Author Question: What is the difference between homogeneity and isotropy? What will be an ideal ... (Read 21 times)

jhjkgdfhk · **on:** Jul 27, 2018

What is the difference between homogeneity and isotropy?

What will be an ideal response?

Question 2

How is Olbers's paradox explained?

What will be an ideal response?

sarah_brady415 · **Reply #1 on:** Jul 27, 2018

Answer to Question 1

Think of a dart board. Isotropy is radial lines radiating outward from the center, but a radial line does not have to be constant along that line. However, every radial line must change by the same amount along the radial line. Homogeneous is angular so think the rings of the dart board. Adjacent rings of the dart board can be different but the space within each ring has to be the same.

Answer to Question 2

The Universe may be infinite in size, but it is neither infinitely old nor static. The essence of modern cosmologists' answer to Olbers's question was suggested first by Edgar Allan Poe in 1848 . Poe proposed that the night sky is dark because the Universe is not infinitely old but came into existence at some finite time in the past. The more distant stars are so far away that light from them has not yet reached Earth. That is, if you look far enough away, the look-back time approaches the age of the Universe, and you see to a time before the first stars began to shine. The night sky is dark because the Universe had a beginning.