Categories: Astronomy

At cosmic distances, even the speed of light is really slow

The speed of light is the absolute fastest thing in the universe, clocking in at a whopping 299,792,458 meters per second. At that speed, a beam of light could travel around the Earth’s entire equator in a mere 0.13 seconds. That’s…fast. And yet, when it comes to cosmic distances, it’s incredibly, frustratingly, boringly slow.

A new video posted on YouTube by creator and scientist Dr. James O’Donoghue shows the whole scale of interplanetary space – and just how insanely long it takes to get anywhere.

The video starts at Earth, with a hypothetical light pulse (say, a radio transmission) emitted every single second. At that rate, the distance between pulses is a massive 300,000 kilometers. At the speed of light, the pulses race away from the Earth in the blink of an eye.

And then we zoom out.

How slow can you go?

At a new scale, the Earth and the Moon sit at opposite sides of the screen (though in reality they are on average 384,000 kilometers apart). At this position, you can actually watch the light pulses – they are traveling relatively slow enough to be able to follow with the human eye. The pulses take one and a quarter seconds to make the hop. So still, not so bad.

And then we zoom out again.

This time, the Earth-Moon system sits in the far left, while our neighbor planet Mars is on the opposite side of the screen. Hey, it’s the next planet over in the solar system, so it can’t be that bad, can it?

We then are forced to spend the next three minutes in agony as the pulses of light – still traveling at the blistering speed of 299,792,458 meters per second – slowly inch their way across the screen to the red planet, in reality at a distance of over 54.6 million kilometers (in the best case scenario when the planets are at closest approach).

And that about sums it up: light is the fastest thing in the universe, but the true vastness of distances in the cosmos completely overwhelms even that, making communication (let alone travel) the ultimate game of patience.

Paul M. Sutter

Astrophysicist, Author, Host |

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