Transcript: Newton’s master work is the universal law of gravity. Newton’s law of gravity states that every object in the universe, every particle, every planet, every star, every galaxy, attracts each other with a force that is proportional to each of the masses of two objects and inversely proportional to the square of the distance between them. The constant in this equation is the gravitational constant. Thus, if you have two objects in space and double the distance between them the...

Transcript: Tycho Brahe is one of the most colorful characters in the history of astronomy. He was born into an extremely poor family and at a young age was essentially bought by his uncle, a nobleman, and so he grew up in wealth. Then, as a teenager he was lucky enough to rescue the king of his country and so received a handsome stipend with which he set up a fantastic observatory on an island off the coast of what is now Sweden. Brahe’s careful and meticulous observations over twenty...

Transcript: We tend to think of the Renaissance in terms of developments in art and sculpture in the 15th century, mostly in Italy. But the Renaissance had its start several hundred years earlier in the 13th century, and it really started in Spain with the rediscovery of ancient Greek manuscripts and the Greek philosophers’ knowledge. Renaissance in fact means rebirth or rediscovery. In Toledo, in Spain, around 1100 AD translators working in large schools were recovering the Greek...

Transcript: With the decline of Greek civilization also came the decline of science. The next dominant civilization were the Romans, and the Romans were little interested in pure science, being more interested in practical matters such as agriculture and creating the bureaucracy of their huge empire. Several events from the fourth century AD symbolized the decline of science. One was the sacking of the great library at Alexandria and the horrible loss of knowledge represented by that event....

Transcript: Looking at the distances of the planets from the sun, it’s easy to see that they are neither uniformly spaced nor randomly spaced. In fact the distance of the planets from the sun follow a geometric progression where each is one and a half to two times further out than the one before. This was noticed in the late 18th century by Bode and Titius, and it forms what is called Bode’s rule. At the time of the discovery of Uranus it fitted the progression by being roughly twice the...

Transcript: Too often science is treated in isolation from other human pursuits. However the broad history of ideas from the time of Copernicus to the time of Newton parallels a similar evolution in the arts in Europe at that time period. The popular cliché goes that science is pure analysis, or reductionism, or taking the rainbow to pieces, whereas art is pure synthesis, or putting the rainbow together. This makes an unnatural division between science and the arts. Thinkers as great as...

Transcript: Ptolemy was a scholar at the Alexandrian library in Egypt. Little is known about him. He wrote around the year 140 AD a vast encyclopedia of astronomy called the Almagest which means “the greatest.” This was the compendium that would carry forward through the next millennium as astronomy moved through Europe. He created a star catalog with over one thousand stars, and he propagated the geocentric model of Aristotle that was the standard cosmology for his day and for another...

Transcript: The Greek geocentric cosmology of Aristotle, as propagated by Ptolemy, was highly complex in trying to explain the motions within the solar system. Because the planets do not have uniform motion, the model needed the centers of their motion to be displaced from the Earth. Because Mars, Jupiter, and Saturn display retrograde motion, or occasional backward motion on the sky, they had to have epicycles inserted on their orbits. All in all, the Ptolemaic model was extremely complex...

Transcript: The Copernican revolution and the invention of the telescope opened up people’s ways of thinking about the universe. The universe now became a very large place in the heliocentric model because the stars must be very far away compared to the distance between the Earth and the sun. In addition, Galileo’s observations of mountains on the moon and of planets themselves that had objects in orbit around them, the moons of Jupiter, showed that there were worlds within space and led...

Transcript: Science proceeds by making observations that discriminate between rival hypotheses. Galileo’s observations of the phases of Venus were decisive evidence in favor of the heliocentric model. In the geocentric model the fact that Venus has always seemed close in the sky to the sun is explained in terms of an epicycle. As Venus moves on its epicycle it is always between the sun and the Earth, thus the phases of Venus do not change substantially since Venus always has its sunlight...

Transcript: Parallax is the shift of angle when something is observed from two different perspectives. If you hold your finger out in front of your face and observe it with one eye and then the other you will notice the shift, or the parallax shift, relative to a distant backdrop. This angular shift becomes a way of measuring distances in astronomy. The parallax angle depends on distance. If you take the finger in front of your face and move it to a larger distance the parallax angle goes...

Transcript: Newton’s third law of motion says that for every force there is an equal and opposite force. This is sometimes called the principle of action and reaction. For example, when you sit on a chair you exert a downward force due to gravity, but if the chair does not move or break the chair is exerting an upward force to support you. A rocket is another example of action and reaction. The forward motion of the rocket is countered by an equal force backwards that propels the exhaust...

Transcript: Newton’s second law of motion mathematically relates a force to the change of motion that it causes. Newton’s law says that an object is accelerated when a force is applied to an object with an acceleration that is proportional to the force and in the direction of the force and inversely proportion to the mass: F equals M A. Imagine you push on a shopping cart. The mass is low, and so the inertia or resistance to a change in motion is low, and thus the shopping cart will suffer...

Transcript: One of the things Newton is famous for is his understanding of the laws of mechanics and his development of three laws of motion. The first law is that an object continues in its present state of motion unless acted on by an external force. This is the concept of inertia. The second law is that an object is accelerated when an unbalanced force is applied to it, with acceleration proportional to the force and inversely proportional to the mass: F equals M A. The final law is...

Transcript: Newton’s first law of motion says that an object will stay at rest or in uniform motion unless an unbalanced force acts on it. Newton’s first law is a major departure from Greek physics which stated that rest was the natural state of an object. Newton realized that when an object subject to friction, such as a light thing falling through the Earth’s atmosphere or an object rolling on the surface, when such an object slowed down it was because it was subject to a force that...

Transcript: Perhaps the greatest scientist who ever lived, Isaac Newton was born just after the death of Galileo. Lonely and moody as a child, his early education was unremarkable, but when he went to university at Cambridge his true intelligence came forth. During a torrent of creativity between the years of the plague years when he was age 23 to 25 Newton developed the theory of calculus, the science of optics, developed an understanding of the properties of light, and the properties of...

Transcript: Newton’s work was central not only to the history of physics and astronomy but to the history of ideas of Europe in the last 400 years. Newton’s innovations in mechanics led to ways of harnessing energy and power in machines, and this within a few generations led to major inventions of the industrial revolution in England. Newton’s idea of gravity led to the notion of a clockwork universe where the law of gravity could be used to predict the motion of objects in space. This idea...

Transcript: The idea of space exploration is a direct development from the ideas of Newton. Nearly 300 years before the invention of the rocket Newton had speculated as to how an object might be launched into Earth orbit. This is how he did it. In his book the Principia he imagined being positioned on top of a high mountaintop, high enough to be above the Earth’s atmosphere and so not subject to friction or air resistance. He imagined a cannon pointed sideways from the mountaintop. As...

Transcript: Newton was the first person to develop a basic understanding of the nature of light. In a famous experiment, he admitted sunlight through a hole in the shutters in his bedroom and dispersed the light with a prism into the colors of the rainbow. But Newton wondered, were the colors fundamental or not? So he inserted a second prism on one of the colors and tried to spread those rays of light out even further but was unable to do so thereby proving that the individual colors could...

Transcript: A basic concept in mechanics is momentum. Momentum is a measure of inertia and is proportional to velocity of an object. Momentum is calculated by multiplying the mass times the velocity. Momentum is conserved in any interaction between objects. We can see examples of this in a rocket at work where the forward momentum of the rocket represents a modest velocity of a large amount of mass, and that equals the huge velocity of the exhaust gasses representing a smaller amount of...

Transcript: In the thirteenth century Aristotle’s work was rediscovered and merged with Christian thought by Thomas Aquinas in a synthesis that would define cultural world view of that period of European history. In the Aquinas view the world had a fixed and static social order in which humans were the pinnacle of creation, and the celestial sphere was the realm of God. The two were not related. Scientific inquiry of the heavens was not a high priority under this theology.

Transcript: Some of the most important ancient advances in astronomical knowledge came within Central and South America, in particular from the Mayan culture. Around the year 400 AD, when Europe was slipping into the dark ages, Mayan astronomy was at its peak. Mayan records recorded the phases of the moon, eclipses, motions of the planets, and they had an extremely accurate calendar. Mayan astronomy was well regulated and supported by the state. In the Mayan calendar the year starts on...

Transcript: People use the words interchangeably, but there is a big difference between the concept of mass and the concept of weight. Mass is the amount of stuff in an object, or the number of atoms, measured in units of kilograms. Weight however is the response of an object to a gravitational field, and it depends on your location in space or in the universe. On the surface of the Earth the acceleration due to gravity is 9.8 meters per second per second, and that gives objects their...

Transcript: Kepler deduced three laws of planetary motion that are applied to all the objects in the solar system. The first law says that the planets move in elliptical orbits with the sun at one focus. There is nothing at the other focus of the ellipse. We characterize an ellipse in terms of the semi-major axis. When the ellipticity, or amount by which the ellipse is squashed, goes to zero the ellipse turns into a circle and the semi-major axis into the radius. The second law says that...

Transcript: Johannes Kepler inherited Tycho Brahe’s meticulous observations and as a skilled mathematician knew exactly what to do with them. After eight years and thousands of pages of analysis he reluctantly concluded that the planets could not be explained with circular orbits but only by elliptical orbits. It was a reluctant conclusion because Kepler was in awe of the Greeks and was well aware that the sphere and the circle were the most perfect figures. However, he listened to what...