Why do telescopes give modern astronomers an advantage over people in the past

If you have 200.0 g of radioisotope with a halflife of 5 days, how much isotope would remain after 15 days?

A 120VAC electric heater has two resistive heating elements that can be switched separately in and out, in series or parallel. Find the values of the two resistors if the minimum power drawn by the heater is 300 watts and the maximum is 1200 watts.

In a research facility, a person lies on a horizontal platform which floats on a film of air. When the person's heart beats, it pushes a mass m of blood into the aorta with speed v, and the body and platform move in the opposite direction with speed

Speed of a radio wave in air

As long as an object is not gaining or losing mass, a net force on the object will cause a change in

Three light bulbs are wired in series. What happens if one of these light bulbs burn out

How do you distinguish a pure substance from a mixture?

Does the size of the particles change as the substance changes state?

What is the Z number of an atom with 9 protons, 8 neutrons, and 7 electrons? 7 8 9 16 17

What is the most dense crust