(MUSIC)
JOAN CARTAN-HANSEN, HOST:

SCIENTISTS HAVE SPECIAL TERMS
FOR MEASURING VERY SMALL AND

VERY BIG DISTANCES.

A MICRON IS ONE MILLIONTH OF A
METER.

SOME BACTERIA ARE A FEW
MICRONS ACROSS.

A NANOMETER IS ONE BILLIONTH
OF A METER.

THE DNA INSIDE THE CELLS OF
YOUR BODY ARE ABOUT TWO

NANOMETERS ACROSS.

A PICOMETER IS ONE TRILLIONTH
OF A METER.

A HYDROGEN ATOM IS ABOUT 25
PICOMETERS ACROSS.

IN SPACE, DISTANCES ARE SO
VAST THAT WE MEASURE THEM IN

ASTRONOMICAL UNITS AND LIGHT
YEARS.

ONE ASTRONOMICAL UNIT OR A-U
EQUAL 93 MILLION MILES, THE

DISTANCE FROM THE EARTH TO THE
SUN.

SO, MARS, FOR EXAMPLE IS 1
POINT 5-2 ASTRONOMICAL UNITS

FROM THE SUN.

A LIGHT YEAR IS HOW FAR LIGHT
TRAVELS IN ONE YEAR.

A LIGHT YEAR IS 60 THOUSAND
ASTRONOMICAL UNITS.

THE SUN'S CLOSEST STAR IS
ALPHA CENTAURI AND IT'S 4

POINT 4 LIGHT YEARS AWAY.

FOR MORE INFORMATION ABOUT
MEASUREMENT, CHECK OUT THE

SCIENCE TREK WEBSITE.

YOU'LL FIND IT AT SCIENCE TREK
DOT ORG.