Tour of the EMS 01 - Introduction

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