# Whew! by Derrick B. '08

A brief interlude before I go back to studying.

Hi Everyone! It’s been quite a while since I last blogged. MIT can be a harsh mistress. But I’d like to use this post to get back into the swing of things and begin posting regularly again.

When we last left each other, I’d finished the hardest semester of my undergraduate career. I received my first D, but I fulfilled enough graduation requirements for both degrees and got a whole lot of planning experience being the operations officer for NROTC.

IAP ’08 came and went without a post, and that was intentional. I took 10.493: Integrated Chemical Engineering Topics over IAP. After my abysmal performance in ICE back in the fall, I decided to put my all into that module. I did, and I think it paid off. For some reason my grade hasn’t posted to WebSIS yet, but I’m pretty sure it’s an A. I can’t remember the last time I got one of those. Probably back when I was a freshman.

This semester is my last hurrah. While my total number of units dropped, the actual difficulty of the courses increased. Let’s take a look at my registration this semester:

8.04: Quantum Physics I
I finally feel like a physicist. Up until this point, I’ve felt like a kid walking around in his daddy’s shoes pretending to be a grown up. Now I feel like I’m beginning to build a fundamental understanding of the way the universe works. This is a great class, and I’d highly recommend it to anyone with an interest in physics, even if you don’t plan on majoring in course 8. At the very least, it will make you question how the world around you works. In fact, I’m still struggling with some of the results of what I’ve been told. Of late, I’ve been wondering about the following:

Quantum mechanics says you cannot predict, in a deterministic fashion, the location of a particle at a given time. However, you can predict the probability with which a particle will be found over a set of locations. Once you measure a particle’s position, it’s probability distribution turns into a spike (because you’ve found it, the probability that the particle is anywhere else becomes zero. This property is called wavefunction collapse, and to the best of my knowledge its true nature is still a mystery). A small amount of time later, you know that it must be somewhere near where you just found it. However, the same cannot be said for an equally small amount of time before! You can say nothing about the location of the particle before you actually measured it, regardless of where you find it.

Ok, that’s all fine, I guess. In the face of experiment and mathematics I can swallow my disbelief. What I don’t get is this: Quantum Mechanics is a “deeper” theory of reality than classical mechanics, yet in the limit of large quantum numbers (things with everyday size have large quantum numbers), quantum mechanics reproduces classical mechanics (a result called the correspondence principle). However, we know that classical mechanics looks the same regardless of the direction of time. That is, if I know the position and momentum of a classical particle, I know where it is and how fast it’s moving immediately after AND immediately before. How does a theory that says we can’t say anything about where a particle is before we measure it give rise to a very well-understood theory that is invariant under a reversal in time? I’m sure there’s an answer, they just haven’t taught me enough yet.

By the way, the lecturer this term is Marin Soljacic. After being bothered by a beeping cell phone, he decided to invent wireless electricity (I guess we should credit Tesla too). I should decide to invent something.

8.044: Statistical Physics I
Thermodynamics from a physicist’s perspective. Thermo and I are old friends. We met back in sophomore year and have been inseparable since. This will be the third class that explicitly concerns thermodynamics, and the nth class I’ve taken that includes some sort of thermo. I’m enjoying it, if only for the eerie familiarity.

8.593: Biological Physics
My favorite class this term, and my first graduate-level course. Finally, biology the way I’ve been waiting to see it! I once read an article that said “Biologists think that if they try really hard, they can solve any problem with arithmetic.” I’ve found that to be true in the course 7 classes I’ve taken here. Not to denigrate the biologists I know in any way. It’s just that the courses shy away from heavy duty mathematics. I say if you’ve got it, flaunt it. This course gives a rigorous description of selective but representative biological phenomena (vision, protein-protein interactions, etc) using the machinery of calculus and statistical mechanics. The problem sets are longer and harder than any I’ve seen before, but they’re also fewer and certainly worth the effort.

10.491: Integrated Chemical Engineering II
Continuous process design. Right now we’re working on a computer simulation of the production of biodiesel from used vegetable oil. I regret that I don’t enjoy this sort of thing as much as I do physics. But its the last ChemE class I need for my degree, and I’m doing a lot better this term. I’m too close to stop.

21M.051: Fundamentals of Music
A long, long time ago, in another life called “high-school”, I was a musician. I wasn’t great. In fact, I was pretty average. Once I came to MIT, I gave it up. But after going for 4 years without music, and being a senior who’d finished his hass concentration, I decided it was time to go back. Fundamentals of music centers around learning music using the voice as your primary instrument. So we sing all the songs that you learned in elementary school (including “Hot Cross Buns” and that song about the Kookaburra). We also learn how to play the piano. I can’t say I like it more than any of my physics classes, but it is certainly a refreshing interlude.

What else is new? 87 days until I graduate. I have a job. But more on those things later.

### 21 responses to “Whew!”

1. Anonymous says:

first

2. OmarA says:

So it’s not too hard to take five classes?

3. Shruthi says:

Hot cross buns? :D Sounds like fun!

4. Ana says:

You are the kind of person I want to be, and a real fit for MIT. You seem to enjoy more a course where you have ‘heavy duty mathematics’ instead of arithmetics.

5. Anonymous says:

Best way to race through this looong last week!

http://whitehatdesign.com/chat/
Unofficial MIT Admissions Chat Room

6. E. Rosser says:

SWEET! I particuarly liked the WiTricity aricle. Imagine what you could do with that idea– not only PDA’s and cell phones, but imagine medical equipment powered not by bulky cords and battery packs, but by a unit on the patient’s bedside table! Or roving units would not have to dock to recharge, but simply drive back to a WiTricity “hotspot”…
Exciting stuff, and just another reason why MIT ROCKS!

7. Sabreena!! says:

8th!!yay!!

8. Dan says:

Wow it’s so cool to be the first person to post a comment on a blog! I’m so jealous!

It’s hard to believe how much the mentality of a student changes in a year.

9. Anonymous says:

Hot cross buns….I still remember the notes on the recorder: B A G B A G GGGG AAAA B A G

Hot Cross Buns is a classic! I’ve thought of being ChemE, or BioE. I don’t know.

10. Karen says:

YAY! Finally biologists get to whip out the calculus like all those ‘real’ scientists my physics teacher teases me about

Quantum physics blows my mind – but I guess it’s supposed to do that at this juncture in my life. I’m looking forward to hearing more about your classes – please don’t disappear again!

11. yukiko says:

D? AHH..

am I 12th person to post?

12. Ethan says:

I’m certainly no expert, but my understanding is that the uncertainty principle does not affect the correspondence of quantum mechanics with classical mechanics on non-quantum scales for the simple reason that the position of individual particles in a mass is not really relevant in classical mechanics. A mass is a mass and interacts with other masses regardless of how you rearrange the electrons within that mass. When you reverse the arrow of time, you may no longer be able to predict the position of particles within the mass, but there is no reason for that to affect large scale events to any significant degree.

13. Ron says:

How does ROTC work @ MIT? I’ve been really curious about this for a while, but you’ve never posted anything explicit about your naval responsibilities, job, etc..

14. anon says:

15. Duncan says:

I’ve always been interested in a course like 8.04, and now I know that I want to take it.

16. Brett says:

Isn’t the uncertainty principle just important for small things, because it is negligible for big things. That’s what I learned, anyway.

17. Alexander says:

Mainly because we don’t know where the particle is after the measurment either! The only reason we can do it in classical mechanics is because macroscopic objects have a much smaller probability wave associated with them, therefore it becomes almost statistically impossible that the object didn’t come from where you measured it to come from. Now, these objects still have uncertainty in their movements, but few care if your measurements of a kg size ball are off by a femptometer. I’m also not an expert by any means, but I sure do love my quantum physics.

18. Z says:

I don’t understand the issue. QMech is symmetric in time–witness Feynman diagrams. Anti-matter particles are just particles moving backwards in time, and the laws of physics apply to anti-matter the same.

This is probably not satisfactory to you, but I can’t quite get a better handle on the problem…

19. Manou says:

“All science is Physics the rest is STAMP_COLLECTING” Rutherford
enough said