Inexplicable Universe unravels a tapestry of unsolved mysteries that continue to captivate human curiosity. From the enigma of dark matter to the perplexities of black holes, these unresolved cosmic puzzles challenge our understanding of the cosmos.

I had the pleasure of studying under the guidance of Neil deGrasse Tyson, Ph.D., in a course titled “The Inexplicable Universe: Unsolved Mysteries.” This course discussed various phenomena and how our understanding of the universe has evolved over the centuries.

Before Galileo, about 400 years ago, most scientific theories were formulated based on mere thought and speculation. Philosophers like Aristotle devised theories just by pondering upon things. After Galileo, science became experimental; we performed experiments to either accept or deny an argument.

For instance, before Galileo’s era, epilepsy was deemed a sacred disease as no experimentation could be done. Mysterious occurrences like overnight mushroom growth were attributed to fairy circles because there was no scientific explanation.

Tyson discusses a variety of topics, starting with the idea of ether. Before Einstein, it was believed that light needed a medium to travel, just as sound requires air. This supposed medium was called ‘ether.’ In the 19th century, physicists including James Clerk Maxwell proposed that light was a wave that propagated through this “luminiferous aether“. Newton and many others believed in this concept. However, Einstein, along with other scientists, disproved the existence of ether, establishing that the speed of light is constant. He proposed this in his Special Theory of Relativity in 1905, debunking the notion of ether from classical physics.

In 1781, Urranus was discovered. When Newton’s laws were applied to Uranus, they could not explain the planet’s movements. This led to the realization that there must be another body exerting gravitational influence. This hypothesis pointed towards the existence of another planet, which when investigated, led to the discovery of Neptune. This was the first time that calculations predicted a discovery, hence this is significant.

Einstein’s Theory of Relativity, proposed in 1916, identified space and time as a fabric that curves in the presence of a heavy body. At high levels of gravity, Newton’s laws failed, necessitating Einstein’s theory. His conceptualization of space and time as a fabric successfully explained the movement of massive celestial bodies.

From the second century geocentric model of Ptolemy, to the 16th-century heliocentric model by Copernicus, to Newton’s Law of Gravity, and ultimately to Einstein’s theories, humanity has made significant progress.

Einstein’s Theory of Relativity, which is essentially a theory of gravity, describes gravity not as a force as traditional Newtonian physics does, but as a curvature of space and time caused by mass and energy. Since its proposition, it has passed a multitude of experimental tests.

Tyson also delves into the subject of atomic structure. In 1897, electrons were discovered, followed by protons in 1911. This led to the realization that an atom is mostly free space. In 1932, neutrons, which carry no charge, were discovered. Both protons and neutrons are composed of quarks, which come in six types: up, down, top, bottom, charm, and strange, characterized by varying levels of energy. Quarks always exist in pairs, and they are impossible to separate; if you try to move them apart, the energy exerted is converted into another quark.

In 1930, the existence of neutrinos was predicted, and they were discovered in 1956. An astounding 65 billion neutrinos pass through our skin per square centimeter, primarily emanating from the Sun. Neutrinos also carry no charge.

The time dilation principle, as explained by Einstein’s theory, states that as we move closer to the speed of light, time slows down. If we reach the speed of light, time stops. For a photon released by a star a billion light-years away, the journey to us would seem instant, because from the photon’s perspective, time does not exist because it is traveling at speed of time.

Upon reaching Earth, if a photon hits an object like a telescope, its journey ends, and the energy is transferred. If it strikes a solar panel, its energy is converted into electricity. If it hits a plant, it triggers photosynthesis. If it hits our eyes, it generates an electrical signal that our brain interprets as light. So, its journey ceases when it imparts its energy to something else.

Then we move on to quantum physics. Quantum physics, also known as quantum mechanics, is a branch of physics that deals with phenomena on a very small scale, such as molecules, atoms, and subatomic particles like electrons and photons, or particles of light. This fundamental theory provides a description of the physical properties of nature at the atomic and subatomic scale.

The development of quantum theory or quantum mechanics was a cumulative effort by numerous scientists over several decades. The “father” of quantum theory is often considered to be Max Planck. In 1900, he proposed that energy is made up of individual units, or quanta. Albert Einstein, in 1905, suggested that light also exists in discrete packets, which he named photons. He won a Nobel Prize for explaining the photoelectric effect, a phenomenon that states electrons are emitted from a material when light of certain frequency shines on it.

In 1913, Niels Bohr introduced his model of the atom, positing that electrons exist in quantized energy levels. Other major contributors to quantum mechanics include Werner Heisenberg and his famous uncertainty principle. This principle states that it is impossible to simultaneously measure with perfect accuracy both the position and the momentum of a particle. In other words, the more precisely the position of a particle is determined, the less precisely its momentum can be known, and vice versa.

We also look at the contributions made by Edwin Hubble. He was the first to propose that the universe was expanding, and that all galaxies are moving away from us at speeds proportional to their distance. Hubble’s law isn’t to say that the galaxies themselves are moving; instead, it posits that the fabric of space itself is expanding, carrying the galaxies along with it. This was a profound idea and a stepping stone for the Big Bang theory, as well as subsequent developments in astronomy and astrophysics.

In the context of the universe’s expansion, it’s more accurate to say that the space between galaxies is expanding, rather than the galaxies themselves are moving through space. However, galaxies can also have their own motion, independent of the cosmic expansion. This is referred to as peculiar velocity. For instance, the Andromeda Galaxy and the Milky Way are moving towards each other due to their mutual gravitational attraction, and they will eventually collide in about 4 billion years, despite the overall cosmic expansion.

Tyson then moves on to quantum tunneling, a phenomenon in quantum mechanics where particles can pass through potential barriers that classical physics predicts they should not be able to. This concept is integral to several physical phenomena and technologies, such as the operation of quantum computers and the scanning tunneling microscope. It is also involved in certain nuclear reactions in stars.

Quantum tunneling also forms the basis of quantum bits or qubits, the fundamental building blocks of quantum computers. Unlike classical bits, which can be either 0 or 1, qubits can be in a superposition of states, and quantum tunneling allows them to switch between these states.

Then we move on to Einstein’s most famous equation, E=mc^2, where energy and mass are interchangeable. For instance, when we pull the string of a spring, we’re inserting energy into it, and if we weigh it afterward, it will weigh more due to the added energy. More energy means more mass, so substances with stored energy, like gunpowder or gasoline, would weigh more because of this additional energy.

Tyson continues to explain that whenever Newton encountered anomalies or inexplicable occurrences in his research, he attributed them to divine intervention. He called this the invisible hand of God, suggesting God’s role in events unexplainable by Newtonian physics. Meanwhile, when Christiaan Huygens penned his theories, he didn’t invoke God but relied on creative rationality. For example, he hypothesized about Jupiter, questioning if it had an atmosphere, and if so, it must have weather, which would mean rain and potentially oceans, possibly indicating the existence of life. Huygens’s logical thought progression led him to ponder whether life may have existed on Jupiter at some point.

Moving on to the origin of life on our planet, Tyson explains that life emerged relatively soon after Earth’s formation. Initially, frequent meteoroid impacts raised temperatures, making the environment inhospitable for life. But once the impacts ceased and the Earth cooled down, life emerged within 200 million years, evolving from inorganic to organic forms. This process took place over approximately 4 billion years ago.

Tyson posits that all life on Earth evolved from a singular “tree of life,” with DNA being the universal basis. However, he doesn’t discount the possibility of life forms on other planets that may not be DNA-based. The phenomenon of panspermia suggests life on Earth could have originated from Mars, carried here by a meteorite harboring Martian microbes. If true, we are all descendants of Martians.

Another intriguing aspect Tyson points out is the chirality, or “handedness,” of molecules. On Earth, molecules predominantly exhibit left-handedness, whereas in the universe at large, there’s an equal 50-50 split between left and right-handed molecules. This minor shift in atom placement can drastically change the structure of a molecule, just like the difference between spearmint and caraway seeds – they share the same chemical composition but differ in orientation. Tyson leaves us pondering whether this left-handed dominance on Earth is a coincidence or perhaps a survival mechanism.

The next topic Tyson discusses is intelligent life itself. Despite sharing 99% of our DNA with chimpanzees, the 1% difference yields a significant gap in communication and cognitive capabilities. Suppose there exists another life form just 1% more advanced than us. In that case, the communication gap could be similarly vast – they would be as superior to us as we are to chimpanzees.

These ideas prompt contemplation on the various dimensions of possibilities. There could be anything out there, and anything could have happened. Tyson then transitions to discussing the periodic table. Elements numbered 113 to 118 are created in laboratories, not naturally occurring. The table’s structure also reveals interesting patterns; as we move from left to right, each column adds an electron, leading to different bonding capacities.

In relation to life forms, Tyson considers that while Earth harbors carbon-based life, silicon-based life could exist elsewhere due to carbon and silicon’s similar bonding properties. He discusses atomic stability, pointing out that the stability of both the outer shell, where electrons revolve, and the nucleus, containing protons and neutrons, is critical. Elements on the periodic table with an atomic number greater than 82 (lead) are unstable and can exist only briefly.

Tyson then explains the concept of smashing atoms in an accelerator. The resulting energy release takes on three levels: low, medium, and high. He also discusses the universe’s balance of matter and antimatter.

The topic shifts to Einstein’s unfinished United Field theory, envisioned as a single equation to define all laws of the universe. This concept is reminiscent of when electricity and magnetism were unified into electromagnetism, and later, the weak force and electromagnetism combined to form the electroweak force. Scientists are still seeking this unifying theory.

Tyson then explores black holes, where the curvature of space-time is so steep and gravity so strong that nothing can escape. This concept is encapsulated in a well-known scientific aphorism: “matter tells space how to curve, and space tells matter how to move.“

Then Tyson delves into the hypothetical scenario of a human falling into a black hole. Such an event would cause intense physical distortion, referred to as ‘spaghettification‘, and a complete stop in time. Some speculate this could potentially open up a gateway to a different universe. A person falling into a black hole would perceive their own time as passing normally due to gravitational time dilation, while observers from outside would see their time slow down and eventually freeze. The universe one falls into when entering a black hole is theorized to be entirely different from the one left behind – an intriguing concept.

We next delve into the Pioneer anomaly. In the early seventies, the Pioneer 10 and Pioneer 11 spacecrafts were launched and have since traveled through our solar system and beyond. An analysis of their navigational data revealed an unexplained constant acceleration directed towards the sun. For many years, this phenomenon remained a mystery. However, in 2010, it was determined that the deviation was largely due to the heat emitted by the spacecraft itself. This is a testament to how some anomalies can take decades to be fully understood without having to modify our foundational theories.

Our attention then shifts to dark matter. Approximately 85% of the gravitational pull in the universe is attributed to dark matter. The issue surfaced when galaxies in clusters moved faster than the known mass within them would seemingly permit. This suggested the presence of additional mass or gravitational force within these galaxies, which was then termed dark matter. Unlike ordinary matter, dark matter neither emits, absorbs, nor reflects light. It doesn’t interact with photons or electromagnetic radiation, rendering it invisible. However, we infer its existence based on its gravitational effects on visible matter. One leading theory posits that dark matter is comprised of weakly interacting massive particles (WIMPs). These particles would primarily interact via gravity and the weak nuclear force, which makes them exceptionally elusive.

Tyson introduces a captivating idea: dark matter might be an interaction or “spillage” from a parallel universe. While this is a speculative hypothesis, it introduces the tantalizing possibility of multiple, interacting universes. The gravitational pull we term “dark matter” might indeed be the influence of matter from another universe seeping into our own.

Subsequently, we explore dark energy, believed to be the force driving the accelerated expansion of the universe. Intuitively, the collective gravity of all matter should cause the universe to contract. However, it’s expanding, suggesting another force at play. Einstein once introduced a constant in his equations to account for this but later retracted it after Edwin Hubble’s discovery of the expanding universe. Today, with our understanding of dark energy, we realize Einstein might have been on the right track. The universe’s composition is roughly 70% dark energy and 26% dark matter. Surprisingly, this means about 96% of the universe is still a mystery to us, with the remaining 4% being ordinary matter.

We then touch upon the concept of zero total energy. When accounting for all visible matter, dark matter, and dark energy, our universe is “flat” — implying it has zero net total energy. This could mean our universe arose from nothing.

The narrative then transitions to the impending collision between our Milky Way galaxy and Andromeda, our closest galaxy. In about four billion years, they will merge, a spectacle illustrated in various images.

Milky Way’s Head On Collision
Tyson then delves into the multiverse concept. In the universe, plurality is the norm: numerous stars, countless galaxies, and myriad galaxy clusters. This hints that our universe might just be one among many — a fascinating proposition suggesting the existence of multiple universes.

We then explore the iconic equation E=mc^2. When energy is introduced, it produces particles, always in pairs, which move in opposite directions. This means energy can create an electron and its antimatter counterpart, a positron. If these pairs are brought together, they revert back to energy, demonstrating the interchangeability between mass and energy. Initially, it seemed that there was a symmetrical creation of matter and antimatter. However, this symmetry was broken. If perfect symmetry had been preserved, the matter and antimatter would have annihilated each other, and we would not exist. At some point, nature deviated from its own patterns. In rare instances, perhaps one in 100 million, a matter particle was created without its corresponding antimatter partner. The visible universe exists due to this broken symmetry and the resultant “orphan” particles that couldn’t be annihilated.

Next, we delve into the concept of wormholes. If we want to reach a distant galaxy millions of light-years away, using conventional travel (even at the speed of light) would still take millions of years. However, by bending or “warping” the fabric of space, distances can be drastically reduced, allowing near-instantaneous travel between vast cosmic distances. This idea, popularized in series like Star Trek, suggests that wormholes might be our only viable option for intergalactic travel. For perspective, using current spacecraft, reaching our nearest star would take between 50,000 and 70,000 years!

Our discussion then shifts to the expanding universe. In the distant future, the universe will have expanded so much that galaxies and stars will be too far apart to be observed. This would mark the end of cosmology, as there would be nothing left to study. Over time, galaxies would lose their stars, having consumed all their fuel. Eventually, black holes will be the remaining dominant entities. Fast forwarding to an almost incomprehensible time scale — 10^100 years, or a “googol” year — black holes will evaporate, leaving the universe in darkness. As the universe continues to expand, it will cool until it reaches near absolute zero, turning it into a cosmic “icebox” rather than a blazing inferno.

In concluding the course, we’re reminded of an awe-inspiring fact: the observable universe we see comprises only 4% of its total content. The other 96%, made up of dark energy and dark matter, remains a mystery. Moreover, there could be other dimensions and parallel universes beyond our comprehension. Much like how future generations might be oblivious to the stars and galaxies that once existed, we might currently be unaware of vast cosmic truths.

In this course, Tyson masterfully presents these complex ideas. His style, complemented by his gestures and effectiveness, makes the content accessible and intriguing. I highly recommend it to all curious minds. Having engaged with this content, I’ve sought out and enjoyed many of Tyson’s other works, which provide similarly enlightening perspectives on the universe.