Einstein's theory of gravity—general relativity—has been very successful for more than a century. However, it has theoretical shortcomings. This is not surprising: the theory predicts its own failure at spacetime singularities inside black holes—and the Big Bang itself.
Unlike physical theories describing the other three fundamental forces in physics—the electromagnetic and the strong and weak nuclear interactions—the general theory of relativity has only been tested in weak gravity.
Deviations of gravity from general relativity are by no means excluded nor tested everywhere in the universe. And, according to theoretical physicists, deviation must happen.
Deviations and quantum mechanics
According to a theory initially proposed by Georges Lemaître and widely accepted by the astronomical community, our universe originated in a Big Bang.
Other singularities hide inside black holes: Space and time cease to have meaning there, while quantities such as energy density and pressure become infinite. These signal that Einstein's theory is failing there and must be replaced with a more fundamental one.
Naively, spacetime singularities should be resolved by quantum mechanics, which apply at very small scales.
Quantum physics relies on two simple ideas: point particles make no sense; and the Heisenberg uncertainty principle, which states that one can never know the value of certain pairs of quantities with absolute precision—for example, the position and velocity of a particle.
Naively, spacetime singularities should be resolved by quantum mechanics, which apply at very small scales.
Quantum physics relies on two simple ideas: point particles make no sense; and the Heisenberg uncertainty principle, which states that one can never know the value of certain pairs of quantities with absolute precision—for example, the position and velocity of a particle.
This is because particles should not be thought of as points but as waves; at small scales they behave as waves of matter. READ MORE...
