Because we know that the half-lives of many radioactive isotopes are millions of years, we can deduce that
a. the longer it exists the more radioactive nuclei Earth produces.
b. the sun is the source of all the radioactive nuclei on Earth.
c. there must have been many more radioactive nuclei on Earth when life began.
d. there must have been far fewer radioactive nuclei on Earth before life began.
e. the natural radioactivity of minerals on the Earth was created by the Earth's internal temperature.
c
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Why do models suggest that Uranus and Neptune formed elsewhere?
A) We do not have very good models. B) The density of materials was too low in their current orbits for the ice giants to have formed there. C) Jupiter and Saturn took up most of the material in the area; Uranus and Neptune must have formed elsewhere. D) It is too cold at their current locations for the ice giants to have formed there.
A uniform electric field, with a magnitude of 600 N/C, is directed parallel to the positive x axis. If the potential at x = 4.0 m is 1000 V, what is the change in potential energy of a proton as it moves from x = 4.0 m to x = 1.0 m? (qp = 1.6 × 10^-19 C)
a. 500 J c. 1.9 × 10^-16 J b. 2.9 × 10^-16 J d. 8.0 × 10^-17 J
When pore spaces become completely filled with water, the soil is considered to be at
What will be an ideal response?
Suppose it turns out that one in 1 million stars has a planet that at some point in its history is home to an advanced civilization. Then the total number of civilizations that have arisen in our galaxy would be closest to ________
A) 40,000 B) 400,000 C) 40 D) 4,000 E) 400