Actions have consequences

Throughout our lives, we make decisions which change the rest of our lives. Sometimes it is fairly obvious that a decision will end up being significant, but other times we have no idea how much things will change as a result of what we do. Mira went to the same summer camp for years and eventually ended up as the bus counselor on the bus she rode. The bus route was overcrowded and probably should have been split in half to be safer. She told the camp that she wouldn't come back unless they split the bus, and they didn't. So that summer she ended up working at Old North as a docent instead. Which led to her learning to ring church bells. Which is how we met. Some person I don't know and will probably never meet can claim some credit for me meeting my wife. Life is random like that.

I borrowed a friend's car today to drive to an interview.

When I look back over my life, I can see all kinds of decision paths like that. Some seemingly minor decision sets up a chain of events that eventually changes everything. And I'm sure that there are many more that I am unaware of. A stupid little essay that I wrote in my 7th grade math class because the school board decided that even math classes should have essays was the first step in the process that led to me finishing high school a year early. Which probably changed where I lived at MIT as an undergrad (and possibly even what college I went to). Almost all of my current friends in the Boston area are people that I met either directly or indirectly because I lived at Random. I probably would have met some of them anyway, but who knows? Almost my entire social circle is people that I might have never met if I hadn't written that essay.

While driving north on I-95, I noticed some odd movement in the cars ahead and to the left of me. Then I saw a car that was sideways at the left edge of the road (perpendicular to traffic with wheels down, not on its side).

Some major decisions obviously change our lives. Where we live, where we work, where we go to school all change who we meet and who we spend time with. People tend to agonize over these decisions, as though they are more important. But then someone decides that math classes don't need essays, or that adding a bus is a good idea. And all that careful planning is overwhelmed by the randomness of life.

This seemed like a good time to slow down. Then the sideways car was in front of me. This seemed like a good time to stop. Unfortunately, momentum can't disappear in an instant.

I have been very actively applying for jobs for the past 5 weeks. I'm mostly concentrating on two totally different areas that I think would work well. I know how to connect either of them to my long term plans. I'm not sure which one I like better. One of them probably requires us to leave Boston. There are also some other possibilities that I'm considering which don't clearly connect to my long term plans, but which I can probably manage to make work through creative execution of the secondary backup plan. I'm not actually expecting to have multiple simultaneous job offers, so I will probably take the first one I get, but I might also end up actually getting to make a decision. It's interesting to see how very different the the hiring time scale is for different industries.

The result was a low speed collision between the front right corner of the car I was driving and the driver's side door of the other car. There was a brief period where I thought I would stop in time before I heard and felt the impact.

And then today there's this accident that occurs in front of me and spreads out in a way I don't manage to avoid. When I finished telling the police officer what happened and said "I tried to stop, but I couldn't manage to" he replied with "Yeah, well you're not superman. You clearly weren't at fault." So I guess there's that at least.

But when I thought about it more, I realized that if I had hesitated for 1/4 second, it wouldn't have been a low speed collision. It's likely that the other driver would have been injured. If I had hesitated for a full second, he possibly would have been killed. If I hadn't slowed down at all, then I probably would have been next to the accident by the time his car came across the highway, and it would have been my driver's side door getting hit, and I would have possibly been injured. There was some 2-3 seconds of my life where my actions changed the outcome from me being probably injured to someone else possibly being killed to that person being probably injured to just cars being damaged. Which can be fixed.

Every moment of every day, we are making decisions. Most of the time, we won't know for years which of these decisions will end up mattering. And we never find out about the decisions that would have been important if they had been made differently. But sometimes, we know that a decision mattered right away.

I have this habit of considering what my life would be like if I had done some particular thing differently. It's one of the things I do while I lay awake at night sleeping (I'll explain how that makes sense some other time). But there's a limit to how far I can push things with any kind of certainty. It's easy to work out things that would have prevented something from happening. It's much harder to understand what would have happened if something had been enabled.

The title of this entry is the opening line to the first episode of the TV show "Dollhouse." That show was on track to be my all-time favorite show for the first 1.5 seasons. Then it switched from being a show about some interesting psychology topics into a show about defeating the evil corporate conspiracy. Which is fine, but not nearly as appealing.

Why I studied astrodynamics

There are two stories from my childhood that provide good foreshadowing of my interest in astrodynamics. Mira told them at my graduation party, but for those who were not there:

First Story:

When I was two, we were visiting my grandmother in Florida. My mom wanted a break from her older kids (my little sister was about 6 months old), so my dad took us to watch a shuttle launch (this ended up being the only shuttle launch I saw in person). I was very excited with everyone else before the launch, and counted down with everyone. But then, as I watched the shuttle go up higher and higher in the air, it became clear that I was concerned about something and wanted to hide under the seats. My dad asked what was bothering me, and I explained that when I threw a ball in the air, it would come back down and hit me in the head. That thing over there was going up really high and looked really big, and I didn't want to get hit when it came back down.

Second Story:

When I was 5, Halley's comet was in the proper part of its orbit to be seen from Earth. I heard about this comet for several weeks as it came closer and closer. I remember being excited about this thing that was flying around the sun that only came close enough to be seen every 75 years. Then Challenger exploded. Somehow I managed to work out that the shuttle had been hit by the comet based on what the news was saying. I was very upset that the scientists at NASA had not figured out where the comet was going to be and let the shuttle fly into it. I lost interest in looking at the comet, because I was upset that it had blown up the shuttle.

And now I have completed my degree work in astrodynamics. I can make sure that spaceships will not fall on children's heads and will not fly into comets.

Just for clarification, astrodynamics is the science of determining orbits and spaceship trajectories. People who study how stars work are studying astrophysics, which is basically unrelated. As best as I can tell from what my parents have said and NASA's launch records, the shuttle launch was the first launch of Challenger, so these stories are about the first and last launches of Challenger. And I first heard about the broken O-ring that actually destroyed Challenger six years after the explosion, and was very surprised at the time to discover that the space shuttle had not been hit by a comet.

Enough Mens, time for some Manus

After spending 8 years doing theoretical astrodynamics (and the last four of those were applying theoretical math that nobody in the Eastern half of the US understands), I needed to spend some time doing something more practical and hands-on. I needed to construct things that could be touched and looked at. There was a brief period where Mira and I considered buying a broken house so that I could rebuild it, but that didn't end up working out. So instead, I had to make do with smaller projects.

Project 1: A hat for Jesse
Mira knits all the time, but I only knit occasionally. In early November, I decided that I wanted to knit a hat for Jesse. Mira had some yarn leftover from a sweater she had made for him, so I started a hat that would match the sweater. Then Mira went into labor. I spent a fair bit of time in the hospital working on the hat, and managed to finish it before we went home, so Jesse was able to wear a matching hat and sweater made by his parents when he left the hospital.

Working on Jesse's hat while holding Jesse in the hospital

The matching hat and sweater on Jesse at about 10 days old

New skills learned: knitting in the round, binding off for a hat

Project 2: Socks for Mira
I told Mira that for her birthday and Chanukah, I would knit her whatever she asked for. She asked for socks, picked out some yarn, and picked out a pattern. I have finished the first sock and I am about halfway down the ankle on the second sock. It turns out that socks have a lot of stitches and therefore take a long time to finish. And this yarn is fairly dark, so I can only work on these when the lighting is good. I don't have any pictures of these yet.

New skills learned: turning a heel with a heel flap, binding off a sock toe

Project 3: A hat for friends' child
Some friends were moving away this fall, and as a going away present, I made a hat for their daughter. This hat was double knit, which is a process of knitting that creates two layers of fabric simultaneously. For some reason people seem to think this is difficult (even Mira has never tried it), but really it just involves having more yarn tangled around your hands. I also designed the pattern. Did you know that every web site that lists hat sizes for toddlers has different numbers for how big their heads are? I kind of guessed what a good size would be based on the range of numbers I could find, put ribbing on the bottom in case it was too big and then made the hat taller in case it was too small (a double knit object is very stretchy, but stretching it in one direction makes it smaller in the other direction). She seems to like her hat, which is nice because two year olds are totally unpredictable and she could have just as easily decided she was unwilling to ever wear it.

One of the nice things about double knitting is that the hat is reversible. It really is like making two hats, but they are attached to each other.

New skills learned: double knitting, knitting pattern design

Project 4: Dresses for Mira

Nursing with the dress on.

Mira and I went to a Bar Mitzvah two weeks ago. Mira was having trouble deciding what she could wear that would be fancy enough while still allowing her to nurse Jesse. So we decided that we would make dresses that would be modified to allow nursing while wearing the dress. Mira helped with the first dress (the black and white one), but then realized that since she is a responsible adult and actually has a job (unlike me), she did not have time to work on sewing. So I finished the first dress and made the second one on my own. The dresses both came out very well and we expect Mira to wear them many more times. We will probably be making more clothing in the future. Sewing in zippers is not nearly as complicated as it seems to be when you read a written description of how to do it. Videos are much better. Also, French seams are awesome.

New skills learned: French seams, zipper installation, sewing in elastic bands, using fusible interfacing, modifying clothes for nursing, adjusting a dress pattern to fit a particular person

Project 5: New shirts for Mira
My sister made nursing turtlenecks for Mira. Winter is coming to an end. Mira needs summer nursing shirts. I will probably make them in May.

Project 6: New Bookcases
This one is still in the planning phase. We have about 800 books. Most of them are in four bookcases in our living room. Mira does not like these bookcases. I like carpentry. I have half-drafted plans for what I want in my head, and hope that I will actually build these bookcases some time this year. I am intending to put doors on the bookcases, so that the small toddler we will have next year can't pull all the books off the shelves. I am also thinking of mounting our television on a bookcase door and putting the TV related electronics (VCR and such) behind the television, with the cords nicely contained. And maybe I'll throw in a coat closet while I'm at it. This is still an imaginary bookcase, so it has all kinds of great features. We'll see what actually happens.

Friday, February 25th

It is the changes and transitions in life that are always the most interesting parts. My life has always been full of changes. The longest I have ever lived in the same building is about 8 years. I went to five different schools before college. My hobbies also seem to be all about changes. Change ringing is the music of combinatorics, square dancing is the rhythmic moving from one formation to another, and ba gua is a martial art focused on stability in transitions. Even my research is about how to get from the initial point to the final point, and what the best transition is. Then there are the deeper changes within myself that happen all the time. Two of the most significant transitions in my life were centered around Friday, February 25th. I remember both of those days and the events which occurred on them very clearly.

The first day (17 years ago) I remember laughter, smiles, balloons, and rain as I waited to be picked up with my cello. It was a day of beginnings, a day of happiness. The spring that began then was one of the happiest seasons of my life, in which basically everything just went the way I wanted it to (this also happened in the fall of 1999, fall of 2003, and summer of 2007). That weekend and the following week were just about perfect.

The second day (11 years ago) I remember snow, a turning away, a question, an answer that wasn't an answer, "heads will roll", a ball, and a pair of parallel conversations. It was a day of endings, a day of sadness. The spring that followed was the worst season of my life, in which almost nothing went well. There was a certain happiness and optimism that I had had which faded out and never fully returned. I lost touch with quite a few people that spring, though I have recently found some of them again.

The major transitions associated with those days did not actually occur on them, as they were far too big to be completed in just a day. Those days were just the turning points at which things could never be the same again. They were the catalysts which forced the transitions to occur, forcing the changes which I could at best attempt to control. Those two days and the transitions associated with them are linked in more ways than I could count, because as different as they seem to be, they are in many ways just the opposite sides of the same thing. Separating everything out into basic components and then putting them all back together again. The story of the canon and the rainbow, of the sun and the flame. A story of discovery and exploration.

And now it is Friday, February 25th again, for the fifth time in my life (although the first time I was only 2 1/2 years old and probably didn't notice). The next time this will happen is in 2022. I'm not expecting any major events today, although my life is full of transitions right now. I remember thinking in the spring of 1994 that the only way I could ever have a better year would be if I graduated, got married, had a child, and got a job I really liked all in one year. Two of those have happened in the past year, one of them was longer ago than that, and the fourth one I am still working on. Where will things go from here? I don't know.

Thank You

I just turned in my PhD thesis. Many people helped me get to this point. Here is the acknowledgements section:

I would like to thank everyone who made this research possible: my committee members - Olivier de Weck, Manuel Martinez-Sanchez, and Ray Sedwick - for providing advice as I navigated the depths of differential geometry; NASA and the MIT School of Engineering (through a TA position for 1.00) for providing funding as I worked through the mess of equations to create a small amount of order in the chaos of Newtonian gravity; my official readers Thomas Lang and Paulo Lozano for feedback as I completed my research; and my unofficial proofreaders Dale Winter, Rachel and Alan Fetters, Sarah Rockwell, and Allen Bryan for helping me to realize where my explanations needed more clarification.

I would like to thank my many friends for making life more enjoyable while I toiled on a seemingly endless task of translating PhD level theoretical math into moderately usable engineering concepts. I would especially like to thank the Boston change ringers for providing a steady rhythm in my life, Tech Squares for reminding me to peel off from my research and shoot the stars every now and then, Metaphysical Plant for reminding me that all hunts for knowledge are eventually completed, and MIT Hillel and TBS for the services and prayers that provided regular cycles in my life to mark the passage of time. I would like to thank my high school cross-country team for training me to have the endurance to keep going forever, my high school math club for encouraging me to study math beyond what I was taught, and the Cows for being good friends.

I would like to thank my parents for everything they have done: providing a good home for me to grow up in, encouraging me to explore the abstract world of ideas, letting me rush off to MIT where I got stuck for years in an endless maze of equations that I may have finally found a path through (suboptimal as it may have been), and most of all for teaching me the value of hard work, honesty, and persistence. I would like to thank my many siblings for living their lives so fully while I was too busy to do so on my own, providing me with many niblings to enjoy, and making the holidays so full of love and excitement. I would like to thank my in-laws for providing some local family and support as Mira and I toiled through the challenges of graduate school. I would like to thank my extended family for being a good and supportive family, and Mira's extended family for welcoming me so quickly and filling our lives with love and happiness. I would also like to thank my son Jesse for making the final months of this work much more exciting than they would have been without him.

And most of all I would like to thank my wife Mira, without whom I would never have made it all the way to the end. She has provided support and encouragement at every step of this process. I have learned how to move the heavens and the earth for her and I would like to remind her that some things really are rocket science. Melanyecce iluvòrënenya oio, mo bhean chéile luinnar silamiradilenya.

Goodbye!

When I was in grade school, we used literature books published by Prentice Hall. They were full of short stories and essays. We typically had to read at most about 1/5 of them, but I normally read all of them anyway. One of the extra readings that I particularly remember is from ninth grade: "Sayonara" by Anne Morrow Lindbergh (an excerpt from her book "North to the Orient"). It is an essay about saying goodbye that looks at what we are really saying when we say goodbye in different ways. Goodbye (short for God be with you) and Adios are blessings and wishes for the protection of those who are leaving (Farewell and Slan are non-religious wishes for things to go well). Auf Wiedersehen, Au Revoir, and such sayings are a statement of hope that the time of separation will be short. But Sayonara means "since it must be so." It isn't a statement of hopes or expectations, it is a simple acceptance of what is happening. It is, according to Mrs. Lindbergh, the most beautiful of all goodbyes. I don't entirely agree with this, as I think it depends on the situation.

As a student for the past 12 years, I have watched many people graduate and leave. Sometimes the blessings seem appropriate (people going off to grad school or a job). Sometimes I really do expect the goodbye to be temporary and using one of those forms is best (summer jobs and short breaks). I can only think of a few examples where I really felt that Sayonara would have been most appropriate (mostly people leaving for medical reasons).

I first recalled this essay when breaking up for the first time. Sayonara had never seemed as appropriate as it did then. After a lengthy period of trouble in our relationship, it was clear that things were over. "Since it must be so" is a good description of how I felt about it. Two and a half months of happiness followed by six weeks of uncertain misery led to me understanding that we wanted different things. Sayonara, an acceptance of reality as it is rather than as we want it to be. And as we broke up, we agreed that we would remain friends, which is the part that mattered most to me.

This summer I again thought of this essay. My time at MIT is drawing to an end, and it is time to move on to the next part of my life. But how can you say goodbye to an institution? I have been at MIT for about two fifths of my life, nearly twice as long as I have been anywhere else. For so many years, MIT has been my home. I have learned all the twists and turns of the hallways, where the bathrooms and water fountains are, and how to quickly get between points even when classes are switching. I have explored the innermost parts of the buildings and found the places of true beauty on campus. MIT has taught me my limits. I have watched the campus grow and change as new buildings were added and old ones were renovated. I have watched the world be completely transformed while I hid in the safety of MIT's academic halls. There are many stories I have made about the things I did and failed to do at MIT.

But now it comes to an end. I don't expect to be back, so some variant of "until later" wouldn't be right. And I don't think that blessing MIT makes any sense. But sayonara isn't right either. There is an edge of sadness in that expression. It suggests a premature parting. I want something more like 2 Timothy 4:7 - "I have fought the good fight, I have finished the race, I have kept the faith." I have done what I came to do, and MIT has little more to offer me. I also have little more to offer to MIT. It is time to go, because I am done. This is not a time for saying "since it must be so." There is no significant difference between reality as it is and reality as I wish it could be. I have been at MIT for long enough; I have done what I came to do. I suppose the appropriate thing to say is "Thank you."

There is another parting in my life right now. Someone I have been friends with for a long time is leaving. We were for a while very close and for a while very distant, but in the past few months our friendship has been pretty much right where I wanted it. And now, almost exactly 6 Martian years from when we first met, she is moving halfway across the country with her family. They have an opportunity which is too good to pass up. And as much as I would like to continue seeing them regularly, I want even more to see them continuing to succeed in life. This is a situation where the proper goodbye really is Farewell, Slan, Good Luck. And so to Erin, Ben, and Blaise, I have this to say:

Slan go foill. Go raibh mile maith agaibh. We will miss you, but we wish you well. Good luck in North Dakota.

How a Thesis is like a Newborn

In the following, I use the term thesis to refer to all the work involved in completing a PhD.

Ways in which a thesis and a newborn are similar:

• both consume all of your time, significantly cutting into your social life and making you lose contact with some friends
• both seriously interfere with getting enough sleep
• both are something you put a lot of effort into in the hope that someday they will produce a meaningful benefit to the world, but you have to accept that most likely they will both go unnoticed by the world at large
• both are capable of making you feel completely incompetent and unable to do anything right for what feels like forever
• both are a good way to meet other people doing the same thing
• friends and family give you advice on both, which is only sometimes useful
• both have a very frustrating way of telling you that something is wrong, but not indicating in any way whatsoever what is wrong
• both are expected to triple in size over the course of a year (different years of course)
• both produce lots of meaningless gibberish

Ways in which a thesis and a newborn are different:

• your thesis is never going to smile at you
• your thesis never seems to be satisfied with what you have done
• your thesis's problems can't be solved in a few minutes
• nobody has claimed that putting your uncovered thesis on your naked chest is good for anything
• your thesis didn't come into the world looking like it came from an alien race, you had to spend years working on it to provide that appearance
• your thesis doesn't smell good
• your thesis doesn't look like you, your partner, or any of your relatives
• your thesis does not become more independent over time
• your thesis will not be damaged by unexpectedly rolling off a table while your back is turned
• you don't have to thesis-proof your house
• you are not genetically programmed to fall in love with your thesis
• people offer to make food for you when you have a newborn
• people do not come over and ask to hold your thesis
• people are actually interested in your newborn (some people, not everybody)
• your thesis isn't your responsibility for 18 years (I sure hope not anyway)
• you can drop out of a PhD program
• neglecting your thesis is not illegal
• you don't have to pay people to watch your thesis when you are unable to
• you get to choose a partner for raising a newborn (most of the time)
• you can't accidentally apply to, be accepted by, and enroll in a PhD program
• there isn't a committee that decides when your newborn is good enough for you to move on with your life
• removing a useless appendix from your thesis does not require major surgery
• random strangers on the subway don't comment on or try to touch your thesis
• when you first bring your thesis home, your pets don't react to it at all
• nobody asks you to track how much waste your thesis produces
• the soft spots in your thesis won't go away on their own
• if you fall asleep with your thesis on your chest, you won't wake up to the feeling of something sucking on your neck
• you don't have to buy any furniture for your thesis
• most people know what a newborn is, but have not heard of sub-Riemannian geometry or astrodynamics
• people never mistakenly think you study stars when you say you have a newborn
• you are allowed to physically damage your thesis when you are mad at it
• your thesis is not at risk of suddenly dieing because you put it down the wrong way
• nobody thinks your thesis is "the cutest thing ever"
• people don't post pictures of their thesis on facebook (or at least not large numbers of pictures)
• you don't normally put your newborn on your resume or expect him/her to be useful for getting a job later
• your thesis never learns to sleep through the night
• when your thesis does something strange and unexpected, you can't call somebody and ask if it is actually normal
• all your ancestors successfully raised at least one child, but most of them did not do academic research
• when you talk about your child, people understand the words you are using
• you can backup your thesis in case you make a mistake later or a hardware problem causes you to lose it
• most parents don't pressure their children to get a PhD
• you can pretend to not have a thesis for a few weeks before it causes a problem