# Since the Earth is spinning, the objects in its surface are always changing direction, and thereby, changing velocity. So is this not an example of a non-inertial frame of reference?

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Since the Earth is spinning, the objects in its surface are always changing direction, and thereby, changing velocity. So is this not an example of a non-inertial frame of reference?

In: Physics

Yup. If you take the entire Earth into account, you won’t have a true “inertial reference frame” because there is slight differences from if it were not rotating.

However. These differences are very small, so anything not related to the Coriolis Effect or some other way involving the entire planet is fine to consider the surface to be inertial.

Yes, it is! And there are places where this is important – build an accurate gyroscope, and it will appear to rotate at the rate of 1 rotation per day. And it causes weather systems to rotate.

But for most of the things we do, a rotation rate of one per day isn’t going to be measurable.

Yes. It’s a rotating reference frame, but that rotation is rarely an issue for anything but the most precise measurements. The mass of the earth is just so much bigger.

Yes. You can use a [Foucault pendulum](https://en.wikipedia.org/wiki/Foucault_pendulum) to verify this fact. They need to be large to work well but they’re common at science museums.