Einstein Refused to Believe This, But It Could Explain the Universe | Sabine Hossenfelder

The Gist

A recent physics paper argues that applying the quantum uncertainty principle to the entire universe resolves the mystery of changing dark energy and proves that gravity obeys quantum rules. While the math offers an elegant connection between cosmic acceleration and quantum mechanics, it relies on unverified theoretical assumptions and an unproven predictive power constant.

Quick Overview

New cosmological observations show that dark energy is not constant and its value is decreasing, matching a recent physics paper by Savvas Koushiappas that applies quantum uncertainty to the entire universe. This framework suggests that the universe's accelerating expansion is smaller because of an uncertainty contribution tied to the size of the cosmos. Although the argument bridges cosmology and quantum mechanics neatly, the paper contains notable theoretical shortcomings regarding unmeasured constants and assumptions about quantum gravity.

Key Points: Recent astronomical observations show that dark energy is not constant and its value is decreasing over time. Physicist Savvas Koushiappas published a paper in Physical Review D titled Cosmological uncertainty relation and late universe acceleration. The paper argues that applying the quantum uncertainty principle to the entire universe explains why dark energy is evolving. Quantum uncertainty dictates that certain pairs of quantities like position and velocity cannot both be measured to arbitrary precision. The new cosmological formulation applies this principle to the size and speed of the universe, linking cosmic acceleration directly to quantum mechanics. The author concludes that the observed acceleration of the universe is smaller due to a contribution coming from this cosmic uncertainty. The paper has two major shortcomings, including the inability to predict the absolute size of the effect and the reliance on a candidate approach to quantum gravity.

Context: Astronomers have long debated the nature of dark energy, the mysterious force driving the accelerated expansion of the cosmos. Albert Einstein originally introduced the cosmological constant in 1917 to keep the universe static, later calling it his biggest blunder when expansion was discovered. Modern observations have complicated this picture further by suggesting dark energy changes over time, forcing physicists to search for fundamental links between cosmology and quantum mechanics.