eli5: Why do objects moving fast look blurry to our eyes?
In: Biology
The retina can only detect signals so fast. When you’re pumped with adrenaline then it will go faster, but there’s a limit to how fast our retinas can trigger. When objects move faster than the retina can fire, then the object may appear in more than one place or in a larger blurred area. For example, when a wheel is spinning fast enough to where its spokes are in positions slightly behind where they were before when your retina detected them, then it’ll appear as if the wheel spins backwards.
The objects moving too fast may not be blurry if our eyes are focused around where they are. If a fast thing flies by and our eyes aren’t focused on where that thing was, then it’ll be blurry because it’s out of focus and not because it’s moving fast.
Do they? Or is it just pictures of fast moving objects that look blurry?
An object moving faster than the ‘set speed’ of your retina prevents your eye from focusing on the object; it is moving too fast for your eye to do what the eye wants to do, which is track and then focus. It tracks but cannot focus in the set time it needs, so you see a blurry image. It’s like the object is going fast enough to cause its appearance in more positions than one at the same time, because you can’t focus quickly enough to see a single, detailed view of the object, preventing you from seeing anything other than a blur.
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