WEBVTT

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Something surrounds you. Bombards you

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some of which you can't see, touch, or even feel. Everyday.

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Everywhere you go. It is odorless and tasteless.

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Yet you use it and depend on it every hour of every day.

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Without it, the world you know could not exist.

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What is it? Electromagnetic radiation. These waves

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spread across a spectrum from very short gamma rays,

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to x-rays, ultraviolet rays,

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visible light waves, even longer infrared waves,

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microwaves, to radio waves which can measure longer

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than a mountain range. This spectrum is the foundation of

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the information age and of our modern world. Your radio,

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remote control, text message, television, microwave oven,

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even a doctor's x-ray, all depend on waves within the electromagnetic spectrum.

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Electromagnetic waves (or EM waves)

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are similar to ocean waves in that both are energy

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waves - they transmit energy. EM waves

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are produced by the vibration of charged particles and have electrical and

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magnetic properties. But unlike ocean waves that require water,

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EM waves travel through the vacuum of space

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at the constant speed of light. EM waves have crests

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and troughs like ocean waves. The distance between crests

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is the wavelength. While some EM wavelengths are very long

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and are measured in meters, many are tiny and are measured

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in billionths of a meter...nanometers. The number of these crests

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that pass a given point within one second is described as

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the frequency of the wave. One wave - or cycle -

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per second, is called a Hertz. Long EM waves,

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such as radio waves, have the lowest frequency

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and carry less energy. Adding energy increases the frequency of the wave

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and makes the wavelength shorter. Gamma rays are the shortest,

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highest energy waves in the spectrum. So, as you

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sit watching TV, not only are there visible light waves

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from the TV striking your eyes...But also radio waves transmitting from

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a nearby station; and microwaves carrying cell phone calls and text messages;

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and waves from your neighbor's WiFi; and GPS units in the cars driving by.

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There is a chaos of waves from all across the spectrum passing

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through your room right now! With all these waves

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around you, how can you possibly watch your TV show? Similar to

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tuning a radio to a specific radio station, our eyes

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are tuned to a specific region of the EM spectrum and can detect energy

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with wavelengths from 400 to 700 nanometers,

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the visible light region of the spectrum. Objects appear to have color

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because EM waves interact with their molecules.

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Some wavelengths in the visible spectrum are reflected and other

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wavelengths are absorbed. This leaf looks green because

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EM waves interact with the chlorophyll molecules.

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Waves between 492 and 577 nanometers in length

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are reflected and our eye interprets this as the leaf being green.

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Our eyes see the leaf as green,

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but cannot tell us anything about how the leaf reflects ultraviolet, microwave,

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or infrared waves. To learn more about the world around us,

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scientists and engineers have devised ways to enable us to 'see'

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beyond that sliver of the EM spectrum called visible light.

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Data from multiple wavelengths help scientists study

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all kinds of amazing phenomena on Earth,

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from seasonal change to specific habitats. Everything around us

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emits, reflects and absorbs EM radiation differently

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based on its composition. A graph showing these interactions across a region

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of the EM spectrum is called a spectral signature.

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Characteristic patterns, like fingerprints within the spectra allow astronomers

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to identify an object's chemical composition and to determine such

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physical properties as temperature and density.

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NASA's Spitzer space telescope observed the presence of water and organic molecules

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in a galaxy 3.2 billion light years away.

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Viewing our Sun in multiple wavelengths with the SOHO satellite

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allows scientists to study and understand sunspots that are associated

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with solar flares and eruptions harmful to satellites,

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astronauts and communications here on Earth.

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We are constantly learning more about our world and Universe

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by taking advantage of the unique information contained in the different

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waves across the EM spectrum