What if Time Really Exists?

2008/11/23 by Sean M. Carroll, Carroll, Sean M. · 1 voice · 1 citation
Physics and Astronomy · #Cosmology and Gravitation Theories #Noncommutative and Quantum Gravity Theories #Quantum Mechanics and Applications #gr-qc #hep-th

paper · pdf · doi:10.48550/arxiv.0811.3772

openalex publication_date 2008/11/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Despite the obvious utility of the concept, it has often been argued that time does not exist. I take the opposite perspective: let's imagine that time does exist, and the universe is described by a quantum state obeying ordinary time-dependent quantum mechanics. Reconciling this simple picture with the known facts about our universe turns out to be a non-trivial task, but by taking it seriously we can infer deep facts about the fundamental nature of reality. The arrow of time finds a plausible explanation in a "Heraclitean universe," described by a quantum state eternally evolving in an infinite-dimensional Hilbert space.

Citations

• The world as a hologram
• Dimensional Reduction in Quantum Gravity
• Spontaneous Inflation and the Origin of the Arrow of Time

Cited by

• Toward a Phenomenologically Acceptable Quantum Cyclic Universe

Discussions

• What If Time Really Exists? (2008) [hn, 158 points, 204 comments]

Related

• Does time exist in quantum gravity?
• The problem with `The Problem of Time'
• Space time and the passage of time
• Quantum Cosmology and the Arrow of Time
• Space does not exist, so time can