this week's question comes from severe of deraa in columbia. why do animal horns vary so greatly. some a small. others big. big maybe cuddly point upwards or downwards. but even though they look very different they all have. the same structure the bony core of the horn protrudes from the skull. then comes the sheath which is usually hollow and made of keratin similar to hair feathers fingernails and hooves. but not all animals with horns come from the same family rhinos are what's known as an odd angle it as they have 3 toes and they're the only ones in that family to have horns. other group is the brother die family they're even told and you let's which nearly all have horns they include cattle sheep and goats but also antelopes and gazelles. by contrast mussa and deer don't have horns they have antlers which are bony structures. elephant tusks by the way are neither horns nor employers but actually teeth are made of dental. but what's the purpose of hormones. in all cases they're sharp weapons to fend off enemies. but perhaps their most important function is to impress the males

can count deraa is one of the founding fathers of geo engineering shortly after the new millennium began he carried out the 1st simulations of solar geo engineering he demonstrated that it was possible to limit global warming simply by diffusing the sunlight some parts of the earth's system like the coral reefs. are facing. tension collapse within 20 or 30 years maybe we want to have emergency options then these kinds of options are the only thing that are known to work that quickly and in marine corps breaking you could break clouds over 20 percent of the clouds of the ocean maybe 3 or 4 percent of the ocean's surface and possibly cool the entire planet by 2 degrees. influencing the reflectivity of marine clouds to make them brighter was one of the 6 solutions chosen by the australian government in 2018 to save the great barrier reef already showing the effects of global warming. in the u.s. researches for the marine cloud brightening project have developed a floating offshore device to enhance the reflectivity of ocean clouds. clouds cover about 2 thirds of the earth's surface so anyth