You’re not from this planet – Math Skills

You’re not from this planet – Math Skills – calculating your age on different planets

Earth completes one rotation on its axis in what has come to be a universal measure of 24 hours: one day. And when Earth completes one orbit around the sun, the measure is 365.26 days: one year. But not all planets in the solar system rotate or orbit at the same rate, which sure makes a difference when it comes to celebrating your birthday. Use the formula and chart below to calculate how old you would be–in Earth years or days–on each planet.

A. How many days old you were on your last birthday: (Your Age) x 365.26

B. How many days it has been since your last birthday: (Today, in number of days since January 1) – (Your birthday, in number of days since January 1) + 1. If the result is less than 0, that means you have yet to celebrate your birthday this year–add an extra 365.

C. How many days old you are today: Add the results from Step A to Step B

D. How old you are on (planet): (Result in Step C) / (Length of planet year in Earth days)

E. How many days old you are on (planet): (Result in Step C) x 23.934 / (Length of planet day in hours)


You can check students’ math on this page:

Venus is odd because it’s the only planet with its day longer than its year.

Planet Length of year Length of day Your age Your age

(in Earth days) (in Earth hours) in Earth in Earth

Years Days

Mercury 87.969 1,407.6

Venus 224.7 5,832.5

Earth 365.26 23.934

Mars 686.98 24.62

Jupiter 4,330.6 9.92

Saturn 10,747 10.5

Uranus 30,588 17.24

Neptune 59,800 16.11

Pluto 90,591 153.3

Don’t Stop Now!

1. On some planets your parents or even grandparents may still be in what Earthlings consider “diaper age.” Select one older relative and find out his or her age throughout the solar system.

2. According to the chart above, why is Venus odd?

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