The incubation period for the coronavirus is between 2 and 14 days. On average, COVID-19 symptoms appear around 5 days after exposure, but this can vary. Learn more.

Variation in the amount of CO2 in the atmosphere is usually taken to be the main cause of climate change on geological timescales. The apparent exceptions to the link threaten to undermine that view.

Found in rock samples retrieved in Australia more than 60 years ago, the microfossils dating to the Lower Ordovician Period, approximately 480 million years ago, fill an approximately 25-million-year ...

The Ordovician–Silurian extinction events, also known as the Late Ordovician mass extinction, were two events that occurred somewhere between 450 and 440 million years ago. These are considered one of ...