Time Isn’t Universal — and That Changes Everything | What the Physics?!

PBS NOVA
PBS NOVAApr 17, 2026

Why It Matters

Because modern navigation, communication, and climate‑monitoring technologies rely on nanosecond‑level timing, relativistic corrections are critical to their reliability and to future space missions.

Key Takeaways

  • Earth's core experiences time lag of 2.5 years versus surface
  • Time dilation varies with velocity and gravitational strength per Einstein
  • Atomic clocks on GPS satellites run 38 microseconds faster
  • Millimeter‑scale height differences cause nanosecond‑scale time offsets over decades
  • Precise time measurements can forecast earthquakes, sea‑level rise, and climate change

Summary

The video explains that time is not a universal constant; it flows at different rates depending on velocity and gravitational field strength, a phenomenon first described by Einstein’s theories of special and general relativity.

Examples include Earth’s core lagging 2.5 years behind the surface, astronauts on the ISS experiencing micro‑second differences, and GPS satellites whose onboard atomic clocks run about 38 microseconds faster than ground clocks. Laboratory tests have even measured a 90‑billionth‑second discrepancy between a person’s head and shoulders over a lifetime.

The presenter illustrates the effect with a light‑clock thought experiment and notes that without relativistic adjustments, GPS navigation would drift six miles per day. Ongoing experiments on the ISS and high‑precision terrestrial clock networks aim to detect minute gravitational variations that precede earthquakes or track melting ice.

These findings underscore that accurate timekeeping is essential for navigation, communication, and Earth‑monitoring systems, and they open pathways to map the planet’s gravitational landscape, potentially revealing new insights into dark matter, black holes, and the nature of time itself.

Original Description

Time isn’t the same for everyone, according to Einstein.
Hosted by Athena Bresnberger @astroathens 💫
💙 Help us bring the universe closer to home. Your donation ensures that NOVA’s deep-space discoveries and quantum physics explorations remain free and inspiring for the next generation of scientists. Support fact-based storytelling today https://bit.ly/48UnsrD
📰 Stay up to date on the latest science discoveries, full episodes, articles, videos, and more by signing up for NOVA's newsletter here: https://to.pbs.org/4brCC7Y
▶️ Stream NOVA documentaries & more with PBS Documentaries on Prime Video: https://amzn.to/4hXBlsu
🛍️ Shop official NOVA 50th anniversary merch: https://nova-shop.org/
Follow on social for more NOVA content

Comments

Want to join the conversation?

Loading comments...