GENEVA, June 2 (Xinhua) -- The official ball for the 2018 World Cup in Russia has been approved after a series of rigorous Swiss scientific tests, standing out as a perfect example of material and applied physics, according to the Swiss Federal Laboratories for Materials Science and Technology (EMPA) on Saturday.
EMPA has been testing footballs for FIFA for 22 years, and not every ball passes the test. Although some goalkeepers had been critical of the ball's flight characteristics, the Adidas "Telstar 18" has now got the seal of approval.
According to EMPA, it's not only the circumference and weight of the ball that are measured precisely. Despite being crushed 250 times in a water tank, the ball may only absorb a minimal amount of liquid, and must be able to hold its air and always jump off at the same height when it impacts from a height of two meters.
To prove that the ball is a perfect sphere, it's also measured at no less than 4,000 points. And finally, the ball must retain its shape even if shot against a steel wall 2,000 times at 50 km per hour.
The tests were specially developed by EMPA experts in St. Gallen for official tournament footballs.
Some goalkeepers of various World Cup teams who have already been allowed to test the ball have complained that the ball "flutters."
It's precisely the surface that is responsible for the unpredictable flight of the ball. Researchers said optics also come into play. Telstar 18 is not made up of the traditional hexagons and pentagons, but of irregular elements with asymmetrical prints. Thus the flying ball can be quite an unusual sight under some lighting conditions.
Professional players can take advantage of the fact that a football's trajectory is complex and, according to the theory of aerodynamics, sometimes chaotic.
Unlike a streamlined projectile that describes a perfect parabola, the ball deforms, for example when the player kicks it. Experienced players take advantage of this effect and "bend it like Beckham." This is not actually a matter of magic, but of applied physics, according to the researchers.