Day 2 – Units & Tour
If you want to understand Astronomy, then you
need to understand the units that are used by
astronomers. While the Americans continue to use
English measurements like inches, feet, miles,
virtually the rest of the entire world uses the metric
system, and ALL of the scientific community does
as well. Therefore, I am going to teach this course
in metric units. While some of you are already
familiar with the metric system, others may not, so I
want to get you on the same page.
The Metric System – small
The basic unit in the metric system is the
meter.
1 meter is 39.77 inches long … slightly
longer than a yard.
The front and back sides of yard sticks and
meter sticks are seen below.
The Metric System
There are lots of tiny markings on a meter stick, but
the key is knowing that the markings are done in
groups of 10.
There are 100 centimeters in a meter.
There are 10 millimeters in a centimeter, and
therefore 1000 millimeters in a meter.
A dime is about 1 millimeter thick.
The Metric System – small
As there are 10 millimeters in a centimeter, there
are 1000 micrometers in a millimeter.
So, there are 1,000,000 millimeters in a meter.
A red blood cell is about 7 micrometers wide.
The Metric System – small
As there are 1000 micrometers in a millimeter, there are
1000 nanometers in a micrometer.
So, there are 1,000,000,000 nanometers in a meter.
A DNA strand is 2 nanometers wide
The Metric System – small
Now, to learn the symbols for the small units of the metric
system
1 meter = 1 m
1 centimeter = 1 cm … which is 1 x 10-1 m = 0.01 m
1 millimeter = 1 mm … which is 1 x 10-3 m = 0.001 m
1 micrometer = 1 m … which is 1 x 10-6 m = 0.000001 m
1 nanometer = 1 nm … which is 1 x 10-9 m = 0.000000001 m
Okay, how are these units relevant to Astronomy?
The Metric System – small
We use the metric system to describe the properties and types
of “light.”
Light travels through space in the form of waves, and the
distance from one wave crest to the next crest determines the
form of that light.
The Metric System – small
The light that our eyes are accustomed to “seeing” is called
visible light and ranges in wavelength from 700 nm for the red
light to 400 nm for the blue light. The combination of all of the
waves of visible light (red, orange, yellow, green, blue, and
violet) makes white light.
The Metric System – small
Light comes in other forms. Longer waves of light travel as
Infrared … familiar as the form that you feel as heat, or that
you recall is how snakes see, how Sylvester Stallone saw with
special goggles in “Cliffhanger” and how the “Predator” looked
with awe at Arnold Schwarzenegger. Infrared waves are
measured in thousands of nanometers.
The Metric System – small
While you are used to thinking of telescopes seeing the
Universe in visible light, there are telescopes that can see
what the Universe looks like in the Infrared. Take a look at this
7 minute video about a new Infrared Telescope. I met Dr.
Thayer at an Astronomy conference, and she gave me this
teaching video.
The Metric System – small
Longer and longer wavelengths are found in microwaves (like
in the ovens of your homes) and in radio waves … which can
be hundreds or thousands of kilometers long.
The Metric System – small
Ultraviolet waves are 380 – 250 nanometers shorter and even
shorter than that, and are most familiar to you as the kind of
light that gives you cool tan lines like you see below and left.
The Metric System – small
X-rays are even shorter, measuring less than a nanometer,
and are most familiar to you as the kind of light that is used to
see through things.
The Metric System – small
Of course, x-ray glasses do not work. Only an x-ray machine
or Superman can “see” with x-ray vision. While UV rays can
give you a nice tan or cancer, x-rays are lethal in bigger doses.
The Metric System – small
The most energetic and dangerous waves are also the
shortest ones, called gamma rays. With wavelengths shorter
than 0.001 nanometers, they are exceedingly lethal. In the
history of mankind, only one person has ever survived a direct
exposure to gamma rays without dying.
The Metric System – small
In 1962, Dr. Bruce Banner was exposed to a burst of gamma
radiation while working on a secret project. However, instead
of dying from radiation poisoning he somehow lived, but the
cells of his body were forever altered in an unusual way.
The Metric System – small
Dr. Bruce Banner’s skin turned green, his muscled bulged, and
he developed a real nasty attitude.
The Metric System – small
So, let’s review:
1 meter = 1 m
1 centimeter = 1 cm … which is 1 x 10-1 m = 0.01 m
100 centimeters in a meter
1 millimeter = 1 mm … which is 1 x 10-3 m = 0.001 m
1000 millimeters in a meter, 10 millimeters in a centimeter
1 micrometer = 1 m … which is 1 x 10-6 m = 0.000001 m
1,000,000 micrometers in a meter, 1000 micrometers in a
millimeter
1 nanometer = 1 nm … which is 1 x 10-9 m = 0.000000001 m
1,000,000,000 nanometers in a meter, and 1000 nanometers in a
micrometer
There are smaller units too, like Angstroms and Picometers, but they are
not important for this Astronomy class.
The Metric System – small
So, in this class, please do your best to think, write, and speak
as scientists do … in metric. As you work through this lesson, I
hope that you will better be able to understand the world of the
very, very small. Now, it is time to look at the metric world of
the very BIG.