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。

If you listened carefully, you learned the difference between the net velocity of a gas and the average velocity of its particles, and that both things have a lot to do with the mass and kinetic energy of the particles.

如果你仔细听，你就会了解到气体的净速度与其粒子的平均速度之间的差异， 并且这两者都与粒子的质量和动能有很大关系。