The Blue Whale (Balaenoptera musculus) is the largest animal ever to have lived on Earth. It's even larger than the largest dinosaur that once roamed the Earth millions of years ago. It can grow up to 30 metres in length and 150 tons or more in weight. Blue Whales can reach speeds of 30 mph (50 km/h), but 12 mph (20 km/h) is more typical. A Blue Whale's head is so wide that 50 people would be able to stand on its tongue. Its heart is close to the size of a small car. A human baby could crawl through a Blue Whale's arteries. A newborn Blue Whale calf weighs more than an adult elephant and is 25 feet (7.6 metres) long. During the first 7 months of its life, a baby Blue Whale drinks approximately 100 U.S. gallons (379 litres) of milk each day. Baby Blue Whales also gain weight very fast: 200 pounds (91 kg) every 24 hours. The longest Blue Whales ever recorded were two females measuring 33.6 m and 33.3 m respectively. There are some disputes over the reliability of these measurements, however, the longest whale measured by scientists at the American National Marine Mammal Laboratory (NMML) was 29.9 m long --- about the same length as a Boeing 737 aeroplane. The largest Blue Whale to date is a female that weighed 389,760 pounds (176,792 kg).