When moving at the speed of light time stops

In summary: Suppose you have a nice standard plane polarized...In summary, time doesn't freeze for photons traveling at the speed of light.
  • #1
eyad-996
18
2
If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?
 
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  • #2
eyad-996 said:
If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?
Do you think maybe it's because you're not moving at the speed of light?
 
  • #3
What do you mean?
 
  • #4
time flow is observer dependent in relativity. 8 minutes is measured from an observer on Earth for example.
 
  • #5
Pauli's exclusion principal?
 
  • #6
eyad-996 said:
Pauli's exclusion principal?
How could that possibly be relevant?

You may want to read the FAQ on the rest frame of a photon:
https://www.physicsforums.com/showthread.php?t=511170

Basically your opening statement "when you're moving at the speed of light time freezes" is fundamentally invalid.
 
  • #7
eyad-996 said:
If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

As has already been pointed out, you CAN'T move at the speed of light. However, light can, so the second part of your question is meaningful.

Do you understand the concept of distance = rate x time ? Rewritten as time = distance/rate, you could use this to figure out how long it would take you to go 1 mile if you are going 60 miles an hour. How about you apply this to light traveling from the sun to the earth.

EDIT: Do you understand that all I've done here is expand post #2 ?
 
  • #8
basically Einstein's own question 'what happens if i move at speed of light' is not answered in his theory since nobody can move with that speed (no clock neither)
 
  • #9
Okay, I think there is an interesting question here. I did read the FAQ before posting.

So far we know that because an axiom of the theory of special relativity is that light moves at c, we cannot use that theory to describe time dilation for a photon. One might still ask, DO we have a theory that suggests the meaning of time for a photon? I am still curious.

Or maybe I have misunderstood something?

Edit:

In the FAQ the last bit is "The concept doesn't make sense."

I guess I'm asking if in some other theoretical framework it does make sense?
 
  • #10
ThereIam said:
One might still ask, DO we have a theory that suggests the meaning of time for a photon?
Not that I am aware of.
 
  • #11
in hofstadter's book goedel escher bach it is called the mu-method of answering a question by -deasking- it.
 
  • #12
ThereIam said:
One might still ask, DO we have a theory that suggests the meaning of time for a photon? I am still curious.

No. There is a sort of geometry that describes photon's worldlines, and one's ability to make "equally spaced" marks along them, even though one cannot assign a non-zero value to the spacing of the marks.

THis sort of geometry is called an "affine geometry".

It's an interesting topic, but it's a mistake to think of it as having all the properties of "time". That tends to lead only to self contradictions and confusion.
 
  • #13
eyad-996 said:
What do you mean?
Your question started:
If when you're moving at the speed of light...
But you're not moving at the speed of light. You are stationary. The light is moving at the speed of light.
 
  • #14
I'm not talking about me moving at the speed of light, I'm talking about light itself! Light is moving at the speed of light (obviously!) Shouldn't time freeze for light and arrive instantly - since time has stopped for it!?
 
  • #15
eyad-996 said:
I'm not talking about me moving at the speed of light, I'm talking about light itself! Light is moving at the speed of light (obviously!) Shouldn't time freeze for light and arrive instantly - since time has stopped for it!?

You have some a notion of time, and you assume that light must have some sense of it too. And this idea is wrong.

Time is something that can be measured, and assigned values. This gives geometry a metric structure. We can say "the interval between point A and point B is C seconds".

The geometry of light has an affine nature - it doesn't have measurable "time intervals" at all. We can order A, B, and C, but we can't assign any meaningful numerical intervals to the "distance" between them.
 
  • #16
pervect said:
The geometry of light has an affine nature - it doesn't have measurable "time intervals" at all. We can order A, B, and C, but we can't assign any meaningful numerical intervals to the "distance" between them.

You've been a great help, but from the last paragraph I only understood that time doesn't have measurable time intervals! But why?
 
  • #17
eyad-996 said:
You've been a great help, but from the last paragraph I only understood that time doesn't have measurable time intervals! But why?

Suppose you have a nice standard plane polarized radio wave.

If you calculate the invariant time interval, also known as the "proper time" between any two points on the light wave according to relativity, the number you get will be zero.

However, any given observer can mark points along the wave at which the E-field is zero at any given time. And he'll find these points will be evenly spaced. This "even spacing" property happens in spite of the fact that all the proper time intervals are zero.

The distance from A to B, from A to C, and from B to C, measured using the invarinat interval, will all be zero. However, there is a unique point C such that AB and BC are "evenly spaced". This is the affine geometry of the light wave.

The exact spacing depends on the ight wave and the observer. One observer might see an AM radio wave with a 300 meter wavelength - a relativistically traveling observer might see it as much shorter, or longer, due to the doppler effect,
 
  • #18
So light takes time to reach between two points because I (the observer) can feel/ measure time differently from the Light ??
 
  • #19
That seems like a good way to put it. In your reference frame you are not moving at the speed of light, you experience time, and in your frame light takes time to go from A to B. And light doesn't have a reference frame of its own.
 
  • #20
Thank you all, you have been a great help.
Last post puts it straight and simple.
 
  • #21
the lorentz transformation is singular for the speed of light i.e. Not defined
 
  • #22
What about this answer:

The time dilation formula is according to http://en.wikipedia.org/wiki/Time_dilation

T‘ = T * sqrt (1-v2/c2).


Set v=c, the proper time of light T’ will always be 0. The lorentz transformation is not defined for the speed of light, but the time dilation formula above is.

However, time is not frozen, the proper life time of a photon is zero.
 
  • #23
Moonraker said:
What about this answer:

The time dilation formula is according to http://en.wikipedia.org/wiki/Time_dilation

T‘ = T * sqrt (1-v2/c2).


Set v=c, the proper time of light T’ will always be 0. The lorentz transformation is not defined for the speed of light, but the time dilation formula above is.

However, time is not frozen, the proper life time of a photon is zero.
Here's a thread you should read:

https://www.physicsforums.com/showthread.php?t=661429
 
Last edited:
  • #24
I don't think any of the previous posts have really addressed the basic misunderstanding invoved in the OP's question. The OP asked:

(1)
eyad-996 said:
If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

The question shows a more basic misunderstanding of frames of reference. Suppose the OP had asked instead:

(2) "If when you're moving close to the speed of light time freezes, why then does it take neutrinos 8 minutes to reach the Earth from the sun?"

The answer is that when we talk about the time taken for something to reach the Earth from the sun, we're implicitly talking about the time as measured in the frame of the earth. But relativistic time dilation would relate the 8 minutes to the much longer time taken in the frame of the neutrino.

A question that didn't involve this misconception would be:

(3) If when you're moving close to the speed of light time freezes, does that mean that only a very short time passes in the frame of a neutrino that, in the Earth's frane, takes 8 minutes to reach the earth?

The answer would be yes.
 
  • #25
Thanks, great answer!
 
  • #27
bcrowell said:
(3) If when you're moving close to the speed of light time freezes, does that mean that only a very short time passes in the frame of a neutrino that, in the Earth's frane, takes 8 minutes to reach the earth?

The answer would be yes.

I suppose that neutrino's speed in neutrino's frame is not higher than light speed because the distance sun-earth is diminishing in neutrino's frame as well? (according to Lorentz transformation)
 
  • #28
Moonraker said:
ghwellsjr said:
Hi ghwellsjr,
which one? are you (mistakenly?) referring to our current thread?
Moonraker
It was no mistake.

If you had read this thread you would have read this post:
pervect said:
You have some a notion of time, and you assume that light must have some sense of it too. And this idea is wrong.
So then why do you say:
Moonraker said:
However, time is not frozen, the proper life time of a photon is zero.
This is a wrong statement because time does not apply to a photon. It doesn't have a proper time or a life time or a proper life time or any other time. You shouldn't say that time for a photon is not frozen or frozen. You should say time doesn't apply to a photon which is different than saying that some kind of time of a photon is zero.
 
  • #29
ghwellsjr said:
This is a wrong statement because time does not apply to a photon. It doesn't have a proper time or a life time or a proper life time or any other time. You shouldn't say that time for a photon is not frozen or frozen. You should say time doesn't apply to a photon which is different than saying that some kind of time of a photon is zero.

I don’t agree. There is no doubt that each photon is sent and absorbed at a precise time.Temission and Tabsorption. Time applies to photons too. This is one of the very few things we know for sure about photons.
 
  • #30
Moonraker said:
I don’t agree. There is no doubt that each photon is sent and absorbed at a precise time.Temission and Tabsorption. Time applies to photons too.
These are not times measured from the (nonexistent) frame of a photon, they are measured from other quite ordinary frames of reference.
 
  • #31
Moonraker said:
I suppose that neutrino's speed in neutrino's frame is not higher than light speed because the distance sun-earth is diminishing in neutrino's frame as well? (according to Lorentz transformation)
The neutrinos speed in the neutrinos frame is 0.
 
  • #32
Doc Al said:
These are not times measured from the (nonexistent) frame of a photon, they are measured from other quite ordinary frames of reference.

No, the moment of emission is the same for the observer and for the photon.
At the absorption, the clock of the observer shows 8 minutes (Sun-Earth). The “clock” of the photon shows 0 seconds, according to the above-mentioned time dilation formula:
T‘ = T * sqrt (1-v2/c2),
even if the Lorentz transformation does not apply to photons.
 
  • #33
DaleSpam said:
The neutrinos speed in the neutrinos frame is 0.

This would mean that the distance is 0 as well in the neutrino's frame.
 
  • #34
Moonraker said:
No, the moment of emission is the same for the observer and for the photon.
At the absorption, the clock of the observer shows 8 minutes (Sun-Earth). The “clock” of the photon shows 0 seconds, according to the above-mentioned time dilation formula:
T‘ = T * sqrt (1-v2/c2),
even if the Lorentz transformation does not apply to photons.
You do realize that the time dilation formula is just a special case of the Lorentz transformation, don't you? So if the LT doesn't apply, neither does the time dilation formula.
 
  • #35
Moonraker said:
This would mean that the distance is 0 as well in the neutrino's frame.
The distance the neutrino travels is indeed 0 in the Neutrinos frame. Note that that is not the same as the distance between the Earth and the sun.
 
<h2>1. What is the theory behind the statement "when moving at the speed of light, time stops"?</h2><p>The theory behind this statement is based on Einstein's theory of relativity. According to this theory, time and space are relative to the observer's frame of reference. When an object is moving at the speed of light, time appears to stop for that object from the perspective of an outside observer.</p><h2>2. Is it possible for an object to actually move at the speed of light?</h2><p>No, it is not possible for an object with mass to reach the speed of light. According to Einstein's theory of relativity, as an object approaches the speed of light, its mass increases infinitely and would require an infinite amount of energy to continue accelerating.</p><h2>3. Does time completely stop for an object moving at the speed of light?</h2><p>No, time does not completely stop for an object moving at the speed of light. From the perspective of the object, time would appear to pass normally. It is only from the perspective of an outside observer that time would appear to stop for the object.</p><h2>4. How does this concept impact our understanding of time and space?</h2><p>This concept challenges our traditional understanding of time and space as absolute and fixed. It suggests that time and space are relative and can be affected by factors such as speed and gravity. This has significant implications for our understanding of the universe and the laws of physics.</p><h2>5. Are there any real-world applications of this concept?</h2><p>While it is not possible for objects with mass to reach the speed of light, this concept has been applied in the field of particle physics. The Large Hadron Collider, for example, accelerates particles to nearly the speed of light in order to study their behavior and properties. Understanding the effects of extreme speeds on time and space is also crucial for space travel and the development of future technologies.</p>

1. What is the theory behind the statement "when moving at the speed of light, time stops"?

The theory behind this statement is based on Einstein's theory of relativity. According to this theory, time and space are relative to the observer's frame of reference. When an object is moving at the speed of light, time appears to stop for that object from the perspective of an outside observer.

2. Is it possible for an object to actually move at the speed of light?

No, it is not possible for an object with mass to reach the speed of light. According to Einstein's theory of relativity, as an object approaches the speed of light, its mass increases infinitely and would require an infinite amount of energy to continue accelerating.

3. Does time completely stop for an object moving at the speed of light?

No, time does not completely stop for an object moving at the speed of light. From the perspective of the object, time would appear to pass normally. It is only from the perspective of an outside observer that time would appear to stop for the object.

4. How does this concept impact our understanding of time and space?

This concept challenges our traditional understanding of time and space as absolute and fixed. It suggests that time and space are relative and can be affected by factors such as speed and gravity. This has significant implications for our understanding of the universe and the laws of physics.

5. Are there any real-world applications of this concept?

While it is not possible for objects with mass to reach the speed of light, this concept has been applied in the field of particle physics. The Large Hadron Collider, for example, accelerates particles to nearly the speed of light in order to study their behavior and properties. Understanding the effects of extreme speeds on time and space is also crucial for space travel and the development of future technologies.

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