Scientists have discovered that 70 million years ago when dinosaurs walked the Earth, the days were shorter than they are today. Based on a new study published in AGU’s journal Paleoceanography and Paleoclimatology, the examination of a fossil mollusk shell called rudist bivalves from the Late Cretaceous period revealed that each day consisted of 23 and a half hours, and each year lasted 372 days instead of the 365 days that we’re accustomed to today.
Scientists used lasers to examine the daily growth rings on a 70-million-year-old Torreites sanchezi mollusk that lived over nine years in a shallow seabed that was once in the now-dry land located in Oman’s mountains. And according to Niels de Winter, who is an analytical geochemist at Vrije Universiteit Brussel as well as the lead author of the study, they were able to find “convincing evidence” that the mollusks had symbiotic connections to photosynthesizing species as the ring patterns indicated that the shells grew faster during the day than they did at night time.
“We have about four to five datapoints per day, and this is something that you almost never get in geological history. We can basically look at a day 70 million years ago. It's pretty amazing,” de Winter stated.
Additionally, by performing chemical analysis on the shell (pictures of the shell can be seen here), they were able to find out that the temperatures in the ocean during the Late Cretaceous period were much warmer than previously believed. In the summer time, the water was around 40 degrees Celsius (104 degrees Fahrenheit) and would have surpassed 30 degrees Celsius (86 degrees Fahrenheit) during the winter. For comparison, today’s tropical oceans have temperatures of 28 degrees Celsius (83 degrees Fahrenheit) during the summer and 27 degrees Celsius (81 degrees Fahrenheit) in the winter.
While it’s been long speculated that days were shorter 70 million years ago, researchers say that this is the most accurate calculation that they have provided thus far. In fact, as the Earth’s gravitational grip on the moon gets weaker, the days do get a bit longer. The moon’s gravity slows the rotation of Earth because of the friction from the ocean’s tides but it also causes the moon to drift away from us. The average distance of the moon to Earth is around 239,000 miles and it’s slowly getting further away by moving about 1.5 inches each year.