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Shivering timbers
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THE LAST WORD Clucking on
Treading lightly
Why do hens cluck loudly after laying an egg?
By UK law, car tyres must have a tread at least 1.6 mm deep. It is about 9 mm on my new tyres. At what point would deeper treads worsen road holding and why?
n I have kept domestic fowl free-range for almost 60 years, namely bantams and silver-laced Wyandottes. This is what I have observed: a hen enters the nest 10 to 20 minutes before laying and settles herself. She stands to lay the egg, which is soft-shelled and hardens on contact with the air. She then sits quietly for a few minutes, preening, crooning and resting. The hen then jumps up from the nest with a loud cackle and, given the freedom of the range, runs a considerable distance. The dominant rooster hears the cackling, runs with wings outstretched to the hen and mates with her immediately. He then performs a “stamping” display and both go off happy. So it seems that the cackle helps to attract the rooster to mate once an egg is laid. If there are rival males, the rooster will patrol outside the nest like any expectant father, and then mate with the hen as soon as she has finished laying. In that case, the cackle may be quiet to non-existent. When mating at other times, the stamping display comes beforehand and there is no cackling. Nina Dougall Malmsbury, Victoria, Australia
The writers of answers that are published in the magazine will receive a cheque for £25 (or US$ equivalent). Answers should be concise. We reserve the right to edit items for clarity and style. Please include a daytime telephone number and an email address if you have one. New Scientist retains total editorial control over the published content. Reed Business Information Ltd reserves all rights to reuse all question and answer material that has been
n Tyres do not need grooves to improve grip in dry weather. This is demonstrated in motor racing, in which smooth “slick” tyres are the rule. These are used unless it is wet, when the addition of grooves allows a tyre to squeeze away water that would otherwise lubricate it and remove grip. The heavier the rain, the deeper and more numerous the grooves. New road tyres have sufficient grooves for all but very heavy rain. But as they wear, their capacity to shift water drops because the grooves become shallower, until
they are insufficient even for light terrain well, but is heavy and noisy on tarmac. The heavy tread means rain – which is the limit for legal that it won’t rebound so quickly to tyres as noted in the question the relatively small stones on the (with a safety margin added). The deeper the grooves, the less road, so its grip is poor. Modern tyres on racing bicycles are thin grip the tyres have because less rubber touches the road and the parts between the grooves move “The deeper the grooves, about. So on a dry road, any groove the less tyres will grip because less rubber inhibits grip. But unless you can touches the road” do a pit stop as soon as it rains, you are still better off with grooved tyres for road use, purely to ensure and light. The tread layer has low mass so it can follow small road you can drive in all conditions. undulations, providing good grip. John Davies Because the internal pressure of Haverbreaks, Lancashire, UK the tyre is high, it pushes through any water, so even slick tyres grip n The maximum tyre tread before the ride becomes too rough well in the wet. On a good road you can do over 40 miles per hour depends on the kind of road on in comfort. But the tyres have zero which you’re driving, and what suspension you have. Bicycle tyres grip on slimy mud when cycling. Simon Dales are a good example – a thick knobbly tyre grips mud and loose Oxford, UK
This week’s questions Total recall
When I can’t remember something, how do I know that I ever knew it in the first place? John Ripley Leeds, West Yorkshire, UK Shivering timbers
This photo was taken at Vieux Port in Marseille, France. Can anybody explain why the distribution of ripples varies so much that some of the mast reflections have large “waves” in them, whereas others are almost straight? Clive Wilkinson Townsville, Queensland, Australia
submitted by readers in any medium or in any format and at any time in the future. Send questions and answers to The Last Word, New Scientist, 110 High Holborn, London WC1V 6EU, UK, by email to [email protected] or visit www.newscientist.com/topic/lastword (please include a postal address in order to receive payment for answers). Unanswered questions can also be found at this URL.
Question Everything The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything
THE LAST WORD Clucking on
Treading lightly
Why do hens cluck loudly after laying an egg?
By UK law, car tyres must have a tread at least 1.6 mm deep. It is about 9 mm on my new tyres. At what point would deeper treads worsen road holding and why?
n I have kept domestic fowl free-range for almost 60 years, namely bantams and silver-laced Wyandottes. This is what I have observed: a hen enters the nest 10 to 20 minutes before laying and settles herself. She stands to lay the egg, which is soft-shelled and hardens on contact with the air. She then sits quietly for a few minutes, preening, crooning and resting. The hen then jumps up from the nest with a loud cackle and, given the freedom of the range, runs a considerable distance. The dominant rooster hears the cackling, runs with wings outstretched to the hen and mates with her immediately. He then performs a “stamping” display and both go off happy. So it seems that the cackle helps to attract the rooster to mate once an egg is laid. If there are rival males, the rooster will patrol outside the nest like any expectant father, and then mate with the hen as soon as she has finished laying. In that case, the cackle may be quiet to non-existent. When mating at other times, the stamping display comes beforehand and there is no cackling. Nina Dougall Malmsbury, Victoria, Australia
The writers of answers that are published in the magazine will receive a cheque for £25 (or US$ equivalent). Answers should be concise. We reserve the right to edit items for clarity and style. Please include a daytime telephone number and an email address if you have one. New Scientist retains total editorial control over the published content. Reed Business Information Ltd reserves all rights to reuse all question and answer material that has been
n Tyres do not need grooves to improve grip in dry weather. This is demonstrated in motor racing, in which smooth “slick” tyres are the rule. These are used unless it is wet, when the addition of grooves allows a tyre to squeeze away water that would otherwise lubricate it and remove grip. The heavier the rain, the deeper and more numerous the grooves. New road tyres have sufficient grooves for all but very heavy rain. But as they wear, their capacity to shift water drops because the grooves become shallower, until
they are insufficient even for light terrain well, but is heavy and noisy on tarmac. The heavy tread means rain – which is the limit for legal that it won’t rebound so quickly to tyres as noted in the question the relatively small stones on the (with a safety margin added). The deeper the grooves, the less road, so its grip is poor. Modern tyres on racing bicycles are thin grip the tyres have because less rubber touches the road and the parts between the grooves move “The deeper the grooves, about. So on a dry road, any groove the less tyres will grip because less rubber inhibits grip. But unless you can touches the road” do a pit stop as soon as it rains, you are still better off with grooved tyres for road use, purely to ensure and light. The tread layer has low mass so it can follow small road you can drive in all conditions. undulations, providing good grip. John Davies Because the internal pressure of Haverbreaks, Lancashire, UK the tyre is high, it pushes through any water, so even slick tyres grip n The maximum tyre tread before the ride becomes too rough well in the wet. On a good road you can do over 40 miles per hour depends on the kind of road on in comfort. But the tyres have zero which you’re driving, and what suspension you have. Bicycle tyres grip on slimy mud when cycling. Simon Dales are a good example – a thick knobbly tyre grips mud and loose Oxford, UK
This week’s questions Total recall
When I can’t remember something, how do I know that I ever knew it in the first place? John Ripley Leeds, West Yorkshire, UK Shivering timbers
This photo was taken at Vieux Port in Marseille, France. Can anybody explain why the distribution of ripples varies so much that some of the mast reflections have large “waves” in them, whereas others are almost straight? Clive Wilkinson Townsville, Queensland, Australia
submitted by readers in any medium or in any format and at any time in the future. Send questions and answers to The Last Word, New Scientist, 110 High Holborn, London WC1V 6EU, UK, by email to [email protected] or visit www.newscientist.com/topic/lastword (please include a postal address in order to receive payment for answers). Unanswered questions can also be found at this URL.
Question Everything The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything