Undoubtedly, the sensation of speed carries an unmatched thrill, and the swifter the pace, the more invigorating the experience becomes. In the modern age, humanity has invented all sorts of fast-moving entities, spanning from rapid bullet trains to military aircraft designed to achieve speeds reaching a staggering Mach 6.
Yet, despite these achievements, one thing triumphs over all when it comes to motion—light. As such, if you have ever wondered what it would be like to travel at the speed of light, read on to learn what it would feel to experience the pinnacle of velocity in the known universe.
How the Theory of Relativity Changed Our Perspective of Time
As you may have learned from class or your physics tutor, Einstein’s Theory of Relativity cleared up many doubts about mass and energy, starting with the equation of mass-energy equivalence, which evidenced that these two concepts can be converted into the other and vice versa. Einstein also proposed that there exists no standard frame of reference, hence why everything is relative, including time.
From this foundation, we deduce that light maintains a consistent speed regardless of the observer’s perspective—whether they’re stationary or in motion. This implies that a light beam would appear identical to both someone at rest and another individual moving at half the speed of light in the same direction as the light itself.
But how does mass-energy equivalence tie into all of this? Essentially, it suggests that objects will experience an increase in mass proportional to their velocity as they approach the speed of light. For instance, an object travelling at 10% of light speed will undergo a 0.5% augmentation in its original mass. As that velocity approaches 90%, the mass increase would double the initial value.
Can Humans Achieve Light-Speed Travel?
Unfortunately, humans would not survive at such speeds, making the prospect of travelling at light speed a distant dream.
As previously explained, an individual’s mass experiences rapid growth as they approach the speed of light, which is around 299,792 kilometres per second. Achieving such velocity would necessitate mimicking an entity with infinite mass, requiring an infinite amount of energy for propulsion— which is simply impractical.
What About Traveling Almost at the Speed of Light?
Moving at nearly the speed of light is a different playing field that presents many interesting observations. For one, a person travelling at such speeds would perceive the slowing of time, otherwise known as time dilation.
For instance, imagine a spacecraft embarking on an expedition from Earth to Mars and back, maintaining a constant speed of 90% of light speed with instantaneous acceleration. Covering a total distance of 450,000,000 kilometres in an uninterrupted round-trip would seemingly take about 16 minutes, roughly. However, there’s a fascinating twist in this scenario. The estimated time duration applies exclusively to the crew on Earth who are observing the journey from afar. Meanwhile, for the astronauts onboard, the experience would span around eight minutes.
These high velocities bring forth the concept of time dilation. Essentially, as your speed increases through space, your progress through time decelerates. This also means there would be a difference in age as the people on Earth get older by 16 minutes while the astronauts just aged by eight.
Now, let’s kick things up a notch and increase our speed to 99.99% of light speed. This time, let’s envision a voyage to Alpha Centauri, which is now positioned beyond our solar system and is approximately 4.35 light-years away. Undertaking this journey and returning at our newly heightened speed under identical circumstances as before results in a trip of roughly eight years and eight months when perceived by those back on Earth. Meanwhile, our interstellar explorers will have only spent 1.5 months for the entirety of the trip
Redshift and Blueshift
In addition to time dilation, there are also phenomena known as redshift and blueshift that come into play when nearing the speed of light. Upon leaving Earth at such speeds, the light waves that bounce off you undergo a stretching process, causing them to elongate. This elongation leads to the perception of a reddish hue for those observing from Earth. Conversely, when you return from your journey, a contrasting effect occurs: the light waves become compressed by the time they reach the eyes of the observers, resulting in a bluish appearance of the travellers.
From the traveller’s perspective, the world ahead appears compacted, creating a somewhat blurred tunnel-like vision. Intriguingly, once you attain a specific velocity, your surroundings might turn pitch-dark since the wavelength of light entering your eyes extends beyond the visible spectrum.
Exploring the universe would be so much easier if we could achieve near-light speed travel, but the rules like dilation covered above would still apply and pose their own unique challenges. And while such a feat remains a pipe dream for now, it may become a reality far into humanity’s future.
If you’d like to contribute to helping humankind achieve interstellar travel, you can cover the fundamentals you need by signing up at Tuition Physics. As a leading tuition centre, we understand that physics can be intimidating for many students. Therefore, our JC and IP physics tuition in Singapore aims to tackle this problem by helping students become familiar with and engaged in its many key concepts. Contact us today to learn more details!