mixture

An Epitome of Relativity

“There was a young lady of Wight
Who travelled much faster than light
She departed one day
In a relative way
And arrived on the previous night.”

From this limerick you can guess what is going to be in the article. We are now diving into the great paradigm shift of modern physics which will start of from the anomalies in the behavior of light to the new understanding nature of light and space-time. The theory of Relativity. The measure intellectual revolution that has transformed the way of thinking about universe. The theory not only talks about curved space but also curved or warped time as well.
Einstein once quoted that ‘ for the rest of my life I want to reflect on what light is’. So, let’s sit on the beam of light and start our journey into strange form of reality!

Before directly hit into Relativity, let’s first understand what space and time actually is.
Space is what we speak of when we ask “Where?”, Time is what we speak of when we ask “When?” If I ask, “Where are you?”, a possible answer might be “at home”. If I ask “Where is Mumbai” a possible answer is “it’s in Maharashtra, India.” Now if I ask ” When do you meet” the answer would be “at 5 PM “. So when you want to meet someone, you need to give both space and time details for that meeting to take place. “We will meet at 5PM in Cream Cafe, Mumbai “, to define your position of your event you need this entities, space i.e. X,Y,Z dimension and Time as fourth dimension. Thus one can think that space and time together as a four-dimensional entity called Space-time. Each point of space-time is labelled by four numbers that specify its position in space and in time.

Before Einstein, everyone understood the universe in terms of Newton’s three laws of motion. Classical physics which said Laws of physics were same for everyone and time is constant entity anywhere in the universe. But Einstein was troubled by this. He began thinking of behavior of light. He did a “thought experiment” and this led him build the foundation of special theory of relativity. Accordingto Newton, space and time was absolute but if someone attempts to synchronize the clock with the one that is moving, light would have to speed up or slow down to keep the clock synchronized. But James Clarke Maxwell said that light only moves at one speed. Now either Maxwell is correct or Newton is, but it can’t be both! This thought intrigued Einstein and result of this he put his own theory of “special relativity” ahead.

In Einstein’s special train example, the light from bolt A will arrive at Train(x) before that from bolt B. Hence Train will observe the lightning at A as happening before that at bolt B. Man(Y), however, will observe the bolts of lightning to be simultaneous. An example of how observations from reference frames moving at great speeds relative to each other reveal a different timing of events.

Imagine you are standing at railway station. Now imagine a train racing very fast in front of you, faster than any train you’ve ever seen. Now as the train is flying past, two lightning bolts crashing beyond the tracks in the sky at the same time 100 meters apart. From railways station where you are standing still, these two lightning bolts crashing simultaneously. Now imagine you are standing at the middle of the train during the exact same scenario of bolts. Would the lightning bolts be simultaneous? If you look closely, they aren’t simultaneous! Because you are moving towards one and away from the other. You’re not still, you are moving. How could one experience this same event differently? Because, Time is not absolute! It varies according to your frame of reference. Time is relative! It flows differently according to the state of motion and so that distance is also relative.

One of the most famous equations in physics also comes from special relativity. The equation “E= mc^2” – means ‘energy equals mass times the speed of light squared.’ This equation is demonstration for ‘why atomic bomb is so powerful’, when its mass converted into an explosion.

This equation also shows that speed of light(c) is the fastest velocity at which an object can travel. As object moves, its mass also increases and near the speed of light, the mass is so high that it reaches to infinity and would require infinite energy to move it. Thus putting the limits on how fast things can move. This conclusion also ruled out the time travel in the past. But wait, we have other ways, according to our current understanding, time travel can’t be ruled out. There’s a hope in M-theory!
Another strange conclusion of Einstein’s work from the realization that time moves relative to the observer. Time dilation. Moving object experience the time dilation. For the one who is moving, time moves more slowly than the one who’s standing still. This becomes extremely apparent when one approaching the speed of light. If 15 year old kid is traveling at 99.5% the speed of light for 5 years. When this 15 year kid came back to Earth, he would be only 20 years old but his classmates would be 65 years old. This phenomenon is practically tested with the astronaut revolving aboard space station, who aged slowly than his twin brother on Earth who aged little faster!

This is how physical world behaves! Though it looks weird but it has measured proofs. We think time is something we know about instinctively but actually, its a profoundly strange in reality!