Late October of 2016, I attended a seminar hosted by New Scientist magazine called “Instant Expert: Relativity and Beyond”. It took place at the First Church of Boston and was the first “Instant Expert” event to be held in the U.S.
The seminar featured 6 speakers, listed in order: David Keiser of MIT, Robert Caldwell of Dartmouth College, Priya Natarajan of Yale University, Lisa Barsotti of MIT, James Guillochon of the Harvard-Smithsonian Center for Astrophysics, and Tanseem Zehra Husain, physicist and writer.
Now, in the next 800 words or so, you are going to become as much of an expert as I have, on topics including: special relativity, dark matter, black holes and string theory. I hope your thinking caps are on.
The seminar began by laying out the basics of the one theory that all following theories relied on: Einstein’s theory of special relativity. Now, unless you’re a physicist, you’re probably unfamiliar with the details of the theory. However, you are likely very familiar with the 3-dimensional world that we live in. Recently, it has been proven that Einstein’s theory is correct: 4-dimensional spacetime is not flat, but curved, relative to the mass of objects within it. Here’s an example: the moon orbits the Earth because it is following the shortest path through space and time, which is dictated by the gravity of the objects around it – like our Earth.
David Keiser – the first featured speaker at the event – illustrated the point using Einstein’s own “twin paradox”. Imagine twin human beings traveling at different speeds throughout the universe: one twin is sitting on a rocket-ship that is orbiting the Earth, while the other is standing still on planet Earth. Finally, the two twins reunite on Earth, only the Earthbound twin appears to have aged quite a significant amount compared to their sibling. This effect is due to the nature of spacetime, in which there is a difference in the elapsed time between events measured by observers.
Following David Kaiser was speaker Robert Caldwell on “the past, present and future” of our universe. He spent an information-saturated forty minutes explaining how the 14-billion year-old universe has been expanding since the big bang, and that expansion itself is accelerating; galaxies are moving away from each other, mutually. Along with many members of the audience, I learned about things like “where light has been”, which is measured by cosmic imprints left behind by the “curves” that light has traveled through in space. I learned that scientists have also found evidence of the origin of the universe by measuring amounts and temperatures of cosmic microwave background (CMB) radiation, as well as how densities of energy scattered through out the universe change over time. Caldwell concluded with his three predictions for the fate of the universe: a “big rip” in which acceleration never stops, a cold and lonely “big chill” where dark energy dominates, or a “big crunch” where the universe resorts back to a hot and dense state like in the Big Bang.
Next up was Priya Natarajan, who stretched the limitations of our knowledge with the introduction of dark matter and energy. The stuff is apparently the most dominant element in the universe, and a key factor in all structure formation. Dark matter is unseen — like air — and an exotic particle that has hung around since day one — like atoms. Although a single particle has never been found, we have learned that they are lazy and don’t have much of an influence on their own. Dark matter does not emit, absorb or reflect radiation, but it can bend light rays and influence the motion of stars and galaxies. Particles behave like they do in fluid, minus the pressure — they don’t collide, but instead graze past each other. In galaxies, dark matter is needed to explain the stability and formation of the structures within them. I was amazed at how an image of the formation of galaxies by dark matter looked just like neural networks in the brain.
The next two speakers, James Guillochon and Lisa Barsotti, discussed black holes and gravitational waves. In September of 2015, the first gravitational wave was recorded at two different laboratories in the U.S. at the same exact time. The events recorded at the Laser Interferometer Gravitational-Wave Observatory (LIGO) are hugely valuable for the scientific community. In a black hole, the gravity is so strong that nothing, not even light, can escape. When two black holes are orbiting each other, they eventually merge to create a new, bigger black hole. Because there is no light associated with gravitational waves like there is with black holes, there is no way to measure the waves themselves using light. The “ripple” caused by the merge of two black holes is a gravitational wave that can be measured by its effects on particles of matter that are “free to move”. Other gravitational waves are created from energy that is emitted by the orbit of a star (this too creates a distortion of spacetime). There is an upcoming worldwide network of these advanced detectors.
Lastly, and my personal favorite, was theoretical physicist Tanseem Zehra Husain, the first Pakistani woman to become a string theorist! She brought to our attention that Einstein’s theory does not “play nicely” with the other theories that scientists are using today. This is because different theories are using different frames of reference.
Most of what scientists measure depends on a coordinate system — even something like spacetime. Einstein’s goal was to not have to depend on a coordinate system because of its effects on what is being measured (ever heard of the observer effect?); Einstein formulated his theory in terms of invariants, or common truths that are agreed upon despite reference frames (or quantities that are agreed upon despite their measurement, like the speed of light).
These discoveries led Husain to pursue her chosen field of study, string theory, and inspired her explanations for there being at least 10 dimensions including the 3D world that we live in and 4D spacetime. Did I lose you yet? If not, I’ll have to end on string theory and hope you are interested enough to look into it for yourself. Godspeed!