The rotation rate of the planet Venus was first determined by measuring:
A)the time delay of radio pulses after reflection from the planet's surface.
B)the Doppler shift in radio waves reflected from the planet's surface.
C)photography from the Hubble Space Telescope at infrared wavelengths that penetrate the planet's clouds.
D)sequential photography of Venus from Earth.

Question

Quizplus · Accepted Answer

The rotation rate of Venus was first determined accurately by measuring the Doppler shift in radio waves reflected from the planet's surface. This technique allows scientists to measure the rate at which the planet rotates by observing the change in frequency of the radio waves, due to the Doppler effect, as the planet rotates.

The Rotation Rate of the Planet Venus Was First Determined