10 Unknowns of the Universe

Known: The universe is expanding from a hot dense state ~13.8 billion years ago; the Big Bang model is verified back to the first fractions of a second. Inflation is strongly supported but not confirmed.

Unknown: Whether 'before' exists at all — if time began with the Big Bang — or whether the Bang was a transition inside an older cosmos (bounce, eternal inflation, cyclic, or quantum-gravity tunneling).

Known: Gravitation, unambiguously: galaxy rotation curves, lensing, CMB — about 85% of matter interacts via gravity but not electromagnetically. Decades of direct-detection searches have come up empty.

Unknown: What it actually is — a WIMP, an axion, primordial black holes, sterile neutrinos, a modified-gravity effect, or something not yet imagined.

Known: The expansion is accelerating; a cosmological constant (Λ) fits observations, and 'quintessence' (a dynamic field) is the main alternative. Recent surveys probe whether dark energy evolves.

Unknown: Its physical nature, its constancy over time, and the vacuum-catastrophe: quantum field theory's vacuum prediction is off from Λ by some 120 orders of magnitude — the worst mismatch in physics.

Known: CP violation exists (verified), baryogenesis had to occur in the first moments, and a tiny excess of matter over antimatter — about one part per billion — survived annihilation to make everything.

Unknown: Which mechanism (Sakharov conditions fulfilled how?) created the asymmetry — Standard Model CP violation is far too weak; candidates include leptogenesis, electroweak baryogenesis, or new physics.

Known: The laws of motion are (nearly) time-symmetric; the forward direction comes from the second law — entropy increases — which points to an extraordinarily low-entropy initial condition at the Big Bang.

Unknown: Why the early universe had such a low entropy at all (the Past Hypothesis) — whether the arrow of time is fundamental or emergent, and whether other arrows (causality, memory, radiation) reduce to it.

Known: Quantum mechanics is the most accurately verified theory in science, and every practical prediction (Born rule, decoherence) works — decoherence explains why interference disappears at macroscopic scale.

Unknown: Which interpretation is right — Copenhagen, many-worlds, objective collapse, QBism, pilot-wave — and, deeper, what physically singles out one outcome. All are experimentally equivalent so far.

Known: General relativity and quantum field theory each work superbly in their domains; string theory and loop quantum gravity are the main candidate frameworks, neither confirmed by experiment.

Unknown: Which — if either — is correct, and what the theory predicts where both matter: inside black holes, at the Big Bang, in high-energy quantum gravity regimes we cannot yet probe.

Known: Life on Earth existed by ~3.7 billion years ago; prebiotic synthesis of amino acids and nucleotide precursors works in the lab; RNA's dual information/catalysis role anchors the leading hypotheses.

Unknown: The specific path — an RNA-first world, metabolism-first, mineral-surface chemistry — from raw chemistry to a self-replicating, evolvable system. No one has made life in a beaker from scratch.

Known: Consciousness correlates strongly with thalamocortical activity and integrated neural processing; specific circuits gate awareness; anesthesia and brain lesions map parts of the terrain.

Unknown: The Hard Problem: why physical processing is accompanied by subjective experience at all, and which proposed theory (global workspace, IIT, higher-order, others) correctly explains it.

Known: Thousands of confirmed exoplanets, many in habitable zones; life arose fast on Earth; thousands of stars have been scanned for technosignatures — none confirmed.

Unknown: The Fermi paradox's real answer: which step of the chain from abiogenesis to spacefaring civilization is the bottleneck (a 'Great Filter'), or whether the silence has a mundane explanation we haven't run down.