Answer:
The sidebar tells us what Earth scientists are actually doing about the risk of an asteroid impact.
Explanation:
The main part of the page discusses how frequently the moon is hit by rocks; how most rocks are too small to make it past Earth's atmosphere; how the rocks that do make it all the way to Earth's surface are usually pretty small and don't hit anything important; how screwed we would be if a massive rock – like an asteroid – made it to Earth's surface.
The sidebar says that scientists are understandably worried enough about these asteroids – they "feel the danger is to great to ignore" – so they're keeping a lookout for asteroids that might be on a collision course with Earth.
It is important to have a primary source and a secondary source because it allows you to set up the writing and add information to support or disagree with the topic. If you were reading two books and you were planning on comparing/contrasting them using a specific topic, those two books would be your primary sources. The primary sources are the bulk of the writing while the secondary sources add on in support with your argument. Secondary sources would be source outside of your primary sources (Internet, magazines, newspapers, etc). Primary source is the main source. Secondary source is the source outside of your main source. Secondary sources are usually used to give your paper more factual evidence or things of that source.
The electromagnetic spectrum<span> is a continuum of all</span>electromagnetic waves<span> arranged according to frequency and wavelength. The sun, earth, and other bodies radiate </span>electromagnetic<span> energy of varying wavelengths. </span>Electromagnetic<span> energy passes through space at the speed of light in the form of sinusoidal</span>waves<span>.</span>
