The source of the infinity is easy to describe. - Lawrence M. Krauss

Now, since the time of Newton there had been a debate about whether light was a wave---that is, a traveling disturbance in some background medium---or a particle, which travels regardless of the presence of a background medium. The observation of Maxwell that electromagnetic waves must exist and that their speed was identical to that of light ended the debate: light was an electromagnetic wave.

There's a loophole if you weigh galaxies and clusters because you're weighing the total amount of energy around galaxies. What if there's energy where galaxies aren't? What is where galaxies aren't? Nothing.

But what we've discovered is that, in fact... the total energy of the universe could be zero, which is a first clue that maybe it could come from nothing. ...In physics, ...once you include gravity, there's positive energy and negative energy, and our universe appears as if its total energy could be precisely zero, which is the first hint that maybe it could come from nothing. That, and the great discovery... that namely empty space, you take a region of space, get rid of all the particles and all the radiation ...so there's nothing there. That empty space weighs something, and we don't understand why.