# Does a photon experience time as we perceive it?

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If a photon travelled a billion light years to come to Earth, how do those billion years pass from the photon’s perspective?

In: Physics

The spacetime interval between the photon leaving its origin to arriving at earth is s^2 = ct^2 – x^2, which is equal to zero since x=ct (the photon travels at the speed of light). For any ordinary object traveling at a speed less than the speed of light, the proper time experienced by that object between any two events happening on its own trajectory (world line) is equal to the spacetime interval between the events. It is unclear whether this idea can be extended to photons, but if we assume it can, it means the proper time between the two events is zero. That is, from the photon’s perspective, it leaves and arrives at the exact same time.

That time passes instantly for the photon. The moment it is emitted, and the moment it is absorbed, are a single moment when considered from the photon’s reference frame. In effect, photons don’t experience time at all.

No, photons do not experience time at all. The closer you go to light speed the “slower” time moves at light speed time stops.

From a photons perspective all things are instantaneous. The photons leaves the star 2 billion light years away and hits your eye at the same instant. The star and your eye are also infinity close together from the perspective of the photon.

TL;RD relativity is a hell of a drug