How many birthdays would you have on Mercury?
On Mercury, you would celebrate a birthday every 88 days.
A birthday marks one full orbit around the Sun. Because Mercury is the closest planet to the Sun, it moves much faster than Earth. It completes its orbit in just 88 Earth days, meaning you would have over four birthdays every single year.
Nerd Mode
Mercury is the innermost planet of our solar system, orbiting at an average distance of only 36 million miles from the Sun. According to Kepler's Third Law of Planetary Motion, the closer a planet is to its star, the faster it must travel to maintain a stable orbit. Mercury zips through space at an incredible speed of about 107,000 miles per hour, which is significantly faster than Earth's orbital speed of 67,000 miles per hour.Due to this high velocity and its shorter orbital path, Mercury completes one solar revolution in approximately 87.97 Earth days. This means a 'year' on Mercury is less than three months long on Earth. NASA missions like MESSENGER, which orbited the planet from 2011 to 2015, have provided precise data on these orbital mechanics. These measurements confirm that Mercury's year is the shortest of all the planets in our solar system.Interestingly, while a Mercury year is short, its day-night cycle is very long. Because of its 3:2 spin-orbit resonance, Mercury rotates on its axis very slowly. It takes about 59 Earth days to complete one rotation, but a single solar day—the time from one sunrise to the next—actually lasts 176 Earth days. This creates the strange reality where a single day on Mercury lasts twice as long as a Mercury year.
Verified Fact
FP-0001850 · Feb 16, 2026