What If the Speed of Light Got Slower and Couldn’t Stop?

What if the speed of light got slower every second and never stopped? Light normally travels 299,792 km/s (186,282 miles per second). Here it loses 5% of its speed every second and halves every 13.5 seconds. Follow one first date in Paris, from a sunny café to total darkness, as GPS fails, the Sun dims, phone calls die and the city curls up into a bowl, until light is slower than a person walking. WHAT HAPPENS IF THE SPEED OF LIGHT SLOWS DOWN • GPS goes wrong first, because it depends on the exact speed of light • Sunlight dims on its way to Earth, so afternoon turns to dusk and then night, with no clouds • Satellite TV and phone calls lag, then die • Earth can no longer hold its orbit once light is slower than its own 30 km/s (about 67,000 mph) • Light gets slower than sound, so you hear things before you see them • The horizon rises into a bowl, because light from far away arrives falling • Headlights turn blue and taillights fade out of sight as cars approach light speed • At 18 mph (8 m/s) you can only see a few metres, and your own hand appears late QUICK ANSWERS Q: What would happen if the speed of light slowed down? Everything that depends on light travel time breaks: GPS, satellites, phone calls, then sunlight itself. In this video light loses 5% of its speed every second, so in about six minutes it is slower than a person walking. Q: How fast is the speed of light? 299,792,458 metres per second: about 186,282 miles per second, or 671 million mph. Q: Would the Sun go out? No. The Sun keeps shining, but the light already on its way to Earth slows down, so the sky dims and then goes dark. Q: Could this really happen? No. The speed of light is a fixed constant in relativity, and the rest of physics depends on it. This is a thought experiment. THE READOUT The numbers in the corner are calculated from one rule: the speed of light is 299,792 km/s multiplied by 0.95 every second. Which what-if should we do next? Tell us in the comments. #whatif #speedoflight #physics #science #light