4. Radiation
Any particle which has the ability to travel through space in the form of a particle or as a wave comes under the purview of radiation. Radiation exists in our environment and atmosphere but it was first discovered in 1865. Radiation as we know exists in the form of radio waves, x-rays and microwaves. The discovery of radiation is important because it has shown many benefits in the medical field by way of providing radiation therapy and x-rays. Radiation has the ability to clear contaminated waste and decrease air pollution.