Happy anniversary, Einstein!
Brownian Motion and Atoms
"Albert Einstein was the first to come up with a way to measure the size of atoms," says White. How? He studied an unsolved mystery. In 1827, a botanist (plant scientist) named Robert Brown looked very closely at water droplets. He noted that tiny particles suspended inside--such as pollen or dirt--darted around in random, jerky movements. That movement was dubbed Brownian motion. But Brown couldn't figure out what caused the suspended particles to behave that way.
Although you can't see water molecules, Einstein theorized that they also are constantly in motion. The invisible water molecules that make up a water droplet are so small in size and mass (amount of matter in an object) that they can move very quickly. As the water molecules zip around, they knock the visible particles from place to place, creating Brownian motion.
Einstein showed that by studying Brownian motion, you could use math to calculate the size of atoms in water molecules. Later, other scientists tested Einstein's complex mathematical formula, and the convincing results helped erase doubts of the atom's existence.
"Any modern appliance or bit of technology--like a computer, TV, or laser--owes much of its workings to Einstein," he says. What exactly did Einstein discover in 1905, now dubbed the "miracle year"? Read on to find out.
"Einstein convinced people that while light acts like waves, it also comes as individual panicles of energy [later called photons]," says White. How? He explained a phenomenon called the photoelectric effect: When you shine a certain type of light beam on a metal plate, the light's energy causes the plate to eject electrons (negatively charged particles). But not all light beams produce this effect. Scientists who believed that light comes only as waves couldn't explain why.
Consider how light waves behave: A brighter beam of light has a higher wave crest (highest point on a wave) than a dimmer beam. That means brighter beams have more energy. Also, light with shorter wavelengths (more waves passing per second), like blue light, packs more energy than light with longer wavelengths--like red light. The puzzler: Why is it that a blinding red light hitting the metal plate doesn't send electrons flying, but a dim blue light does?
Einstein's theory: Forget brightness. That isn't the key to electron-ejecting power. Something hidden inside short-wavelength light--compared with long-wavelength light--must be punching more forcefully at the metal plate to kick out electrons. Einstein saw light as a stream of energy particles. Just as water coming from the tap is made of droplets, there are individual particles inside light called photons, says White. And each photon that makes up shorter-wavelength light has more energy than those of longer-wavelength light. So when these energy-packed particles hit the metal, electrons fly out. Thanks to photon know-how, "We have [inventions like] DVDs," says White.
Special Theory of Relatively
"Einstein may be most famous for his Special Theory of Relativity," says White. "But what he came up with was so stunning and weird that it was--and still is--hard for most people to understand." Here are the basics:
1. If you measure the speed of light, it will always be 300,000 kilometers (186,000 miles) per second--no matter how quickly you move toward the light source. That's fast. A beam of light can zoom across the United States in far less time than it takes you to blink your eyes.
2. Time is relative. How? Suppose you and your superhero pal have one thing in common: You two always devour candy bars at the same rate. One day, you choose to eat a candy bar while lounging on a hammock, and your pal chooses to eat the same type of candy bar while zipping through the sky at a high speed. When your superhero buddy lands next to you, he's shocked: Even though you both are at your normal rates, you finished eating at an earlier time than he did. How come? Einstein's reason: The faster an object moves, the slower time moves for it.
3. Points 1 and 2 led Einstein to come up with his famous formula: E = [mc.sup.2] (Energy = mass x speed of light squared). "When he started, Einstein had no idea that he would be discovering a new form of energy called mass energy," says White. He found that under the right conditions, even a tiny mass could be convertad into a lot of energy. Today, a device called PET (Positron Emission Tomography) scanner uses this concept to locate tumors in the body.
Learn more about Einstein and join the celebration of The World Year of Physics 2005 at: www.physics2005.org
DID YOU KNOW?
* Albert Einstein's explanation of the photoelectric effect won him the Nobel Prize for physics in 1921. Although Einstein has been hailed as one of the greatest minds of the 20th century, his school records were underwhelming. Einstein briefly dropped out of high school at age 15, and he graduated from university with unexceptional grades.
* The World Year of Physics 2005 invites middle school classrooms to participate in PhysicsQuest. This learning adventure encourages students to solve scientific mysteries in the same curious spirit that Albert Einstein did. By performing a set of experiments and solving puzzles, classrooms may qualify to earn national recognition and prizes. Only the first 10,000 classes to sign up will be able to participate in this free event. For more information or to sign up, visit: www.physics2005.org/events/physicsquest/index.html
* For a fun site about Einstein and physics, visit Einstein Year, Be sure to try the cool games, Go to: www.einsteinyear.org/
* To learn more about Albert Einstein's life, check out this time line from the American Institute of Physics: www.aip.org/history/einstein/
DIRECTIONS: On a separate piece of paper, defend or dispute the following statements. (Hint: Defend means to explain why a statement is correct. Dispute means to explain why a statement is incorrect.)
1. Albert Einstein helped prove the existence of atoms.
2. Einstein discovered that light only behaves like waves.
3. Einstein studied Brownian motion to discover the behavior of light.
4. The speed of light changes from second to second.
First, study "Happy Anniversary, Einstein!" on p. 12. Then, solve the clues below to complete this crossword puzzle. To spell out the bonus words, unscramble the letters in parentheses.
1. Albert Einstein's area of science expertise: --
2. The speed of--is about 300,000 kilometers (186,000 miles) per second.
3. The random, jerky movement of tiny particles suspended inside a water droplet is called --motion.
4.--are particles of two or more atoms joined together.
5. Because of Einstein's multiple discoveries in 1905, the year has been dubbed the--year.
6. A plant scientist is called a--.
7. An--is the smallest unit of an element.
8.--are negatively charged particles.
9.--describes the number of waves passing per second.
10. The formula E=[mc.sup.2] is part of Einstein's Special Theory of--.
11. Light is made up of individual particles of energy called--.
12. The--is the highest point on a wave.
BONUS: Einstein quotes
a. "If we knew what it was we were doing, it would not be called--, would it?"
b. "Imagination is--important than knowledge."
1. Defend: Albert Einstein helped prove the existence of atoms by explaining Brownian motion, or the jerky motion of particles inside a water droplet, Einstein theorized that water molecules, although you can't see them, are constantly in motion. The invisible water molecules that make up a water droplet are so small in size and mass that they can move very quickly As the water molecules zip around, they knock the visible particles from place to place, creating Brownian motion. Einstein showed that by studying Brownian motion you could use math to calculate the size of the atoms that make up water molecules.
2. Dispute: Einstein convinced people that while light acts like waves, it also comes as individual particles of energy called photons.
3. Dispute: Einstein's discovery of light behavior was a result of studying the photoelectric effect: When you shine a certain type of light beam on a metal plate, the energy from the light causes the plate to eject electrons.
4. Dispute: The speed of light is always about 300,000 kilometers (186,000) miles per second.
1. physics 2, light 3, Brownian 4. molecules 5. miracle 6. botanist 7. atom 8. electrons 9. wavelength 10. Relativity 11. photons 12, crest Bonus: a. research b. more
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|Title Annotation:||Physical Sience History|
|Date:||Jan 3, 2005|
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