Hubble did not believe the redshift represented expansion. He called it "an hitherto unknown principle of nature". He is right, it is an unknown principle. It comes form the conservation of energy when Newton';s Law of gravity is updated with the energy of moving masses. E= -mu/R + mcv; mcv is the vector energy associated with gravity. This introduces the sum of a real energy and a vector energy which is a quaternion energy. As some may know quaternions represent a non-commutative mathematics. Quaternions are the ideal mathematics for four dimensional space-time. Using quaternions the mystery of the redshift is resolved.

The redshift is the solution of the equilibrium between the gravitational centripetal (center seeking) and the centrifugal (center fleeing) accelerations or forces. The centrifugal forces are the so-called "dark energy". There is no dark energy, it is the moving masses giving the redshift and balancing the gravity. Einstein called in the cosmological constant to combat gravitational collapse. The cosmological constant is the centrifugal forces of moving matter.

Hubble's relation that the farther away the greater the redshift is true. it is the reult of the further towards the boundary of the universe the greater the mass projection at center and the greater the redshift. At the boundary of the universe the redshift is 1 and the speed is at the speed of light.

The reshift formula is mg=mcDel.v ; v^2.R = cV/R cos rv thus
cos rv=v/c=z=sqrt(GM/Rc^2).

A test of this theory would be Einstein's deflection of light. There should be a redshift of light glancing the sun is 89 degrees 54' 59.93''. This is a deflection of 5' 0.07" ( five arcminutes and 0.07 arcseconds) shift away from the sun, not towards the sun.

The redshift is key to understanding the universe but it is mis-understood. It is z=v/c=cos rv = sqrt(GM/c^2R) = sqrt(GP/c^5) where c^5/G is power of the universe. Thus z^2 = GP/C^5 or P=z^2(c^5/G) the redshift measure is a measure of power and the redshift measure is a measure of the proximity to the boundary of the universe; z=v/c =r/R= cos rv, where R = radius of universe, R is approximately 158E24meters.