Photons have no time

[CraigD]

Consider the statement that a photon is everywhere at once. I read that in one of the earlier posts. Now I don't know about you, but that doesn't seem likely in my world view. If it were true, then all photons are essentially in the same place at the same time all the time.

I’ve encountered this confusion on many previous occasions.

 

Quantum mechanics does not state that “a photon is everywhere at once”. It states that the probability of a specific photon being measured in a particular volume of space at a specific time, is non-zero for every non-zero volume of space. It does not state that the probability of every photon being in a particular volume of space is the same.

 

On the scales at which we ordinarily measure photons – with eyes, cameras, etc. – quantum mechanics predicts that the probability of photons being within a volume centered on the point that classical mechanics predicts a body representing the photon to be is very close to, but slightly less than, 1.

It is much more likely that something is seriously wrong with at least one of the concepts in the discussion. Basically, the ship is sinking.

This statement is too metaphorical for me to make much sense of. I believe I share the sentiment expressed by kalias_knight in:

Exactly what is the point that you are trying to make ?? Please be more specific ...

Idsoftwaresteve seems to be implying that the “sinking ship” is quantum mechanics, or perhaps mathematical physics as a whole. My impression, however, is that, if any metaphorical ship is sinking, it is the principle that which is not intuitive, or easy to understand without the use of difficult math, must be wrong. This ship, I believe, has never floated.

[Pluto]

Hi

 

I'm trying to understand: What do you mean that photons have no time?.

 

If photons have a speed or velocity than they are locked into a reference point in time.

[Boerseun]

Hi

 

I'm trying to understand: What do you mean that photons have no time?.

 

If photons have a speed or velocity than they are locked into a reference point in time.

Well, basically it boils down to time slowing down as velocity increases, with time not being experienced at all at the speed of light. No massive object can reach this velocity, so the point is moot. But if you were massless, and somehow riding a photon travelling at the speed of light, you won't experience any time passing at all.

 

So, in a nutshell, a for a photon emitted at the Big Bang, the beginning and the end (whatever and whenever that might be) of the universe will be the exact same moment, with no inkling of the billions of years that passed in between the two events.

[CraigD]

I'm trying to understand: What do you mean that photons have no time?

As this is the essential question of this thread, it’s good of Pluto to ask it again. Answering it very precisely is, I think, critical.

Well, basically it boils down to time slowing down as velocity increases, with time not being experienced at all at the speed of light. No massive object can reach this velocity, so the point is moot. But if you were massless, and somehow riding a photon travelling at the speed of light, you won't experience any time passing at all.

This is not quite correct. According to the theory of special relativity, if an observer (A) who can measure time (via clock A) appears to an observer (B) who can also measure time (via clock B) to have a speed of exactly the speed of light in vacuum ©, B will observe clock A to be unchanging, and A will observe B to be unchanging. B will observe clock B to be telling time as usual, and A will observe clock A to be telling time as usual.

 

So, neither observer will “not experience any time passing”, rather both will observe that the other is “frozen”. Each will observe other weirdness about the other:

• that their size is contracted to length zero in the direction of their motion;
• emitted/reflected photons – the usual way things are observed will, for different positions, be extremely frequency shifted;
• and, absurdly, if either A or B had non-zero rest mass, the other will have measured their mass to be infinite. What an observed infinite mass implies is profoundly weird – one reasonable possibility is that it will collapse the whole observed universe, including the observer, into something like a universe-sized black hole.

All of this weirdness is enough to lead one to suspect there’s something fundamentally weird, and possibly wrong, with the question as interpreted, or with special relativity in the extreme case the question poses.

 

:eek_big: The real fun comes when you consider what happens if B can, at some time non-zero time [math]t_B[/math] (assuming that, at the beginning of the experiment, both clock read 0) according to clock B, change his speed to zero relative to A. Assuming that both observer correctly compensate for the travel time of light or whatever signal passes between them to make these observations, what time [math]t_A[/math] will B now observe on clock A, and A on clock B?

 

The answer, as predicted by special relativity, is that A will observe [math]t_B=0[/math], and B will observe [math]t_A= \infty[/math] (A math purist might argue that, rather than infinity, [math]t_A[/math] should be undefined). There are great problems with this prediction: it’s a given that [math]t_B \gt 0[/math], contradicting A’s observation; how is it even possible for a clock to read “[math]\infty[/math]” or “undefined”?

 

This thread’s question, and similar ones, suggest such fun and weird answers, I’ve dedicated large chunks of contemplation to them, one of the results of which I relate in a bit of creative writing in the post ”A Math Student’s Campfire Tale About Time”.

[Pluto]

Hi Boreseum

 

You said

 

Well, basically it boils down to time slowing down as velocity increases, with time not being experienced at all at the speed of light. No massive object can reach this velocity, so the point is moot. But if you were massless, and somehow riding a photon travelling at the speed of light, you won't experience any time passing at all.

 

So, in a nutshell, a for a photon emitted at the Big Bang, the beginning and the end (whatever and whenever that might be) of the universe will be the exact same moment, with no inkling of the billions of years that passed in between the two events.

 

In a nutshell you are completly wrong. On both counts. You are assuming that the BBT is correct, its only a theory with many problems supported by ad hoc ideas.

 

Time itself is a word that cannot be changed or altered. We cannot go into the future or into the past. We can look at old light and see the images of the past, but not of the future.

 

So! if photons are leaving Earth at the speed of light, and if there was a clock on it. The clock will alays read the same time. Or is there a mathematical formula that can give us time reading.

 

Craigs explanation is great.

[jackson33]

using the theory that time slows with speed and is stopped at C velocity, then no time could pass under that thought. yes that clock would read the same on that photon, for ever as that energy wave will never age.

 

what your probably thinking is that mass will show age in its continuously moving through space even at C if possible. here i would agree with you and that if you held this speed for ten years, you in fact would be ten years older.

 

since i don't want to see a bunch of nasty post, let me explain theory. when a principle, notion or hypothesis is accepted by the scientific community, its classified as that...accepted theory or much as what the scientific law used to mean. BBT, has such status in the scientific world today in that community.

 

i have problems with many of the accepted theory, such as the above relativity, the BB, gravity in total but have to admit, much is already accepted by those who teach and practice science.

 

i might question Mr. B, by asking if a wave has the same effect or that the wave seen from 10-12 or 14 billion years ago is not the same one was emitted...i might even suggest that looking into the night sky with the unaided eye at a star (actually a distant galaxy) that the appearance of light are from millions of sources in or near that star like object, maybe up to 186,200 different such objects each second. this is IMO and understood to be speculative.

[Boerseun]

In a nutshell you are completly wrong. On both counts. You are assuming that the BBT is correct, its only a theory with many problems supported by ad hoc ideas.

You have missed the point with at least a few astronomical units, at least.

I'm not defending the Big Bang, I was using the two most distant (in time) points under modern cosmology to illustrate that photons don't experience time. If it'll make you feel better, let's make another analogy:

 

A photon emitted from the Sun and then absorbed by Pluto's eyeballs has no inkling of the 8 minutes that passed between the two events (as measured from Earth).

 

Happy now?

Time itself is a word that cannot be changed or altered. We cannot go into the future or into the past. We can look at old light and see the images of the past, but not of the future.

That's patently untrue. We are travelling into the future, at the speed of 1 hour per hour.

 

But enough nitpicking now.

 

We cannot change time, that's true. But time is a property that is bound to your frame of reference, and will differ when compared between two frames moving at different velocities to each other. Two similar clocks, being synchronised, will measure different times when they have been moving in seperate frames at seperate speeds and then eventually be brought back together again. As your velocity increases, time slows down. Not for you, of course, because everything in your frame will be measured as if everything is normal. But looking outside your fancy fast-flying spaceship's cockpit, you'll see the universe age much faster than what you're used to. If you can accellerate at 1g, the speed that you're comfortable with on Earth, you'll reach the edge of the known universe in slightly more than 52 years. As far as you can tell. For anybody on Earth, it would have taken you more than 15 billion years. Time is not cast in stone, time is relative to the observer.

So! if photons are leaving Earth at the speed of light, and if there was a clock on it. The clock will alays read the same time. Or is there a mathematical formula that can give us time reading.

For someone watching to clock zoom past at the speed of light, the clock would stand still. For the observer 'riding' the lightbeam, the clock would tick as normal - but time 'outside' his frame of reference would seem to have sped up so much that the intervening period between any two possible events will be infinitely small, i.e. unmeasurable. Which means if this photon was transmitted at the moment of the Big Bang* , and the photon travels through space until the very end of the Universe, whatever or whenever that might be*, the intervening time (for the photon) will be completely and utterly unmeasurable. The photon will not be aware of it. A photon is massless, and travels at c. At c, time stops. Time is not an object, event, dimension or concept that's appliccable to photons. Photons exist without 'knowing' about it. In order to be aware of your own existence takes time. Photons are emitted and absorbed in what appears to them as the same instant, regardless of how many billions of years it took them, as far as an external observer is concerned.

Craigs explanation is great.[/unquote]

What craig said, is exactly what I said (although he prolly won't agree with that).

As speeds approach c, length contraction (in the direction of travel) contracts, and once again, the observer travelling at close to c won't know about it. Travelling at c, that dimension dissappears altogether. It can be said that a photon is a two-dimensional expression of energy, because it travels at c, the dimension in the direction it's travelling (as observed by us), simply doesn't exist. It doesn't experience travel in the direction it's travelling in, because that dimension does not exist. It has been infinitely contracted. The analogies of "as we approach c" and "as we keep on adding speed" all falls flat at c itself. Photons can get there, because they're massles.

 

For all we know, we can be travelling at the speed of light through some as-yet unknown dimension without knowing it. There would be no way testing for it. The Big Bang* would be when you lifted your coffee cup, and the End of the Universe* will be by the time you took your first sip. Because you experiece three physical dimensions, you can't test for a fourth, or what your velocity through that particular dimension would be.

 

*Including the concept of the Big Bang in this instance is solely to illustrate an analogy. By no means am I implying the truth to the Big Bang, or saying anything about the end of the Universe, if or when it might happen at all. Although, of course, explaining the Hubble flow in any other way will take some serious hypothesizing from Big Bang deniers, which, for some reason not known to me, they fail to do. Saying "The Big Bang Sucks Balls" is not enough. Come with an alternative hypothesis, then we can talk. But brush up on some GR as well, so you can get an idea about the relativity of time as measured by different observers. But I digress. This is a disclaimer. So if you're allergic to shellfish, don't read this post. This post is to be read three times per day after eating. Children under 10 should read it once a day after dinner. Do not read this post for more than ten days without consulting your physician. Overdosing on this post have been known to result in hair loss and ecxzyma. On overdosing, induce vomitting by putting index finger in throat and other hand's index finger up anus. Upon failure to vomit, switch hands.

This post might cause excessive flatulence.

[Qfwfq]

In a nutshell you are completly wrong. On both counts. You are assuming that the BBT is correct, its only a theory with many problems supported by ad hoc ideas.

Boerseun's argument, although put a bit loosely, is based on special relativity, Big Bang is not a necessary premise at all. Get your facts straight before so blithely stating that somebody is wrong.

[Mike C]

To All

 

I would like to clarify the meaning of time.

 

Time is just another word for 'motion or change'.

So anything that moves or changes has a 'time' component.

 

Photons move at the velocity of 'c' that is 300,000 kms per SECOND.

So light has a time component irregardless of any other physics or science.

My opinion.

 

NS

[Jay-qu]

In our reference frame photons experience time - I think the point of the thread is that from the point of view of a photon (if they can be said to have a point of view..) no time would pass.

[Mike C]

In our reference frame photons experience time - I think the point of the thread is that from the point of view of a photon (if they can be said to have a point of view..) no time would pass.

 

What you are saying here is an endorsement of Relativity that we cannot experience.

 

However, to use relativity here, we can say that the photon does experience time because everything within its view is moving in the opposite direction at the velocity of 'c'.

Since time is relative, than it would see this as 'time' passing by.

 

NS

[Boerseun]

What you are saying here is an endorsement of Relativity that we cannot experience.

'Course we can experience it. Atomic clocks put on airplanes clearly show different times after flying at varying speeds relative to each other. We regularly cater for the increase in mass at atomic colliders. Relativity is tested and proven. I'm sorry if you don't like it or agree to it, but I can't sell you a bikini if you don't know how to swim.

However, to use relativity here, we can say that the photon does experience time because everything within its view is moving in the opposite direction at the velocity of 'c'.

The photon will experience time as everything else does. But, from the photon's point of view, the moment it was released (say, as a normal photon from the sun) and the moment it was absorbed (when it struck your eyeball) will be the one and same moment. From your point of view, however, it would have taken about eight minutes. Basically, the universe would seem to age from birth to death in the same moment, as far as a photon released in the Big Bang is concerned. But the 'moment' would feel exactly as long to the photon as a 'moment' feels to you. I'm sorry if you don't get it.

Since time is relative, than it would see this as 'time' passing by.

No. It won't see it as 'time passing by'. Time dilates as you approach c. C can never be reached, so the closer you get the digits towards the speed of light, the more time dilates. But you'll never reach c seeing as you're mass. And at c, you'll reach infinite mass. At c itself, time comes to a complete stop. For massless particles, seeing as they're the only sonsabitches who can actually reach c. So, for light, it won't experience anything as 'time passing', because the moment its emitted and the moment its absorbed would be the same moment for a particle travelling at c. And that's regardless of whether its from the sun to Earth or from the sun to the end of the universe. Whether the distance is 100,000 miles or 100 billion light years, the time it took to travel that distance at c would be instantaneous from the photon's point of view. Once again, I'm sorry if you don't get it. The maths and experimental results, however, do check out.

[CraigD]

What you are saying here is an endorsement of Relativity that we cannot experience.

'Course we can experience it. Atomic clocks put on airplanes clearly show different times after flying at varying speeds relative to each other. We regularly cater for the increase in mass at atomic colliders.

To this list of data confirming the predictions of the theory of relativity, we should add our everyday experience with clocks on the 24+ Global Positioning System satellites. Odds are most of us have at one time or another used, been a passenger on a vehicle using, or benefited from data collected with the aid of GPS.

 

Due to the reduction in gravitational field strength, GPS satellites clock slightly faster than the Earth’s surface, while due to their velocity, they clock slightly slower, for a net effect of the satellites clocking about .000038 seconds slower a day, a lot by atomic clock and GPS standards. The effect is accounted for in the systems design.

 

Had the theory of relativity been unknown when the GPS was deployed, this effect would have been immediately noticed, necessitating compensate for it after deployment. In an alternate history, time dilation, not the invariant speed of light in a constant medium discovered in 1887 via the Michelson–Morley experiment, might have been the key evidence pointing to the need for the theory of relativity.

[snoopy]

I have to agree with

Jay-qu

on this one

 

He is the only one that seems to have right answer the rest of you are just going kinda off topic.

 

If you could ride on the back of a photon (I said IF) you would experience no time, time would effectively freeze for you until you hit something and then you get squished.

 

Not the safest form of travelling is it ?

:)

[Mike C]

Like I said on my last post, if you are riding on a photon and look about you, you will see the universe moving backward. This is reality since the universe moving backward is your relative instrument for measuring time.

 

NS

[CraigD]

However, to use relativity here, we can say that the photon does experience time because everything within its view is moving in the opposite direction at the velocity of 'c'.

Since time is relative, than it would see this as 'time' passing by.

Like I said on my last post, if you are riding on a photon and look about you, you will see the universe moving backward. This is reality since the universe moving backward is your relative instrument for measuring time.

This is a bizarre prediction. New Science, do you have some support for it based on known (to someone other than yourself) physics? Something involving formulas of some sort?

 

By this reasoning, it stands that as I walk down the street at a comfortable 2 m/s, perceiving the world moving “backwards” at -2 m/s. Are you predicting, New Science, that I’d see the hands of a clock on a passing building (in my neighborhood, that would be the ones on a church steeple) moving backwards/counter-clockwise? Or that I would if I was moving at c? Or slightly less than c?

 

The conventional “use of relativity” for this situation is to use the familiar and easily derived Lorentz factor in an equation like:

[math]\Delta t_0 = \Delta t \sqrt{1 – (\frac{v}{c})^2}[/math], where [math]\Delta t_0[/math] is the elapsed time the observer sees on a clock that is not moving along with him, [math]\Delta t[/math] is the ET he sees on a clock that is moving with him, and [math]v[/math] is his relative speed. When [math]v=c[/math], as in the case if you were “riding a photon” this equation evaluates to [math]\Delta t_0 = \Delta t \cdot 0[/math], which can be phrased “no matter how much time you see passing on you clock, no time appears to pass on the other clocks.” As mentioned previously in the thread, several other strange effects predicted by relativity render seeing time passing on other clocks practically impossible.

 

Relativity predicts that, as I walk down the street, I actually do see the church steeple clock running very slightly slower than my own watch – for every 60 seconds on my watch, I should see [math]60 \cdot \sqrt{1 – (\frac{2}{3 \times 10^8})^2} \, \mbox{s}[/math], about 59.9999999999999986 s on the steeple clock – a bit tricky, as it doesn’t even have a second hand, let alone a femto-second hand! :hihi:

[Mike C]

This is a bizarre prediction. New Science, do you have some support for it based on known (to someone other than yourself) physics? Something involving formulas of some sort?

 

By this reasoning, it stands that as I walk down the street at a comfortable 2 m/s, perceiving the world moving “backwards” at -2 m/s. Are you predicting, New Science, that I’d see the hands of a clock on a passing building (in my neighborhood, that would be the ones on a church steeple) moving backwards/counter-clockwise? Or that I would if I was moving at c? Or slightly less than c?

 

The conventional “use of relativity” for this situation is to use the familiar and easily derived Lorentz factor in an equation like:

[math]\Delta t_0 = \Delta t \sqrt{1 – (\frac{v}{c})^2}[/math], where [math]\Delta t_0[/math] is the elapsed time the observer sees on a clock that is not moving along with him, [math]\Delta t[/math] is the ET he sees on a clock that is moving with him, and [math]v[/math] is his relative speed. When [math]v=c[/math], as in the case if you were “riding a photon” this equation evaluates to [math]\Delta t_0 = \Delta t \cdot 0[/math], which can be phrased “no matter how much time you see passing on you clock, no time appears to pass on the other clocks.” As mentioned previously in the thread, several other strange effects predicted by relativity render seeing time passing on other clocks practically impossible.

 

Relativity predicts that, as I walk down the street, I actually do see the church steeple clock running very slightly slower than my own watch – for every 60 seconds on my watch, I should see [math]60 \cdot \sqrt{1 – (\frac{2}{3 \times 10^8})^2} \, \mbox{s}[/math], about 59.9999999999999986 s on the steeple clock – a bit tricky, as it doesn’t even have a second hand, let alone a femto-second hand! :hihi:

 

These thought experiments are a departure from reality IMO.

 

However, I do believe in a spiritual force that can INFLUENCE the physical. So these tiny corrections can be spiritually manipulated.

This may surprise you about what I write here, but my LIFE experiences have proven this to me.

 

So, I kinda ignore these deparures from our realistic environment and prefer to stick with the Earth, Moon and the Sun clocks as our standards.

The other trivialities are ignored by me,

Of course, I can accept the current 'cesium' clocks as the current standad.

What you cite above has no relavence to by brand of Cosmology.

 

I am a 'free thinker' and refuse to be regimented by the 'power' science establishment.

 

If Copernicus didn't correct the churches power science in the past, our modern science today would not exist.

We would still be accepting the 'geocentric' theory that the current BBU is based on with some major modifications.

 

NS