In physics, energy scale is a particular value of energy determined with the precision of one order (or a few orders) of magnitude. Different phenomena occur at different energy scales. The typical energies of all phenomena that occur at the same energy scale are comparable.
The observation that different phenomena should be organized according to the energy scale (or, equivalently, the length scale) is one of the basic ideas of the renormalization group.
For example, the QCD (energy) scale is around 150 MeV, and the masses of strongly interacting particles (such as the proton) are roughly comparable. The electroweak energy scale is higher, roughly 250 GeV. The Planck scale is much higher yet - about 1019 GeV.
"Energy is hands-down the biggest enterprise on the planet," Smalley said, by way of placing its importance in perspective: at $3 trillion a year globally, energy constitutes "the largest industry in the world," versus only $1.3 trillion for agriculture and $700 billion for all defense spending, he said.
These potential energy breakthroughs, which, he said, "could only come from nanotechnology," also include a "revolution" in hydrogen storage; direct conversion of light and water into hydrogen supplies; "photocatalytic" reduction of carbon dioxide; and nanomaterials, or coatings enabling the possibility of very deep drilling into Earth to obtain geothermal heat.
Solving this gigantic energy problem, which Smalley termed "the largest enterprise of humanity" on the horizon, would go far toward solving many of humanity's other most pressing problemssuch as food and water supplies, environmental degradation, and povertybecause they are so directly affected by the availability of energy, he said.
For energies approaching the Planck scale, an exact theory of quantum gravity is required, and the current leading candidate is string theory, or its modernized form M-theory.
At the Planck scale, the strength of gravity is expected to become comparable to the other forces, and it is theorized that all the fundamental forces are unified at that scale, but the exact mechanism of this unification remains unknown.
Planck scale dynamics is important for cosmology because if we trace the evolution of the cosmos back to the very beginning, at some very early stage the universe should have been so hot that processes involving energies as high as the Planck energy (corresponding to distances as short as the Planck length) may have occurred.
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