It has been over a century since General Relativity and Quantum Mechanics have become the two most basic forms of our understanding of the universe. Each has enormous success in its own area–as General Relativity able to simply solve a huge number of new problems Quantum Mechanics gives an extremely accurate description down to very small scales. However, despite their successes, these two frameworks cannot ultimately be reconciled. So quantum gravity is in fact an effort to make one big natural law, not simply bridging the gap between two disciplines.
The Unbridgeable Standoff of Two Schools of Thought
The most vivid example comes with gravity. According to General Relativity, gravity is the curvature of space-time due to mass and energy. This may be decently expressed by in the endless smooth equations that are infinitely continuous. Quantum Mechanics, on the other hand, operates at a microscopic level and relies essentially on probabilities. There are only certain minimum values which many physical quantities can take because of the uncertainty principle: for specific pairs of variables – of which position and momentum are one–a fixed value at any single moment is not always possible.
And so on the boundary where Quantum Mechanical behavior becomes important, the smooth classical picture of space-time given by General Relativity will give way to something else. At such scales the old equations of General Relativity itself break down and we must use a new paradigm where both theories come into play.
Seeking Quantum Gravity
Different attempts have been made to construct a quantum version of general relativity, the best-known of which is string theory. Strings vibrating at different frequencies. Each of these is recognised as a different particle. It is an unusual theory.
The theory says that the basic building constituents of such matter do not exist in some taralist sPace but rather one-dimensional ‘strings”each vibration ip this het uNit is thus a different particle. string theory has the property of naturally sup- plementing gravity and so combines gravity Electromagnetic, weak nuclear forceaU and strong nuclear forces. It is indeed an excellent applicant for s Quantum Gravity However, requiretling more dimensions than the known four— three for space and one for time—this forcing difficult predictions which one cannot test.
Except that@ this plae quantum gravity, past contributes have a have always set out, entails a complete revolution in how general relativity is understood. This reverse means that the furtive universe elemen- would stop doing all have found its way back to some large brick earth in the middle of nature All efforts to spread the universe, namely by frontierism of space, must fail.
For as an obsolete concept it will soon be no different from how we now regard the idea that an infinite number of stars are moving through empty space The view taken here therefore produces a picture differing numerically from anything d- duced above. For example: spacetime has structure, but it is atomic whereas those theories which assert there isn’t LQG doesn’t need Added our dimensions.
Cannot be Verified
In terms of quantum gravity research, a major problem is the lack of experimental evidence. The scales at which quantum effects begin to matter in gravitational fields are incredibly small, and such energies are well beyond the capabilities of current particle accelerators. For example, if gravity’s hypothetical quantum particles –gravitons–were indeed emitted in such an interaction
The size of a normal detector makes it to all intents and purposes impossible to try to measure gravitational forces directly by this method. The experimental conditions involved are, in general, inherently unrealistic. Still, indirect evidence might some day come from black hole evaporation (a process predicted by Stephen Hawking), or from studying cosmic inflation–where space is expanding exponentially fast just after the “big bang” of our universe.
And so on these gravitational waves, which had better be found–the ripples traversing all spacetime as their very own pure energy. Perhaps they may also provide a solution. I offer this typically foolish prediction: if the gravitational waves coming from the origin, or origins, of these light pulses can be gleaned in future experiments of quantum `观灏 properties; then maybe we will know what galaxy or galaxies they come from at long last.
The Logical Consequence of Quantum Gravity
Tucked away somewhere in all those ideas is still a theory of quantum gravity; nothing less than the way we shall view our universe. Such a theory might solve the problems stealthy black holes present, maybe clearing up what lies beyond their singularities or whether information really is lost when you throw matter into one–a central issue discussed in the “black hole information paradox”. Quantum gravity theory may provide some insight as well into where the universe as we know it got its start.
Summary
This is one of the most earnest and difficult tasks physics confronts today: searching for a quantum theory of gravity. When General Relativity and Quantum Mechanics can be reconciled, physicists may well feel that they are seeing an old, familiar face replace its mask with another’s. The road to Endeavour still has many a mountain towering over it. Even so, for reasons both theoretical and experimental, prospective rewards-a theory unifying all natural phenomena-loom incalculably great in front of any one who wants to try and grasp them. In our quest for something like quantum gravity, however, we find ourselves looking outside the familiar cosmos. Each one has spacetime as its flora and fauna, built out of the quantum-mechanical craziness which gains control at every small range of scales.