Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

What makes Earth spin on its axis without slowing down?

Betty Lou Bose
York, Pennsylvania

ASYSK1119_01
Planets form from disks of material swirling around a young star, such as in this artist’s impression. Because this disk is rotating, it imbues the resulting planets with rotational energy as well. Without forces acting upon them, these planets will keep spinning.
ESO/L. Calçada
The planets in our solar system formed from the solar nebula of gas and dust that surrounded our infant Sun. The material in this nebula was spinning; as the planets formed from this material, they, too, were spinning.

Objects in motion will stay in motion unless an outside force acts on them. In most everyday applications on Earth, friction counteracts motion by slowing things down, so energy must be added to keep an object moving (or spinning). Our planet doesn’t slow down much simply because there is almost nothing stopping it from continuing to spin.

But there are factors slowing it down, as well as speeding it up. The collision that formed the Moon added rotational energy to the planet, making Earth’s day only about five hours long. Over time, tides raised on Earth by gravitational interactions with the Moon and, to a much lesser extent, the Sun, have slowed our planet’s rotation to the 24-hour day we now experience. Current measurements show the effects of the Sun and Moon are slowing Earth’s rotation at a rate of about 2 milliseconds every 100 years.

Alison Klesman
Associate Editor

0

JOIN THE DISCUSSION

Read and share your comments on this article
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. View our Privacy Policy.

ADVERTISEMENT
ADVERTISEMENT
RCLP_ASY_0301_mediumrectangle

Untangle the mysteries of our solar system and its moons with this free download.