Soccer World Cup
Bend it like Einstein: the science behind the 2018 Soccer World Cup ball
With just about every World Cup, there seems to be grumbling about the ball, which adidas has designed for the four-yearly FIFA tournament since 1970.
Already, this year's offering, Telstar 18, has been criticised by some goalkeepers for being too flighty and hard to grip.
But scientists say the new sphere is actually quite stable - certainly more so than Jabulani, the much-denigrated official ball for the 2010 World Cup in South Africa.
The Telstar 18 is a nostalgic nod to Adidas' first-ever World Cup ball, the Telstar, used in Mexico for the 1970 World Cup.
That was the first black-and white sphere made for a World Cup - designed for better visibility on monochrome TV screens - and sported the mix of pentagonal and hexagonal panels that has become synonymous with soccer balls.
The latest offering is white, black and grey with gold lettering.
Eric Goff, a physics professor at the University of Lynchburg in Virginia, was part of a team that analysed the ball using wind-tunnel experiments and surface measurements.
Compared to the Brazuca, its predecessor used in Brazil in 2014, the Telstar 18 experiences more "drag" or resistance as it flies through the air, the researchers found.
The Telstar 18 will travel shorter distances when kicked at high impact speeds of more than 90km/h ... that could be bad for strikersEric Goff, physics professor
This means it will travel shorter distances -about eight to 10% less than Brazuca - when kicked at high impact speeds of more than 90 kilometres per hour, Goff said
"That could be bad for strikers who kick from a great distance and must therefore kick the ball very hard," he explained.
But potentially good news for goalies, as it means balls kicked at high speed "will reach the goal a little slower than Brazuca did in 2014."
Like Brazuca, Telstar 18 has six panels, compared to Jabulani's eight - far fewer than the traditional 32-panel recipe long followed.
But Telstar 18's panels are shaped differently, and the seam that holds them together is 30% longer in total than Brazuca's, though also narrower and more shallow.
Sungchan Hong of the University of Tsukuba's sports science faculty in Japan, said kicking robot tests revealed the Telstar 18 has "a very stable trajectory compared to the previous balls".
"In other words, it is expected that a set-piece situation such as a free kick or corner kick, or an intermediate-range strong shot, may be effective," he said
"I don't think there will be as many irregular moves" as with Jabulani, added Hong. "I don't think there will be any disadvantage to the goalkeeper."
Compared to Jabulani, the Telstar 18 should display much less of the "knuckleball" effect that makes balls launched with no surface spin start zig-zagging wildly in flight.