Why do we believe there is dark matter?
What will be an ideal response?
When we use the Keplerian equation to determine the mass of the Galaxy, we find a value of 100 billion Suns inside the Sun's orbital radius, or about 200 billion Suns all the way out to the end of the visible part of the spiral arms and halo stars. However, when we look the rotation curve, we find objects distant from the center rotating much faster than expected. To account for this, significantly more mass must exist outside the visible portion of our galaxy that we cannot see.
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The fundamental force that binds the electrons to the nuclei to form atoms is
A. strong force. B. weak force. C. electromagnetic force. D. gravitational force.
What is an indication that a planetary moon may have been captured?
A) it revolves in retrograde direction, opposite to the direction of planetary spin B) it has a highly elliptical orbit C) it has an orbit which is inclined to the equator of the host planet D) all of these are indications
When the equation Al + O2? Al2O3 is balanced, the coefficient of O2 is
a. 1 b. 2 c. 3 d. 4
How far must one travel to escape Earth's gravitational field?
A) to a region above Earth's atmosphere B) to a region well beyond the Moon C) to a region beyond the solar system D) forget it; you can't travel far enough.