Question Relativity and the past and future

[Slinkey]

Can't distant non-moving points define common clock time? You subtract knowing the speed of light and your separation.

 

I think you probably can, yes. If you are not moving relative to each other and you know your spatial separation it should be calculable. It would just be an arbitrary convention however, rather than a definitive time.

 

Or you can imagine a common source clock halfway between. I don't see what you're laying out, Slinkey.

 

What I am trying to get across to the original poster is that we have to take into account spatial separation in our calculations for an object moving relative to us. The first effect is due purely to the fact that light takes time to cross space but is dependent on the direction of movement of the object relative to ourselves (simply put if the object is moving away their clock slows down and if they are moving towards you then their clock will speed up. This is not to be confused with relativistic time dilation which had I more time last night I was going to try to explain. I'm at work right now (on a saturday! ) so really don't have the time now either, but hopefully when I get home tonight I will have time to try and clarify a few things for the original poster.

[thedarkshade]

Tachyons are thought to be moving faster than the speed of light. It's not like you can send them or they have been sent to the speed of light because you'd need infinite energy to send them to the speed of light. So they're born moving faster than the speed of light. I mean, they have to move faster than the speed of light because if they move at the speed of light, they'll have infinite energy, and so one of their weird characteristics is that the faster they go, less energy they posses, just like the equation shows:

 

[math]E=\frac{m_0c^2}{\sqrt{\beta^2 -1}}[/math]

 

As you see in the equation if tachyons move at the speed of light, we'll get zero under the fraction, and as anything divided by zero tends to infinity, then they'd have infinite energy. They just have to move faster than light.

And according to the Special Relativity if you exceed the speed of light, the order of events will begin to reverse, so in a way they belong to the past. So why can't we detect tachyons coming from the future, since we are the past of the future?

 

Just interested to know

 

Cheers,

Shade

[Norman Albers]

If you plot out the permittivites, [math]K_{rad}, K_{trans}, [/math] in my gravitation paper, the interior portion, [math] r<m [/math] has the K's becoming less than one, and going to zero at the center. (The transverse permittivity is negative but comes to zero similarly.) This implies asymptotic speed of light!

[thedarkshade]

Norman, could you say what you just said, but in a more normal and "easy to understand" way?

[Norman Albers]

We speak of the local vacuum electric permittivity, the [math]\epsilon_0[/math] which relates electric fields and sources. You should be used to the concept of light going slower in a dielectric medium. Water, glass, plastic, all have additional polarizability which we call total permittivity or index of refraction, and is always greater than unity. Were it less, light-speed would be higher than c. What I did in this paper is to substitute the equations you can find in an E&M book for dielectric fields, into the Scwarzschild metric solution for a BH. That whole process assumes that physics is locally everywhere the same. However, the distant observer measures light and all matter "oscillations" relatively slowed approaching the event horizon. These equations of mine yield a most curious set of graphs in the interior.

[thedarkshade]

We speak of the local vacuum electric permittivity, the [math]\epsilon_0[/math] which relates electric fields and sources. You should be used to the concept of light going slower in a dielectric medium.

Yeah! [math]\epsilon=\frac{\epsilon_r}{\epsilon_0}[/math]

[Norman Albers]

So I have joined the PV -theory club by showing how the dilations implied in the GR solution of a massive object may be seen as an increase in the permittivity, a "thickening" of the vacuum. If you study the E&M solution for fields in a dielectric, there's a sort of feedback in the equations so that as the increased polarizability approaches a value of 3, you get what's called "dielectric runaway" in E&M lab, where permittivity blows up. This is equivalent to the speed of light going to zero near an event horizon. I picked up on your tachyons, darkshade, because the interior solution has permittivity coming back from its blowup near the horizon, and even going down through unity inside, as I described before.

[asprung]

How could time slow for a space traveler, relative to that on earth, and yet he returns to earth in its present.

[insane_alien]

because it is always the present. if he returned somewhere at any other time than the present when he done it, it would be very very strange.

[Klaynos]

"it's always now everywhere, Miss"

[iNow]

Haven't we answered this question for asprung in like three different threads already?

 

 

http://www.scienceforums.net/forum/search.php?do=process&showposts=0&starteronly=1&exactname=1&searchuser=asprung

[swansont]

Yes, we have. Threads will be merged.

 

"The present" isn't something that is measured on a clock.

[iNow]

"The present" isn't something that is measured on a clock.

 

That's right. It's a gift which we are perpetually unwrapping.

[asprung]

Does "now" progress uniformly while time at a diffrent rate ?

[iNow]

That is an interesting question, but I don't think it has an answer.

 

What does it mean for "now" to "progress?"

What does it progress "into?"

How are you defining "uniform progression?"

 

 

The second part, however, is yes. The rate of time passage is relative to each observer.

[swansont]

Does "now" progress uniformly while time at a diffrent rate ?

 

No, the way "now" progresses is different, because that's time. What reading you get on a clock for "now" will depend on your reference frame.

[asprung]

What I mean does the present move into the future at a rate independent of time. Does the universe age uniformly while clocks can run diffrently.

[Norman Albers]

We can say that the physics of the processes we fairly well understand have the same character when viewed locally, anywhere, but from a perspective in a distant locale with a substantially different metric, all process is at a different rate. It seems to me there are logical problems of embeddedness at all scales.

[asprung]

All that exists is "now". The past has become history and the future has yet to arrive. How, according to relativity, can the space twins "now" fall behind that of earths ?

[iNow]

All that exists is "now". The past has become history and the future has yet to arrive. How, according to relativity, can the space twins "now" fall behind that of earths ?

 

Asprung,

 

This has been explained before, but I'll try again (I think this is like the 7th time you've asked the same question?)...

 

 

The passage of time, or the "duration" of elapsed time of the two observers is different, but if they are meeting one another, then they share the same reference frame (and they share the same now), regardless of where and when they have been previously.

 

It's like you're asking, "If one person came from England and another came from Russia, how is it possible that they are sitting beside one another in China." They travelled different paths, and it took them both different lengths of time to get there, but once they are there, they share the same reference frame.

 

Time is not different in this regard. You seem confused because one traveller came from England and the other came from Russia...essentially, one traveller took a different path to get there, and on that path, less or more time has passed than the other dude.

[swansont]

All that exists is "now". The past has become history and the future has yet to arrive. How, according to relativity, can the space twins "now" fall behind that of earths ?

 

It doesn't. Nobody except you claimed that it did.

[Slinkey]

What is now for me is your past by virtue of the fact that we are distinct entities separated in spacetime. Literally, your "now" is a collection of past events that you perceive at any given moment. Therefore it could be argued that "now" is actually the past.

[iNow]

That's right. It's a gift which we are perpetually unwrapping.

 

Okay. I want to punch myself in the face for this one.

[asprung]

Do I understand that we all share common points of transition from past toward future while our rates of passage through time my differ ?

[asprung]

The space twin is in his year 2000. He starts to drift in outer space. The earth twin is in his year 2050. He takes off in a sister ship and docks with the space twins ship in outer space. The twins meet in an air lock between the ships. Does the earth twin fall back to the year 2000, or does the space twin jump to the year 2050?

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