| Dr Hypothesis - Q&A |
| Wednesday, 26 April 2006 | |
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Dear Dr Hypothesis, I have recently been asked to participate in an experiment looking at the effect of coffee on the brain. Keen though I am to help the advance of science, part of this would involve being subjected to a Magnetic Resonance Imaging (MRI) scan. I haven’t been in a hospital for many years and I don’t like the idea of any chemicals being injected into my body. What exactly is involved in an MRI scan, and how are the images produced from it? Caffeinated Carl DR HYPOTHESIS SAYS: Carl, there’s no need to worry—MRI is a technique carried out in hospitals every day. The machine applies a magnetic field straight down the body, causing the majority of the protons in the hydrogen atoms of the body to line up along this field. A radio pulse is then applied to these atoms, which makes them spin slightly differently. Once this pulse is removed, the spins of the atoms gradually return to their previous state, releasing energy. It is this release of energy that varies for different patterns of hydrogen atoms.This is visualised on the computer without the need for any invasive procedure. No nasty chemicals will be injected into your body. Dear Dr Hypothesis, I must confess that I ate one too many Easter eggs over the holidays and, with the stress of exam term coming on, I’ve let my diet slip over the last couple of weeks. It was when I clambered into the shower and felt the curtain brush up against me that I first noticed how much more space I was taking up. Could you please tell me why the shower curtain gets sucked inwards when I turn on the shower? Is there any way to prevent this daily reminder of all that chocolate? Clean Carmella DR HYPOTHESIS SAYS: The curtain is dragged in towards you because there is a lower air pressure inside the shower than outside. This is caused by the faster flow of air downwards in the shower as it is dragged with the water. Computer modelling has shown that this forms a mini-cyclone just as is seen (admittedly on a larger scale) in weather patterns. I’m afraid, Carmella, that there isn’t much you can do to avoid this. So, if it upsets you, it’s probably time to get on that treadmill.
Dear Dr Hypothesis, I have only just returned home from a rather lengthy stay in hospital after an experiment I conducted during the winter went badly wrong. I was interested in finding out why salt is spread onto icy roads. To investigate this, I used a number of different household products to try to melt the ice on my garden path. Needless to say, none of them were successful and I slipped, leading to my trip to the hospital. Do you know why salt, specifically, is used on icy roads? Limping Lorna DR HYPOTHESIS SAYS: I’d first like to warn my readers of the dangers of experimenting alone—I’m sure Lorna would agree! Regarding the question, salt is spread on roads so that when it dissolves in any water present it lowers the melting point as far as –9°C, preventing ice formation. The decision to use salt, rather than another soluble compound with a similar property, is likely to be based on cost; glycol, for example, costs up to 20 times as much as salt and so is only rarely used. Glycol is usually only used on bridges where its non-corrosive nature is important. Glasgow City Council on the salt they use |
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