ZA_2_11 — Spacetime Foam and Quantum Gravity Effects

At the Planck scale — lengths of ~$1.6 \times 10^{-35}$ m and times of ~$5.4 \times 10^{-44}$ s — quantum mechanics and general relativity collide, and the smooth spacetime continuum of Einstein's theory is expected to b

Q_1_18 — Loop Quantum Gravity: Discrete Spacetime and the Planck Scale

Loop Quantum Gravity (LQG) is one of two major approaches (alongside string theory) to the quantization of general relativity — the long-sought unification of quantum mechanics and Einstein's theory of gravity. LQG's fou

ZA_2_04 — Loop Quantum Gravity: Spacetime as a Fabric of Quanta

Loop quantum gravity (LQG) is a leading approach to quantum gravity that quantizes spacetime itself — predicting that area and volume come in discrete Planck-scale quanta. Unlike string theory, LQG does not require extra

ZA_1_19 — Loop Quantum Gravity

Loop quantum gravity (LQG) is one of two leading candidate theories (alongside string theory) for unifying general relativity with quantum mechanics — the central unsolved problem of theoretical physics. [KEY FINDING] LQ

ZA_2_17 — Emergent Spacetime & ER=EPR Conjecture

The ER=EPR conjecture — proposed by Juan Maldacena and Leonard Susskind in 2013 — posits that Einstein-Rosen bridges (wormholes, "ER") and Einstein-Podolsky-Rosen entanglement ("EPR") are fundamentally the same phenomeno

ZA_2_09 — Wormholes and Exotic Spacetime Geometries

Wormholes — hypothetical tunnels through spacetime connecting distant regions of the universe or even different universes — are exact solutions of Einstein's field equations. First identified by Einstein and Rosen (1935)

ZA_2_06 — Spacetime Geometry: Minkowski, Causal Structure, and Light Cones

Spacetime — the four-dimensional continuum unifying space and time — is the arena in which all physics takes place. Einstein's special relativity (1905) revealed that space and time are not separate absolutes but are int

P_1_14 — Philosophy of Space: Absolute vs. Relational, and the Architecture of Being

The philosophy of space addresses one of the oldest questions in metaphysics: what is space? Is it a real, independently existing entity (an infinite container within which objects are located), or is it nothing more tha

Q_1_05 — Holographic Principle

The holographic principle proposes that all information contained within a volume of space can be encoded on the boundary surface of that region. First suggested by Gerard 't Hooft (1993) and developed by Leonard Susskin

Q_1_23 — White Holes: Theory and Implications

A white hole is the time-reversed analogue of a black hole — a theoretical spacetime region from which matter and light can emerge but into which nothing can enter, as opposed to a black hole's event horizon from which n

Q_4_02 — Gravitational Wave Astronomy

Gravitational waves — ripples in spacetime predicted by Einstein's general relativity (1916) and first directly detected by LIGO (Laser Interferometer Gravitational-Wave Observatory) on September 14, 2015 (event GW150914

Q_2_01 — Black Holes, Singularities, and Information

Black holes are regions of spacetime where gravity is so extreme that nothing — not even light — can escape once it crosses the event horizon. Predicted by general relativity (Schwarzschild solution, 1916), regarded as m

P_1_09 — Philosophy of Time

The philosophy of time addresses some of the deepest questions in metaphysics: Is time real or an illusion? Does the present moment have a special ontological status, or are past, present, and future equally real? Does t

ZA_2_13 — Quantum Gravity Approaches

Quantum gravity is the unfinished quest to unify general relativity (GR) — which describes gravity as spacetime curvature at macroscopic scales — with quantum mechanics (QM), which governs microscopic physics. The challe

ZA_2_02 — Gravity, Gravitational Waves, and Anomalous Gravitational Claims

Gravity — the weakest of the four fundamental forces yet the dominant force at cosmic scales — remains the most mysterious force in physics. Newton's law of universal gravitation (1687) described gravitational attraction

ZA_2_03 — General and Special Relativity — Einstein's Revolution

Albert Einstein's two theories of relativity — special (1905) and general (1915) — fundamentally reshaped the understanding of space, time, mass, energy, and gravity. Special relativity, built on Lorentz invariance and t

ZA_2_00 — Gravity Spacetime Cosmology: Subfolder Summary

ZA_2_14 — Penrose Twistor Theory: Spinor Geometry and Spacetime

Twistor theory — conceived by Roger Penrose beginning in 1967 — is a radical reformulation of the geometry underlying physics in which the fundamental objects are not points in spacetime but rather twistors: elements of