Oh geez, Matt might hate me for this...

If the planets were travelling away from you, they would have a red tint. If they were travelling towards you, they would have a blue tint. Get your head around that

It's because red light is less energetic, and blue light is more energetic.

If light leaves the planet travelling away from you, if it was something normal, it would be travelling towards you slightly slower than if it had launched from something stationary with respect to (wrt) you. It's not something normal, it has to travel at the same velocity, so instead of travelling slower, it travels with less energy, effectively carrying less (as energy is mass).

Light doesn't have rest mass, LSD... LDS... SDS, that's it but it does have kinetic energy. It's only just real, it exists because it is travelling at the speed of light, thus giving the tiniest (ie zero) amount of (rest) mass, the potential to be infinitely bigger. It's nothing, but because it moves, it's something. The thing is, because it's nothing, it also takes zero energy to accelerate it to maximum velocity. Light speed is the only speed it can travel at.

It's also a self propogating fluctuation in the electric then magnetic fields. It seems these two fields work at right angles to each other in space. Blah blah yakkity yack.

 

I understand that I am seeing events that happpened one and two years ago when I look at objects having respective distances of one and two light years. This a matter of how long it takes the light to reach me but I think the train problem is something different.

The red shift -- yes if a luminous object is moving away from me its light travels toward me at the same velocity but is shifted to a lower frequency and thus is more red. It's like if I'm rowing in a rowboat away from a pebble dropped in a pond fewer ripples will pass by me in a unit of time than if I were sitting still on the water. I don't think this helps me with the train problem either.

The speed of light being the same for all observers regardless of how fast they're moving is one of the things that causes contradictions to arise. If the same thing were true of a bullet shot from a revolver, then a bullet shot by a person standing still on the ground toward the caboose of a train moving away from him would suddenly increase its velocity by the speed of the train as soon as it reached or was seen by a person watching it from the caboose. He (the person riding on the caboose looking at the bullet) would see the bullet travelling as much faster than the train as the stationary person who shot the bullet would see the bullet moving away from the gun just after it was fired. As if the bullet could have two different velocities or suddenly gain velocity. The bulllet would have the same velocity for both observers. I just can't understand how this can be the case even though I am told and accept that for light it is the case. I really don't know what's going on here is light something "magic"?

I'm lost and I agree we're currently getting nowhere. If I make any progress I'll let you know but right now I'm not making any. I need to the be able to completely understand that train example but I don't understand it at this point.

 

Well, time would be passing slightly slower for the observer on the train. That would give the bullet a slightly higher apparent velocity, see?

 

Light is only magic because it has no rest mass. Every moving body behaves somewhat like light depending on how fast it is moving. The idea that everything is moving at the same speed through space/time is important. Speed sacrificed in spacial movement is given to temporal movement.

I think time and electromagnetism are fundamentally linked. Electromagnetism quite possibly causes time, or something(?). Becasue light is stationary in time, it gives something objective by which time can be measured. Moving along an electromagnetic wave is exactly the same thing as moving in time. Do you see what I mean? The time from peak to peak of the wave will always be the same (assuming no change in gravitational potential).

Did you know also that 1 meter is defined as the distance light travels in 1/300000000 sec. So an observer moving with the light beam would measure a longer meter, an observer moving in the opposite direction to the light would measure a shorter one. Apparently space, as well as time, distorts when you accelerate. I don't know why both are necessary. I don't get it

 

Random Andy

I have two physics books on my bookshelf, both textbooks. The old one is from 1969. I always liked it, it explains things rather simply it doesn't even use calculus, one of its authors was a famous physicist George Gamow. The other one is somewhat newer from the 80s and is a lot more complex.

So I got these books out to see if I could learn anything more about relativity.

Remember how my friend said "It's acceleration not velocity" and we both agreed this is wrong (because for example in the case of the train moving at constant velocity there is change in time without acceleration). Well I found this statement in my old physics text: "Earlier in this chapter it was said that each of two observers, one on a space voyage and the other remaining on earth, would think the clock of the other was slow. Could we not then equally well argue that when landing after a voyage in space the traveler would find that earth clocks were slow and the error would be the other way? To help resolve this argument we can note that the two are not exactly equivalent. Earth has been virtually unaccelerated all the time the traveler was on his space voyage. The traveler on the other hand underwent a takeoff acceleration, a turn around acceleration and a landing deceleration. There have been arguments over this question for many years, but now most relativists agree that a clock on a spaceship would come back reading slow relative to an unaccelerated earth clock. The space traveler would return younger than his twin brother who remained at home."

Well just because it's in a book doesn't make it correct. But you can see that they're emphasizing acceleration even though we (you and I ) don't really understand why this is necessary or what additional difference acceleration makes as compared to just constant velocity.

My other physics book says "Photons have zero mass but they have momentum" (actually what it says is "Even though photons have momentum, they have zero mass"). I don't understand this either because momentum = MV and if M=0 how can the momentum MV not itself be zero? Looking at their equations what they seem to indicate is that the momentum of a photon = Plack's Constant divided by the light wavelength.

"Speed sacrificed in spatial movement is given to temporal movement." I don't know what you mean. I do understand that time changes with velocity, at least so they say. And space also chages with velocity.

"Light is stationary in time." I don't understand what you mean. Light requires time to get from one place to another. It travels at the speed of light, of course, expressed in units of distance/time.

The time from peak to peak of light waves I think changes according to the color of the light. Like we said yesterday, blue light is higher frequency than red.

On the moving train time passes more slowly as seen by a stationary observer but to a person on the train the time of the stationary observer passes more slowly, his own time seems ok to him, so it seems this cannot account for the bullet (i.e. light) being seen to move faster by the person on the train.

I just don't know anything about light with respect to electromagnetism. I'll see if I can find anything in my physics books. We know already that gravity affects light, but only indirectly -- actually it doesn't affect light it warps space.

I still wish I could get that train thing all figured out. Then I could use that as a basis for understanding the other stuff.

My newer physics book says: The entire theory of special relativity is dervied from just two postulates 1) All the laws of physics have the same form in all inertial frames and 2) The speed of light in a vacuum has the same valuue in all inertial frames.

What is an "inertial frame"? It seems to be an object at rest or an object with constant velocity. An accelerating object is not an inertial frame the book seems to say. This brings us back to the problem of why they keep talking about acceleration with respect to changes in the observation of time...

 

okay. Where to begin?

1 second in time is equivalent to 300,000 km in space. If your time is moving at one of your seconds per stationary observer's second, then you are stationary (spatially) wrt this stationary observer.
If you start to move in space (wrt the stationary observer), then your time will slow down at a ratio of 300,000km/sec. That is, for every km you move, you experience 1/300,000 of a second less than a stationary observer. Are you following? I think that's right.
Following this reasoning, you can see that if you were to move 300,000km, you would sacrifice 1 second. Thus if you were moving at 300,000km/sec, your time would not be passing wrt a stationary observer. He would see you travelling at 300,000km/sec but you would see the moment you dropped out of light speed at the same time as you saw the moment you reached it.

This couldn't happen because, as you accelerate you gain Kinetic Energy. The more Kinetic Energy there is in a body, the more Energy is required to accelerate it any further. As the body tends towards light speed, the Energy required to make it accelerate any further (ie reach light speed) tends towards infinity. Simply because there's so much energy already in the body.

An inertial frame is a frame of reference in which something stationary wrt to this frame is defined as having zero inertia. It's just a (fixed velocity) point of view.

 

About the astronauts being younger than others born at the same time:
I used to agree, but can't remember if I had really thought it through or if I just accepted what is accepted, if you see what I mean... but... doesn't the train example bear out my idea that it would even out and it depends on whether something is travelling towards you or away from you? I mean, in the train example, the front door seems to open before the back door (wrt the observer on the train). Oh, no, I'm confused now. I thought I had something

 

No, yeah. Because the front door is effectively closer to the observer on the train than the back door. Because the observer is moving towards the front door and away from the back door. That means that when you're travelling towards something it ages quicker and when you're travelling away from something it ages slower.

Is my understanding oversimplified, dya think?

 

Random Andy sorry I was away a couple days.

Hey in the following my format is screwed up again I don't seem to be able to figure out how to cite multiple quotes and separate them from one another -- but I take it you'll have no problem of course seeing what corresponds to my responses. In the boxes.

Yes that's my understanding.

 

Random Andy now I'll respond to your other two posts about the astronauts and the train example. But listen I don't understand all this myself.

Listen they SAY the astronauts come back younger compared to people who stayed at home and they SAY it's because of acceleration. But nobody has ever explained to me exactly or fully how or why acceleration is the critical factor. Because, as you yourself pointed out Random Andy and as my books about relativity seems to say -- and as they even represent in the equation [1-(v^2/c^2)]^1/2 -- simply moving along in a train at CONSTANT velocity makes a clock go slower compared to a clock on the ground. This is all fine and good -- except it leads to the Twins Paradox thing.

Yeah the Twins Paradox thing. The paradox is that each sees/saw the other's clock going more slowly. So when everybody's back home each one sees the other as younger than himself. And this obviously is a contradiction or paradox I don't understand at all and appparently neither does anybody else otherwise they wouldn't call it a paradox. One reason for this or maybe THE reason for this is you can't really say which one is moving away from the other. If there existed an absolute fixed point in space you could say who was moving and who was not, or who was moving faster with respect to this absolute fixed point. But no such absolute fixed point exists.

Now acceleration is one way "out" of the Twins Paradox because you CAN tell who is accelerating (the water sloshes to the back of the container) and who is not (the water stays level in its container). So I can understand this as being a potential reason for why the astronauts return younger because they accelerated and we here at home didn't. But nobody has explained to me HOW acceleration intervenes, I have not seen any mathematical equations, acceleration is not used in any of the examples in my books. And AGAIN they DO always say that even at a constant moving velocity time goes slower and they DO always give that equation with V^2/c^2 and that brings us right back to the Twins Paradox...

So there's something here that we need to know that we don't know. Does anybody know? Anybody here -- or anybody AT ALL??? HAS the Twins Paradox been solved or not? DOES time go slower in a reference frame moving at constant velocity with respect to another reference frame? Then WHAT is the solution to the Twins Paradox in this context without consideration of acceleration? It's like"OK society you've been telling me this crap for years now GIVE ME AN ANSWER." (Of course I'd have to study physics in depth -- but even then I'm almost beginning to wonder...)

Because I don't know how to use the "quote" function like I want to I'm going to stop here and go on to the train example in a separate post. Right now because I'm running out of time.

 

The train example. My favorite. If we could just get this figured out, as I said before, I think it would go a long way in helping us understand the rest we could use it as a reference model for understanding. But it doesn't tell us anything about accceleration. And it does lead to the Twins Paradox. We need greater understanding or some answers from someone or something about both of those.

You know I seem to recall there is a Physics website and you can ask questions and so forth. I have not referred to it in the course of working on this thread but it may be something to look into if I can find the time or if you want to Random Andy.

But I do seem to understand some things about the train example. For the passenger riding in the car the front and back doors of that passenger car open are seen to open at the SAME time. To the person standing on the ground the BACK door is seen to open BEFORE the front door because it is moving toward the rearward directed light beam that was sent out by the midseated passenger at the same time he sent out a forward directed light beam to the front door...

Hey I want to say this. It's very important to understand that in the train example THE ONLY REASON the observer on the ground does NOT see the doors open simultaneously is BECAUSE for him the speed of the train is NOT added or subtracted to the speed of light and NEITHER is it for the passenger on the train because the speed of light is the same for all observers and this is the "fly in the ointment", this is DIFFERENT than if the passenger on the train rolled ball bearings on the floor of the coach fore and aft to open the doors, if you roll ball bearings then you DO add and subtract the speed of the train from the speed of the bearings. I think it is very important to understand this. Maybe go back and look at my analysis of the moving train example. But while I'm saying this it still doesn't mean that everything is clear to me, there are still paradoxes that arise I think and I think the Twins Paradox arises from this very example because in one of my books they used a "light clock" on the moving train and to the guy on the ground it runs slower the way he sees it for the same reason.

Hey Random Andy:

 

Good to see you back dude

Once more into the breach...

KE is relative, obviously because it depends on velocity, but the equation you cited is the classical version. I think you'll find there's a slightly different equation for relativistic KE which makes small difference at low speeds (you'll probably find that it's something divided by c squared minus v squared, such that when c = v you're dividing something by 0 hence the answer is infinity, that's a guess though, I can't remember the equations from A level). When you use this equation you'll find that KE is proportional to gained mass and the square of the speed of light. KE = delta m x c^2. In words, Kinetic Energy is equal to change in mass (between rest mass and moving mass of the body) times the speed of light squared, recognise it? E = mc^2 isn't just about atomic reactions, energy really is mass, they're the same thing. So we're both right

If you were on a plane going at relativistic speeds, the ball and every other part of the plane and you would be heavier to a stationary observer (measurable by gravitational effects) but to you on the plane it would seem the same weight because to you it is stationary. This is one of the profanities (does that mean something that's profound as well as rude words? I mean it's something profound) of Relativity... everything is relative. Mass, energy, velocity, time, space, everything. Proper mind fuck ay?

I'll get to your other stuff later. Thanx for the correction on time dilation - I thought my way was a bit too simple.

 

Yes you're absolutely right there is a relativistic equation for KE, the equation I gave was the old nonrelativistic Newtonian one. I hadn't realized there was a relativistic equation because I had not yet read that far in my book "Einstein For Beginners". But I should have known better! Because as you point out there is an increase in KE with an increase in velocity but obviously there is also going to be a further KE increase as mass increases relativistically with velocity. I should have thought of that and I didn't. Thanks.

The book says that the relativistic KE formula is:

KE = {[(mc^2)/(1-v^2/c^2)^1/2] - (mc^2)}

And you're right all those things mass velocity time length and so forth they're all relative.

(And yes from this same formula and maybe some other stuff they derive the E = mc^2.)

(Should we say that mass and energy are the same as one another or that one is changeable into the other?)

***

Let me, let us, take a step back. I've already said this but let me say it again.The REASON for all these relativistic problems, the One Single and Only Reason for them, the "fly in the ointment" as I call it, is that the velocity of light is the same for all moving and nonmoving observers. The thing is, I wonder WHY this is the case. WHY is light different from everything else? As a contrasting example let's use sound waves (or a rolling ball bearing). If I'm a few hundred feet away from a guy who hits a piece of metal with a hammer I will hear the sound after the delay of a second or whatever (I forget what the speed of sound is in feet/sec). Or if he rolls a ball bearing toward me it will reach me (in whatever time) depending on its velocity. But if I am moving away from the guy with the hammer greater than the speed of sound I will NEVER hear the sound the hammer made. Just like if I am travelling away from him faster than the ball bearing rolls the ball bearing will NEVER catch up to me. But it's not the same for light. If I'm looking at myself shaving in a mirror and my friend is holding a flashlight so I can see to shave, then I start moving away from my friend while still looking in the mirror, I can never outrun the light like I can outrun the sound waves or the ball bearing and not only that but the light will OVERTAKE me and at the SAME VELOCITY as I observed when I was standing still. If light behaved like sound waves or the ball bearing, then one would outrun the light and cease to see one's self in the mirror. This example is given in my "Einstein For Beginners" book. The book seems to say that this was one of Einstein's original thoughts that led him toward all his relativity ideas. The book seems to say that one of Einstein's original thoughts was "I should be able to see myself in a mirror no matter how fast I'm going. My image in the mirror should not fade away no matter how fast I go." The book seems to indicate that the reason he thought this is because that you can never tell whether you're moving or not "without looking outside" and if you're looking in a mirror shaving or whatever and your image starts to fade away then you would know you were moving without looking outside and that's not allowed.

Well I still don't understand why light is different from everything else. I don't understand where this comes from, how this is. Light catches up with you and passes you by no matter how fast you're going. I don't understand at all why this is the case. This is the source of all these relativity problems.

I'm just thinking out loud.

***

Random Andy as if we didn't already have enough to think about there's something I want to bring to your attention that I find very interesting. It was in that old physics book of mine that I like. I used that book at Kent State one summer. That's where the four students were killed protesting the Vietnam War on May 4 1970 as you probably know. Actually you may or may not have ever heard of that I don't know. It always had a big effect on me. Anyway suppose we have two boat docks, A and B, ten miles from one another on the coast near Dover. We row a boat at a speed of two miles per hour from A to B and then from B back to A -- a round trip -- which takes us of course 5 + 5 = 10 hours for the complete round trip. Now consider two boat docks on the Thames ten miles from one another and suppose the Thames is flowing at 1 mph. Now how long will the round trip take us? Suppose B is downstream from A. As we row downstream from A toward B we gain 1 mph from the river (so we're going 3 mph) and as we row from B back to A we lose 1 mph from the river (so we're only going 2-1 = 1 mph). One MIGHT THINK -- this is what I thought! -- that the gain and loss in speed from the river in the two different directions would cancel each other out and the round trip would be the same as at Dover. Not so, do the calculation! It takes 10/3 = 3.33 hours to get from A to B on the Thames and to get back from B to A it takes 10/1 = 10 hours so the round trip takes 13.33 hours whereas it only took 10 hours to make a trip of the same distance in the nonflowing water along the coast at Dover!

This thing fascinates me. It seems to go against some kind of common sense, at least MY kind of common sense. I understand that the answer works out this way but I have trouble grasping the "gut reason" of what's really going on here. The best I can come up with is something like "It's because you have a lot shorter time to compensate going faster the one direction and a lot longer time to lose time going slower the other direction." But I'm not sure that's exactly it.

Now does this boat-on-a-river-roundtrip example have anything to do with relativity. Well, the time loss due to the river flowing is not relativity in the same sense as with light rays and so forth. However this example in my old physics book is provided in the Chapter on Relativity. The reason they give this example, it appears, is because they then go on to consider the example of a boat CROSSING a flowing river and the time differences caused by this, and the reason they give the boat crossing a river example is because this corresponds to one of the experimental test set ups they used to determine that the speed of light is the same no matter who the observer is and there's no aether...

Anyway even this little boat on a river problem causes me problems.

***

Listen I've got to shut up. But I want to say two things. First, I get called away on jobs and I'm not expecting this to happen for a couple weeks but when it does happen then I only have internet access on stolen time on weekends at public libraries. But even if I disappear you will hear from me again when I'm able.

The second thing is, what I'd like to do is start a careful step-by-step list of the progressive thoughts and considerations in the development of relativity. You don't have to do this but I want to. I want to see them written down and I want them to be step by step. This will help me to see what I understand and what I don't entirely understand. Just because I write them down doesn't mean I completely understand them.

I believe this list should start out as follows:

1. The original "Principle of Relativity" (according to my book "Relativity For
Beginners") says that you can't tell if you are moving (at a constant
velocity) or stationary with respect to a point without looking at that
point.

2. Scientific evidence demonstrates that the velocity of light is the same for
all observers no matter how fast you are moving.

3. Scientific evidence shows there is no ether, no medium (other than space)
necessary for light to travel in. Sound waves need air to travel but light
waves don't need anything.

(We will see whether I decide to continue this list or whether I will decide it's not the best thing to do.)

(Hey what is space is it something or is it nothing? It has to be something. But what? It's not matter. It's not energy. What is it?)

Listen here's the thing if you pursue ANYTHING far enough in terms of understanding you always come up with a TOTAL MYSTERY and NO ANSWERS and this is why philosophy is where it's at! You SUSPECTED my prejudice in this direction Random Andy long ago and I ADMIT to it now!

In the intellectual domain everything is ultimately a mystery and the physical domain always fails to completely satisfy so where does this leave us? It's not a very pretty picture.

Still, some stuff makes more sense (the nonexistence of "free will") than other stuff (the existence of free will), and some physical stuff is more pleasing than other physical stuff...

The word you want, the noun derived from the adjective "profound", is "profundity"! "One of the profundities of relativity..."

 

Hey SDS. It feels good to be back here

I'm sorry I haven't been around for a while but I'm working pretty hard on this project I'm trying to get started. With the baby and keeping the little lady happy I'm quite busy. I read your last post a few days ago and have been thinking about it but haven't even put pen to paper with the boat problem so don't expect many insights about that from me (yet).

I totally know what you mean about everything being such a load of meaningless nonsense. Nothing makes any sense does it. But I think it's important to go through reality before you get to unreality. Science (physics, at least) does lead to philosophy, but it does achieve something on the way that philosophy on its own wouldn't. But then I suppose you'll tell me that it's the other way round, philosophy leads to science, and historically you'd be more correct.

Maybe it is more healthy to wonder, without knowing all the 'facts' science gives us, before one starts to learn these 'facts' and reasons. It seems to me (having stopped my sincere study of science almost a decade ago now) that there's plenty of time to wonder once you 'know' the 'facts' (excessive inverted commas annoy me but they're kinda necessary considering what we're discussing).

There's a coupla things I want to ask, in case you can enlighten me.
This is just as much Newtonian as Einsteinian I think, but how do they know how fast two objects orbit each other? I know they can measure the distance and work out how much centripetal force is required to keep balance with gravity, but doesn't that imply there's some way of knowing what is 'still', if not in terms of linear motion then in terms of rotation. Because it's got nothing to do with where the two objects are facing or how fast they're spinning (individually). This is a bit of a mind-bender to me. There are so many things about science that I used to take for granted and it's not easy questioning them.

I'll give you an example because that last paragraph was ungainly and perhaps impossible to understand.

If two objects are orbiting each other, but spinning such that they are always facing each other, then in that rotating inertial frame the two objects appear entirely weightless. Gravity seems to have no effect. If the orbit were eliptical the effect would be even more bizarre. Could a misapprehension of how fast we are actually spinning be responsible for dark matter and dark energy?

If light is effected by gravity (and it surely is) then it could orbit something in a circle in space. But light (travelling at 3 x 10^8 m/s) doesn't experience time, so wouldn't it run into its own arse and form a closed loop in space time? Could this be how matter is formed (except that it would be spread over huge swathes of space, not the sub-pin-prick it is)?

A planet is a light year away, so obviously you see what was happening a year ago and they see what you were doing a year ago. According to lightspeed being constant, when you accelerate toward them, your perception of their time passing would slow down because the light leaving their planet would seem to you to accelerate with you (a negative acceleration, because it's in the opposite direction of the light flow). It would therefore take more time for the light to reach you. However, your perception of their time passing would speed up as well because you'd be getting closer to the source and it wouldn't have to travel as far to reach you. Is this an analogy of the flowing Thames thing (and why relativistic equations are so fucking complicated)?

I'm not sure if the fly in the ointment is the constancy of the speed of light. I still think it might be the 'who is really accelerating' question we were talking about earlier. I'll give you what appears to me to be a simple thought experiment that proves the objective loss of time by a space traveller is not the truth. In terms of relativity.
(A physicist once told me that, though some real experiments have backed up relativity's time dilation assertions, enough have come back with errors in the opposite direction to suppose that there is no measurable time-dilation at all, although the dilation that was supposed to be measured was so tiny anyway it's hard to say)

There's a planet with a population and someone leaves as some light leaves, then the person comes back. Relativity says that he will have aged less than those on the planet, but surely the distance the light is from the planet when the traveller gets back can be objectively measured (or at the very least measured such that the traveller (who is now stationary again) and the people who stayed agree). However if the speed of light is constant to all observers and the traveller has made no net movement (ie he ended up in the same place he started at) and the traveller has experienced less time. Distance (agreed)/ Time (disagreed) = Speed (disagreed)

Do you see what I mean? The speed of light is not the same to the observer who moved and those who stayed still. It doesn't make sense.

I'm gonna go look up the Michelson-Morley experiment, which is the only experiment name I can remember of all those I've heard of. I think it's the one that seemed to show light always travels at the same speed.

Hope to hear from you soon.

 

Hello Random Andy here I am again and it was good to see your last post.

The bottom line is I am unable to really answer any of the questions you raise there. The issues are too difficult for me it's as simple as that!

The only bit of "good news" (I don't like excessive quote marks either and I think this is because there has developed you know a corresponding gesture using the second and third digits of each hand and this gesture is overused and maybe there is something unappealing about the people who tend to overuse this gesture however I must at the same time say that people generally can't help the way they are and I should not be so critical in this respect it's just like bigotry and everything is a complex issue...) is that I agree with your thought experiment that it would seem either that the speed of light is not the same for the two observers or that there is no time discrepancy. That's an interesting scenario did you come up with that yourself? The only thing I am able to say that comes to mind is they always insist the speed of light is the same for all observers and if indeed time is disagreed in the equation the only way to get the speed to come out the same is if there is also a disagreement about distance but I'm not able to see how such a distance disagreement is possible. So this is a paradox I'm unable to solve and since they claim the speed of light IS the same for all observers and there IS time dilatation with travel all I can say is we need help here or at least I need help. It's beyond me at this point.

A few other comments.

Could light orbit something in a circle? I don't know I never thought of that. It sounds fascinating. They say light can't escape from a black hole so it would also seem you could have light trapped in an orbit around a black hole. Would this form a closed loop in space-time hmm maybe gee I just don't know it's beyond me. Could this be how matter is formed? Now that seems less likely to me even though energy can be converted into matter and vice versa what would provoke this transformation in this circular orbit situation? But I know so little here I probably shouldn't say anything at all. And if it were a closed space time loop the matter would never get out and we would never detect it. This is just all beyond me. Have you read Steven Hawking's book "A History of Time" I have not read it. I intend to read it some day when I'm ready. I want to know more before I try to read it. Does he talk about this kind of stuff like light in circular orbits? This is just all beyond me. I'm not willing to say at this point what is or is not the truth. All I'm willing to say is we or I don't understand.

Could a misapprehension how fast we are spinning be responsible for dark matter and energy? I have no idea, whatever you are talking about here is way beyond me.

With two objects rotating around each other you talk about them appearing weightless and gravity having no effect. I don't follow you here at all. Each object exerts a gravitational pull on the other and on anything else around. There could be people living on each object held to their surfaces by gravity. And another thing. "A and B rotating around each other" it seems to me is the same as "A rotating around B" is the same as "B rotating around A." They are all equivalent it just depends where you want to arbitrarily place your stationary point it might be between them it might be in the center of either of the two bodies. We normally think of the moon rotating around the earth but it is also possible to think in terms of the moon being stationary and the earth rotating around the moon. When two binary stars are of roughly equal size we tend to think of them as rotating "around each other" and maybe the center of gravity is between them or something but I think you can think of either of them as rotating around the other or however you want. I think you can take any point in space and define that point as stationary and say the rest of the universe albeit lopsided in many cases is rotating around that point. The earth can be the center of the universe if you want. Or the moon. Or any other point. I think. Anyway I just don't follow you here at all. Sorry. I don't understand your saying weightless and I don't know what you're leading up to.

And then your scenario of speeding toward a planet that's one light year away. This should be simple but I can't address it yet there's something I need to know that I don't know. I know or think I know that they say that when someone is travelling away from me I see his clock going slower (and he sees mine going slower). My question then is if someone is travelling toward me do I see his clock running also more slowly or faster? Well if it's running faster when he's travelling toward me then how can they possibly say that a space traveler who left earth and returns comes back younger (EITHER because of velocity OR because of ACCELERATION -- we haven't even had THAT satisfactorily explained yet) because the time change in the one direction would be cancelled by the change in the other.
Until I learn about this at least I better not try to handle the seemingly simple scenario of what would be seen travelling toward a planet one light year away. But -- well -- when one light year away you'd see what happened one year ago and by the time you got there you'd have to be caught up so I guess you'd see two years' worth (what happened a year ago plus what happpens in the year it takes you to get there) of events happening in one year so you'd see everything happening faster is that correct? Does that mean you'd see light moving on that planet at twice the speed of light? I don't feel qualified to address this at the present time.

***

[Note: All of what follows, from here on, is inadequate but at a later time I will probably be able to be more explicit and tie things down to specific cases.]

There's something else I want and need to say. What I want and need to say is that there are just too many problems here. We need some answers. Or at least what are claimed to be answers. Answers, explanations, to some of the questions we have been asking. Like the solution to the Twins Paradox. And whether it's velocity or acceleration.
But in fact there's even more. It's even WORSE than that. The reason I say it's worse than that is because there are things going on that make things even worse than I first realized.

For example.

Remember I was using ball bearings in the passenger car instead of light waves?

Why was I rolling ball bearings on the floor of the passenger coach instead of beaming out light waves fore and aft?

I was rolling ball bearings as a simpler case scenario for purposes of comparison to light because ball bearings are ordinary, unlike light the speed of ball bearings is NOT the same for all observers, ball bearings behave ordinarily you DO add and subtract the speed of the coach to the speed of the ball bearings rolling on the floor I was trying to see what things are like without relativity.

But then it turns out that when you're rollling ball bearings in a moving coach there's still relativity because the time is passing more slowly and they are more massive and the distance in one direction is shorter and all this stuff even though we're not talking about light waves at all. So this screws me all up.

I still say we need to go back to the simplest thing possible which is the train example, the simple basic case of one object moving with respect to another and painstakingly have every element of this situation explained bit by bit until we completely understand all the ins and outs both using ball bearings and light waves.

Well that kind of petered out but there's alot going on there AND it also leads to the following.

What it leads to is and what I also want to say is there's something else lurking right here, right here in the shadow just INCHES away. We're on the edge of it ALL THE TIME we just haven't quite brought it up yet.

It's a philosophic problem. One of the big grand-daddies of all philosophic problems.

It's being in relationship to knowing.

The material realm in relationship to the mental realm.

The relationship between mind and matter. Between consciousness and physical reality.

The constancy of the speed of light for all observers leads to what we call CONTRADICTIONS, I believe.

Do these contradictions that arise from relativity represent anomalies in what we KNOW or in what IS?

Can two mutually exclusive things physically coexsist but just not mentally coexist? Or vice-versa? Or both?

There is SOME RELATIONSHIP between mind and matter. We DON'T KNOW what this relationship is.

Also we don't know what consciousness is. We don't know how to manufacture or measure consciousness or empirically demonstrate consciousness "See there it is that's conscious! or "I have some consciousness here in this test tube!" (!!!)

I need to express these last thoughts more concretely.Something about realtivity straddling the boundary betweeen mind and matter (but everything does that) and whether from relativity we can learn something about the connection between mind and matter.

Here's something I wrote down yesterday:

"Knowing is absolute: the same speed of light. Being is not absolute." I forget what I was getting at. It'll come back to me later probably.

We can never seem to know, never get a handle, on what IS, materially. We can only know what we know, what we perceive. Then how come the speed of light is absolute and constant, since light is not only something that we know but also something that is? Is light a constant element, the one constant element, which straddles the boundary between what we know and what is? Is light the one thing that IS that we also KNOW? Or something along those lines.

But what about knowing things outside of the context of light?

I'll just have to talk about this stuff more later when I can do so more concretely.

Maybe I should try to look at a physics/relativity website.

Let me know what you think about anything. I'd still like to have the train example dealt with thoroughly. And have some of our other recurrring questions answered.

Michaelson-Morley had light beams travelling at right angles to each other (using a half silvered mirror at a 45 degree angle) each going the same distance and no matter how the apparatus was oriented with respect to the moving earth the beams reached the observer at the same time so there was no "ether wind" of the earth moving through the ether. If there were an ether with the earth moving thru it then there'd be a phenomenon like different times of a boat going across and back a river versus its going the same distance up or downstream and back. But it's easier to look in a textbook and see a picture and the math than to take it from this description.

With all these questions and problems we may as well turn the smile upside down.

I'm dissatisfied with what I've written here today.

 

An inertial frame can spin can't it? If not, what can't it spin relative to? And if so, it could spin with the planets, with an origin at the centre of mass of the system, and it would seem as if there were no gravity, but if you span the planets back one way the would fall together, and the other way they'd fly apart.

 

Again I'm not sure you're talking about here.[But look what I say toward the end.] Let me just say some things and let me know if this covers whatever it is. I'll be saying a bunch of things and let me know whether this covers what you're talking about or not.

(I will just be thinking out loud here let's see where it leads us I don't know myself yet what I'm going to come up with.)

Yes an inertial frame can spin. The earth is an inertial frame. It spins with respect to all the other objects we see in the sky the moon the sun the planets the stars etc.

By reference to these other objects we are spinning.

BUT it is also possible to consider the earth as the stationary point and not spinning and everything else spinning around us. Considered in this way we (the earth) are not spinning.

So does this mean we can't tell for sure who's spinning and who's not?
Is this a situation just like the situation of two objects (two inertial frames) moving away from one another at a constant velocity and you can't say which one is moving away from which, it's however you want to define it? Are we in that kind of situation where you can't tell in an absolute sense?

Well, with constant velocity you can't tell which one is moving and which is stationary it's however you want to define it. You can't tell with constant velocity if you are moving or not without looking outside at an object you define as "stationary" to compare yourself to. (I guess this is the original "Principle of Relativity" according to my Einstein For Beginners book.)

But with ACCELERATION you CAN tell who is moving and who is not. The water sloshes to the back of its container and stays there as long as you're accelerating linearly. You don't have to look outside...

And SPINNING is also considered a form of acceleration. (Not because there's a constant change in speed but because there's a constant change in direction. At least this is what physics says, that's the way they define it.) And just like with linear acceleration you can tell if you're spinning or not without looking outside because if you're spinning the water sloshes to the ouside of the container and stays there as long as you're spinning (accelerating). (It's commonly refered to as "centrifugal force" but I guess it's really just the water in the container wanting to continue in a straight line it's actually the inertia of the water I think is what physicists like to say not really "centrifugal force.")

THEREFORE it seems to me we could tell that the earth is spinning even if it were the only object in the universe with no other object to look at and compare our movement to. We could always tell the earth was spinning because the water sloshes to the outside of the container and stays there (we can't see this effect I presume because it's so small but I presume it is there and could be detected with sensitive instruments).

But now I want to enter gravity into consideration with the spinning and it seems this makes things a little more complicated.

Gravity counteracts the "centrifugal force" of spinning. This centrifugal force is always at right angles to the axis of spinning. Whereas gravity is always pointed radially at the center of the earth. Well if you were at the equator these two forces would be directed 180 deg away from each other. And if the earth were spinning fast enough the centrifugal force would be equal to the force of gravity and the water would be weightless. So if you were at the equator on a planet spinning at such a speed you could interpret things as actually not knowing if you were on a planet having gravity but spinning fast enough to make the water weightless OR if it was a nonspinning planet AND having no gravity! (But if you knew gravity always existed and the water were weightless you'd know you were spinning.)

But if you're not at the equator the "centrifugal force" will be at some angle with respect to the force of gravity other than 180 degrees and so you'll know you're spinning because the water will be a little deeper at one end of the pan than at the other. For example if you're in the northern hemisphere a pan of water should be of uniform depth (by gravity radially directed to thte center of the earth) if the earth is not spinning but with the earth spinning as it does I think the water will be a little deeper at the south end of the pan nearer the equator than at the north end of the pan. It sloshes down there toward the south because it's a little further away from the axis of rotation of the earth and the "centrifugal force" is greater there.

Or if you were at one of the poles the water is uniformly deeper at the edge of the pan than at the center because of the earth spinning...

This is way too long again. I'm almost done but not quite.

So at this point it SEEMS you can tell whether an object is absolutely spinning or absolutely still with respect to the space contained in the universe. (But you could be travelling linearly at any velocity and not know it, this has no meaning except with respect to another point of reference...)

So after all that Random Andy maybe I understand your scenario after all. If the WHOLE solar system were spinning centered on the sun fast enough then the "centrifugal force" of the planets would be great enough to overcome the gravity of the sun and the planets would go on their merry way. Or if the whole solar system IS spinning centered on the sun and it slowed down the planets would crash into the sun.

{{{How can we tell if the solar system is spinning or not centered on the sun? We could raise a pan of water up in space directly over the north pole of the earth and see if it sloshes to the outside of the pan. Actually we should be able to tell with any pan of water above the plane of the earth's rotation around the sun. (Provided we know the "intrinsic gravitational force" of different substances... so we know whether it's the sun's gravity or spinning that's affecting the state of the pan of water. I mean if we found out or knew that the sun's gravity were less than it was supposed to be then we would know that the solar system is spinning centered on the sun. The thing is if you're orbiting the sun or any other body stuff is weightless -- not because it's weightless and not because you're not being acted on by gravity but because you're constanting falling, accelerating at the rate brought about by the gravity of the object you're orbiting. Now this is getting too complicated for me right here and now at least. Well. To simplify I guess you could just raise a pan of water above the north pole of the sun and if it sloshes to the outside of the dish then the whole solar system is spinning. Is that correct???}}}

It bothers me that we can detect "absolute spinning or nonspinningness" within the framework of the space of the universe if indeed this conclusion, that such detection is possible, is correct.

 

There's a problem I think. We were talking about "having the whole solar system spin" -- as an entire unit in addition to the rotation of the planets around the sun. I think there may be a problem with this concept. What it amounts to is having a unit or section of space spinning with respect to the surrounding space. And I'm not sure that is possible, I've never heard of such a thing, I don't know how it could be produced or what it would mean or what would happen if it were possible. So I'm not going to pursue the idea very far unless you want to.

You can have spinning objects in space and objects spinning around each other in space but I've never heard of units or sections of space (with or without objects in them) themselves spinning. If this is possible I don't know how and if it were possible I don't know what all it would mean.

 

I wrote this last night and forgot to post it:

If two objects spin around each other, both are free falling in the other's gravitational field. If one object is much heavier than another then the centre of gravity of the system is nearer the heavier object, but they're always spinning around each other.

But here's why I mentioned dark energy and matter:

Each galaxy seems to be spinning so fast that they should fly apart. Gravity seems to be smaller than the required centripetal force to make them stable but they are stable. To account for the apparent extra gravitational force, physicists have invented a hyptothetical substance called dark matter.

All galaxies seem to be flying apart quicker than theory would suggest they should do (I don't know exactly what theories). For this anomoly physicists invented the term dark energy.

It seems to me that both of these could be accounted for by different rates of rotation to those we assume to be true. Or maybe the formula for gravitational attraction is actually much more complex than Gm1m2/r^2.

And yeah, an absolute value for how fast one is spinning seems a little wierd. I mean, how do the particles know? What is the body spinning relative to? Within a gravitational field perhaps? I don't know.

There's also the whole coriolis effect which is a bit bizarre and non-intuitive. I never quite got to grips with that, maybe I should try now.

 

So you see, if, as you put it, whole sections of space were spinning, this might account for dark matter and energy.

I think of it as gravity being created by a kind of vortex left behind matter as it travels through time. This force might work in a spiral like water flowing out of a plug, because of coriolis effects of our movement within the larger (in terms of volume), but weaker (where we are) gravitational force of the rest of the galaxy, and then universe.

The point is that if gravity generated its own spin, then all kinds of currently supposed 'absolute' measurements would be wrong.

Therefore things may not be as simple as we think in terms of calculating our spinnyness (I think spin sounds a bit more sensible than spinnyness so will use that from now on).

[The spinning water in our plug hole is caused by the coriolis effects of the Earth's movement. Corriolis forces also cause hurricanes.]

But then I just thought, the only reason the Earth experiences corriolis effects is because it's a solid sphere. Funky Diva. Am I making any sense here?