| Fun facts! The longest nerve cell in your body, the sciatic nerve, runs from your lower spine to your foot, roughly two to three feet in length! The crust of the earth is solid. So is the inner core. But in between, the outer core and mantle (90 percent of the mass of the earth) are liquid to molten semi-solid. We do not live on a particularly solid planet. Darwin believed that humanoids emerged in Africa. No one believed him for 50 years, until Dart uncovered his famed skull in 1924. The Himalayas, the world’s highest mountain system, are the result of the ongoing collision of two huge tectonic plates (the Eurasia plate and the Indian subcontinent), which began about 40 million years ago. In the bizarre quantum world, many of our “normal” laws do not apply. There, objects (like electrons) can be (and regularly are) in two different places at once without upsetting any of the laws of quantum existence. Discovered in January 2000, the closest black hole is only 1,600 light years from Earth and is known as V4641 Sgr. Such normal black holes are several times the mass of the sun. But supermassive black holes reside in the hearts of galaxies and can be as massive as several hundred million times the mass of the sun. As the universe is expanding, every galaxy in existence is moving away from our own Milky Way—except for one. Andromeda, our nearest neighbor, is moving on a collision course with the Milky Way. Don’t worry, though: the collision won’t occur for several million years. In 1922 a 14-year-old boy suffering from type I diabetes was the first person to be treated with insulin. He showed rapid improvement. | |
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