The spinning Solar System
Start the clock and watch the nine bodies go around, each at its own speed. Then switch to the real distances, and see how empty it is.
Here the distances are squeezed, as in almost every book: if they were real, the four inner planets would all be stuck to the Sun. Try the other button.
Why the faraway planets are so slow
Neptune is 78 times farther from the Sun than Mercury, and that alone would make its trip very long. But there is more: the farther away a planet is, the more gently the Sun pulls on it, and the slower it goes. The two add up, and that is why Mercury goes around in three months and Neptune takes a lifetime.
One year on Neptune lasts 164 of our years: since it was discovered, in 1846, it has made just over one full trip.
Something to know: here the planets all start in a line, which is a handy way to draw them and never really happens. Where they actually are today is not in the book’s data, and we did not make it up. What is true, and what you can watch, is how long each one takes to go around.
The card: gravity and orbits · And for sizes: the size comparison tool
The numbers come from the NASA Planetary Fact Sheet, line by line.