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The profundity of relative motion and position

#1
Magical Realist Offline
Walk 10 feet ahead of where you are and stop. Everything in the universe in a straight line ahead of you has just been moved 10 feet closer to you. Everything in the universe in a straight line BEHIND you has just been moved 10 feet farther from you. Isn't that amazing, that by the simple act of moving your body you can change the factual state of the entire universe? There's something very deep here, something about information speeding across the universe faster than the speed of light--instantaneously in fact! That one state of one very miniscule being can change the state of the entire universe. A sort of inviolable symmetry between the microcosmic and the macrocosmic. "As above, so below."
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#2
Magical Realist Offline
(Oct 29, 2014 08:10 PM)Motor Daddy Wrote:
(Oct 28, 2014 08:05 PM)Magical Realist Wrote: Walk 10 feet ahead of where you are and stop. Everything in the universe in a straight line ahead of you has just been moved 10 feet closer to you.
So let's pretend that there is a painted grid of perfect squares on the huge parking lot that we're playing in. You are at an intersection of an x line and y line, and we put a green dot on the ground at that point to denote the start point. The grid squares are exactly 1 foot x 1 foot in size, so if you walk along an x line and come to an intersection of a y line, that is 1 foot from the start point along the x line, or the 1 foot point (checkpoint if you like). If you keep walking along the x line, the next y line intersection you come to is the 2 foot point, and so on.
So you are at the start point, and there is a ball at the 2 foot point. You walk your ten feet (8 feet past the ball at the 2 foot mark). Now you are at the 10 foot point, and the ball is still at the 2 foot point. You are 8 feet past the ball, so "everything in the universe in a straight line ahead of you has just moved 10 feet closer to you" is not very clear.
You moved 10 feet and the ball is 6 feet further away (now 8 feet instead of 2 feet at the start), in the opposite direction, then when you started!!

True enough. So to clarify, everything along the x line will have moved ten feet relative to where it was. Everything less than 10 feet ahead of you will have moved 10 - the distance it was from you. Everything less than 10 feet behind will have 10 + the distance it was from you. Everything 10 feet or more ahead of you will have moved 10 feet toward you. Everything 10 feet or more behind you will have moved 10 feet away from you. Better?
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#3
Magical Realist Offline
Quote:No. The only thing that moved was you, 10 feet. If you want to pretend the ground and x y coordinates are stationary, then what moved is you.
True enough. But my original OP stands. Everything ahead of you beyond 10 feet is 10 feet closer, and everything behind you beyond 10 feet is 10 feet farther. That's what I'm talking about: the simple a priori truth that a change of distance propagates instantaneously thruout the length of the trajectory.
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#4
Magical Realist Offline
(Oct 30, 2014 12:07 AM)Motor Daddy Wrote:
(Oct 29, 2014 09:18 PM)Magical Realist Wrote: True enough. But my original OP stands. Everything ahead of you beyond 10 feet is 10 feet closer, and everything behind you beyond 10 feet is 10 feet farther. That's what I'm talking about: the simple a priori truth that a change of distance propagates instantaneously thruout the length of the trajectory.

What about the ball? You moved ten feet and the ball is 8 feet away from you, when at the start it was 2 feet away from you. That means the ball is 6 feet further away from you than before you moved 10 feet. So everything didn't get 10 feet closer, the ball got 6 feet further away!

I already covered that in my statement. Read it again.
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#5
Magical Realist Offline
(Oct 30, 2014 01:20 AM)Motor Daddy Wrote:
(Oct 30, 2014 01:17 AM)Magical Realist Wrote: I already covered that in my statement. Read it again.
What, that you eliminated the 10 feet of space between you and the objects that moved or didn't move 10 feet closer when you moved 10 feet?? LOL
You didn't cover it. At t=0 the ball was 2 feet away. At t=29 (when you arrived at the 10 foot mark) the ball was 8 feet away, so the ball went from 2 feet away to 8 feet away, a net increase of 6 feet in 29 seconds. See what I'm getting at? You are locked in to the point. There is no escaping!! You're trapped in the numbers, and I'm right!!

Move along troll. I'm not wasting my time on you.
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#6
Yazata Offline
(Oct 28, 2014 08:05 PM)Magical Realist Wrote: Walk 10 feet ahead of where you are and stop. Everything in the universe in a straight line ahead of you has just been moved 10 feet closer to you. Everything in the universe in a straight line BEHIND you has just been moved 10 feet farther from you.

I suppose that your moving relative to everything else (assuming simply for the sake of argument that nothing else is moving) could be described as you moving (taking the rest of the universe as the reference frame) or as the rest of the universe moving (with you defining the reference frame).

In a sense they are both equivalent, I guess, from a special relativity viewpoint. But one way of looking at it sure makes the physics a lot simpler. (How would we account for a force that moves the entire universe?)

From a general relativity viewpoint, we have the accelerations to consider with their inertial forces and stuff. So the two ways of looking at it wouldn't seem to be equivalent any longer.

(This is coming from somebody who isn't remotely close to being a physicist, so take it with a grain of salt.)

Quote:Isn't that amazing, that by the simple act of moving your body you can change the factual state of the entire universe?

If one thing in the universe moves, the relation of everything else in the universe to that thing would seemingly change. So we probably need to ask, is it right to think of something's external relations as being included among its qualities or its physical state?

Quote:There's something very deep here, something about information speeding across the universe faster than the speed of light--instantaneously in fact!

How could anyone at point A know that something had just moved at point B, 500 light-years away, until 500 years later when the information about the movement arrives? (Assuming that the speed of light is the cosmic speed limit, ignoring possibilities of quantum 'entanglement' which may or may not be relevant, and so on.)
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#7
Magical Realist Offline
Quote:How could anyone at point A know that something had just moved at point B, 500 light-years away, until 500 years later when the information about the movement arrives? (Assuming that the speed of light is the cosmic speed limit, ignoring possibilities of quantum 'entanglement' which may or may not be relevant, and so on.)

It isn't necessary to have someone there due to the fact that in a sense the universe knows about it. The distance between that object and the other has changed and describes a real physical state. In this sense any object that moves changes the factual state of the universe, at least relatively speaking.
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#8
C C Offline
I suppose there is one sense in which a person walking or moving -- in this or that direction -- can alter an overarching condition across billions of light years that seems important from the standpoint of biological experience. Though in some quarters, "now" as such isn't deemed significant enough to a physics worldview to have the decency to fall consequentially out of its formulations; merely introduced as an impromptu add-on.

- - - - - - - -

BRIAN GREENE: Rudolf Carnap, the philosopher, recounts Einstein's telling him that "the experience of the now means something special for man, something essentially different from the past and the future, but this important difference does not and cannot occur within physics." [...] In my everyday routines, I delight in what I know is the individual's power, however imperceptible, to affect time's passage. In my mind's eye, I often conjure a kaleidoscopic image of time in which, with every step, I further fracture Newton's pristine and uniform conception. --The Time We Thought We Knew

BRIAN GREENE: [...] These, and all other events that I think are happening at the same moment in time but in different regions of our universe, make up what I intuitively think of as "now." You can picture them as lying on a single slice of spacetime. Let's call it a "now" slice.

Common sense would say that you and I and everyone else will agree on what's happening or what exists right now, moment after moment after moment. That is, we will all agree on what lies on a given now slice. But Einstein showed that, strangely, when you take motion into account, this common sense picture of time goes out the window.

To see what I mean, think of spacetime as a loaf of bread. Einstein realized that, just as there are different ways to cut a loaf of bread into individual slices, there are different ways to cut spacetime into individual "now" slices. That is, because motion affects the passage of time, someone who is moving will have a different conception of what's happening right now, and so they'll cut the loaf into different now slices. Their slices will be at a different angle.

DAVID KAISER: That person who's moving will, will tilt the knife, will be carving out these slices at a different angle. They won't be parallel to my slices of time.

BRIAN GREENE: To get a feel for the bizarre effect this can have, imagine an alien, here, in a galaxy 10-billion light years from Earth, and way over there, on Earth, the guy at the gas station. Now, if the two are sitting still, not moving in relation to one other, their clocks tick off time at the same rate, and so they share the same now slices, which cut straight across the loaf. But watch what happens if the alien hops on his bike and rides directly away from Earth.

Since motion slows the passage time, their clocks will no longer tick off time at the same rate. And if their clocks no longer agree, their now slices will no longer agree either.

The alien's now slice cuts across the loaf differently. It's angled towards the past. Since the alien is biking at a leisurely pace, his slice is angled to the past by only a miniscule amount. But across such a vast distance, that tiny angle results in a huge difference in time. So what the alien would find on his angled now slice—he considers as happening right now, on Earth—no longer includes our friend at the gas station, or even 40 years earlier when our friend was a baby.

Amazingly, the alien's now slice has swept back through more than 200 years of Earth history and now includes events we consider part of the distant past, like Beethoven finishing his 5th Symphony: 1804 to 1808.

DAVID KAISER: Even at a relatively slow speed we can have, actually, tremendous disagreements on our labeling of "now," what happens at the same time, if we're spread out far enough in space.

BRIAN GREENE: And if that's not strange enough, the direction you move makes a difference, too. Watch what happens when the alien turns around and bikes toward Earth. The alien's new "now slice" is angled to…toward the future, and so it includes events that won't happen on Earth for 200 years: perhaps our friend's great-great-great granddaughter teleporting from Paris to New York.

Once we know that your now can be what I consider the past, or your now can be what I consider the future, and your now is every bit as valid as my now, then we learn that the past must be real, the future must be real. They could be your now. That means past, present, future…all equally real; they all exist.

SEAN CARROLL: If you believe the laws of physics, there's just as much reality to the future and the past as there is to the present moment.

MAX TEGMARK: The past is not gone, and the future isn't non-existent. The past, the future and the present are all existing in exactly the same way.

BRIAN GREENE: Just as we think of all of space as being "out there," we should think of all of time as being "out there" too. Everything that has ever happened or will happen, it all exists, from Leonardo da Vinci laying the final brushstroke on the Mona Lisa; to the signing of the Declaration of Independence; to your first day of school; to events that, from our perspective, are yet to happen, like the first humans landing on Mars.

With this bold insight, Einstein shattered one of the most basic concepts of how we experience time. "The distinction between past, present, and future," he once said, "is only an illusion, however persistent." --THE FABRIC OF THE COSMOS: THE ILLUSION OF TIME
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