I'll probably never forget one particular experience I had as a kid on my first camping trip.
The night sky was so full of stars, it was incredible to just stand there and look straight up.
That's all I could say.
My dad pointed out the Big Dipper, showed me how to find the North Star, and there were some other constellations he mentioned as well,
but as a youngster, I was overwhelmed and just kept thinking, "Look at all of those stars!"
Seeing that light band in the sky, which I was told was the "Milky Way" Galaxy, left me stunned. I could not get enough information
from the men who were the fathers of the Boy Scouts with whom I was camping. I asked all of the normal childlike questions about
the Milky Way's size and the speed of its apparent rotation, but exact answers were just not a part of their everyday experience.
As I got older, I learned that what we see in the northern hemisphere is the center of the galaxy, should we happen to gaze in the direction
of the constellation Sagittarius. If you track it away from the galactic center, you will be staring at two components of the Milky Way:
The Sagittarius "Arm" and the Orion "Spur." These are both portions of the spiral arms of the galaxy, and once you try to comprehend the
magnitude of what you are observing, you cannot help but feel a tremendous sense of awe and wonder.
According to a July 2015 estimate by NASA,
our galaxy has between 100 billion and 400 billion stars within it. This is a mind-boggling number.
The distances between stars is measured in "light years," which is how far a beam of light traveling 186,000 miles per second will travel in one year (31,557,600 seconds).
Do the math and you get one light year is 5,869,713,600,000 miles (roughly 5.8 trillion). Our best estimate for the diameter of the Milky Way is between 150,000 and
200,000 light years. This means to get from one side of the galaxy to the other, you would have to travel as many as 1,173,942,720,000,000,000 miles (1.1 quintillion).
Just looking at the chart shown above jargogles the mind. Such extraordinary scales are far beyond our perspicacity.
Going from the galaxy-scale to the scale of the universe is even more astonishing. The best estimate for the age of the Universe is
13.8 billion years, so one might naturally conclude that it can be no "larger" than that number of light years as a "radius."
It turns out that the Universe is much larger than 27.6 billion light years wide, for two reasons:
1. The Universe itself has been expanding over its entire existence, so the light travelling within it has been traversing an expanding space.
2. The light-emitting objects that are most distant, estimated at 46 billion light years, are part of the Observable Universe, which is, in fact,
smaller than the entire Universe!
Originally, I used to think that the red-shifted light most distant to us, the so-called Cosmic Microwave Background, was the first light
emitted from the Big Bang, and, therefore, was the furthest something could be from us here on earth. But this is not the case at all.
If we could INSTANTLY transport to any such spot where such radiation existed, we would be at the center of yet another OBSERVABLE UNIVERSE,
and we would see there is no microwave radiation there at all! Yet there would be, on some far-off horizon, a perceived background of the same
type of radiation, equally distant from our previous instantaneous jump. There is an entire Universe's worth of objects we could not see before,
since they were beyond the range of lit objects whose light could reach us in the time since the Big Bang occurred.
In this respect, the Universe itself could indeed be infinite.