Your room can be instantly flooded with light with the flip of a switch.
In fact, there’s no perceivable lag at all.
Because emitted photons travel at a speed of 186,000 miles (300,000 kilometers) per second, light only takes 1/500,000th of a second to reach the farthest part of a typical room. And if it could break through the barrier, it could orbit the planet 7.5 times in a single second.
Light Speed is Fast…
We never think of light as having to “take time” to do anything in our daily lives. It’s incredibly fast, brightening everything in its path in an instant — and scientists believe that, with a few exceptions, light speed is the fastest-known achievable speed in the universe.
But what if we get out of our bubble, and look at light from outside the confines of life on Earth?
Dr. James O’Donoghue, a planetary scientist, created today’s animation to help visualize the speed of light in a larger context. It helps remind us of the mechanics of this incredible phenomenon, while also highlighting the vast distances between celestial bodies — even in our small and insignificant corner of the solar system.
Light Speed is Slow…
Once a photon is sent into the vast abyss, suddenly the fastest possible speed seems somewhat pedestrian.
- Moon: It takes about 1.255 seconds for light to get from Earth to the moon.
- Mars: Mars is about 150x further than the moon — about 40 million miles (54.6 million km) in the closest approach — so it takes 3 minutes to get there from Earth.
- Sun: The sun is 93 million miles (150 million km) away, meaning it takes 8 minutes to see its light.
Let that sink in for a moment: the sun could explode right now, and we wouldn’t even know about it for eight long minutes.
Going Further, Taking Longer
If it takes light a few minutes to get to the closest planets, how long does it take for light to travel further away from Earth?
- Jupiter: The largest planet is 629 million km away when it’s closest, taking light about 35 minutes.
- Saturn: The ringed planet is about as twice as far as Jupiter, taking light 71 minutes.
- Pluto: It takes about 5.5 hours for light to go from Earth to the dwarf planet.
- Alpha Centauri: The nearest star system is 4.3 light years away, or 25 trillion miles (40 trillion km).
- Visible stars: The average distance to the 300 brightest stars in the sky is about 347 light years.
If you really want to understand how “slow” light is, watch the video below and travel from the sun to Jupiter. It takes about 43 minutes because it is done in real time:
So while light obviously travels at a ludicrous speed, it really depends on your vantage point.
On Earth, light is instantaneous – but anywhere else in the universe, it’s pretty inadequate for getting anywhere far (especially in contrast to the average human lifespan).