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100 Greatest Discoveries in Science Video Guide
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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.
1. What did Aristotle believe about the rate of falling objects?
2. How is air resistance a factor when testing the rate of falling objects?
3. Why was Galileo’s challenge to Aristotle’s law a turning point in science?
4.What happened when the feather and hammer were dropped on the moon where there is no air
resistance?
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.
5. What is the legend of Isaac Newton and the apple?
6.What is the law of universal gravitation?
7.How are tides created on Earth?
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.
8.Why are Newton’s laws so important?
9.What is Newton’s 1st law of motion?
10.What is Newton’s 2nd law of motion?
11.What is Newton’s 3rd law of motion?
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.
12._______ energy can be turned into the energy of _________.
13. What is the second law of thermodynamics?
I
14.How much of the energy from gasoline is actually used to move the car and passengers? Where does
the rest of it go?
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.
15.What did Michael Faraday do in 1831 that is now the basis of all generators?
16.Why was Bill Nye safe inside the cage when it was hit by a lightning bolt?
17.How would the world be different without the work of Faraday and James Maxwell?
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.
18.How was Einstein’s view of time and space different than Newton’s view of time and space?
19.Describe the “twin paradox.”
20.The ________ you move, the _______ time beats.
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.
21.The _____ you move, the _______ you get.
22.What does each letter stand for in this equation?
23.Why was this discovery so important in science?
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.
24.Why was there a crisis in physics around 1900?
25.What are “quanta”?
26.Atoms are _________; atoms are ___________; and there are _______________ involved in them.
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.
27. What did the ancient people think the universe was made of?
28.What was Newton’s main contribution to the understanding of light?
29.How did Thomas Young understand light?
30.How did Einstein contribute to the understanding of light?
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.
31. How many atoms fit into a single grain of sand?
32.What is the “plum-pudding” model of the atom?
33.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?
34.Why was James Chadwick’s discovery of the neutron so important?
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.
35.What happens in a particle accelerator?
36.What happens to the electrical resistance of a metal when it is at very low temperatures?
37.What is the “holy grail” of superconductors, and why would this discovery be so important?
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.
38.What did Murray Gell-Mann propose that protons and neutrons are made of?
39. How did scientists first “see” quarks?
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.
40. What are the 4 fundamental forces of nature?
41.What does the strong nuclear force do? The weak nuclear force?
42. What is the “theory of everything”? Has anyone 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?
Mercury’s orbit could not be correctly predicted by Newton’s Laws of motion.
How can a trampoline help to explain the theory of general relativity?
A bowling ball in the middle sinks in the trampoline, and a marble will orbit around the bowling
ball because the trampoline is pushing the marble in certain directions. This shows that a large
mass warps space (and time).
How did observations taken during a solar eclipse help to prove Einstein’s theory of general relativity?
Pictures taken before, during, and after an eclipse show that light from stars was bent as the light
passes by the Sun.
8. The Universe Is Expanding (1924 – 1929) Edwin Hubble determines the distance to many nearby
galaxies and discovers that the farther they are from us, the faster they are flying away from us. His
calculations prove that the universe is expanding.
The “white nebulae” found by William Herschel turned out to be what we call today _________.
galaxies
A shift toward the blue end of the spectrum in the color of a star showed the star was moving
_____________________; a shift toward the red end of the spectrum in the color of a star showed the
star was moving _______________________.
closer to Earth, away from Earth
Edwin Hubble found that almost all stars showed a _____-shift, meaning that the universe is
_________________.
red, expanding
Measuring backwards from the expansion led astronomers to propose the _____________ theory where
a huge explosion started the universe expanding.
Big Bang
9. The Center of the Milky Way Emits Radio Waves (1932) Karl Jansky invents radio astronomy
and discovers a strange radio-emitting object at the center of the Milky Way. Jansky was conducting
experiments on radio wavelength interference for his employer, Bell Telephone Laboratories, when he
detected three groups of static; local thunderstorms, distant thunderstorms and a steady hiss-type static.
Jansky determines that the static is coming from an unknown source at the center of the Milky Way by
its position in the sky.
What did Karl Jansky’s static observations end up showing at the middle of the Milky Way galaxy?
A black hole
How were Jansky’s observations the start of a new kind of astronomy?
He was the first to use radio waves (which can’t be seen) to study astronomy.
10. Cosmic Microwave Background Radiation (1964) Arno Penzias and Robert Wilson discover
cosmic microwave background radiation, which they suspect is the afterglow of the big bang. Their
measurements, combined with Edwin Hubble's earlier finding that the galaxies are rushing away, make
a strong case for the big bang theory of the birth of the universe.
What were Robert Wilson and Arno Penzias trying to measure with the spare microwave antenna?
They wanted to measure the temperature of the gas halo around the Milky Way galaxy.
How is the steady state theory of the universe different than the Big Bang theory?
The steady state theory said that the universe had no beginning or end, and is always expanding.
How did the work of Wilson and Penzias help to support the Big Bang theory?
The “extra” 3-4 degrees measured by Wilson and Penzias showed energy that was left over from
the Big Bang theory.
11. Gamma-Ray Bursts (1969 – 1997) The two-decade-long mystery of gamma-ray bursts is solved by
a host of sophisticated ground-based and orbiting telescopes. Gamma-ray bursts are short-lived bursts
of gamma-ray photons, which are the most energetic form of light and are associated with nuclear
blasts. At least some of the bursts have now been linked with distant supernovae — explosions marking
the deaths of especially massive stars.
Contrast the understanding of gamma ray bursts in the 1960’s with today’s understanding of gamma ray
bursts.
In the 1960’s scientists believed that gamma ray bursts were caused by supernova explosions.
Today we believe that gamma ray bursts are very powerful and may have caused past extinctions
on the Earth.
Why was it so hard to study gamma ray bursts?
They happened so fast that they were over before scientists could get a telescope focused on that
area of space.
12. Planets Around Other Stars (1995 – 2004) Astronomers find a host of extrasolar planets as a
result of improved telescope technology and prove that other solar systems exist, although none as yet
resembles our own. Astronomers are able to detect extrasolar planets by measuring gravitational
influences on stars.
How do scientists look for planets orbiting other stars? Why can’t scientists look for the planet itself?
To find another planet, you watch the star to see if it wobbles (using the Doppler effect) due to
the planet’s gravitational pull on the star. Scientists don’t look for the planets because they don’t
create their own light and are very dim.
How many “extra solar” planets (planets outside our solar system) have been found so far?
Around 130
What qualities would a planet need to support life?
The star the planet orbits should be similar to our sun; the planet needs to have a temp that
allows liquid water.
13. The Universe Is Accelerating (1998 – 2000) Unexpectedly, astronomers find that instead of
slowing down due to the pull of gravity, the expansion of the universe at great distances is accelerating.
If these observations are correct and the trend continues, it will result in the inability to see other
galaxies. A new theory of the end of the universe based on this finding has been called the "big rip."
Why is the discovery that the universe expansion is speeding up so important?
The acceleration of the universe expansion doesn’t fit with our current understanding of how the
universe works.
What is one possible explanation for the accelerating universe expansion?
There may be some type of “dark energy” that causes the universe to expand faster and faster.
100 Greatest Discoveries in Science Video Guide
Chemistry
Discovery #1. Oxygen (1770s) Joseph Priestley discovers oxygen; later, Antoine Lavoisier clarifies the
nature of elements. Priestley produces oxygen in experiments and describes its role in combustion and
respiration. Then, by dissolving fixed air in water, he invents carbonated water. Priestley, oblivious to
the importance of his discovery, calls the new gas "dephlogisticated air." Lavoisier gives oxygen its
name and correctly describes its role in combustion. Lavoisier then works with others to devise a
chemical nomenclature, which serves as the basis of the modern system.
Ancient Greek philosophers believed that there were four basic elements. What were they? Which one
was underlying element that was responsible for the make-up of everything in the world?
Earth, air, fire, and water; air was the single substance responsible for the make-up of everything.
Describe Joseph Priestley’s famous experiment that showed a new kind of “air” or gas.
He heated a mercury compound and collected the gas produced by heating.
How did Antoine Lavoisier expand on Priestley’s discoveries?
He recreated Priestley’s experiment, but measured the masses of the substances. He called the
gas that was emitted “oxygen”.
Discovery #2. Atomic Theory (1808) John Dalton provides a way of linking invisible atoms to
measurable quantities like the volume of a gas or mass of a mineral. His atomic theory states that
elements consist of tiny particles called atoms. Thus, a pure element consists of identical atoms, all with
the same mass, and compounds consist of atoms of different elements combined together.
What was John Dalton’s great discovery?
Dalton discovered atomic weights, then developed the atomic theory that explained the
relationship between atoms and the elements.
Discovery #3. Atoms Combine Into Molecules (1811 onward) Italian chemist Amedeo Avogadro
finds that the atoms in elements combine to form molecules. Avogadro proposes that equal volumes of
gases under equal conditions of temperature and pressure contain equal numbers of molecules.
Why were the results of Joseph Gay-Lussac’s experiments so surprising?
When equal volumes of different gases were combined, he ended up with twice as much gas as
he expected.
How did Amadeo Avogadro help to make sense of Gay-Lussac’s results?
He realized that gases are not made of single atoms, but rather made of molecules (groups of
atoms).
Discovery #4. Synthesis of Urea (1828) Friedrich Woehler accidentally synthesizes urea from
inorganic materials, proving that substances made by living things can be reproduced with nonliving
substances. Until 1828, it was believed that organic substances could only form with the help of the
"vital force" present in animals and plants.
What was the 19th century view of organic substances?
Somehow they were different and inorganic molecules could not be used to make organic
molecules.
How did Friedrich Woehler’s production of urea help to change the views of scientists about organic
molecules?
Organic substances can be made from inorganic molecules. Both inorganic and organic
substances are both made of the same thing – atoms.
Discovery #5. Chemical Structure (1850s) Friedrich Kekule figures out the chemical structure of
benzene, bringing the study of molecular structure to the forefront of chemistry. He writes that after
years of studying the nature of carbon-carbon bonds, he came up with the ring shape of the benzene
molecule after dreaming of a snake seizing its own tail. The unusual structure solves the problem of how
carbon atoms can bond with up to four other atoms at the same time.
How was the structure of benzene different than the structure of most other chemicals being studied at
the time of Friedrich Kekule?
Benzene’s carbon atoms weren’t linked in a chain, but rather in a ring.
The study of carbon-containing compounds is called ________ chemistry.
organic
Why is the discovery of the benzene structure so important?
It opens up many new possibilities for chemical structures for new drugs and medicines.
Discovery #6. Periodic Table of the Elements (1860s – 1870s) Dmitry Mendeleyev realizes that if all
of the 63 known elements are arranged in order of increasing atomic weight, their properties are
repeated according to certain periodic cycles. He formulates the periodic table of the elements and
predicts the existence of elements that have not yet been discovered. Three of those elements are found
during his lifetime: gallium, scandium and germanium.
How did Mendeleev come up with his periodic table of elements?
He made cards with info on each known element, and then arranged them in 7 vertical columns
with elements in a column being similar to one another.
Why did Mendeleev get credit for the periodic table instead of the German chemist Lothar Meyer?
Mendeleev made risky predictions about new elements on the periodic table.
Discovery #7. Electricity Transforms Chemicals (1807 – 1810) Humphry Davy finds that electricity
transforms chemicals. He uses an electric pile (an early battery) to separate salts by a process now
known as electrolysis. With many batteries he is able to separate elemental potassium and sodium in
calcium, strontium, barium and magnesium.
How did Humphry Davy use electricity to study the chemical make-up of potash?
He melted potash, then ran an electrical current through the melted potash, producing pure
potassium.
Why is electrochemistry so important?
It led to the aluminum industry, production of semi-conductors, solar panels, LED displays, and
rechargeable batteries.
Discovery #8. Atoms Have Signatures of Light (1850s) Gustav Kirchhoff and Robert Bunsen find that
each element absorbs or emits light at specific wavelengths, producing specific spectra.
What new elements were discovered by Robert Bunsen and Gustav Kirkoff using their newly built
spectroscope?
Cesium and rubidium
How did Bunsen and Kirkoff figure out that there was sodium in the sun?
They used their spectroscope to look at sunlight, and found that two of the lines exactly matched
the lines produced by sodium in a Bunsen burner.
How is spectroscopy used today in astronomy?
It’s used to study the atmospheres of planets, to look for water, and to look for signs of life.
Discovery #9. The Electron (1897) J.J. Thomson discovers that the negatively charged particles
emitted by cathode ray tubes are smaller than atoms and part of all atoms. He calls these particles, now
known as electrons, "corpuscles."
What did J.J. Thomson find out about the electron in 1897?
He found out it was very, very small compared to known atoms.
How did a magnetic field affect the beam of electrons in the cathode ray tube?
The stream of electrons would bend when a magnet was brought near, showing that electrons had
mass.
What did Ernest Rutherford later discover about the atom?
He found that the nucleus of the atom has the positive charge in the atom, as well as most of the
mass of the atom.
Discovery #10. Electrons for Chemical Bonds (1913 onward) Niels Bohr publishes his model of
atomic structure in which electrons travel in specific orbits around the nucleus, and the chemical
properties of an element are largely determined by the number of electrons in its atoms' outer orbits.
This paves the way to an understanding of how electrons are involved in chemical bonding.
Describe Gilbert Lewis’s model of the behavior of atoms.
He explained that electrons were in shells around the nucleus; each shell has a limited number of
electrons. Compounds form when 2 elements give up or accept electrons from their outer shells.
Why was Lewis’s theory such an important breakthrough?
It allowed scientists to create millions of new compounds.
Discovery #11. Radioactivity (1890s – 1900s) Marie and Pierre Curie discover and isolate
radioactive materials. After chemically extracting uranium from uranium ore, Marie notes the residual
material is more "active" than the pure uranium. She concludes that the ore contains, in addition to
uranium, new elements that are also radioactive. This leads to the discovery of the elements polonium
and radium.
What did Henri Becquerel’s experiments show about uranium?
He found out that uranium was a mineral that produced radioactive rays.
What 2 new elements were isolated by Marie and Pierre Curie in their search for radioactive material?
Polonium and radium
How did Marie Curie’s experiments lead to her death?
She died from leukemia caused by radioactive poisoning.
What are the names given by Ernest Rutherford to the 3 types of energy given off when radioactive
elements decay (fall apart)?
Alpha particles, beta particles, and gamma rays
How has radioactivity been helpful for us?
Medical imaging, treatment for tumors, method to calculate age of earth, power source for space
craft to explore solar system, smoke detectors
Discovery #12. Plastics (1869 and 1900s) John Wesley Hyatt formulates celluloid plastic for use as a
substitute for ivory in the manufacture of billiard balls. Celluloid is the first important synthetic plastic
and is used as a substitute for expensive substances such as ivory, amber, horn and tortoiseshell. Later,
Leo Baekeland invents hardened plastics, specifically Bakelite, a synthetic substitute for the shellac used
in electronic insulation.
What is a plastic?
Plastics are polymers.
What are polymers?
Polymers are long-chains of carbon atoms.
What are the advantages of plastics?
Plastics can be molded, they can be very strong, they can be woven into fibers to make clothing.
Discovery #13. Fullerenes (1985) Robert Curl, Harold Kroto and Rick Smalley discover an entirely
new class of carbon compound with a cage-like structure. This leads to the discovery of similar tube-like
carbon structures. Collectively, the compounds come to be called buckminsterfullerenes, or fullerenes.
The molecules are composed entirely of carbon and take the form of a hollow sphere, ellipsoid, tube or
ring. Named for Richard Buckminster Fuller, the architect who created the geodesic dome, they are
sometimes called "buckyballs" or "buckytubes."
What did Richard Smalley, Harold Kroto, and Robert Curl discover that led to their Nobel prize?
They discovered a special form of carbon atoms called “bucky balls”.
What are some of the unique properties of bucky tubes?
They are stronger than steel or diamonds, but they can be stretched to great lengths.
What are some of the potential uses of bucky tubes?
Electrical cables that are lightweight and conduct electricity better than copper.
What is nanotechnology?
Building things from “scratch” (atoms and molecules) that are stronger and more precise than
what we have now