American History in the Planetarium

Figure 1: Paul Revere’s depiction of the Boston Massacre

Some of the richest resources of astronomical events and history are the articles of Dr. Donald W. Olson of Texas State University at San Marcos. He has written on an incredible number of topics, including this subject, published in the March 1998 issue of Sky and Telescope, which deals with the Boston Massacre.

The Boston Massacre occurred in 1770. Relations between the colonists and the occupying British troops were very strained, and on the evening of March 5 a group of angry townspeople gathered. They harassed the British guard outside the Town House on King Street, and at 9 PM the British called out more troops to handle the menacing group.

The crowd of colonists threw sticks, snowballs (it had snowed heavily the night before leaving a foot of snow on the ground), and ice at the soldiers. Captain Preston was in front of his men trying to restrain them from losing control, but eventually a shot was fired and then several others rang out haphazardly. When all was said and done, five colonists lie dead or wounded on the ground.

Figure 2: Old State House

The most famous engraving of this incident was made by Paul Revere and is shown in Figure 1.

There are several gross inaccuracies in this engraving as Revere was trying to incite anger and resentment against the British for this incident. (In fact, John Adams would eventually represent the soldiers accused of murder in this confrontation and because of his skill as a lawyer the court found them all innocent!)

Notice that Captain Preston is shown behind his men and they are firing orderly in a volley seemingly at his command. This is a fabrication. Also note that there is no snow on the ground.

The building in the center of the engraving is the Old State House (called the Town House at that time) and it still stands in Boston today along the Freedom Trail as shown in Figure 2. Especially note the strange looking “crescent” Moon in the upper left hand corner of the engraving in Figure 1.

Figure 3: Boston Massacre site with Old State House on left

Here is yet another strange depiction by Revere since the Moon never looks like this in the sky, i.e., a fat “crescent” Moon! Was this yet another fabrication by Revere to emphasize that the Massacre occurred at night, or was his depiction of the phase and placement of the Moon accurate?

To determine this we must first orient ourselves based upon his engraving. We are facing the end of the Old State House in Revere’s engraving. A search on Google Earth shows the orientation of the Old State House (due west from our vantage point in the engraving) and the red arrow shows the location of the Massacre and the direction (southwest) towards the Moon that he drew.

So, what remains for us to determine in the planetarium is what exactly did the Moon look like at 9 PM March 5, 1770 and where was it in the sky? How accurate was Revere in his astronomical depiction? Going to Boston, MA and the proper time and date leads us to the view shown in Figure 4.

Figure 4: 9 p.m. sky over Boston on March 5, 1770 (Moon enlarged for clarity)

We see the Moon is in the approximate position that Revere indicated. What is also interesting is that the approximate surface area depicted in his engraving is correct, although it’s really a waxing gibbous moon and not crescent. (It’s been known for a long time that artists typically drew the Moon as a crescent because it’s more esthetically appealing than a gibbous phase.)

So, although Paul Revere’s propagandist engraving was rife with inaccuracies in order to enrage the colonists, his depiction of the position and brightness of the Moon were fairly close (the crescent phase notwithstanding!).

This fairly bright Moon coupled with a foot of snow on the ground would have given the colonists and soldiers ample light in order to see exactly what they were doing in this most famous initial skirmish which helped lead to the American Revolution.

Using Distance Spheres for Illustrating Stars, Black Holes, and the Speed of Light

Figure 1: Stars added to Sun Distance Spheres

Distance Spheres included in Starry Night allow “Cosmic Zoom” sequences in our domes. However, I also use them to show audiences scale sizes of stars, the Milky Way’s supermassive black hole, and the speed of light.

In a previous article I described the upcoming “Stellar Sizes” minilesson from the Fulldome Curriculum Volume 2. This program compares the sizes of a dozen different stars to each other on the dome. Here’s another captivating way to illustrate stellar scales, but this time compared to the size of the Solar System on the dome making use of Distance Spheres in Starry Night Dome.

I’ve added new Distance Spheres centered on the Sun and made them the appropriate scale according to the sizes of the stars as given in Starry Night and the scientific literature. The stars added as Distance Spheres are shown in Figure 1.

Figure 2: Betelgeuse compared to the Solar System

We can easily add a star’s size to its label name, so as they appear in the dome, their sizes will also show.  I’ve colored them appropriately either by temperature or my prejudiced preference. It’s possible to change their opacities so that they look gaseous but you can also see planetary orbits through them, as shown in Figures 2 and 3 which show Betelgeuse and VY Canis Majoris (arguably the largest star known in the Milky Way).

I’ve also added the supermassive black hole that lurks at the center of the Milky Way, which is almost the same size as the star Arcturus. It’s very interesting to see how “small” this 4.3 million solar mass object is compared to the Solar System, as shown in Figure 4.

VY Canis Majoris compared to the Solar System

You can turn various spheres on and off in the dome via SciDome’s “QuickSphere” cue (QS) and or by loading various Starry Night files.

Another useful trick is hidden in a special Distance Sphere which is centered on the Earth, namely the time-varying Radio Sphere. The size of this sphere depends on the date you look at it as it’s expanding at the speed of light. The beginning point in time for this sphere is 12/12/1901 at 14:29:59 UT. So, I’ve set up a Starry Night simulation far enough away from the Earth to see the Moon’s orbit easily with the time stopped.

I tell my audience to watch carefully and they will see the light sphere expand away from the Earth in real time and reach the Moon’s orbit in 1.3 seconds, as seen in Figure 5.

Figure 4: Supermassive Black Hole of the Milky Way compared to the Solar System

You can also increase your elevation to encompass larger volumes of space to watch this sphere expand into the solar system. It’s educational to emphasize that, although light makes it to the Moon in slightly more than one second, it takes minutes to reach the planets, etc.!

I’ve found these to be great tricks for showing students the size of stars and our supermasive black hole compared to the size of our Solar System as well as illustrating the speed of light. I highly recommend that you play with this wonderful new tool in our SciDome teaching arsenal!

Figure 5: Light Sphere after traveling one second, almost to the Moon’s orbit