Describe how gravitational lensing works. What can it tell us about the galaxy that is doing the lensing? How is lensing valuable to the study of dark matter?
What will be an ideal response?
Gravitational lensing occurs when a nearby object (normally a galaxy) bends the light of a distant object (often a quasar), causing two or more images of the distant object to be seen. The lensing galaxy can have its mass calculated based on the amount by which it bends light. This lets us study dark matter by comparing the lensing galaxy's luminous mass with its gravitational mass.
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Sir William Herschel counted the number of stars in different directions, and getting similar numbers in each direction along the disk, concluded the Sun was near the center of a disk like collection of stars. Herschel came to the wrong conclusion about the Sun's location because
A. He did not know that interstellar dust made it hard for him to see a large part of the Milky Way's disk. B. The Sun's position in the Milky Way at that particular time was very unusual and skewed his results. C. He only counted globular clusters, and not regular stars. D. He was predisposed to believe the Sun was in the center of the Milky Way, and ignored data which disagreed with that conclusion.
The vibrational direction of an electron and the plane of polarization of the light it emits
A) are the same. B) are at right angles to each other. C) may or may not be at right angles to each other. D) are independent of each other.
What happens to the magnitude of the magnetic field inside a long solenoid if the number of turns is doubled, with the length remaining the same?
1.It becomes four times larger. 2.It becomes twice as large. 3.It is unchanged. 4.It becomes one-half as large. 5.It becomes one-fourth as large.
The terrestrial planets have mantles of ________ materials and iron rich cores
Fill in the blank(s) with correct word