I didn’t know that liquid oxygen is blue until last Friday, when my physics professor brought it to class and let us play with the three-hundred-Celsius-below-zero substance.
A bar magnet (ferromagnetic), liquid oxygen (paramagnetic), andliquid nitrogen (diamagnetic)
I did have a vague recollection of being told before that liquid oxygen is magnetic, but in class, we briefly learned why. Although liquid oxygen has an even number of electrons, molecular orbital theory decrees that two of these electrons abstain from pairing up and canceling out each other’s spins. In other words, liquid oxygen is paramagnetic. Each “spinning” charge looks like a loop of electrical current and produces a magnetic field. In the presence of another magnet, the electrons turn so that their magnetic fields align with the external field.
In a magnetic field, such as that from a bar magnet, the tiny magnets of liquid oxygen’s unpaired electrons align (left). Normally, they point in random directions (right). (Image fromWikimedia)
Now, under the influence of an external magnet, the paramagnetic material has itself a net magnetic field. Further, its North and South poles are aligned with those of the external magnet. Voila, we have magnetic attraction.
The liquid oxygen in the beaker behaves like another bar magnet pointing in the same direction as the real one, and is thus attracted to it.
One thing I really like about my physics professor is that every time he performs demos, he invites everyone to come play with the equipment after class. When we do, it’s practically unsupervised—except for maybe an offhand warning to wear gloves when handling the freezing substances. It makes me feel like an adult and exemplifies either his personal trust for students or trust deriving from Caltech’s Honor Code—or maybe both.
You’re squished with all your dorm essentials in the back of the car and your parents in the front trying to find parking. Emotions are high: Will you make friends? Will classes be too hard? What’s your roommate going to be like?
So you’ve done it! You’re going to attend Caltech, one of your dream schools, and you can officially call yourself a Techer. Maybe you grew up in sunny Southern California or, like me, moved thousands of miles from the East Coast (where they actually have seasons.) Regardless of how familiar you are with Pasadena or the Caltech campus before attending, becoming a student is a unique and new experience. Life at Caltech can be fun, but it is also one of the most rigorous schools in the world. It is important that your own health and wellbeing is always a top priority, regardless of whatever commitments you have on your plate.
Senior year tends to differ widely between different folks. Some have finished nearly all their major requirements, while others will be working through their classes all the way until graduation. My friends and I all fall on different points along this spectrum, but we all have something in common: we’re ready for second and third term.