The Unit of Dark Energy: g/cm3?

Reply Fri 26 Aug, 2016 10:38 pm
Today, Scientific American reports:
This Weird Galaxy Is 99.99 Percent Dark Matter

Usually, we use kg or g to describe matter, be it ordinary or dark, and we also use joules or ergs to describe energy.

Well, as I checked out Dark Matter and Dark Energy in Wiki, I found it says:
Again, on a mass–energy equivalence basis, the density of dark energy (~ 7 × 10−30 g/cm3) is very low, much less than the density of ordinary matter or dark matter within galaxies.

What? It has used g/cm3 to directly describe dark energy. Although Einstein's equation E=mc2 offers energy-mass converting relationship, the use of g as the unit of energy is new to me.

My question is: is g used properly here? Does it stand for gram?

Thanks in anticipation
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Reply Sat 27 Aug, 2016 12:26 am
the density of dark energy (~ 7 × 10−30 g/cm3) Read g as grammes and cm as centimetre, and cm3 as "cubic centimetre". No superscripts possible on here.

The density of dark energy (approximately seven times ten to the minus 30th power grammes per cubic centimetre).

weight per unit of volume.


Reply Sat 27 Aug, 2016 01:00 am
contrex wrote:
weight per unit of volume.

Sorry, that's mass per unit volume (of course).
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