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The speed of light is $2.998 \cdot 10^8 \mathrm{\frac{m}{sec}}$. This means that it travels $2.998 \cdot 10^8$ m in one second (one light-second).
However, light travels $2.998 \cdot 10^8$ m by traveling one meter at a time. So, it takes $\frac{1}{2.998} \cdot 10^{-8} \mathrm{sec}$, which is $3.336 \cdot 10^{-9}$(3.3 billionths) sec to travel one meter.
Light also travels one light-second by traveling one millimeter at a time. Light therefore would travel one millimeter, which is $\frac{1}{1000}$ meters ($1 \cdot 10^{-3}$ m), in $\frac{1}{1000}$ the time that light takes to travel one meter.
In the same vein, light would travel one micrometer $1 \cdot 10^{-6}$ m in $\frac{1}{1000}$ the time it takes to travel one millimeter. It would therefore take approximately $3.336 \cdot 10^{-15}$ seconds for light to travel one micrometer. (Check this for yourself.)
But light nevertheless travels one light-second in one second, or one light-year in one year, or a billion light-years in a billion yearsâ€”all the time traveling one micrometer at a time! It just travels a very large number of micrometers in a very large number of really small bits of time.
Use GC for your computations. Enter "*" for multiplication, "/" for division, shift-6 ("^") for an exponent, "$\downarrow$" to exit an exponent, "$\rightarrow$" to move to the next term.
You might be tempted to use your personal calculator for these exercises. PLEASE DON'T DO THIS. Use GC. It is by using GC that you will become comfortable using it. Being comfortable with GC will be very important for later chapters.
A sheet of A4 paper is 21 cm by 29.7 cm and is 0.1 cm thick. Suppose you can slice the sheet without losing any paper.
Slice it in half lengthwise and stack the slices. You will have a stack that is 0.2 cm high. The slices will be 14.85 cm by 21 cm.
Slice each of these pieces in half lenghwise and stack the pieces. You will have a stack 0.4 cm high. The slices will be 14.85 cm by 10.5 cm.
Continue this process a total of 50 times. How high will the stack be in km? In trips to the sun? What will be the dimensions of the slices?