Hi everyone,
I have started a summary book which contains plain-language descriptions of the material we have covered so far in the syllabus. This should be useful in studying for Tests. I will update the summary file each week as we go through the academic year, so please check back at this link often.
I hope this helps. 
Cheers,
Prof. Peet.
Hi everyone,
An eagle-eyed student in our class noticed that one of our UofT particle experimentalists will be giving a lecture on campus on Tuesday (September 25th) which will be helpful in writing your Essay 1. For more information, please go to the Galbraith Society’s webpage for the event.
Cheers,
Prof. P.
Hi everyone,
Next week we will be focusing on physics insights from two extremely famous physicists from history: Isaac Newton and Albert Einstein. Here are my notes.
Newton is famous because he figured out new laws of motion and gravitation that revolutionized our understanding of terrestrial and celestial motion. His insights systematized a huge heap of astronomical data, and are still technologically powerful enough to land men on the Moon! In particular, his theory of Universal Gravitation explained the motions of planets in our solar system, which had puzzled people for millennia. Along the way, Newton (co-)invented calculus. He was an intellectual giant in his day, and is still a physics rock star over 350 years later.
Einstein is famous because he also changed the way we think about the universe. In his case it was because he developed Relativity, a bit over a century ago. This week we will talk about Special Relativity, which is all about how the motion of objects differs in different frames of reference, and how to translate observations from one reference frame to another. Einstein’s central insight was that the speed of light is the same in all frames of reference. From this, he was led to the discovery that time is not absolute: it is RELATIVE. This startling conclusion will take some time to digest, and will be illustrated by two examples: (1) Rollerblader Relativity and (2) the Twin Paradox. What we will find out is that one observer might measure different times and lengths than another, but they are both right. It all hangs together mathematically because of the constancy of the speed of light.
Keep in touch as you start researching your LHC/Higgs essay. I think it should be straightforward, but if it isn’t, I’m here to help.
Cheers,
Prof. P.
For next week’s class, please read:-
Next week we will begin discussing gravity in some detail, by introducing Isaac Newton’s incredible insight of over three centuries ago that the very same gravity force is responsible for the motions of celestial bodies and for the motions of human scale objects like baseballs on Earth. We describe the inverse-square behaviour of Newton’s Law of Universal Gravitation.
Newton’s theory of gravity is very powerful, with the ability to explain observations like Kepler’s Laws of planetary motion (planets move in elliptical orbits, and each orbit sweeps out equal area in equal times). Newton’s gravity is precise enough to land humans on the Moon.
One weakness of Newton’s gravity theory, however, is that it assumes that the speed of transmission of gravity is infinite. This gives rise to nasty causality problems, which is part of what drove Einstein to refine Newton’s theory of gravity by formulating Relativity. Newton’s theory also predicts a deflection of light by gravity that is experimentally incorrect; Einstein’s refinement got it right.
Einstein’s fundamental insight was that the speed of light is invariant – the same in all frames of reference. This deceptively simple looking proposition is amazingly deep, in that it forces us to rethink our conventional, low-speed-based, intuition about how velocities should add and about how every observer should measure the same time. In fact, as Einstein showed theoretically and decades of experiments have shown since, time is relative (not absolute) and velocities which are a significant fraction of the speed of light do not add simply.
We demonstrate how time dilation works in a very simple example. By drawing a straightforward diagram and using simple trigonometry without any equations, we show that – because the speed of light is the same in all reference frames – clocks look like they are running slow to an observer in relative motion.
We also set up and explain the famous Twin Paradox. In particular, we explain that it is the acceleration of the astronaut twin that breaks the apparent symmetry between the twins. The astronaut twin ages less quickly than the homebody. This kind of theoretical prediction of Relativity has been exhaustively tested in the laboratory and found to work perfectly. So it is real life, not “just a theory”!
This is the first of three written assignments in Fall semester.
Due date: Wed 03 Oct 2012 by 2:10pm
N.B.: The following description may seem a bit long at first, but don’t panic! I deliberately designed it a bit like a FAQ, so that it would be straightforward for you to figure out what I expect. Just take a deep breath, read the instructions carefully all the way through to the bottom, and then ask me if you have any remaining questions.
Note: before you start, you may wish read my Essay Grading Rubric. Here’s the executive summary: essentially, I grade for two things: (1) physics accuracy, and (2) how well you explain things (pedagogy).
Your primary source of information for our course is my Notes, which I make available here on this web site. Our required textbook is also likely to be useful in writing your essay. (The index of Greene’s book shows where to find relevant pages.) Another good book is Dan Falk’s book “Universe on a T-shirt”, which should be on short-term reserve in Gerstein science library.
Reputable, understandable sources of online information about the LHC include:
See also
Please note: Wikipedia is NOT an acceptable source/reference (for this or any essay in this course). Why? (a) Its accuracy on modern physics is dubious, because bona fide experts in theoretical physics are FAR less common online than unqualified cowboys who think they can do theoretical physics; and (b) the level of technicality is often mismatched to what we need in this course. You may of course use Wikipedia as a mechanism of finding reputable sources.
If you are in doubt about the legitimacy of a source, please ask your friendly professor by email. That is what I am here for.
Your assignment must be two to two-and-a-half pages in length, including references.
Make sure that your assignment is typed, no more densely than single spaced, on US letter-size (8.5 x 11 inch) paper, with one to one-and-a-half inch margins, in a plain font (e.g. Verdana) of size 12pt (twelve points) or larger, in black colour.
Please use the APA system of formatting references.
Note: do not use a separate title page. This is a waste of paper. Just write your student name and number in the header (or top line) of page 1 of your essay.
Stylistically, please write this essay conversationally – as if you are verbally explaining this stuff to your favourite artsy cousin who knows little or nothing about science. Use the first person and the active voice.
Essays must be handed in before the deadline in both of the following two ways, for the safety of students (and instructor):
(1) an electronic version, with your name and student number on it, sent to the prof by e-mail from your official UofT email account;
(2) a printed version, with your name, student number and signature on it, handed in to the prof personally at the beginning of class. This must be stapled together properly or it cannot be accepted.
At least one of the two versions must be handed in before the deadline – preferably the electronic version.
The electronic document formats I accept are: rich text format (.rtf), Portable Document Format (.pdf), plain text (.txt), LaTeX (.tex).
For security reasons, I recommend against Microsoft Word (.doc or .docx) as a file format, but will grudgingly accept it. LibreOffice is a great alternative to Word for editing .rtf files; it works on Mac Windows and Linux and costs $0.
Compliance with all UofT academic integrity guidelines is, of course, compulsory. For clarification of what is expected of UofT students, please carefully study the handouts on Academic Integrity (the Writing handouts will also be useful). For example, do remember to properly quote and reference all sources you use, but don’t cut-and-paste content from the internet. Please read How Not To Plagiarize.
I will run essays through the University’s TurnItIn.com system for detecting cheating in essays. All this does is checks whether you have lifted paragraphs or phrases straight from common sources without referencing properly. If you don’t cheat, you have absolutely nothing to worry about. If you would prefer not to participate with Turnitin, you must provide alternative evidence that your essay is your own work. You must discuss this with me in person; I require at least two rough drafts along with the finished essay.
You are also required by UofT regulations to print, fill in, and sign the Essay Checklist. This is compulsory.
Procrastination is silly. Start early – don’t leave it till the night before.
If you have any questions or concerns about doing this assignment, any questions at all (including computer related questions), please contact your friendly professor for advice. I am here to help you – so please take full advantage!
Hi everyone,
A student emailed me recently mentioning that they find the idea of giving oral presentations a bit scary because they are shy. The advice I thought up for them in response is actually applicable to the whole class, so I am posting the information here in the hope that it will benefit everyone.
My basic message is: don’t be afraid. Here’s why.
In each of the courses I teach, I work to be scrupulously fair to each individual student and to the class as a whole. All I ask in return that each of my students works to be scrupulously fair to all of the other students in our class. Part of that means respecting the UofT Code of Academic Integrity. Another part has to do with communication style and listening skills.
In most undergraduate classrooms, students say a lot less than professors, and student-student interaction is weak. But in a 199Y seminar course, the communication styles of the students are centrally relevant. There is always a wide spectrum of extroversion/introversion: some students are more talkative while some others prefer to think more carefully before volunteering an answer to a question. Our diversity as a group is entirely natural, and it is an asset academically.
As the professor, I work to ensure that everyone gets to make valuable contributions to the intellectual life of our seminar class — regardless of their communication style or their academic background.
A few basic ground rules help to ensure courtesy, respect, and inclusiveness. This is mostly just common sense.
I enforce my classroom code of conduct fairly, even-handedly, and without personal bias. The vast majority of the time I don’t have to do anything at all. But when a disruption does occur, I deal with it quickly and appropriately and I do my best to save face for all parties.
Everyone in my past 199Y classes got nervous about giving oral presentations on modern physics — from the shyest ESL student to the former high school debate team member. Why? Having debating experience doesn’t help much, because I don’t grade you on the quality of your rhetoric. Instead, I grade on two different criteria: (1) physics accuracy and (2) quality of pedagogy. The upshot is that everyone in the class is really in the same boat. (The boat called “HMCS Nervous”.)
The Code of Conduct I mentioned above for classroom discussions is extended by one further rule during student Oral Presentations, to make things easier for presenters. It is:-
Undergrad students get nervous about giving presentations. Grad students get nervous about giving presentations. Postdoctoral research fellows get nervous about giving presentations. Even professors get nervous about giving presentations. In each case, the solution is PREPARATION and PRACTICE in advance.
Prof. Peet’s Secret Formula for Successful PMU199Y Presentations Without Sleep Loss:-
Well, I hope that helps.
Cheers,
Your Professor Peet.
Note: this announcement has absolutely nothing to do with the course. Paying attention to it is entirely voluntary. Ignoring it will not affect my opinion of you at all.
Do you bicycle? I do. Since I moved to Toronto in 2000, I have consisently refused to own a car. Everywhere I go in the city I ride a bike as my vehicle, or take public transportation, or walk. Cycling is good for the environment, it reduces traffic congestion, and it is good for my health.
Last week I bought a new bike for the first time in years, which was really exciting. Woot! It has taken me a total of twelve and a half years since my Mammoth skiing accident to get back on a regular-frame bicycle, in a personal victory of sorts. Here is a picture of my new steed on the evening I brought it home from a local bike shop, last week after class office hours. The weird handlebars are needed to accommodate my damaged shoulders/neck/back. I’ve already ridden it to the Toronto Islands this past weekend.
If you ride a bike in Toronto, and if you would like our streets to become safer for cyclists, then I warmly invite you to join Cycle Toronto. Cycle Toronto is a diverse member-supported non-profit community organization that advocates for a healthy, safe, cycling-friendly city for all. (It is badly needed: Mayor Ford wants to spend a quarter of a million dollars of taxpayer money to remove bike lanes on Jarvis St in November!) I have already put my money where my mouth is: I am a Founding Life Member of Cycle Toronto.
Student memberships in Cycle Toronto cost $20/year. (This reduced rate became available after a number of us advocated for it.) With your membership fee, you get (a) really decent people who know their stuff advocating for your safety as a cyclist, and (b) a number of member benefits - mostly discounts at local bike shops.
If you would like to join Cycle Toronto, I invite you to do so at my Refer-A-Rider campaign page. Invite your friends to join up using the same link. If I end up placing in the top three in the contest and win a prize, I will donate that prize to one of you – by making a random draw from the list of all students who signed up as Cycle Toronto members through my Refer-A-Rider page. First prize is a whole bike.
Don’t sign up because I offer the slim chance of winning a prize. (The odds are much better than in any Lotto draw, but whatever!) Sign up because you believe in cycling infrastructure for your city. Cycling is a great way to help your health – both physical and emotional – even if, like me, you’re a person with disabilities.
Ride on!
Hi everyone,
It was a true privilege to meet you all today in our seminar. I’m thrilled to have a class full of such talented people!
Here are my class notes for September 19th.
Looking forward to our next seminar very much. See you then.
Cheers,
Prof. Peet.
Hi everyone!
Next week on September 19th we will be talking about particle physics, a.k.a. subatomic physics. During our two-hour discussion, we will talk about the building blocks of subatomic particles together with the forces that act on them. The fancy physics name for all of this is the Standard Model of Particle Physics. It’s just like the Periodic Table for Chemistry, except that it applies to subatomic physics instead.
Please read the following before coming to class:-
This week is all about particle physics. We will begin by discussing how physicists tell particles apart. This is important in the same way that being able to tell your kids apart is important! A clever idea is to pick invariants – properties of the subatomic particle that remain unchanged regardless of changes in perspective (like speeding up or rotating around). It’s like recognizing your friend Sam by the shape of his face: you can recognize him at all kinds of different angles and when he’s running or sitting still, but he’s still the same Sam.
The three types of invariant used to classify subatomic particles are: the mass m, the spin s, and the force-charges q. Mass can be anything from zero to large, but spin is quantized, meaning that it can only take on some very specific values: integers or half-integers, measured in units of a physical constant named h-bar. The values force-charges can take depends on the force (and we will not have time to delve into this detail). An example of a force-charge is the electric charge.
Nature makes an important distinction between bosons, which have spin 0, 1, 2, 3, … in units of h-bar, and fermions, which have spin 1/2, 3/2, 5/2, 7/2, … in units of h-bar. Up at high temperatures when particles race around with a lot of average energy of motion (kinetic energy), bosons and fermions behave pretty much the same. But when you’re down at extremely low temperature, it matters hugely whether you’re a boson or a fermion.
The Pauli Exclusion Principle (PEP) is a really important property of fermions: it says that “no two fermions can be in the same quantum state at the same time”. In plain language, this means that fermions have elbows. You simply cannot crowd them on top of one another: if you try, it never works. This fact helps explain (among other things) why atoms with more protons in their nucleus are physically larger. Bosons have no such requirement.
Incidentally, the name “fermion” is a salute to the awesome but dead Italian physicist named Enrico Fermi. Similarly, the name “boson” is a salute to the awesome but dead Indian physicist Satyendra Nath Bose.
Matter (a.k.a. stuff) in particle physics is composed of fermions, while the force-transmitter particles are bosons. It’s a bit mind-bending to imagine how exchanging a particle can represent a force, so in class we will discuss the Ice Skater Analogy to help visualize it. You can see more about this analogy in the online notes which I will post soon.
There are four different forces known in Nature – gravity, electromagnetic, strong nuclear and weak nuclear. Gravity holds you on Earth and Earth in orbit around the Sun. The electromagnetic force describes electricity and magnetism – which you can see are connected if you watch a compass needle move around during an electrical storm! As we discussed at the end of our Sep 12 seminar, the strong nuclear force holds the atomic nucleus together. You can see the power of the strong force when you set off a nuclear bomb. The weak force is responsible for the kind of radioactivity that powers our Sun. So even though it’s weaker between two subatomic particles than the strong force, it’s still mighty.
For now we’ll just mention that the electromagnetic and the two nuclear forces have spin one messengers, while gravity has a spin two messenger particle. The Higgs boson (responsible for mass of quarks, leptons and the weak bosons) has spin zero. All of these particles have been seen and studied in particle accelerator laboratories.
Another couple of big words used by particle physicists are hadrons and leptons. These come from the Greek and basically mean “heavy little bugger” and “light little bugger”. (Well, not quite! ) Hadrons is the name particle physicists use for baryons and mesons, which are colourless subatomic particles made only out of quarks and gluons. All hadrons feel the strong, or colour, force. Leptons, on the other hand, are unaffected by the strong force. The lepton group is composed of electrons and their heavier cousins the muons and taus, plus their associated neutrinos: the electron neutrino, the muon neutrino, and the tau neutrino. While leptons don’t feel the strong force, they do feel the weak nuclear force. Every particle with an electric charge feels the electromagnetic force. Every particle with energy – i.e. every subatomic particle known in Nature – feels gravity.
We will close by giving a lightning tour of the Large Hadron Collider (LHC) based at CERN near Geneva, Switzerland. The LHC and the Higgs boson recently discovered there will be the subject of your first essay. I will provide a set of reliable sources about the LHC and the Higgs boson to help you get started.
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