Karen Hill

In 1960, Louis Leakey found the skull, leg, foot, and hand bones of another hominid in Tanzania, East Africa. It was dated at around 2 million years old, just slightly older than Zinj. The bones showed that this ancestor walked on two feet and had a large brain, but there were differences. The teeth were … Read more

Alfred Wegener conducted four expeditions to Greenland to study its atmosphere and ice cap. On the second expedition, he completed the longest crossing of an ice cap ever made on foot (750 miles). The fourth expedition, in 1930, was to establish three weather stations on the island. One station on the west coast was set … Read more

Once scientists realized that fossils were a key to uncovering Earth’s past, the search was on for more, older fossils. Three main new sciences grew out of these studies, paleontology, archaeology, and anthropology. Paleontology is the study of fossils, including those of humans, animals, and plants. Archaeology is the study of past human culture and … Read more

There are four main developments in human evolution that led to today’s Homo sapiens: walking on two legs instead of four; a larger, more complex brain; the making of tools; and language. The development of all but language could be revealed by studying fossils of hominids, members of the family that include humans and apes. … Read more

In the nineteenth century, scientists discovered that Earth was much older than previously thought. Humans and other animals had been on Earth much longer also. Some animals had lived on Earth before humans and become extinct. This raised many questions. How old was Earth? When did life start? When did humans appear? In 1925, Australian … Read more

Just as Alfred Wegener was getting his degree in astronomy, the new science of meteorology was getting a boost from some new scientific advances. The telegraph, the laying of the Atlantic cable, and wireless communications were making storm tracking and weather forecasting much more accurate. Wegener became a meteorologist. He used kites and balloons to … Read more

Some of the instruments used by the scientists on the Challenger expedition were remarkably simple. Measuring the depth of water is called sounding. Their sounding device was simply a very long rope with a heavy weight (over 100 pounds) attached to the end. The machine lowering the rope had a counting wheel to record the … Read more

The H.M.S. Challenger returned to England on May 24, 1876. All the oceanographic findings of the Challenger expedition would take 20 years to compile into 50 volumes and almost 30,000 pages. Charles Wyville Thomson was able to complete a two-volume account of the main findings before his death in 1882. The most remarkable discovery of … Read more

Alfred Wegener was so sure of his theory on the origin of the continents that he gave the original continent a name, Pangaea, which means “all of Earth” in Latin. In his research, he found much more support for the theory, in addition to the fossil findings in Greenland. Wegener created a map of Pangaea … Read more

In 1596, the Flemish mapmaker Abraham Ortelius proposed a strange theory. He suggested that all the continents of Earth were once joined together and had drifted apart over the course of time due to earthquakes and floods. He offered no evidence other than that the coastlines of Africa and South America seemed to fit together … Read more

Without the ultimate proof of the force behind continental drift, Alfred Wegener’s theory was rejected by most as a fairy tale. The first hint of proof came right after Wegener’s death, with the confirmation of the submerged mountain range called the Mid-Atlantic Ridge under the Atlantic Ocean and a central valley along its crest. Wegener … Read more

People had some strange ideas about fossils when they were first discovered. Some thought that dinosaur bones were the remains of a race of human giants. Even when it became clear that the fossils were the remains of strange, previously unknown animals like mastodons, some thought these animals must still exist in unexplored areas of … Read more

Some cosmologists have taken Stephen Hawking’s work and proposed that the same black hole process that formed our universe may have occurred more than once to form other universes. They say that structures called wormholes might connect our universe to others. These same wormholes might connect different parts of our universe that are millions of … Read more

Like Albert Einstein, Stephen Hawking hopes for “a complete, consistent, and unified theory of the physical interactions which would describe all possible observations”, a theory for everything. Sometimes there are contradictions in science’s greatest breakthroughs. For example, Newton’s theories explained gravity and motion, and Maxwell’s theories explained radiation, but the two could not agree on … Read more

One night, Cuvier’s students decided to play a trick on their professor. They dressed up in devil’s costumes and woke up Cuvier in the middle of the night, chanting, “Cuvier, Cuvier, we have come to eat you!” Cuvier opened his eyes and took a good look at his pretend attackers. He said, “All animals with … Read more

Before Charles Darwin came up with his theory of evolution in 1859, biologists debated how to explain the similarity and diversity among animals, and Georges Cuvier was right in the middle of the debate. Cuvier was brilliant at anatomy, but he made the mistake of dismissing evolution. Both of France’s other leading biologists at the … Read more

A few scientists before Georges Cuvier believed that fossils were the remains of species that no longer existed, but religion was still a powerful force in science in Cuvier’s time. Many scientists could not believe that God would create living things only to wipe them out later. Cuvier decided to settle the issue. For his … Read more

Charles Darwin took a copy of Charles Lyell’s Principles of Geology with him on his around the world research voyage aboard the HMS Beagle. Darwin was just beginning to formulate his ideas on evolution, and Lyell’s findings would have a deep influence on him. There’s little doubt that Lyell’s basic belief that Earth had undergone … Read more

In 1650, Archbishop James Ussher of Ireland used the history of Earth presented in the Bible to calculate that the world had been created in 4004 B.C. If this were true, how could fossil formations be explained? More and more fossils of plants and animals were being uncovered in thick layers of rock. Sometimes the … Read more

Charles Lyell was born into wealth in Kinnordy, Scotland, in 1797. His father was a skilled botanist, and Lyell, growing up on the family’s huge estate, acquired a love for the natural world. His family decided, however, that he would study law at Oxford because science was not considered a “gentleman’s” profession. Lyell completed his … Read more

In 1795, the Scottish geologist James Hutton wrote a book called Theory of the Earth. Hutton had a new theory about how Earth formed. He said Earth was probably millions of years old. Hutton rejected Cuvier’s catastrophism and said changes had occurred slowly over these millions of years from simple forces, like erosion and sedimentation, … Read more

The British government provided Charles Wyville Thomson with the HMS Challenger warship for the Challenger expedition. It was a 200-foot sailing ship, but it was equipped with a 1,200-horsepower engine to power dredging experiments. All but two of the ship’s 18 guns were removed and replaced with scientific laboratories and storage space. The ship had … Read more

Who Was Sir Charles Wyville Thomson and How Did the Challenger Expedition Help Advance Oceanography? For thousands of years, humans navigated the open seas with very little idea of what lay beneath them. By the late nineteenth century, humans knew more about the universe and the atom than Earth’s oceans. Early studies of the oceans … Read more

Charles Lyell’s most unusual idea in his book “Principles of Geology” was that the pattern of life on Earth might occur in cycles. Some fossil discoveries were already revealing evidence that huge reptiles, later named dinosaurs, roamed Earth long before humans had. According to Lyell’s idea of cycles of life, these reptiles might return one … Read more

The scientists on board the Challenger were experts in biology, chemistry, geology, and physics, and Charles Wyville Thomson’s plan for the voyage was very ambitious. They would record data and collect samples at 362 observation stations around the world. Here’s a list of the observations and experiments that were performed at most stations: The depth … Read more

The skies are full of variable stars. These are stars that go through a cycle of fading and brightening, so they look like they’re winking. Cepheid variables have very quick cycles, some as short as 12 hours. In 1912, American astronomer Henrietta Leavitt discovered a connection between a Cepheid’s cycle and its brightness: the slower … Read more

At the start of the twentieth century, the perception of the universe was still limited to Earth’s own Milky Way system, which scientists thought measured no more than 20,000 light-years across. William Herschel had theorized 100 years earlier that there were other separate systems far outside our own, but most astronomers doubted this. There were … Read more

After Edwin Hubble’s galactic discoveries, many scientists felt that for the first time in history we understood the key elements of the structure of the universe. In 1922, the Russian mathematician Alexander Friedmann used Einstein’s theory of relativity and Hubble’s theory of an expanding universe to propose the big bang theory to explain the origin … Read more

Edwin Hubble’s study of galaxies led him to a classification system based on shape and composition into regular and irregular forms. He found that 97 percent of the regular galaxies had elliptical or spiral shapes. He divided spiral galaxies into two types: normal and barred. The arms of a normal spiral stretch out from a … Read more

If Hubble’s law proves correct for the entire universe, it will help us estimate the age and size of the universe. In fact, the radius of the measurable universe is called the Hubble radius. There is one problem, however. The galaxies in the outer reaches of the universe move faster and faster. Astronomers have detected … Read more

In the nineteenth century, astronomers discovered that studying the light emitted from a star, a study known as spectrum analysis, revealed what elements stars are made of. Changes in a star’s spectrum indicate the movement of the star, and analysis could determine the star’s speed and direction. It was revealed that stars only appear fixed … Read more

Vera Rubin was not the first astronomer to suggest that there is invisible matter in the universe. In the 1920s, the Dutch astronomer Jan Hendrik Oort found that the velocity of stars in our own Milky Way did not conform to Newton’s laws of gravity. However, he thought that the problem was in his observations … Read more

The big bang theory states that the present universe was born in an incalculable explosion of matter and gas. Albert Einstein had proposed the idea early in the twentieth century, and Hubble’s discoveries about galaxies seemed to confirm it. Vera Rubin’s next discovery would raise questions about the theory. The big bang theory predicted that … Read more

Rubin’s first discovery was amazing for several reasons. When she made it, she was still just a 22-year-old student from the virtually unknown graduate department at Cornell. When she presented her findings to the American Astronomical Society in 1950, she was practically booed off the stage. Several years after her presentation, however, her findings would … Read more

Vera Cooper Rubin was born in Philadelphia, Pennsylvania, in 1928 and knew from a very early age that she wanted to study the stars. She built her own telescope at 14 and attended Vassar College because her heroine, astronomer Maria Mitchell, had founded the astronomy department there. There were so few graduate schools that accepted … Read more

Hawking believes that the conditions in a black hole are the key to our entire universe and the big bang theory. In a black hole, matter collapses into an infinitely dense, infinitely small point. Hawking says that if you reverse the process, you have an infinitely dense, infinitely small point, surrounded by nothingness, exploding outward … Read more

In the 1960s, English mathematician Roger Penrose came up with the idea of singularity. A singularity occurs when an object becomes smaller and smaller from being crushed but does not lose any matter. Even the atoms and subatomic particles are crushed. The process continues indefinitely until the object is infinitely small and infinitely dense. Astronomers … Read more

By the 1960s there were two theories that tried to explain the origin of the universe. The big bang theory said that there was an immense explosion 12 to 20 billion years ago and that the universe was still expanding outward from that explosion. Astronomers who believed in the big bang said the movement of … Read more

In the 1970s, Vera Cooper Rubin started what seemed like an innocent experiment with another American astronomer, Kent Ford. Rubin wanted to determine why spiral galaxies differ in structure. She decided to compare the movements of stars near the center of a galaxy with those in the outer reaches of the galaxy. Rubin chose the … Read more

By 1781, Herschel had become an expert telescope maker and had built the most powerful telescope in the world. One night while he was working on his catalog of the stars, he saw something near the constellation Gemini that he hadn’t seen before. He could tell it was not a star from its movement, so … Read more

The key to William Herschel’s discoveries was his telescopes. His desire to see farther and farther into space meant that he had to become an expert in optics as well as astronomy. By 1779, he had built the best collection of telescopes in the world. His best was a 7-foot instrument with a 6-inch mirror … Read more

After William Herschel’s discovery of Uranus in 1781, astronomers studied the new planet carefully, but something was wrong with its orbit. It went wildly off track, and some scientists even started to question Newton’s laws of gravity. The mystery remained unsolved until 1846, when another planet was discovered in orbit beyond Uranus. English astronomer John … Read more

It’s hard to top the discovery of the first planet since ancient times, but William Herschel’s next observation was so amazing that few astronomers believed it until it was proven 150 years later. As telescopes became more sophisticated, astronomers began to see misty objects much farther away that were definitely not stars. They came to … Read more

After William Herschel proposed his theory of “island universes”, or galaxies lying far outside our own Milky Way, astronomers became curious about measuring the distance to the stars. In 1838, the German astronomer Friedrich Bessel used improved telescopes and a technique called parallax to prove that the universe was much more vast than even Herschel … Read more

In 1609, Jacques Badovere wrote a letter to his former teacher telling him of an amazing new instrument from Holland called a “Dutch cylinder.” With one convex lens placed in front of one concave lens inside the cylinder, the instrument made distant objects appear much closer. Ships miles away at sea could be seen approaching … Read more