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What does Hubble's constant represent?

Answer 1

It represents the ratio between the recessional velocity of a galaxy (#km# #s^-1#) and the distance to the galaxy (#"Mpc"#), #km# #s^-1# #Mpc^-1#, or sometimes converted to #s^-1#. When given in terms of #s^-1#, #1/H_0="approximate age of the universe"#

Based on observations, we know that #vproptod# with #v# being recessional velocity(#km# #s^-1#) and #d# being distance #(#Mpc#)

A graph of #v# against #d# produces a rough straight line with gradient #H_0#, using this we can work out the recessional velocity or distance to a galaxy given the other.

#"time"="distance"/"velocity"=1/H_0#

When #H_0# is given as #s^-1# the reciprocal can give the approximate age of the universe.

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Answer 2

John Alexander

Hubble's constant is a measure of the expansion rate of the universe and the velocity at which galaxies are accelerating away from one another.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.