Gravitational Energy

[smooth]

With the greatest of respect

 

I would like to ask Klaynos to stop replying to my posts in this thread, for I am unable to work with his/your methods of explanation.

 

 

 

OK, 5614 I have understood most of what you have said, but I do not believe you have grasped what I am trying to explain - if I may proceed with your explanation of light falling down into the dent…

 

The first scenario depicted within the link you included (with the orange and white lines), shows light not falling into a dent (as would be expected in the rubber sheet scenario), rather light been initially ‘pushed away’ and then falling into a dent upon the other side of the ’massive object’. So why do you continue to confuse by giving an analysis of the rubber sheet analogy?

 

[swansont]

With the greatest of respect

 

I would like to ask Klaynos to stop replying to my posts in this thread, for I am unable to work with his/your methods of explanation.

 

 

That's not how it works. You are free to skip over any response you do not wish to read, under circumstances such as this (i.e. as long as you are not ignoring questions put to you or ignoring moderator comments).

[5614]

OK, 5614 I have understood most of what you have said, but I do not believe you have grasped what I am trying to explain - if I may proceed with your explanation of light falling down into the dent…

Remember that in the rubber sheet analogy a dent is where another object will fall into (or curve around, depending on speeds and masses etc.), this is because in the rubber sheet analogy there is some gravitiation source beneath the sheet, so whenever there is a dent things will fall in to it. In real life there isn't this gravity source "beneath" the real thing, instead the curvature itself represents a force. The rubber sheet analogy is good for getting a picture, but the method via which it works is different from real life. Rubber sheet has a gravity source beneath it, so when there's a dent things fall in to it. Whereas in real life the dent, which is in space-time, which isn't as such a physical thing (you can't pick it up), represents a force.

 

The first scenario depicted within the link you included (with the orange and white lines), shows light not falling into a dent (as would be expected in the rubber sheet scenario), rather light been initially ‘pushed away’ and then falling into a dent upon the other side of the ’massive object’. So why do you continue to confuse by giving an analysis of the rubber sheet analogy?

We are talking about this picture:

 

 

In this picture, if you wish to stick with the rubber sheet analogy, the rubber sheet would be beneath the Earth and the sun, and there would be a dent at each mass. The dented zone is where the blue field around the sun is, or at least that is where the field is strongest, in theory gravity doesn't become 0 until you are an infinite distance from the source, but it does get quite weak quite quickly (it loses strength at 1/distance²).

 

Initially the light (the white line) is angled such that it will go past the sun. This is not the light being pushed away, it is merely the initial direction of the light. Light going straight in to the sun will go straight in to the sun. Light going off at 90 degrees to the sun will never be seen by us. But light that is angled to brush past the sun (as the white line initially is) will be seen due to gravitational lensing. If the sun weren't there then the white line would be straight, at the angle it is at the beginning of the arrow, so it would go past the Earth.

 

So the white line is initially going to brush past the sun (if it continued in a straight line). However after a short while it hits the blue zone around the sun, the sun's dent in space-time, where the light feels a force due to the sun's gravitational field. This causes the light to curve around the sun, just like a ball bearing would around a dent in a rubber sheet, and just like commets and asteroids do when passing by the sun.

 

The light then "escapes" the sun's field (or at least the really strong part, which is the blue bit), and proceeds to travel in a straight line towards the Earth. When we see this white arrow arriving, it would look as if the white arrows came from where the orange arrows came, because our eyes can't account for how the photon has been curved by gravity.

 

I hope this explains the picture, and in turn helps answer the original question.

[smooth]

As far as I am concerned you have not given me an adequate explanation of how light is able to enter into a segment of bent space-time, and without accelerating (as a body obeying Kepler's law of planetery motion would have to do to prevent itself from spiralling inward) leave that inward spiral and find its way to earth.

 

I have continued to give as clearer reason as I can, as to why I cannot percieve this happening, and I am getting very thrustrated now.

 

[insane_alien]

light cannot change speeds, there is only one possible speed it can be moving at. this is because it is massless, to move at any other speed would be impossible. objects with mass can move at nearly any speed they want wthin the limits of c.

[swansont]

If you look at the path a plane travels between two distant points, taking the shortest path (as light would) and then project that onto a 2-D map, you'll notice that the path is no longer a straight line — it's a curved line. Something similar is going on here. We thing the path of the light is straight, because we assume the spacetime is "flat" but it really isn't.

 

When you look at something a tub of water, its position appears shifted because of refraction. General relativity is similar to that, except the bending is modeled as/explained by geometry rather than a change in the speed.

 

So if you look at assuming that spacetime is flat, i.e. Cartesian coordinates work, the light does accelerate — it just doesn't change speed. But like the globe/map example, it's because we are assuming one geometry when the actual geometry is different.

 

As far as I am concerned you have not given me an adequate explanation of how light is able to enter into a segment of bent space-time, and without accelerating (as a body obeying Kepler's law of planetery motion would have to do to prevent itself from spiralling inward) leave that inward spiral and find its way to earth.

 

 

 

It's because the warping is very gentle, so the deflection is small. Large warping, to the point where the light cannot leave, is a black hole.

[5614]

Just to add a picture to Swansont's post:

 

 

a plane will take the shortest distance between two points, because it wants to save fuel (so it's cheaper). To do this it will follow one of the lines shown in the above image. However this "line" is actually a curve, and you might think that therefore this is not the shortest distance, but that is because we're modelling the spherical and 3D Earth on to a 2D surface. In the real world it is the shortest path, but when you project that on to a different set of axes the transformation distorts it (basically we're projecting the real world, a 3D non-Euclidian system, on to a 2D Euclidian one, so this projection cannot be interpreted literally, not without first undoing (or taking in to account) the effects that the transformation has).

 

Is it any clearer now?

[YT2095]

simply put, think of Water passing through a hose pipe, it`s moving in the same direction, taking the shortest path even at a constant velocity if you want it to.

 

now curve the hose around.

 

the water doesn`t "Know" it`s curved around, as far as it "Knows" it`s still traveling in a straight line.

 

well Space is the hose, and the water is the Light.

[Kygron]

As far as I am concerned you have not given me an adequate explanation of how light is able to enter into a segment of bent space-time, and without accelerating (as a body obeying Kepler's law of planetery motion would have to do to prevent itself from spiralling inward) leave that inward spiral and find its way to earth.

 

At least with this post I understand what you're trying to ask for. Let me simplify this tremendously. Assume a black hole and an asteroid, the BH is fixed in position and the rest of the universe is empty.

 

You're asking how the asteroid can enter the BH's influence and then leave again. The answer is that it never does! Gravity has no range, so the entire universe is under the influence of that black hole. Anywhere the asteroid is it will be obeying Kepler's laws. If it gets to earth, that will be because earth is on the orbit, not because it escaped from the orbit.

 

Back to light, as swansont said light CAN accelerate, as long as it's not in the direction of motion. Light only has a fixed SPEED, not VELOCITY. I don't think Kepler's laws would apply to light, for this vary reason, so a simple "orbit" would appear far more like a parabola or hyperbola then an ellipse.

 

Is that what you were trying to ask, or am I still misunderstanding you?

[5614]

Gravity has no range

Gravity has an infinite range, I think this is what you mean, but I don't like your wording .

 

Back to light, as swansont said light CAN accelerate, as long as it's not in the direction of motion.

Err, wrong way around . Light can accelerate as long as it is the direction (and not the speed).

 

FYI light could orbit an object, if the object were big enough and light started off in the right direction.

 

And whilst a gravitational field does strech to infinity, it is possible to "escape" it. If you have more kinetic energy than the graviational energy it would take to move from the planet to infinity, then you would "escape" the field. This velocity is known as the escape velocity.

[smooth]

Allow me to illuminate you to some of the confusion you place upon me.

 

As you have tried to instil in me- Light travels in a straight line, it does not bend, rather the space-time it enters into bends. However to explain my query as to how light can enter into a downward spiral (of space-time) and still escape without been able to increase in speed, you have offered me the explanation that it (light) can change its velocity. However this statement contradicts your earlier statement (ie light travels in a straight line), as this implies that its velocity never changes (rather the velocity of space-time changes), hence my statement - light is unable to accelerate - which you dismissed.

 

With this in mind - How can space-time change its velocity, allowing light that has been bent inward by it, to escape?

 

 

Thank you all for your efforts

 

[Klaynos]

The light doesn't spiral downwards, it mearly curves.

[5614]

I can understand why you're confused, and I'm not doing an amazing job of explaining, but I'll keep trying:

 

In a cartesian (or Euclidian) system the light will look like it bends. Look like it does, nothing more. This is because using a cartesian system for space-time is a bad model, because space-time is very much non-Euclidian. In the correct or real-world non-Euclidian system, light does only travel in straight lines (where "straight" is defined within the non-Euclidian system).

 

Light has the appearance of bending in a Euclidian system, but only because the Euclidian system doesn't represent the bare truth, as it were. In the real-world the system itself is bent by gravity (hence it is non-Euclidian) and light follows this curvature, but remember that this curvature only exists if you're using a Euclidian system, in the real non-Euclidian system you don't have a bend, as it were, because the bend defines the system, the bend is the shortest distance between two points.

 

The human brain thinks in terms of Euclidian systems, we can't really mentally process a non-Euclidian system, I think it is this that you are struggling with.

[swansont]

Back to light, as swansont said light CAN accelerate, as long as it's not in the direction of motion.

 

Err, wrong way around . Light can accelerate as long as it is the direction (and not the speed).

 

Actually, I think both cases are true (though I believe you misread the statement) if you don't account for the curvature, i.e. you make a measurement in a region that is not in your locally flat region, and assume the whole region is flat. You won't get c for the speed. That's one interpretation of the Shapiro delay, AFAIK. Of course, if you do account for the curvature, you get a different path length, and get c, or you go into the locally flat frames of the path of the photon, and take the gravitational time dilation into account.

 

Here's a page with some more animated diagrams that might help:

http://www.astro.ucla.edu/~wright/deflection-delay.html

 

and more here

http://www.astronomynotes.com/relativity/s3.htm

[5614]

Actually, I think both cases are true (though I believe you misread the statement) if you don't account for the curvature, i.e. you make a measurement in a region that is not in your locally flat region, and assume the whole region is flat. You won't get c for the speed. That's one interpretation of the Shapiro delay, AFAIK. Of course, if you do account for the curvature, you get a different path length, and get c, or you go into the locally flat frames of the path of the photon, and take the gravitational time dilation into account.

Ah yes, true, they're mathematically identical, and each method is equally valid. Interesting!

[smooth]

Time for celebration! Yippee! I’ve got it!

 

Well sort of, I’ve got an understanding of it in my language, but before I share it with you may I please ask you to show some patience if you already know where it will fall down in the future, if that is indeed the case… as I am allowed some time to enjoy the view from this particular peak!

 

 

Firstly, for this exercise I am viewing the light that is in perpetual standstill just inside the event horizon of the black hole, as irrelevant on the grounds that energy is always been added to it, and hence that light is spiralling inward even if that process takes an incredibly long time. For simplicities sake I am also going to ignore light that may encircle the black hole, possibly many times, before been freed there from.

 

To understand I am going to create a boundary, which funnily enough happens to also be the event horizon of a black hole. However what is new about how I view this boundary in order to comprehend a ‘geometrical’ picture of how light can be bent by space-time while still having the ability to escape to an outside observer is this…

 

I am going to give the boundary a kind of solidness, comparable to say a smooth and evenly distributed crust upon the earth, remember that inside this crust all light must at least orbit the black hole once before breaking free from the curvature. If there was an atmosphere upon this boundary, and the angular momentum/spinning of the crust brushed against this atmosphere, causing friction that led to it been warped (admittedly only in one direction), I solve my spiralling inward problem.

 

The difference here is that before my spiralling inward was like a taught string of gravity (similar to that seen in the spiral arm galaxies), by creating this atmosphere scenario there is still space-time curvature, but now there is no tension in the ‘gravity string’ for it is not attached as it were, and hence I get curvature while still allowing the light to escape.

 

________________________________________________________________

 

 

Klaynos

 

I hope you might now start to realise why I said what I did previously, for I doubt you envisaged that I was trying to understand it in this manner, for as you can see, I do not currently comprehend it in the formal manner. And will you not allow me some time to see where this thought process leads? For you never know what might crop up before I abandon it if I need to.

 

No hard feelings?

 

 

Thanks for the links swansont, I have wrote the above before reading/studying them, so it might need altering, as I am sure it will in the future anyway.