Yet it has no synonym when we wish to discuss a source of power or the capacity to do work. Moreover, it's now a century since Einstein showed that matter and energy are two sides of the same coin. They're equivalent. This means that all the seemingly solid objects of the universe are concentrated forms of energy.
This being so, it is correct to say that the entire universe is energy in various guises. Indeed, physicists often prefer to think of electrons as their energy equivalents rather than as solid objects weighing 1,836 times less than protons. When an electron and its antimatter analogue (the positron) collide, both vanish, having been transformed into their equivalent energies of 511,000 electron volts apiece.
One now-common application of this principle is the PET scan. The "P" stands for positron, a bit of antimatter, which is created and released by radioactive material injected into the blood. The gamma ray energy created by positron/electron annihilations allows the machine to chart the positions of the tissues that have absorbed the radioactive substance.
The widely accepted existence of Z-point energy or vacuum energy, an unimaginably powerful energy field that pervades the universe, supplies us with even more wildness. Particles appear and disappear in and out of this invisible, all-enveloping field; some remain in existence permanently. We can regard atoms, planets, rocks and people as ever-so-slightly increased concentrations of energy in the all-pervasive field, like lumps in pudding.
All these little eddies in the field, whether hamburgers or sunlight, attract our notice only because our senses have been fashioned to perceive them. This can't be stressed enough: We're aware of the slight, piddling energy bumps that surround us, but blind to the underlying field itself.
When we touch things, we never encounter solids. Rather, your nose's atoms' electrons have a charge that repulses the fields of the electrons of your fingertips. This is the only reason your finger does not penetrate your head when you scratch your nose. The empty spaces in all the atoms of your body are so vast that you contain virtually no solids at all. You merely feel energy fields - not solids - when you touch anything.
If we removed all the space from all the atoms in all the people on Earth, the solids that remained (mostly protons and neutrons) would fit inside a single sugar cube. That's us, Homo sapiens: one cc weighing half a billion tons. The rest is empty space. If you care to calculate the energy content of the human race, convert those half-billion tons of solids to grams (28 to the ounce) and multiply that by the speed of light expressed in centimeters per second, squared. Then you'll have our collective energy in ergs.
But the number hardly matters. It's all energy everywhere. And despite all the seeming changes large and small, the universe's total energy never fluctuates. It cannot decrease.
All this may help those who seek "cosmic unity" in a scientifically valid way. But any sense of profundity is short-lived when we try to follow this up. No redefining of the universe's bottom-line essence can help solve the familiar time-based questions that seem to torment our collective liquidy brains.