Recreational Math

Just For Fun

How can people calculate their age and weight on other planets?

It’s certainly possible to find a person’s age and weight on another planet without having to travel there. To figure out weight, one just needs to know the amount of the gravitational pull on another planet, moon, or other space body. For example, based on the chart below, if a person weighed 100 pounds on Earth, he or she would weigh 38 pounds on Mercury (100 × 0.38).

A person’s age on Earth depends on how many times the planet has orbited the Sun during his or her lifetime. For example, a person 30 years old has traveled around our star 30 times. In order to work out how old a person is on another planet, the person’s age has to be divided by the period of rotation (in terms of Earth years). Thus, if the same 30-Earth-year-old person lived on Saturn, he or she would be just over 1 Saturn-year-old (30/29.5 = 1.02 Saturn-year-old). On Mercury, he or she would be 124.5 Mercury-years old (30/0.241 = 124.5).

Space Body Time to Orbit
around the Sun*
Gravity (Weight)
Compared to Earth
Mercury 87.9 days 38%
Venus 224.7 days 91%
Earth 1 year 100%
Moon 1** 17%
Mars 1.88 years 38%
Jupiter 11.9 years 254%
Saturn 29.5 years 93%
Uranus 84 years 80%
Neptune 164.8 years 120%
Pluto 248.5 years 0.01%
Sun N/A 2800%


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