The BIG Questions
What is the universe made of? We know only 5 percent of the composition of the universe. The other 95 percent is a mystery. It is composed of dark matter (roughly at 25 percent) and dark energy (roughly at 70 percent). We don’t know what either dark matter or dark energy are, and there are hypothetical explanations that try to modify Einstein’s theory of gravity to accommodate the observations and do away with the darkness.
1) Dark Energy: Roughly 70% of the universe. It is the must mysterious, a kind of ether-like medium filling up space with the bizarre property of pushing it apart, making galaxies accelerate from one another. Nature always moves from order to disorder. Physicists discovered that universe’s inevitable slide from order to chaos is the forward movement of time. They even have a name for it: entropy. And entropy’s cosmic increase is demanded by the new piece of physics they discovered: the (hallowed) second law of thermodynamics. The forward march of chaos — that is the second law of thermodynamics and the forward movement of time.
2) Dark Matter: Roughly 25% of the universe. Dark matter doesn’t shine and is found around galaxies and clusters of galaxies, like an invisible cloak. We know it’s there because it has mass and hence gravity: it pulls on the familiar 5 percent and we can measure this effect. You have to do work to make order out of chaos. But that work heats up the matter in the universe causing them to bounce around just a bit more chaotically and creating more chaos, more entropy.
3) Bosonic Matter: The 5% of the universe made of the familiar atoms of the periodic table, their molecular aggregates or of the components of atoms, protons, electrons and neutrons. There are also neutrinos, the elusive particles that can traverse matter as if nothing was there, including the whole of Earth.
a) Why does matter exist? According to the laws of physics, matter shouldn’t exist. For every particle of matter there should be a companion of antimatter particle. For each electron there should be a positrons; for each proton there should be a antiprotons; for each neutron there should be antineutron; and so on. Matter particles are balance by an equal amount of antimatter particles. The problem is, when matter particles meet their antimatter particles they disintegrate each other (in a puff of high-energy radiation.
In the early universe matter and antimatter particles met and destroyed each other over and over again. There should be nothing left. But that’s not what happened. Particles survived the early universe without their antimatter particles. So, the mystery is what happened to all the antimatter?
Clearly something happened in the early universe to favor matter over antimatter. What? Was the universe “born” this way, with a huge asymmetry between matter and antimatter? Maybe some primordial asymmetry evolved to do the job, selecting matter? If so, when did it act in the cosmic history? And what would this asymmetry be?
(1) How did life come about? Life appeared on Earth some 3.5 billion years ago, perhaps earlier. The mystery here is how aggregates of nonliving atoms gathered into progressively more complex molecules that eventually became the first living entity, a chemical machine capable of metabolism and reproduction.
(a) What makes us human? We have three times more neurons than a gorilla, but our DNAs are almost identical. Many animals have a rudimentary language, can use tools and recognize themselves in mirrors. So, what is it that differentiates us from them? The thicker frontal cortex? The opposing thumb? The discovery of fire and the ability to cook? Our culture? When did language and tool making appear?
(i) What is consciousness? We’ve been there before in these pages, wondering about the nature of consciousness. How is it that the brain generates the self of self, the unique experience that we have of being … unique? Can the brain be reversed-engineered to be modeled by machines? Or is this a losing proposition? And why is there a consciousness at all? What is its evolutionary purpose, if any?
(ii) Why do we dream? Even though we spend about a third of our lives sleeping, we still don’t know why we dream. Do dreams have an essential function, physiological and or psychological? Or are they simply random images of a brain in partial rest? Was Freud right about his theory that dreams are some sort of expression of repressed desires? Or is that all bogus?
- Where will we put all the carbon? With the global ramping up of industrialization, we are putting more and more carbon up in the atmosphere, accelerating global warming. What can be done to change our impact on the environment? And what happens if we don’t? Models of global warming have a range of predictions, from somewhat mild to dire. Should we bet on the low odds that doing nothing will be OK? Or is it time to really take this seriously at a global scale, for the benefit of the next generation?
- How can we get more energy from the sun? We have based our explosive growth mainly on fossil fuels. Nevertheless, we have a remarkable source of energy up in the sky, waiting to be exploited more efficiently. Also, can we reproduce the solar engine here on Earth, fusing hydrogen into helium in a controllable and viable source of energy, solving our energy problem for the foreseeable future?
(b) Are we alone in the universe? This question is really two questions: Does life exist out there and, if so, what fraction of this alien life is complex and intelligent. If intelligent life is not so rare, why haven’t we heard from “them” yet? I recommend the book by Lee Billings, Five Billion Years of Solitude, for an up-to-date synopsis of the search for life elsewhere and the key people behind it.
Are there other universes? Or is our universe the only one? Believe it or not, modern theories of cosmology and particle physics predict the existence of other universes, potentially with different properties to our own. Are they there? How would we know, if we could? If we can’t confirm this hypothesis, is it still part of science?