Answer:
The average luminance of the Sun is about 1.88 giga candela per square metre, but as viewed through Earth's atmosphere, this is lowered to about 1.44 Gcd/m2. However, the luminance is not constant across the disk of the Sun (limb darkening).
Explanation:
<span>Factors contributing to the west ward expansion of the United States include the discovery of gold, the Homestead Act, and the desire for adventure, land and riches. The answers are the third, fourth and fifth statements among the choices that you have included or posted.</span>
