My Essay (Part VI) - The Expanding Universe

The analogy of an expanding universe. X and Y arrows are the visual representations of a flat space and T arrow follow the forward timeline. As seen, the space is getting bigger with time and the spiral galaxies within gets further apart from each other. (Free Source)

When Einstein finished his seminal paper, he, just like Isaac Newton, believed in the static universe. That is the volume, or space in this universe is neither expanding nor contracting. He believed that the size of the universe is as it is throughout its existence. Strangely, his formulations in General Relativity predicts that the universe should be either expanding or contracting. Hence, he introduced a modification to his original paper called the cosmological constant to keep the universe static.

A ground breaking discovery was made in 1929 by a prominent American astronomer, Edwin Hubble. Using a powerful telescope, he discovered that there are other galaxies, which are huge collections of stars outside of our massive Milky Way galaxy and what is strange is that these small specks of light emitting from stars very far away appear to be moving away from us! No matter which part of the sky we look at, all the distant galaxies appear to be moving away from our view. This could only mean one thing – the space between the galaxies is getting larger making the galaxies further apart from each other. One way of viewing this is by marking ink dots on a deflated balloon. When you blow air into the balloon, the surface expands causing the distance between the dots to increase. The ink dots represents the stars and this is the analogy of stars moving away from each other due to the expanding universe.

"[If the redshifts are a Doppler shift] … the observations as they stand lead to the anomaly of a closed universe, curiously small and dense, and, it may be added, suspiciously young. On the other hand, if redshifts are not Doppler effects, these anomalies disappear and the region observed appears as a small, homogeneous, but insignificant portion of a universe extended indefinitely both in space and time." - Hubble, Edwin, Monthly Notices of the Royal Astronomical Society, Vol. 97, p.506,The SAO/NASA Astrophysics Data System

Obviously mistaken, Einstein called the Cosmological Constant his biggest blunder and accepted the fact that the universe is expanding after this groundbreaking discovery. Seeing that the universe is expanding has another implication, which means the universe was a much smaller place in the past. Using precise measurements, scientist are able to compute how much time it was when the universe back then was infinitely small, infinitely dense and infinitely hot – a universe smaller than the size of an atom containing everything we see, touch and sense, in a history about 13.4 billion years ago.

My Essay (Part V) - Gravity by Einstein

First page of Einstein's manuscript, explaining the idea of general relativity and gravity.

(Public Domain: US)

The problem was planet Mercury. By the late 19th century, astronomy has developed to measure the orbit of mercury so precise that they realise the orbit did not follow Newton’s law of gravitation. Instead of a steady elliptical orbit, it went through another movement we call precession. The elliptical orbit of mercury didn’t stay in place but changes it position where the long axis of the ellipse will rotate the sun at about one degree in ten thousand years. That means the elliptical orbit changes position to form a huge circle that completes a turn in 3.6 million years.

Here comes a man to rescue – Albert Einstein. Einstein published his paper called “General theory of Relativity” in 1915 that radically redefined gravity. He made the revolutionary suggestion that the very fabric of space and time itself is “bent” or “curved” in the presence of a massive object. He proposed that the physical quantity of space and time are intimately connected. The idea that space and time itself are interconnected is actually not so strange when you think about this: When you have a date with someone, you must know about the location and time. There is simply no point telling your date about the place to meet up but not the time. So, one can now think that space and time is “woven” like a fabric because each event is linked to a specific time and space.

To demonstrate how General Relativity works require a little imagination. Here is an analogy - Picture the fabric of space-time as a thin sheet of rubber. Now we pull the four edges of the sheet and lift it up from the ground. What you see is a “flat” space where space-time is uniformly spread. Now, throw a bowling ball onto that rubber sheet and you’ll notice the ball sinks into the sheet of rubber, curving the surface of the rubber sheet. Now, roll a marble towards the bowling ball and you’ll see the marble traveling in a straight line and as it approaches the bowling ball, its path will curve towards the bowling ball, circulating it before it finally sticks to the bowling ball and stop.

What you’ve just pictured was the analogy of how gravity works in General Relativity. The bowling ball represents a massive object (like the sun) and the marble on the other hand, is a less massive object (earth) orbiting it on the curvature of space-time. Now you must be thinking “How is the marble orbiting the bowling ball? Because the marble will roll closer to the bowling ball and eventually stops.” The reason is because there is the presence of frictional force between the rubber sheet and the marble. Theoretically, if we remove the friction factor (which means we are having perfect lubrication between the marble and the rubber sheet), inserting the marble in a correct angle and we will observe the marble orbiting the bowling ball forever and ever in a circular orbit. So, essentially, mass is able to bend the structure of space and time itself and the consequences are the effects of gravity. Now with Einstein’s view of gravity, the problem in physics specifically the analogous orbit of Mercury can be explained.

The effects of Special Relativity

I'll explain about the cause for odd effects of relativity soon. Stay tuned!

How elegant is our Universe?

Negative from the 1919 Eddington's experiment proving gravity does indeed bend light rays.

As Einstein’s general relativity is finally proven experimentally by Sir Eddington’s expedition in 1919, the good news spread like wild fire. A student asked Einstein what if Eddington’s experiment has not found the prediction of his theory (the bending of starlight due to a massive body). Einstein replied:

“Then I would have been sorry for the dear Lord, for the theory IS correct.”

Of course, if the theory was disproven by the experiment, his theory of relativity will not become a pillar for modern physics as we know it.

What Einstein meant was general relativity describes gravity with such a deep inner elegance, with such simple yet powerful ideas, that he finds it hard to imagine that nature can just pass it by. General relativity, in Einstein’s view, was almost too beautiful to be wrong.


In physics, as in art, symmetry is a key part of aesthetics. Physicists describe the two properties of physical laws – that they do not depend on when and where you use them – as symmetries of nature. For example, the physics laws applies on the surface on the earth, applies exactly the same on the moon, on mars, on the edge of the galaxy and so on. By this usage physicist means that nature treats every moment in time and location in all of space identically – symmetrically – by ensuring that the same fundamental laws are in operation. Much in the same way that symmetries affect art and music, such symmetries are deeply satisfying; they highlight an order and coherence in the workings of nature.


The elegance of rich, complex, and diverse phenomena emerging from a simple set of universal laws is at least part of what physicist mean when they invoke the term “beautiful”.


-Adapted and edited from The Elegant Universe by Brian Greene.