Saturday, March 21, 2009

Happy New Years!

In response to my midwinter refusal to resolve to anything until the spring equinox, my brother noted the following:

Did you know that the Persians celebrate new year at the spring equinox? They call it Nau Ruz and is a huge celebration in Afghanistan/Iran and Tajikistan as well as being celebrated in other places in Central Asia.

Also, the Nepali new year, Dassain, is celebrated at the Autumn equinox.

This of course, quite apart from Chinese New Year which he celebrated in China later in the month. So it seems that if I mix up several unconnected traditions, new year resolutions at the equinox makes a whole lot of sense.

Of course this still leaves me needing some resolutions to make. I think I've got 5, which neatly split into the usual categories: Work, Friends, Exercise/Health, Bad Sci-Fi and Other

1. Work. I'm tutoring maths. I'd like to resolve to get those kids on the borderline the C that would make such a difference, but at the end of the day that's not up to me. I will resolve to maintain my current level of professionalism; namely that even though I only get paid for the hours I'm working, I'll still prepare and mark, discuss with their regular teachers and make myself available to the students, whether it's part of the scheduled hours or not[1].

Also, I resolve to continue to show as much patience as the kids need. Right up to the moment when it becomes counter productive; then I'll rant, rave and use every sanction in the book.

2. Friends. Looking at emails and facebook and christmas cards, there are far too many people I've not seen for ages. Fortunately I'm not working during Easter or the Summer Holiday when the school is closed. My resolution is to have very cheap holidays visiting friends. We all win! I win more of course, as I don't have to pay so much for accommodation. But still.

3. Exercise/Health. Time to take some exercise in the sunshine so I don't look like a giant pale slug while visiting during the summer. On the other hand, no need to go overboard. The resolution: Walk (or run or cycle) down to the bay twice a week.

4. Bad Sci-Fi. More movie nights and more reviews at Heckler and Kochk. Shall I aim for reviewing at least one item per week? I think so. It is so resolved.

5. Other. You know what? I've forgotten what this one was going to be. So my final resolution will be to be more organised. Yes, yes, you've all heard it before. But I'm going to use that notebook sitting by the keyboard properly so that things get done in a timely way.

Well, there we go. They're all testable, although some are a bit vague. In other words, I can go back and take a look at how I've done, come Nepalese new year. Assuming I'm organised enough to do so, see you at Daissan!

[1] This doesn't mean I won't complain and/or ask for overtime if they start to insist on me attending outside my contracted hours, but I'll still do the damn job like a professional.

Thursday, March 19, 2009

Conversation of the day

Pupil A: Sir, Sir, do you know you have a secret admirer?
Me: You're not doing very good job of keeping it secret. [Walks away, smirking]
Pupil A: Eh?
Pupil B: He thinks you're the secret admirer.
Pupil A: What? Me? No! It's not me sir! Oh no!

Monday, March 09, 2009

Conversation of the Day (reported)

Pupil: So Miss, where's this dude who's supposed to be observing this lesson?
Miss B_: It's Miss G_, the Head of School, and she's sitting over there.
Miss G_ [Brightly]: Hello, I'm Miss G_, Head of School, and I'm going to be observing this lesson.
Pupil: Um.

Sadly I wasn't there to see this, but it is highly plausible.

Sunday, March 08, 2009


Dave sent me a link to this cartoon about the loneliness of being a photon. After wiping the tears from my eyes, I was consumed with rage. Why? The science is wrong!

In the cartoon, 10,000 years pass for the photon, who lives each and every second of it. But this simply won't wash. It's the 21st century now. If you're going to create a cartoon with a photon as the protagonist, you have to have a basic grasp of relativistic time dilation. It's special relativity too, rather than general relativity so really there's no excuse. I will demonstrate using the formula for time dilation between events for a moving observer compared to an inertial observer:

t' = t*√(1-v2/c2)

t' is the time interval for the observer in the moving frame
t is the time interval for the observer in the inertial frame
v is the velocity of the moving frame (in terms of c)
c is the speed of light

As we can see... hello? Is anyone still here? Do you want to come down to the front now all the people scared by equations have left[1]? There. Now I don't have to shout and you can see better.

As I was saying, if you start plugging in values you'll see that if you're travelling at 80% of the speed of light, c=1.0, v=0.8, so t' = 0.6t. Or in other words, if you're travelling at 80% of the speed of light (0.8c), you only experience 60% of the time that observers at rest[2] will record. The faster you go, the greater the difference, and the smaller the time appears to be. At 90% of the speed of light (0.9c), t' =0.33t or time moves at one third that of the outside universe. At 0.99c, t'=0.14t or one seventh to those observing the traveller from a rest frame.

But what happens when v=c? Plug in the numbers and v2/c2=1. So (1-v2/c2)=1-1=0. Square root that and we get t'=0t, which tells us that no time passes while you travel at the speed of light.

In practice, any particle with mass, will have had it's mass increased to infinity (requiring infinite energy) to get to that speed. But photons are massless, and, (almost) by definition travel at the speed of light. So no time passes for them between when they are emitted and when they are absorbed[3].

Or in other words, I'm afraid the cartoon of Sam the photon is fatally flawed for me.

On a lighter note, I wrote this in 2003:
The adventure of Jim and Stan riding a photon in three scenes

Scene 1
Outside Stan's Physics theme park Photon ride - "Ride a quantum mechanical particle at the speed of light! Guaranteed to reach a destination before the universe closes"
Jim "This should be good"

Scene 2
Just about to take the Photon Ride
Jim "Yeee..."

Scene 3
Just after taking the Photon ride
Jim "Can I have another go Stan - I didn't really have time to appreciate it. Oh go. Please. Side effects? Well, for a moment I thought I'd put on some weight..."

[1] Fairly simple derivations of this equation are available on the internet. Ask in comments, or simply google time dilation equation.
[2] In general we'd be thinking of observers at the start or end of the journey, but any in a common rest frame will do.
[3] In a closed universe, all photons will eventually be absorbed. In other universes, they might not. But don't feel sorry for the photons that miss everything ever; they exist in an eternal now, without duration. They'll keep travelling on, following their path to timelike infinity, as fresh and young as the moment they were emitted.

Friday, March 06, 2009

Conversation of the Day

THEM: Sir, do you know an easy way of making money?
ME: If I did, why would I be working here?

Another week gone, and some kids understand a bit more maths than they did on Monday. Let's see if they remember any of it after the weekend.

Also, next Thursday is a focus day. I'm slightly concerned that my notes say "Morning, Year 10, Disaster Relief".

Tuesday, March 03, 2009

More News From The 21st Century

Over on a discussion of recent technological innovations on Charlie Stross' blog, Alex notes
Manly-Warringah Rugby League club, since last night the world champs, have added a GPS data logger to their players' equipment, so their stats guy can analyse precisely where they move on the park and how fast. They're networked, too, so statto gets real-time data. Aussie RL clubs tend to be very innovative with stats, they were doing complex spatial things when British RL was doing tackle counts at most and football thought ProZone was science fiction.

This also means it's possible to simultaneously blog and play rugby league.

Which has stalled my brain[1]. Clearly to kickstart I should just glance through the papers for some science news that isn't weird:
How the smell of rotten eggs makes men randy

Scientists take eight transsexuals and a whiff of hydrogen sulphide to begin making an alternative to Viagra

It makes yesterday (when I was measured by a team of Year 9s and have had my height and forearm length[2] immortalised in 15 scattergraphs) seem positively normal.

[1] Actually it hasn't, but you don't want to hear about my ideas for a Rugby League twitter feed
[2] 196cm and 34 cm respectively