What were the two critical brightness measurements Hubble compared to solve the final distance to V1 using the inverse square law?
Answer
Absolute magnitude and apparent magnitude
The final calculation that determined the distance relied on comparing what the star's brightness should be versus what it appeared to be from Earth. The star's *absolute magnitude* (its true, intrinsic brightness) was derived indirectly from its pulsation period using Leavitt's Law. The *apparent magnitude* was its observed brightness as measured through the 100-inch Hooker Telescope. The inverse square law of light then directly links the ratio between the absolute brightness (how bright it is) and the apparent brightness (how bright it looks) to the square of the distance separating the two points.
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