Building a budget involves calculating your monthly income and expenses to see how much money you have and where it's going. It can help you pay your bills, save for the future and achieve your goals.

The velocity of light in vacuum, c, is approximately 3 × 10 8 m s −1, fast enough to make 7.5 round-the-world trips in a single second, and to move a distance of 300 mm in 1 ns. This ultrahigh speed ...