5 ms·

It's 8 minutes for an "external" observer. Physicists say the photon itself does not experience time or space.

sahil50 5y ago
The photon does experience change over time and space. Take gravitational lensing by the Sun. The photons that we see from behind the Sun, are definitely affected by the Sun. From the photon's point of view, it is experiencing changes through time and space. Thoughts?
- ithinkso 5y ago
  Not from the photon's point of view. It is emitted and absorbed immediately. The distance traveled (in 4d spacetime) of a photon is always 0, no matter (pun intended) what's in between or what you observe.
  - sahil50 5y ago
    I don't think it is true to say that "it is emitted and absorbed immediately", because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter. I know the theory the view you're saying comes from, and the weight it has in academia, but it always struck me as useless. And that whoever came up with it was lost in notation.
    - ithinkso 5y ago
      >because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter. Not from the photon's point of view. This is very crucial and it is not because of notation or maths. The real difference is from your point of view. I know it's counter-intuitive but that's different from being useless. Sun->Earth or Sun->Jupiter is a small beer. It is the same for photons from the CMB being recorded. For them, they have been emitted and absorbed at the same instant and experienced no passage of time or distance traveled
      - sahil50 5y ago
        "Sun->Earth or Sun->Jupiter is a small beer"? How do you mean? This is a real physical example with real physical consequences for example for how much dimmer the light is per area (by 1/r^2) and by how much redder it is (by 1/r). What are the real physical consequences of thinking that the photon is "emitted and absorbed at the same instant"?

The photon does experience change over time and space. Take gravitational lensing by the Sun. The photons that we see from behind the Sun, are definitely affected by the Sun. From the photon's point of view, it is experiencing changes through time and space. Thoughts?

ithinkso 5y ago
Not from the photon's point of view. It is emitted and absorbed immediately. The distance traveled (in 4d spacetime) of a photon is always 0, no matter (pun intended) what's in between or what you observe.
- sahil50 5y ago
  I don't think it is true to say that "it is emitted and absorbed immediately", because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter. I know the theory the view you're saying comes from, and the weight it has in academia, but it always struck me as useless. And that whoever came up with it was lost in notation.
  - ithinkso 5y ago
    >because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter. Not from the photon's point of view. This is very crucial and it is not because of notation or maths. The real difference is from your point of view. I know it's counter-intuitive but that's different from being useless. Sun->Earth or Sun->Jupiter is a small beer. It is the same for photons from the CMB being recorded. For them, they have been emitted and absorbed at the same instant and experienced no passage of time or distance traveled
    - sahil50 5y ago
      "Sun->Earth or Sun->Jupiter is a small beer"? How do you mean? This is a real physical example with real physical consequences for example for how much dimmer the light is per area (by 1/r^2) and by how much redder it is (by 1/r). What are the real physical consequences of thinking that the photon is "emitted and absorbed at the same instant"?