- #1

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H

_{0}= 72 km/s/Mpc

but i've started seeing it expressed as:

H

_{0}= 100 h

_{100}km/s/Mpc.

what is h

_{100}and why is it coming up in this??

I've also seen the critical density for the shape of the universe (flat/open/closed ect) as:

Rho

_{c}= 1.879 h

_{100}

^{2}kg/m

^{3}

what does it mean in this context, and as the critical density is given by:

Rho

_{c}= 3 H

_{0}

^{2}/8 pi G

i don't see where you get the 1.879 from even if you do replace the Hubble constant with the above.

i'm really confused, so could some one please help???