Who was Henrietta Leavitt, and what did she do to help map the universe?
What will be an ideal response?
This Harvard astronomer found the period-luminosity relationship for the Cepheid variables from her work on the Large Magellanic Cloud. The discovery of these "cosmic yardsticks" allowed Shapley to map the home Galaxy, and other astronomers to use these stars in finding distances to many galaxies beyond us.
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Which of the following caused the Moon to show (nearly) the same face to the Earth at all times?
A) tidal friction B) spring tides C) conservation of energy D) atmospheric drag E) gravitational encounters
The ground rises and sinks regularly because of tidal effects
Indicate whether the statement is true or false
An object is placed 15 cm from a spherical concave mirror with a focal length of magnitude 20 cm. If the object is 4.0 cm tall, how tall is the image?
A) 1.0 cm B) 2.0 cm C) 8.0 cm D) 16 cm
A 4.0-?C charge is situated at the origin of an xy-coordinate system. What is the magnitude and direction of the electric potential at x = 6.0 m?
A) 1500 V along the +x-axis B) 4000 V along the +x-axis C) 4000 V with no direction, as it is a scalar quantity D) 6000 V along the +x-axis E) 6000 V with no direction, as it is a scalar quantity