Light is never late, nor is it early, it arrives precisely when it means to.
wolframhydroxide@sh.itjust.works
on 25 Jan 01:15
collapse
Since an observer traveling through space at the speed of light experiences no time from the beginning of their journey until they decelerate (since their 4-velocity vector has non-zero values only in the 3 dimensions of space), photons don’t just arrive precisely when they mean to, from the moment they are emitted, they have already arrived.
qjkxbmwvz@startrek.website
on 24 Jan 16:22
collapse
Dispersion and nonlinearities would like to have a word ;)
mexicancartel@lemmy.dbzer0.com
on 26 Jan 14:00
collapse
But when you think about light’s speed in medium it seems like absorption and re emission which shifts light’s net velocity. The speed of light between the interaction is still c. That becomes obvious if you zoom into matter and find its mostly empty likr vaccum
qjkxbmwvz@startrek.website
on 26 Jan 16:38
collapse
No, that’s not really a useful way of modeling it for the case of light traveling through a linear medium.
The absorption/re-emission model implicitly localizes the photons, which is problematic — think about it in an uncertainty principle (or diffraction limit) picture: it implies that the momentum is highly uncertain, which means that the light would get absorbed but re-emitted in every direction, which doesn’t happen. So instead you can make arguments about it being a delocalized photon and being absorbed and re-emitted coherently across the material, but this isn’t really the same thing as the “ping pong balls stopping and starting again” model.
Another problem is to ask why the light doesn’t change color in a (linear) medium — because if it’s getting absorbed and re-emitted, and is not hitting a nice absorption line, why wouldn’t it change energy by exchanging with the environment/other degrees of freedom? (The answer is it does do this — it’s called Raman scattering, but that is generally a very weak effect.)
The absorption/emission picture does work for things like fluorescence. But Maxwell’s equations, the Schrödinger equation, QED — these are wave equations.
mexicancartel@lemmy.dbzer0.com
on 26 Jan 18:35
collapse
I wouldn’t say its a useful way, but if you think about it, everything is vaccum if you zoom enough. Also absorption can mean different things though so keep that aside and think of it as some interaction going on which in effect slows it down.
Now i looked up on youtube and this is what i meant (timestamp included). I was looking for 3b1b explaination but this one works too. It’s arguable if we can call it absorption or not, and what I said before might be ambiguous. But this guy explains it well
Edit: The 3b1b explaination is either in this video or in this one or maybe a combination of both
NaibofTabr@infosec.pub
on 24 Jan 2025 05:21
nextcollapse
Technically everything moves at c (the speed of light) through spacetime, all the time. Most objects that have mass spend the majority of their motion in the time part, and thus move relatively slowly in space. If an object moves fast in space (where fast is a significant fraction of c) then it moves noticeably slower in time because the total spacetime vector value is always c.
Photons, being massless, do not move through time at all, and move through space at c.
remotelove@lemmy.ca
on 24 Jan 2025 05:45
nextcollapse
That’ll break a few brains. To elaborate with an example: From the perspective of a photon, it’s “life” is over as soon as it begins. Even though it takes about 8 mins for a photon to travel from the sun to the earth from our perspective, no time at all has passed for it.
(Correct me if I misspoke.)
midribbon_action@lemmy.blahaj.zone
on 25 Jan 02:18
collapse
Light is generally better modeled by a wave, so I would say the wave doesn’t experience time. Photons are the smallest unit of energy that can be transferred between a light wave and a different particle. They have momentum and direction, but they don’t really travel exactly. They just mediate the force between light waves and matter.
Worded differently, a fermion (massive particle) within an electromagnetic (light) wave with a frequency of f may absorb some multiple of h x f joules of energy, where h is a very small constant. There is no way for the wave to transfer less than hf joules to the particle at a time. There is no need to think of photons as anything other than the smallest possible quantization of the electromagnetic wave rather than a particle of light. There’s no need to think of it existing for any amount of time or space.
Photons are the smallest unit of energy that can be transferred between a light wave and a different particle.
That is a much better description than what I have heard for the last 30 years: “A photon is a packet of energy”. That made no sense to me back then, and makes no sense to me now and, IMHO, doesn’t quite give a good visualization. It’s a placeholder, and I suppose it is slightly accurate depending on how “packet” is defined.
midribbon_action@lemmy.blahaj.zone
on 25 Jan 16:10
collapse
That’s awesome, and I totally agree. Everyone already intuitively knows that waves carry energy. We’ve all heard of tsunamis and earthquakes. The only difference on the quantum scale is that the amount of energy transferred is discretized.
I was blanking on her name. Sadly she is almost never given the credit she deserves
DasFaultier@sh.itjust.works
on 25 Jan 15:55
collapse
Didn’t want to make you fell like you have defend yourself, just wanted to turn it around and shitpost. But yeah, she rarely does.
I was also lowkey referencing the famous photo caption from am interview with “Amal Clooney, famous and successful lawyer and human rights activist, and her husband, an actor”. Referring to a certain George.
How on earth would an average person looking at this pic of Cavill know it’s Hugo Boss?
nightwatch_admin@feddit.nl
on 25 Jan 05:53
collapse
I am sorry, I thought this was a Hugo Boss ad and that that was the joke. I have never heard of Cavill?
FooBarrington@lemmy.world
on 25 Jan 06:36
collapse
That’s the beautiful man in the photograph
nightwatch_admin@feddit.nl
on 25 Jan 06:40
collapse
As dumb as I am, that I understood from the first reply. Appreciated the help!
FooBarrington@lemmy.world
on 25 Jan 07:52
collapse
Sorry, wanted to make a joke :D he’s a pretty famous actor. He played Geralt of Rivia in The Witcher, Superman in a bunch of DC movies, as well as many other roles.
nightwatch_admin@feddit.nl
on 25 Jan 22:21
collapse
I like the mood here. Also I looked him up and he is more famous than I understood. Nice!
threaded - newest
Camera: *flash*
“Fuck you photons, next time. Again.”
And it is remarkably consistent at doing that.
*in vacuo
Yes, but light always travels at the speed of light, regardless of its speed. It travels at c in a vacuum.
Light is never late, nor is it early, it arrives precisely when it means to.
Since an observer traveling through space at the speed of light experiences no time from the beginning of their journey until they decelerate (since their 4-velocity vector has non-zero values only in the 3 dimensions of space), photons don’t just arrive precisely when they mean to, from the moment they are emitted, they have already arrived.
Dispersion and nonlinearities would like to have a word ;)
But when you think about light’s speed in medium it seems like absorption and re emission which shifts light’s net velocity. The speed of light between the interaction is still c. That becomes obvious if you zoom into matter and find its mostly empty likr vaccum
No, that’s not really a useful way of modeling it for the case of light traveling through a linear medium.
The absorption/re-emission model implicitly localizes the photons, which is problematic — think about it in an uncertainty principle (or diffraction limit) picture: it implies that the momentum is highly uncertain, which means that the light would get absorbed but re-emitted in every direction, which doesn’t happen. So instead you can make arguments about it being a delocalized photon and being absorbed and re-emitted coherently across the material, but this isn’t really the same thing as the “ping pong balls stopping and starting again” model.
Another problem is to ask why the light doesn’t change color in a (linear) medium — because if it’s getting absorbed and re-emitted, and is not hitting a nice absorption line, why wouldn’t it change energy by exchanging with the environment/other degrees of freedom? (The answer is it does do this — it’s called Raman scattering, but that is generally a very weak effect.)
The absorption/emission picture does work for things like fluorescence. But Maxwell’s equations, the Schrödinger equation, QED — these are wave equations.
I wouldn’t say its a useful way, but if you think about it, everything is vaccum if you zoom enough. Also absorption can mean different things though so keep that aside and think of it as some interaction going on which in effect slows it down.
Now i looked up on youtube and this is what i meant (timestamp included). I was looking for 3b1b explaination but this one works too. It’s arguable if we can call it absorption or not, and what I said before might be ambiguous. But this guy explains it well
Edit: The 3b1b explaination is either in this video or in this one or maybe a combination of both
Relatively consistent.
I’m reasonably sure that Einstein’s breakthrough was more that he assumed light only travels at the speed of light and the all the equations worked.
Every experiment since has confirmed it.
Any speed that light travels is the speed of light
The real breakthrough
Technically everything moves at c (the speed of light) through spacetime, all the time. Most objects that have mass spend the majority of their motion in the time part, and thus move relatively slowly in space. If an object moves fast in space (where fast is a significant fraction of c) then it moves noticeably slower in time because the total spacetime vector value is always c.
Photons, being massless, do not move through time at all, and move through space at c.
That’ll break a few brains. To elaborate with an example: From the perspective of a photon, it’s “life” is over as soon as it begins. Even though it takes about 8 mins for a photon to travel from the sun to the earth from our perspective, no time at all has passed for it.
(Correct me if I misspoke.)
Light is generally better modeled by a wave, so I would say the wave doesn’t experience time. Photons are the smallest unit of energy that can be transferred between a light wave and a different particle. They have momentum and direction, but they don’t really travel exactly. They just mediate the force between light waves and matter.
Worded differently, a fermion (massive particle) within an electromagnetic (light) wave with a frequency of f may absorb some multiple of h x f joules of energy, where h is a very small constant. There is no way for the wave to transfer less than hf joules to the particle at a time. There is no need to think of photons as anything other than the smallest possible quantization of the electromagnetic wave rather than a particle of light. There’s no need to think of it existing for any amount of time or space.
That is a much better description than what I have heard for the last 30 years: “A photon is a packet of energy”. That made no sense to me back then, and makes no sense to me now and, IMHO, doesn’t quite give a good visualization. It’s a placeholder, and I suppose it is slightly accurate depending on how “packet” is defined.
That’s awesome, and I totally agree. Everyone already intuitively knows that waves carry energy. We’ve all heard of tsunamis and earthquakes. The only difference on the quantum scale is that the amount of energy transferred is discretized.
To add to this, this is always relative to an observer. If an object moves fast in space compared to you then it moves slower in time compared to you.
The other way around. Experiments said that light always moves at C and he deduced what follows from that for space time.
Uh, that discovery actually predated Einstein. He simply explained how the speed of light was constant for all observers
To be more accurate actually, he and his first wife explained it
Einstein proved time is relative just so he could take credit for it
You mean Mileva Marić and her husband?
I was blanking on her name. Sadly she is almost never given the credit she deserves
Didn’t want to make you fell like you have defend yourself, just wanted to turn it around and shitpost. But yeah, she rarely does.
I was also lowkey referencing the famous photo caption from am interview with “Amal Clooney, famous and successful lawyer and human rights activist, and her husband, an actor”. Referring to a certain George.
Oh I didn’t feel like you were attacking me, rather I appreciated you posting her name
ಠ_ಠ
This is unaceptable…you have to be assholes to each other.
Put a monocle on him and make it The Speed Of Causality.
Yeah, but is it a wave or a particle, eh, Einstein? Answer that!
Well, he did get a Nobel price for saying it’s a particle.
Yes.
Holy Minkowski spaces, Batman! It’s the old man himself!
He also discovered that the speed of light equals c.
Where c is defined as the speed of light
And that’s why we take vitamin C!
And why pirates drink coffee. “Boo, tea!” they cry
Weak
Now you know how I felt through this whole comment chain
Uh, Einstein was Jewish and Hugo Boss made the SS uniforms. This is a bit odd.
How on earth would an average person looking at this pic of Cavill know it’s Hugo Boss?
I am sorry, I thought this was a Hugo Boss ad and that that was the joke. I have never heard of Cavill?
That’s the beautiful man in the photograph
As dumb as I am, that I understood from the first reply. Appreciated the help!
Sorry, wanted to make a joke :D he’s a pretty famous actor. He played Geralt of Rivia in The Witcher, Superman in a bunch of DC movies, as well as many other roles.
I like the mood here. Also I looked him up and he is more famous than I understood. Nice!