as they orbit the Sun. The time it takes to spin once - one "day" on a comet - is also called a period, but in this case, it is specifically called the rotational period. Just in case you're ...

These sedimentary archives offer not just geographic history, but evidence of the Earth's rotational history. The datasets covered the period from 280 to 650 million years ago. The timeline ...

Opinions expressed by Forbes Contributors are their own. Jamie Carter is an award-winning reporter who covers the night sky. A single rotation of our planet takes 24 hours and constitutes a day.