True
Variables is changing. It is any factor, trait or condition that can exist in differing amounts or types. An experiment has three types: Independent, Dependent and Controlled.
Answer:
<u>Over the last century, the average surface temperature of the Earth has increased by about 1.0o F.</u>
Explanation:
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Answer: D. Infrared
Infrared is the best way to observe it.
Answer:
First, as you may know, the light travels at a given velocity.
In vaccum, this velocity is c = 3x10^8 m/s.
And we know that:
distance = velocity*time
Now, if some object (like a star ) is really far away, the light that comes from that star may take years to reach the Earth.
This means that the images that the astronomers see today, actually happened years and years ago (So the night sky is like a picture of the "past" of the universe)
Also, for example, if an astronomer sees some particular thing, he can apply a model (a "simplification" of some phenomena that is used to simplify it an explain it) and with the model, the scientist can infer the information of the given thing some time before it was seen.