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- 1. The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in such areas is known as a physicist.
- 7. A minute amount of something.
- 8. The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which variation in values is possible. Also, the distance within which something can be reached or perceived.
- 12. High-energy radiation often generated by processes in and around exploding stars. Gamma rays are the most energetic form of light.
- 14. (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
- 15. (in biology) A type of eye cell that is part of the retina inside the back of the eye. These cells can sense red, green or blue light. And recent research has uncovered evidence that some can sense white light — but only white light.
- 16. (in biology) A type of eye cell that is part of the retina inside the back of the eye. These cells are rod shaped and sensitive to light. Although more sensitive to light than cone cells are, rods cannot tell what color something is.
- 18. The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
- 19. (in physics) To emit energy in the form of waves.
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- 2. (plural: spectra) A range of related things that appear in some order. (in light and energy) The range of electromagnetic radiation types; they span from gamma rays to X rays, ultraviolet light, visible light, infrared energy, microwaves and radio waves.
- 3. A disturbance or variation that travels through space and matter in a regular, oscillating fashion.
- 4. A type of electromagnetic radiation invisible to the human eye. The name incorporates a Latin term and means “below red.” Infrared light has wavelengths longer than those visible to humans. Other invisible wavelengths include X-rays, radio waves and microwaves. Infrared light tends to record the heat signature of an object or environment.
- 5. A portion of the light spectrum that is close to violet but invisible to the human eye.
- 6. A type of radiation analogous to gamma rays, but having somewhat lower energy.
- 9. Energy that travels as a wave, including forms of light. Electromagnetic radiation is typically classified by its wavelength. The spectrum of electromagnetic radiation ranges from radio waves to gamma rays. It also includes microwaves and visible light.
- 10. A constant often used in physics, corresponding to 1.08 billion kilometers (671 million miles) per hour.
- 11. The distance between one peak and the next in a series of waves, or the distance between one trough and the next. It’s also one of the “yardsticks” used to measure radiation. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves.
- 13. A particle representing the smallest possible amount of light or other type of electromagnetic radiation.
- 14. Referring to radio waves, or the device that receives these transmissions. Radio waves are a part of the electromagnetic spectrum that people often use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar. Many astronomical objects also radiate some of their energy as radio waves.
- 17. The star at the center of Earth’s solar system. It is about 27,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.