Why did Hubble conclude the universe must be expanding?
What will be an ideal response?
He found the universe was not static, that the most distant galaxies showed us the highest recessional velocities and redshifts. He believed this was most easily understood by having all of spacetime itself expand, taking the galaxies with it.
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What is the wavelength of a 1-hertz electromagnetic wave?
A) less than 1 m B) 1 m C) more than 1 m
The small piston of a hydraulic lift has a diameter of 8.0 cm, and its large piston has a diameter of 40 cm. The lift raises a load of 15,000 N
(a) Determine the force that must be applied to the small piston. (b) Determine the pressure applied to the fluid in the lift.
A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. When they collide and stick, the combined-glider speed is
A) 0 m/s. B) 1/2 m/s. C) 1/3 m/s. D) 1/6 m/s. E) 1.5 m/s.
The root mean square speed of a gas molecule is greater than the average speed, because the former gives a greater weight to
a. lighter molecules. b. heavier molecules. c. lower speeds. d. higher speeds. e. more probable speeds.