Archive | December 2012

Alien Life Lesson

A couple of weeks back I was asked to help plan a lesson on alien life to a GCSE class. In our 20 minute brainstorm we came up with what’s below and I suitably pleased with house the lesson went that I’d share our quick thoughts on this.

Alien life and SETI (Search for Extraterrestrial Intelligence) is part of GCSE science, in particular it is a physics topic. For this we decided that it would be quite interesting to add a bit extra to make the subject a bit deeper.


For a starter we got the students to look at the Drake Equation, yes I know this isn’t the most scientific and indeed some of the numbers are hard for the class to comprehend (doing this as group work would lead to differentiation giving a variety of information or different parameters for the more able to answer). The Drake equation is good fun as it exposes the students to a wide range of different numbers and the large scale of astronomy. It also has some interesting social issues in there. The idea that society could transmit, or retrieve, a signal for thousands of years is very thought provoking especially when you bring in the idea of 60 years or so for our society. So, you might be think, what is the Drake Equation? Simply the Drake Equation allows one to estimate the number of detectable civilizations in our galaxy. This was put together in 1961 by radio astronomer Frank Drake.

The Drake equation states that:

N = R x fp x ne x fl x fi x fc x L


N = the number of civilizations in our galaxy that can be communicated with
R* = average rate of star formation per year in our galaxy
fp = fraction of those stars that have planets
ne = average number of planets that can potentially support life per star
fl = fraction that develop life at some point
fi = fraction that develop intelligent life
fc = fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = length of time for which such civilizations release detectable signals into space

Drake used the following:

R* = 1/year
fp = 0.2-0.5 (
ne = 1-5
fl = 1 (100% will develop life)
fi = 1 (100% will develop intelligent life)
fc = 0.1-0.2
L = 1000-100,000,000 years

They roughly concluded that N ~ L and somewhere between 1000 and 100,000,000 civilizations in the galaxy.

Using more recent, and less optimistic numbers gives much lower values, very sceptical values give very small values of N: 10^-20. So we would probably be alone in the whole Universe. A good discussion of these parameters is given over on wikipedia (maybe a chance for some research work?).

After this we went on to get the class to discuss how we would communicate and how we could detect alien life, what we are looking for, how we are doing this and why should we do this. This was done in groups with ideas discussed as a whole group. The students then went on to think how we could terraform Mars, in essence answering the question: what do we need for life?

We finished off by getting the students to calculate how far out into space the first radio signals that man sent into space will have now gotten? This is a nice link into history and the Berlin Olympic game of 1936 and the first TV signal sent into space. The students were asked, after being reminded what the speed of light is in SI units, how far the radio signal would have gone. This is of course the current year – 1936 light years. It was interesting to see how close the students got to the correct answer in metres. This could have been extended if they had been time via a list of nearby stars and to calculate how many stars are in that region.

I feel this lesson was a bit different to their normal work and they got to touch on many different aspects of physics and the world around them.

Have you Pynterferometer’d yet?

So you want to have a play with a radio telescope? Why not do it at home using a virtual array of telescopes. A while back I mentioned Pynterferometer and now we are pleased to be able to say that there is now a version for most operating systems. If you run Linux, Mac or Windows you can now use our tool. Pynterferometer is a graphical interface designed to demonstrated the techniques of radio interferometry used by telescopes like, ALMA, e-Merlin, the JVLA and SKA, in a manner accessible to the general public. For further information take a look at the tool’s webpage:


Oh and if you want to read all about the background to the tool and have an introduction to radio intereferometry take a look at our paper.

My 2012 in 12 images

Its about that time of year where I do my annual summary of what I have done… I normally go on endlessly writing random stuff. This year I thought I’d do something a little different (and hopefully a little faster for me to put together)… my year in 12 images of things I’ve done and places I’ve been:

1. The wonderful caves of Ellora, India (this is cave number 10)

Ellora cave 10

2. The serene and might Giant Metrewave Radio Telescope (GMRT) at sunset

GMRT Antenna at Dusk

3. Amsterdam Central Station

Amsterdam Central Train Station

4. Saracens vs the Harlequins and my first time at the new Wembley

Woop Wembley

5. Kings College, Cambridge


6. The Royal Society Summer Science Exhibition and ALMA

some of the ALMA SSE team

7. Black Sabbath @ Download 2012

Black Sabbath @ Download 2012

8. Wicken Fens windpump

Wicken Fen Windpump

9. The 4C at the MRAO during one of my many public tours


10. Garden gate a Wimpole

Wimpole Garden Gate

11. St. Andrews Square in Glasgow

St Andrews in the Square

12. The baby’s room

Baby's room

Stone Age boardgame

We recently got our hands on Stone Age – this was a birthday present for me off my wife (yes my birthday is not till January but with a baby on the way we thought best get it now so we can learn and actually enjoy it).

I have to say I really enjoyed playing it… not just because I have now won twice but because its a bit different to our other games. There is a nice constant competition going on throughout but then there is the anticipation as you add your scores up at the end, a lead that happens in the game can quickly be destroyed at the end.

Stone Age

The concept is quite simple, gather resources and build things but there is the randomness introduced by the dice role – so do you go for broke and put all your little people in one area or take a chance and role for a win! With the collection of food and increasing population it feels like Agricola. This game has won many different rewards and I can understand why… its so much fun and I reckon it will be played many times in my house. I’m now looking forward to playing it as 4 players as the rules change!


How light affects photosynthesis

The other week we did a nice and fairly straightforward experiment to look at the factors affecting photosynthesis. For this we used some pondweed, water, baking powder and a light. Sounds rather straight forward doesn’t it? It mostly is apart from it not being entirely reliable. I found this quite a nice experiment to run with my GCSE group as it allowed them to get a hands on feeling for this. We only spent 30 minutes on this and this should have been longer. Around 2 out of 8 groups got reliable data. We followed this up with homework to repeat the experiment using an online tool.

Here is what you need and and do..

Large beaker, funnel, graduate test tube, light source (lamp), metre ruler, stopwatch, paperclip, sodium hydrogencarbonate solution (5g/l), sharp scissors, Elodea sample.

Elodea experiment


  1. Place your pondweed (Elodea) in a large beaker of water containing a pinch of sodium hydrogen carbonate (ensures a good supply of carbon dioxide in the water).

  2. Attach a paperclip to the uncut end of the pondweed. Makes the stem float upwards but keeps the plant at the bottom.

  3. Cut the end of the pondweed while it is under water

  4. Place the funnel over the weed to cover it completely. The end of the funnel should be under the water – see diagram.

  5. Using the metre ruler – position the light 10cm away from the plant and leave for 5 minutes to adjust to surroundings.

  6. Whilst waiting: Write a prediction. How will the rate of bubbles change as you move the light away?

  7. Whilst waiting: Create a table of results – Distance away (cm), Number of bubbles

  8. Count the number of bubbles given off by the stem in one minute and record your answer.

  9. Now move to 20cm, 30cm, 40cm. Record your result in a table. Make sure you give the plant 5 minutes at each new light intensity before you start to measure.


Questions (answer in book):

What do you notice?

Does this accurately represent the rate of photosynthesis?

What factor may also play a part as the lamp is moved closer to the plant? How would this affect your results? How could you overcome this?

Ankh-Morpork boardgame

I’ve decided, given I now spend quite a bit of time (and since we have a decent group getting together often) playing board games to try and write a bit about some here… so here is my first attempt..

Ankh Morpork

Ankh-Morpork is set in the largest city-state in Terry Pratchett’s Discworld. The concept basically is that Lord Vetinari has disappeared and the different factions are trying to take control. The thing that makes it so much fun is you don’t know how everyone else is trying to win. There are lots of different characters and there are many different victory conditions – for example Command Vimes wants you to get all the way through the deck of cards then that player wins. You don’t need to know any thing about Discworld, but I’m told it helps with the jokes on the cards etc.

We have played this many time as a 4 player game and quite a few times just 2 players. It works best with 4 but works pretty well with just the two of you too.  Its a pretty simple game to get your head around – you play a card and do what it says, of course with your goal in mind. I’ve been given the game on a plate by Joe at least once. Not that I’m minding. I’m sure many of the other games I could write about will have that statement.

This game is also nice cause it doesn’t go on and on, requiring at most an hour or so and at times less than 20 minutes – depends how things go etc, definitely has lots of replay-ability too, so you’ll get your money’s worth.

Exploring Exoplanets with Year 7

At school this week I ran Science Club (a 20 minute lunch time session) on “How to find alien worlds…. “. For this we explored the developments within the hunt for extrasolar planets. We started off by recapping the number of planets in our own star system and then looked at the number of planets currently know – quite a few, as I write this  853, (latest numbers can be found on This was the hook and it seemingly worked well.

To further explore this I then got a volunteer to hold a pretty bright torch and pretend to be a star. Another student was a planet who could move in front of the star. The rest were observers with telescopes on the Earth. A discussion of what they could see was led culminating in the conclusion of how this was similar to an eclipse.

We then went about looking at a graph of the light curve from HD209458 – the first discovered transiting extrasolar planet. This is a stripped down version of my 2011 “Extrasolar planets in the classroom paper”  . Firstly I explained how the graph could represent what we just did with the torch and then we went on to make some measurements.


All you have todo now is measure the time from the start to the end of the transit (i.e. were the light has dipped from the higher to the lower level) and you can determine the planetary radius!

Now I was doing this in 20 minutes with Year 7 so the next bit we kind of glossed over the Newtonian physics and the orbits – if I had longer and doing this with an older group I would have spent time here.  So to make this short (full details in the George 2011 paper):

Planetary radius = Transit Time x pi  x a / P


a = the separation between the star and the planet = 0.047 AU = 7031099.937 km

P =  time taken to orbit the star for the planet = 3.52 days = 304128 seconds

pi = 3.14159….

Its useful to compare to the radius of Jupiter: 69 911 km

And there you go planetary radius, should be something like 1.27 x the radius of Jupiter.

Not bad for about 20 minutes. The students quite enjoyed this and it worked really quite well allowing me to show off an area of science I’m truly passionate about.

(If you would like to try this with your class then it might be handy to have my excel workbook.)