What is the saros cycle?
A) the 26,000-year cycle of the Earth's precession
B) the roughly 18-year cycle over which the pattern of eclipses repeats
C) the roughly one-month cycle of lunar phases in the sky
D) the annual cycle of the seasons
Question 2
Recent measurements of the expansion rate of the universe reveal that the expansion rate of the universe is doing something astronomers did not expect. What is that?
A) The measurements show that the universe may not be expanding at all.
B) The measurements show that the universe may be shrinking rather than expanding.
C) The measurements show that the expansion is accelerating, rather than slowing under the influence of gravity.
D) The measurements indicate that the universe is at least 30 billion years old, meaning that more than 10 billion years passed between the Big Bang and the formation of the first stars and galaxies.
E) The data show that the expansion rate varies widely in different parts of the universe.
Changes in Earth's atmospheric carbon dioxide levels over geological time.
Schematic of the Earth–Moon system (without a consistent scale)
The hydrologic cycle "الدورة الهيدرولوجية"
Earth’s Biomes "الأرض الحيوية"
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Earth 240 Million Years Ago