# Amount of dark Energy at different times

1. Dec 17, 2015

### 69911e

I am wondering what the formula would be for the amount of Dark Energy in the observable universe would be for different time (t). (according to best current theory/data)

Would it be this directly proportional to volume?
Dark energy (t) = Dark energy (present time)/ (scale factor (t)3)

If so, 6GY ago scale factor = 1.618 therefore Dark Energy would be about 1/4 the current amount.

I could be way off as I am just starting on this stuff.

Last edited: Dec 17, 2015
2. Dec 17, 2015

### Chalnoth

I don't think that the amount of dark energy is a useful quantity (total energy is not well-defined in General Relativity). The density, however, is useful, and can be thought of as a constant (if it does change over time, those changes haven't yet been detected).

3. Dec 17, 2015

### Jorrie

Apart from what Chalnoth said about the usefulness of total energy, the radius of the observable universe does not scale directly with scale factor a. You mentioned a=1.618, which is in the future, so I guess you intended to say a=0.618, which correlates with 6 Gy ago.
The radius of the observable universe was then about half of what it is today ( D_particle ~ 23 Gly then, according to LightCone 7) and the total vacuum energy in the observable universe about one eighth of today (at constant density).

4. Dec 18, 2015

### 69911e

Jorrie: That clarifies what I was looking to understand. I also was not using scale factor term correctly.
Thanks