Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: yor_on on 07/10/2011 19:33:12
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If you imagine something moving, as defined relative its origin, we find that it express two kinds of inertia, as in 'refusal to stop'. One if hit from the side, another if we stop it 'head on'. We also have the objects invariant mass, that we expect to be the same in both cases. So it has to be the direction of its relative motion that creates it. That motion can be uniform or accelerated, and will in both cases vary the inertia with its relative speed.
Why?
And what is the difference between this and the idea of a 'universal absolute motion', existing?
And if you find this as proving a absolute motion, what stops you from defining a absolute rest?
And where does the energy, related to the motion situate in a uniform motion. Measurable in the object, or as a function (of its relative motion) but not measurable?
Why can't we measure it on the moving object, if so?
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All motion, or absence of motion, is relative to something else. To define absolute motion you would need to determine "absolute stopped". I don't think that's possible.
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My question is relevant to the idea of all uniform motion being inseparable from rest. It also has a relevance for the idea of what a motion really should be seen as. Macroscopically we define it as something having a duration, taking place between two defined points in SpaceTime.
The theory of relativity points out that all 'motion' (as in 'distance') is frame dependent, as well as 'time'. This one is directly related to that.
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It also have a direct influence on how QM acts, as I see it. And to be a little clearer on how I think. To me it goes back to what I see as Einsteins definitions of how to make 'experiments'. His idea of gravity as inseparable from accelerating 'constant uniform motion' for example builds on equivalences, the impossibility to differ between that acceleration and a 'gravity' in a 'black box scenario'. His way makes a lot of sense to me, and it's from there I'm wondering. There are some things I'm wondering about if they are possible, and a idea, but it's vague as for now. So all input welcome :)
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My question is relevant to the idea of all uniform motion being inseparable from rest.
Isn't that a consequence of the difficulty of defining an absolutue "rest" state? You can only say something is motionless relative to something else.
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No, that isn't the case here. If we define rest as being in a environment where we see no detectable differences in and on our experiments, in a black box scenario, then all uniform motion can be seen 'at rest', as it won't matter what speed you define yourself to have relative something else.
If you instead define it as always being still relative something else then you can't be at rest when being 'still' relative Earth, or any planet. In Einsteins definitions a 'gravity' is a acceleration, and a acceleration is a gravity. A planet is always 'accelerating' in that it has a gravity. How you want to define/explain the 'acceleration' is another matter, but it can also be seen in how 'clocks' will differ from your own.
Hmm, you can still define yourself at rest relative Earth, just as you can define yourself as being at rest relative your constantly uniformly accelerating rocket, at one G. But it's still about what 'motion' really is, and what 'at rest' really is. It's about the geometry, gravity, time, and energy to me. And there? It becomes tricky..
So being 'at rest' is slightly different from what we think, as I see it. But if you like you can ignore this and define it from your own frame of reference. And that will never be wrong, all distances you measure will be true, and your clock will never differ to you. And doing so, being 'at rest' will be where you are still relative what/where you are (on), and the only difference will be the distance you measure yourself to have made in your time measured. For example being at rest in your car, driving to work.
But this is about how I think of it :)
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There is one point more I can make, if motion exist, then 'rest' must be there too. To assume only motion is meaningless if you don't expect it to exist relative some other state. If you expect motion to exist, and we do expect it to be so, as shown in my example of 'inertia' above, then the question becomes what this 'rest' should be seen as?
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But that is what I'm trying to see, what is 'motion'?
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Let us put it another way.
If I accelerate to a higher velocity, relative some arbitrarily chosen frame of reference, then 'coast' uniformly, will my later collision free more energy that what it would do at a 'lower relative uniform velocity'?
If you think it will we have established 'motion'. And if motion is a scalar, as in speed, then there should be a scale for it. To define it as we can't say where 'null speed' is, is perfectly acceptable from the definition of speed always becoming relative something else, a 'inertial frame'. But if motion exist, so should being 'at rest'.
And the question becomes if we have something we can prove as being at rest. To find out we need to look at the phenomena we're discussing. And that is relative 'motion'. There we only find two stages, either a acceleration or a uniform motion. And a acceleration is, in Einsteins definitions, the exact equivalence of a 'gravity'. All uniform motions are as I see it also 'equivalent', and furthermore, none of them is inseparable from being at rest. To be at rest relative a accelerating frame, like a uniformly moving rocket or Earth, is experiencing a 'gravity' acting on you, so will also a non uniform acceleration be.
The point is that once we established motion, it seems very relevant to me to understand what the he* it really is :)
We live in a very 'cool universe' :) The temperatures we had at the origin has more or less disappeared, maybe the inside of a super massive black hole can recreate something similar? Probably not, but nevertheless, the universe has cooled down and we find 'distances', and it is inside the 'room' we find our 'motion'. So? Where do the 'energy' go in a uniform motion?
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If SpaceTime was a Jello able to compress and stretch. What would the space do in front of the direction of your relative motion, and what would it do aft of your direction? Think of that space as 'marked out' by photons, all keeping a equal distance between them, relative their own frame of reference, 'c'. And assume a even 'gravity' for this. What would happen to the 'markers' behind your relative motion, and what would happen to the markers in front of you.
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And it is here you need to consider it from two different 'frames of reference'.
One is 'uniform motion', the other is a acceleration. And the real question is one about 'energy' there. In a uniform motion, we have no measurable expression of any new energy inside that black box scenario. If you imagine yourself in a room with a light bulb at its 'front', in the direction of relative motion. Then the light hitting you at aft will be of the same 'energy' in all 'uniform motions', no matter their velocity.
In a acceleration you will find the light 'blue shift', as it will experience a gravitational 'acceleration' (not 'accelerate', but it simplifies it thinking of it this way) And if you change position, light bulb/ detector, the light will be seen to redshift, and so be losing energy. But, it will in both cases be a measurable change, due to your acceleration, as well as the gravity you will experience. Or constant 'inertia' if you like.
But not in a uniform motion. Where and how do the energy your motion represent get 'stored'. In 'space', that same space that compress and stretch, relative the 'markers', according to you?
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The normal definition of motion is in three (plus one) dimensions. Three of them makes the room we can measure. The last dimension is what creates the durations we need to define those first three in. We can be said to 'move' in (three) and at the same time in 'one' (time).
But motion in itself? It 'deforms' them all. Normally we define it as 'free agents' moving in a SpaceTime. But if you define it locally, motion becomes incredibly weird as it contract/stretch the space, and also all other frames durations you measure relative your your own 'clock'. And, if we stop talking about 'motion', but keep the 'deformations'?
And this is me wondering naturally :)
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And it is here it becomes very interesting how SpaceTime stores that energy, and why a uniform motion differs from a acceleration. And it is there we also find the universe to have a memory of sorts, as it will 'remember' your relative uniform motion. It 'knows' the 'energy' it represents, in a later collision. The universe seems to have a definition, although, we will find that there is no way we can differ those uniform motions from each other, when making that 'black box' experiment with the light bulb.
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Where does that 'memory'´come from, and why isn't it measurable.
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Quote yor_on
"Where and how do the energy your motion represent get 'stored'."
Presumably, this energy has to be either kinetic or relativistic depending upon speed and its really only noticeable relative to something else. How much of that energy is liberated upon a collision depends upon relative motion.
Quote yor_on
"But motion in itself? It 'deforms' them all. Normally we define it as 'free agents' moving in a SpaceTime. But if you define it locally, motion becomes incredibly weird as it contract/stretch the space, and also all other frames durations you measure relative your your own 'clock'. And, if we stop talking about 'motion', but keep the 'deformations'?"
Surely, "the deformations" are in space time and the affect is what we call gravity.
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All motion, or absence of motion, is relative to something else. To define absolute motion you would need to determine "absolute stopped". I don't think that's possible.
"Absolute stoped" does not exist,but dominant masses make kinematic slowing of time of fast objects.
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I don't know Mike, if it is 'gravity' involved there. If you think of the contraction and time dilation in form of different uniform motions you will find both and they will differ with your relative velocity, according to Einstein, and neither one being a 'optical' illusion.
But if 'gravity' is what defines and shapes a 'space', becoming its metric as it is expressed, then 'gravity' should be involved in some way. Energy seems to be some sort of thought up transformation we use for describing some origin, but there we have two descriptions. 'Work', as in useful energy able to do work, and 'work done' defining some state of energy wherefrom we can't get any more work.
And that's entropy's description but it seems quite true. I've seen some defining what is used as 'disappearing as heat', but heat is a useful energy too if you treat it right. 'Work' and 'work done' seems deeper than so to me.
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I think of gravity as a geometry myself, but, if it is there also have to be something defining its heights and troughs. And maybe that is 'energy'? I don't really know, but 'fields' are nice analogy's for the way it behaves? Does gravity interfere with itself? Does it quench and reinforce? How about something placed 'weightless' between gravitational wells, stationary relative them, and all of it moving uniformly.
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Of course, rather than thinking about the ground state as "stopped", you could start at the other end and assume the ground state is motion at light speed and try to determine what it is that prevents everything from flying around at c.
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Nice thinking Geezer, in a way that's what I'm wondering. 'c' is indeed described as being a 'uniform motion' too. To me all 'uniform motions' have a same appearance and description, in a black box scenario. Although 'c' becomes a exception, as we can't reach that state, being of 'matter'.
And then we come to 'energy'.
We all agree, I hope, that 'motion' exists :) And we all agree on that with different 'uniform motion' the 'energy' expressed in a later collision will differ.
Now, if a 'arrow of time' don't exist, all bosons at 'c' could be expected to have a indefinable 'energy', just as we describe 'virtual particles'.
It is also so that, as I understands it, even though relativity may differ in their descriptions between observers, they will all find that something that from one frame of reference act 'simultaneously', like two simultaneous lightning strikes in one frame of reference (loosely speaking here), will be found to act the same in all other frames too, even though the definition of 'when' and 'where' it happened may differ. And if the arrow of time didn't exist, then such things happening should all become freaks of nature, and no common expectation, aka 'law' of relativity. And I have some other arguments for it too.
So I think there is a real 'arrow of time', as some direction in 'four dimensions', pointing only one way. What is 'work done'.
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There is one other thing. If we define all as being energy, what would matter represent? A very 'condensed form' of energy maybe? What would 'space' represent, and 'gravity'?
So 'energy' in 'motion' inside..?
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There is one thing though, to me all uniform motion can be seen as being 'at rest'. Although they will express themselves differently in a collision. So that will be my definition of being 'at rest' in this universe, not 'motion' per se. And that may seem weird, but it's a assumption I still think of as correct.
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What is a collision? A deceleration and acceleration?
Whatever it is, it's not being 'at rest'.
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So is 'energy' related to 'distance'? Not really, in a uniform motion you can have a finite acceleration defined in the 'energy lost' as you accelerate, but after that acceleration you can continue 4-ever. On earth though, you will burn energy moving, friction/resistance wise, with gravity working either for, or against, that motion. If you use Feynman's definition of a symmetry "Anything is symmetrical if one can subject it to a certain operation and it appears exactly the same after the operation." then, when you apply a acceleration to a uniform motion to then stop after some time, becoming uniformly moving again, then all uniform motions should be a symmetry.
So, is acceleration a symmetry too? I don't think so, but I'm not sure. If we're talking about gravity then we have one definition of a acceleration that might be considered 'symmetric' possibly? If we use a uniformly constant acceleration that is, but, not when using a non uniform acceleration even though that too will leave you with a 'gravity' of sorts. I'm not sure there though. To use it this way you have to imagine that all accelerations comes from the same, leaving a exact same, 'ground state' of 'uniform motion'.
So is there a 'exact same ground state' in all 'uniform motion'?
Do you think it matters what uniform motion Earth has for a rocket leaving it? That is, assuming a higher relative uniform motion of our Earth, would it cost the rocket more fuel to leave Earths 'gravity well'?
If you think not, how/where do the universe remember what energy to express relative a collision?
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In what way do a planet constantly 'gravitationally' accelerate?
It's not doing it inside those three dimensions. Although it move it does so uniformly, constantly 'at rest', as I think of it. Does it accelerate in time then? Looked at from some other frame of reference it would seem to 'slow down' in time, relative us observing. In its own frame it does not matter what durations we define, they will always be the exact same, where and whenever we test.
But if the equivalence is a true one, there must be some description that can capture this gravitational acceleration? What about space 'expanding' then?
I've recently seen it defined as doing so 'everywhere', not only between galaxies, but also inside them. In a way that makes a lot more sense than a expansion only existing where 'gravity' is low, between the galaxies. But it also, if so, must assume that this 'space' expanding is, really, 'everywhere'. That should mean that all 'space' expands, inside our atoms too. That would give 'space' a 'direction' of sorts, a 'sphere-like' one, which then to me seems like some 'inflation' happening in every point of 'space'?
How does it do that? It doesn't make it simpler to assume it being at some weakest gravity, that one is more doubtful to me than the idea of it doing it everywhere.
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If you imagine something moving, as defined relative its origin, we find that it express two kinds of inertia, as in 'refusal to stop'. One if hit from the side, another if we stop it 'head on'. We also have the objects invariant mass, that we expect to be the same in both cases. So it has to be the direction of its relative motion that creates it. That motion can be uniform or accelerated, and will in both cases vary the inertia with its relative speed.
Why?
And what is the difference between this and the idea of a 'universal absolute motion', existing?
And if you find this as proving a absolute motion, what stops you from defining a absolute rest?
And where does the energy, related to the motion situate in a uniform motion. Measurable in the object, or as a function (of its relative motion) but not measurable?
Why can't we measure it on the moving object, if so?
Remember I said that using F = ma i.e. mass as defined by Euler is a tricky thing. Here is what I mean. A while back I wrote up a derivation of what has become known in the scientific field as Longitudinal mass and Transverse mass. In fact Einstein derived these expresent case in his 1905 paper on relativity. Here is the URL for that derivation http://home.comcast.net/~peter.m.brown/sr/long_trans_mass.htm
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Yeah, it's sort of strange isn't it?
Another thing, in the inflation we had a energy in a 'dimension less point' right? In the beginning, whatever that means :)So was this 'energy' uneven? Or was it the same all over? Is 'energy' only a definition relative a 'space' or is it something else we define it by?
(The general idea here is that depending on the 'energy density' coupled to matter the room that we call the universe either would direct inwards or outwards, changing the 'shape' of gravity/the universe. As I think of it)
I've seen arguments around how the 'energy density' could become as 'even' as we measure it in the cosmic Background radiation, and I wonder too. If I assume a sphere of 'energy' and then scale it down, is compression the answer to that?
In a compression, does the energy becomes 'evened out', even if unequal relative the distances inside it before. If we assume a time symmetry? And if those energies wasn't 'equal' inside some universe, would a compression deliver another result? Not as I can see?
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What I'm wondering is if we apply the idea of a symmetry we can imagine two sorts of (or more) universes. One like ours, another where we would find that background radiation to be very uneven. But if 'played backwards', assuming this 'point' of origin, both seems to me to start the same?
So where do I find the difference defining them, and relative what?
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A alternative view might be that we can't speak of a 'compression' for this one. But if we do you will have to define what you mean by a 'room (time)' to me. As a room is expected to be able to compress as I understands it?