Cells make up you, your friend, your hamster, and your mom's broccoli surprise. If it's alive or ever was alive, it is made of cells. Space scientists looking for life on Mars are trying to find microbes made of simple cells—not little green men—and biologists who search for cures to diseases work with cells. Small as they are, cells determine how life unfolds from its beginning to its end.
Planet Earth is made up of all kinds of rocks. When you know the type of rock you have in your hand, you will know something about the history of the place it came from.
One morning, the old wooden dam on the Rappahannock River went up in clouds of smoke. It was a huge thing—ancient and strong, built in layers to tame the river so that the power of the water pushing against it could provide electricity for the town. But it had been years since anyone tapped that power. Now, the dam was falling apart, and it was decided that it had become dangerous. So the Army Corps of Engineers blew it up one morning, and the river was flowing freely again—just as it had in previous centuries. By getting rid of the dam, the river had a chance to go back to being more like it once was. There would be more fish, which would mean more birds, and, really more of everything.
Slow, sleepy winter days find many animals curled up in their dens. They sleep warmly through winter, awakening in spring ready to enjoy the renewed Earth. This unusual, deep sleep is called hibernation.
What Is Hibernation?
True hibernation is a very deep sleep. The animal's body temperature drops, its breathing slows, and it is very difficult to awaken. But some animals, such as most bears, do not really hibernate.
Circles, squares, pentagons, octagons, polygons, angles, rays, points, and lines, there are so many names to learn in geometry. They may sound strange and new, but geometry is all around you. Your computer monitor's surface is more or less a rectangle, your pencil is roughly a cylinder, and, viewed from the top, the cable from your mouse to the computer, is a line segment. Once you start thinking about geometric shapes, you'll find them everywhere.
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