Hubble Relationship?

Question

State the hubble relationship in words and quantify numerically what it says about the speed of reccession of distant galaxies?
Include a definition of 1 unit parsec.

Also What does the Hubble relationship tells us about the universe and what it implies about the density of the universe in the distant future?

Answer 1

In the 1920's Hubble investigated the relation between distance to galaxies and their velocity toward or away from us. He found (as had been noted earlier) that most galaxies are moving away from us.
In a paper ppublished in 1929, Hubble reported a relation between distance and velocity, now known as the Hubble law.

The parsec (symbol pc) is a unit of length used in astronomy. The length of the parsec is based on the method of trigonometric parallax, one of the oldest methods for measuring the distances to stars.

The name parsec stands for "parallax of one second of arc", and one parsec is defined to be the distance from the Earth to a star that has a parallax of 1 arcsecond.

Definition:A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond.

Source: http://en.wikipedia.org/wiki/Parsec

Answer 2

Hubble's law states that the redshift in light coming from distant galaxies is proportional to their distance. The proportionality factor is called the Hubble Constant and it is 71 (km/s)/Mpc, where Mpc is mega parsecs or million parsecs. A parsec is a unit of distance that is equal to 206,265 times the distance from the Earth to the Sun, and the distance from the Earth to the Sun is 93 million miles or 150 million kilometers.