After watching Lawrence Krauss on YouTube, doing a presentation on how the Universe could have arisen from nothing, I felt compelled to buy the book, even knowing how I struggle with physics. The question of the Universe’s origin is just too fascinating to pass up an opportunity to possibly answer it. I did struggle through some of the sections as I expected, but conceptually I was able to grasp much of it and come away from reading it with an even greater sense of awe if such a thing is possible.
A century ago–which is a blink of an eye in geological terms, let alone cosmological ones–we thought the Milky Way was the entire Universe. We’ve become so accustomed to pictures from the Hubble Telescope, showing us 100 billion galaxies, each with a billion or more stars, that it’s almost hard to imagine a time when we didn’t know this.
The universe is flat, expanding ever outward from the Big Bang. The most important set of observations in all of cosmology are the measurements of the cosmic microwave background radiation, which is the afterglow of the Big Bang. It is direct evidence of the Big Bang, allowing us to look back directly and detect the nature of the very young universe from which everything we see today eventually emerged. While I understand the scientific method, reading the history of our expanding knowledge about the observable universe shows how the most important aspect of science is not what we learn, but how we learn. Following the evidence to show us the true picture of our natural world, which may or may not be the way we think it is or should be, is an important lesson for all of us in how to think critically and logically.
The key focus of the book is of course on the origins of the universe and why there is something rather than nothing. I’m not going to pretend to understand quantum mechanics but I think I can grasp the concept that empty space isn’t exactly “empty.” At the quantum level, there are particles popping into and out of existence all the time. Much of our universe is composed of empty space, but there’s a difference between empty space and “nothing.” Empty space with the laws of physics acting upon it, expanding exponentially–and we’ve observed the expanding universe as galaxies filled with stars all scream away from each other at fantastic speeds–means that there is energy in this space, in this nothingness.
As the universe expanded, the empty space inflating from the initial expansion was filled with energy and this energy turned into real particles and radiation. Residual, small-density fluctuations in empty space would eventually become all the matter and structure in the universe. The energy of empty space in the presence of gravity is the reason there is something rather than nothing. Nothing is unstable. Empty space is a “boiling brew of virtual particles that pop in and out of existence in a time so short we cannot see them directly.” An asymmetry of matter and anti-matter, even if it were only 1 part in a billion, would leave enough matter left over to account for everything we see in the universe today. In fact, 1 part in a billion is exactly what is called for because today there are roughly 1 billion photons in the cosmic microwave background for every proton in the universe. The photons are the remnants of the early matter-antimatter annihilations near the beginning of time.
What is perhaps most astonishing is what the future holds. As the universe continues to expand, galaxies will move outside of what is observable. Future astronomers in some other galaxy a trillion years from now will never know the Big Bang, will never see the other galaxies. They will in fact make the same mistake we made a hundred years ago: that their galaxy is the entire universe surrounded by nothing. The future will be dominated by a universe with nothing in it as protons and neutrons will decay, matter will disappear and the universe will approach a state of simple symmetry.
I know I will read this book again, likely more than once. I will watch the YouTube video presentation again, likely more than once. The fact that it’s been viewed over a million times shows that the origins of the cosmos is still just as fascinating and perplexing a question as it has always been to humanity. This book brings together the major pieces of evidence we’ve collected along with the newest information and paints the picture of what this evidence suggests. It may not be what we’d like it to be, but I don’t think the universe cares much for what we think.
The Known Universe from AMNH on Vimeo.