Jellyfish Nebula and also its surroundings (Image Credit: Patrick Gilliland)

Thanks to Albert Einstein’s theory of Relativity, we recognize that our universe has actually a rate limit. This limit is set by the speed of light, which travels a staggering 186,282 miles per 2nd (299,792 km/sec). If we are looking at hours, that translates to 670.6 million mph (1.1 exchange rate kmh). For a small context, if you to be traveling in ~ the rate of light, girlfriend would have the ability to whip about the planet 7.5 times every second.

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It’s pretty dang fast, which come in handy for measurements.

Since the cosmos is together a huge place, if we measured ranges in miles or kilometers, we would certainly be working with some amazingly huge numbers. Together such, we measure cosmic distances according to how quick light can travel in a year. If you space wondering, there room just about 31,500,000 seconds in a year, and if you main point this by 186,000 (the street that irradiate travels every second), you get 5.9 trillion miles (9.4 trillion km)—the distance that light travels in one year.

In short, on Earth, we talk around things in relationship to feet or meters, yet in the cosmos, we talk about things in relationship to light.


For example, the Milky means galaxy is some 100,000 light-years across, and also our closest galactic neighbor, Andromeda, is part 2.5 million light-years away. In other words, the takes light 2.5 million years simply to take trip from our galaxy come the one the is right next to us. Remember the the following time that you watch a Hubble photo that mirrors a host that galaxies dancing across the cosmos—what you are looking at is amazingly much away.


Image via European southerly Observatory/ESO

The time that it takes us to travel one light-year is (unsurprisingly) considerably longer 보다 a year. In fact, the takes between six months and also a year just to with Mars, i m sorry is just 12.5 light-minutes away. And it took brand-new Horizons nearly a decade to make its way from planet to Pluto, which is just roughly the corner, 4.6 light-hours away.

This expression is a little bit of a problem, together it makes space exploration a painstakingly sluggish process.

Even if us hopped aboard the room shuttle discovery, which can travel 5 miles a second, it would certainly take us around 37,200 year to go one light-year. Walking? That would take us some 225 million years (that’s assuming the you managed a continuous speed that 20 minutes because that every mile and also didn’t protect against for any type of bathroom breaks…it would be a little trying, come say the least, specifically when one considers that contemporary humans have actually only been around for around 200,000 years.


The worst thing? even after all that time, us still wouldn’t be anywhere also remotely interesting. The closestly star, Proxima Centauri, is much more than 4 light-years away.

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