How long is a nanosecond?

Answer 1

Not very ;-). A nanosecond is one billionth of a second, which is 0.000,000,001 s. Written in engineering notation, that's 1E-9 s.

Think of it this way:

Take one second, and chop it up into one thousand equal pieces.

Now, take One of Those milliseconds; chop It up into one thousand equal pieces.

Now, take One of Those microseconds; chop It up into one thousand equal pieces.

One of those pieces is a nanosecond! Light travels about one foot in that amount of time.