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How long would it take to travel a light year?

Our universe has a speed limit, and this limit is set by the speed of light which travels at the mind boggling pace of 186,282 miles per second, or 299,792 kilometres per second. That’s 670,6 million miles per hour, or 1.1 billion kilometres per hour. Basically, if you had the ability to travel at the speed of light, you would be able to do a complete cycle around the Earth seven and a half times each second. Imagine, for example, the speed at which Liz Truss was—and then very quickly wasn’t—the UK’s Prime Minister. So, when human hour’s turn to years, we’re talking light years in particular, how long would a light year take in human time?

The theory of relativity

Thanks to Albert Einstein’s trusty theory of relativity, which is based on two key concepts—special relativity and general relativity—we can figure this out. In layman’s terms, Einstein’s theory translates as everything is relative, but the speed of light is constant.

To warp your thinking a bit, consider rulers and clocks—these tools mark time and space and are not the same for different observers. However, if the speed of light is constant, as Einstein stated, then time and space cannot be absolute or uniform, they must instead be subjective. Einstein read the relationship between space and time, and noticed that their consequences were intertwined. In fact, space and time can no longer be independent. Don’t worry, we’re almost there.

We as humans have many misconceptions of time and space because time, for one, feels like it’s relentlessly moving forward. Time to us, flows, and has a direction that advances in an orderly fashion. Time has become like a backdrop in which all events take place in space, sequence and durations are measured. So, if you’ve ever felt as though the Kardashians’ ability to continuously create personal brands truly subverts time and space—you’re not alone.

However, this concept is challenged by Einstein’s theory of relativity whereby space and time convert into each other in such a way as to keep the speed and light constant for all observers. In other words, they depend on the motion of the observer who measures them—this is why moving objects appear to shrink. This theory is the infrastructure of our current understanding of the universe. So, how does this all relate to calculating the speed of light then?

Keeping the perspective of a viewer in mind, and bringing in an object that travels (which is essentially what we are measuring here) let’s say, a human that is travelling at the speed of light. To an observer, the size of the human would be miniature, but to the human travelling, they would remain their own size.

Time also passes slower the faster one goes, and mass also depends on speed. The relationship between mass and speed (or energy) is calculated with the formula E=mc^2, where E is energy, m is mass, and c is the speed of light.

How long would it take to travel a light year?

Now back to figuring out how long it would take us to travel a light year. If we were to measure distances in miles or kilometres, we would be working with enormous numbers. So, instead we measure cosmic distances in light years according to how fast light can travel in a year. I know, but bare with me.

According to Futurism, there are just about 31,500,000 seconds in a year, and if you multiply this by 186,000 (the distance that light travels each second), you get 5.9 trillion miles (9.4 trillion kilometres) which is the distance that light travels in one year.

The time that it takes humans to travel one light year is considerably longer than a year. To put it into context, it takes between six months and a year for us to reach Mars, which in light year terms, is 12.5 light minutes away. It took NASA’s New Horizons spacecraft almost ten human years to reach Pluto from Earth—which is ‘just around the corner’, only 4.6 light hours away.

Let’s say we were a space shuttle that travelled five miles per second, given that the speed of light travels at 186,282 miles per second, it would take about 37,200 human years to travel one light year. That’s a long time, and what would you see? Well, not much, unfortunately. You’d be closer to the centre of our own galaxy, but with a further 26,000 light year distance still to travel.

Will light-speed space travel ever be possible?

Okay, we know how long it’s going to take—albeit might not be as impressive once we arrive—but is there a possible way to travel as far as a light year?

From our current understanding, unfortunately no. According to Britannica, Einstein’s aforementioned theory of relativity clearly states that the speed of light is a cosmic limit that cannot be surpassed. And so, light-speed travel would be a physical improbability—especially if it involved mass, such as a human or spacecraft.

It should be noted that Musk may have once considered pursuing the impossible feat, but I imagine he’s far too preoccupied taking over Twitter.

So, while you may be craving some of the magnificent sights captured by the recent James Webb Telescope, I’m afraid you netizens might have to rely on the confines of the internet.

How would language change if some of us moved into the interstellar?

Imagine Noah’s ark, but floating in a sea of stars. If worse comes to worst and we really do have to abandon Earth, we’ll have to take our generation with us in order to save the next—the new generation would then become the ‘generation ship’. In order for us to save the human race,  a variation of ages would be sent to space. How could a potential move to space alter the way we speak?

First things first, we would need to take our environment with us. Everything will be on board—everything alive, that is. Maybe we’d be allowed to bring the odd memorabilia, but all packing has a priority order as we know, meaning that the heavy bits and pieces at the bottom of your shopping bag would usually go first. In this case, other than ourselves, the minuscule would take a predominant lead with bacteria, seeds and gases.

The long journey we would be embarking on also means that we would inevitably evolve over time. People will continue to be born, raised and, eventually, die. Interstellar travellers would probably have a lot less space to live their lives. Biologically, this could lead to all kinds of issues or mutations that cannot be foreseen. One other thing in particular will have to evolve too: language.

A team of linguistics professors, Andrew McKenzie and Jeffrey Punske, published an ongoing study based on Language Development during Interstellar Travel, in the April issue of Acta Futura, the journal of the European Space Agency’s Advanced Concepts Team.

In the study, they discuss how languages evolve over time as communities grow isolated from each other. In this case, our entire population couldn’t possibly fit on the ship—which sparks another discussion altogether—we would have to leave humans behind. If the ship were to come back to Earth, would the two groups still be able to understand each other, having evolved separately?

One would hope that Earth and the vessel would keep in contact with each other, but time warps in space, so communication of any kind will eventually lag. “If you’re on this vessel for 10 generations, new concepts will emerge, new social issues will come up, and people will create ways of talking about them and these will become the vocabulary particular to the ship. People on Earth might never know about these words unless there’s a reason to tell them. And the further away you get, the less you’re going to talk to people back home. Generations pass, and there’s no one really back home to talk to,” explains McKenzie.

The paper is concluded by the statement that on the generation ship “Eventually, the language or languages of the crew will diverge from those on Earth. If they start out with multiple languages, those will perhaps converge towards each other,” whereas on Earth, the opposite may happen. Language is formed by finding mutual understandings for the purpose of communication or translation. So, with a significant sum of our population subtracted and shipped away, the geography of our population would be dispersed further. The world as we know it would be, for a time, underpopulated—which may lead to more distinct language barriers and divergence.

We could argue that because of the internet, distance doesn’t control our differences in language as much as it would have in the past. Would the generation ship evolve technologically faster than Earth? It’s hard to decide without knowing exactly what resources they would discover out there  compared to our current rate of advancement.

Time on our beloved planet has proven thus far that most of the imaginable is possible. What’s stopping us from imagining a little more? Furthering our understanding is arguably humankind’s greatest trait, but it’s also the misunderstandings that push our drive to understand further. We’re aiming high to test this out, quite literally. Turns out science and fiction really are yin and yang, but their language is different.