We so often use the word “astronomical” when describing something so huge or vast that it is “inconceivable.” The Merriam-Webster definition of astronomical is, in fact, “enormously or inconceivably large or great.” Distances in space are so great that using miles or kilometers generates numbers so large they are unmanageable and unimaginable! So distance is measured in a light year. But how can we imagine this “inconceivable” distance?
The Light Year
The speed of light is a familiar number to most of us. Moving at 186,000 miles/sec (300,000 km/sec) means it travels 5.88 trillion miles (9.46 trillion km) in a year. Well, how can we imagine that distance? Sometimes it is a matter of using comparisons to more familiar objects and their measurements.
Self-taught American astronomer, Robert Burnham Jr., provides a useful set of comparisons. in his Celestial Handbook. He wrote and rewrote this series of books for amateur astronomers while working at the Lowell Observatory for over 20 years. In it, he shares his method for comparing the distance in light years to more familiar measurements.
Burnham begins with the Astronomical Unit (AU). This is the distance from the sun to the earth–approximately 93 million miles. The time it takes for light to reach the earth from the sun is approximately eight minutes. Okay. . .so far, so good!
In one of those quirky mathematical coincidences, there are about the same number of AUs in a light year as there are inches in a mile (63,000 AUs in a light year; 63,360 inches in a mile). Using this scale, if we imagine that one AU is one inch, then a light year is the equivalent of one mile! That puts the nearest star, Alpha Centauri, at 4 miles away from Earth and the center of the Milky Way Galaxy at 26,100 miles from Earth. (Putting the latter number in more familiar terms, the circumference of the Earth at the equator is just under 25,000 miles. It would take you almost 17 days to drive around the Earth at the equator at a steady speed of 62 m/hr.)
Another creative attempt to put into perspective the vast scale between the farthest reaches of the universe and the hidden smallness of the nucleus of an atom is found in a book written for school children: Cosmic View: The Universe in 40 Jumps.
The Cosmic View
In 1957 a book suggesting a project for school children appeared with the title Cosmic View: The Universe in 40 Jumps. Written by Kees Boeke, a Dutch educator, the book features 40 photographs, with the scale in each successive picture representing a “jump” to the next power of 10.
This is how Boeke describes the reason behind the project:
"We all, children and grownups alike. . . tend to forget how vast are the ranges of existing reality which our eyes cannot directly see, and our attitudes may become narrow and provincial. We need to develop a wider outlook, to see ourselves in our relative position in the great and mysterious universe in which we have been born and live."
After explaining the scales used in the pictures and encouraging children to draw their own images to scale, the book begins with the picture of a young girl on a blanket holding a cat. In this picture, the scale is 1:10. In other words, each centimeter represents 10 centimeters. The pictures progress from “human scale” to the farthest astronomical reaches in 26 “jumps.” Returning then to the girl on the blanket, the exploration begins in the opposite direction, down to the tiny realm of the atomic nucleus in 13 “jumps.” The book has inspired several video presentations of the same scaling (though each uses different images).
The book ends its journey at the nucleus of the atom, “that mysterious, utterly small, and incredibly powerful center of energy.” Boeke observes:
"When we thus think in cosmic terms, we realize that man, if he is to become really human, must combine in his being the greatest humility with the most careful and considerate use of the cosmic powers that are at his disposal."
By taking this imaginative journey through the universe, Boeke succeeds in imparting a sense of scale. As vast as the scales are, we can still understand something of the size of created reality.
Where Are We Now in Our Cosmic View?
In the 66 years since the publication of Boeke’s book, technological advances have extended our cosmic view. The James Webb Telescope, missions to Mars, the Moon, and even the Sun, are providing ongoing revelations about the universe. At the smaller end of the scale, investigating the inner workings of cells, the structures of viruses, measuring brain activity and visualizing neural networks, and so much more, reveal the mechanisms at work in visual perceptions, word recognition, memory, learning, creativity, and other aspects of cognition and intelligence.
The human mind, through the use of mathematics, technology, and the power of creative imagination, can glimpse the breadth and depths of the universe. What has been discovered fills us with wonder, especially when we recognize that new discoveries of the cosmos and an understanding of our place in it are not likely to end any time soon.