Santiago Andrés Triana<p>The Earth's Free Core Nutation (<a href="https://fediscience.org/tags/FCN" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>FCN</span></a>) motion is essentially a slight misalignment between the mantle's spin axis and the fluid core spin axis (I greatly exaggerated it here for ease of visualization). The camera starts in an inertial reference frame and slowly moves to the mantle's frame. As seen from the mantle the core seems to wobble!<br>This is all caused by the Earth's slow <a href="https://fediscience.org/tags/precession" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>precession</span></a>. The fluid core lags a bit resulting in a small misalignment.<br><a href="https://fediscience.org/tags/Earth" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Earth</span></a> <a href="https://fediscience.org/tags/Core" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Core</span></a> <a href="https://fediscience.org/tags/Science" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Science</span></a> <a href="https://fediscience.org/tags/Geophysics" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Geophysics</span></a> <a href="https://fediscience.org/tags/Nutation" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Nutation</span></a></p>