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What is the speed of light?

The constant speed at which light travels in a vacuum is 186,282.397 miles (299,792.458 kilometers) per second. A light-year is the distance that light travels in one year, about 5.9 trillion miles (94.6 trillion kilometers).

Sources: Illingworth, Valerie. The Facts on File Dictionary of Astronomy,3rd ed., p. 250; McGraw-Hill Encyclopedia of Science and Technology, vol. 10, p. 51.

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1. Chemists And Chemical Principles
   1. Who are some of the founders of modern chemistry?
   2. Who made the first organic compound to be synthesized from inorganic ingredients?
   3. Who is known as the founder of crystallography?
   4. When was spontaneous combustion first recognized?
2. Physicists And Physical Principles
   1. Who is generally regarded as the person who discovered the electron, the proton, and the neutron?
   2. What is the speed of light?
   3. What were some of the leading contributions of Albert Einstein?
   4. What is inertia?
   5. Who is generally regarded as the founder of quantum mechanics?
   6. Who is the founder of the science of magnetism?
   7. How is ''absolute zero" defined?
   8. Who invented the thermometer?
   9. What is the Kelvin temperature scale and how does it compare with Celsius and Fahrenheit scales?
   10. What is an adiabatic process?
   11. Why does a boomerang return to its thrower?
   12. Does water running down a drain rotate in a different direction in the Northern and Southern Hemispheres?
   13. What is a Leyden jar?
3. Chemical Elements
   1. What are the two most abundant chemical elements on Earth?
   2. Who developed the periodic table?
   3. What are the alkali metalls?
   4. What are the alkaline earth metals?
   5. Which elements are liquid at room temperature?
   6. What are the transition elements?
   7. What are some chemical elements whose symbols are not derived from their English names?
   8. Which elements have the most isotopes?
   9. Which chemical element is the most abundant one in the universe?
   10. What is heavy water?
4. Matter
   1. What are the four states of matter?
   2. What are the subatomic particles?
   3. How did the quark get its name?
   4. What are the characteristics of alpha, beta, and gamma radiation?
   5. Why is liquid water more dense than ice?
5. Light And Sound
   1. Is light made of waves or particles?
   2. Does hot water freeze faster than cold water?
   3. What are the colors in light?
   4. Why does the color of clothing appear different in direct light than it does under fluorescent lignt?
   5. What is the speed of sound?
   6. What causes the sounds that are heard in a seashell?
   7. What is a decibel?
   8. What is the Doppler effect?
6. Terms And Measurements
   1. What is the density of air?
   2. What are the gas laws?
   3. How did the electrical term "ampere" originate?
   4. What is a mole in chemistry?
   5. What is "STP"?
   6. How did the electrical unit "volt" originate?
   7. How did the electrical unit "watt" originate?
   8. What does half-life mean?