Why do astronomers think that the milky way is a spiral galaxy?

The integral design hub incorporates thento the bearing unit. n a. cv joint n b. mounting carrier n c. brake rotor n d tie rod end

Amichelson interferometer operating at a 600 nm wavelength has a 3.02-cm-long glass cell in one arm. to begin, the air is pumped out of the cell and mirror m2 is adjusted to produce a bright spot at the center of the interference pattern. then a valve is opened and air is slowly admitted into the cell. the index of refraction of air at 1.00 atm pressure is 1.00028.how many bright-dark-bright fringe shifts are observed as the cell fills with air?

What is the single most important equation in all of physics?