tar

Iggy,

Sorry for the long delay in response. Irene left us without power for 48hrs. and we just got internet back this afternoon.

I had difficulties with the red line, because the trail end of it followed the moving planet. The trail end of it should have stayed at the starting point. But you tell me it was to show the distance between the moving planet and the photon. This is fine, except how does the scientist on the moving planet determine how far away from the ship the photon has gotten? We need the third "god's eye view" to make this determination. The moving planet's scientist cannot "see" the photon get to the other planet.

I return to my simutaneity question. If the moving scientist knows the distance at the start is 1 light year, the photon will get there in a year and the moving planet,(I forget its speed, say .9C) will get there in 1.11... years.

Whose perspective, or whose "now" is violated by this reality?

Is the objective reality that relativity describes based on the now of the moving planet, the now of the stationary planet, or the now of a "God's eye" view that can see all events happening at once?

Regards, TAR2

Iggy,

In you diagram with the green planet and the blue planet the red line, at least the lead arrow represents only the position of the lead photon, which was emitted when the blue planet was at its starting point. At every point of its motion a new red arrow should go out to the green planet.

According to my conception a photon emitted from the blue planet will travel the same speed and distance as there is between the blue and green planet, regardless of whether the blue planet is following it fast, standing still or going the other way.

The second photon emitted by the blue planet would do the same. It would have a slightly smaller distance to travel, and would hence make the trip in a slightly smaller amount of time, but would still cover 186,000 miles per second.

If a yellow planet at the midpoint, sent a signal to the green planet, when it saw the blue planet start moving toward the green, the signal would reach the green planet at the same moment the red arrow reaches it.

If the yellow planet at the midpoint, sent a signal to the green planet, when it saw the blue planet pass by, the green planet would recieve the signal, at the same moment that it recieved the photons put out by the blue planet as it passed the midpoint.

The "difference" between the signal from the yellow planet, and the signal from the blue planet, as seen by the green planet would be the "frequency" of the signal. If the same signal was sent by both the yellow planet and the blue planet, as the blue planet passed the yellow, the green planet would see the blue planet's signal "blueshifted", in comparison to the yellow's signal.

Perhaps this conception requires an "ether" which Michelson/Morley did not find. But I don't think it does. What it requires only is an objective "medium" built by the magnetic and electric fields of the photon, which are subject to the characteristics of the electric and magnetic fields which the photon finds itself among.

Subjective experience of any given signal requires that the signal was generated at a distant point at a past time.

Only an objective gathering of the evidence, can however determine this.

If one is to imagine an objective universe, it should be one that fits together, and exists in its entirety, irregardless of which parts of it are experienced here and now. In fact, most of it is "unreachable", being that it is happening "now" and is too far away for us to sense in our lifetimes or even in a million years.

Does relativity describe the reality that exists "now", that we will never experience? Or does it describe the reality that we experience?

Regards, TAR2

Schrödinger's hat,

There are several issues I have with "understanding" what you are talking about.

I have been told to dispose of certain notions I have of reality, which do not agree with the math that describes reality "better" than my notions of it.

I am somewhat bewildered by this. I am not certain how one is supposed to imagine anything without making an analogy to something "already" understood.

If we are "aware" of reality, it is because we know what space is, and our position in it, and we know what time is, and our position in it.

If we are to assume (assumption number 1) that the speed of light is a constant thing, when measured from an inertial reference frame, then we have to PREsume that there is a constant thing that measures space and a constant thing that measures time.

How can you have a constant of 186 thousand miles per second, if you are not prepared to hold either miles constant or seconds constant? The whole idea of constancy loses its meaning. All the SI units are interrelated. Each defined in reference to the others. If meters are shorter than meters and seconds are longer than seconds to make C an integer, namely 1, in your formula, then you just changed the meaning of every other scientific unit in the book. How the laws of physics can hold under these circumstances appears more like a shell game, than a description of reality that I should yield to, instead of holding on to a sensible notion.

I never did understand the difference between a "real" force and a "ficticous" one. If it throws me off the merri-go-round, it is sufficiently real for my consumption.

There are "ways" that we sense, remember and predict reality. We have analogies we draw, maps we make, things we discover and share, names we give to stuff we collectively experience. We are not gods, we cannot see Alpha Centuri and our hand pointing at it, at "the same time" except in the manner that it actually happens. Our existence at a particular place and time, allows us to put everything else in perspective, and measure the "distance" things are from us. But that assumes the speed of light is a constant 186,000 miles per second. And a mile stays a mile, and a second stays a second. Otherwise, what exactly is it that you are holding constant?

Regards, TAR2

Owl,

I don't wish to interfere with your discussions. I thought I might be augmenting.

Perhaps not, but I am enjoying this thread none-the-less.

I am still hung up on time being the same type of thing as space as Schrödinger's hat points out in 177.

I lean in your direction on this Owl, and think it something else that exists along with, or because of, or as a result of 3-D space.

What seems to be always swept under the rug, is the fact that this moment is different than the one that just past, and the one that is about to happen. It is this difference that is time.

A stationary room, say Point A, will feel the effects of it, even if it doesn't move at all. All the physical processes going on inside the room will continue to happen. Things will grow and die, be built and fall apart, within the room, given the interplay between the components of the room.

Even the vacuum of space inside a void between strings of galaxies will have the rest of the universe "going on" around it, and the photons of an immense number of "events" passing through any given volume, "all the time", or "at any given time."

One of the things I have "figured out" in the last couple years, is that space, in its enormity, "loses" important characteristics, if thought of, all together, "at one time". It simply does not exist this way...ever.

That "now" where Alpha Centuri exists and we will "see" it in 4.5 years CANNOT be seen together with "this" now, except at a midway point in 2.25 years. And there is no actual way to coordinate the experiences together as "one thing".

And the "event" that is occurring "now" on Alpha Centuri, does not actually "end". It continues through the midpoint in 2.25 years, through the Solar System in 4.5 years, and right on past to the environs behind us (as we face Alpha Centuri).

Every event, everywhere has this "ripple" effect through the rest of the universe, and every point in the universe is continually buffeted by the continual ripples sent out from every other point in the universe.

In an important sense there IS only one perceiver, because if not at the particular place "here", and the particular time "now", there is no place or time to be.

Regards, TAR2

'Cept all those "other" places and times we can consider in reference to "this one."

Objective idealism is an idealistic metaphysics that postulates that there is in an important sense only one perceiver, and that this perceiver is one with that which is perceived. One important advocate of such a metaphysics, Josiah Royce, wrote that he was indifferent "whether anybody calls all this Theism or Pantheism".

Owl,

You say that "one perceiver" is clearly theistic, but I don't think it has to be taken that way. It is you that are the perceiver, or me, or whoever, but this one perceiver, who perceives the world at a particular time, and at a particular place, is not "other than" the world which he/she/it perceives. "The perceiver is one with that which is perceived."

I don't think this requires an Anthropomorphic being, to be true. I think it simply is true.

There is no place or time, other than reality from which a perceiver can evolve. By definition we must be both of and in reality.

My feel, (or thought) is that our brains hold an analog representation, or model of reality, that we constantly "check" against that which is "happening".

We improve our model by "discovering" or "learning" what is going on. (this normally aids in our survival, and our ability to predict and modify and "use" what is going on, to our benefit, and avoid what would be harmful)

And we have the ability to "put ourselves in someone else shoes." Here is where the "frame of reference" comes in, in my book. We HAVE the ability to consider the world from more than one. We can consider that the world fits together well, and ANY frame of reference will "add back" to ours, flawlessly. Thus establishing both a subjective reality AND an objective reality that exists for us to have evolved from, and to exist in, and to perceive.

I do not think that this way of looking at it denies either science or religion. But I do not know which camp these thoughts would put me in, in regards to this thread.

I personally look for the ways that "everybody" is "correct". And figure that most difficulties are "in the translation".

Regards, TAR2

Spacetime is four dimensional, and time is a dimension unrelated to movement from point to point.

Cap'n Refsmmat,

How can time be unrelated to movement from point to point, if movement from point to point, takes it (time)?

It takes a collection of matter (entity C) "time" to make the trip between collection of matter A, and collection of matter B.

In addition, since A and B are separated by this distance that it take "time" for C to transit, it take "time" for even light to make the trip between A and B.

Thus there is the "time" it takes matter to make the trip, AND there is the "time" it takes light to make the trip.

I think the distance between A and B can be defined as either the time it takes matter to make the trip, or the time it takes light to make the trip, and that these "distances" will equate.

There is a problem with considering "real", the idea that point A and point B are "no distance" from each other. If relativity requires that point A and point B be at the same point, in any dimension, that dimension must be hypothetical or "without" dimension.

Regards, TAR2

Oblate spheroid folks,

If from a stationary point, along the path of the high speed flyby guy, the Earth is a circle, and from the next point, the Earth is a circle, and from the next point the Earth is a circle, at what point is it not a circle?

I would think that the Earth could not be seen at all, unless there was light reflecting off of it. And the "shape" of the Earth would always be a result of the amount of the "sky" of the observer that was "filled" by the Earth. Arclength wise, this would be always be the diameter of the Earth whether horizontally considered, or vertically, or diagonally or any diameter direction you wish to consider. There is not a stationary vantage point from where the Earth would not be this circle shape. Why would it matter how fast one changed their observation point? The Earth would always be a circle. At no one point would it ever have a reason to fill a different shape. Would it?

Regards, TAR2

Iggy,

Those events could also, interestingly enough, be in your present instant again if you took on a sufficient velocity away from Alpha Centauri.

I don't think that is true. You cannot outrace light.

Regards, TAR2

SwansonT,

No reference frame that represents reality?

Not quite sure what that means. We have the Earth, we have human size scales of space and time. That is what we know. Why would any reference frame, that could not be mapped back to this one, have any meaning at all to us.

For instance, if something happens "now" on Alpha Centuri, it will not be "real" for us for another 4.5 years.

And any reference frame that is not "like" ours, were we "know" a particular place and time as here and now, is not a very useful frame, or very useful thing to consider "real".

If it doesn't map back to our reference frame, why should we even know or care about it, much less consider it "real"?

Regards, TAR2

Tar,

Your conversation with Iggy on presentism/simultenaity (what “now” means) belongs in the Ontology of Time thread.

Owl,

Perhaps, but my mind is concerned with the fact that what we know to be the case, is an imagined condition, based on past "actual" experience, that we predict will be the case in the future. So what we have "learned" is applied to our "predictions".

Subjectivity and Objectivity are interwoven in this consideration of "now" as deeply as it is for the "shape of the Earth".

Perhaps, since its your thread, I should listen to you. But I believe, that if you consider it a piece of the investigation of subjectivity and objectivity, you might entertain it here.

Regards, TAR2

The first relativity calls your past light cone and the second it calls the present instant.

 

So if what we see happening on Alpha Centuri, now, is our past light cone, and what is happening "now" on Alpha Centuri is happening in our present instant, what of the 4.5 years worth of "events" that are currently in transit?

What does relativity call those moments?

Regards, TAR2

Iggy,

I understand the concept that Einstein was talking about with similtaneity, and the important role that light speed plays in the determination of "distance" in both space and time. I go by it.

But there is a "reference" point, a viewer we use, to concieve of the observer "inbetween" that sees the two simultaneous moments, and this "viewer", that "sees" the inbetween observer IS NOT CONSTRAINED BY THE SPEED OF LIGHT. This viewer can be at both ends and in the middle, AT THE SAME TIME. This is not "possible", it can only be imagined, and only "proved out" by repeated experimentation, and memory of what was the case, before.

This is why I am leaning in the direction of there being two types of NOWs. One actual, and the other imagined.

Both however, real, in that the "imagined" one will indeed prove out to be the case.

More than likely Einstein and the other geniuses that have been cogitating on this for the last century, have indeed "figured" it out, put it down in writing and formulae, and tested it all out, to indeed "be the case".

What I object to is calling the view of this viewer, that sees both ends and the middle at the same time, the "real" objective truth. When this view, is actually the "imagined" one.

Regards, TAR2

Kturbo,

I was raised Christian, I said my prayers, I had long talks with God, I have no problem with anybody having a "personal" relationship with the universe/reality/nature/God, or whatever or however you want to call it.

I cannot have "your" relationship with the world. You cannot have mine.

It is not appropriate in my way of thinking, that anyone should think that "their" way is the only way it should be done.

That simply is not correct, or logically possible.

It is much more sensible to figure that EVERYBODY is doing it correctly. There is no doubt in my mind, that we are all of, and in reality, with approximately the same "access" to it. I don't have to use your key to open any lock. The door is standing wide open already.

Regards, TAR2

Iggy,

Thanks again for #109. I read it through a few time. Get hung up around the same time each time. Will have to read through it again a few times.

I don't like the "now" line at tzero. That looks too much like the universal now we have been talking about. That is not an empirically observable moment, from ANY reference frame. And it takes a God's eye, or at least an imaginary eye that "sees" instantly, events separated by lightseconds of distance "at the same time". If this imaginary view of "now" is to be considered "real", it can only be sensibly understood as what will be "real" seconds later. And I am left with the same question. Which "now" are we talking about?

There are a number of ways one can look at a moment, in both duration and in size. After all, from the point of view of an epiphany I had 30 years ago "life on Earth, from the first organic molecule till an evolved forest of Oak, and Maple and Pine, is but a fleeting instant in the vastness of time and space".

I wonder sometimes about how "scale" effects this discussion. We have no problem considering something we can hold between our hands, being in one place, at one time. But there is some fraction of a lightnanosecond's distance between our right and left hands.

At any grain size, from a quark to a universe, we can consider the whole thing contained in one thought (properly scaled). Existing at a properly sized "here" and a properly sized "now".

Not empirically proper to consider ANY two separated events "simultaneous". By definition they are separated. Either by time, or by the time light takes to go the distance.

Regards, TAR2

Iggy,

I am still reading #109. Thank you for doing that. I have had problems with my computer that I usually use, so I am not keeping up. Will "respond" after catching up with the thread.

Regards, TAR2

Iggy,

Still working on what "understandings" we can have, without relating one thing to another. And how much "time" it takes to make the comparison.

Such an investigation is one of the reasons I am on this board, and particularly on this thread.

Critical to the discussion though, is the fact that "time marches on" with or without us. And this progression is something that we are subject to, along with everything around us, and by extention, a "thing" that is happening everywhere, all the time, and has been going on since the beginning of the universe, and will continue to go on for a very long time, since we have no good evidence that it has any reason to stop.

Regards, TAR2

Iggy,

Oh. I understand. But there is the historical knowledge, of having sent something between A and B that "gives" us a knowledge of the distance. And then, we are in a position to predict the results, of repeating the experiment.

As much about reality, there is what has happened before, that "structures" the situation. That makes it real.

Time, in this regard, in my estimation, is something that we experience continually, and "measure" in retrospect.

Spacetime then is not something handily "present". That is, it does not appear to be something you can step out of and take a look at. There is no actual way to get out of it, or any platform available (other than here and now), where you can take a look at it.

There is however an "understanding" of it, that we already have. An analog model of the world, built in the synapses and connections and layout of our brains, that places actual items in the real world at various "distances" from us in space, and various events, in their proper "place" in time.

Time is an actual constituent of reality. One that we have already, as Kant would say, an intuition of.

Space is Kant's other "pure" intuition. Between the two, we have spacetime, if you will.

But simultaneity needs some heavy agreement on some rather deep "thoughts".

Perhaps the manifolds and equations lay out exactly what it is that I already have an intuition of. Perhaps they make of it, something that it is not. There are easy misunderstandings in "what is meant". And perhaps subtle misapplications, where an analogy is taken too far, or into a domain, where it does not belong.

It seems reasonable to me, that if the universe is a certain age, then ALL of it is that age. That makes it hard to figure what somebody could possibly mean by time slowing down or speeding up. Every piece of the universe, should have had the same time to evolve to where and how it is, in relationship to the rest, and should be at the point where the next moment, for it, has never before occurred. Each peice, at whatever grain size you choose, should have a past history, a present state, and a future state.

And there is no way to get to another place in the universe, without taking some time to get there, not actually.

But we can mentally take the trip, in "no time".

I think it important to note, the distinctions between, (as Owl put it), the map and the territory.

Regards, TAR2

but light is not at rest with A and B.

Iggy,

Why not? If a photon sees no time pass as it goes from A to B, and sees no distance traveled as it goes from A to B and has no Mass to move from A to B, I would say that is as "restful" as you can get. Since point A and point B are "glued" together by the photon traveling between them, and the impulse getting from A to B is what defines space and time, then the photon, the graviton, and anything else that connects point A and B at 186,000miles per second, is not a candidate for moving or being at rest, or having a relative velocity to any one particular other thing. Is it?

Regards, TAR2

Iggy,

Well thanks for that. My experiment would have no chance of finding rest (compared to the background radiation.)

But that does give us a rest frame to work with, doesn't it?

But why is it impossible to determine the distance between A and B if all your equipment, and both points are at rest?

Can't you put a mirror on B, bounce a light beam from A off of it, measure the seconds that elapse for the beam to return, use the fact that every second corresponds to 186,000 miles, and figure just how far A and B are from each other?

Regards, TAR2

Iggy,

I know I am confusing things. One has to have the same assumptions, go by the same rules, and use the same conventions, to actually know what another "means" by various statements.

But lets say a close to light speed experiment were to accidently take a path that countered the path and rotation of the milkyway, the path of the sun, and the motions of the Earth. The experiment, might then be at rest compared to the average motion of surrounding galaxies. In which case, if the experiment was as rest, the Earth would be moving close to light speed in its rest frame, and OUR clocks would slow?

Regards, TAR2

Dr. Rocket,

I am quite confused about the difference between special and general relativity, and I am not sure about a theory that is a "special" case of another theory, with "gravity" left out.

Where in reality do we find a situation where gravity is left out?

And isn't it better to have a theory, that fits it back in?

Regards, TAR2

Owl,

OK, trying to get back on topic.

Time is something. Like distance is something. You can measure them both.

I am not thinking it makes any sense that time slows down, or that distances shorten.

Once you establish a unit of either, based on some example, then you should stick to your units and your examples, and measure everything else, in regards to them.

If the speed of light in a vacuum is 186,000 miles per second, measured as 186,000miles per second in any inertial frame of reference, with all the instruments involved moving in concert through space and time, then we know what a second is, and we know what a mile is. Neither one is going to change, as long as everything we are measuring is moving as we are moving.

If on the other hand, the thing we are measuring is moving, relative to the frame we have established, say a clock, moving away from us at .886C, then it makes sense that by the time the second hand ticks to the next position, the clock will be 165000 miles away, and due to photon lag, we won't see the tick till the photons get back to us, which I think would be, by our stay at home clock reckonings, 1.886 seconds later. So it would appear that the moving clock is ticking .53 the speed of our clock. But nowhere, here, does it seem to me that time slows down. It is moving right along for us, and moving right along for the clock speeding away. If the traveling clock where to turn around and head back, I would think the ticks would appear to be ticking faster as the frequency would be appropriately blue shifted.

It would seem that the clocks should be back in snyc upon return. After all, we were moving away from it, as fast as it was moving away from us, and we were moving toward it, as fast as it was moving toward us, on the way back.

As Iggy might say, "which clock was at rest?"

Regards, TAR2

Iggy,

I myself am guilty of misunderstanding, lack of knowledge AND willful ommissions.

But be that as it may, there is something about reality that Owl and I have noticed, an "actual" nature to it, that four dimensional spacetime does not quite do justice.

Perhaps if we understood exactly what it was saying, but I for one do not. Not that I have not tried, but always there are aspects dropped out, or assumptions made, that I either cannot grasp, or simply do not agree with.

There is an understanding about time, that humans have, automatically, that I do not think is incorrect. To abandon this intuition, in favor of a formulae, that does not have the "natural" flow of human understanding attached solidly to it, is in my mind "unreal".

There remains to be discovered, the "link" between general and special relativity, that will tie them together, as understandable aspects of each other (or so I have heard.)

Mass and gravity "do something" to space and time. If it was not for matter, and the distances and interchange between one piece of matter and another, we would not have anything real to talk about.

To remove oneself from the fray, and consider an "objective" reality that exists without YOU as a participant, is somewhat fanciful.

Particularly on my mind the last several days is the question, "why is my now, the same now as everything elses, and everybody elses?"

We are connected in this fashion to everything. We are made of the same stuff. Subject to the same cycles. Bombarded by the same photons and gravity waves, that everything else is.

I am thinking, that the "universal" now, that we are aware of, is no accident. Regardless of the fact that we know Alpha Centuri is 4.5 lightyears from the Sun, it is in our sky NOW. Its photons are flooding our Earth NOW, its gravity is affecting us NOW. (as it was a moment ago) I am thinking that its distance is not so important, as the fact that it is with us NOW.

There is a shape that the Earth is, that we have determined from many perspectives. It is this way, because of the way everthing else is. And the way everything else was.

To do a thought experiment, that does not take the whole universe into consideration, might be leaving something important out.

I will for now, agree with Owl, that the Earth IS a sphere, and not an oblate spheroid. And any traveler, leaving from the Earth, and returning to the Earth, would add this fact to whatever it was she observed while flying by it at .886C. And I am rather sure, that she would at no point be able to leave the universe. Alpha Centuri, will continue to shine on her.

Regards, TAR2

wanabe,

Perhaps, but although subjective, there are many things people have in common with each other, that allows us, I think, to take an objective view of ourselves, by looking at our similarities to others.

Not scientific perhaps, but still effective, I think. Certainly one has to allow a wide range of differences, in terms of the other's experiences, knowledge, personality, goals, rules, will, principles and values, but I do believe we have a tremendous amount in common with each other.

If you have an insight about yourself, it is wrong to apply it automatically to everybody. But I do not believe there is anything wrong with keeping your eye out for where it might apply.

Regards, TAR2

Owl,

I think it was answered. Something about the loop-de-loop being an acceleration.

But I think I sort of see the point. Space and time are two aspects of the same "thing". Because of the "geometry" of this thing, changing position puts you in a different "place" in this thing. But the same way that exactly 12 spheres fit around a sphere of the same diameter in ping pong ball geometry...spacetime HAS TO fit together.

Mass effects its curvature and is affected by it.

Moving requires both a change in position, and the time to do it.

And the two have to add back and fit the geometry.

I have no idea what I mean by that. But I think it adds up to the Earth being an oblate spheroid if you fly by at a relativistic speed.

Regards, TAR2