Light from stars really from billions of years ago?

[Wiploc]

Photons travel at c, and therefore experience no time, and no distance.

People keep saying that, but I don't understand why.

Maybe they say it because understand relativity and time dilation. t = t₀/(1-v²/c²)^1/2.

In that equation, I understand only the equal sign.

Then again, if they don't understand relativistic time dilation, maybe they are just repeating what they heard someone who does understand it has said.

As I said, I don't understand. So I'm not trying to argue with you. I'm taking a position as an invitation to correction. I'll try to state my mathematically ignorant layman's position clearly, in the hope that you, or someone, will be able to see and correct my error.

Joe and Sara are twins. Sara gets on the rocket and blasts off for Alpha Centauri.

I don't understand t = t₀/(1-v²/c²)^1/2, but I assume it lets us calculate how much Joe's speed slows down (as viewed by Sara) and how much Sara's speed slows down (as viewed by Joe).

Those parentheses aren't intended to trivialize. Sara's time really does run slow for Joe, and Joe's time really does run slow for Sara. But Sara's time never runs slow for Sara, and Joe's speed never runs slow for Joe.

The faster Joe goes (relative to Sara), the slower he sees Sara's time go, until, as he approaches the speed of light, her time (from his point of view) approaches being stopped. But her time never even begins to slow down for her.

If we extrapolate, if we say, "Sara's time would stop if she got all the way to c," we're saying that Sara's time would stop for Joe. And Joe's time would stop for Sara. But their own time never even begins to slow down for either of them.

If Sara were to go the speed of light, her watch would (by Joe's reckoning) stop ticking altogether. But her trip would take over four years according to Joe. And it would take the same length of time according to Sara, because, for Sara, it is Joe's watch that has stopped ticking.

Her own time hasn't slowed down for her.

And the little photons traveling beside her, their watches haven't stopped either. So the trip takes just as long for them as it does for her.

-

So, if I'm wrong, I hope someone can shed light on where my mistake is.

 

[Shadowy Man]

You’re missing length contraction in the mover’s frame. Even if in your own frame the time doesn’t slow, it appears to you that the distance you need to travel is shorter.

This is exhibited nicely by muons created in showers when high energy cosmic particles hit the atmosphere. They seem to travel much farther than they should given their speed and decay lifetime. From our frame their clocks seem slow, from their frame the distance they travel is shortened.

 

[Bomb#20]

Photons don't need to be conscious for us to understand that they exist for zero time in their own reference frame, and that as a result it is incoherent to describe any event for a photon as 'delayed'. A photon is emitted by a distant quasar, and absorbed by whatever detector you are using, simultaneously in the photon's reference frame. In your reference frame, these events are separated by many billions of light years of space, and many billions of years of time, but that's irrelevant - neither frame is preferred, both are correct and mathematically equivalent, according to the rules of general relativity as set out by Einstein, Lorentz, and others. You can do all your calculations in whichever frame makes them easiest, or in whatever frame takes your fancy, and then convert to any other frame to see how the same circumstances would appear to an observer in that other frame.

I don't think that's correct. A photon doesn't have a reference frame. There's no way you could do all your calculations about your own movements from the point of view of the photon and then convert to some real observer's frame. If you tried, the Lorentz transformation would just give you a bunch of divide-by-zeros.

 

[skepticalbip]

Maybe they say it because understand relativity and time dilation. t = t₀/(1-v²/c²)^1/2.

In that equation, I understand only the equal sign.

... snip ...

You seem to be asking for a "hand waving" explanation avoiding any mathematic concepts for a subject that relies heavily on an understanding of basic mathematics. In particular you seem to be wanting a solution for what has been called the "twin paradox" and again with no math references.

I'm a bit doubtful that a good explanation can be given of this subject and a good understanding received under those conditions. But the twin paradox isn't really a paradox for someone willing to engage in some very basic math... even though I think it would be a bit long to try for an internet discussion board.

Just in case you would like to see an explanation (though using a bit of math), I just did a google search and found a youtube video that did explain why the "twin paradox" isn't a paradox and why the stay on Earth twin aged more.




ETA:
I might add that what you now seem to be asking for is far afield from your original question of why people say that no time passes for a photon.

 

[excreationist]

I think that to connect Copenhagen interpretation with Shrodinger's thought experiment is incorrect. For example, the many-worlds interpretation also says that the cat is in a superposition of dead and alive.

Actually DBT's link
https://landing.newscientist.com/department-for-education-feature-3/
talks about this:

 

[excreationist]

A guy from reddit:

There's no standard Copenhagen.

Say if you think that wave particle duality is undecided all the way until measurement, then you have no retrocausality. The problem with this picture for some people is that there's no reality underneath.

If you think that there's reality (the light was either a wave or particle, never undecided), say if detected as particle, it means the light only took one path even all the way back there billions of years, then it seems to imply that assigning reality to quantum things forces one to adopt retrocasuality.

But then this is not a universal conclusion. One can look at the pilot wave picture. There's both wave and particle. The particle guided by the wave can reproduce the experiment without any need for retrocausality, although the wave guide acts faster than light.

So it seems with the Copenhagen interpretation if photons are always particles or waves, then at the quasar they started as particles or waves billions of years before the experiment...

 

[steve_bank]

The answer is photons is a word we use to describe particles that as part of theory is able to predict results, that is all.

The map is not the countryside. What we call scince is models for reality we observe, not reality 9itself.

To me it is likely what we label photon is actually a reality we can fullyl discern and may never will. That is what the wave particle duality says. We are limited by our instrumentalom.

The wave label is a convienient metaphor. As is particle.

 

[excreationist]

My eventual post:

https://www.youtube.com/watch?v=0ui9ovrQuKE
.......This is called a delayed choice because the observer’s choice of selecting how to measure the particle is being done billions of years from the time that the particle left the quasar. So presumably the light would have to be committed to either being a particle or wave, billions of years before the measurement is actually made here on earth.​

But if this is a simulation the thought experiment can be explained - the observer would choose how to measure the light causing it to be detected as particles or waves. The light from the quasar could be generated instantly but give the impression that it was from billions of years ago as either particles or waves.

Note that if we assume a version of the popular Copenhagen interpretation where light always acts like either a particle or a wave then the light became particle-like or wave-like billions of years before the measurement.

Though there are quantum mechanics interpretations that don't require retrocausality (the future affecting the past).

BTW a related thing is the delayed choice quantum eraser. PBS Space Time says that it could involve retrocausality... it gives a thought experiment about sending the winning lottery numbers back in time. This is their explanation about why it wouldn't give useful results:
https://www.youtube.com/watch?t=239&v=MuvwcsfXIIo&feature=youtu.be

 

[steve_bank]

Schrodinger posed his cat live or dead until observed question to show how absurdly quantum physics can be interpreted.

 

[Jayjay]

Schrodinger posed his cat live or dead until observed question to show how absurdly quantum physics can be interpreted.

That may have been his goal, but unfortunately nature really is that absurd.

 

[steve_bank]

Schrodinger posed his cat live or dead until observed question to show how absurdly quantum physics can be interpreted.

That may have been his goal, but unfortunately nature really is that absurd.

For us atheists who ascribe to naturalism nature is what it is. It is the human brain that allows humans to see what is natural as absurd.

Imterpretaion is metaphysics, philosophy, and religion. Since the 60s people have put a spin on physics. The Tao Of Physics, the Dancing Wu Li Masters.

I listen Coast To Coast AM on the radio for entertainment. A daily stream of real science mixed with the supernatural and mysterious.

Chopra Depak performs spell spinning talks mixing physics and mysticism.

 

[skepticalbip]

^ ^ ^
True...
Schrodinger wrote his equations to describe the probability of finding a particle in any particular position... It was a probability distribution or a curve that predicted the probability of finding the particle at any specific point under the curve.

Bohr interpreted Schrodinger's equation to mean that the particle was physically distributed so in superposition or in all places (or everywhere allowed) under the curve at the same time... and only decides on one place when we make a measurement.

There is no dispute that Schrodinger's equations are damned useful in QM. The dispute is in the interpretation. Schrodinger who figured out the equation disagrees with Bohr's interpretation. So did Einstein.

 

[bilby]

^ ^ ^
True...
Schrodinger wrote his equations to describe the probability of finding a particle in any particular position... It was a probability distribution or a curve that predicted the probability of finding the particle at any specific point under the curve.

Bohr interpreted Schrodinger's equation to mean that the particle was physically distributed so in superposition or in all places (or everywhere allowed) under the curve at the same time... and only decides on one place when we make a measurement.

There is no dispute that Schrodinger's equations are damned useful in QM. The dispute is in the interpretation. Schrodinger who figured out the equation disagrees with Bohr's interpretation. So did Einstein.

Maybe, but neither Schrödinger nor Einstein were gifted a house next door to a brewery with a supply of free beer. So how smart can they really have been?

 

[skepticalbip]

^ ^ ^
True...
Schrodinger wrote his equations to describe the probability of finding a particle in any particular position... It was a probability distribution or a curve that predicted the probability of finding the particle at any specific point under the curve.

Bohr interpreted Schrodinger's equation to mean that the particle was physically distributed so in superposition or in all places (or everywhere allowed) under the curve at the same time... and only decides on one place when we make a measurement.

There is no dispute that Schrodinger's equations are damned useful in QM. The dispute is in the interpretation. Schrodinger who figured out the equation disagrees with Bohr's interpretation. So did Einstein.

Maybe, but neither Schrödinger nor Einstein were gifted a house next door to a brewery with a supply of free beer. So how smart can they really have been?

It could be that the unlimited supply of free bear might have played some part in his interpretation.

 

[bilby]

^ ^ ^
True...
Schrodinger wrote his equations to describe the probability of finding a particle in any particular position... It was a probability distribution or a curve that predicted the probability of finding the particle at any specific point under the curve.

Bohr interpreted Schrodinger's equation to mean that the particle was physically distributed so in superposition or in all places (or everywhere allowed) under the curve at the same time... and only decides on one place when we make a measurement.

There is no dispute that Schrodinger's equations are damned useful in QM. The dispute is in the interpretation. Schrodinger who figured out the equation disagrees with Bohr's interpretation. So did Einstein.

Maybe, but neither Schrödinger nor Einstein were gifted a house next door to a brewery with a supply of free beer. So how smart can they really have been?

It could be that the unlimited supply of free bear might have played some part in his interpretation.

I guess that depends on whether they were grizzly, brown, polar, or grizzly.

 

[fromderinside]

So how does one orient the grizzly, brown, polar, and grizzly dimensions of grizzly if you don't mind my being grizzly grizzly.

 

[steve_bank]

Flip a coin in a dark room. At any point in time position has any number of probabilities. A wave equation would predict the probability of coin being a in position if the light is flashed on and off.

When the coin comes to rest on the floor the wave function has collapse into a measurable state.

In principle not that complicated.

BTW, from a bio I read Einstein was a party animal of his day. He played a violin. He enjoyed eating, drinking, and smoking with his peers. He was hardly the stereotypical academic.

 

[Shadowy Man]

Flip a coin in a dark room. At any point in time position has any number of probabilities. A wave equation would predict the probability of coin being a in position if the light is flashed on and off.

When the coin comes to rest on the floor the wave function has collapse into a measurable state.

In principle not that complicated.

BTW, from a bio I read Einstein was a party animal of his day. He played a violin. He enjoyed eating, drinking, and smoking with his peers. He was hardly the stereotypical academic.

Having been in academia for a decent chunk of my life I can say that the vast majority of academics eat, drink, and party with their peers. Some even smoke. Many play instruments. I don’t know what the stereotype is but the implication doesn’t seem to fit with my observations.

 

[excreationist]

Flip a coin in a dark room. At any point in time position has any number of probabilities. A wave equation would predict the probability of coin being a in position if the light is flashed on and off.

When the coin comes to rest on the floor the wave function has collapse into a measurable state.

In principle not that complicated.

Can coins also become entangled?

 

[Shadowy Man]

Flip a coin in a dark room. At any point in time position has any number of probabilities. A wave equation would predict the probability of coin being a in position if the light is flashed on and off.

When the coin comes to rest on the floor the wave function has collapse into a measurable state.

In principle not that complicated.

Can coins also become entangled?

No. The coherence at the microscopic level breaks down for macroscopic objects.