Surface tension can push particles up falling water

Science News : The phenomenon was first noticed in 2008 when Sebastian Bianchini, a student at the University of Havana, Cuba, was making mate tea . As he poured hot water from a pitcher into a cup of tea leaves, he found that some of the tea leaves ended up in the pitcher. Bianchini ran some experiments with Ernesto Altshuler, a professor at the university, but they never published their findings because of skepticism from other physicists. Altshuler recently performed similar experiments with Troy Shinbrot of Rutgers University in New Jersey. When water was poured from a container placed 1 cm above a container of mate and chalk, the researchers found that the particles in the second container did indeed flow up the downward pouring water into the higher container. They concluded that their explanation matched Bianchini and Altshuler’s original finding—the particles disrupt the surface tension of the water and get pushed upward to water with higher surface tension. That surface tension pushes particles to areas of the highest tension is a known characteristic of water, but this experiment is the first to show that the effect is strong enough to push particles upward against gravity.