Units

The ‘units’ parameter category contains parameters specifying the unit system used by CONCEPT. This system of units is used both internally and for output.

`unit_length`

	Description		Specifies the base length unit to use
	Default		'Mpc'
	Elaboration		Internally, all dimensional values (be it lengths or otherwise) are represented as bare floating-point numbers. The number `1.0` then corresponds to some length. This length is what this parameter specifies.
	Example 0		Use kiloparsec as the base length unit: unit_length = 'kpc' Caution Note that unlike when using units when defining other parameters, here `'kpc'` is used as a `str`. This is because here we want the symbolic meaning of a ‘kiloparsec’, whereas in other places what we are after is its numeric value (which really is not defined prior to specifying `unit_length`).
	Example 1		Many other codes make use of units like \(\text{Mpc}/h\) or \(\text{kpc}/h\), where \(h \equiv H_0/(100\, \text{km}\, \text{s}^{-1}\, \text{Mpc}^{-1})\) and \(H_0\) is the Hubble constant. Specifying simply `'Mpc/h'` as `unit_length` will not work however, since `h` itself can only be inferred from `H0` once the numeric value of `Mpc` has been established, which itself depends on `unit_length`. To bypass this issue, we can use unit_length = 'Mpc/0.67' given that `h = 0.67`, corresponding to `H0 = 67km/(sMpc)`.

`unit_time`

	Description		Specifies the base time unit to use
	Default		'Gyr'
	Elaboration		Internally, all dimensional values (be it times or otherwise) are represented as bare floating-point numbers. The number `1.0` then corresponds to some time. This time is what this parameter specifies.
	Example 0		Use seconds as the base time unit: unit_time = 's'
	Example 1		Use the same base time unit as is (implicitly) used in CLASS: unit_time = 'Mpc/c'

`unit_mass`

	Description		Specifies the base mass unit to use
	Default		'10¹⁰ m☉'
	Elaboration		Internally, all dimensional values (be it masses or otherwise) are represented as bare floating-point numbers. The number `1.0` then corresponds to some mass. This mass is what this parameter specifies.
	Example 0		Use the same base mass unit as is (implicitly) used in CLASS (at least in the background module): unit_mass = '3/(8 π G) c² Mpc' Note In specifying the symbolic unit, we are allowed to be fancy as above. We could equivalently use e.g. unit_mass = '119366.2073189215light_speed2pc/G_Newton'