If the earth’s crust contained twice as much iron as it does, would atmospheric oxygen buildup have been slowed down or sped up during the past 2.5 billion years?
what would the consequence of this have been for the evolution of aerobic respiration, the ozone layer, green plants, and animals?

True or false graphs must include scales that increase by the same amount

Light traveling in water, nwater = 1.33, strikes a plastic block at an angle of incidence of 51.4°; part of the beam is reflected and part is refracted. if the index of refraction of the plastic is 2.0, what is the angle made by the reflected and refracted beams?

Currents in dc transmission lines can be 100 a or higher. some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. for a line that has current 150 a and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? express your answer in teslas and as a percentage of the earth’s magnetic field, which is 0.50 g. is this value cause for worry?