New evidence shows Earth’s day was shorter
Once upon a time, a day on Earth lasted about 19 hours, and this was not a short-lived phenomenon but rather an entire geological epoch. A new analysis of Precambrian rock indicates that the planet's rotation speed has remained virtually unchanged for about a billion years.
This topic is covered in a study published in Nature Geoscience.
How did the Earth "get stuck" on a 19-hour day?
Scientists studying Cambrian geological data concluded that, during the middle of the Proterozoic era (approximately one to two billion years ago), the usual slow increase in the day's length actually stopped. The length of the day then remained almost constant at around 19 hours.
Usually, the Earth gradually slows its rotation due to tidal interactions with the Moon. The Moon "drains" some of the Earth's rotational energy. In the distant past, however, this effect was almost balanced by atmospheric tides caused by solar heating.
Under certain conditions, atmospheric waves entered resonance, creating a force that pushed Earth to rotate faster. Consequently, the braking influence of the Moon was offset, and the day stabilized at approximately 19 hours.
To recreate this period, researchers compiled 22 independent estimates of the length of a day on Earth. They obtained these estimates by analyzing tidal deposits, stromatolites, and rhythmic geological structures. They also used cyclostratigraphy methods, which allow for the evaluation of the planet's rotation speed based on ancient sedimentary rocks.
A statistical analysis revealed a clear "plateau" in the length of the day. This plateau lasted approximately one billion years, after which the day slowly began to lengthen until reaching its current length of 24 hours.
This long period coincides with the "boring billion," an era of stable climate and slow biological changes. It also coincides with the period between two significant shifts in atmospheric oxygen content.
Researchers hypothesize that oxygen and ozone levels influenced the strength of atmospheric tides, thereby maintaining a resonant state. Once this process was complete, the increase in day length could have created conditions that allowed for more efficient photosynthesis and growth of oxygen, which is necessary for the development of complex life.
Read more:
- Time on Mars is unstable — NIST reveals how it really flows
- Scientists find Earth-like planet that could host life