Arithmetic, not a law

The half-billion-year window

Earth is 4.54 billion years old. Divide that by the eight worlds from Io to Earth. You get about 567 million years. That number is arithmetic.

How the number is made

Earth’s age (Allègre and colleagues, 1995) divided by eight: Io, Europa, Ganymede, Callisto, Titan, Triton, Mars, Earth. Venus and Mercury are not in that count. They are read as an earlier turn, already spent. The Great Red Spot is not in that count either. Treat it as a ninth, un-emerged body and the window falls near 504 million years. The same division was first posted here on 10 June 2015 as Planetary Shift Every 570 Million Years.

Change the count by one and the window moves by sixty to seventy million years. A number that moves when you change the count is a ruler you chose, not a law of nature.

Why it still gets a page

Around that same order of magnitude sit dates other people measured: Venus’s surface only a few hundred million years old; Titan rivers that look too fresh for a billion years of today’s rain; late floods and young volcanic skins on Mars; Europa’s young ice; Triton’s young patches; Earth’s Snowball ending and the Cambrian diversification; a 1979 argument that Jupiter’s three-moon lock may be younger than 500 million years.

Those dates were gathered here in 2015. They are a notebook, not proof that one process runs the solar system. Unrelated local processes can make young numbers too.

What this page will not say

This page does not say how a world would change its place in the solar system. Present distance is not a path. Geology can be set in order without a finished force law. It cannot be said to have moved a world until that law exists.