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THE LAST WORD Radio gaga A car radio needs an external aerial to stop the car itself interfering with the signal. Yet the fob on the car key also works by radio and is effective even if I hold it near the steel garage door with the car on the other side. So how does it work?
n Metal is effectively opaque to all but the most energetic electromagnetic radiation, so most vehicles act as a Faraday cage, whereby the radiation is distributed around the exterior. However, some electromagnetic waves can pass through car windows – most notably visible light. Remote keyless systems operate at a frequency of 433.92 megahertz in cars manufactured in Europe. This corresponds to a wavelength of about 0.7 metres, which means that the signal from a fob can pass through the windows to reach the transceiver inside. But some wavelengths are simply too big to travel through the windows, and for these the car might as well be a solid metal box.
should be one-quarter of the signal’s wavelength, but this is clearly impractical for many wavelengths. Mike Follows Sutton Coldfield, West Midlands, UK
Everything but the curl I’ve been making notes to revise for my exams, and as I write, the pages curl inwards first from the top corners of the paper, and then the bottom corners. Why is this? I’m using a black ballpoint pen on white A4 printer paper.
FM radio signals can be as short as about 3 metres, but AM signals range from more than 100 metres to half a kilometre. This is why cars are fitted with external aerials. Ideally, their length
n I suspect your note-writing is quite small and closely spaced, and that you apply more pressure than normal with the pen. This compresses the fibres of the paper and causes them to expand sideways, thus effectively stretching the paper below the pen. Because you don’t write to the top, bottom and edges of the sheet, these parts remain unaffected and so curl up. A classic example of this effect, but for a different reason, is a sandwich left out in the sun. Most people will notice that the corners and edges soon start to curl, and it will have become unpalatable. This time, the phenomenon is caused by the sides and upper surface of the bread drying out and shrinking. The stretching effect caused by pressure is used by manufacturers to produce curved skin panels for
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
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.
“Some radio wavelengths are simply too big to pass through car windows, hence car aerials”
custom-built cars and aircraft. A machine called an English wheel is used for this purpose. This consists of a rigid “G”-shaped frame supporting a large, flat wheel. Below this is a smaller wheel with a curved edge. A sheet of metal is fed between the wheels and worked back and forth. In the hands of a skilled operator, quite complex shapes can be produced. There are many
“A sandwich left out in the sun will soon start to curl at the corners and edges, and become unpalatable” videos online that show the machine in action. Before the invention of the English wheel, the stretch-shaping of metal was achieved with a hammer. Bob Halahan Godalming, Surrey, UK
This week’s questions Disease-proof
If you have a few drinks, does the alcohol in your bloodstream act as medication against any microbes in the body? Adam Wilson Leigh-on-Sea, Essex, UK Catch a falling star
How long would it take for all our space junk to fall back to earth and burn up in the atmosphere? Renee Colwell New York City, US
Polar trader
If I bought 1000 tonnes of gold bullion in Antarctica and sold it in Mexico at the same price per kilogram, would I make a loss? Surely the consignment would be lighter at the equator than the poles because it is spinning faster? Richard Byrne Swanmore, Hampshire, UK Colour wash
My bath water is pale blue in Paris, but pale green in Berlin. What causes this? The pipes, water hardness or something else? Brian Smith Berlin, Germany Nighthawks
The gulls where I live on the south coast of England can be heard squawking day and night. Why aren’t they quiet, and presumably asleep, like other birds at night? Dawn McNally Brighton, UK UNsuitable SUIT
I read that Neil Armstrong’s spacesuit from his moon landing is deteriorating. It was, apparently, made out of materials created for only short-term use. Why was this and what are these materials? How can the suit be preserved? The spacesuit of another Apollo astronaut, David Scott, is on display in the Smithsonian National Air and Space Museum in Washington DC. This suit looks pretty much intact, so was it made of different materials? Alan Brewer Washington DC, US
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 Radio gaga A car radio needs an external aerial to stop the car itself interfering with the signal. Yet the fob on the car key also works by radio and is effective even if I hold it near the steel garage door with the car on the other side. So how does it work?
n Metal is effectively opaque to all but the most energetic electromagnetic radiation, so most vehicles act as a Faraday cage, whereby the radiation is distributed around the exterior. However, some electromagnetic waves can pass through car windows – most notably visible light. Remote keyless systems operate at a frequency of 433.92 megahertz in cars manufactured in Europe. This corresponds to a wavelength of about 0.7 metres, which means that the signal from a fob can pass through the windows to reach the transceiver inside. But some wavelengths are simply too big to travel through the windows, and for these the car might as well be a solid metal box.
should be one-quarter of the signal’s wavelength, but this is clearly impractical for many wavelengths. Mike Follows Sutton Coldfield, West Midlands, UK
Everything but the curl I’ve been making notes to revise for my exams, and as I write, the pages curl inwards first from the top corners of the paper, and then the bottom corners. Why is this? I’m using a black ballpoint pen on white A4 printer paper.
FM radio signals can be as short as about 3 metres, but AM signals range from more than 100 metres to half a kilometre. This is why cars are fitted with external aerials. Ideally, their length
n I suspect your note-writing is quite small and closely spaced, and that you apply more pressure than normal with the pen. This compresses the fibres of the paper and causes them to expand sideways, thus effectively stretching the paper below the pen. Because you don’t write to the top, bottom and edges of the sheet, these parts remain unaffected and so curl up. A classic example of this effect, but for a different reason, is a sandwich left out in the sun. Most people will notice that the corners and edges soon start to curl, and it will have become unpalatable. This time, the phenomenon is caused by the sides and upper surface of the bread drying out and shrinking. The stretching effect caused by pressure is used by manufacturers to produce curved skin panels for
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
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.
“Some radio wavelengths are simply too big to pass through car windows, hence car aerials”
custom-built cars and aircraft. A machine called an English wheel is used for this purpose. This consists of a rigid “G”-shaped frame supporting a large, flat wheel. Below this is a smaller wheel with a curved edge. A sheet of metal is fed between the wheels and worked back and forth. In the hands of a skilled operator, quite complex shapes can be produced. There are many
“A sandwich left out in the sun will soon start to curl at the corners and edges, and become unpalatable” videos online that show the machine in action. Before the invention of the English wheel, the stretch-shaping of metal was achieved with a hammer. Bob Halahan Godalming, Surrey, UK
This week’s questions Disease-proof
If you have a few drinks, does the alcohol in your bloodstream act as medication against any microbes in the body? Adam Wilson Leigh-on-Sea, Essex, UK Catch a falling star
How long would it take for all our space junk to fall back to earth and burn up in the atmosphere? Renee Colwell New York City, US
Polar trader
If I bought 1000 tonnes of gold bullion in Antarctica and sold it in Mexico at the same price per kilogram, would I make a loss? Surely the consignment would be lighter at the equator than the poles because it is spinning faster? Richard Byrne Swanmore, Hampshire, UK Colour wash
My bath water is pale blue in Paris, but pale green in Berlin. What causes this? The pipes, water hardness or something else? Brian Smith Berlin, Germany Nighthawks
The gulls where I live on the south coast of England can be heard squawking day and night. Why aren’t they quiet, and presumably asleep, like other birds at night? Dawn McNally Brighton, UK UNsuitable SUIT
I read that Neil Armstrong’s spacesuit from his moon landing is deteriorating. It was, apparently, made out of materials created for only short-term use. Why was this and what are these materials? How can the suit be preserved? The spacesuit of another Apollo astronaut, David Scott, is on display in the Smithsonian National Air and Space Museum in Washington DC. This suit looks pretty much intact, so was it made of different materials? Alan Brewer Washington DC, US
Question Everything The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything