A duel of theories: quantum mechanics, general relativity — or both?

Talks by researchers during Science Rendezvous festival illuminate theories of physics

A duel of theories: quantum mechanics, general relativity — or both?

From the Department of Physics, Professor A. W. Peet and post-doctoral fellow Aharon Brodutch delivered two related yet different talks about crucial theories of physics to a wide range of attendees of the May 11 Science Rendezvous street festival on the St. George campus.

Gravity causes black holes to exist

Even if you dozed off in high school physics lectures, there’s almost no way you haven’t heard of black holes. Just over a month ago, NASA published the first ever image of a black hole, which left the world in utter awe.

But what causes black holes to exist? To answer, Peet began by explaining the theory of gravity.

We are all familiar with the force of gravity: you drop a tennis ball, and it falls downwards. Gravity is the invisible force that is responsible for the attraction of all objects to each other. Furthermore, the strength of the force is directly related to the object’s mass. The larger the mass, the larger the force of attraction between the objects.

However, gravity not only attracts mass, but it also pulls on light — despite the fact that light is composed of massless particles.

How can gravity ever be strong enough to trap massless light?

Consider black holes: Einstein’s theory of general relativity — which provides an alternative explanation of gravity as a property of space and time — anticipated that when a massive star dies, the remnant it casts off has three times the mass of the Sun, and a black hole is produced.

Peet gave an alternative definition of the phenomenon: “an object is called a black hole if it is dense enough to be contained within its own event horizon.”

The event horizon can be thought of as the point-of-no-return: if you fall into it, escape is impossible, regardless of your rocket power. This also applies to light. Inside this radius, the gravity is so strong that not even light can escape.

Yet despite their attractive force, black holes still emit radiation

Peet mentioned that “at [a black hole’s] heart, there exists a singularity, where its curvature becomes infinite.” With an infinite radius, Einstein’s theory of general relativity fails to demonstrate any results at the singularity of a black hole, since all the equations render infinity as the solution.

Meanwhile, with the employment of quantum theory into Einstein’s theory of general relativity, physicist Stephen Hawking was able to prove that black holes actually do emit radiation — therefore they do not appear completely black after all.

Two theories that cannot exist under the same roof

Einstein’s theory of general relativity describes the physics behind very heavy objects — such as planets, stars, and moons. Quantum mechanics, on the other hand, is the physics relating to extremely small particles.

Now, considering the two, you would think that their incompatibility is not truly problematic, since nothing can be both very heavy and very small. However, when has science ever been that simple?

“There are two things that we care about: black holes and the Big Bang!” added Peet. They continued by saying that in order to be able to effectively and accurately analyze these two mysteries, we would need a theory that could be applied to both massive and small objects.

String theory mends the two clashing theories

String theory predicts that inside the elementary particles — irreducible particles previously thought to be point-like — are actually one-dimensional vibrating strands of energy known as strings. The fact that strings are versatile demonstrates the ease with which they can interact, and thus solves the problems arising from the theory of general relativity.

Peet also mentioned that string theory can predict possible extra dimensions of space, explaining that “the strings could wrap around those hidden dimensions.”

Multiple worlds at once?

Now that we have reached a better understanding of black holes, let us consider other realms and dimensions through our understanding of quantum theory. In 1935, physicist Erwin Schrödinger came up with a world-changing theoretical experiment known as the Schrödinger’s cat paradox.

“He placed a cat in a steel chamber with a Geiger counter, a vial of poison, a hammer, and some radioactive substance,” explained Brodutch.

This process is not one that naturally comes to mind, yet it does make physical sense. With the decay of the radioactive substance, the Geiger counter would prompt the hammer to fall on the vial, releasing the poison and consequently killing the cat. Seems pretty straight forward, right? Then, what is the paradox about?

What Schrödinger wanted to demonstrate, explained Brodutch, was that we would not know whether the cat was dead or alive until we opened the chamber. Thus, in order to be theoretically accurate, we would have to assume that while the steel box is still closed, the cat is both dead and alive simultaneously in two different worlds.

With the help of the Schrödinger’s cat paradox, we are able to somewhat understand the possibility of the existence of more than a single world at once.

The worlds can interfere

This paradox was employed in order to account for the wave function of a particle: the particle could be in any allowed position at a certain instant, yet you could not know exactly where unless you directly saw it.

Brodutch further said that “each world will be one term in the equation, and as the branched worlds keep going, the equation becomes longer and longer.”

Thus, maintaining control over these quantum systems becomes the main concern. Applying quantum theory to modern-day technological advances, Brodutch explained that it enables quantum computers “to factorize really, really fast,” and as a result, “keep [security-sensitive] transactions very secure.”

The mathematics behind soccer

Abdullah Zafar studies team movement in soccer using vector fields

The mathematics behind soccer

Third-year U of T math and physics student Abdullah Zafar is collaborating with Sport Performance Analytics Inc. to study the mathematics behind team movements in soccer.

Zafar, a soccer player himself, presented his research at the ASSU Undergraduate Research Conference in January, in a presentation entitled “Weaving the Fabric of Football: How Vector Fields and Fractal Dynamics Structure Patterns in Team Movement and Performance.”

This project was brought to life after Zafar and Farzad Yousefian, founder and president of Sport Performance Analytics Inc, noticed a gap in how sports models were approached and analyzed. The pair sought to understand the underlying mechanics behind group movement and team dynamics on the field.

To achieve this, the research team collected data from the Canadian women’s soccer team at the Summer Universiade. Zafar analyzed the overall patterns of individual player movements and explored their relation to player performance measures.

While each player’s movement is individually determined, their overall movement on the field is influenced by other players’ positions. Zafar quantified movements of the latter type and analyzed them as a single unit.

Using vector fields, Zafar measured team movement and found a correlation to physical metrics like player heart rate and distance played. He characterized these patterns of team movement as Brownian motion.

Zafar’s findings could be used to assess efficiency and performance on the field, and develop strategies to impact the tactical side of team sports with practical training protocols.

In an interview with The Varsity, Zafar explained that quantifying group movements by collecting variables such as speed, directionality, and steps per minute was the easier part of the process. However, painting a group picture in terms of a complete analysis was a challenge.

The project has come a long way since last summer, and is being presented at various conferences.

Moving forward, data collection will still be a major barrier, considering that performance data is like personal property to teams, and Zafar notes that getting access to it can be difficult. Were the research team to have access to league information, the sports teams need not worry about competition between them. In the long run, access to more information would allow the data to be more generalizable.

Zafar said that this initial report serves only as a pilot study a proof of principle that demonstrates that this field of research can be pursued.

Currently, the team is breaking the project into more concise research questions that can address specific aspects of sports performance, including tactical and physiological perspectives.

According to Zafar, another challenge is obtaining funding. Compared to health and wellness, sports performance analysis receives less funding. Shifting the perspective of the research to one of clinical importance could be the key to accessing funding in the future.

Physics and philosophy at play

U of T professors answer questions about dark matter, instrumentation, and more

Physics and philosophy at play

At a panel earlier this month, undergraduates in the joint specialist Physics and Philosophy program at U of T posed philosophical questions arising from findings in physics to Professors David Curtin, Michael Luke, and Michael Miller at McLennan Physical Laboratories.

Dark matter and dark energy

Valentina Pentcheva, a Physics and Philosophy specialist, explained that dark energy and dark matter are unobservable components of reality, which compose 72 per cent and 23 per cent of the universe respectively. That leaves only five per cent of the universe observable.

Theories of dark matter and dark energy arose from researchers “trying to make sense of observations that contradict our physical theories up until now,” continued Pentcheva. Dark energy explains the “rapid expansion of the universe” while dark matter explains the movement of stars at the edge of galaxies.

“How can we consider our science adequate, if we missed over 90 per cent of our universe?” asked Pentcheva.

Furthermore, should we conceptualize dark matter and dark energy as “real things,” or “should we instead be committed to them only as instrumental tools?” Finally, she asked if “is there any reason why we should be more confident in the truth of our current theories” rather than others that have been falsified.

Curtin, Assistant Professor of Physics, explained that dark matter and dark energy are indeed every real things, even though we cannot directly image them due to their inability to interact with light.

“Dark matter and dark energy are, in fact, extremely observable and extremely precise physical predictions and have very concrete physical consequences,” said Curtin. For example, when astrophysicists view the collision of two galaxy clusters, they can “map out the dark matter” involved in the collision using an observational technique called gravitational lensing.”

“Just because we can’t see it without eyes, doesn’t make it not right,” Curtin continued. “Dark matter is exceptionally robust empirically.”

But Miller, Assistant Professor in the Department of Philosophy, raised the point that empirically robust concepts in the past have been proven to be non-existent, such as the existence of luminiferous aether, a type of substance proposed to explain how light waves travelled through space, which was disproven in 1887 with the Michelson-Morley experiment.

After an in-depth discussion with Curtin and Luke, a professor in the Department of Physics, Miller noted that even if we cannot directly observe a concept theorized to exist, we can mitigate our concerns that the theory may be false by pursuing “multiple independent strands of evidence.” If each strand “independently demonstrates to us” that the concept exists, then we can be more confident that the theory works out as in the case of dark matter and dark energy.

The validity of using instrumentation

Sasha Manu, also a Physics and Philosophy specialist, presented the background and questions for the second topic of discussion: observation. “Our sense experience clearly constrains what types of observations we are able to make,” said Manu.

But scientists can create “high-profile discoveries” such as that of gravitational waves using “countless electronic connections and computer programs running in unison,” which lets scientists send a “probe into nature far beyond anything possible with the bare senses.”

What connects the “undeniably dissimilar experiences” of direct observation and observation using instrumentation, such that we “treat them in many ways as being the same.” Moreover, Manu asked if we are “justified in doing so.”

Luke opened the discussion by saying that he agrees that no direct observation occurs with our senses when scientists look for phenomena such as gravitational waves or the Higgs Boson, an elementary particle studied in particle physics. However, he says that he thinks “that’s what science is” using theoretical intermediaries to make observations of phenomena that are not directly observable.

He continued by explaining that every time physicists agree they understand something with a certain degree of confidence, they can use it as a basis or tool to explore other phenomena.

The nature of physical laws

Hannah Sousa-Fronenberg, a Physics and Philosophy specialist, asked the questions for the final topic of discussion: the nature of physical laws.

How is it that “real and abstract mathematical laws govern and influence the behaviour of regular physical objects? Do these real and existing laws cause physical phenomena to occur? Does this mean that the laws of nature existed ‘before’ the Big Bang?”

Miller opened the discussion, explaining that “there’s lots of different views on the issue,” but he wished to focus on two classes of them.

According to the first class of views, explained Miller, physical laws are “just kind of patterns in the way the world unfolds, and there’s nothing over and above that to say about how things happen.” And according to the second class, physical laws “actually govern the behaviour” of particles in the world.

21 Canada Research Chairs appointed at U of T

Federal award recognizes high-impact academic researchers across Canada

21 Canada Research Chairs appointed at U of T

In 2000, the Government of Canada initiated the Canada Research Chairs Program (CRCP) to provide funding and resources to researchers working at Canadian universities.

The funding promotes the work of promising researchers who are considered world leaders in their field. In addition, it attracts international researchers and retains talented home-grown individuals to position Canada as a world leader in research and development.

An appointment to the CRCP signifies and rewards impactful research.

The number of Research Chairs made available to each university is based on the value of federal research funding that a university has received over the past three years prior to the year of allocation. U of T and its partner hospitals currently hold 275 Chairs.

The CRCP appointment is broken down into Tiers 1 and 2, which are differentiated by the length and value of funding.

This year, 21 new and renewed CRCP Chairs were awarded at U of T. Eight researchers received Tier 1 appointments, with Dr. Daniel Durocher of the Faculty of Medicine having his Tier 1 appointment renewed. Among the recipients are researchers studying breast cancer, neural circuit development and function, developmental genetics and disease modeling, and experimental high-energy particle physics.

 

Below are a series of profiles on the new Tier 1 appointments and their research.

Dr. Rayjean Hung’s research aims to detect cancer in its early stages through examining individuals’ genomic and molecular profiles.

“This Chair award will form an important foundation of my research program in the next 7 years, not only to continue the core of my current research program but it will also help us to embark on novel initiatives that are considered high-risk and high-reward,” wrote Hung in an email to The Varsity.

Dr. Brian Ciruna is a professor in the Department of Molecular Genetics who previously held a Tier 2 Chair. Ciruna’s research includes studying the molecular genetic regulation of embryonic development. Using zebrafish models, his team’s work is directed towards understanding the role that the planar cell polarity signalling pathway — a mechanism responsible for proper tissue development and cell to cell communication — plays in the growth and development of the embryo.

Dr. Alan Davidson is a Chair in researching and developing bacteriophage-based technologies. Bacteriophages are viruses that infect bacteria. In addition to understanding the interactions between bacteriophages and their bacterial hosts, Davidson and his team study the CRISPR-Cas systems, and investigate their inhibitors and their potential in helping understand how bacteria resist bacteriophages.

Dr. Dana Philpott is the Acting Chair in the Department of Immunology. Philpott’s team seeks to investigate the Nod-like receptor family of protein. Of particular interest is the role that these proteins play in autoimmune disease and in the adaptive immunity to bacterial infections.

Dr. Pierre Savard is a particle physicist in the Department of Physics. A Scientific Associate with the European Organization for Nuclear Research, his work focuses on the production and behaviour of the Higgs boson particle.

Dr. Mei Zhen is a neuroscientist at the Lunenfeld-Tanenbaum Research Institute and is cross-appointed to the Departments of Molecular Genetics, Physiology, and Cell & Systems Biology. Zhen’s research uses the worm C. elegans to reveal deficits underlying human neurological disorders. Her lab works in the field of connectomics — the the study of neural connections known an connectomes — with applications in understanding the development of the human nervous system and its diseases.

Dr. Rama Khokha is a renowned breast cancer researcher at Princess Margaret Cancer Centre. With a wide scope in solving biological problems associated with cancer, the research led by her group includes a focus on stem cells, having also setup workable mouse and human cell platforms for cancer research.

Dr. Lisa Strug is focused on developing new methods to analyze multi-omic data that can help in the creation of diagnostic models for diseases, including cystic fibrosis and genetic epilepsies.

“I am inspired by — and committed to — the people involved: The patients and their families who suffer but continue to contribute their time and specimens even when the research may not immediately benefit them; the foundations who tirelessly raise money and support the patients and families they aim to serve; and the students who I train, who are so committed to a career in biomedical research and work tirelessly to push the science forward,” wrote Strug in an email to The Varsity.

“Choose something you love to do and that you believe is important, and then work hard at it,” Strug advises young scientists. “Be resilient in the face of adversity, be determined, have a strong foundation in your discipline and always practice your science with the utmost scientific integrity.”