Oh, I love questions like this! It's like being Randal from XKCD's What If!
I recently did something like this with a friend who was saying how another friend was "more than a moon" to him, so I went on to determine that the second friend was Neptune's Adams ring. I may post that one day. It needs to be memorialized.
How many times a second does a human eye send information to the brain?
The shutter speed/exposure time equivalent is between
1/15th and
1/30th of a second. Not quite what you were looking for, but I thought it might be relevant for the third answer, so I brought it up. Spoiler alert: it's not.
How fast would you need to run to outrun a mosquito?
You wouldn't. You can just walk away from it. A mosquito's top speed is between 1.2 and 1.5 MPH, or 2 and 2.4 KMPH. A human's walking speed is, on average, 3.1 MPH, or 5 KMPH.
If this seems wrong, you might not be dealing with a mosquito. They're some of the slower insects.
Mosquito's top speed.Human's walking speed.How fast would a car need to move to be invisible?
Well, there's two ways to look at this question, that I can see:
A. How fast does an object have to go so that light does not reflect off it?
B. How fast does an object have to go so that it can pass through a person's field of vision without being hit by enough photons to be a visible object?
To answer question A:The speed of light.
It's a bit anticlimactic, but it's what it is. Light moves at a constant speed, and even if you are moving at .9
repeating c (the speed of light), light will eventually hit you, and bounce off. But you cannot reach the speed of light, so the question, and subsequent answer, are irrelevant.
To answer question B:I was originally going to use FOV measurements to see how fast our car would have to go to pass through our FOV in the exposure times listed in the first question, but it turns out that humans have a FOV of approximately 180
o. That doesn't help us. At all.
Instead, I'm going to skip that, and determine the minimum photons required for a human to see an object. We do this by figuring the faintest light someone can see. Luckily, Google is rather forthcoming.
In 1942, Hecht, Shlaer, and Pirenne determined what is called the "Absolute threshold", the lowest amount of photons required for vision. They determined that an emission of 90 photons was all that was required for a human to see. However, only half reached the retina, and of that group,
9, or 20%, reached the fovea. It's theorized that the human eye can react to a single photon.
That last part was the most important, since it means that it is impossible, in this context, to make a car go so fast that it is completely invisible. Even if it were to go at c, then photons would still reflect off of the sides. One would eventually hit an observer.
Practically? If you've got the tech to make a car go fast enough that it starts to become difficult to see, invisibility is not a huge issue.
Source.And yes, I realize just how much of a neck beard this image makes me.
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Topic: The small random questions thread [WAAAAAAAAAAluigi] (Read 973998 times)