When Richard Feynman encountered Dirac’s textbook on quantum electrodynamics, he did not understand it very well. Moreover, the book was replete with problems that no one was quite adept enough to solve. However, it was the last paragraph at the end of the book that encouraged him to investigate them. It read “some new ideas are here needed.”, a request Feynman felt obligated to attend to and dutifully did. His new ideas changed the way we study QED and led to the development of the Standard Model.
Unsolved problems also remind me of gravitational waves, a ripple in the fabric of space-time spread by gargantuan masses. Einstein predicted this in his General Theory of Relativity in 1916. Even though the theory was successfully corroborated by the bending of light due to the presence of the Sun while it traveled around it, evidence for the occurrence of gravitational waves never materialized.
The phenomenon was relegated to being merely a prediction due to either technological constraints or the absence of stones massive enough to cause such a sweeping ripple. It was just under 100 years before the entire world marveled at the findings of LIGO, which felt the tremors of a colossal collision between two supermassive black holes, an impact so devastating that the gravitational waves traveled astronomical miles to be detected by the observatory.
So, we can also cross that off our list of the Universe’s mysteries. However, there remain a ton of mysteries about which we are either still in the shadows or have absolutely no clue about. The theories expounded on below are not solely physics problems, but also problems concerning biology, mathematics and everything under the Universe’s umbrella.
Dark matter and Dark energy
Around the 1990s, cosmologists realized that the mass of clusters, a collection of multiple galaxies, is not large enough to hold onto those galaxies. They hypothesized that there exists, between these galaxies, other than visible matter, another type of exotic matter that accounts for the missing mass. This mysterious matter refuses to interact with light and visible matter, thereby eluding any detection. It was rightly termed, Dark Matter.
If this wasn’t enough, cosmologists also discovered that the combined mass of both visible and dark matter only accounts for roughly 30% of energy (only 4% is visible matter!) necessary to produce the density that the flat shape of our Universe requires. Where is the remaining 70%? Cosmologists hypothesized that this mysterious field, like dark matter, eludes recognition and named it Dark Energy. It is believed that dark energy is the repulsive force responsible for the rapid expansion of our Universe that Hubble observed in 1929. It was subsequently identified as the embodiment of Einstein’s cosmological constant.
To this day, no one is quite sure what dark matter or energy are comprised of. Still, while dark matter hints that there might be a new species of particles we have yet to discover, we have no assessments regarding dark energy whatsoever. It has baffled us for nearly 20 years now and looks like it will continue to do so for years to come.
The Origin of Life and Consciousness
From today’s vantage point, the emergence of life seems almost impossible. The Big Bang profusely vomited a bunch of subatomic particles that gradually coalesced to form atoms, which coalesced to form a billion stars, around one of which the remnant gas coalesced to form the Solar System, our planet and subsequently, life.
The precariousness of the tower formed by the blocks of highly unlikely possibilities stacked upon one another is perfectly illustrated by a short story that featured in Cosmicomics, a collection of eccentric science fiction tales penned by Italian writer Italo Calvino. The tale, called How Much Shall We Bet, involves two characters – the narrator, whose name is an unpronounceable “Qfwfq” and a friend “Dean (k)uk”.
They seem to live somehow separated from the Universe and make a series of bets concerning what might unfold within it. The narrator always bets for the proposition, while Dean always bets against it. The bets are quite familiar – the first one asks whether the formation of atoms would occur following the Big Bang, while the second asks whether they’ll react to form basic elements and so on until the emergence of RNA and self-replicating cells – or life.
The most unlikely, however, is depicted to be the emergence of intelligent life. Consciousness, supposedly a product of our intelligence, has long baffled philosophers, psychologists and neurologists. The most convincing explanation seems to be the hyper-connectivity and complexity of our brain cells. However, it seems impossible to discern at what point an electrochemical signal racing through a neuron transmutes to, say, the subjective feeling of the color red.
The notion of intelligent life also compels us to explore another mystery, a mystery, simultaneously, that is one of the most exulting and dreadful of the lot.
Are we alone in the Universe? If not, then where is everyone else? Of course, the emergence of intelligent life is an extremely rare phenomenon, but considering the plethora of planetary systems out there, we must expect a greeting now and then, except we never receive one.
Fermi’s one quip at lunchtime with his mates turned into one of the most important arguments speculating the whereabouts of extraterrestrial life. Fermi predicted that 10 million years would be enough for any civilization to accomplish sufficient technological grit to terraform an entire galaxy. If ten million years are a mere tick on the Universe’s clock, then these colonies must crowd galaxies densely enough to be easily detected.
Fermi’s paradox implies either the ubiquity of aliens in the Universe and our failure to detect them or that we are the lone residents of the Universe’s inconceivably capacious mansion, obscured in a remote sock drawer.
No one knows what is inside a black hole. Cosmologists predict that the stark pull of a black hole is powered by a region of zero volume and infinite density. This point of infinite gravity is called a singularity; even light cannot escape its pull.
Singularities are extremely notorious cosmological phenomena. Currently, no branch of physics can explain their behavior. Not only does Einstein’s General Relativity break down at such an infinitesimal scale, but particle physics at such a density is also beyond the understanding of the Standard Model of quantum physics. It is a point where all the laws of physics break down.
Black holes have troubled cosmologists for 50 years now. Their inexplicability signals that our understanding of physics is incomplete, thus hinting at a new theory that would unify the two extremes of physics. Einstein was found to be working on this theory until his last breath. The notebooks beside his bed and blackboards hung on the walls were filled with scribblings, but he could not accomplish any significant breakthrough whatsoever.
The multiverse theory is one of the leading arguments about the origins of the Universe. According to it, our Universe is one of a series of cluttered cosmic bubbles, each of whom is oblivious to their neighbor’s presence. The grid of Universes is known as a Multiverse, where each bubble, after springing into existence, expanded at a rate faster than the speed of light.
This whimsical theory is corroborated by the CMBR and the theory of inflation, where the former is an indisputable proof of the Big Bang and the latter is a compelling explanation for the Universe’s homogeneity. However, conclusive evidence has yet to come to light. The theory essentially explores what might have existed before the Big Bang, a question that cannot be answered right now, as it requires knowledge of singularities, which we don’t yet fully possess, as mentioned earlier.
Prime numbers have always inspired in mathematicians or number theorists, at least, a sense of mystery or rather sanctity. The Riemann Hypothesis is a mathematical problem that deals with the indiscernible distribution of prime numbers. The hypothesis, unlike the phenomena mentioned above, is in a way separated from the real world… it is highly abstract and impractical.
The problem cannot be expounded here, as it would take an entirely different article, but it can be simply summarized as “given an integer N, how many prime numbers are there that are smaller than N?” The summarization obscures the complexity it entails and makes it appear as if the problem isn’t that big of a deal. Well, if you think it’s so trivial, you might want to try your luck and proceed to win a reward of $1,000,000. The Riemann hypothesis is one of six incredibly difficult mathematical problems, together known as the Millennium Prize Problems.
Baryon Asymmetry is one of the most challenging and stimulating problems in physics. This asymmetry refers to the asymmetry in the quantity of matter and anti-matter in the Universe. Physicists often talk about how a Universe entirely made up of anti-matter would work just fine, so why is it that we only witness matter?
We know that the coming together of matter and anti-matter results in their devastating annihilation. In fact, the explosive combination has been speculated to be a promising contestant for very high-speed rocket propellant technology if, of course, we are able to extract plenty of anti-matter. Because equal proportions of the two species would annihilate themselves completely, one of them would survive only if its quantity were larger than the other.
However, why did nature favor matter and not anti-matter? And why should nature be biased in the first place? It must contrive equal amounts of both matters in the beginning. If so, what tipped the balance? Is there an unknown, underlying cause beyond our understanding… or is it just pure luck? We don’t know.
Other intriguing unsolved problems include quantum entanglement, or what Einstein called “spooky action at distance”, the scarcity of lithium in the Universe and the conjugal relationship between the Universe’s entropy and the flow of time. Some new ideas will be appreciated.