prize9-1, Exercise 2: Your own 24-hour clock

Method: the Earth is 4.5 billion years old, which is 24 hours, so one hour is about 187.5 million years. For an event X years ago, the clock time is 24 hours minus (X / 187.5 million) hours.

Example (check the dates against a trusted source such as the Natural History Museum or the British Geological Survey):
- First land plants, about 470 million years ago: 24 - 2.5 = about 21:30.
- First flowering plants, about 130 million years ago: 24 - 0.7 = about 23:17.

Write the source next to each date.

Care: the ages are estimates and change. Quote a range if the source does.