Using simple materials like plastic bottles, straws, modelling clay, and syringes you can witness many interesting phenomena relating to air and water pressure.
When a material gets wet, we see it with a darker colour. Professor Inmaculada Pascual Villalobos explains why.
Between 1925 and 1975, the Sahara desert grew, especially southward, about 645,000 km2, and in some parts of Sudan, the southern boundary of the desert moved 310,000 km2 between 1958 and 1975. This development was most important in the sixties and