Science by Email | Light's whispers, thermometer

Having trouble reading this? Try the web version Manage your subscription Forward to a friend     13 JUNE 2014           News: Light's whispers         A whispering gallery of light has made the world’s most sensitive thermometer yet.   This thermometer sets a new record in precision. Made by an Australian team of researchers, it is three times better than the previous record holder, and can measure temperature differences of just 30 billionths of a degree. This is the smallest change which can currently be measured.   Although the thermometer is very precise, it is not accurate – it measures changes in temperature, not an absolute temperature. It can’t tell you that it is 20 degrees Celsius today, but it can tell you that a chemical reaction has produced energy! Scientists use these measurements to investigate how medicines react with chemicals in the body.   The thermometer works like a whispering gallery. Maybe you’ve played with one before. A whispering gallery is a curved wall, and when you whisper to one end the sound carries all the way across to the other. There’s a great example at the Barossa Reservoir in South Australia.   Instead of sound and a wall, the thermometer uses light and a crystal. Lasers fire red and green light into a crystal shaped like a Frisbee. The light circles ‘round and ‘round the disc, like sound in a whispering gallery.   Heat makes the crystal expand. That changes the speed of the red and green light. If the lights were sounds, the two tones would be slightly out of tune with each other. Because they are lights, the change in speed as they circle means a change in colour, which can be measured.   “We have built a very precise thermometer, and our technique could be used to measure other things,” explains Andre Luiten from the University of Adelaide. “Force, pressure or small quantities of molecules could be detected ... We can use the power of light to do many useful things.”   The whispering gallery technique can detect a single virus in a drop of water. To do this, a round crystal is coated with chemicals that stick to a certain kind of virus. When a virus gets stuck, it changes the size of the crystal. Just like with the thermometer, this affects light in a way that can be measured.   One issue with the virus sensors is that they are sensitive to temperature. The thermometer team used this issue to their advantage – being sensitive to temperature is just what you want in a thermometer!   More information The world’s most accurate thermometer. South Australia’s whispering wall. A biosensor that can ID virus particles.                 The thermometer uses light to measure temperature differences to 30 billionths of a degree. Image: James Anstie/IPAS/School of Chemistry and Physics/University of Adelaide.                   Quiz questions         Where would you find the longest bone in the human body? Are electromagnets activated by a) electricity, b) magnetism or c) gravity? How long does a night on the Moon last? True or false: pterosaur means ‘winged lizard’? There are two letters that don’t appear in the periodic table – what are they?           Try this: Make a thermometer         Add food colouring to water in a glass bottle.   Add a straw to the bottle and seal with modelling clay.    Heat the bottle and watch the water rise. Mark the water level with a pen. Next, try cooling the bottle. What happens?              You will need Glass bottle Cold water Hot water Ice Food colouring Modelling clay See-through straw Large container Oven mitt What to do Fill the glass bottle almost to the top with cold water. Add some food colouring to the water so you can see it better. Add a straw to the bottle and hold it in place with the modelling clay. The straw should stick up through the middle of the bottle's mouth. Make sure the clay seals the bottle tightly around the straw. You can check by blowing gently in the straw. If it is sealed, water should rise through the straw. Fill the large container with hot water. Keeping the glass bottle upright, put it into the hot water in the large container. What happens? Wearing your oven mitt, carefully remove the glass bottle and pour the hot water from the large container down the sink. Put the ice into the large container, and put the glass bottle in the ice. What happens now?   What’s happening? When the glass bottle is placed in hot water, the coloured water inside the bottle rises up the straw. The water molecules in the bottle heat up, which makes them bounce around faster and faster. Because bouncing molecules take up more room than slow-moving molecules, the volume of water in the bottle increases. The clay stops any water or air getting in or out of the bottle, so the water has nowhere to go but up the straw.   Once the bottle is added to ice, the water molecules cool down. They don’t have as much energy to bounce around, so they take up less space and the water goes back down the straw.   This activity works best if there’s a big difference between the temperature of the water in the bottle and the temperature of the water in the container.   Applications There are many different types of thermometer and you can find them all over your house. You might use one when you are feeling sick, to check if you have a fever. Around your home, all sorts of machines keep track of temperature, including air-conditioners, ovens and fridges. Many computers respond to temperature and prevent overheating by turning up the fans inside the case.   This activity appeared on SCOPE. SCOPE turns the ordinary into the EXTRAORDINARY every Thursday and Friday at 8 am on Channel 11. SCOPE is produced by Network Ten with the cooperation of CSIRO. For more information, check out the SCOPE website.   More information Different types of thermometer. Try another temperature activity – cozy in cotton or warm in wool?                 Websites         Read it! CSIRO chief Megan Clark received a Companion in the Order of Australia on Monday for her service to scientific research.   See it! Light as you’ve never seen it before. Three image galleries from the Optical Society.               Watch it! Sunlight floods solar fields in Newcastle to create supercritical steam.                   Quiz answers         The longest bone in the human body is the femur, in the thigh. Electromagnets are activated by electricity. A night on the Moon lasts about two weeks. True. Pterosaur means ‘winged lizard’. J and Q do not appear on the periodic table.               Our partner         Lloyd’s Register Foundation (LRF) is a proud partner of Science by Email. LRF helps to protect life and property by supporting engineering-related education, public engagement and the application of research.           Written by Sarah Kellett  • Edited by David Shaw • Email sciencemail@csiro.au   Manage your subscription · Unsubscribe