the lack of a GPS alternative invites attack.

a recent demonstration by an IBM hacker showed that you don't need a missile to hobble our timing-based infrastructure

Before you can settle into your new moon base, you need to have an accurate moon clock.

Why is timing so critical for modern networks?

Who You Gonna Call? It is well known that GPS is an Achilles' heel for our modern world.

You wake up. Emergency and rescue radios are down. Your location app is offline and planes are grounded worldwide.

The time you see on your phone is synchronized to a clock at the US Naval Observatory, delivered via GPS satellites through your local cell

A Brief History of Time (Synchronization)