OK maybe ELI12 would do.
In: Physics
The faster you travel, the smaller distances seem. This can be hard to envision, since it takes a pretty good bit of speed to actually see this in action, but imagine a car speeding past you really fast. The faster it goes by, the less time it takes to pass you, right? This is partially a function of speed, but it’s also because the car literally looks smaller. However, this is only from the point of view of someone observing the car. From the guy driving the car, he’s sitting still and not moving. In fact, YOU are the one moving very fast indeed. He’s simply sitting still while the world zooms by. As a matter of fact, you are the one who shrunk a bit while he drove by. This is because while fast things shrink, fast things also view everything else as shrinking instead. This all comes to a point when you reach the speed of light. At the speed of light, everything else has shrunk so much that distance is meaningless. Everything is at the exact same point and can’t shrink anymore. Therefore, movement is meaningless. Movement is just moving some distance over time, and distance no longer exists. So a photon wouldn’t “perceive” a body moving to cut its path. To a photon, it doesn’t have a path because a path implies some distance to be travelled, some point B to get to from point A. Point A and B are the exact same point, as is everything else, because everything is shrunk. Either there is an object for it to collide with, or there is not, and the photon would never know the difference, because it would happen instantly by its personal timescale.
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