How much energy do we need to make an expanding universe?

[Chalnoth]

You are saying there's a few ways to calculate universe observable radius and these ways takes us different solutions.
Cause General relativity don't allow us to measure it

Sort of. Cosmologists usually mean a very specific way of writing down the distance when they say, "radius of the observable universe," but you shouldn't mistake that for an unambiguous, observed quantity.

Basically, when we start talking about things that are much, much bigger than the Earth, the definitions get weird and it becomes hard to be explicit. You can be explicit using math, but translating that to human language is difficult.

 

[Quarlep]

Volume of observable universe is increasing every time then you are telling me dark energy will be decrease.But thay cannot be true I guess (lamda doesn't change with volume)

 

[Quarlep]

Sort of. Cosmologists usually mean a very specific way of writing down the distance when they say, "radius of the observable universe," but you shouldn't mistake that for an unambiguous, observed quantity.

Basically, when we start talking about things that are much, much bigger than the Earth, the definitions get weird and it becomes hard to be explicit. You can be explicit using math, but translating that to human language is difficult.

I understand

 

[Chalnoth]

Volume of observable universe is increasing every time then you are telling me dark energy will be decrease.But thay cannot be true I guess (lamda doesn't change with volume)

The dark energy density stays roughly the same over time (if it's a cosmological constant, it stays exactly the same). So if the volume increases, that volume contains more energy from the dark energy.

 

[Quarlep]

So dark energy "energy" increase every time

 

[Chalnoth]

Essentially, yes. Energy is not conserved in General Relativity.