3 ms·

Isn't the emission from a star, and the absorption within an eye or a telescope? There is clearly distance and time between the two here, how are you reducing i

Isn't the emission from a star, and the absorption within an eye or a telescope? There is clearly distance and time between the two here, how are you reducing it to 0?

sk5t 8y ago
Time passes for us, but not for the photon traveling at lightspeed.
- omarchowdhury 8y ago
  Would you explain why this is so? The speed of light is finite, not infinite.
  - zaarn 8y ago
    A photon is moving at the speed of light. Things moving at the speed of light do not experience distance or time (and have no mass), for them their creation and destruction are the same event. This effect is also valid for objects with actual mass, the faster you go the slower your time moves relative to everyone else and the shorter distances become. You can't hit the speed of light but you can get fairly close.
    - omarchowdhury 8y ago
      > A photon is moving at the speed of light. Things moving at the speed of light do not experience distance or time (and have no mass), for them their creation and destruction are the same event. How does this follow? There is still a traversal of spacetime at a limited speed between the creation and destruction. If the speed of light was infinite then yes I would agree with the proposition that no time or space experienced. You are offering a description without the explanation.
      - zaarn 8y ago
        >There is still a traversal of spacetime at a limited speed between the creation and destruction. From your point of view, that is correct. From the hypothetical point of view of a photon, an object moving at the speed of light, time does not pass and the distance gets squished into zero. You can observe a partial effect by looking at cosmic rays. We can detect several decay products of cosmic rays on the ground despite these decay products being far too short lived and too slow to have actually reached the ground. However, due to their high speed, their internal clock runs "slower" compared to ours and the distance between the top of the atmosphere where they are created in a collision or decay and the ground is much shorter than they can travel at their speed. A photon experiences the same effect times infinity; distance and time no longer have a reasonable meaning other than being 0.
        omarchowdhury 8y ago
        I'm sorry, I still don't understand and if you can provide me with further material to research I would appreciate it. From my point of view, for there to be 0 time and 0 distance is equivalent to saying the speed of light is infinite, ie. the point of emission is equivalent to its annihilation, but that is traversed at the limited quantity of c.
        zaarn 8y ago
        It's a bit of a hard subject to digest, I admit that. I guess one thing would be to accept that distance and experienced time aren't objective. If you move in a train, the time you spend inside the train moving and the distance you cover from your perspective will differ from the time that is shown on the clock at the station as well as the distance between the stations. By a very tiny amount. This process is exponential, so if you double the speed you travel at (as a number relative to four) the effect on your time and distance covered will quadruple. When you travel at C, then this effect becomes infinite. Time passes infinitely slow to the point that the time passed becomes zero. Same for distance. It also doesn't mean the speed of light is infinite, rather, from the perspective of the photon, ignoring the time part, the universe is exactly 0 in size. In turn that means travelling to some point in the universe, from the perspective of that photon, is instant. From the perspective of the outside observer, the photon is not traveling 0 distance, it's moving at the speed of light to a far away destination. From the photon's perspective, it's speed is not infinite, it's not moving at all, it's created and annihilated at the same point in space and time. From ours it's moving at the speed of light for a long time. Because these are different frames of reference, it's not as easy to compare speeds experienced in one to the other, especially if one is moving at C relative to the other. (Simplified) The entire affair is necessary because only things not having mass can move at C (and in turn, must move a C, a massless particle like a photon must always move at C). The entire rest of the universe has mass. From the photons frame of reference, everything else is moving at C. But that isn't allowed because that stuff has mass. So space itself is compressed into a 0 sized point to stop things from moving at C (from the perspective of the photon). Now, the photon however wouldn't be moving because in 0 sized space, you can't be moving at the speed of light. So in turn, time is experienced instantly and the photon is annihilated instantly so it can actually move at C (because it didn't move at all, it was destroyed instantly). In short; the photon doesn't experience time or distance because if it did it would be slower than C, it must always move exactly at C, therefore the universe arranges a situation in which the photon doesn't have to move at all, from it's own perspective.
- bookofjoe 8y ago
  It's always now for a photon.
  - omarchowdhury 8y ago
    It's always now for any object.

Isn't the emission from a star, and the absorption within an eye or a telescope? There is clearly distance and time between the two here, how are you reducing it to 0?

sk5t 8y ago

Time passes for us, but not for the photon traveling at lightspeed.

omarchowdhury 8y ago
Would you explain why this is so? The speed of light is finite, not infinite.
- zaarn 8y ago
  A photon is moving at the speed of light. Things moving at the speed of light do not experience distance or time (and have no mass), for them their creation and destruction are the same event. This effect is also valid for objects with actual mass, the faster you go the slower your time moves relative to everyone else and the shorter distances become. You can't hit the speed of light but you can get fairly close.
  - omarchowdhury 8y ago
    > A photon is moving at the speed of light. Things moving at the speed of light do not experience distance or time (and have no mass), for them their creation and destruction are the same event. How does this follow? There is still a traversal of spacetime at a limited speed between the creation and destruction. If the speed of light was infinite then yes I would agree with the proposition that no time or space experienced. You are offering a description without the explanation.
    - zaarn 8y ago
      >There is still a traversal of spacetime at a limited speed between the creation and destruction. From your point of view, that is correct. From the hypothetical point of view of a photon, an object moving at the speed of light, time does not pass and the distance gets squished into zero. You can observe a partial effect by looking at cosmic rays. We can detect several decay products of cosmic rays on the ground despite these decay products being far too short lived and too slow to have actually reached the ground. However, due to their high speed, their internal clock runs "slower" compared to ours and the distance between the top of the atmosphere where they are created in a collision or decay and the ground is much shorter than they can travel at their speed. A photon experiences the same effect times infinity; distance and time no longer have a reasonable meaning other than being 0.
      - omarchowdhury 8y ago
        I'm sorry, I still don't understand and if you can provide me with further material to research I would appreciate it. From my point of view, for there to be 0 time and 0 distance is equivalent to saying the speed of light is infinite, ie. the point of emission is equivalent to its annihilation, but that is traversed at the limited quantity of c.
        zaarn 8y ago
        It's a bit of a hard subject to digest, I admit that. I guess one thing would be to accept that distance and experienced time aren't objective. If you move in a train, the time you spend inside the train moving and the distance you cover from your perspective will differ from the time that is shown on the clock at the station as well as the distance between the stations. By a very tiny amount. This process is exponential, so if you double the speed you travel at (as a number relative to four) the effect on your time and distance covered will quadruple. When you travel at C, then this effect becomes infinite. Time passes infinitely slow to the point that the time passed becomes zero. Same for distance. It also doesn't mean the speed of light is infinite, rather, from the perspective of the photon, ignoring the time part, the universe is exactly 0 in size. In turn that means travelling to some point in the universe, from the perspective of that photon, is instant. From the perspective of the outside observer, the photon is not traveling 0 distance, it's moving at the speed of light to a far away destination. From the photon's perspective, it's speed is not infinite, it's not moving at all, it's created and annihilated at the same point in space and time. From ours it's moving at the speed of light for a long time. Because these are different frames of reference, it's not as easy to compare speeds experienced in one to the other, especially if one is moving at C relative to the other. (Simplified) The entire affair is necessary because only things not having mass can move at C (and in turn, must move a C, a massless particle like a photon must always move at C). The entire rest of the universe has mass. From the photons frame of reference, everything else is moving at C. But that isn't allowed because that stuff has mass. So space itself is compressed into a 0 sized point to stop things from moving at C (from the perspective of the photon). Now, the photon however wouldn't be moving because in 0 sized space, you can't be moving at the speed of light. So in turn, time is experienced instantly and the photon is annihilated instantly so it can actually move at C (because it didn't move at all, it was destroyed instantly). In short; the photon doesn't experience time or distance because if it did it would be slower than C, it must always move exactly at C, therefore the universe arranges a situation in which the photon doesn't have to move at all, from it's own perspective.
bookofjoe 8y ago
It's always now for a photon.
- omarchowdhury 8y ago
  It's always now for any object.