# #7: Speed of light

by Tomasz Nurkiewicz

Speed of light is not as abstract to us, software engineers, as you might think. If you are deploying to the cloud or if you want to squeeze every bit of performance in your app, speed of light holds you back

# Distance the light travels during one CPU cycle at 5 GHz

\begin{align} c = 3 \cdot 10^8 \mathrm{m \over s} \\ f = 5 \mathrm{GHz} = 5 \cdot 10^9 \mathrm{Hz}\\ t = {1 \over f} \\ s = c \cdot t = {c \over f} \\ s = { {3 \cdot 10^8 \mathrm{m \over s}} \over 5 \cdot 10^9 \mathrm{1 \over s}} = \\ = {3 \over {5 \cdot 10}} \mathrm{m} = {30 \over 5} \mathrm{cm} = \\ 6 \mathrm{cm} \end{align}

# More materials

- Latency Numbers Every Programmer Should Know
- Instruction pipelining
- A CPU history
- Moore’s law
- The distance from Perth, Australia to New York

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