People can fall: â  from the edge of a completed roof; â  from the edge where work is being carried out; or â  through openings or gaps. Edge protection Unless the roof parapet provides equivalent safety, temporary edge protection will be required during most work on flat roofs.
Why is astronomy considered the original science? Astronomy is the oldest science for our ancients either drew or made structures according to seasons or movements of celestial bodies in our Universe.
radio astronomy.  The study of celestial objects by measurement of the radio waves they emit. Radio astronomy has enabled the detection and study of objects such as pulsars, quasars, radio galaxies, and other objects, some of which emit considerably less radiation at other wavelengths. Radio astronomy has contributed to the discovery of cosmic background radiation and has enhanced the understanding of solar activity and the structure of galaxies.