We have a sufficiently difficult problem to encompass in our imagination the universe known to us. Let us try for a moment to look at that from a far-off point of vantage, with eyes that telescope distances, and with a mind freed, if possible, from the prejudice of every-day dimensions. We see from that seat of the Gods great spaces in which bright bodies are moving in black space in apparent disorder. They seem to be subject to the complex influences of currents, swirls and eddies like bubbles in churning waters. Many of these millions of celestial bodies glow by their own light. Many of them are not self-luminous, but shine by light borrowed from a nearby glowing gem of great brilliancy. These occasionally pass into shadow and become faint ghosts illuminated by distant stars. But there are no great shadows as we conceive the night sky to be as viewed from the Earth. Everywhere celestial space is velvety dark and upon this black background we are seeing the gems of the universe from the far-off viewpoint that we have assumed in our imagination.

Looking back at the region where Earth is, an insignificant part of the whole, we see this solar system which also is a very minor part. It consists of a few bodies among millions. On close observation we see this planetary system - a number of planets revolving about the Sun which is just a mediocre star. Some of these planets have satellites attending them. Our eyes range over the universe and we see thousands of nebulae twisting themselves into balls, of course, infinitely slowly as measured by our ideas of time. Here and there bushy-tailed comets dash along in apparent independence. Star-clusters as viewed from the Earth spread out over great spaces as seen from this imagined point of view.

The millions of bright gems in this dark void differ greatly in size, shape, brightness, velocity, and direction of motion. The first glimpse gives the impression of chaos. Observations of a year or two reveal systematic motion here and there, such as in the rotations of bodies and the revolutions of their satellites. A century might include more than one complete journey of some comets over their eccentric pathways. It would reveal orderliness in our solar system and in some other places. A thousand years might show enough to make it seem safe to predict that all bodies were obeying certain laws which bound them in their paths and cemented their relationships. A thousand years of observation might change our impression of chaos into one of cosmos. But this period would be too short to detect progress in nebulae toward the spherical form that they seem to desire. If we could rid ourselves of the prejudice imposed by our experience as Earth-beings in time as well as in distance, we would then be ready to view the universe as a whole in our imagination.

Let’s investigate the landscape of the moon.

The landscape of the moon is remarkably different from any seen on earth. Only a very few places on earth have features that are at all like those on the moon. Does this mean that the methods used for determining the history of lunar landscapes are different from methods used for the earth?

Examine the landscape shown in Figure 1. The Imbrium Basin is the largest basin on the nearside of the Moon, with a diameter of 1160 kilometers (the South Pole-Aitken Basin on the farside is twice as large). The Imbrium Basin is also the second youngest basin on the Moon. Based on samples returned by Apollo 15, it formed about 3.85 billion years ago.

The Face of the Moon

The moon’s appearance; light and dark patches are interpreted as a face in Western culture; “the man in the moon”.

Look at the full moon with binoculars. You will see two major types of landscapes, one dark and the other much lighter. The light areas are generally called highlands or continents-although they are probably quite different from continents on earth. Close examination of the highlands in a photograph like that of Figure 2 shows that the light areas appear very rough because they are covered with craters of all sizes.

The word crater simply means a bowl shaped depression.

The dark areas are much smoother and lower than the highlands. They also contain fewer large craters. Early astronomers called these dark areas maria (MAH-ree-ah), the Latin word for seas, mistaking them for bodies of water like oceans on earth. You can be quite sure, even without high-powered telescopes, that there are no oceans on the moon. The ancient name remains, however, and in fact a new mare (MAH-ray, singular of maria) was named only recently. This area, which was photographed by the Ranger 7 spacecraft, was called Mare Cognitum, the Known Sea.

The extent of the universe as we see it through the telescope is inconceivably large, but it is so on account of our experience which is confined to much smaller dimensions. In other words, dimensions are not based on an absolute scale, but upon the scale of our experience. Furthermore, our experience arises solely through our senses which are admittedly limited and biased. We think of atoms, as we know them, as being small planetary systems far beyond the revealing power of the microscope. Who can say that the entire universe of which we are conscious is more than a complex atom of a still greater cosmos? Who can say what is large and what is small?