The World According to Physics

by Jim Al-Khalili

So to say that the quantum vacuum of empty space has zero energy would be the same as claiming a calm ocean has no depth. The equivalent of water beneath the ocean surface is t...

However, having a mathematical symbol for dark energy does not mean we entirely u...

Astronomical measurements suggest that the cosmological constant has a certain numerical value, but, like the mass of the Higgs boson in the Standard Model, we do not know why it has this value. This long-standing problem ...

In fact things are even worse than this. The discrepancy between this calculated vacuum energy from quantum field theory and the observed vacuum energy from cosmological measurements is so huge that it’s one of the most embarrassing and unresolved problems in physics. You see, the calculated ...

Our ‘best guess’ cosmological model—the equivalent of the Standard Model in particle physics—which contains under its umbrella what we currently know about dark matter and dark energy, is called the ΛCDM model (or Lambda–cold dark matter model).

And similar to the way deeper quantum field theories underpin the loose alliance of the Standard Model of particle physics, so too does general relativity underpin the ΛCDM cosmological model.

There is one more important ingredient of the ΛCDM model, which most, but by no means all, cosmologists claim is needed to explain the properties of the universe we see. It is called cosmic inflation, and it provides a possible answer to that perennial question: How did the universe a...