Something surrounds you. Bombards you
some of which you can't see, touch, or even feel.  Everyday.
Everywhere you go.  It is odorless and tasteless.
Yet you use it and depend on it every hour of every day.
Without it, the world you know could not exist.
What is it?  Electromagnetic radiation.  These waves
spread across a spectrum from very short gamma rays,
to x-rays, ultraviolet rays,
visible light waves, even longer infrared waves,
microwaves, to radio waves which can measure longer
than a mountain range.  This spectrum is the foundation of
the information age and of our modern world.  Your radio, 
remote control, text message, television, microwave oven,
even a doctor's x-ray, all depend on waves within the electromagnetic spectrum.
Electromagnetic waves (or EM waves)
are similar to ocean waves in that both are energy
waves - they transmit energy.  EM waves
are produced by the vibration of charged particles and have electrical and
magnetic properties.  But unlike ocean waves that require water,
EM waves travel through the vacuum of space
at the constant speed of light.  EM waves have crests
and troughs like ocean waves.  The distance between crests
is the wavelength.  While some EM wavelengths are very long
and are measured in meters, many are tiny and are measured
in billionths of a meter...nanometers.  The number of these crests
that pass a given point within one second is described as
the frequency of the wave.  One wave - or cycle -
per second, is called a Hertz.  Long EM waves,
such as radio waves, have the lowest frequency
and carry less energy.  Adding energy increases the frequency of the wave
and makes the wavelength shorter.  Gamma rays are the shortest,
highest energy waves in the spectrum.  So, as you
sit watching TV, not only are there visible light waves
from the TV striking your eyes...But also radio waves transmitting from
a nearby station; and microwaves carrying cell phone calls and text messages;
and waves from your neighbor's WiFi; and GPS units in the cars driving by.
There is a chaos of waves from all across the spectrum passing
through your room right now!  With all these waves
around you, how can you possibly watch your TV show?  Similar to
tuning a radio to a specific radio station, our eyes
are tuned to a specific region of the EM spectrum and can detect energy
with wavelengths from 400 to 700 nanometers,
the visible light region of the spectrum.  Objects appear to have color
because EM waves interact with their molecules.
Some wavelengths in the visible spectrum are reflected and other
wavelengths are absorbed.  This leaf looks green because
EM waves interact with the chlorophyll molecules.
Waves between 492 and 577 nanometers in length
are reflected and our eye interprets this as the leaf being green.
Our eyes see the leaf as green,
but cannot tell us anything about how the leaf reflects ultraviolet, microwave,
or infrared waves.  To learn more about the world around us, 
scientists and engineers have devised ways to enable us to 'see'
beyond that sliver of the EM spectrum called visible light.
Data from multiple wavelengths help scientists study
all kinds of amazing phenomena on Earth,
from seasonal change to specific habitats.  Everything around us
emits, reflects and absorbs EM radiation differently
based on its composition.  A graph showing these interactions across a region
of the EM spectrum is called a spectral signature.
Characteristic patterns, like fingerprints within the spectra allow astronomers
to identify an object's chemical composition and to determine such
physical properties as temperature and density.
NASA's Spitzer space telescope observed the presence of water and organic molecules
in a galaxy 3.2 billion light years away.
Viewing our Sun in multiple wavelengths with the SOHO satellite
allows scientists to study and understand sunspots that are associated
with solar flares and eruptions harmful to satellites,
astronauts and communications here on Earth.
We are constantly learning more about our world and Universe
by taking advantage of the unique information contained in the different
waves across the EM spectrum
