Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

stargazine_ep3_banner.thumb.jpg.5533fb830ae914798f4dbbdd2c8a5853.jpg

Recommended Posts

Would someone explain the concept of the earth's figure axis please.  The term came up in a forum discussion elsewhere about the affect of the tsunami that hit Japan a few years ago that supposedly shifted the earth's figure axis by 8 inches. 

I googled but didn't find much. I understand it's to do with the earth's distribution of mass. I can see that if the earth's mass shifts, because of an earth quake say, then the centre of mass can shift, and therefore the axis of rotation can shift. What surprises me is that the shift is expressed in units of distance not angle. So is the earth's figure axis parallel to the earth's north south axis through the poles?

Share this post


Link to post
Share on other sites

First time I've heard of it, but this article might help:

https://news.nationalgeographic.com/news/2011/03/110316-japan-earthquake-shortened-days-earth-axis-spin-nasa-science/

It says, and I quote:

Quote

Instead the quake shifted what's called Earth's figure axis, an imaginary line around which the world's mass is balanced, about 33 feet (10 meters) from the north-south axis.

So Earth's figure axis is an imaginary line that represents mass balance rather than rotational axis. It's very close to rotational axis, and I guess it is parallel to it.

Share this post


Link to post
Share on other sites

Thanks.  That link doesn't seem to work on my iPad. Nevertheless going by your quote I am surprised that the axis of rotation is not the same as the axis around which the mass is balanced. 

Share this post


Link to post
Share on other sites
3 hours ago, Ouroboros said:

Thanks.  That link doesn't seem to work on my iPad. Nevertheless going by your quote I am surprised that the axis of rotation is not the same as the axis around which the mass is balanced. 

In principle it is, but center of mass is constantly shifting - tides, polar ice, tectonic movements, .... so those two are very close, but as you can see - not perfectly aligned and there are changes to this distance.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.