CAN WE TRAVEL FASTER THAN THE SPEED OF LIGHT?

As of 2020, the fastest car in the world is the Bugatti Chiron Super Sport 300 which clocks an astounding top speed of 304 MPH or approximately 480 kmph. Is this the fastest we can travel? Well you guessed it, definitely not! In fact the Konigsegg Jesco Absolut is all set to debut soon which is expected to break all records once again. If you leave behind the love for roads, and hop on to a wide body jet today, you can travel at around a 1000 kmph. A few years earlier, in a Concorde, you could travel at approximately 2100 kmph which is close to twice the speed of sound, better described as Mach 2. Ditch the passengers, improve your aerodynamics and forget the deficiency of fuel and what you get is a fighter jet and you can clock speeds of Mach 3 to Mach 9… 9 times the speed of sound! NASA’s Space Shuttle Columbia, in fact has the record of the fastest manually controlled flight with 28000 kmph, around Mach 22.

What do all these things have in common? Well, all of these are lesser than 0.0000261 times the speed of light! Why is light so fast and can we ever travel faster than or equal to the speed of light?

The Speed of Light

What would it be like to travel at the speed of light?

Galileo Galilei in the early 1600s tried to calculate the speed of light using timers between hilltops. He concluded that the speed of light was infinite! This is understandable but at the same time astonishing considering what a great mind Galileo was because not that late in the 1670s, Danish astronomer Ole Romer successfully established that the speed of light was a constant. He was studying Jupiter’s moons at the time and predicting when the eclipses of the moons would occur.

It was in the late 20^th century using advanced technologies like inferometry that the exact value of the speed of light was found: 299 792 458 m/s. It’s represented with the alphabet c. Please note this value is only for speed of light in vaccum! Light slows down in a medium. Don’t get it wrong, the individual photon still travel at c, but the path taken is longer like shown below.

Speed of light in a medium

A meter is defined as the length of the path travelled by light in vacuum during a time interval of ​1⁄299792458 second. To have a jist of the speed we are talking about here, remember light can travel 7.5 times around the equator in a single second. 

Why is light so fast?

The simple & sole answer to this is because light is made of photons. Photons have no mass. In fact electromagnetic and gravitational waves also have no mass and therefore travel at the speed of light!

Einstein’s thought experiment

Einstein wondered how it would be to travel at c. Of course, this is not experimentally possible as there was no means to travel that fast, so he developed a thought experiment. Imagine sitting on a train travelling at the speed of light. If you hold a mirror in front of your face, will you see your reflection in a mirror? For you to see your reflection, light has to travel from your face to the mirror and back. How is this possible since you yourself are travelling at c? But Einstein's relativity says, it should be. This is because inside the train you are in an inertial frame of reference. But think about an observer outside the train. For that external observer light in the train seems to be moving at twice the speed of light. This led to an inconsistency.

Einstein concluded that if the speed of light is constant, which it is, this means something else should be changing… Time! He explained that  relative to the external examiner, your time in the train is constant or not moving. Relative to him, there is no distance covered by light inside the train as time is still and the speed of light overall continues to remain c! This is time dilation and is an experimentally proven concept.

Forget us... Can anything travel faster than light?

The fastest manmade object in the world is the Parker Solar Probe. It is a NASA space probe launched in 2018 to study the outer corona of the sun. It is expected to be the first ever mission to enter into the Sun’s atmosphere on 2025. When closest to the Sun, it is set to travel at 430000MPH which is about 0.0006 times the speed of light! It will be able to achieve this speed due to the immense gravitational pull of the Sun.

NASA's Parker Solar Probe

Practically it is impossible for anything with mass to travel with the speed of light with our current technology. This is because as speed of an object increases the mass of the object increases. Therefore, inertia increases and more force and energy are required for the mass to be accelerated further. Interesting theories and ideas have been formed over the years to try and prove otherwise. One of the classical examples is where you shine a laser at the moon. If you can flick the beam across the moon surface in less than 1/100th of a second, that beam would travel faster than the speed of light. Unfortunately, the theory doesn’t hold good as the beam is still travelling to the moon at the speed of light. The laying down of that laser is just an illusion.

There might be a way!

Well, there might just be one way to travel faster than the speed of light. Einstein in his general theory of relativity predicted the existence of wormholes, a kind of shortcut through space covering billions of light years in mere seconds caused due to the space time warpage. We haven’t found any wormholes yet, but who knows, maybe a wormhole is the way we can finally travel faster than the universal speed limit!