How fast does the Earth's inner-core rotate compared to the Earth's daily rotation?

The inner core is always described as a spinning/rotating solid core while the Earth has a single revolution per day. I've always imagined it as a fast spinning top, but realised I don't actually know if it is a faster spin or slower spin when compared to the Earth's rotation.

And even if I knew the speed (which I don't), a number doesn't mean anything unless compared to something relatable.

So how much faster/slower is the core rotation compared to the 24 hour day rotation?

Eg the inner core rototes 25 or 2.5times per 1 day. Or the inner core rotates 0.5 times per 1 day.

  • $\begingroup$ It is impossible earth's core is faster rotating. $\endgroup$ Oct 3, 2016 at 18:56
  • $\begingroup$ Just wanted to say thank you from 2023 to 2016 your answer helped me. $\endgroup$ Mar 29, 2023 at 14:25

1 Answer 1


Roughly once per day, but a tiny bit faster. As the website for Columbia University's Lamont-Doherty Earth Observatory says:

The inner core rotates in the same direction as the Earth and slightly faster, completing its once-a-day rotation about two-thirds of a second faster than the entire Earth. Over the past 100 years that extra speed has gained the core a quarter-turn on the planet as a whole...

Off the top of my head, I would have doubted that the core had a significantly different rotation rate than the mantle and lithosphere, because it would create different mixing layers in the liquid outer core, resulting in tangles in the Earth's magnetic field, similar to what happens in the Sun.

  • $\begingroup$ Wow. I knew it wasn't that much faster but a whole 2/3 of a second! $\endgroup$ Sep 29, 2016 at 7:26
  • 1
    $\begingroup$ Just a small update to Spencer's answer from 2016. Recent measurements suggest that the core has ben slowing relative to he mantle, and is now probably rotating slightly slower, and that it may oscillate between spin faster/spin slower phases over several decades $\endgroup$
    – Andy M
    Mar 31, 2023 at 8:58

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