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 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 m = 0.01 m 1 millimeter = 1 mm … which is 1 x m = m 1 micrometer = 1  … which is 1 x m = m 1 nanometer = 1 nm … which is 1 x m = 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 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 = m 1000 millimeters in a meter, 10 millimeters in a centimeter 1 micrometer = 1 m … which is 1 x 10-6 m = m 1,000,000 micrometers in a meter, 1000 micrometers in a millimeter 1 nanometer = 1 nm … which is 1 x 10-9 m = 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.