A blue whale weighs 190,000 kilograms (420,000 pounds), but how do we know that?
When surfacing, a blue whale shows only a fraction of its enormous body and hauling a live whale out of the water is cruel and impractical, so their weight has been measured from dead specimens found washed ashore. Once a carcass is discovered, researchers can determine its weight by placing it on an industrial scale. Unfortunately, whaling still continues in parts of the world. Some vessels collect data about the animals that are brought on board, so these individual whales can be studied extensively.
Image: Amit Patel