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Geek Culture / Random little thing I thought up about relativity and acceleration

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Dark Java Dude 64
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Posted: 22nd Jul 2013 08:41
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So sometimes I find it really fun to just come up with random theories about physics and the like. There are almost always significant issues with my theories, but it's still fun. Today I came up with one I found to be pretty neat however, so I thought I'd share it and see what people who know more about this stuff than I think about it.

Basically I was riding in the car today and while going around a large turn, I looked down at the ground and saw it whizzing by. I thought, well, the ground is accelerating relative to the car, but unlike the car, no force is acting upon the ground to make it accelerate relative to the car. Now keep in mind, the word relative is really important here. I noticed a significance with that realization, so after a bit more thinking I came to the conclusion that, relativity depending, objects with zero net force acting upon them may accelerate, and objects with a non zero net force acting upon them may not accelerate. Of course, Newton's equations state that this is wrong, any object with a net force acting upon it will accelerate and any object with a zero net force acting upon it will not accelerate. So then I thought, well, with the standard model of observation, Newton's equations work perfectly. Our standard model of observation however takes really no relativity into account; we consider objects not moving relative to earth to not be moving at all, even though that is far from the truth. The final conclusion I came to is that, besides the regular two force and mass factors determining acceleration, what if you could add a third relativity factor?

After doing some research on my little theory thingy, I have found a few interesting articles describing stuff that seems pretty similar to what I figured out. Those were articles about stuff like proper velocity and proper acceleration and the likes. Again I'm sure there are people here who have studied this field far more extensively than I have and I'm curious what people think of it.
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Neuro Fuzzy
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Posted: 22nd Jul 2013 09:09 Edited at: 22nd Jul 2013 09:14
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Maybe you won't find my explanation satisfactory, but here goes.

From the Newtonian point of view, relativity for rigid bodies still holds. Also, from the special relativistic view, relativity holds. However, in both of these systems there's a concept of an inertial reference frame, which is essentially: If every particle you drop in your coordinate system, with no real forces acting on it, and it moves in a straight line (or stands still - in which case we could still say its position is linear), then the frame that you're in is an inertial reference frame.

The reference frame of someone standing on earth is like the car's frame, in that it's not an inertial frame. We have the centrifugal and coriolis forces. These are real forces in most senses. If you have a particle and want to constrain its motion in your frame, you'll have to exert a force to cancel these forces. However, they aren't fundamental forces, they're only due to our frame of reference. However, they can still be called forces. Sometimes they're called fictitious forces, but the word "force" is still there.

So, one could say that, from your frame of reference, the earth accelerates underneath you: an absolutely massive force is applied to it from your reference frame. If you define F=mA and you want to use a noninertial reference frame, you are inexorably drawn to this conclusion! You can't have acceleration without a force. Of course this screws up all of our nice formulas for energy but you could probably work around this.

Therefore, from a classical perspective I'd say that there's a fundamental difference between an inertial and a noninertial frame.

Buuuuut then there's a little thing called Mach's principle which is tackled by general relativity, which completely ties my head in a knot and which I haven't studied yet. See: http://archive.org/stream/NewtonianMechanics/French-NewtonianMechanics#page/n551/mode/2up "Speculations on the Origins of Inertia". That chapter covers a lot about accelerating reference frames too, so it might be a good read, if it's not too advanced. I don't remember if there are good first principle justifications of why there should be a distinction between an accelerating and a non-accelerating reference frame. (Also note that you won't understand the text if you don't understand the equations, so try not to skip 'em ;D )

Proper velocity/acceleration are useful only if you're taking into account time dilation effects, I don't think they'd help here.

[edit]
and, I don't think we'd be talking about Newton's laws anymore, because most versions of the laws I've heard are prefixed with the clause: "In an inertial reference frame..."

[edit2]
OOh also, the paragraph on page 497 under the heading "Accelerated Frames and Inertial Forces" is useful too.


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Libervurto
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Posted: 22nd Jul 2013 15:51
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When you say, "standard model of observation", I think you mean classical mechanics.

I too like to come up with theories, it's fun and it's what real scientists do all day! Except they have the mathematics to actually test and refine these loose theories.

I'm about to post my own theory actually.
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TheComet
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Posted: 22nd Jul 2013 16:14
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Quote: "but unlike the car, no force is acting upon the ground to make it accelerate relative to the car."


Yes it is, the earth spins faster when you accelerate and restores to its original state when you're not accelerating.

Quote: "Our standard model of observation however takes really no relativity into account; we consider objects not moving relative to earth to not be moving at all, even though that is far from the truth."


That's because the influence of everything else is so minimal and insignificant most of the time, the error you calculate is significantly larger. So you may as well just drop it.

TheComet


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Kezzla
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Posted: 23rd Jul 2013 12:14 Edited at: 23rd Jul 2013 12:28
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I cant really add anything to your theory, but here is a half-baked thought I had.

I was actually wondering the other day if gravity was an illusion caused by the fact that everything in the universe is increasing in scale at the same rate,however their actual position does not change unless initiated by another object. (edited to add clarity)

probably easy to poke holes in, however I had a good time thinking about it.

I'm not a complete idiot -- Some parts are just missing.
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Libervurto
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Posted: 23rd Jul 2013 13:24 Edited at: 23rd Jul 2013 13:29
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Quote: "I was actually wondering the other day if gravity was an illusion caused by the fact that everything in the universe is increasing in scale at the same rate,however their actual position does not change unless moved physically by another object."

No no no no, everything is shrinking at the same rate, this explains the expansion of the universe.
Maybe the shrinking leaves behind divots that cause gravity. Isn't that basically Pincho's theory?

Couple that with my theory http://forum.thegamecreators.com/?m=forum_view&t=206856&b=2 and the cause of the shrinking is the continuous collisions between particles that break the universe down into ever decreasing scales.

Well I think that just about wraps up everything. You can turn off the LHC now lads.
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Kezzla
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Posted: 23rd Jul 2013 13:39
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Quote: "No no no no, everything is shrinking at the same rate, this explains the expansion of the universe.
Maybe the shrinking leaves behind divots that cause gravity. Isn't that basically Pincho's theory? "


I negate your theory by creating a hole filled with negative mass... that and you are wrong. so is everybody else.
(stands in corner not looking)

I'm not a complete idiot -- Some parts are just missing.
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Matty H
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Posted: 24th Jul 2013 12:36
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Quote: "I was actually wondering the other day if gravity was an illusion caused by the fact that everything in the universe is increasing in scale at the same rate, however their actual position does not change unless initiated by another object. (edited to add clarity)"


I thought about this too for a while, quite pleasing to see you had the same thoughts

Not sure where the theory brakes down, but it's not as silly as people may think, gravity is equivalent to acceleration, this was Einstein's insight, so what if gravity is acceleration in scale

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Libervurto
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Posted: 24th Jul 2013 13:11
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Quote: "Not sure where the theory brakes down"

It breaks down because if it were true the universe would be shrinking not expanding.
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Daniel TGC
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Posted: 24th Jul 2013 14:16
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@Dark basic dude79

My biggest issue is when you say zero force. I'm being pedantic, but when looking into an accurate physics model these persistent forces are always acting on an object.

Gravity
Small nuclear
Large nuclear
Electromagnetic

So the concept of zero force applied to any object in a real world situation can't exist as long as there is other matter around it. Heck even the smallest units of quantum appear to have forces act upon them.

The other danger point here is the concept of perception. Human perception is flawed, depending on the way you look at the world you could say one of two things.

1) I am moving faster than the ground below me.
2) I have caused the world around me to speed up, but I am staying still.

Thanks to education we all know that it's trains, cars our legs etc that move. Not the world relative to it. The world always stays at the same speed and is completely unaffected by our locomotive power.

As game programmers this is even more interesting because we can actually write programs that exhibit this behaviour, place the player in the middle of a graphical scene and then move the would around that player. Now from a 1st person or 3rd person perspective within that game world the player might think they are moving freely in space when in fact all the positioning, rotation, etc is happening to every other object in the scene other than the player.

So conceptually you could have a world that behaves like that. Of course, the problem comes about when you have multiple players zooming around the space space. You can't do that for all of them... well you could, but it would be damned confusing and it isn't something I'd like to code!

When you say things like that ground is moving relative to the car, that's an inherently false statement, from the passenger perspective within that car it's true, from the perspective of people standing outside that car it is false.
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Matty H
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Posted: 24th Jul 2013 15:35 Edited at: 24th Jul 2013 15:37
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Quote: "It breaks down because if it were true the universe would be shrinking not expanding. "


Not of the space between things also scaled up. I know it breaks somewhere pretty soon but it is interesting to think about

EDIT: I probably got the idea from my dad, he used to ask if we would know if the universe doubled in size tomorrow

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Indicium
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Posted: 24th Jul 2013 15:59
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Quote: "So the concept of zero force applied to any object in a real world situation can't exist as long as there is other matter around it"


Gravity and electromagnetism affect objects over an infinite range - although eventually it becomes insignificant - so objects will always have a tiny force acting on them.


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Libervurto
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Posted: 24th Jul 2013 16:09
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Quote: "Not if the space between things also scaled up."

Oh, I see. But if the force is completely uniform then how is gravity a by-product?
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Matty H
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Posted: 24th Jul 2013 16:10
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Quote: "Oh, I see. But if the force is completely uniform then how is gravity a by-product? "


I told you it broke down pretty quick

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easter bunny
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Posted: 25th Jul 2013 07:26
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Quote: "The world always stays at the same speed and is completely unaffected by our locomotive power."

not true and I'm sure you know it!
if you jump up, the earth moves down, but the amount is so small that it's [probably] impossible to detect

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Neuro Fuzzy
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Posted: 25th Jul 2013 08:58
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Alls I'm saying is that if F=m*x''(t) [One way to write F=m*a] and x accelerates in our coordinate system, there's a force there, even if we do make the distinction that it is a fictitious force.

I also take issue with this sentence in the OP:
Quote: "Our standard model of observation however takes really no relativity into account; we consider objects not moving relative to earth to not be moving at all, even though that is far from the truth."

The idea of relativity is that it makes no sense to talk about velocity/position without talking about a particular reference frame. So, if someone asked, "Are we moving", the answer would be yes and no.


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Daniel TGC
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Posted: 25th Jul 2013 13:27
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MissJoJo as overweight as I am even my jumps won't affect the world. It's overall mass, rate of rotation and the forces acting upon it from the depths of space mean that even I and a million of my fattest friends all jumping on pogo sticks won't affect the world's orbit, rotation or speed at all.

Such things in the system are compensated for by the above factors.

To move the world out to mars's orbit it would take 1.4 X 10^33 joules of energy.

The average 1 megaton nuclear device generates 4.18 x 10 ^15 joules of energy.

To generate the thrust required to move earth you would have to detonate a 100 megaton nuclear weapon every 10 seconds for the next billion years.

Therefore I think any uncoordinated action, that isn't religiously repeated and duplicated by many many people is going to be compensated for by the natural forces that drive out planet through space and round the sun. So our actions won't move the planet any undetectable amount because it's not enough to overcome the existing forces in place.
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TheComet
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Posted: 25th Jul 2013 16:05
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Quote: "To generate the thrust required to move earth you would have to detonate a 100 megaton nuclear weapon every 10 seconds for the next billion years."


And that only works if you direct the released force out into space so it leaves the atmosphere. Detonating bombs on earth without anything leaving the atmosphere will do bum-kiss.

I'm just going to leave this here: http://what-if.xkcd.com/26/

TheComet


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Indicium
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Posted: 25th Jul 2013 23:32
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Quote: "if you jump up, the earth moves down, but the amount is so small that it's [probably] impossible to detect"


What would you measure relative to anyway?


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TheComet
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Posted: 26th Jul 2013 01:08
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Quote: "What would you measure relative to anyway? "


The sun


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Dark Java Dude 64
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Posted: 26th Jul 2013 04:19
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Wow, didn't know I'd be venturing into such a complex field when I posted this, though I should have guessed!

All of this frame of reference stuff is an interesting study for sure, I'll have to look into it in more detail.
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easter bunny
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Posted: 26th Jul 2013 06:02
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Quote: "MissJoJo as overweight as I am even my jumps won't affect the world. It's overall mass, rate of rotation and the forces acting upon it from the depths of space mean that even I and a million of my fattest friends all jumping on pogo sticks won't affect the world's orbit, rotation or speed at all."


According to Newton, "Every action has an equal and opposite reaction", which means that to jump up, will push the earth down.

Quote: "To move the world out to mars's orbit it would take 1.4 X 10^33 joules of energy.

The average 1 megaton nuclear device generates 4.18 x 10 ^15 joules of energy.

To generate the thrust required to move earth you would have to detonate a 100 megaton nuclear weapon every 10 seconds for the next billion years."


If, to move the earth xxxxxx Kilometer's takes xxxxxx Joules of energy, it follows that xx Joules of energy will move the earth xx Km's, right?
The keyword in Newton's law is equal, if you weigh 1/1000000000000th of the weight of the earth (random amount). Then if you jump 1 meter, the earth will move 1/1000000000000th of a meter, an undetectable amount.

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Dark Java Dude 64
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Posted: 26th Jul 2013 06:08
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So saying those things won't affect the velocital status of the Earth at all is equivalent to saying it will affect the Earth by zero amount; zilch, nada. But wouldn't the velocity be changed, just by a ridiculously small and negligible amount, although still changed indeed? Granted when you jump, the force you put into the Earth when you land will offset what you did by pulling on it making the net change zero, but between the time you were resting and the time you were at the apex of your jump, the velocity would have indeed been different.
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easter bunny
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Posted: 26th Jul 2013 07:20 Edited at: 26th Jul 2013 07:21
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that /\

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Indicium
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Posted: 26th Jul 2013 17:43
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Does your own gravity not pull Earth back the same amount your jump pushed it away?


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Daniel TGC
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Posted: 26th Jul 2013 22:29 Edited at: 26th Jul 2013 22:35
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Quote: "According to Newton, "Every action has an equal and opposite reaction", which means that to jump up, will push the earth down."


I think that's a very simplistic view, not strictly speaking wrong but it doesn't take into account other factors.

Note: These statements assume you mean Earth as in the planet rather than earth as in soil, ground, dirt etc.

1) The mass of earth compared to a single human being is massively overwhelming.
2) The planet earth is not a perfect conductor, or a single material. It's made up of many substances, some of which transmit kinetic energy better than others.

For example, if you jump up and down on a trampoline then the impact energy is absorbed, stored and even returned with a loss.

The same is true for lose soil, if you jump up and down on loosely pacted earth then it will absorb a great deal if the energy, rather than pass it on.

After all if no energy was ever lost from impacts, and transmitted perfectly all the time then as I hammer on one side of planet earth some one would have to send me a very long distance letter asking me to keep it down they are trying to sleep.

3) The earth has rotational spin, which is a massive kinetic force. Gravity has been holding planets and bay for billions of years, given there mass that's pretty darn impressive even if it is supposed to be the weakest of the four forces (after all a small magnet can overcome gravity very easily).

Therefore you might be able to "push" the immediate soil under your feet down, or perhaps send some vibrations through a building. But you're no more pushing the planet "down" than I am when I jump. Not as a whole anyway.

Quote: "If, to move the earth xxxxxx Kilometer's takes xxxxxx Joules of energy, it follows that xx Joules of energy will move the earth xx Km's, right?
The keyword in Newton's law is equal, if you weigh 1/1000000000000th of the weight of the earth (random amount). Then if you jump 1 meter, the earth will move 1/1000000000000th of a meter, an undetectable amount."


Nope, because I was quoting extreme numbers to overcome extreme forces. Once you overcome all forces with enough kinetic energy, then you can generate some kind of unnatural movement.

Think of me, I used to be a rugby player in school. I'm large, heavy set and I know how to push. (or at least I did in school). Now imagine that it's not only me you are facing but I have a big pile of sandbags in front of me as well, all pressing against a metal sheet. I'm exherting all my power constantly on one side, the metal sheet and sandbags are perfectly absorbing my force.

No matter how many times you run at me with equal strength, or even slightly more strength you can not hope to overcome the two types of material (one is absorbent, the other is rigid) in addition to my own power. This is because to do so you'd have to overcome the properties of all these objects. Their friction, the loss of kinetic energy through the substances and the fact that I'm acting upon them with equal power.

This is more or less what's going on all the time, you'd have to overcome the mass, momentum, and forces acting upon the earth in order to move it down. The most you can do is spread a bit of dirt around and maybe send a very small vibration through the ground for a few miles before it's completely cancelled out.

Quote: "Does your own gravity not pull Earth back the same amount your jump pushed it away?"


No, because if that happened you would have to be extremely dense. You would have to have the same amount of mass as the world. But if that was to happen then earth would "fall in around you" and you'd become more or less the centre of the planet depending on how dense your concentration of matter would be.

Theoretical black holes are a good example, remember the idea is that these are the reminiscence of a collapsed star. Some people may say it has infinite gravity, but that's not true. It has an equivalent amount of gravity for the mass that the star had, but that mass has been super concentrated so you're effectively getting all of that stars energy in a fraction of the size.

In theory earth could orbit a black hole, providing it was compressed down to 4.4mm and orbited with a period of 3cm ( 30mm ). Effectively that would be a very small black hole orbiting a larger one.
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Indicium
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Posted: 27th Jul 2013 00:28
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Quote: "No, because if that happened you would have to be extremely dense. You would have to have the same amount of mass as the world. But if that was to happen then earth would "fall in around you" and you'd become more or less the centre of the planet depending on how dense your concentration of matter would be."


I don't mean you pull the Earth the entire way toward you, I mean would your gravity pull the Earth back by that tiny tiny insignificant amount you pushed the Earth away by when you jumped?


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easter bunny
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Posted: 27th Jul 2013 02:16
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Quote: "No, because if that happened you would have to be extremely dense. You would have to have the same amount of mass as the world"

well, the moon has less mass than the earth, but it still affects the earth's movement.

but I see your point

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Daniel TGC
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Posted: 27th Jul 2013 02:44
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Quote: "I don't mean you pull the Earth the entire way toward you, I mean would your gravity pull the Earth back by that tiny tiny insignificant amount you pushed the Earth away by when you jumped?"


I wouldn't have thought you jumping or moving away from the earth surface would make any difference, there's so much mass to overcome. But gravity isn't something we can measure very well.

What we can do, is take a metal rod put it in a vacuum tube and measure how fast it falls. This is a good indication of the strength of gravity.

The problem with this is that earth's gravity is so much stronger than yours that you make no difference to it. I suppose what you could do is take a measurement while you are far away from the device, and then take a measurement when you're sitting on top of the device. If the rod falls down any slower than that's reasonable evidence that you're gravity field is having an effect.

But at the same time you can't simply make that assumption, because if for example it's an iron rod then you might actually be slowing it down due to a very small electromagnetic field. So you'd have to repeat this experiment with something non-magnetic.

Even if you do that, then the simple act of your sitting on the machine could produce vibrations that interfere with the results.

I can go on and on, eliminating possible interference and still not not explore all the possibilities.

Realistically, until we detect "The graviton" a particle theoretically connected to gravity and find a way of understand it directly ( rather than crudely dropping stuff and timing how fast it falls ) then your theory is as good as anyone's.

But realistically, I don't think you exert enough gravitational pull to make a difference if at all. After all, when you think of everything on earth, all those different materials and objects. It's all realistically part of a single closed system. We are born, live and return to the earth. Short of blasting ourselves in space I'm inclined to treat anything on earth no matter how it's moving or behaving as part of the earth's gravity well.
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Neuro Fuzzy
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Posted: 27th Jul 2013 13:28
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Quote: "Every action has an equal and opposite reaction"

Just to screw with everyone, this is not true. For example:
"If two charges are moving uniformly with parallel velocity vectors that are not perpendicular to the line joining the charges, then the mutual forces are equal and opposite but do not lie along the vector between the charges. Consider, further, two charges moving (instantaneously) so as to 'cross the T,' i.e., one charge moving directly at the other, which in turn is moving at right angles to the first. Then the second charge exerts a nonvanishing force on the first, without experiencing any reaction force at all."
[correct time for "freacking magnets how do they work". Uuuh not sure about the second one, I did an analysis on this once but... I swear there was at least an electrostatic force on the 2nd one.]


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Daniel TGC
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Posted: 27th Jul 2013 14:33
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That phrase comes from Newtons laws of motion, which form the foundation for classical mechanics. It's designed to provide laws between objects and the forces acting upon them. A quick summary of these laws are.

1) When considered within the inertial reference framework an object is either at rest or moves at a constant velocity unless it is acted upon by a force.

For example, if you put a stone in a zero gravity environment and leave it there, it won't slow down or speed up for no reason. You must apply a force to it before it will rotate, move position, accelerate, decelerate, etc.

2) In order to accelerate any body of mass the force acting upon it is inversely proportional it's mass. The formula for this is F = ma (F is the force, m is mass and a is the acceleration of that mass).

This is used, for example to calculate how much force is required to achieve a certain acceleration against a given mass.

3) When one of two masses exerts a force upon the second mass, the second mass exerts a force of equal magnitude and opposite direction to the first.

This is where the statement "Every object has an equal and opposite reaction". It's effectively a reduction of newtons third law.

I say all this because it doesn't apply to particle physics or the conduction of charges through an object, at that level you're down down into the atomic scale where the entire ruleset changes. Classical mechanics deals with the macro world, two marbles hitting each other, an astronaut in space, how planets orbit each other.

Quantum physics deals with the reductionist scale, that is atoms, particles, quarks etc.

The biggest problem with both of these disciplines is that they do not agree. When you scale up quantum physics and try to apply it to classical mechanics then they don't agree at many key parts. This is the reason we're searching so hard for a unified theory. Something that can encapsulate both the quantum and macro world.
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Posted: 28th Jul 2013 02:15
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It's not a quantum effect, and it arises from relativity + coulomb's electrostatic "F=K q1 q2/r^2" law. In fact, ignoring general relativistic effects, the same things can be applied to gravity. It is called classical, but is derived through special relativity.


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Daniel TGC
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Posted: 28th Jul 2013 02:52 Edited at: 28th Jul 2013 02:57
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Very little can be applied directly to gravity at this point because we don't know what the heck it is. What we can do is observe heavenly bodies in the sky and work equations around them describing their movement. This mathematics isn't perfect however, and we've had to introduce mathematical tricks to explain why it simply doesn't work. Black holes and dark matter are examples of this. Because we can't see dark matter for example, and because the mathematics don't quite work, we adjust the figures to account for the missing matter.

Now, whether or not that matter is actually there is completely unobserved. As, indeed are black holes which serve a similar purpose in terms of mathematics.

This leaves us with two possibilities, first either these missing elements exist and they have been discovered by mathematics. Second, the mathematics is wrong.

Classical mechanics consists of the work done in the areas of chemistry and physics prior to the 20th century. This includes the organization of the periodic table, thermodynamics, the wave theory of light, and Newtonian mechanics and a few other bits and bobs.

What is quantum mechanics and what does it do?
In very general terms, the basic problem that both classical mechanics and quantum mechanics seek to address can be stated very simply:
Quote: "If the state of a dynamic system is known initially and something is done to it, how will the state of the system change with time in response?"

Newtonian mechanics goes about solving the problem for systems in the macroscopic world and, then quantum mechanics does it for systems on the atomic and subatomic scale.

These two systems of analysis work within different domains, while there may be some overlap in some area's, quantum mechanics is the newer system when dealing with subatomics, and has yielded more practical applications than classical mechanics has espically in electronics.

However quantum mechanics doesn't attempt to deal with anything on a macroscopic scale because the rules at this point appear to change. Why? No one is sure, and this is why we're working towards a unified theory.

Source: Cambridge University Press 0521829526 - Fundamentals of Quantum Mechanics: For Solid State Electronics and Optics, by C. L. Tang
Source: Classical vs. Quantum Mechanics UCDavis
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Neuro Fuzzy
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Posted: 28th Jul 2013 03:04
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I don't understand your point and you don't leave me with confidence that you really know what you're talking about...


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Daniel TGC
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Posted: 28th Jul 2013 04:56 Edited at: 28th Jul 2013 05:00
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Which bit didn't you understand? As far as I was aware we were discussing the small matter of moving a whole planet very very slightly just by jumping up and down on it.

Then you started talking about the transmission of charges (I presume electrical charges as you started talking about electrostatic).

The passing of a charge between particles, isn't the same thing as colliding two sets of matter together.

Then you started talking about newtons 3rd law, which again doesn't apply to charges. It's classical mechanics. That started the classical vs quantum discussion.
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Neuro Fuzzy
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Posted: 28th Jul 2013 05:24
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Quote: "Then you started talking about newtons 3rd law, which again doesn't apply to charges."

It can apply to charges, in the same way that it applies to other forces, no quantum effects are needed. It's just a very confusing thing implied by (special) relativity, equivalents of which occur with any "action at a distance" force. It's completely classical, in the modern sense of the word. It's not classical mechanics, but that doesn't make it not classical! (Generally I've heard classical refer to anything non-quantum. If we take this to be the definition)


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Daniel TGC
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Posted: 28th Jul 2013 13:38
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The collision of two sets of established matter comes under the heading of the 3rd law. Charges do not.

An electrical charge is the physical property of matter that causes it to experience a force when in close proximity to other sets of charged matter. Negatively charged matter is repelled by other negatively charged matter but strongly attracted to positively charged matter.

This leaves the realm of gravity as you originally suggested and places it firmly in the realm of electromagnetic a completely different attractive and repulsive force.

Now if you were to discuss free flying electrons in open space colliding with one another, this comes under the third law most certainly. But electrical charges do not.
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Diggsey
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Posted: 28th Jul 2013 16:37
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Quote: "Basically I was riding in the car today and while going around a large turn, I looked down at the ground and saw it whizzing by. I thought, well, the ground is accelerating relative to the car, but unlike the car, no force is acting upon the ground to make it accelerate relative to the car."


Forces always come in pairs: if the ground is applying a force to the car then the car is also applying a force to the ground.

[b]
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Neuro Fuzzy
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Posted: 29th Jul 2013 04:27
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Quote: "This leaves the realm of gravity as you originally suggested"

I'm telling you that, whether you have a repulsive spring force like F=kx, a gravitational force like F=GmM/r^2, or an electrostatic force like F=kqQ/r^2, with action at a distance forces, if you don't want to violate causality, you need to violate the "equal and opposite" vector law. It's not that, "oh, magnets are just weird", it's a general property of all forces!


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Daniel TGC
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Posted: 29th Jul 2013 04:51
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lol, yeah ok.
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Neuro Fuzzy
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Posted: 29th Jul 2013 05:00 Edited at: 29th Jul 2013 05:02
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b-but... it's true and neat!
[edit]
and is relevant because it throws a wrench into things when talking about Newton's laws


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