In principle, if we could see all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times prior to about 380,000 years after the Big Bang. Why?
A) Before that time, the universe was too crowded with stars.
B) Before that time, the gas in the universe was dense and ionized and therefore did not allow light to travel freely.
C) Before that time, the universe was dark so there was no light to illuminate anything.
D) 380,000 years after the Big Bang marks the time when stars were first born, and thus began to shine the light by which we can see the universe.
B
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Unseen objects in our galaxy have been found by the bending effect they have on more distant stars' light passing near them. These small objects that don't emit light are calculated to have masses of about 10× the mass of the Sun. Which is the best choice for these objects?
a. black hole b. neutron star c. white dwarf d. main-sequence stars
The chemical abundance of population I stars
a. indicates that they were formed before the population II stars. b. indicates that the material they formed from had been enriched with material from supernovae. c. indicates that they contain very few heavy metals compared to halo stars. d. depends on the temperature of the star. e. depends on the mass of the star.
Consider the image formed by a refracting telescope. Suppose an opaque screen is placed in front of the lower half of the objective lens. What effect will this have?
A) The top half of the image will be blacked out. B) The lower half of the image will be blacked out. C) The entire image will be blacked out, since the entire lens is needed to form an image. D) The image will appear as it would if the objective were not blocked, but it will be dimmer. E) There will be no noticeable difference in the appearance of the image with the objective partially blocked or not.
Rotational Dynamics: A force of 16.88 N is applied tangentially to a wheel of radius 0.340 m and causes an angular acceleration of 1.20 rad/s2. What is the moment of inertia of the wheel?
A. 4.78 kg ? m2 B. 3.59 kg ? m2 C. 5.98 kg ? m2 D. 7.17 kg ? m2