According to the Cosmological principle, the Universe is isotropic, homogeneous and the laws of physics are universal. State what is meant by the term homogeneous.
Astronomers often analyze absorption spectral lines in the light from distant galaxies to determine their recessional velocities. The wavelength of a specific absorption spectral line measured in a laboratory on Earth is 550 nm550\text{ nm}550 nm.
A distant galaxy, NGC 1277, is located at a distance of 150 Mpc150\text{ Mpc}150 Mpc from Earth and is known to host an extremely massive black hole at its core.
Calculate, in nm\text{nm}nm, the wavelength λ\lambdaλ of this absorption line when observed in the spectrum of NGC 1277. Assume the Hubble constant is 68 km s−1 Mpc−168\text{ km s}^{-1}\text{ Mpc}^{-1}68 km s−1 Mpc−1 and the speed of light in a vacuum is 3.00×108 m s−13.00 \times 10^8\text{ m s}^{-1}3.00×108 m s−1.
Define the term event horizon of a black hole.
