April 26, 2012
Any diehard stargazer will tell you that springtime is galaxy time. As Earth orbits the sun, our position on Earth is presented with different parts of the sky at any given time of the night. During the early evenings of summer, we stare straight into the disc of our Milky Way, a glorious view of our own galaxy.
Unfortunately, the stars and dust of our galaxy block the view of more distant parts of the universe. During the early evenings of spring we look at a right angle to the disc through the thinnest part of the Milky Way. The sky is sparse with stars, but more distant galaxies appear. Stargazers with telescopes can observe hundreds of galaxies in a night — from the glorious face-on spiral of the Whirlpool Galaxy near the handle of the Big Dipper to the toothpick-thin edge-on NGC4565 to the Virgo Cluster of galaxies where scores of galaxies of all shapes and sizes reside.
When one considers that each galaxy is itself a Milky Way of hundreds of billions of stars, our tiny planet orbiting its below-average star pales to insignificance.
Of course, we haven’t always known our place in the cosmos. For most of the history of civilization, humans have believed that the Earth was at the center of the Universe. That is what our common sense tells us as we look at the night sky.
As we stare at the bowl of the night, we seem to see ourselves at the center with the sun, moon, planets, and stars circling around us endlessly.
People like Galileo got into a lot of trouble for saying that the Earth is just one of the planets circling around the Sun, and that the Sun is just one of many stars in our galaxy, and, more recently, that our galaxy is one of many in a Universe of incomprehensible size.
However, in an important sense, the ancients were right. The Earth IS the center of the Universe.
Much to their amazement, modern astronomers discovered that virtually all the galaxies they look at are moving away from our point of reference, the Earth, at incredible velocities. It looks as if the Universe is expanding with the Earth at the center of the expansion.
To understand that rather strange paradox, we must consider how modern astronomers believe the Universe came into being.
The Universe began as a single point that expanded into the present cosmos in a cataclysmic explosion called the Big Bang.
Our present Universe can thus be conceived of as the surface of a huge balloon, the still expanding remnant of that immense explosion that occurred billions of years ago.
Neither the outside of the balloon or its inside exists, only the balloon itself. All that exists, including not just matter but space, is in the surface of that balloon. All the dimensions of space — height, width, and depth — are thus curved along the surface of the balloon.
There is no center to a balloon. In a sense, any single point on the balloon could be called the center. And from the point of view of any given point, all the other points are expanding away from it as the balloon gets bigger.
Thus, there is no center to the Universe, just as there is no center to the balloon’s surface. But in a very real sense, EVERYTHING is at the center, with everything else expanding away from it.
The Earth is no longer an insignificant speck in a nowhere part of the Universe. It is just as significant as everything else, at the center of a cosmos with an infinite number of centers.
And if you understand that fundamental concept, please explain it to me. My head gets it well enough, but I have yet to understand it in my heart, where it counts.
Saturn is still high in the south in the constellation Virgo.
This week’s big news is the spectacular conjunction of four planets low in the east during morning twilight. They will move around a bit over the course of the week, so the best way to identify them is in order of brightness. Venus is purest white and brightest of all. Nearly as bright is Jupiter. Next comes reddish and much dimmer Mars. Mercury is dimmest of all and may require binoculars to see.
Start about 45 minutes before sunrise. Try to find an eastern horizon free of trees and buildings, look low, and wait. The objects will get higher as time passes, but so will the amount of twilight.
The morning of May 11 (My birthday!) will be particularly spectacular because the two brightest of the four, Venus and Jupiter, will be so close that they’ll look like two gleaming cat’s eyes staring at you from the darkness.
Tom Burns is the director of Ohio Wesleyan University’s Perkins Observatory. firstname.lastname@example.org.