Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Just what the title states with the qualification that the change must be affected without using other celestial bodies as mentioned in the Clarke/Baxter SF 'Sunstorm'.

Obviously given the momentum of Earth it would require a major something to break the inertia. But something like the way an ice-skater whilst spinning on their own axis can apply a touch of heel/toe at the correct point to change the way they spin. For instance, change the rate at which our oceans move with the spin of Earth ...

This is a 'curiosity' question rather than a real-life problem so please feel free to vote to close.

share|improve this question
add comment

1 Answer 1

up vote 6 down vote accepted

Inertia does not suddenly "break" in the sense that the axis will remain fixed until some force threshold is reached, and move thereafter (for that matter, an ice skater cannot change direction by any clever combination of heel-toe maneuvering).

In reality, any change in the mass distribution of the earth will move the orientation of the axis. Small changes in the mass distribution will result in small changes in the orientation of the axis, but a small change is still a change. So, in a technical sense, moving some gravel from a quary to your driveway will change the axis. Even walking around will change the axis.

However, for a measurable change the mass redistribution would need to be immense. practically this is impossible, but only in the engineering sense, not the theoretical.

share|improve this answer
We do make measurable changes simply by filling/emptying dams - but only because we can make immensely sensitive measurements (eg radio VLBI) –  Martin Beckett Jan 3 '12 at 4:35
I have heard earthquakes also cause measurable changes in the axis orientation. –  Vineet Menon Jan 3 '12 at 5:30
space.com/11115-japan-earthquake-shortened-earth-days.html it seems the spin accelerated, as with ice skate figures. also estimates of shift of order of inches, e.g. thirdage.com/news/… –  anna v Jan 3 '12 at 5:50
add comment

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.