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I'd like to preface this by saying that I am not talking about glowing caused by the heat generated from air resistance. Instead lets just say that the hypothetical object we're talking about it in a perfect vacuum.

This question was inspired by the idea that a car is hit by more rain when it is moving than when it's stationary. Does this concept apply to photons?

In other words, do things get hit by more light and therefore reflect more light when they move at higher rates of speed? why or why not? If they do then I'd love to see a general equation for a given object (let's say a sphere to make it simple).

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    $\begingroup$ Is the car really hit by more rain when it is moving? ;) Or is it just that the rain drops encounter car at a higher speed? $\endgroup$
    – Roger V.
    Commented Nov 24, 2020 at 8:01
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    $\begingroup$ Check out Sanjoy Mahajan's The Art of Insight in Science and Engineering (Chapter 3) for a beautiful analysis of the rain problem. That being said, angles do strange things when you take Special Relativity into account, and the number of photons per unit area might be different. (I'm not completely sure about this, but see for example this paper.) $\endgroup$
    – Philip
    Commented Nov 24, 2020 at 8:13
  • $\begingroup$ @Vadim well the car is driiving into rain that would not otherwise hit it if it were standing still so it is being hit by more drops per second than if it were still from what I understand. $\endgroup$
    – Will
    Commented Nov 24, 2020 at 8:13
  • $\begingroup$ thank you @Philip I'll read both of the links you sent. $\endgroup$
    – Will
    Commented Nov 24, 2020 at 8:14
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    $\begingroup$ @Will the car is also driving away from the drops that would otherwise hit it. If we neglect the shape of the car, assuming it just a flat rectangle, then it is always the same surface exposed to the same density of rain drops, just falling at a different angle. This is obviously a non-relativistic analysis. $\endgroup$
    – Roger V.
    Commented Nov 24, 2020 at 8:43

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No, they do necessarily get hit by more photons, for the simple reason that you have to start by defining what light sources are involved. And you also have to define "brighter," which I'm guessing you mean "more photons per second are reflected into my eyeball."

So let's look at two cases. First, like with rain, assume illumination perpendicular to direction of travel. You end up with fewer photons being reflected towards you the faster it moves, just like you running thru the rain.
Second, suppose you aim a flashlight directly at the object. Then (perfect collimation), all the photons are reflected back at you. If the object is stationary, then all the photons arrive in a time period equal to the length of time the flashlight is turned on - a "pulse width" . If the object is moving towards you, the apparent pulse-width is reduced by the distance the object moves during the pulse-width time. (there's also Doppler frequency shifting but I don't think that's what you are asking). So in this case, I believe you'll see a shorter and thus brighter (photons/second) reflection.

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