**Interview with Researchers on Earth’s Rotational Changes Over Millions of Years**
**Interviewer:** It’s fascinating to think about our planet’s past. Recent research suggests that billions of years ago, a day actually lasted only about 20 hours. Can you shed some light on that?
**Ma Chao:** Yes, that’s correct! Our team, in collaboration with international astronomer Jacques Laskar and others, has reconstructed the process of Earth’s rotational slowdown from geological records spanning 700 million to 200 million years ago. What we found indicates that the Earth did indeed rotate more slowly in the past. Approximately 700 million years ago, a full rotation took about 20 hours, while around 200 million years ago, it was about 23 hours.
**Interviewer:** That’s quite a significant change! How did you come to these conclusions?
**Ma Chao:** We’ve uncovered a pattern in the Earth’s rotation that follows a staircase-like evolution—slowdown, stability, slow again, and then stability. Our geological data strongly suggest that the decrease in Earth’s rotational speed has not been a constant nor linear process, as was traditionally thought.
**Interviewer:** Interesting! What do you attribute this rotational slowdown to?
**Ma Chao:** One major factor is tidal dissipation, which relates to the gravitational pull between the Earth and the Moon. Essentially, the Moon’s gravity stretches the Earth’s waters, creating tides that, through friction along coastlines, dissipate energy and slow down the planet’s rotation.
**Interviewer:** It sounds like there are some significant geological events linked to these changes in rotation. Can you elaborate on that?
**Ma Chao:** Absolutely! There are two major geological events that correspond to points of change in the rate of rotational slowdown—one during the Cambrian explosion about 550 million years ago, and the second during the Permian-Triassic extinction event about 250 million years ago. However, the precise causal relationships between these events and the changes in rotation need further exploration.
**Interviewer:** So, what were the dominant life forms during the periods with different rotation speeds?
**Ma Chao:** In the era of a 20-hour day, single-celled organisms thrived in the oceans. Following the Cambrian explosion, more complex life forms emerged, such as the enormous anomalocaridids that dominated marine ecosystems. But during the late Permian extinction event, around 90% of species went extinct. Yet, afterward, life rebounded, paving the way for the age of dinosaurs.
**Interviewer:** That’s quite a dramatic history! Considering these findings, how do you think the Earth’s current rate of rotation and the distance of the Moon from Earth impacts us today?
**Ma Chao:** Great question! The most immediate consequence of Earth’s rotational slowdown is the change in day length and consequently light exposure, which can influence weather patterns and, in turn, affect climate and plant growth. However, our understanding of these effects still requires further study.
**Interviewer:** It seems like we have a long way to go! With geological time scales stretching over millions of years, where do we currently stand in this process?
**Ma Chao:** Right now, we are in a period of stability in the Earth’s rotation. Over the next million years, we don’t anticipate significant shifts in this trend.
**Interviewer:** Thank you for sharing these insights! It really expands our understanding of Earth’s history and its effects on life throughout time.
