How does a vacuum have energy if it has no mass ?

[crawler]

How can it be said there is no energy in a vacuum when all the electromagnetic spectrum traverses vacuum throughout the universe.

Well... there's no such thing as a vacuum in the religious sense it is often invoked with.

Space has a lot of radiation that is not matter or mass in the ordinary sense.

And space has a lot of something that tells us that space is near mass/matter. What is that something?
it us what i have called Photaeno(s). Emitted by all photons, ie emitted by matter & light.
Strictly speaking we karnt tell how far any one photaeno is from its source.
What must be happening is that photaenos are denser per cubic metre near matter.
But, the Olbers' Paradox strikes at this level too, ie every cubic metre should be saturated/full of photaenos (& photons).
The solution to both OPs is that photons die eventually, & photaenos too die eventually.

Anyhow, every cubic metre of space has a lot of (1) photons & (2) photaenos (ie energy) in addition to (3) matter.
And every cubic metre of space contains (4) gravity energy & (5) magnetic energy & (6) charge energy.
I dont think that i can add (7) radio energy, koz radio is a part of (5).

[mariuslvasile]

How can it be said there is no energy in a vacuum when all the electromagnetic spectrum traverses vacuum throughout the universe.

That is obviously not the energy of vacuum, it is the energy emmited by stars in a vacuum. If you have a fully isolated vacuum like in a lab there is no EM wave emmited by the vaccum. Because a vacuum has no intrinsic energy. Quantum pseudo-scientists try to use the Kasimir effect to support their Quantum Fart Theory (QFT), but that effect is clearly caused by electrostatic forces (Van der Waals).
These quantum bozos are complete FRAUDS and someone should sue them for this. And for the Vacuum Catastrophy, which is the worst prediction in the history of physics. You can't take millions in funds to make a prediction that is 52 orders of magnitude wrong, unless you're a complete fraud and/or catastrophically stupid. Now they try to present this astronomical error as a 'great mistery of the universe', and they try to solve it. Sure, give them some other millions, so that they can invent some dark unicorns which absorb 10^52 of the excess dark vacuum energy, vacuum dark energy being zero, lie that some experiment which has nothing to do with it proves their quantum unicorns, and problem is solved !