100 Greatest Discoveries in Science Video Guide Physics KEY
Discovery #1. The Law of Falling Bodies (1604) Galileo Galilei overturns nearly 2,000 years of belief in Aristotle’s idea that heavier bodies fall faster than lighter ones by proving that all bodies fall at the same rate.
What did Aristotle believe about the rate of falling objects?
Heavier objects fall faster than lighter objects.
How is air resistance a factor when testing the rate of falling objects?
Air resistance affects lighter objects more than heavier objects.
Why was Galileo’s challenge to Aristotle’s law a turning point in science?
It marked the beginning of testing the accepted laws of science through experimentation.
What happened when the feather and hammer were dropped on the moon where there is no air resistance?
Both objects hit the ground at the same time.
Discovery #2. Universal Gravitation (1666) Isaac Newton comes to the conclusion that all objects in the universe, from apples to planets, exert gravitational attraction on each other.
What is the legend of Isaac Newton and the apple?
Newton saw an apple fall from a tree, but he wondered why the moon stayed in the sky. He came up with the idea of gravity.
What is the law of universal gravitation?
All objects in the universe have their own gravitational force, so they “pull” on all other objects.
How are tides created on Earth?
Water in ocean near moon is pulled more than other water, causing a bulge in the water on that side.
Discovery #3. Laws of Motion (1687) Isaac Newton changes our understanding of the universe by formulating three laws to describe the movement of objects. 1) An object in motion remains in motion unless an external force is applied to it. 2) The relationship between an object's mass (m), its acceleration (a) and the applied force (F) is F = ma. 3) For every action there is an equal and opposite reaction.
Why are Newton’s laws so important?
They help explain the motion of all objects.
What is Newton’s 1st law of motion?
Object in motion stays in motion.
What is Newton’s 2nd law of motion?
Force equals mass times acceleration.
What is Newton’s 3rd law of motion?
Every action has an equal and opposite reaction.
Discovery #4. The Second Law of Thermodynamics (1824 – 1850) Scientists working to improve the efficiency of steam engines develop an understanding of the conversion of heat into work. They learn that the flow of heat from higher to lower temperatures is what drives a steam engine, likening the process to the flow of water that turns a mill wheel. Their work leads to three principles: heat flows spontaneously from a hot to a cold body; heat cannot be completely converted into other forms of energy; and systems become more disorganized over time.
______energy can be turned into the energy of ______.
Heat, motion
What is the second law of thermodynamics?
In any energy exchange, some energy is always wasted.
How much of the energy from gasoline is actually used to move the car and passengers? Where does the rest of it go?
About 20%; the rest goes to heating up pavement, tires, engine, etc.
Discovery #5. Electromagnetism (1807 – 1873) Pioneering experiments uncover the relationship between electricity and magnetism and lead to a set of equations that express the basic laws governing them.
What did Michael Faraday do in 1831 that is now the basis of all generators?
He used a moving magnetic field to create electricity.
Why was Bill Nye safe inside the cage when it was hit by a lightning bolt?
The 1.5 million volts of electricity creates a magnet around the cage that pushes the electricity all around the outside of the cage, and does not move to the inside of the cage.
How would the world be different without the work of Faraday and James Maxwell?
There would be no electricity, no radios, no TV, no cell phones, no satellites, no computers.
Discovery #6. Special Relativity (1905) Albert Einstein overthrows basic assumptions about time and space by describing how clocks tick slower and distances appear to stretch as objects approach the speed of light.
How was Einstein’s view of time and space different than Newton’s view of time and space?
In Newton’s world, space and time are always separated and fixed. Einstein said that time and space are connected, and not always the same.
Describe the “twin paradox.”
Send one twin into space on a rocket ship so he travels near the speed of light; when he returns he will be younger than the twin left on Earth.
The ______you move, the ______time beats.
Faster, slower
Discovery #7. E = mc2 (1905) Or energy is equal to mass times the speed of light squared. Albert Einstein's famous formula proves that mass and energy are different manifestations of the same thing, and that a very small amount of mass can be converted into a very large amount of energy. One profound implication of his discovery is that no object with mass can ever go faster than the speed of light.
The _____ you move, the ______you get.
Faster, heavier
What does each letter stand for in this equation?
E – energy m – mass c – speed of light
Why was this discovery so important in science?
It helped show us the potential power inside the atom.
Discovery #8. Quantum Theory (1900 – 1935) To describe the behavior of subatomic particles, a new set of natural laws is developed by Max Planck, Albert Einstein, Werner Heisenberg and Erwin Schrodinger. A quantum leap is defined as the change of an electron within an atom from one energy state to another. This change happens all at once, not gradually.
Why was there a crisis in physics around 1900?
New phenomenon were being discovered that went against Newton’s laws. Energy was coming out of nothing; particles were coming out of nothing.
What are “quanta”?
packets of energy
Atoms are ______; atoms are ______; and there are ______involved in them.
Waves, particles, uncertainties
Discovery #9. The Nature of Light (1704 – 1905) Thought and experimentation by Isaac Newton, Thomas Young and Albert Einstein lead to an understanding of what light is, how it behaves, and how it is transmitted. Newton uses a prism to split white light into its constituent colors and another prism to mix the colors into white light, proving that colored light mixed together makes white light. Young establishes that light is a wave and that wavelength determines color. Finally, Einstein recognizes that light always travels at a constant speed, no matter the speed of the measurer.
What did the ancient people think the universe was made of?
Earth, air, fire, and water
What was Newton’s main contribution to the understanding of light?
He found out that white light is really made up of all of the colors of the rainbow. He thought that light was made of tiny particles.
How did Thomas Young understand light?
Light was a wave.
How did Einstein contribute to the understanding of light?
“Duality” – light acts like both a particle and a wave.
Discovery #10. The Neutron (1935) James Chadwick discovers neutrons, which, together with protons and electrons comprise the atom. This finding dramatically changes the atomic model and accelerates discoveries in atomic physics.
How many atoms fit into a single grain of sand?
72 quintillion!
What is the “plum-pudding” model of the atom?
Electrons were spread throughout the inside of the atom.
What happened when Ernest Rutherford shot alpha particles at a sheet of gold? How did this discovery change the understanding of the structure of the atom?
He thought the particles would go straight through the gold, but some of the particles bounced straight back off the foil. He realized that there must be some part of the atom that is very dense, the nucleus.
Why was James Chadwick’s discovery of the neutron so important?
Neutrons were used as bullets to split the atom, leading to the nuclear age.
Discovery #11. Superconductors (1911 – 1986) The unexpected discovery that some materials have no resistance to the flow of electricity promises to revolutionize industry and technology. Superconductivity occurs in a wide variety of materials, including simple elements like tin and aluminum, various metallic alloys and certain ceramic compounds.
What happens in a particle accelerator?
Subatomic particles are accelerated to nearly the speed of light and then smashed into each other.
What happens to the electrical resistance of a metal when it is at very low temperatures?
As you lower temperature, resistance goes down smoothly; at about 4 K, the resistance drops to almost zero.
What is the “holy grail” of superconductors, and why would this discovery be so important?
To find material that is a superconductor at room temperature; everything that uses electricity would be much more efficient.
Discovery #12. Quarks (1962) Murray Gell-Mann proposes the existence of fundamental particles that combine to form composite objects such as protons and neutrons. A quark has both an electric and a "strong" charge. Protons and neutrons each contain three quarks.
What did Murray Gell-Mann propose that protons and neutrons are made of?
3 quarks each
How did scientists first “see” quarks?
Experiments where electrons were scattered off protons
Discovery #13. Nuclear Forces (1666 – 1957) Discoveries of the basic forces at work on the subatomic level lead to the realization that all interactions in the universe are the result of four fundamental forces of nature — the strong and weak nuclear forces, the electromagnetic force and gravitation.
What are the 4 fundamental forces of nature?
Gravity, electromagnetism, strong force, weak force
What does the strong nuclear force do? The weak nuclear force?
The strong nuclear force holds the nucleus force together. The weak nuclear force causes radioactive decay.
What is the “theory of everything”? Has anyone developed a successful “theory of everything”?
The theory of everything would unite all four forces into one super-force that existed at the beginning of time. No one has yet developed a successful “theory of everything.”
100 Greatest Discoveries in Science Video Guide Astronomy
1. The Planets Move (2000 B.C. – 500 B.C.) A thousand years of observations reveal that there are stars that move in the sky and follow patterns, showing that the Earth is part of a solar system of planets separate from the fixed stars.
Why is the Venus tablet of Amozogania important?
It’s the earliest record of a planet moving.
Describe the Greeks’ model of the solar system.
Planets move around the Earth.
2. The Earth Moves (1543) Nicolaus Copernicus places the sun, not the Earth, at the center of the solar system.
How was Nicolaus Copernicus’s model of the solar system different than the Greeks’ model?
The sun is the center of the solar system, and the Earth circled the sun like other planets.
Why was it so hard for people to accept his theory?
It didn’t feel like the Earth was moving.
3. Planetary Orbits Are Elliptical (1605 – 1609) Johannes Kepler devises mathematical laws that successfully and accurately predict the motions of the planets in elliptical orbits.
How was Johannes Kepler’s model of the solar system different than the models of Copernicus and the Greeks?
Planets did not move in circular orbits as Copernicus and the Greeks thought, but rather in an elliptical orbit.
Why was Kepler’s model so important?
It was the first system to accurately predict the movement of the planets.
4. Jupiter Has Moons (1609 – 1612) Galileo Galilei discovers that Jupiter has moons like the Earth, proving that Copernicus, not Ptolemy, is right. Copernicus believes that Earth is not unique, but instead resembles the other planets, all of which orbit the sun.
What were some of the things first seen by Galileo Galileo with his new telescope?
Mountains on the moon, star clusters of the Milky Way, Jupiter’s moons
How did Galileo’s discovery of Jupiter’s moons support Copernicus’s model of the solar system?
If moons could orbit Jupiter, then Earth could orbit the sun.
5. Halley's Comet Has a Predictable Orbit (1705 – 1758) Edmund Halley proves that comets orbit the sun like the planets and successfully predicts the return of Halley's Comet. He determines that comets seen in 1531 and 1607 are the same object following a 76-year orbit. Halley's prediction is proven in 1758 when the comet returns. Unfortunately, Halley had died in 1742, missing the momentous event.
What did people in the Middle Ages believe about the appearance of a comet?
It meant that something bad was going to happen.
Edmund Halley studied the orbits of comets and predicted that a particular comet (now named Halley’s Comet) would return in the year _____ and every _____ years after that.
1758, 76
Why Halley’s Comet a milestone discovery in astronomy?
A superstitious belief was replaced with a rational understanding of the universe.
6. The Milky Way Is a Gigantic Disk of Stars (1780 – 1834) Telescope-maker William Herschel and his sister Carolyn map the entire sky and prove that our solar system resides in a gigantic disk of stars that bulges in the center called the Milky Way. Herschel's technique involves taking a sample count of stars in the field of view of his telescope. His final count shows more than 90,000 stars in 2,400 sample areas. Later studies confirm that our galaxy is disk-shaped, but find that the sun is not near the center and that the system is considerably larger than Herschel's estimation.
What did William Herschel find as he counted the stars in particular sections of the sky?
First he found the planet Uranus. He also found that the Milky Way was much larger than people knew.
How did this discovery change the study of astronomy?
Our solar system is just an island in a huge universe.
7. General Relativity (1915 – 1919) Albert Einstein unveils his theory of general relativity in which he proposes that mass warps both time and space, therefore large masses can bend light. The theory is proven in 1919 by astronomers using a solar eclipse as a test.
Why did the orbit of Mercury puzzle Einstein and other scientists?