1Two things you need to know
A "year" is one loop — and the Sun's pull is a leash
You only need two ideas. Watch each one:
A year = one full loop
Every planet circles the Sun. One trip all the way around and back to the start is exactly one year. Finish the loop, you're a year older.
The Sun's pull is a leash
The Sun tugs on every planet. Up close the leash is tight and strong. Far out the leash goes weak and floppy — the farther you are, the gentler the tug.
Try the ingredient below. Make a prediction before you compare the completed cases.
2Your turn — move a planet
Walk one planet around a fixed orbit
Drag one planet around its fixed circular path. A full lap is one year. This control chooses position, not speed; the two-orbit race comes after your prediction.
3Now race them
Two planets, one start line — does the far one move at the same speed? 🏁
Forget moving one planet. Now we lock a close planet and a far planet in place and let them go at the very same instant. Guess first — then release them and count the birthdays.
Guess before you release them
A far-out planet has a longer path to travel. Does it move along that path at the same speed as a close one — or slower?