A Discussion of Time

[Pondering Youngster]

Before I say anything, keep in mind I am not an expert in thisfield by any means; I am a mere high school senior with an interest in physicsand many questions regarding the subject. I may be entirely incorrect ineverything I bring up, and I will not at any point claim that my theories areanything but speculation. I am searching for counterarguments to my hypotheses,not trying to declare them fact.

 

 

The Premise:

 

If the Sun wereto spontaneously disappear by miraculous means, people say that from a referenceframe on Earth we would see its light vanish eight minutes after the event, andat the same time we would fly off tangent to our elliptical orbit. Myquestion is simple: Why do the eight minutes matter? Ignoring as of yet unexplainedcircumstances and extraneous theories to the contrary, nothing can travelfaster than the speed of light. The fastest we could possibly observe the stateof the Sun is the time it takes light and gravity to reach us. People say thatbecause light has a finite speed, we are "looking into the past" whenwe look at the Sun, stars, planets, and any light source in the night sky, butif it is impossible to know the "present" due to the limitation ofthe speed of light, there is no significance to those events being "in thepast". It seems to me that these people see the universe as a3-dimensional space which time "happens" to as a blanket phenomenonrelevant to all locations in exactly the same way, whereas in reality time isonly relevant to each distinct point in space.

 

 

The Hypothesis:

 

Describingpatterns in the universe would be easier if we considered time a relativephenomenon, instead of a universal constant. Events are only relevant when wecan observe them from our reference frame, and no earlier, thus for all intentsand purposes, the Sun disappears at the very instant we see it disappear noteight minutes prior to the observation.

 

 

Troubleshooting:

 

Isuggested this theory to many of my more intellectual friends and all of themdisagreed with me from the outset, thus I have an extensive list ofcounterarguments that have been nullified along the way.

 

 

Let's say thereis a person floating in space some distance between the Sun and Earth. Theywould see the Sun disappear some number of minutes before we do on Earth,thus they would tell us that they saw the Sun disappear some number of minutesbefore we saw it disappear, thus we know from the reference frame on Earth theSun must have actually disappeared before we observed it.

 

You are considering two different reference frames and assumingyou can instantly know both reference frames' observations at the same time,which is impossible. Say you are the observer on Earth. If the observer inspace comes rushing at the speed of light (yes I know it is impossible, justtheoretically) to tell you about the event as soon as he sees it. It will takehim exactly as much time to come tell you about the event as it will take forthe light from the Sun to stop reaching you (for you to observe it yourself),thus you will still never be able to know about the event until you see itoccur. Delving into the more shakey side of the topic for me: if the observerin space moves at the speed of light to come tell you about the Sundisappearing, in his reference frame no time passes for him to get to you, thusfrom his reference frame you see the event at the same time he does, so itmight as well have happened at the moment either of you saw it happen.

 

 

What if thelight hits some gravitational field which makes it do a few loops beforecontinuing? Couldn't the observer in space swerve around the gravitationaldisturbance and get to the Earth before the light does?

 

Light takes the shortest time path between two points; there is noway to get between points A and B faster than light does.

 

 

If we werestanding on the Sun's surface, we would see the Earth go dark sixteen minutesafter the Sun disappeared, so there is obviously a time difference between whenthe event actually happens and when the Earth sees it.

 

You're looking at the situation from the reference frame of theSun, not Earth, so the problem is entirely different. I'm not saying that thelight would move from the Sun to the Earth at an infinite speed, I'm sayingthat events might as well occur at the moment that you see them happen from aparticular reference frame. From the Earth as a reference frame, the Sun mightas well have gone dark the moment you see it go dark, and from the Sun as areference frame the Earth might as well go dark the moment you see it go dark(sixteen minutes later, not eight minutes later, because I amproposing that the time it takes the light to get from the Earth back to theSun is irrelevant)

 

 

But then inone reference frame it takes light no time to get from the Sun to Earth, and inanother it takes light sixteen minutes, how is that possible?

 

Time is not universal, it is relevant only to your referenceframe, you cannot compare the two values.

 

 

Say there's aplanet off to the left of the Sun that reflects light from the Sun towards theEarth. If the Sun disappears, this planet will go dark to an observer on Earthsometime after he sees the Sun vanish. How can we say events happen as we seethem if we see the effects of the Sun's disappearance some time after we seethe disappearance itself?

 

Once again, I'm not claiming that light travels at an infinitespeed. Assuming the planet is behind the plane of the Sun relative to Earth,the delay in what we see will be exactly accounted for in the time it takeslight to get from the Sun to the planet in the first place, plus the extradistance the light has to travel to then get to the Earth because the planet isfarther away than the Sun. This time delay does not contradict my theory thatwe can consider the initial event to happen at the moment we observe it to happen.If an observer equidistant from the Sun and the Earth records the time it takeslight to get between the two entities and we call this time x, the time ittakes for light to then bounce of another planet and get to the Earth will be xplus some value y based on the distance of the planet from both the Sun and theEarth. I am not stating that x + y should be considered a total time of zero, Iam arguing that x should be considered 0, thus the time it takes light tobounce off the planet and reach us can be considered y, not x + y,for every possible application.

 

 

Pretend there is a mirror floating in spacethat is angled perfectly so that we can shine a very bright light at it fromthe surface of the Earth and observe our reflection. You argue that we cannotsee into the past, but we would see an earlier version of the Earth in thatmirror.

 

I am not arguing that we cannot see into the past of ourreference frame, I am arguing that the “past” of locations other than ourreference frame might as well be offset by the time it takes light to get fromthat location to our reference frame. In this case my argument would be thatwhat we see in the mirror is the present state of the mirror, and that wearen’t seeing an image of a past state of the mirror, because we have noway of knowing anything more recent about the mirror than what we see there.

 

 

Closing Statements:

 

I haven't yet considered any practical applications of this slightly different method of viewing time, partially because going any further with the idea transcends my knowledge at this point. For all I know the viewpoint is a) completely wrong, b) interesting but irrelevant, or c) long since old news. Whether you agree or disagree post your opinion for my sake.

 

 

 

The formatting got confused by my copy/paste between Word and the forum, so spaces are missing here and there, my apologies

[ajb]

So, different observers will in general not agree on simultaneity of events. You understand this as due to the finite speed of light.

 

Great, however this is a standard result to be found in special relativity. Indeed your opening premise seems very close to special relativity and you use the language of reference frames (you mean (local) inertial frames).

 

Take a look at the Wikipedia entry on special relativity. Then have a look at the entry on simultaneity.

Edited January 19, 2011 by ajb

[Pondering Youngster]

So, different observers will in general not agree on simultaneity of events. You understand this as due to the finite speed of light.

 

Great, however this is a standard result to be found in special relativity. Indeed your opening premise seems very close to special relativity and you use the language of reference frames (you mean (local) inertial frames).

 

Take a look at the Wikipedia entry on special relativity. Then have a look at the entry on simultaneity.

 

Interesting, so this is much older news than I expected. And your second link says pretty much exactly what I stated above, slightly disappointing. Can every pair of events then be said to have simultaneity from at least one inertial frame?

[ajb]

Interesting, so this is much older news than I expected. And your second link says pretty much exactly what I stated above, slightly disappointing.

 

This goes back to the conception of special relativity, around 1900. Einstein's special theory of relativity we published in 1905.

 

Can every pair of events then be said to have simultaneity from at least one inertial frame?

 

Yes. You could investigate this using Minkowski diagrams.

[uncool]

Interesting, so this is much older news than I expected. And your second link says pretty much exactly what I stated above, slightly disappointing. Can every pair of events then be said to have simultaneity from at least one inertial frame?

No. I think that ajb wasn't quite thinking about it correctly; this actually corresponds the notion of the difference between "spacelike" and "timelike" separations.

 

It is true that for any pair of events, there is a frame where either the two can be said to be simultaneous (in which case the separation between the two is called 'spacelike') or there is a frame where the two are considered to have happened at the same location (in which case the separation between the two is called 'timelike').

 

Something that is true: for any pair of events, there is a third event such that the first and third event, and the second and third event, are separated by spacelike intervals.

=Uncool-

Edited January 19, 2011 by uncool

[ajb]

No. I think that ajb wasn't quite thinking about it correctly; this actually corresponds the notion of the difference between "spacelike" and "timelike" separations.

 

 

You are right, I was thinking specifically about space-like intervals, not that I said that.

Edited January 20, 2011 by ajb

[md65536]

Interesting, so this is much older news than I expected. And your second link says pretty much exactly what I stated above, slightly disappointing.

No, I think that your interpretation is different from the one described by "Relativity of simultaneity" according to SR.

 

Specifically I think you are suggesting that events separated by "light-like intervals" be treated as simultaneous to an observer who sees the 2 events appearing to be simultaneous (IE someone colinear to the 2 events and closer to the 2nd event), while SR treats 2 such events as separated by a time equal to d/c, where d is the spatial distance between the 2 events.

 

So, SR would still say that the Earth observes the sun disappearing 8 minutes after it ceased to exist, according to Earth's reference frame, but that other observers (in frames with different relative velocity, or in different gravitational fields according to GR) will determine a different time difference between the 2 events.

Let's say thereis a person floating in space some distance between the Sun and Earth. Theywould see the Sun disappear some number of minutes before we do on Earth,thus they would tell us that they saw the Sun disappear some number of minutesbefore we saw it disappear, thus we know from the reference frame on Earth theSun must have actually disappeared before we observed it.

 

If this person signaled you at the same instant that it observed the sun disappearing, then that is an example of a "light-like interval" (between the sun disappearing and them signaling you).

 

 

I think that if you were to fully develop this idea, you would encounter a lot of inconsistencies that could be resolved by a reformulation of time, but doing so would result in some bizarre requirements, such as the speed of light not being invariable and finite, and stuff like...

But then inone reference frame it takes light no time to get from the Sun to Earth, and inanother it takes light sixteen minutes, how is that possible?

I've been developing a theory which claims that this, and most of the rest of your interpretation of simultaneity, is literally true. I've posted about it on these forums before, but I stopped because the theory was full of holes and I was unable to answer questions about it. Hopefully within a month I'll be able to post again, and explain it...

 

 

But yes, I think your idea is good (probably even correct), but not consistent with the definition of time used by special relativity (which by the way is literally the definition of time that we use by standard, in which even the unit of time -- the second -- is defined in terms of c).

Edited January 21, 2011 by md65536