Describe some of the early theories for the Sun's energy source and why they are no longer accepted as viable
What will be an ideal response?
One early idea was that the Sun shone through chemical burning (like a conventional fire on Earth), but this was discounted when the huge energy output of the Sun was first estimated. A popular hypothesis suggested in the late 1800s was that the Sun shone through the emission of thermal energy resulting from gravitational contraction. While the Sun was required to contract only slightly each year to maintain its temperature, this contraction could only last for about 25 million years, far less than the estimated age of the Earth at that time.
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Suppose a ball is thrown straight up, reaches a maximum height, then falls to its initial height. Make a statement about the direction of the velocity and acceleration as the ball is going up
A) Both its velocity and its acceleration point upward. B) Its velocity points upward and its acceleration points downward. C) Its velocity points downward and its acceleration points upward. D) Both its velocity and its acceleration points downward. E) Neither velocity nor acceleration can be determined without additional information.
Listed following are some distinguishing characteristics of comets, meteors, and asteroids. Match these to the appropriate category of objects.
What will be an ideal response?
How many electrons are gained or lost in the following half-reaction?
2 Na ? 2 Na+ A) 2 electrons are lost B) 1/2 electron is gained C) 1/2 electron is lost D) 2 electrons are gained E) 4 electrons are gained
We can study how galaxies evolve because ________
A) galaxies are transparent to visible light B) we can watch as they interact in real time C) the farther away we look, the further back in time we see D) we are really smart astronomers