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Caterpillar plague strikes West Africa
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THIS WEEK coincidence. A hollowed-out hemisphere with a hole in the top was a type of sundial used in Roman times, albeit on a much smaller scale, to show the time of year. While the Pantheon’s dome is quite flat on the outside, it forms a perfect hemisphere inside. “This is quite a deliberate design feature,” says Hannah. Pantheon means “all of the gods” and the building’s roof represented the dome of the sky, where Romans believed the gods resided. At equinox, the sun is on the celestial equator – where Earth’s equator would lie if projected into space – which was seen as the most stable part of the sky, a perfect eternal home for –Light on time– the gods. Hannah thinks that by marking the equinoxes, the Pantheon was intended to elevate emperors who worshipped there into the realm of the gods. James Evans, a historian of astronomy at the University of Puget Sound in Washington state, is intrigued: “The architect of the and floor. At the two equinoxes, Pantheon would certainly have in March and September, the been aware of the symbolic sunlight coming in through the connections between the cosmos hole strikes the junction between and the empire, and between the the roof and wall, above the sun and the emperor.” He doesn’t Pantheon’s grand northern believe the case is proven, however, doorway (pictured). A grille above as no markings survive in the the door allows a sliver of light Pantheon that relate to a sundial. through to the front courtyard – Hannah counters that sundials the only moment in the year that rarely came with instructions: it sees sunlight if its main doors “They were part of the culture, are closed (see diagram). they wouldn’t need to explain Hannah reckons this is no themselves.” ■
Is this the boldest sundial ever built? Jo Marchant
HAS the grand Roman Pantheon been keeping a secret for nearly 2000 years? An expert in ancient timekeeping thinks so, arguing that it acts as a colossal sundial. The imposing temple in Rome, completed in AD 128, is one of the most impressive buildings that survives from antiquity. It consists of a cylindrical chamber topped by a domed roof with an oculus in the top which lets through a dramatic shaft of sunlight. It boasts a colonnaded courtyard at the front. When Robert Hannah of the University of Otago in Dunedin, New Zealand, visited the Pantheon in 2005, researching for a book (see “Changing time”, p 45), he realised that the Pantheon may have been more than just a temple. During the six months of winter, the light of the noon sun traces a path across the inside of the domed roof. During summer, with the sun higher in the sky, the shaft shines onto the lower walls 12 | NewScientist | 31 January 2009
The ultimate sundial Only at noon on an equinox does the sun shine through the Pantheon’s oculus at the perfect angle to pass through a grille above the closed door and light up the front courtyard
48°
NORTH
43.3 metres
Caterpillar plague strikes west Africa A THRONG of crop-eating caterpillars is threatening food supplies across west Africa, and could prove hard to control with pesticides. The crawling menace has appeared in northern Liberia, where hundreds of millions of the black, hairy larvae are devouring plants, fouling wells with their faeces and even driving farmers from fields. They are now crossing into neighbouring Guinea, and the UN Food and Agriculture Organization (FAO) warns that in two to three weeks they will turn into moths that can fly hundreds of kilometres and could spread across west Africa, worsening food shortages in the region. “The species is so far unknown,” FAO entomologist Winfred Hammond told New Scientist from Accra in Ghana, where Liberian specimens were being flown for analysis. Several species of African caterpillars swarm over crops but unlike the best-known species, army worms, the newly discovered Liberian caterpillars reportedly climb trees to get away from handsprayed insecticides on the ground. Aerial spraying might kill them but the FAO fears this will contaminate water supplies. Although too late to help farmers this year, a bio-pesticide already developed for army worms could be adapted for the new species. The idea would be to infect the caterpillars with a virus specific to that species, and then use mashed-up infected caterpillars against the rest. Such a pesticide could be made locally for a third of the cost of chemical sprays. But there is a hitch: though UK agencies funded the pesticide’s development, commercialisation has stalled for lack of funds. “It has been “extremely difficult to get £1.25 million for producing it locally,” says Ken Wilson of Lancaster University in the UK. Debora MacKenzie ■
THIS WEEK coincidence. A hollowed-out hemisphere with a hole in the top was a type of sundial used in Roman times, albeit on a much smaller scale, to show the time of year. While the Pantheon’s dome is quite flat on the outside, it forms a perfect hemisphere inside. “This is quite a deliberate design feature,” says Hannah. Pantheon means “all of the gods” and the building’s roof represented the dome of the sky, where Romans believed the gods resided. At equinox, the sun is on the celestial equator – where Earth’s equator would lie if projected into space – which was seen as the most stable part of the sky, a perfect eternal home for –Light on time– the gods. Hannah thinks that by marking the equinoxes, the Pantheon was intended to elevate emperors who worshipped there into the realm of the gods. James Evans, a historian of astronomy at the University of Puget Sound in Washington state, is intrigued: “The architect of the and floor. At the two equinoxes, Pantheon would certainly have in March and September, the been aware of the symbolic sunlight coming in through the connections between the cosmos hole strikes the junction between and the empire, and between the the roof and wall, above the sun and the emperor.” He doesn’t Pantheon’s grand northern believe the case is proven, however, doorway (pictured). A grille above as no markings survive in the the door allows a sliver of light Pantheon that relate to a sundial. through to the front courtyard – Hannah counters that sundials the only moment in the year that rarely came with instructions: it sees sunlight if its main doors “They were part of the culture, are closed (see diagram). they wouldn’t need to explain Hannah reckons this is no themselves.” ■
Is this the boldest sundial ever built? Jo Marchant
HAS the grand Roman Pantheon been keeping a secret for nearly 2000 years? An expert in ancient timekeeping thinks so, arguing that it acts as a colossal sundial. The imposing temple in Rome, completed in AD 128, is one of the most impressive buildings that survives from antiquity. It consists of a cylindrical chamber topped by a domed roof with an oculus in the top which lets through a dramatic shaft of sunlight. It boasts a colonnaded courtyard at the front. When Robert Hannah of the University of Otago in Dunedin, New Zealand, visited the Pantheon in 2005, researching for a book (see “Changing time”, p 45), he realised that the Pantheon may have been more than just a temple. During the six months of winter, the light of the noon sun traces a path across the inside of the domed roof. During summer, with the sun higher in the sky, the shaft shines onto the lower walls 12 | NewScientist | 31 January 2009
The ultimate sundial Only at noon on an equinox does the sun shine through the Pantheon’s oculus at the perfect angle to pass through a grille above the closed door and light up the front courtyard
48°
NORTH
43.3 metres
Caterpillar plague strikes west Africa A THRONG of crop-eating caterpillars is threatening food supplies across west Africa, and could prove hard to control with pesticides. The crawling menace has appeared in northern Liberia, where hundreds of millions of the black, hairy larvae are devouring plants, fouling wells with their faeces and even driving farmers from fields. They are now crossing into neighbouring Guinea, and the UN Food and Agriculture Organization (FAO) warns that in two to three weeks they will turn into moths that can fly hundreds of kilometres and could spread across west Africa, worsening food shortages in the region. “The species is so far unknown,” FAO entomologist Winfred Hammond told New Scientist from Accra in Ghana, where Liberian specimens were being flown for analysis. Several species of African caterpillars swarm over crops but unlike the best-known species, army worms, the newly discovered Liberian caterpillars reportedly climb trees to get away from handsprayed insecticides on the ground. Aerial spraying might kill them but the FAO fears this will contaminate water supplies. Although too late to help farmers this year, a bio-pesticide already developed for army worms could be adapted for the new species. The idea would be to infect the caterpillars with a virus specific to that species, and then use mashed-up infected caterpillars against the rest. Such a pesticide could be made locally for a third of the cost of chemical sprays. But there is a hitch: though UK agencies funded the pesticide’s development, commercialisation has stalled for lack of funds. “It has been “extremely difficult to get £1.25 million for producing it locally,” says Ken Wilson of Lancaster University in the UK. Debora MacKenzie ■