Gregory's Server@dgoldsmith - that’s a great link, after reading the page twice I’m sure I don’t fully appreciate/understand the topic.
However this line has zapped my brain….. “Relative to Earth's age in billions of years, Earth's core is in effect 2.5 years younger than its surface”
@ianbradbury The planet orbiting the black hole in “Interstellar" is an extreme example (if you've seen that, or know the plot).