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Goose blood runs cold
News Animal physiology
Goose blood runs cold
Some birds have unusual ways to cope with high-altitude flying BAR-HEADED geese migrate across the Himalayas, reaching altitudes of up to 7270 metres where the thin air contains just 30 to 50 per cent of the oxygen that air at sea level has. To understand this feat, Jessica Meir at NASA’s Johnson Space Center in Texas and her colleagues raised bar-headed geese from eggs so that the birds would imprint on them, seeing them as their parents. Then, they trained the birds to fly in a wind tunnel wearing a breathing mask that simulated the limited oxygen at high altitudes. They discovered that the geese lowered their metabolism during these taxing flights and their heart rates didn’t increase. The team also found that the blood in the birds’ veins cooled as they flew in the wind tunnel (eLife, doi.org/c96s). Cold blood can carry more oxygen than warm blood, which may help the geese fuel the muscles that help them fly. ❚
OHN DOWNER/GETTY
Chelsea Whyte
Maths
Elusive mystery of the number 42 solved IT MIGHT not tell us the meaning of life, the universe and everything, but mathematicians have cracked a tricky problem involving the number 42. The origins of this puzzle go back a long way. In 1825, a mathematician known as S. Ryley proved that any fraction could be represented as the sum of three cubes of fractions. Then, in the 1950s, a mathematician named Louis Mordell asked whether the same could be done for integers, or whole numbers. In other words, are there whole numbers k, x, y and z such that k = x3 + y3 + z3 for each possible value of k? It is an example of a maths riddle that is easy to state 14 | New Scientist | 14 September 2019
but fiendishly difficult to solve. Andrew Booker at the University of Bristol, UK, and Andrew Sutherland at the Massachusetts Institute of Technology have now solved the problem for 42, the only
“It is an example of a maths riddle that is easy to state but fiendishly difficult to solve” number under 100 for which a solution hadn’t been found. Some numbers have simple solutions. The number 3, for example, can be expressed as 13 + 13 + 13 and 43 + 43 + (-5)3. But solving the problem for other
numbers requires vast strings of digits and computing power. The solution for 42, which Booker and Sutherland found using an algorithm, is: 42 = (-80538738812075974)3 + 804357581458175153 + 126021232973356313. They worked with software firm Charity Engine to run the program across more than 400,000 volunteers’ idle computers, using processing power that would otherwise be wasted. It is equivalent to a single computer processor running continuously for more than 50 years, says Sutherland. Earlier this year, Booker found a sum of cubes for the number 33,
which was previously the lowest unsolved example. We know for certain that some whole numbers, such as 4, 5 and 13, can’t be expressed as the sum of three cubes. However, the problem is still unsolved for 10 numbers under 1000, the smallest of which is 114. The team will next search for another solution to the number 3. “It’s possible we’ll find it in the next few months; it’s possible it won’t be for another 100 years,” says Booker. Those interested in aiding the search can volunteer computing power through Charity Engine, says Sutherland. ❚ Donna Lu
Goose blood runs cold
Some birds have unusual ways to cope with high-altitude flying BAR-HEADED geese migrate across the Himalayas, reaching altitudes of up to 7270 metres where the thin air contains just 30 to 50 per cent of the oxygen that air at sea level has. To understand this feat, Jessica Meir at NASA’s Johnson Space Center in Texas and her colleagues raised bar-headed geese from eggs so that the birds would imprint on them, seeing them as their parents. Then, they trained the birds to fly in a wind tunnel wearing a breathing mask that simulated the limited oxygen at high altitudes. They discovered that the geese lowered their metabolism during these taxing flights and their heart rates didn’t increase. The team also found that the blood in the birds’ veins cooled as they flew in the wind tunnel (eLife, doi.org/c96s). Cold blood can carry more oxygen than warm blood, which may help the geese fuel the muscles that help them fly. ❚
OHN DOWNER/GETTY
Chelsea Whyte
Maths
Elusive mystery of the number 42 solved IT MIGHT not tell us the meaning of life, the universe and everything, but mathematicians have cracked a tricky problem involving the number 42. The origins of this puzzle go back a long way. In 1825, a mathematician known as S. Ryley proved that any fraction could be represented as the sum of three cubes of fractions. Then, in the 1950s, a mathematician named Louis Mordell asked whether the same could be done for integers, or whole numbers. In other words, are there whole numbers k, x, y and z such that k = x3 + y3 + z3 for each possible value of k? It is an example of a maths riddle that is easy to state 14 | New Scientist | 14 September 2019
but fiendishly difficult to solve. Andrew Booker at the University of Bristol, UK, and Andrew Sutherland at the Massachusetts Institute of Technology have now solved the problem for 42, the only
“It is an example of a maths riddle that is easy to state but fiendishly difficult to solve” number under 100 for which a solution hadn’t been found. Some numbers have simple solutions. The number 3, for example, can be expressed as 13 + 13 + 13 and 43 + 43 + (-5)3. But solving the problem for other
numbers requires vast strings of digits and computing power. The solution for 42, which Booker and Sutherland found using an algorithm, is: 42 = (-80538738812075974)3 + 804357581458175153 + 126021232973356313. They worked with software firm Charity Engine to run the program across more than 400,000 volunteers’ idle computers, using processing power that would otherwise be wasted. It is equivalent to a single computer processor running continuously for more than 50 years, says Sutherland. Earlier this year, Booker found a sum of cubes for the number 33,
which was previously the lowest unsolved example. We know for certain that some whole numbers, such as 4, 5 and 13, can’t be expressed as the sum of three cubes. However, the problem is still unsolved for 10 numbers under 1000, the smallest of which is 114. The team will next search for another solution to the number 3. “It’s possible we’ll find it in the next few months; it’s possible it won’t be for another 100 years,” says Booker. Those interested in aiding the search can volunteer computing power through Charity Engine, says Sutherland. ❚ Donna Lu