Why is the length of a year different on every planet?
Our Solar System has eight planets, and each has a year of a different length. That has to do with their distance from the sun and how quickly they orbit our star.
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00:00Why is the length of a year different on every planet?
00:10Eight planets orbit our sun, and they do so in more or less elliptical orbits.
00:17Most places on Earth we experience a year through the course of the seasons.
00:22Only around the equator does weather remain largely the same all year round.
00:29In astronomical terms, a year is the period of time it takes for a planet to complete
00:34a single orbit around the sun.
00:36On Earth, that's 365 terrestrial days.
00:40This has to do with our distance from the sun.
00:43It's so far away that our planet has to travel 940 million kilometers to complete one orbit.
00:53Vast in size compared to the planets, the sun exerts enormous gravity.
00:58To remain in a stable orbit, the Earth must circle it at a very specific speed, 30 kilometers
01:05per second.
01:09If our planet moved any slower, it would get closer to our star.
01:17If it went faster, it would drift further and further away.
01:24The duration of a year therefore depends on how far away from the sun a planet orbits,
01:30as well as its speed.
01:32The closest of the eight to the sun is Mercury.
01:36Its orbit is much smaller than that of Earth's.
01:39But because it's so close, the effects of the sun's gravity are greater there.
01:45Mercury must orbit the sun faster to stay on track.
01:49It therefore covers less distance at a higher speed.
01:52A year on Mercury only lasts 88 Earth days.
01:58The farther away a planet is from the sun, the longer its orbit and the slower its speed.
02:04It might sound hard to believe, but a year on the outermost planet, Neptune, lasts for
02:10almost 165 of our years on Earth.