Tuesday, March 17, 2015

Magnetism the Most Magical of Forces

Nothing impresses a child more than magnets.  OK, maybe balloons, but magnets are a close second.  Give two magnets to a five year old and that is a solid hour of entertainment right there.  The magnetic force is not like the 'ever-present' gravity in our day-to-day lives.  It seems to be the result of some special, 'magical' force that we observe from time to time.

At the start of my electricity and magnetism course, I usually emphasize that although the electrostatic and magnetic forces are of the same family of forces, they must not be confused as the same thing.  The average person interacts with both of these forces daily and has little understanding of either.  It takes a while to wrap one's head around magnetism, but let's give it a try...

The mere presence of a charge creates an electric field, which can exert an electrostatic force upon another charge.  This is the basis of electrostatics.  In order for a magnetic field to be produced, charge must be in motion.  It then follows that for a charge to experience a magnetic force within a magnetic field, it too must be in motion.  This is the basis of magnetism.  So, whereas all charges produce and respond to electric fields, only those in motion produce and respond to magnetic ones.

The electrostatic force acting on a charged particle in an electric field is quite straight forward:

Here, charge q responds to electric field E.  What makes this force kind of intuitive is that the force points along the same axis or exactly opposite to that of the field (depending on the sign of the charge).  Contrast that with the magnetic force, which acts on a charged particle as follows:

Friday, December 19, 2014

The Physics of "Gravity" and "Interstellar"

Hanukkah is a Jewish holiday celebrating a miracle whereby oil sufficient for just one day burned for eight.  Over this past week, an entirely different miracle took place: I, a father of two young girls watched two movies, none of which contained a single princess.

I really got my nerd on: I rented "Gravity" and then went to the theater to see "Interstellar".  Both films feature a lot of physics, but they could not be more different.  "Gravity" is a ninety minute expedition featuring orbital mechanics, while general relativity weaves its way through the three hours of "Interstellar".

You are probably expecting me to dissect these two films and expose all of their scientific inaccuracies.  In truth, I enjoyed both of them immensely, but would like to address one major problem with each one.

Wednesday, December 10, 2014

Deep Breaths During Exam Time

Over the past weeks and months, I have witnessed some distraught students.  Young adults who walked into the semester cool as a cucumber are hitting the finish line exasperated - not all of them, but many.  A few have asked me for advice, and all I can seem to muster is "Breath".

I thought that I would strive here for something deeper and perhaps more helpful than this.  At the same time, I'll toss in a science metaphor, cause that is sort of my thing.

We are all aware of the need to manage our stress level.  Everyone has their own coping mechanisms for this, so I won't say "Go to the gym" or "Get more sleep" - it's good advice, but I want to focus instead on the bigger picture.

One thing that has been important for me is setting reasonable expectations.  I was not always good at this.

Thursday, November 13, 2014

Rosetta Mission and Noodle Bridges

A couple of unrelated engineering feats occurred yesterday, and I'd like to address them.

First off, the European Space Agency (ESA) succeeded in landing a probe (Philae) on a comet (67P) for the first time in history.  The level of difficulty of accomplishing such a thing is truly off the scale.

A comet is tiny, 'celestially speaking'.  The mass of 67P is about 10^13 kg.  That's a one with 13 zeros attached to it.  But that makes its mass about 100,000,000,000 times lower than that of a typical planet.  Another aspect that makes docking with such a body tricky is its irregular, peanut-like shape.  It is far from a sphere (largest dimension about 5 km, and smallest about 2 km).  Still, regardless of where you land on this comet, the surface gravity is on the order of 0.001 m/s/s (about one ten-thousandth that of the Earth).  So, if you want to dock, you'd better hang on, because escape velocity is only about 1 m/s (jump, and you now orbit the Sun).

Wednesday, November 5, 2014

My Halloween Costume: A Free-Body-Diagram

Last week, on Halloween day, I came to work dressed in a costume...

As you can possibly tell, I was dressed up as a free-body-diagram.  All the forces acting on me were identified by force vectors (large red arrows) at their respective points of application.

I had the gravitational force, mg, acting at my center of mass, and then a reaction load at each foot.  In the picture above, I also posed with a reaction coming from the wall I was leaning against.  Hanging around my neck is a list of assumptions (this costume is valid under the following conditions...).

So, there you have it.  If you were wondering if I'm a nerd, you now have your answer.  I think even my physics teacher colleagues found it slightly nerdy - that speaks volumes.

I got some nice reactions from my students that day, though as I walked through the halls, non-science folks gave me some strange looks.  I spared my family any embarrassment by removing my costume before I returned home.

Thursday, October 2, 2014

IAC 2014 - Day 4: My Presentation

Today, I give my presentation about the static deformation of the space elevator tether due to the presence of a climber.  I have decided to open the talk with a picture of the CN tower.  You see, its been a foggy week of weather in Toronto, and I have taken some time to stare up at the tower from its base.  The top of the tower disappears into the fog - no end in sight.  The sight appeals to me for obvious reasons, so I have to mention it to the other space elevator aficionados in attendance.  Imagine a time, decades from now, when there will be no end in sight to such a structure, even on the clearest day.

I present a summary of my most recent research.  One of the most surprising things is that this fundamental mechanical analysis had not been documented yet.  You station a climber at some location on the tether, and what will the new equilibrium state of the tether be?  Will it stretch more or less and in what locations?  What are the changes in stress and tension throughout the tether?

The results are as follows:

Wednesday, October 1, 2014

IAC 2014 - Day 3: An Independent Review of the Mars One Proposal

I know I should be writing about day 3 here, but yesterday, after submitting my day 2 entry, I attended perhaps the most compelling symposium of the conference; it was all about manned missions to Mars.  I can say with some confidence that nothing today will top it, so this entry will focus entirely on the exciting presentations that took place yesterday afternoon.

Most of the conference rooms hold about 150 people in it, and it is rare that a room is more than half full.  But I had a feeling that this symposium about Mars missions would draw interest, and sure enough, it spilled out the back of the room.  The first few talks were rather benign: A plan to land on Mars by 2030, recommendations by several experts in the field on planning the first mission, and a commentary on the social and legal structure of the first Martian society (nothing more compelling than reading the novel Red Mars).

The fourth presentation was introduced by the session chair as 'something special', and he was right.  Five students from M.I.T. wrote a paper challenging the proposal for Mars One.

Tuesday, September 30, 2014

IAC 2014 - Day 2: An Ode to my Yoda

Today, I will abandon the approach of summarizing my experience at the IAC, and focus solely on the morning session on space structures.  In particular, I want to highlight the talk that was given by Professor Arun K. Misra, my mentor.

He is the Yoda to my Skywalker, the Dumbledore to my Potter.  Much of my knowledge of space research and the reason for my initial interest in space elevators came from Misra.  He supervised my Masters project from 2004 to 2006, and we have published several papers together since then.  He is kind and acts with integrity, and has served as a model for professionalism in my eyes.

I will never forget my initial meetings with Professor Misra in 2004, when I expressed my concern that the project will be difficult for me to carry out.  He quietly laughed, and said "You know, building the first space elevator will be hard... Your project, studying its dynamics, will be easy."  He curbed my definition of hard work, and in so doing, helped me mitigate a common fear that young professionals commonly face - that of daunting tasks.

Monday, September 29, 2014

IAC 2014 - Day 1: Blast Off

"Dude, Buzz Aldrin just walked by..."  This type of thing happens at a major space conference, but as someone who has only been to a few such events, it stopped me in my tracks.  I paused, and considered the significance of the moment when that man walked on the moon forty-five years ago.  Aldrin is 84 years old now, but he still moves well (fast enough that I decided not to chase after him for his autograph).

Today, the International Astronautical Congress kicked off with an exceptional opening ceremony featuring a couple of astronaut MCs and Cirque de Soleil performances.  However, it was the musical performance of Peter Katz that really stole the show - he spoke to the 3,000 audience members about the importance of dreaming and following those dreams.  He then went on to blow everyone in attendance away with his amazing voice and songwriting; that was my friend Peter Katz, upstaging Cirque de Soleil.  The event closed with a fine speech by astronaut/rock star Chris Hadfield.

At the convention centre, it is hard to keep up with the fascinating information that constantly flies in all directions.  During the head of agencies event, I learned that only 40% of spacecrafts sent to Mars actually make it there.  It takes most countries many tries to succeed.  India's space agency (ISRO) recently made history by succeeding on a Mars mission on their first try.

Monday, September 22, 2014

The 65th International Astronautical Congress

Next week, I will be attending and presenting at the 65th International Astronautical Congress (IAC).  It is the annual space conference with the highest attendance in the world.  Thousands of experts in industry and academia from all corners of the world with gather to share expertise in anything and everything space-related.  The event will take place between Sept. 29 and Oct. 3 in Toronto, Ontario, at the Metro Toronto Convention Centre; the location changes every year - it's like the Olympics for nerds.

The scale of the event is kind of mind-boggling.  There will be 180 symposiums, each on a specific space topic.  Each symposium consists of anywhere from five to ten 14-minute talks.  Therefore, there will be about one thousand presenters and more than one thousand presentations, as some speakers will be giving several talks.

It is impossible to physically attend more than 6% of these talks.  At any given time, there are eighteen symposiums taking place.  When attending such a conference, one must make choices; there will be interesting talks missed because something more interesting is taking place at the time.  Spinning it more positively: there is always something amazing going on.