Which correctly identifies the distribution of elements in the universe?
a. the universe is 70% hydrogen and 2% heavy elements.
b. the universe is 80% hydrogen and 9% oxygen.
c. the universe is 90% heavy elements and 4% hydrogen.
d. the universe is 95% heavy elements and 2% oxygen.?

The sun’s mass is 2.0×10^ 30 kg, its radius is 7.0×10 5 km, and it has a rotational period of approximately 28 days. if the sun should collapse into a white dwarf of radius 3.5×10 3 km, what would its period be if no mass were ejected and a sphere of uniform density can model the sun both before and after?

What would be the strength of earth's gravitational field at a point where an 80.0 kg astronaut would experience a 80% reduction in weight

What is the increase in density of a medium due to wave travel?