I couldn't find any TAGS that fit my question…
I don't know if I'm doing this correctly.
I want to know how long a "twinkling of an eye" would be. A twinkling of an eye is the time it takes from the moment the light hits the front of the eye, until it hits the back of the eye and is reflected back.
I googled some stuff and found that an average human eye is about 26.6666667 mm, so we'd double that to 53.3333334 mm, this is the distance light must travel.
the speed of light is 299,792,458 M per second, which is 299,792,458,000 mm per second. (notice i took the speed of light from Meters to millimeters).
So, now do i divide 299,792,458,000 mm by 26.6666667 mm? if so, google says that's:
(299 792 458 000 millimeters) / (53.3333334 millimeters) = 5.62110858 × 109
so how do I turn 5.62110858 × 109 into time, or… i'm confused..
The smallest amount of time is a plank, or, $10^{-43}$ seconds. How close would the 'twinkling of an eye' be to a plank?
Best Answer
I think I would define a "twinkling of an eye" to be the amount of time it takes for reflected light to travel from the surface of the eyeball in question to an observer, which would of course radically depend on how far away the observer was.
But, regarding your computation, your issue is just keeping track of units, otherwise known as dimensional analysis. $299,792,458,000\frac{\text{mm}}{\text{sec}}$ is not the same thing as $299,792,458,000\text{ mm}$.
You have a length, $L=26.\bar{6}\text{ mm}$, and a velocity, $V=299,792,458,000\frac{\text{mm}}{\text{sec}}$. To get a time quantity, you would have to divide $\frac{L}{V}$, because this corresponds to computing $$\frac{\text{length}}{\tfrac{\text{length}}{\text{time}}}=\frac{\text{length}\cdot\text{time}}{\text{length}}=\text{time}$$ It will have units of $$\dfrac{\text{mm}}{\tfrac{\text{mm}}{\text{sec}}}=\frac{\text{mm}\cdot\text{sec}}{\text{mm}}=\text{sec}.$$ So, the result is $$\frac{L}{V}\approx8.895\times 10^{-11}\text{sec}.$$