Does Time really Exist?

Episode Summary

Executive Summary: This CrowdScience episode revisits the nature of time, starting with leap seconds and global timekeeping before moving into human time perception and Einsteinian physics. It contrasts atomic time, UTC, GPS, and Earth rotation, then explores why time feels different psychologically and how relativity changes time near speed and gravity, including black holes.

Main Topics: Leap seconds and global timekeeping (Priority: 5/5): The episode explains why leap seconds are inserted into UTC to keep official time aligned with Earth’s uneven rotation, and why this correction is increasingly controversial in modern systems. International time standards and atomic clocks (Priority: 5/5): BIPM’s role in averaging hundreds of atomic clocks to create International Atomic Time is described, along with how it underpins UTC and precise modern timing. Human perception of time (Priority: 4/5): Claudia Hammond discusses mental time travel, memory, emotion, boredom, trauma, and aging as factors shaping how quickly or slowly time feels. What time is, conceptually (Priority: 4/5): Dimitrios Matsakis offers a physics-oriented definition of time as an ordering of events and a coordinate tied to evolution, causality, and closed systems. Relativity and the physics of time (Priority: 5/5): Marek Kakula explains Einstein’s space-time, time dilation, and how motion and gravity make clocks run at different rates, including for astronauts and near black holes. Time travel and the arrow of time (Priority: 4/5): The program examines whether backward time travel is possible, why we remember the past but not the future, and how memory creates the sense that time moves forward.

Key Arguments: Leap seconds are necessary to reconcile atomic time with Earth’s irregular rotation, but they create operational risks for sectors needing uninterrupted, ultra-precise timestamps. Modern systems like GPS prefer continuous time and are disrupted by leap-second insertion, making leap seconds a growing technical liability. Time is not just a physical measurement; for humans it is deeply shaped by memory, attention, emotion, and the number of novel experiences we accumulate. Older age makes time seem faster not simply because life is proportionally shorter, but because routines blur memories together and reduce distinct time markers. Einstein’s relativity shows time is not universal: clocks in motion or deep gravity fields tick at different rates, and this has been experimentally confirmed. Backward time travel remains speculative; even if possible, physics may impose self-consistency constraints that prevent changing history. Near a black hole, gravity distorts space-time so strongly that time and space effectively swap roles at the event horizon, making the singularity part of the future direction.

Data Points: Atomic clock accuracy: 1 second in 300 million years - Mentioned when recalling National Physical Laboratory atomic clocks Leap seconds added since 1972: 26 times - Count of leap seconds introduced to keep UTC aligned with Earth rotation Atomic clocks used by BIPM: About 450 - Global atomic clocks averaged to produce International Atomic Time UTC vs International Atomic Time difference: 37 seconds - Current divergence noted between UTC and TAI Financial sector timestamp accuracy need: Microsecond accuracy (10^-6) - Used to explain why leap seconds are problematic for trading systems Clock precision provided today: Tens of nanoseconds accuracy - Felcitas Arias describing modern time services Leap-second impact example: 400 flights cancelled - 2012 Australian airline computer crashes linked to leap second issues Astronaut aging difference: A fraction of a second less over six months - Illustration of time dilation on the International Space Station Arrow-of-time perception: One minute of lost divergence per roughly 100 years - Rami’s estimate of how slowly UTC and Earth rotation drift apart

Pivotal Quotes: "The leap second is not a friend of the electronic trading." — Felicitas Arias: Explaining why financial markets dislike discontinuities in official time "Time is that coordinate that can be most simply related to the evolution of closed systems." — Dimitrios Matsakis: His formal definition of time for Encyclopaedia Britannica "What is weird is we all know what the passing of time feels like, although it's impossible to describe." — Claudia Hammond: Describing time as a psychological experience rather than just a physical quantity

Implications: Listeners are left with time as both a technical standard and a subjective experience. For industry, leap seconds may become untenable; for science, relativity and black holes show time is flexible; for individuals, memory and attention shape lived reality.