The revamped fossil hall at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C., wanted to chart swings in Earth’s average surface temperature over the past 500 million years to show ancient temperature extremes and how rapid shifts between them have led to mass extinctions. A loose-knit collaboration, called Phantastic, has been assembled to put together a rigorous record of Earth’s temperature variations over the past 500 million years. Antaractic ice cores go back about million years. Oxygen isotopes (delta-18O) in tiny fossilized shells on the ocean floor provide a longer-term record to about 100 million years. Ocean floor older than 100 million years is scarce, because of the churn of plate tectonics. Beyond that marine fossils found on land provide a record which has been difficult to establish a chronology for. The Phantastic collaboration is using a new dating technique, called clumped isotopes, that measures the abundance of two or more rare isotopes. This promises to extend the temperature record to a billion years. The temperature curve that is presented at the new fossil hall is a beta. The plan is to replace it when the Phantastic team’s efforts reach maturity.