According to observations, what type of galaxy was much more common when the universe was 2 billion years old?
A) elliptical galaxies
B) spiral galaxies
C) irregular galaxies
D) We can't say, because we are living at a time when the universe is 14 billion years old, not 2 billion years.
C
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Single-Slit Diffraction: The figure shows the resulting pattern when a single slit is illuminated by monochromatic light. The slit is 0.3 × 10-3 m wide and is illuminated by light of wavelength 506 nm. A diffraction pattern is seen on a screen 2.8 m from the slit. What is the linear distance on the screen between the first two diffraction minima on either side of the central diffraction maximum?
Fill in the blank(s) with the appropriate word(s).
An elastomeric bearing pad is subjected to a shear force V during a static loading test. The pad has dimensions a 5 150 mm and b 5 225 mm, and thickness t 5 55 mm. The lateral displacement of the top plate with respect to the bottom plate is 14 mm under a load P 5 16 kN. The shear modulus of elasticity G of the elastomer is approximately:
(A) 1.0 MPa
(B) 1.5 MPa
(C) 1.7 MPa
(D) 1.9 MPa
During the eighteenth and nineteenth centuries, attempts to precisely measure the astronomical unit relied largely on rare
A) total solar eclipses. B) transits of the inferior planets across the Sun. C) passages of comets close to the Earth. D) maximum elongations of Venus. E) oppositions of Mars.
The main constituent of the Martian atmosphere is
A) methane. B) helium. C) carbon dioxide. D) hydrogen. E) nitrogen.