Only five centuries ago, not even the blink of an eye in time when compared to the age of the universe, humanity’s vision extended but a little beyond Saturn. Our ancestors envisioned a universe both limited and orderly. The telescope changed all that, and our universe expanded exponentially as we observed literally thousands of objects beyond the Earth. Because of developments in astronomy and spaceflight in the twentieth century, humanity’s vision of the universe has changed even more.
Edwin Hubble proposed the idea of the Big Bang to explain the origins of the universe and since that time numerous spacecraft and scientists have helped to expand on our knowledge of the universe. The most significant astronomical instrument since Galileo’s first telescope, the Hubble Space Telescope, has revolutionized our understanding. In just the last decade, our cosmology has changed as we found irrefutable evidence of black holes, the Big Bang, dark matter, dark energy, the corpuscular universe, multiple dimensions, and extra solar planets. So just what have we learned since the beginning of the space age, what big questions exist at present, and how are space scientists seeking to answer them?
Using the powerful telescope at the Mount Wilson Observatory near Pasadena, California, in the early 1920s astronomer Edwin Hubble first confirmed the existence of galaxies outside the Milky Way. He then observed that these galaxies were racing away from ours, an indication that the universe was expanding. This became the first critical evidence pointing to an explanation of the origin of the universe in a Big Bang from a singularity of infinite nothingness that contained all of the matter of our universe to what we observe today. It proved an elegant, convincing, and resilient theory of the universe’s formation. Despite periodic detractors, the Big Bang theory is virtually universally accepted in the scientific community even as it undergoes moderate modification through further observation and experimentation.
For decades scientists debated the possibility that the mass of the universe—matter, anti-matter, dark matter, and perhaps others types as yet undiscovered—would be sufficient that its gravitational forces over eons would halt the expansion and begin a contraction of the universe back to its singularity. And then the process would start all over again. Whether we live in an open (expanding indefinitely) or closed (eventually contracting) universe depends very much on the mass of the universe and the gravity generated by it.
Thus far scientists have found that only about 4 percent of the universe exists in the form of stars, gas planets, white dwarfs, black holes, and other observable matter. The rest is made up of dark energy or dark matter, and the core question is whether this 96 percent of the universe’s “stuff” is sufficiently strong in gravity to pull everything back from endless expansion. Many scientists now think that the universe will continue to expand indefinitely, with energy eventually dissipating some trillion years in the future and all stars eventually becoming so many stellar cinders. This is a pretty bleak future, but obviously a far distant one.
Of course, the universe may not end in this manner. Scientists may be wrong about these projections. Something yet undiscovered mass or process may affect cosmic evolution in a far different manner. The most intriguing possibility at present is a theory of multiverses occupying the same time-space. According to some cosmologists, the space in our universe is part of a three-dimensional place called a brane, short for membrane, which is also part of a much larger eleven dimensional space-time connected by gravitational forces.
There may even be an infinite number of three-dimensional universes occupying portions of this larger eleven dimensional space-time. In modern M-theory, as the multiverse ideas are called, other universes might be very different from ours, but separate from own space-time by a very short physical space. Like frequencies on a single radio, there might be a vast number of successful and failed universes co-existing in an eternal state.
Perhaps black holes offer linkages between these universes, perhaps not. Perhaps there may be ways to travel between them. Perhaps also, black holes are the point from which new universes begin, extending as corpuscles of the universe from which the black hole had emerged. If so, perhaps the eternity of all we know in this universe may be assured elsewhere. This theory is unproven, and perhaps unprovable, but it represents an enormously exciting potential for consideration.
I showed my cousin through the “Explore the Universe” exhibition at the National Air and Space Museum last week and was waxing eloquent about some of these concepts. She was fascinated, but had difficultly fathoming the sheer magnitude of the possibilities. She’s not alone; so do I. It was a bit of the blind leading the blind. But it is one of the most exciting concepts I’ve ever been exposed to. I always wonder, what might we learn in the twenty-first century that will lead to a scientific revolution every bit as great as the Copernican Revolution of the seventeenth century and the Einstein Revolution of the twentieth century?