What causes stars to twinkle?
A) It is intrinsic to the stars—their brightness varies as they expand and contract.
B) variations in the absorption of the atmosphere
C) variable absorption by interstellar gas along the line of sight to the star
D) bending of light rays by turbulent layers in the atmosphere
E) the inability of the human eye to see faint objects
D
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Kepler's ________ law states that the orbits of planets are elliptical, with the Sun at one focus.
A. First B. Second C. Third D. Fourth
A block of metal weighs 40 N in air and 30 N in water. What is the buoyant force that the water exerts on the block? The density of water is 1000 kg/m3
A) 10 N B) 30 N C) 40 N D) 70 N
An ancient building was known to have been built 3 000 years ago. Approximately what proportion of Carbon-14 atoms are yet in the building's wooden framing compared to the number which were present at the time of its construction? (half life of 14C = 5 730 years)
a. 0.425 b. 0.500 c. 0.517 d. 0.696
The Hubble Space Telescope only detects visible light.
Answer the following statement true (T) or false (F)