxies, etc)
Light always travels in a straight line unless passing through transparent shaped objects where refraction/reflection can occur.

I think the problem is when people say things like "Gravity bends light" it does not. Mass curve's space - draw a straight line on a piece of card, now bend the card, from a two dimensional point of view the line is still straight, from a three D perspective it 'appears' curved, but it is the card that is curved, the line is still straight, a straight line. THat's how I understand it, unless I have it wrong as well. If you lived in a 2-d world on a flat sheet of paper, no matter how 'screwed up' the paper became you would always see your flat world.

It's a brainpounding concept, I like everybody else can't explain it in easy terms for you, so you have to keep at it and make a leap of faith. It's also contrary to all our senses and instincts, but if you can do mental arithmetic (that other great mental abstract) then you will get the hang of it.

Thanks for your responses, I can see that I have a lot more reading to do to get a better grasp of the concept.

For something with mass to travel the speed of light require infinite energy as the theory of relitivity goes.

Light does travel, funnily enough, at the speed of light. (aka Light travels as fast as itself)

Lightbulbs do not expend infinite energy (aka all the energy in the universe) to turn on. Thus Light does not expend infinite energy.

I see this rules out the possiblity of photons ever having mass, thanks.

Originally Posted by Zelos

its bent becuase it follows a straight line in 4D wich to us seem bending thou to gravity

the forth dimension is the first time-achse
its following 3d(or more) and gravety is nothing but a bump in 3d space.
eventhough im pretty shure gravety also effects more than our 3d's (i beleve it to be 6)

radio waves is not a lower frequency of light:
light is a wave like radio(wave), yes, eventhough they have 1 problem
light waves itself.

Light and Radio are part of the electromagnetic spectrum. They all travel at the speed of light.

The spectrum goes something like:


Longwave Radio, Shortwave Radio, HF radio, VHF radio, UHF radio, Microwaves (radar) Infrared, Red, Orange, Yellow, Green, Blue, Purple, Violet, Ultraviolet, Xray, Gamma ray.



All made out of the same thing, just with different frequency lengths.

Light can and does exist in the same space as other light, otherwise we would never see "white".

Particles with Mass can never exist in the same space as other particles with mass, or else you could walk through walls.

If you don't agree with the acertation that "Radio" and "Light" are not the same thing, then would you also apply the thought that "Red light" is not the same thing as "Green light" ?


And I'll do another thought experiment before you come at me with another question regarding this:

Put a white lightbulb up, and then cover it up in green celophane.

The light is green yes? Did it change the light?
No. why? Because the white light already was giving out green light, just that it was mixed with all the rest of the spectrum too (all the way from Infrared to ultraviolet)

the celophane acts like a filter, stopping and either absorbing or scattering the rest of the spectrum except green.

Now if you had a light which was puerly only giving off red light but you put blue celophane down, the colour of the resulting light would either be very dark purple (assuming not a 100% efficent filtering process) or actually completley dark (assuming a theoretical and technologically unfeasable 100% efficient filtering process).

Since the question wasn't asked, i'll refrain from putting the conclusion here

radio waves is not a lower frequency of light:
light is a wave like radio(wave), yes, eventhough they have 1 problem
light waves itself.

they are both light just different frequenses

embarrassingly, I must admit i havent known about the electromagnetic spectrum.
what do radio waves wave?

also light is to be thought as a particle or a wave.
some characteristics about light say its a wave some say its particle.
some say its particle and that it waves (the particle)

how do u mean? what makes radio waves radiowaves? its frequens

well since its a wave it must wave something.....

Originally Posted by miomaz

embarrassingly, I must admit i havent known about the electromagnetic spectrum.
what do radio waves wave?

The electromagnetic spectrum is radio waves. A small portion of it (less than 1 octave) forms the visible light spectrum. The range of the whole spectrum is from >0 to a theoretical frequency tied into plancks constant.
Look it up on Google, Electromagnetic spectrum, images.
I say >0 because 0 cannot be a wave. Photons are responsible, the little buggars, the higher the frequency the higher the energy. There are formula for these but probably best to leave them out for a while....

Radio waves can be 'man made' eg a radio transmitter or they can be of cosmic origin. This spectrum also includes infrared waves which manifest themselves as heat.
Approximately 80% of the sun's radiation is in the form of electromagnetic waves with the other 20% being solar particles.

Originally Posted by DarcgreY

I'm a little confused as to the nature of gravity.

I often read about how it's a force of attraction between bodies with mass. From what I understand of General Relativity though, what we percieve as gravity is the distortion of space and time near a massive body. So a body moving through the distorted space/time doesn't change its' path it's the space/time that curves.

So which is it, is gravity a force of attraction or distortion?

As usual, I have my own interpretations of science.
I wrote an article on the nature of gravity which I called ElectroMagnetic Gravity. I will hunt it down or post if it is not here somewhere.

I consider gravity to be an attraction by the nature of the proton spins acting as 'bipolar' magnets to attract only. This weak attraction would be overpowered by the electron interactions to cause this attraction to be very weak as gravity is to the coulomb forces interactions between similar and opposite charges.

With this understanding, the EM gravity would bend the light because of the influence of the magnetic nature of the gravity on light which is EM in nature. So it is not the curvature of space that causes the bending but gravity itself.
That is my opinion.

NS

Originally Posted by miomaz

embarrassingly, I must admit i havent known about the electromagnetic spectrum.
what do radio waves wave?

also light is to be thought as a particle or a wave.
some characteristics about light say its a wave some say its particle.
some say its particle and that it waves (the particle)

If you know anything about radio mechanics, you would know that radio waves are created by electrons moving 'back and forth' in the antennas that radiate these waves.
The component that transmits the intelligence is the 'magnetic' component that is oscillating as the electrons move back and forth to radiate a modified EM wave. The wave can be modified with a changing magnitude of the waves or changing the frequencies.
The current broadcast stations are on the AM (amplitude modulation) or the FM (frequency modulation) band.
The frequency modulated bands are immune to any nearby 'static' from thunderstorms or other noise generators.

NS

Originally Posted by DarcgreY

Thanks for your responses, I can see that I have a lot more reading to do to get a better grasp of the concept.

For something with mass to travel the speed of light require infinite energy as the theory of relitivity goes.

Light does travel, funnily enough, at the speed of light. (aka Light travels as fast as itself)

Lightbulbs do not expend infinite energy (aka all the energy in the universe) to turn on. Thus Light does not expend infinite energy.

I see this rules out the possiblity of photons ever having mass, thanks.

If you're really serious about doing more reading, try the book I'm reading 'The Elegant Universe' by Brian Greene. He's great at dumbing it down to easy to understand models and then building it back up. It covers all of what you're talking about here and tons more. In fact, it's the spacetime warping (which Einstein defines as gravity) that I was just reading about earlier today.

After what I read, the answer to William's initial question would be that light bends around a huge mass because the space is warped, or bent. In fact, all mass warps spacetime. However it's only really noticeable around large masses. So, gravity distorts. The curvature an object creates within spacetime is what appears to "attract" other objects when they come near it - such as in orbiting.

The book has good illustrations and it's been made into some NOVA programs. But you're not going to remember anything from a TV program - not like reading a book.

Oh, and the last chapter covered the massless photon. The fact it is massless allows it to travel light speed. Anything with even a sprinkle of mass could not travel the speed of light.