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MilkyJoe
2010-Apr-17, 06:25 PM
If you were to constantly observe an object travelling away from you and it gets to a point where what you're seeing is (let's say) 1 light year away, since you never took your eye off it and what you're seeing is in the past, where does that missing time go?
Let's just forget any practical problems with actually doing that.

speedfreek
2010-Apr-17, 07:57 PM
Whatever you look at, you are seeing it as it was in the past, even the screen showing you these words. The "missing time" is the time it takes the light from an event to reach your eyes.

Hornblower
2010-Apr-17, 08:00 PM
If you were to constantly observe an object travelling away from you and it gets to a point where what you're seeing is (let's say) 1 light year away, since you never took your eye off it and what you're seeing is in the past, where does that missing time go?
Let's just forget any practical problems with actually doing that.

1. What do you mean by "missing time"?

2. What do you mean by "where does it go"?

Hornblower
2010-Apr-17, 08:04 PM
I should have looked for new posts just before posting mine. speedfreak's answer looks excellent.

kleindoofy
2010-Apr-17, 08:06 PM
... what you're seeing is in the past ...
What you are seeing is in the present, not in the past.

You are seeing the photons which were emmitted from or reflected off the object in their present state of being, in their state of being in the instant they hit the receptors in you eyes. Those photons are physical objetcs which have travelled the distance from the object to you in real time, not as time travellers.

While the photons' present state of being may represent a past state of the object, the object has just kept on existing and moving.

MilkyJoe
2010-Apr-17, 08:42 PM
When you first see the object the light takes a fraction of a second to reach you; when it's at a distance where it takes 1 year to reach you, you're seeing it as it was a year ago.
What if there was a timer on it somewhere, and you had a timer (synchronised, obviously) with you ? Would they remain the same (as seen by the observer), or would the timer on the object be 1 year behind?

cosmocrazy
2010-Apr-18, 09:36 AM
When you first see the object the light takes a fraction of a second to reach you; when it's at a distance where it takes 1 year to reach you, you're seeing it as it was a year ago.
What if there was a timer on it somewhere, and you had a timer (synchronised, obviously) with you ? Would they remain the same (as seen by the observer), or would the timer on the object be 1 year behind?

Now you are delving into relativity, welcome to BAUT MilkyJoe. :)

what is read on the timers depends on the observer's relative speed to the travelling object and their respective frames of reference. This subject is one of the most commonly debated here on BAUT and you might want to check out some of the previous threads about this first. In the mean time someone with a better understanding than myself might give you a more detailed and accurate answer than I can.

JohnD
2010-Apr-18, 10:05 AM
You are also approaching Zeno's Arrow Paradox.
http://plato.stanford.edu/entries/paradox-zeno/#Arr

John

astromark
2010-Apr-18, 11:20 AM
The term ' From who's point of view ' Springs into view...
If I were able to 'see' that clock on that ship as it speed away from me its time would start out as the same.
When you say its a ly away that is to say its taken that image a year to reach you... If that craft was to travel quickly you might need to wait for the light image to reach you... According to the rules...Light can only travel at c. So according to me ( I might be completely wrong ),:o:
If its a year away then only after a year passes would that clock match yours... But do not quote me... Its complicated by all sorts of hideous rules.

Andrew D
2010-Apr-18, 11:27 AM
What you are seeing is in the present, not in the past. [...] While the photons' present state of being may represent a past state of the object, the object has just kept on existing and moving.

Yes, and so the object does not still exist in the same state as it appears to. Thus, we are constantly observing that which has already happened, not that which is happening presently.

Also, it seems you're assuming that the brain takes zero time to receive and process visual stimuli.

astromark
2010-Apr-18, 11:51 AM
The question; What happens to time ? Is very easy to answer correctly. That answer is 'Nothing happens to time.'
There is no aspect of time that we can change. It (time) cares not for our understanding and dithering about...
It just rushes at us the same way it has been for billions of years. Only our perception of it can change.
If you are accelerated it slows. The view of the rate of passage of time is relative to the frame of reference of the observer.

MilkyJoe
2010-Apr-18, 12:14 PM
Wouldn't the time it takes the brain to process it be negligible if you're talking about a year to reach you?
Would time appear to be going slower on the object?
The speed of the object moving could be anything. Going really slow or the speed of light.
I just thought if you never take your eye off it the whole time - so you've always seen it - and the time appears to be 1 year behind, there must be missing time somewhere.

MilkyJoe
2010-Apr-18, 12:37 PM
The question; What happens to time ? Is very easy to answer correctly. That answer is 'Nothing happens to time.'
There is no aspect of time that we can change. It (time) cares not for our understanding and dithering about...
It just rushes at us the same way it has been for billions of years. Only our perception of it can change.
If you are accelerated it slows. The view of the rate of passage of time is relative to the frame of reference of the observer.

I agree with that. Time just keeps ticking regardless. But how does it slow if you are accelerated?
Does it just appear to?

MilkyJoe
2010-Apr-18, 01:18 PM
Try to think of it this way: Let's say it takes 1 year to travel to a distance where it takes 1 year to reach you.
You've watched the object and seen it for a year, but you're seeing it as it was a year ago. A year ago it was with you.

kleindoofy
2010-Apr-18, 04:51 PM
... we are constantly observing that which has already happened, not that which is happening presently. ...
Yes and no.

As far as the photons are concerned, we are seeing what is happening presently -- to the photons.

As far as the original object is concerned, we are seeing (approximately) how it looked when those photons were emmitted.

John Jaksich
2010-Apr-18, 05:24 PM
To me --at least time is a perception that is based on "Einsteinian Relativity" as alluded to . . . as well as photons entering into the rods and cones within the "eye" --and penultimately how the brain may perceive it?

Have you ever noticed how a "blind individual" might perceive time? -- or thought of it?

They have their own "devices" used to tell time, as well. -----> sometimes by way of sound (chimes , e.g. or by "touch" on a device similar to wrist watch?)

Very Well thought out question!

Jeff Root
2010-Apr-18, 07:57 PM
The question that MilkyJoe is asking doesn't really require relativity.
It is a very simple question of light travel time.

MilkyJoe,

Are you really asking a question that you can't answer on your own?
Obviously as you watch a spaceship get farther and farther away from
Earth, you will see clocks aboard the ship reading farther and farther
behind your clock. And obviously the people on the spaceship will see
your clock reading farther and farther behind theirs. You don't get to
see what their clocks read until long after they do, and they don't get
to see what your clock reads until long after you do. Each of you sees
the other as slightly slowed down, due to the time required for light to
travel longer and longer distances as you and the ship get farther and
farther apart. Adding relativistic effects to that makes it interesting.

On a side topic...

The time required for the eyes and brain to process the visual signals,
while negligible compared to the light travel time between Earth and
a distant spacecraft, is enough to be noticeable. In the 1970's, while
playing with an electronic calculator, I discovered that color vision is
slower than night vision. The calculator had red LED's, and I was
playing with it in ambient light some time before sunrise.

-- Jeff, in Minneapolis

MilkyJoe
2010-Apr-18, 08:13 PM
MilkyJoe,

Are you really asking a question that you can't answer on your own?

Er, yeah...

About the brain processing time, it's both negligible and irrelevant, seeing as it's the same from when you first see it to when it's however far away.

Anyway, I think what would happen is pretty much as you said. What I think is odd is, even though you've watched the object/spaceship for 1 year (or however long), what you're seeing is the object when it isn't a year older.

MilkyJoe
2010-Apr-18, 08:26 PM
(Lets say it's a spaceship)
Since time would appear to be going slower, if it had 2 blinking lights on it, and you had 2 blinking lights with you blinking exactly the same frequency, would they blink slower? Since time would appear slower you'd think that, but since the light travelling from the lights would arrive to you as they blunk they should be the same speed.

kleindoofy
2010-Apr-18, 09:00 PM
Let's not forget that the object (spaceship or other), at least as implied by the definition of the OP, is not moving at the speed of light.

Jeff Root
2010-Apr-18, 09:23 PM
MilkyJoe,

If the spaceship went some distance from Earth, then stopped and
maintained constant distance, you would see the flashes of its light
emitted after the ship stopped moving blink at the same rate as your
light. While the spaceship is moving away from Earth, you will see
the blinking of the spaceship's light as slower than your light. That
is because each time the light blinks, it is farther away, so it takes
longer for the light from that blink to reach you than it took the
light from the previous blink. The faster you and the ship move
apart, the greater the difference in the blink rates.

-- Jeff, in Minneapolis

MilkyJoe
2010-Apr-18, 09:28 PM
MilkyJoe,

If the spaceship went some distance from Earth, then stopped and
maintained a constant distance, you would see the flashes of the
lights after the ship stopped blinking at the same rate as your light.
While the spaceship is moving away from Earth, you will see the
blinking of the spaceship's lights as slower than your light. That is
because each time the light blinks, it is farther away, so it takes
longer for the light from that blink to reach you than it took the
light from the previous blink. The faster you and the ship move
apart, the greater the difference in the blink rates.

-- Jeff, in Minneapolis

That makes sense, thanks.

astromark
2010-Apr-18, 10:00 PM
The organised blinking lights tell the whole story..very good. Its red shift all over again...

uncommonsense
2010-Apr-19, 06:41 AM
In my humble opinion, there is a much deeper way of understanding this. The OP asked about "time", and explanations about time were given - but an explanation of "time" was not. A deeper understanding of what, why, or how time behaves starts with an understanding of what time is.

I have nothing original to offer, so I'll quote Einstein:

"If we wish to describe the motion of a material point, we give the values of its co-ordinates as functions of the time. Now we must bear carefully in mind that a mathematical description of this kind has no physical meaning unless we are quite clear as to what we understand by ``time.'' We have to take into account that all our judgments in which time plays a part are always judgments of simultaneous events. If, for instance, I say, ``That train arrives here at 7 o'clock,'' I mean something like this: ``The pointing of the small hand of my watch to 7 and the arrival of the train are simultaneous events.''3

It might appear possible to overcome all the difficulties attending the definition of ``time'' by substituting ``the position of the small hand of my watch'' for ``time.'' And in fact such a definition is satisfactory when we are concerned with defining a time exclusively for the place where the watch is located; but it is no longer satisfactory when we have to connect in time series of events occurring at different places, or--what comes to the same thing--to evaluate the times of events occurring at places remote from the watch."

On the Electrodynamics of Moving Bodies, 1905

Further reading of Einstein reveals length contraction occures along the single axis of motion according to velocity. So velocity and length (distance) are interchangeable, therefore velocity/distance measurement ("time") is said to be relative. It is perhaps more accurate to understand that the moving object realizes 3 dimentional space with one dimention (axis of motion) "contracted". All time/clock explanations follow from there - in my humble opinion.

Please correct me if I am wrong.

cosmocrazy
2010-Apr-19, 08:59 AM
The question that MilkyJoe is asking doesn't really require relativity.
It is a very simple question of light travel time.

I don't agree, the question involves time, motion, distance and frames of reference. Although the question is a simple one to answer on the surface in depth what is actually happening is much more complicated.



MilkyJoe,

Are you really asking a question that you can't answer on your own?
Obviously as you watch a spaceship get farther and farther away from
Earth, you will see clocks aboard the ship reading farther and farther
behind your clock. And obviously the people on the spaceship will see
your clock reading farther and farther behind theirs. You don't get to
see what their clocks read until long after they do, and they don't get
to see what your clock reads until long after you do. Each of you sees
the other as slightly slowed down, due to the time required for light to
travel longer and longer distances as you and the ship get farther and
farther apart. Adding relativistic effects to that makes it interesting.

On a side topic...

The time required for the eyes and brain to process the visual signals,
while negligible compared to the light travel time between Earth and
a distant spacecraft, is enough to be noticeable. In the 1970's, while
playing with an electronic calculator, I discovered that color vision is
slower than night vision. The calculator had red LED's, and I was
playing with it in ambient light some time before sunrise.

-- Jeff, in Minneapolis

This is the simple most logical on the surface answer I agree.

speedfreek
2010-Apr-19, 07:11 PM
One aspect hidden in the OP is the notion of simultaneity between events in relative motion.

How does your "now" relate to "now" on the spaceship that is now 1 light year away? Was it "now" on that spaceship, 1 year ago?

What about as the spaceship was receding - how do the two frames of reference notions of "now" diverge?