At the start of which eon of Earth's history do we find the earliest evidence of life?
A) Phanerozoic
B) Proterozoic
C) Archean
D) Hadean
C
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The Sun's life time is 10 billion years. About how long is the lifetime of a star with a star has a mass of 10 MSun and a luminosity of 10,000 LSun?
A) 1 million years B) 100 billion years C) 100 trillion years D) 10 million years
Two twin sisters, Gwen and Jackie, are both 20 years old in the year 2050. Suppose that Jackie makes the round-trip to Vega, which is 25 light-years away, at an average speed of 0.9999c. Which of the following correctly describes the situation when Jackie returns to Earth? (Ages in this problem refer to biological ages, that is, how much time has passed for each sister since she was born.)
A) It's the year 2100. Gwen (who stayed home) is 70 years old, but Jackie is only a little older than her age of 20 when she left. B) It's the year 2100 and both twin sisters are 70 years old. C) It's the year 2100. Gwen is 70 years old. Jackie is 19. D) According to Gwen, Jackie returns to Earth in the year 2100, but according to Jackie, she returns in the year 2051.
Cooler stars (about 3000 K) emit most of their radiation at wavelengths shorter than 600 nm.
Answer the following statement true (T) or false (F)
Gold is rare since the only time it can be formed is during a supernova
Indicate whether the statement is true or false