# The Naked Scientists Forum

### Author Topic: How much time has passed for a photon during the 8 minutes travel to Earth?  (Read 2246 times)

#### kasparovitch

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##### How much time has passed for a photon during the 8 minutes travel to Earth?
« on: 19/06/2016 12:28:28 »
Once at the speed of light time passes very much faster than at a slower speed:

One photon that leaves the sun now, how much time did pass for the photon, when at our time it reaches the Earth 8 minutes later?

[xx(]
« Last Edit: 20/06/2016 10:44:55 by chris »

#### IAMREALITY

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##### Re: Sun photon time when it reaches Earth
« Reply #1 on: 19/06/2016 17:09:54 »
Actually time would be slower...

But even beyond that, photons actually experience no time at all!

#### kasparovitch

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##### Re: Sun photon time when it reaches Earth
« Reply #2 on: 19/06/2016 23:35:38 »
Sure photons don't actually experience time. Only people capable of computing it.

But if you can put a stone traveling at the speed of light it will advance in time in relation to a stone at rest, even if none experience time.

My question is how much time will the photon advance in the 8 minutes.

What do you mean time would be slower?

#### IAMREALITY

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##### Re: Sun photon time when it reaches Earth
« Reply #3 on: 19/06/2016 23:53:24 »
Sure photons don't actually experience time. Only people capable of computing it.

But if you can put a stone traveling at the speed of light it will advance in time in relation to a stone at rest, even if none experience time.

My question is how much time will the photon advance in the 8 minutes.

What do you mean time would be slower?

The higher the gravity, the faster the speed, the slower time advances. That's why the observer in normal gravity at rest can age thousands of years in what would be minutes for the person standing at the event horizon of a black hole.  Time goes slower for them relative to the observer at rest at normal gravity.  In the time it took thousands of years to go by, only minutes or hours or days went by for that at the black hole.  Time was slower for them.

#### kasparovitch

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##### Re: Sun photon time when it reaches Earth
« Reply #4 on: 20/06/2016 00:12:45 »
Thx IAMREALITY I get it.

#### kasparovitch

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##### Re: Sun photon time when it reaches Earth
« Reply #5 on: 20/06/2016 08:58:33 »
I'm afraid this topic is not about the epistemology of any theory.

I ask a concrete question which assumes the theories concerned are hypothetically correct.

If you think they aren't or that they need fine tuning, I think you should discuss it in a topic about that subject, or create it.

#### Colin2B

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##### Re: Sun photon time when it reaches Earth
« Reply #6 on: 20/06/2016 10:28:39 »
Sure photons don't actually experience time. Only people capable of computing it.

But if you can put a stone traveling at the speed of light it will advance in time in relation to a stone at rest, even if none experience time.

My question is how much time will the photon advance in the 8 minutes.

What do you mean time would be slower?
If we replace stone or photon with clock in your question, then from the travelling clock's perspective it will tick at the same rate it would when at rest. However, an observer seeing it travel at near light speed would say it is ticking more slowly.
Also, from the perspective of the clock the distance between sun and earth is shorter so although its tick rate is the same it has less distance to travel. As it approaches the speed of light that distance approaches 0, so you might conclude that the photon travels 0 distance and so experiences 0 travel time from its own perspective.
Whether that is useful from a physics point of view I don't know.

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#### Alan McDougall

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #7 on: 20/06/2016 11:06:29 »
A photon has zero mass so it would take 8 minutes to travel from the sun to the earth.

A large gravity field between the earth and the sun might effect the time taken to a minuscule degree.

Light can have momentum but not mass?
« Last Edit: 20/06/2016 11:13:36 by Alan McDougall »

#### hamdani yusuf

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #8 on: 20/06/2016 13:25:27 »
The higher the gravity, the faster the speed, the slower time advances. That's why the observer in normal gravity at rest can age thousands of years in what would be minutes for the person standing at the event horizon of a black hole.  Time goes slower for them relative to the observer at rest at normal gravity.  In the time it took thousands of years to go by, only minutes or hours or days went by for that at the black hole.  Time was slower for them.
Imagine a satellite orbiting a black hole near event horizon. To get stable orbital trajectory, it has to move at nearly the light speed.
But it will make it experience micro gravity, considering what happens to people in ISS.
The question is, what cause time dilation of a clock inside the satellite, is it the gravity field, the movement speed, or both? (or none?)
What if the satellite is not moving relative to the black hole nor an external observer, by canceling force of gravity using some kind of propeller?

#### IAMREALITY

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #9 on: 20/06/2016 16:07:03 »
A photon has zero mass so it would take 8 minutes to travel from the sun to the earth.

A large gravity field between the earth and the sun might effect the time taken to a minuscule degree.

Light can have momentum but not mass?

I believe the OP is talking about the time dilation the photon would experience from its own perspective, not simply a question of "how long does it take light from the sun to reach earth?".  I base that off the very questions he asked in the OP and how he stated them.

And at its most basic, that photon would experience having crossed no distance, and it would've experienced no passing of time.  From the photon's perspective, the journey was actually instantaneous.

#### Alan McDougall

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #10 on: 20/06/2016 16:12:54 »
A photon has zero mass so it would take 8 minutes to travel from the sun to the earth.

A large gravity field between the earth and the sun might effect the time taken to a minuscule degree.

Light can have momentum but not mass?

I believe the OP is talking about the time dilation the photon would experience from its own perspective, not simply a question of "how long does it take light from the sun to reach earth?".  I base that off the very questions he asked in the OP and how he stated them.

And at its most basic, that photon would experience having crossed no distance, and it would've experienced no passing of time.  From the photon's perspective, the journey was actually instantaneous.

You are correct, time is meaningless from a photons perceptive!

#### IAMREALITY

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #11 on: 20/06/2016 16:29:37 »
The higher the gravity, the faster the speed, the slower time advances. That's why the observer in normal gravity at rest can age thousands of years in what would be minutes for the person standing at the event horizon of a black hole.  Time goes slower for them relative to the observer at rest at normal gravity.  In the time it took thousands of years to go by, only minutes or hours or days went by for that at the black hole.  Time was slower for them.
Imagine a satellite orbiting a black hole near event horizon. To get stable orbital trajectory, it has to move at nearly the light speed.
But it will make it experience micro gravity, considering what happens to people in ISS.
The question is, what cause time dilation of a clock inside the satellite, is it the gravity field, the movement speed, or both? (or none?)
What if the satellite is not moving relative to the black hole nor an external observer, by canceling force of gravity using some kind of propeller?

I'm not sure if I'm fully grasping the question correctly, but I would think that any factor contributing to the energy/momentum of the system in question would be responsible for its relative time dilation (if I'm saying that all correctly).

#### PmbPhy

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #12 on: 20/06/2016 21:07:30 »
Once at the speed of light time passes very much faster than at a slower speed:

One photon that leaves the sun now, how much time did pass for the photon, when at our time it reaches the Earth 8 minutes later?

[xx(]
It's not meaningful to speak of the time passing for a photon so your question has no meaningful answer

Quote from: timey
That time runs slower for a black hole is purely conjecture.
Nothing could be further from the truth. Conjecture is an opinion or conclusion formed on the basis of incomplete information. Nothing could be further from the truth for black holes. That time slows down in a gravitational field is something that's been measured by experiment at Harvard University in 1906 by Pound and Rebka. GR is based on solid observation/experimentation and is a well verified theory. Black holes have been detected and that time slows down more and more the closer one gets to the event horizon is based on solid theoretical predictions based on verified theory. The gravitational field outside a black hole is just a strong gravitational field and we know how time behaves in a gravitational field.

Layman all too often use the term conjecture or speculation when speaking of things which are based on solid, tested and therefore accepted and trusted theory. I advise learning the meaning of each of those terms so you know when each applies.

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#### kasparovitch

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #13 on: 20/06/2016 22:13:42 »
Once at the speed of light time passes very much faster than at a slower speed:

One photon that leaves the sun now, how much time did pass for the photon, when at our time it reaches the Earth 8 minutes later?

[xx(]
It's not meaningful to speak of the time passing for a photon so your question has no meaningful answer

I'm not sure what you mean by time passing for a photon.

Is it the same as IAMREALITY when he told that photons don't experience time?

Using the formula for time dilation and assuming a solar photon travels at 99.9999% of light speed, a photon leaving the sun at this moment and reaching the Earth 8 minutes later in rest time would have lasted 3 years in its time to reach Earth.

But the instant it leaves the Sun and the instant it touches Earth must be 8 minutes before and 8 minutes later in rest time and those must be coincidental with the photon's time.

If someone could travel at that speed for 8 minutes would advance 3 years in time. The solar photon is used as an illustration.

This is paradoxical in that a photon leaving now the sun would touch Earth later than 2019...

#### kasparovitch

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #14 on: 21/06/2016 00:17:49 »
I'm sorry Colin.  There 'is' no New Theory here...  Just General Relativity concerning what is proven and what is not...  If we can't talk about what is proven and what is not concerning General Relativity, this then renders the physics board as a farce and General Relativity as a 'religion'.

PREVIOUS POST OF MINE:

I'm afraid this topic is not about the epistemology of any theory.

I ask a concrete question which assumes the theories concerned are hypothetically correct.

If you think they aren't or that they need fine tuning, I think you should discuss it in a topic about that subject, or create it.

Assuming a theory is hypothetically correct for the sake of discussion is neither farce nor religion, I think.

Once again, if you have something to add to the theory itself, or subtract from it, do it elsewhere in the forum.

#### Thebox

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##### Re: Sun photon time when it reaches Earth
« Reply #15 on: 21/06/2016 11:30:15 »
However, an observer seeing it travel at near light speed would say it is ticking more slowly.

Interesting Colin, the observer does not see it to begin with, the observer only receives wave packets of information that forms a subjective picture in the sight cortex that is situated in the back of your head.   The observer does not see anything travelling , they only see subjective pictures in the mind .

You don't see an object being displaced, you ''see'' the amount of time it takes photons to reach your eyes displaced in space-time.

#### Thebox

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #16 on: 21/06/2016 11:38:27 »
Once at the speed of light time passes very much faster than at a slower speed:

One photon that leaves the sun now, how much time did pass for the photon, when at our time it reaches the Earth 8 minutes later?

[xx(]

I understand your question, you are mixing subjective and objective together to form your question, try to relate to this and re-phrase your question.

#### Thebox

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##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #17 on: 21/06/2016 11:40:57 »
A photon has zero mass so it would take 8 minutes to travel from the sun to the earth.

A large gravity field between the earth and the sun might effect the time taken to a minuscule degree.

Light can have momentum but not mass?

Photons have momentum (p), light is a generalised term. Photons are mass-less particles that have a net charge of 0 but have energy hf.

h is the Plank constant and the potential energy a photon contains.

« Last Edit: 21/06/2016 11:43:44 by Thebox »

#### The Naked Scientists Forum

##### Re: How much time has passed for a photon during the 8 minutes travel to Earth?
« Reply #17 on: 21/06/2016 11:40:57 »