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Carriacou Diary: Jonathan Hare

Day 17 — Rest Day

Green-turquoise seaKathy, Drew and I take a boat to Trinidad Cays — wonderful place. Green-turquoise sea filling a half mile wide stretch of sand with the odd island dotted here and there. The blue-green lagoon reflects the light so wonderfully that the sea lights up the underparts of the birds that fly over — amazing to see. The boat home from the Cays to Carriacou was great and very, very relaxing — something very mellow about a boat trip slowly making one's way home.

Day 18 — Thermometer

The Ice Men and Woman

Today was 'first day back at school' feeling. By that I mean it started off great and exciting then turned into slight panic by lunchtime, into the blues by afternoon and into an exciting challenge by late afternoon!

Our overall challenge as a group was to try and make ICE! We each had challenges to do to get to this stage. Kathy and I were to make thermometers, and we were happy to help each other on two different types. I chose an electrical device as I thought it might be useful to be able to remotely measure the temperature. Kathy went for a glass liquid version.

Calibrating the glass thermometerMy midday blues were due to the metre that I was trying to make for the thermometer challenge not shaping up the way I had hoped. I think if it was something I was doing at home I would have cracked on with it enough to know what I should be doing but with the camera crews going around and wanting to film various stages of the process, I found it stopped me making the needed development steps.

Also everyone else seemed to be getting straight on with their challenges and I felt a bit worried. During lunch, I had time to think through what I needed to do and so I got stuck into a MK II design for the metre immediately afterwards. This worked really well and so I began to feel much happier about the challenge. Kathy and I made up two coils (1500 turns and 5000 turns) for the metre to try and boost its sensitivity. The metre kicked over wonderfully on the car battery.

I am hoping that tomorrow all of us will have time to brainstorm the ice-making problem.

Overall I feel just the right amount of uncertainty to make the challenge genuinely interesting (scientifically and technically) but not so out-on-a-limb to feel it is uncomfortably impossible.

Day 19 — Thermometer

Today starts early and it's already hot! Up at 5.30, wash, do some meditation and then breakfast. Walk with Kathy to the lime factory. Talk to Kathy about how she feels things are going. We all seem to be full of energy and excited about things. Also talk about calibration points for the thermometers. She suggests using body temperature as well as boiling water etc.

Kathy and Jon test their thermometersSet up the bridge thermometer for its first, and on-film, testing which goes really well. It's so nice when a back-of-the-envelope calculation (done to the nearest order of magnitude in your head) actually works out in real life — in front of your eyes! It gave the sort of kick on the metre it should have done!

The 'in-my-head', 'back-of-the-envelope', type calculation about the metre thermometer: I guessed, or could remember, that the resistance of the copper wire we have used for the thermometer should change by about 20 to 30 per cent between 0° and 100°C. As each resistor is part of the balanced circuit, each will have half of the car battery voltage across it — that's about 6V. So a 20 per cent change in 6V is about 1V. In other words, if only one of the bridge resistors is used as a thermometer, its voltage will change by about this much with respect to the other part of the bridge. I tested the metre I made on a 1.5V battery (from a camera) and it moved about 1cm. When I put the thermometer into hot water the metre moved about 1cm!! That's a really nice feeling.

If we are to make ice in this hot and humid place it occurred to me that we will need a lot of insulation. As a result it might be very difficult to get a standard thermometer into the right place and be able to read it. So I thought that an electronic thermometer would be best as you could have the active circuit fitted near to the ice-making part of the apparatus but also have thin wires to take the signals out to a remote metre where the temperature measurement can actually be done. That was the basis of the electronic thermometer design.

The design consists of four resistors each made from about 40m (44 yards) of very thin (~0.1mm diameter) copper wire. The electrical resistance of wire changes with temperature. It is this change in resistance that causes changes in voltage, which we can measure, and allows us to use the device to measure temperature.

Making the resistors

The coils were wound around a nail for neatness but the coiling was also done in a special way. Firstly, the wire for each resistor is measured out. Then the wire is folded in half so that the two ends are side by side and only then is the wire wound onto the nail. This was done for each resistor. This curious way of winding the coils produces a resistor with no inductance. Inductance is caused by a current flowing in the coil producing a magnetic field but in this case the magnetism is cancelled by the fold in the wire. This greatly speeds up the response of the circuit, when it is turned on and off and when the temperature changes.

The four resistors are wired in what is called a balanced circuit or sometimes a bridge circuit. The balanced circuit consists of two pairs of resistors wired in series (one after the other) across the battery. The meter is wired between the two mid-points of the pairs of resistors.

The thermometer works like this. If each of the four resistors are at the same temperature there will be exactly the same voltage across each. There is therefore no difference in voltage between the two metering points and the meter will not read anything — the circuit is balanced. If, however, we take one of the resistors and place it somewhere at a different temperature, its resistance will change, and so its voltage across it will also change unbalancing the circuit. A voltage difference now exists between the metering points and the meter reads the temperature change.

Back to the diary

The next step was to calibrate the meter. I asked Ellen for some coconut oil to immerse the coil into and this then can be put in boiling water. The oil protects the coil windings from oxidation etc. However, there were problems with the oil and Ellen slaved over the stove for hours to get me some good oil for this test.

Didn't have time to do the final calibration today but we did have time to show that the meter reads one way for cooling and the other for heating (with respect to air temperature) so I marked + and - on the meter to show heating or cooling.

The day ends with the first test run for the ice machine. This was a very exciting time but for some reason we could not cool enough to measure on the meter.

One Funny Moment

Mike L, Mike B and I were being filmed discussing the design of the insulated box for the experiment. Mike B draws the design on the wall while Mike L and I look on and contribute. While this was happening I looked over to Mike L and saw him smiling. At that instant Derek stands on my foot and I can't move and can't get near to the drawing to contribute. I find out later that at the same time I looked over to see Mike smiling, Derek was on his foot too!! So neither of us could move.

Day 20 — Thermometer

The Balanced Circuit

The balanced circuit is the one,
That makes our modern world run,
In TVs, radios and all manner of things,
This circuit even makes the telephones ring,
It's remarkable in this space computer age,
That the balanced circuit is still all the rage!

A Very Funny Moment

Kathy finished her thermometer today and Ellen and I helped to seal it. The filling with alcohol, sealing and setting up of the thermometer could only be filmed once as it was really, really tricky and time was running out. So the director, Sarah, shouted out to the whole factory: "Quiet, please, this can only be done once." All goes quiet and we start to film the sequence. At the crucial moment when all is calm and we are all concentrating on the problem, a donkey walks past the walls of the factory and in a very loud way starts to eeeeeeooooorrrrrr — look out for this one and the strained straight faces in the TV programme.


Kathy and I calibrated our thermometers. Hers was sensitive, mine wider ranging. We both showed two of the many possible ways of making temperature measurements and both got the results we wanted.

Mike L's Doom Comment #9
In the middle of a tense moment of the shoot - "I'll never be able to clean this T-shirt with travel wash" !

A Mike B Funny
Mike B does a rather disturbing but incredibly funny impersonation of a drunk with the rum bottle Kate gave him. The ruffled hair, dirty T-shirt and the great acting was perfect!

I loved it, I enjoyed it, it was true to life, it was believable - it didn't work!! We didn't make ice. We did, however, make a great team effort in a very hot ambient temperature and humidity.

The last hours of the day were brilliant — pure magic. That wonderful mixture of a group focused on a common goal and the wonders of the unknown. Moments like that should be savoured but you tend to be so much a part of it that time goes and you are too soon left with memories to look back on. The programme was amazing in its Science coverage. I hope people understand the difficulty of the challenge and see what was really achieved.

Day 23 — Parabolic Mirror


We circle around this life-giving Sun
Whose centre defies measure of temp. or tun
Simple atoms squeezed into new forms pure
Energy released more and more
It makes its way to surface bright
And on Earth transforms what is day from night
A race and a dance across the void
Of electric and magnetic effect
From distant star we measure their age
And on cold mornings turn our face for warmth
To sunlight made in past times forgot
Turning the wheel of evolution's lot
Clouds, weather, temperate zone
A fly, a snow peak and a bee buzzing moans
Complex shapes and straight white lines
Our colourful illumer from ancient times.

I was to work with Ellen on this programme to try and make distilled water to top up the car battery. I really wanted to make a parabolic solar furnace so we got cracking. I had hoped to make a full size dish but as a first try we made a simpler version which is rather like a cross section of a dish.

Today was hard work. The first day of the filming session is often hard because the crew have to get so much footage to establish the programme. So we spend a lot of time having to set up shots and it feels very slow to move on. Also one is at one's most anxious because you need to get so far to know what to do next and to know how well things are going. Also there was a lot of manual labour needed to get all the holes drilled and all the team: Sandra, Ellen, Steve and I were drilling at the same time! Also, a very hot day indeed.

David got me to do this amazing jammy shot. We need broken mirrors for this challenge and so he asked Derek to set up a camera near to a mirror and positioned so that my reflection can be seen. He then asks me to juggle with three rocks for a bit, talk about how we need some broken mirrors and then hurl one of the rocks into the mirror. The shot was great first time, hit the mirror right in the middle and it shatters into tiny pieces. I made a one in a million perfect shot at the mirror — which disintegrates.

Start to make the mount of the mirror. This is an equatorial mount which, if it is set up correct will allow us to track the sun over the day with just the movement of one control.

Mirror shape takes longer to build than I had thought, partly because there were bans on sawing so that other filming could be done nearby. Ellen makes the supports for the mirror shape, Sandra drills holes in the base, Steve and I carve out the mounting holes in the mount. Mike L shows us how to use a brace and bit which cuts the drilling time down by 100th!

Very dehydrated today, never needed a shower so much. I drank soft drinks and water all night 'til going to bed but still ended up waking up dehydrated in the night!

Day 24 — Parabolic Mirror

Awake to rain! This is as bad as no wind was for the windmill in the first series of Rough Science! But I guess it will pass.

Start the day with a funny scene trying (struggling) to get the mount out of the door of the factory and into its resting place for the solar furnace. Talk about how it works, the pole star etc.

View from inside the lime factoryEllen and I finish cutting the mirror supports down and start to fix them to the base. Fix the thin plywood onto the supports to form the parabolic surface. Ellen and I start to fix a mosaic of mirrors onto the surface with drawing pins. Try out the mirror on flat ground roughly pointing to the sun (midday by then). Not as hot as I would have thought, a little disappointing. Our flat mirrors are focusing the light into pencils of light rather than spots and so I guess it does not feel so hot. Should be OK for heating a largish kettle though. Added the kettle to the focus of the mirror which lights up wonderfully. I don't think it will be hot enough to boil water but it will heat it too hot to hold.

Set up the mirrors on the mount and Ellen starts to cement the mirrors in place. Mount seems to position the mirror OK and just about stands the weight when it is at an odd angle because the Sun's elevation is low. First test runs with a kettle full of seawater producing some condensation on the plastic tube. There is a slight possibility that the water collecting in the collection glass is due to water falling down the spout from above! But the water in the slightly dirty kettle is murky brown while the collected water is clear. Unfortunately, Derek, Ellen and I each take it in turns to accidentally kick over the collected distilled water with our feet!

Ellen and I do a piece to camera where we go through the maths of the parabola and how this formula gives us the numbers to make the basic structure to put the mirrors on. It took a long time to do because we needed to get the chat as brief and as clear as possible. I think this part is very important as maths is the language of so much science. Nice for us to be able to get this across.

Take the mirror off the mount to take indoors to protect it overnight.

Day 25 — Parabolic Mirror

First job today was to put fixing wires into the metal support wire that holds the kettle. This is so that as the mirror tilts when we move it to track the sun, the assembly stays rigid and central. Otherwise the weight of the kettle tends to make it fall around.

Re-assemble the mirror onto the mount so that we can get as much sun time as possible. Today we stop at 3pm because Kathy's light bulb has to be filmed from a boat and we all have to go off and be filmed on location — so we don't have much time. Also the clouds are rolling and so it does not look a great day for solar collecting!

The finished parabolic mirrorBy about 10 am we have set up everything and we leave it in position until the sun gets a little higher in the sky (otherwise the mirror is at a silly angle - too low). The sun is already too hot for me. I've really struggled with the heat and the sunlight these last five days or so. Even by 10am I am feeling strange — we really need some shade. Ellen and I make up a simple palm shade. She said she was surprised at the way I was doing it as she would have done it completely differently! I guess we both use what is to hand but in our own way — that makes sense.

We make up a sunshade out of three palms and a wooden support, carry it out to the solar furnace and Ellen fixes it up with rocks to support it. However, the TV crew wanted to film us doing it and so we took it down and they filmed us walking along and trying to put it back up. I say trying to put it back because we could never get the rock to fix it up again and every time we put it up and sat beneath it, it fell down on us — much to the amusement of David, Derek and John!

By 11ish we had collected no visible amount of water so I tried playing around with painting the bottom of the kettle with black paint. I was also worrying about the seal on the kettle lid not being tight and losing a lot of steam. When you opened up the kettle you could see condensation on the lid but very little coming down the plastic tube. So I played around with replacing the kettle with a glass flask and bung with some seawater inside and collecting from this. However the weather was on the turn and I think our sunshine was over for the best part of the remainder of the day.

The rain pours and pours so I collect rain water!! I collect over half a litre by having loads of jam jars and lids collecting the drops, even from the guttering!

I put back the kettle because I realised there would not be time to test the other device out and also because it would have been too much filming to include the new developments with no obvious benefit in the time available. Also, it would have been fun to try and make a full mirror either by fixing two such mirrors to form a cross, or better still by making a real 3D surface based on the same formula. This would have been quite big but if we had time I know that this would have worked really well. But there you are — the real Rough Science Challenge is the TIME challenge.

Kate, Ellen and I do the handing over of the distilled water. I filled the glass jar with a guess at what we had made from yesterday (we spilt it three times!!) but also we talked about how you could use the rain water a few times for the battery and the salts and chemicals picked up as it fell from the clouds would only be a problem after repeated usage. Also, it's OK in this rainy season but the solar furnace would have come into its own in the dry season when there is no rain for months.

At about 3pm we go to the dive centre in the town and after an hour waiting for the sun to go down a little (we needed to film the sunset or dusk and so there was no point being out on a boat and waiting around in the midday heat) and to have the necessary safety talks. We finally head out on the boats to Sandy Island which is a coral reef that formed a sand bank and island after one tropical storm a few years ago. There are even trees growing on it now. We stop the boat in about 4 or 5 feet of water above some coral. This is Kathy and Mike's big challenge to drop the light overboard and use it to light up a part of the coral. The bulb has to last long enough and also must remain airtight as water entering the bulb would have ruined it.

We filmed the exciting sequence three times because after each time the light was a little more amazing and so the editors could choose the best. It was so good to be out in the boat and exciting too. The view back as we went back to shore was wonderful, the setting sun lighting up Sandy Island in silhouette and the whole thing framed by incredible bubbly red clouds above the sharp horizon of the Caribbean sea. A really great memory to have! I would really love to paint that scene.