The Coriolis Effect and Christmas Questions for Dr Chris Smith

18 December 2005


This week we put our heads in a spin as listeners across the world test whether it is possible to detect the Coriolis Effect from your bath tub, Karl Kruszelnicki provides the answer to the Coriolis quandry from a bathroom Down Under, Kat Arney interviews Jack Ashby about how insects can catch criminals, and Drs Chris, Dave and Phil answer all your questions on science, technology and medicine.

In this episode

Rusted Car

- Dent your Pride But Not your Car

Nissan unveil self-healing paint...

Dent your Pride But Not your Car

Japanse car giant Nissan are set to launch the perfect product for careless drivers, a paint that automatically repairs minor scrapes and scratches...

The paint contains a highly elastic resin that forms a protective coat over the paint. If the paintwork is dented, but no paint is removed, heat from the sun melts the resin which flows back into shape, returning the surface to its original smoothness. The new paint will be unveiled on an SUV soon, and will add about AU$600 to the price tag.

Unfortunately it can't sweep up broken glass, so women drivers are still encouraged to keep a dustpan and brush handy in the boot in case of minor road skirmishes...

The red planet

- Booze-cruise

Mars could once have been a booze-Mecca for methanol lovers...


Mars could once have been a booze-Mecca for methanol lovers, according to recent research from China's University of Science and Technology.

Most scientists believe that, millennia ago, Mars was wet world where oceans, lakes, rivers and streams sculpted the surface as they do here on Earth today. But the Chinese research suggests that grey deposits of iron oxide found on the surface could also have formed in ancient seas filled with methanol, an alcohol, rather than water.

Further analysis of samples from the Martian surface will be required to determine whether the theory hold water or not. But for those fond of a tipple, a trip to Mars remains a bad choice for a booze-cruise under any circumstances because, once inside the body, methanol is converted to formalin (formaldehyde), a highly toxic chemical that is sometimes used to embalm dead bodies!

- Insects Bring Cannabis Traffickers Out of The Wood Work

The Naked Scientists spoke to Kat Arney interviews Jack Ashby at the Grant Museum, London

Insects Bring Cannabis Traffickers Out of The Wood Work
with Kat Arney interviews Jack Ashby at the Grant Museum, London

Jack - This is a collection of insects that were found on a massive haul of cannabis captured in New Zealand. Some people were arrested and they said it was for personal consumption even though there were 188 kilograms of cannabis found. They said that they'd grown it themselves, which also got them round a few laws. What the forensic scientists did was went through the cannabis and found lots of insects in there. There were nine different insect species in total, and by identifying them, and working out where they live in the world, they could overlap the ranges and find out exactly where the cannabis was grown.

Kat - So what insects have we got here?

Jack - We've got lots of types of beetles, including rove beetles and darkling beetles. We also have some rice weevils and ground beetles.

Kat - So when they looked at where all these animals lived, what was their conclusion?

Jack - They found that all the insects lived in a very small area of Burma in South East Asia, which meant that the people had actually imported all the cannabis. So they were actually trafficking as well as being in possession of huge amounts of cannabis.

Kat - So not all for their personal use then.

Jack - No, not all.

Kat - Do insects eat cannabis?

Jack - Yes, a lot of animals eat plants, and cannabis is among them. I'm not sure if they get influenced by it though! I wouldn't know what a stoned beetle looks like!

- Can You Detect The Coriolis Effect in your Sink?

The Naked Scientists spoke to Dr Karl Kruszelnicki, University of Sydney, Australia

Can You Detect The Coriolis Effect in your Sink?
with Dr Karl Kruszelnicki, University of Sydney, Australia

Chris - What we've been doing this evening is asking people all around the East of England to fill sinks and baths with water, pull out the plug and see which way the water swirls down the plug hole. We've got a mixture of results this evening, but is this experiment actually possible? Can we detect the spinning of the Earth using this approach?

Karl - You can get it to work. However, you're looking at a thing called the Coriolis force, which is actually angular momentum under a different name. The Coriolis force on the small bodies of water you're working on is roughly 10 million times smaller than the gravity force, so you really need to do the experiments delicately. Let's just back up a bit here. The thing about angular momentum is the same as when ice skaters go faster when they pull their hands into their body. They speed up because they bring more of their mass to the spin axis of the body. If you think about the Earth spinning, at the equator it's a long way from the spin axis, and at the poles it's right on the spin axis. If you get a storm brewing just above the equator, they spin and move away from the equator towards the poles. As they do so, they head towards the spin axis of the Earth. There's a bit of angular momentum that needs to be accounted for. If you do the equations, this leads to clockwise rotation of a hurricane in the southern hemisphere and anticlockwise rotation in the northern hemisphere. But here you're looking at something tens or hundreds of kilometres across. How can you hope to see that same effect in a tiny tub? The answer is that if you do the experiment very carefully, you should be able to see it. This has been done once or twice.

Chris - So it is possible?

Karl - Yes. In a fine journal called Nature in 1962, there was a paper by Shapiro who did the experiment at MIT. A few years later at the University of Sydney, also published in Nature, a paper by Trefethen in 1964 about the bath tub vortex in the Southern hemisphere. What you do is get a special bath tub, which is two yards across, six inches deep and has a tiny tiny central hole. You put a cork there so you can see which way the water's going. You let the water settle for a day or two so you lose all the residual spin from putting it in there and then you open the drain plug. The water begins to flow out very slowly and nothing very significant happens for about twelve to fifteen minutes. At around that stage, you can begin to see the cork take on a clockwise or anticlockwise rotation depending on your hemisphere. It happens slowly at first and then increases to one rotation every four seconds by the end. Shapiro wrote that when all the precautions prescribed were taken, the vortex was invariably in the anti clockwise direction. Soif you're a fair way away from the equator and you it carefully, you can see it. However if you just rush off the plane at Singapore which is one degree from the equator, and the surface of the Earth is about parallel to the spin axis, put some water in an oval bowl and pull the plug straight out, you're only going to see local effects.

Chris - So in other words, Michael Palin was fooled into thinking this was true at the equator.

Karl - Mate, there's an old Polish saying. If you've got a dog, don't bark. It's fairly obscure, but what it means is stick to your speciality. The number of areas of ignorance we have are huge. In this particular case in the TV series Pole to Pole, Michael Plain meets a man called Michael McCleary, who says that this line here on the ground is the equator. He has a little square tub which he's holding in his hands with floating matchsticks. He then walks off in one direction and spins as he turns around to face the tourists. That gives a spin to the water. He takes his finger off the bottom and you can see the matchsticks going round clockwise or anti clockwise as he's being told. Poor Mr Palin is being conned!

Chris - It just goes to show that even the great Michael Palin can be conned sometimes. Thanks very much for joining us Dr Karl and helping us to avoid throwing out the baby with the bath water and debunking the myth of the Coriolis effect and how it effects spin when water goes down the plug hole.

- When will there be radar controlled brakes on cars?

When will there be radar controlled brakes on cars?

When will there be radar controlled brakes on cars?

There are a number of different things that are coming on line now for cars. Volvo have got a system that literally shakes you awake if you show signs of driver fatigue. In other words, the car is sensitive to characteristic changes in driving habit that people show when they're nodding off at the wheel. Mercedes have got something called a crawl function. When you're in a traffic jam, it's really annoying having to keep braking and changing gear. What they've developed is a car that uses radar to detect the car in front and see how far it is away. When the car in front nudges forward, your car edges forward too. It makes driving in heavy traffic much more enjoyable. Research in air pilots has shown that if everything is automated for the pilots, their brains almost go to sleep. This makes them react badly in an emergency. If they're having to think all the time to control the plane, then if something bad happens they're already aware of what's going on.

What is COPD?

COPD is Chronic Obstructive Pulmonary Disease. This is the inflammation and accumulation of excess mucus within the airways, which makes them narrow and difficult to breathe. Once you have it, it tends to keep coming back, and it gets worse as time goes on. That's the proper text book definition, but it actually exists in a spectrum. Some people have very mild COPD, while some people have very sever COPD. It's generally associated with smoking.

- When you sneeze, why do you sometimes get a horrible smell?

When you sneeze, why do you sometimes get a horrible smell?

When you sneeze, why do you sometimes get a horrible smell?

I have no idea! One possibility is that when you sneeze, you take a lot of air and push it out quickly. It's like your body trying to scratch the inside of your nose. The air hopefully dislodges whatever's aggravating your nose. This may bring up some mucus and put it near the respiratory epithelium, which may be what you're smelling.

Hubble Telescope image of distant stars showing diffraction artefacts.

- Was the Star of Bethlehem a real astronomical event?

Was the Star of Bethlehem a real astronomical event?

Was the Star of Bethlehem a real astronomical event?

There have been quite a lot of people who've looked into this sort of thing to see whether it was actually a real event. In fact, my lecturers when I was back at university wrote a paper on that exact same thing. He looked at the theory that if you get Jupiter, Saturn, Mars and as many planets as possible in the same spot in the sky, can you get a star bright enough to look like the Star of Bethlehem? He found that that probably wasn't the case, as it wouldn't have been bright enough. However, there are some other possibilities. These include comets, asteroids and possibly supernovae as well. When stars explode, they can give out as much light as an entire galaxy, but they don't last for a very long time. This could be an explanation.



Why can't you tickle yourself?

Someone did a really clever experiment on this recently. They had special apparatus where they could tap your finger with this automatic device, and it made you think you were doing it yourself. They recorded to see how much they thought they were being tapped when they were actually doing it themselves and when the machine did it for them. What they found was that when the brain programmes a movement to make a sensation such as a tickle or a scratch, what it actually does is sends an inhibitory signal to the part of the brain that would normally be tickled. So in other words there is a kill joy area in the brain that says if you are tickled in this area, you will ignore the tickle. As your brain is sending the message itself, you ignore the tickle. However, when someone else tickles you, your brain doesn't know it's going to happen and turns off the kill joy signal.

- Why does some wood spit and crackle when you burn it?

When you put wood on a fire, why does some wood spit and crackle while other wood burns slowly and quietly?

Why does some wood spit and crackle when you burn it?

There are a couple of reasons for this. It's usually to do with how dry the wood is. What splits the wood apart is the expansion of pockets of water vaporising as the wood gets very hot. The expansion is like its own mini explosion.


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