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Colour code
THE LAST WORD Colour code When part-time traffic lights switch on, what signal do they display? Red would lead to panic braking, green in all directions would invite an accident. So what do they do to avoid chaos?
n By eliminating red or green
as unsafe, you already have the answer. The only remaining colour, yellow (or amber as it more usually known), is indeed what full and part-time UK traffic signals are programmed to display when they are switched on and when they resume operation after a power cut or other failure. Three seconds of amber is followed by a short period of “all red” before the signals revert to normal operation, all traffic having been brought to rest safely. Simon Morgan Northwood, Middlesex, UK
Last words past and present, plus questions, at last-word.com
decide how fast other cars are going and how likely they are to stop. Drivers become accustomed to making instant judgements along the lines of “Is he bigger than me?” and “Is his car worth more, or less, than mine?”. Battered white vans and buses always have right of way, unless you’re in a particularly bad mood. Occasionally the passage of a vehicle infringing the “priorité à droite” rule is accompanied by frenzied hooting, but you tend not to find that all the traffic has ground to a halt while the combatants sort it out. The entertainment value of these junctions is much increased on Thursdays when a market occupies the car park between the two crossroads, invariably meaning that vans, left wherever the driver felt most convenient, obscure the lines of sight, including those to the pedestrian crossings. Astonishingly, in the 19 years I have lived here, I have never heard of an accident. Perhaps when you know that you can hit someone at any moment you slow down and take care. Perhaps, to drivers, a green light signalling “move” negates any need to look. Has anyone done any comparative safety studies? Halina Stanley Revel, France
n A more interesting question is what happens at relatively busy junctions where part-time traffic lights have been switched off? Who has right of way? In the town centre closest to my house there are two crossroads where the traffic lights almost never function as traffic lights – they just flash amber. Here in France the rule is “priorité à droite” (priority to the right), but an alternative rule “he “Here in France the rule is who arrives first, goes first” is often applied by drivers. The latter ‘priority to the right’, but ‘he who arrives first, goes puts a great deal of randomness first’ is often applied” into the equation. You need to
Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
Ring of doom A fungus is spreading in the garden of our summer cottage. It forms a ring, which has grown year by year and is now about 8 metres in diameter. Large mushroom-like fungi spring up after each rainfall and then appear to take moisture from the lawn and the roots of bushes, drying them out. Why does it form a ring and why does the ring only spread outwards. And how do we get rid of it?
n The lawn has “fairy-ring fungus”, which could be one of many grassland species. The most common and troublesome, with a fondness for short turf, is Marasmius oreades, which sends up mushrooms at certain times of the year. These are the fruiting bodies of a hidden, filamentous fungus which may live for centuries. It feeds on dead vegetable matter and spreads out as it exhausts its food supply. The most widely accepted explanation for the death of the grass is that the fungal filaments, or mycelia, form a dense mass preventing water soaking into the soil. Paradoxically, fairy-ring fungi may also feed neighbouring grasses by releasing nitrogen as they break down their food, and this causes the rank, dark-green growth described by Shakespeare as “the green sour ringlets... whereof the ewe not bites”. Getting rid of a fairy ring is not easy. Weedkillers don’t work against the fungus, and there does not seem to be an effective
anti-fungal treatment on the market. The fungus penetrates the soil to a depth of at least 30 centimetres, making physical removal hard work. The best answer gardening experts can come up with is to support the growth of grass by spiking affected areas and pouring in as much water as possible, mixed with a little washing-up liquid to attempt to damage the fungus. It is worth noting that an attack on a ring may have unpleasant consequences. It is believed across Europe that the Little People do not like such interference. Christine Warman Saltburn-by-the-Sea, North Yorkshire, UK
This week’s questions Bug wash
I want to know if washing vegetables that you would normally eat raw is any protection against illnesses such as the German E. coli outbreak thought to have been caused by contaminated salads. It seems that holding the produce in running water from a tap will have limited success in removing contaminants. Am I right? Peter Mariani Newcastle, New South Wales, Australia The wobblies
Why do my legs become wobbly when I stand near a cliff top? Caroline Clarke Dublin, Ireland
Why can’t elephants jump? The latest collection: witty, brilliant, intelligent and packed with insight Available from booksellers and at www.newscientist.com/elephants
n By eliminating red or green
as unsafe, you already have the answer. The only remaining colour, yellow (or amber as it more usually known), is indeed what full and part-time UK traffic signals are programmed to display when they are switched on and when they resume operation after a power cut or other failure. Three seconds of amber is followed by a short period of “all red” before the signals revert to normal operation, all traffic having been brought to rest safely. Simon Morgan Northwood, Middlesex, UK
Last words past and present, plus questions, at last-word.com
decide how fast other cars are going and how likely they are to stop. Drivers become accustomed to making instant judgements along the lines of “Is he bigger than me?” and “Is his car worth more, or less, than mine?”. Battered white vans and buses always have right of way, unless you’re in a particularly bad mood. Occasionally the passage of a vehicle infringing the “priorité à droite” rule is accompanied by frenzied hooting, but you tend not to find that all the traffic has ground to a halt while the combatants sort it out. The entertainment value of these junctions is much increased on Thursdays when a market occupies the car park between the two crossroads, invariably meaning that vans, left wherever the driver felt most convenient, obscure the lines of sight, including those to the pedestrian crossings. Astonishingly, in the 19 years I have lived here, I have never heard of an accident. Perhaps when you know that you can hit someone at any moment you slow down and take care. Perhaps, to drivers, a green light signalling “move” negates any need to look. Has anyone done any comparative safety studies? Halina Stanley Revel, France
n A more interesting question is what happens at relatively busy junctions where part-time traffic lights have been switched off? Who has right of way? In the town centre closest to my house there are two crossroads where the traffic lights almost never function as traffic lights – they just flash amber. Here in France the rule is “priorité à droite” (priority to the right), but an alternative rule “he “Here in France the rule is who arrives first, goes first” is often applied by drivers. The latter ‘priority to the right’, but ‘he who arrives first, goes puts a great deal of randomness first’ is often applied” into the equation. You need to
Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
Ring of doom A fungus is spreading in the garden of our summer cottage. It forms a ring, which has grown year by year and is now about 8 metres in diameter. Large mushroom-like fungi spring up after each rainfall and then appear to take moisture from the lawn and the roots of bushes, drying them out. Why does it form a ring and why does the ring only spread outwards. And how do we get rid of it?
n The lawn has “fairy-ring fungus”, which could be one of many grassland species. The most common and troublesome, with a fondness for short turf, is Marasmius oreades, which sends up mushrooms at certain times of the year. These are the fruiting bodies of a hidden, filamentous fungus which may live for centuries. It feeds on dead vegetable matter and spreads out as it exhausts its food supply. The most widely accepted explanation for the death of the grass is that the fungal filaments, or mycelia, form a dense mass preventing water soaking into the soil. Paradoxically, fairy-ring fungi may also feed neighbouring grasses by releasing nitrogen as they break down their food, and this causes the rank, dark-green growth described by Shakespeare as “the green sour ringlets... whereof the ewe not bites”. Getting rid of a fairy ring is not easy. Weedkillers don’t work against the fungus, and there does not seem to be an effective
anti-fungal treatment on the market. The fungus penetrates the soil to a depth of at least 30 centimetres, making physical removal hard work. The best answer gardening experts can come up with is to support the growth of grass by spiking affected areas and pouring in as much water as possible, mixed with a little washing-up liquid to attempt to damage the fungus. It is worth noting that an attack on a ring may have unpleasant consequences. It is believed across Europe that the Little People do not like such interference. Christine Warman Saltburn-by-the-Sea, North Yorkshire, UK
This week’s questions Bug wash
I want to know if washing vegetables that you would normally eat raw is any protection against illnesses such as the German E. coli outbreak thought to have been caused by contaminated salads. It seems that holding the produce in running water from a tap will have limited success in removing contaminants. Am I right? Peter Mariani Newcastle, New South Wales, Australia The wobblies
Why do my legs become wobbly when I stand near a cliff top? Caroline Clarke Dublin, Ireland
Why can’t elephants jump? The latest collection: witty, brilliant, intelligent and packed with insight Available from booksellers and at www.newscientist.com/elephants