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Arachnid appetite
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THE LAST WORD Many ridges to cross Back roads in Australia often have hundreds of metres of gravel corrugations, or ridges. They are always a few centimetres high, spaced about 30 centimetres apart… and annoying for vehicle occupants. What causes them?
Over time, these undulations are exacerbated by bouncing truck and car tyres. Wind and rain remove loose dirt between ridges, accentuating them. If your vehicle has feeble city tyres, not big, boofy, four-wheeldrive ones, go slowly. With either type, you can minimise the jarring by reducing tyre pressure, especially if the corrugations combine with the angular rocks of the gibber plains – the desert landscape encountered on the
n When a vehicle is driven over an unsurfaced road, its weight indents the material under the tyre. The loose particles ahead of the tyre tend to be pushed “Some people drive on the forwards, creating a small ridge. wrong side of corrugated Each passing vehicle gradually roads, as it feels smoother raises the ridge, until the rate of that way” material removal from the crest due to abrasion and impact stop it getting any taller. The maximum unsurfaced Oodnadatta Track height of the ridge depends on the in South Australia. I know this material used for the road. from personal experience. The surface of a newly levelled Bonita Ely road generally stays more or less Marrickville, New South Wales, smooth until it rains. After this, it Australia corrugates rapidly, presumably because indentation can occur n I live by a gravel road in rural Western Australia. Corrugations more easily with wet materials. are common and aren’t restricted Such ridges also occasionally to back roads. They start small and occur on bitumen roads. I used increase in size over time, until to pass a bus stop on a downhill you are unsure whether to slow slope in Sydney that developed down and feel each bump or just impressive corrugations due to go faster and ride across the tops heavy buses halting there. of the ridges. Tony Cooke Corrugations form across the Macgregor, ACT, Australia road, and are steeper on the side facing traffic flow. That is why n Gravel and dirt roads are maintained to try to keep the some people drive on the wrong surface in good condition, for side of the road when they can, example by scraping them with as it feels smoother that way. a wide blade mounted under a The material used for the road heavy vehicle. The blade bounces is an important factor in the slightly, creating undulations. corrugations. The road we live on
We pay £25 for every answer published in New Scientist. To answer a question or ask a new one please email [email protected]. Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address. You can also send questions and
answers to The Last Word, New Scientist, 25 Bedford Street, London, WC2E 9ES. New Scientist Ltd retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format and at any time in the future. All unanswered questions and previous questions and answers are at newscientist.com/lastword/
has two sections: the part covered with sand and gravel is corrugated, while the other, made with gravel and some clay, sets hard and is always in excellent condition. If motorists slow down, the likelihood of ridges forming is cut. Anna Butcher Brookton, Western Australia n The amplitude of the ridges depends on the size of wheels, the speed of vehicles and to some extent vehicle length. Larger wheels yield deeper corrugations. Higher speeds produce longer spaces between corrugations. So small vehicles using roads more usually frequented by larger, slow vehicles are worst affected. Australia’s unsealed roads are much used by large vehicles, so they develop long stretches of corrugations. Cars can minimise the bumpiness by going faster and essentially riding along the tops of the corrugations. But this is dangerous because the vehicle isn’t in contact with the ground for significant periods of time, meaning it is easy to lose control of the steering. Brian King Barton on Sea, Hampshire, UK n The ridging effect is known as washboarding. It occurs on all loose surfaces, including sand and snow. It is caused by a force acting in one direction on a movable surface, much like ripples on a lake caused by the wind. The ridges are essentially very slow waves. It helps to use a mix of particles
Watch 100 fascinating science talks! Watch mind-expanding talks from Anne-Marie Imafidon, Carlo Rovelli, Tim Peake, Megan Rossi, and many other inspiring scientists. Visit newscientist.com/nsltalks
of different sizes to make the road surface, as this prevents the material from moving as easily. Lewis O’Shaughnessy London, UK
This week’s questions
ARACHNID APPETITE
I was impressed by the size of the prey captured by this crab spider (see photo), seeing as they don’t use webs to catch food. How much of it would the spider eat and is there a “best before” date? Hugh Meteyard Theydon Bois, Essex, UK FEELING FLY
Do insects have emotions in the same way humans and mammals do? For example, would a fly feel sad if it saw its brother die? Jake Jackson Guisborough, North Yorkshire, UK
THE LAST WORD Many ridges to cross Back roads in Australia often have hundreds of metres of gravel corrugations, or ridges. They are always a few centimetres high, spaced about 30 centimetres apart… and annoying for vehicle occupants. What causes them?
Over time, these undulations are exacerbated by bouncing truck and car tyres. Wind and rain remove loose dirt between ridges, accentuating them. If your vehicle has feeble city tyres, not big, boofy, four-wheeldrive ones, go slowly. With either type, you can minimise the jarring by reducing tyre pressure, especially if the corrugations combine with the angular rocks of the gibber plains – the desert landscape encountered on the
n When a vehicle is driven over an unsurfaced road, its weight indents the material under the tyre. The loose particles ahead of the tyre tend to be pushed “Some people drive on the forwards, creating a small ridge. wrong side of corrugated Each passing vehicle gradually roads, as it feels smoother raises the ridge, until the rate of that way” material removal from the crest due to abrasion and impact stop it getting any taller. The maximum unsurfaced Oodnadatta Track height of the ridge depends on the in South Australia. I know this material used for the road. from personal experience. The surface of a newly levelled Bonita Ely road generally stays more or less Marrickville, New South Wales, smooth until it rains. After this, it Australia corrugates rapidly, presumably because indentation can occur n I live by a gravel road in rural Western Australia. Corrugations more easily with wet materials. are common and aren’t restricted Such ridges also occasionally to back roads. They start small and occur on bitumen roads. I used increase in size over time, until to pass a bus stop on a downhill you are unsure whether to slow slope in Sydney that developed down and feel each bump or just impressive corrugations due to go faster and ride across the tops heavy buses halting there. of the ridges. Tony Cooke Corrugations form across the Macgregor, ACT, Australia road, and are steeper on the side facing traffic flow. That is why n Gravel and dirt roads are maintained to try to keep the some people drive on the wrong surface in good condition, for side of the road when they can, example by scraping them with as it feels smoother that way. a wide blade mounted under a The material used for the road heavy vehicle. The blade bounces is an important factor in the slightly, creating undulations. corrugations. The road we live on
We pay £25 for every answer published in New Scientist. To answer a question or ask a new one please email [email protected]. Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address. You can also send questions and
answers to The Last Word, New Scientist, 25 Bedford Street, London, WC2E 9ES. New Scientist Ltd retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format and at any time in the future. All unanswered questions and previous questions and answers are at newscientist.com/lastword/
has two sections: the part covered with sand and gravel is corrugated, while the other, made with gravel and some clay, sets hard and is always in excellent condition. If motorists slow down, the likelihood of ridges forming is cut. Anna Butcher Brookton, Western Australia n The amplitude of the ridges depends on the size of wheels, the speed of vehicles and to some extent vehicle length. Larger wheels yield deeper corrugations. Higher speeds produce longer spaces between corrugations. So small vehicles using roads more usually frequented by larger, slow vehicles are worst affected. Australia’s unsealed roads are much used by large vehicles, so they develop long stretches of corrugations. Cars can minimise the bumpiness by going faster and essentially riding along the tops of the corrugations. But this is dangerous because the vehicle isn’t in contact with the ground for significant periods of time, meaning it is easy to lose control of the steering. Brian King Barton on Sea, Hampshire, UK n The ridging effect is known as washboarding. It occurs on all loose surfaces, including sand and snow. It is caused by a force acting in one direction on a movable surface, much like ripples on a lake caused by the wind. The ridges are essentially very slow waves. It helps to use a mix of particles
Watch 100 fascinating science talks! Watch mind-expanding talks from Anne-Marie Imafidon, Carlo Rovelli, Tim Peake, Megan Rossi, and many other inspiring scientists. Visit newscientist.com/nsltalks
of different sizes to make the road surface, as this prevents the material from moving as easily. Lewis O’Shaughnessy London, UK
This week’s questions
ARACHNID APPETITE
I was impressed by the size of the prey captured by this crab spider (see photo), seeing as they don’t use webs to catch food. How much of it would the spider eat and is there a “best before” date? Hugh Meteyard Theydon Bois, Essex, UK FEELING FLY
Do insects have emotions in the same way humans and mammals do? For example, would a fly feel sad if it saw its brother die? Jake Jackson Guisborough, North Yorkshire, UK