It is nearly identical to our own planet and bulk properties such as mass, density, and size.

它和我们的星球以及很多其他的特征，比如说质量、密度和体积基本是一样的。

And we so far have no idea why our universe has the mass energy density it does.

到目前为止，我们还不知道为什么我们的宇宙有着恰到好处的质量能量密度。

It is nearly identical to our own planet in bulk properties such as mass, density, and size.

它在质量、密度和大小等体积性质上几乎与地球相同。