Shorter days during dinosaur eraDate: 13 March 2020 Tags: Geography & Environment
When dinosaurs were roaming the Earth, days were shorter with about half an hour compared to the length they have today.
Seventy million years ago, the planet was turning faster than it does today, and it was rotating 372 times a year compared with the current 365, according to an analysis of an ancient fossil mollusk shell that was from the late Cretaceous period.
This means that a day lasted for about 23 and a half hours. It backs up what astronomers had already theorized about the length of days millions of years ago.
Experts analyzed a single mollusk that used to live for more than nine years in a shallow seabed in the tropics. The location is now a dry land in the mountains of Oman.
This mollusk grew really fast, and it was laying down daily growth rings. The study mentioned above used lasers to sample tiny slices of the mollusk’s shell and count the growth rings.
Experts focused a laser on small bits of the mollusk’s shell, and they made holes 5 micrometers in diameter.
This analysis provided accurate measurements of the width and number of the daily growth rings and also seasonal patterns. Experts used the seasonal variations in the fossilized shell to identify the years.
The length of a year has stayed steady throughout Earth’s history, because Earth’s orbit around the sun stays the same. But the number of days within a year has been shortening over time because days have been growing longer.