Within the last two and a half billion years, how many snowball Earth events have occurred?
A) zero
B) one
C) two
D) four
C
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Time Dilation: Astronaut Rachel leaves Earth in a spaceship at a speed of 0.960c relative to an observer on Earth. Rachel's destination is a star system 14.4 light-years away (one light-year is the distance light travels in one year). According to Rachel, how long does the trip take?
A. 14 years B. 15 years C. 11 years D. 4.2 years E. 23 years
Why can't we see past the cosmological horizon?
A) Every galaxy in the entire universe (not just the observable universe) exists within the cosmological horizon, so there's nothing to see beyond it. B) It's impossible to look back to a time before the universe was born. C) We do not have telescopes big enough. D) The cosmological horizon is infinitely far away, and we can't see to infinity.
The atmosphere of Saturn is composed mostly of
A) methane and ammonia. B) carbon dioxide and ethane. C) hydrogen and helium. D) hydrogen sulfide and ammonia. E) nitrogen and oxygen.
The current atmospheric concentration of carbon dioxide on Earth is at its highest in over a million years
Indicate whether the statement is true or false