Relative Nature of Time: Is it True?

In summary: It seems only relative times and sequences can be established, and only after one chooses a reference frame. (one of the three locations) This is basically the idea behind relativity of simultaneity.
  • #1
eon_rider
22
0
Question:

Let’s say one observes three events on Earth while looking up at the night sky. One being right next to an observer on Earth (a flash light turning on), a second being on the moon (a large flash of light of some sort), and a third on Proxima Centauri, (perhaps a massive solar flare or the star going supernova).

Let’s say these events are observed simultaneously on Earth.
They are all observed at (t1)

If the Earth event happened at t1, then the moon event must have happened at t1 – 1.3 seconds wrt Earth, and the Proxima Centauri event must have happened at t1 – 4.22 years wrt Earth.

Still they all appeared to happen simultaneously at our observation point on earth. However, another observer on the moon or a third near Proxima Centauri will state definitively that the events happen in a different order. So no absolute times or absolute sequences of these events can be established.

It seems only relative times and sequences can be established, and only after one chooses a reference frame. (one of the three locations)

Is this a workable way of looking at the relative nature of time and temporal events?



Eon.

EDIT: It may be better to replace Proxima Centauri with another planet in our solar system like Mars because the time it takes light to reach Mars is known more precisely. Cheers. E.
 
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  • #2
yes your right, The view points on the moon and on the Earth (about which light went on first) is equal; that is to say they are both just as vaild as the next. This is the reason you should not think of time in special relitvity as "flowing" from one second to the next. time is relitive, So relitive to an observer on the moon he will see that light go on first but an observer on the Earth will see the light on the Earth go on first.
p.s. i can't spell
 
  • #3
Thanks for your thoughts Simon.

The view points on the moon and on the Earth (about which light went on first) is equal;

OK.

This is the reason you should not think of time in special relitvity as "flowing" from one second to the next.

I don't understand what you mean by this.

Time is relitive,

I think you are right.

Einstein says the following about time.

"Events which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity). Every reference-body (co-ordinate system) has its own particular time ; unless we are told the reference-body to which the statement of time refers, there is no meaning in a statement of the time of an event."

Now before the advent of the theory of relativity it had always tacitly been assumed in physics that the statement of time had an absolute significance, i.e. that it is independent of the state of motion of the body of reference. But we have just seen that this assumption is incompatible with the most natural definition of simultaneity; if we discard this assumption, then the conflict between the law of the propagation of light in vacuo and the principle of relativity (developed in Section 7) disappears.

Albert Einstein
Relativity: The Special and General Theory

To me, The above is 100 percent correct.

I was kind of trying to determine if there is a type of relativity of simultaneity that depends on just location without reference to the state of motion of an object (body).

Or if I was conflating two different ideas and had my wires crossed somewhere. :smile:

best and thanks for the reply,

Eon.
 
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  • #4
eon_rider said:
Question:
Let’s say one observes three events on Earth while looking up at the night sky. One being right next to an observer on Earth (a flash light turning on), a second being on the moon (a large flash of light of some sort), and a third on Proxima Centauri, (perhaps a massive solar flare or the star going supernova).

Let’s say these events are observed simultaneously on Earth.
They are all observed at (t1)

If the Earth event happened at t1, then the moon event must have happened at t1 – 1.3 seconds wrt Earth, and the Proxima Centauri event must have happened at t1 – 4.22 years wrt Earth.

Still they all appeared to happen simultaneously at our observation point on earth. However, another observer on the moon or a third near Proxima Centauri will state definitively that the events happen in a different order.

So no absolute times or absolute sequences of these events can be established.
Actually, this is not what the "relativity of simultaneity" is all about. After all, this sort of thing (perceiving events in different orders) would be just as true with sound waves in Newtonian physics, but there is no disagreement over simultaneity there. Simultaneity deals with the time-coordinate you retroactively assign an event after taking into account the signal delay--for example, if I see a flash happen right next to me, then 1.3 seconds later I see a flash on the moon, then 4.22 years later I see a flash on alpha centauri, I will say that all three events happened at the same time-coordinate in my frame, even though I didn't see them at the same time. An observer who is at rest in my frame and who is sitting on alpha centauri will see them in a different order, but when she takes into account the light-speed delays of the signals in reaching her, she will also conclude all three events happened at the same time.

Where the relativity of simultaneity comes in is when different observers are in motion relative to each other, and they each retroactively calculate the times of different events based on the assumption that light signals travel at c in their own frame. So, for example, if I'm in the center of a train car and the light from two flashes at opposite ends of the car reach me at the same time, I'll retroactively conclude both flashes took place at the same time, since the light from each flash had an equal distance to travel to reach me. But now say that at the moment the light flashes reach me, I pass right next to you standing on the side of the tracks, and you also see both flashes at that moment. From your point of view, at the moment the light reaches you both ends of the train must be at equal distances from you (because at that moment you're passing next to me at the center of the train), but since the train is moving, this must mean that in the past, when the flashes were set off, the front of the train was closer to you then the back of the train. So, if you assume the light from each flash travels at the same speed relative to you, then for the light from each flash to reach you at a single moment, you must conclude the flash at the back of the train was set off before the light at the front of the train. So in your frame, the two flashes cannot have happened simultaneously once you take into account the signal delays, even though the light from each one reached you at the same moment.
 
  • #5
Looks like I was mixing up apples and oranges.
Thanks for the clarification. :biggrin:

So, for example, if I'm in the center of a train car and the light from two flashes at opposite ends of the car reach me at the same time, I'll retroactively conclude both flashes took place at the same time, since the light from each flash had an equal distance to travel to reach me. But now say that at the moment the light flashes reach me, I pass right next to you standing on the side of the tracks, and you also see both flashes at that moment. From your point of view, at the moment the light reaches you both ends of the train must be at equal distances from you (because at that moment you're passing next to me at the center of the train), but since the train is moving, this must mean that in the past, when the flashes were set off, the front of the train was closer to you then the back of the train. So, if you assume the light from each flash travels at the same speed relative to you, then for the light from each flash to reach you at a single moment, you must conclude the flash at the back of the train was set off before the light at the front of the train. So in your frame, the two flashes cannot have happened simultaneously once you take into account the signal delays, even though the light from each one reached you at the same moment.

Your example above makes it clear. I think remembering the standard embankment and the train example is the best way to remember the concept of simultanaety. It works well.

best,

Eon.
 

1. What is the relative nature of time?

The relative nature of time refers to the concept that time is not absolute and can vary depending on factors such as speed and gravity. This was first proposed by Albert Einstein in his theory of relativity.

2. Is the relative nature of time true?

The relative nature of time has been supported by numerous experiments and is widely accepted in the scientific community. However, there are still ongoing debates and research on the topic, so it is not considered a proven fact.

3. How does the relative nature of time affect our daily lives?

The effects of the relative nature of time are not noticeable in our daily lives. Time dilation, which is a result of this concept, only becomes significant at extremely high speeds or in the presence of strong gravitational fields, which are not encountered in our everyday experiences.

4. Can we control or manipulate the relative nature of time?

Currently, there is no known way to control or manipulate the relative nature of time. However, there are ongoing studies and experiments exploring the possibilities of time travel and manipulating time through advanced technologies and theories.

5. How does the relative nature of time impact our understanding of the universe?

The relative nature of time has greatly impacted our understanding of the universe and has led to the development of new theories and concepts such as the theory of relativity and the concept of spacetime. It has also helped to explain phenomena that were previously unexplained, such as black holes and the expansion of the universe.

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