What if we travel with the Light speed?!

To travel the speed of light isn’t actually possible for anything other than massless particles, like photons. It would require infinite energy to get something with mass to that speed. The energy required exponentially goes up the closer you get. But there are instances of matter coming close, we’ve observed some particles travelling 99% of the speed of light. Now for you and me, we have no hope of ever approaching these speeds, but if you did manage it, what happens to space and time from your perspective would be very noticeable.

Let’s ease you into this, as it’s going to be a bit tricky to wrap your head around. We will simulate going from standing to travelling almost the speed of light. This is a fun little game called ‘A Slower Speed of Light’, released by MIT, demonstrating what would happen if the speed of light got progressively slower, eventually to walking speed. At first, my character looks around and sees the world normally. But as I start to pick up these orbs, instead of speeding me up, the game slows the speed of light down, to simulate what it would look like if we were travelling extremely fast over vast distances. As the speed of light slows, what becomes apparent to you? The first thing I notice is that colors start to change. This is because of something called the Relativistic Doppler Effect.

When you look around and you see color on objects, this is because light is reaching your eyes at specific wavelengths. The longest wavelengths you can see are reds, and shortest wavelengths are violets. Beyond the range of our sight are infrared and ultraviolet. But when you start going very fast, because of the doppler effect, some of the wavelengths that were in the infrared and ultraviolet now shift to wavelengths you can detect. Suddenly, things that were invisible to us before, become visible, like heat in infrared and florescent substances in ultraviolet. The faster you travel, the larger your visible range now becomes.

Light does travel in waves, but it is also a stream of particles, called photons. As you head into the flow of particles at speed, more particles will hit your eyes, making everything ahead of you brighter. On the other hand, if you look behind you as you travel forwards, everything will get darker, because less photons are reaching you. This is known as the Searchlight Effect.

What else do you start to notice? You may notice that we seem to be gradually speeding up. But actually, our speed always stays the same throughout this game, we are just walking like we were at the beginning. This is a result of Special Relativity, namely Time Dilation. One of the laws of the universe is that the speed of light is a constant. However, space and time are not, and can be warped. So, when you start moving, two things change: your time and your distances relative to stationary observers.

Time goes slower for an object that goes faster. This has been proven. If you have two clocks, one stationary, and the other in rapid motion, on say a rocket, eventually the times on each will go out of sync. This is why the times on satellites in orbit around Earth need to be occasionally adjusted, or they’d go out of sync with Earth based clocks. Not by much, a few milliseconds per year, but it would add up eventually. The faster you go, the more time dilation happens, until should you hit the speed of light, the rate of time reaches zero. This means photons, or light particles travelling the speed of light, are unaffected by the passage of time.

But let’s go back to how time dilation affects us in the game. Removing the lighting effects will help us see this more clearly. Now remember, throughout the game, our walking speed stays the same, it’s the speed of light that slows down as we collect more orbs. And yet, it seems that we move a lot faster towards the end of the game than at the beginning. What is happening here is that our time is going slower than everything around us. As a result, it’s like the distances of space are shorter, meaning we get somewhere quicker from our perspective. In practice, this means that if we travelled in a vehicle that approaches the speed of light, and we travel for one year at that speed, it all seems normal for us, but 10 years have passed for people on Earth. Should you actually be able to travel the speed of light, you could get anywhere in the universe instantaneously from your perspective, but on Earth, however far in light years your journey takes you will equal the equivalent number of years from their perspective.

Do you want to go 40 light years away and can travel the speed of light? You get there instantaneously from your perspective, but for people on Earth, you show up there 40 years later. Again though, in practice light speed travel is impossible for anything made of matter. The last effect is a weird one, it’s like our field of view changes. This is from the effects of the Aberration Of light and Lorentz Transformation. Light takes time to reach our eyes, and when we see anything, we are seeing that object in the past. As we move in the game, that object we are seeing isn’t where we think it is anymore. This effect also means that I can see much more of my surroundings in one go.

The light source is moving relative to me as I move forward, but because the beam of light takes time to reach me, I see it where it was relative to me in the past. When there is a lot to see all around me, it’s as if my field of view increases the faster, I travel, as I’m suddenly seeing all these objects as they were relative to me in the past. Light, space and time get more complicated still, but I won’t delve into it in this article. In the opposite vein, us being able to approach the speed of light would be beneficial for travelling large distances in short times, however time is passing normally for people on Earth, meaning travelling anywhere in the universe and coming back again could be possible for you, but Earth would look a lot different on your return, with years, decades, millennia or more having passed depending on how far you went.

On your journey, due to the various effects, outside your ship everything would look warped, your field of view would be greater, a greater range of light wavelengths become visible, and in front of you would be much, much brighter. So, there we have it, how your universe would change if you approached the speed of light?