Einstein's Theory of Relativity

This episode explores Einstein’s theory of relativity. As we move forward in this series, you’ll notice that one of the most profound bridges between Vedantic philosophy and modern science lies in grasping the essence of Einstein’s ideas. To facilitate this connection, it’s important to first acquaint ourselves with the concepts of relativity. In this episode, we’ll unpack these ideas in a straightforward, accessible manner, ensuring clarity for all, regardless of your background in science.

Albert Einstein is the best-known scientist in the modern era. His contribution to science is immense. He is famous for presenting the following two theories:

One - Theory of Special Relativity

Two - Theory of General Relativity

We will discuss these two theories in this episode. 

Transcript

Hello and welcome to Science Meets Vedanta - a space where we explore the fundamental principles of Vedanta and unravel the profound intersections between scientific inquiry and ancient wisdom. I'm Jayant Kapatker, the author of the book - Science Meets Vedanta.

Drawing from the insights in this book, each week we’ll explore a variety of topics designed to help you understand the essential teachings of - Vedanta. Along the way, we’ll highlight valuable lessons that science can gain from Vedantic wisdom, so stay tuned!

Today’s episode explores Einstein’s theory of relativity. As we move forward in this series, you’ll notice that one of the most profound bridges between Vedantic philosophy and modern science lies in grasping the essence of Einstein’s ideas. To facilitate this connection, it’s important to first acquaint ourselves with the concepts of relativity. In this episode, we’ll unpack these ideas in a straightforward, accessible manner, ensuring clarity for all, regardless of your background in science.

Albert Einstein is the best-known scientist in the modern era. His contribution to science is immense. He is famous for presenting the following two theories:

One - Theory of Special Relativity

Two - Theory of General Relativity

Einstein’s theory of relativity transformed our understanding of space, time, and the interconnectedness of all things in the universe. 

Fun fact: In 1921, Einstein was awarded a Nobel Prize for his discovery of the “photoelectric effect” phenomenon, which showed that light is a particle. It is surprising that he was awarded the Nobel Prize for this discovery and not for the Theory of Relativity, for which he is better known.

1 - Theory of Special Relativity

The Theory of Special Relativity, first introduced in 1905, revolutionized our understanding of how objects move at constant speeds. Traditionally, we believed that space and time were absolute—unchanging and fixed, like the steady ticking of a clock or the immutable size of a space. Special Relativity shattered this notion, revealing that both time and space can be affected by motion. In other words, how fast something is moving can influence the flow of time and alter the very dimensions of space itself. This realization has fundamentally changed the way we view the universe. Without delving too deeply into technicalities, let’s explore this groundbreaking theory by connecting three key ideas:

1 – The relationship between motion and space

2 – The relationship between motion and time

3 – The interplay between space and time

1. The relationship between Motion and Space 

There is a connection between motion and space. Whenever there is motion, space contracts. Yes, motion influences space. This is not an easy concept to grasp. We are so used to seeing space that we think it is unchanging. All this happens because the speed of light is fixed at 186,000 miles per second, irrespective of the frame of reference.

Let us understand the basics of this theory. We all experience relative speed. Going in a car at 60 miles per hour, we look into another car traveling in the same direction at 55 miles per hour, and we see things inside the other car because the relative speed is only 5 miles per hour.

Imagine yourself aboard a rocket hurtling through space at a speed of 120,000 miles per second, while a particle of light travels alongside you at its standard velocity of 186,000 miles per second. Intuitively, you might expect that, from your perspective within the rocket, light would appear to move away from you at only 66,000 miles per second—the difference between your speed and that of light. However, upon measuring the speed of light from your rapidly moving vantage point, you discover something astonishing: the light still races at 186,000 miles per second, not the 66,000 miles per second you anticipated.

How can this remarkable phenomenon be explained? Logic suggests that, given your rocket’s immense speed, light should traverse only 66,000 miles of space each second relative to you, yet it steadfastly covers 186,000 miles every second. This apparent contradiction lies at the heart of the theory of special relativity. The solution is both subtle and profound: to reconcile these observations, the very notion of distance must adapt. In effect, the length of a mile contracts so dramatically that 186,000 “miles” of space can be compressed into what would otherwise be just 66,000 miles. Thus, space itself shrinks—undergoing what’s known as length contraction—when you travel at such extraordinary speeds. You in the rocket will not notice any space shrinkage and light is still travelling at 186,000 miles per second.

Imagine increasing the rocket’s speed to 150,000 miles per second. Intuitively, you might expect the relative speed of light to drop to 36,000 miles per second. Yet, if you measure the speed of light from aboard the rocket, it remains steadfast at 186,000 miles per second. To account for this, space itself must contract even further so that 186,000 miles’ worth of spatial distance can fit into just 36,000 miles. This is demonstrating that the faster an object moves, the greater the degree to which space contracts.

Now, consider what happens if the rocket reaches the speed of light. In this scenario, there is no relative motion between the rocket and a particle of light. The contraction of space becomes so extreme that space effectively vanishes; space simply ceases to exist at light speed. This is a profound and astonishing implication of the theory of relativity.

This contraction of space also happens even when walking or running. However, the speed at which you walk, or run is so slow when compared to the speed of light that you are unable to notice the difference—but changes to the space framework are occurring.

This would mean that each person creates their own space framework. Person A is sitting in a chair, Person B is walking, Person C is running, Person D is cycling, and Person E is driving a car; all of them are moving at different speeds. Since the motion speed is different, the space contraction is different for each person. The space framework is different for each person. It is counterintuitive. It shows that each of them will have their own separate and independent space framework. This means each living being in the universe has their own framework of space. 

This entire universe is based on relative motion as we just cannot find anything which is fixed. We are walking on Earth; Earth is moving around the sun; the sun is moving in the Milky Way; the Milky Way is moving farther away from other galaxies. The relative motion keeps changing. This means that the framework of space will constantly change with motion.

The speed of light is always fixed at 186,000 miles per second, but the framework of space is never fixed. It is different for each living being and keeps changing with the speed of motion.

The relationship between motion and time 

To explain the connection between motion and time, Einstein provided a thought experiment.

Imagine you stand on Earth, while your twin embarks on a cosmic journey in a rocket, both equipped with precision atomic clocks. The rocket soars at an astonishing 80% of light's speed. When you measure the speed of light from your station on Earth, your instruments read 186,000 miles per second. Curiously, your twin, hurtling through space at breakneck velocity, records the exact same value—186,000 miles per second.

How is this possible? The answer lies in the remarkable principles of relativity: while the speed of light stays unwavering for both observers, space and time themselves become malleable. Inside the rocket, your twin's clock ticks more slowly, and distances compress, all conspiring so that the measured speed of light never wavers. Though time for your twin moves at a gentler pace, the velocity of light remains universal—186,000 miles per second—unchanged by either journey or perspective.

Imagine your twin sibling returns to Earth after a journey through space. According to your clock, their trip lasted ten years. However, when you check your twin’s clock, it reveals only six years have passed for them. Astonishing as it may seem, the passage of time is not the same for both of you—your clocks have ticked at different rates. This means that you and your twin have actually aged differently, all because of differences in motion and speed.

Imagine your twin embarks once more on a cosmic journey, this time accelerating to an astonishing 99.99% of the speed of light. Despite his incredible velocity, when he measures the speed of light, he discovers it remains steadfast at 186,000 miles per second—just as you would observe it from Earth. Time, however, behaves quite differently for him. His clock ticks very slowly, crawling compared to your clock here on Earth. After what feels like 50 days to him, he returns home; yet when for you a full decade has elapsed. 

This clock ticking at different rates also happens even when walking or running. However, the speed at which you walk, or run is so slow when compared to the speed of light that you are unable to notice the difference, but changes to the rate of time are happening. It is impossible for any living being to notice this small unit of time. Even for the smallest change in speed, the rate of time does change. Motion has an influence on time. With motion, time slows down. 

3. The Interplay between space and time

We have just seen that motion influences both space and time. Wherever there is motion, space contracts and time slows down. Does that mean that space and time are connected? Yes, they are. Einstein made this connection by coining the term “spacetime.” Space and time are two sides of the same coin. When you look at space in terms of distances, it is space. However, when you look at the same space in terms of time, that space is spacetime.

This spacetime is a fabric made of time. In space you measure distances. The sun is 93 million miles away; the tree is 500 feet away. In spacetime you measure everything in time—the amount of time light takes to reach us. The sun is eight minutes away. Different objects are so many seconds away from you. The distant star is five million light-years away.

2. Theory of General Relativity

The Theory of Special Relativity addresses objects moving at constant speeds, but it does not account for acceleration or the effects of gravity. These aspects were absent from Einstein’s initial theory. To address this gap, Einstein introduced the Theory of General Relativity in 1915, expanding the framework to include acceleration. It’s important to recognize that gravity itself is a form of acceleration.

Acceleration represents a specific kind of motion in which an object’s speed increases—potentially doubling every second. This rapidly changing speed raises intriguing questions about its effects on space and time. Previously, we learned that as an object’s speed increases, time slows down and space contracts. When acceleration is involved, and the speed doubles each second, these effects on time and space also intensify, with time slowing and space contracting at a doubled rate.

Mathematically, this scenario reveals a profound insight: whenever acceleration is present, it causes the spacetime fabric to curve. The greater the acceleration, the more significant the curvature—or “dip”—in spacetime. Thus, General Relativity shows that both acceleration and gravity warp the geometry of spacetime, fundamentally shaping our universe.

Another consequence of this theory is that the presence of matter causes time to slow down. This effect is illustrated by the bending or curving of the spacetime fabric around objects. The greater the mass, the more pronounced the curvature becomes. Not only do planets and stars influence spacetime in this way—any object with mass, regardless of size, will cause time to slow and spacetime to curve. However, for objects with small mass, the curvature—and thus the effect on time—is negligible.

Drawing on the discussions throughout this episode, we arrive at several foundational conclusions. These insights will serve as recurring pillars in upcoming episodes, making it worthwhile to keep them in mind:

1 - Constancy of Light Speed: The speed of light remains constant at 186,000 miles per second, unaffected by the observer’s frame of reference.

2 - Spatial Contraction: Motion causes space to contract; the greater the speed, the more pronounced the contraction. At light speed, space ceases to exist altogether.

3 - Temporal Dilation: Time slows down as motion increases. The faster the movement, the slower time passes, until—at the speed of light—time itself comes to a halt.

4 - Energy’s Effect on Time: The presence of energy also slows the passage of time; higher energy results in slower ticking of the clock.

We hope today’s episode has sparked your curiosity and offered valuable insights into the theory of relativity. If you’d like to dive deeper, visit our blog at Vedanta and science.com or find my book, Science Meets Vedanta, on Amazon. Be sure to subscribe so you won’t miss upcoming episodes. If you enjoyed this episode, please share it with your family and friends. Thanks for joining us—see you again soon!