What is the shape of our universe?

Space, as we know today, is generally thought of as a never-ending stretch of three dimensions extending towards infinity. This assumption is based on the fact that till date, we haven’t discovered any “end” or corner of space. However, several theories not limited to general theory of relativity ( which describes gravity as a curvature of space and time caused due to mass and energy), shakes the very foundation of such statements making us question whether our reality is somewhat more complicated that we were led to believe .

Science has achieved a lot over the past years on both ends of the cosmic scale. At the lowest known end of the scale of existence, lies the quantum world where strange laws govern various aspects of particles inside an atom. On the other end lies numerous galaxies dwarfing the largest stars spread across billions of light years and more! But,what lies beyond the known expanse of the universe? How would the universe containing so many galaxies and stars, look like if we could step out the three dimensional frames?

By understanding smaller parts of a system, we could infer a lot about it.Take the example of how earth’s shape was finally understood after decades of debate and controversies.

HOW EARTH’S SHAPE WAS UNDERSTOOD

It is a well known fact that Portuguese explorer Ferdinand Magellan circumnavigated the globe for the first time, empirically discrediting the flat earth theory. Yet, the fact that our earth is spherical, was proposed(and perhaps understood) long before Magellan’s time(almost 2000 years ago) by observing the curved path traced by the sun from sunrise to sunset. In fact, this observation was consistent all year round, except of course the length of path which varied according to the season. During summer, it took a longer path than in winter. In essence, although we weren’t technologically equipped to take picture perfect satellite images of our planet, many a scientist and explorers could sense that the visible part of earth;s surface was in fact, a part of some curve.

pinholecamerajd09
The above image shows the paths traced by the sun throughout a year. The steepest arc is that of summer solstice, while the lowest one is of winter solstice.

 

VAST NATURE OF REALITY

In discussing the events that led to discovery of our planet’s shape, we can infer that it gets increasingly difficult for our brains to comprehend the nature of things that are way larger than us. When compared to the milky way, our earth is practically invisible. To understand the nature of things way beyond the three axes is to stretch our brains to incredible proportions. Lucky for us, we aren’t the first to ask such question and while, we can’t state with certainty, scientists managed to come up with some pretty decent theories that is sure to give us some food for thought even if it doesn’t convince us completely.

WHAT GENERAL RELATIVITY HAS TO SAY

One of the most important theories of science – general relativity has helped us explain a lot of things, which wasn’t possible previously. One of the many consequence of this theory is our understanding of gravity, previously thought of as nothing more than an invisible entity binding two celestial bodies in space. Relativity considers gravity as a curvature of space-time, which not only simplified our understanding of it, but also revealed the close link between space and time. (While they cannot be interchangeably used, time when considered as fourth dimension speaks volumes of the fabric of reality we exist in.)

Ever since the Big Bang, our universe has been expanding and celestial bodies seem to be moving away from one another. An important factor that determines whether or not our universe will expand, stop or even reverse, is known as the critical density. Without going much into the details, let’s just say – it is the density at which expansion will cease.  The definitive nature of critical density  gives rise to three possible cases, one of which is  the shape of our universe.

end_of_universe
Three possible shapes of our universe

Case I :

Ωo > 1 implies that the actual density is greater than the critical density. In this case, our universe would be a perfect sphere and the expanding universe would eventually collapse into itself (opposite of Big Bang) and is known as the “Big Crunch”.

Case II:

Ωo < 1 implies that the actual density is lower than the critical density. In this case, our universe would be a hyperbolic and it wont contain enough mass to stop the expansion.

Case III:

Ωo = 1 implies that the actual density is equal the critical density, in which case our universe is flat and infinite, as it was thought of, previously.

 

CONCLUSION

Our universe is ever expanding. There exists corners of space so far away from our home planet, that not even light with it’s incredible speed, has managed to reach the lenses of camera despite having started its journey billions of years ago. Distances this large is incomprehensible and way beyond the capabilities of even the best pieces of technology available. As of now, we can merely speculate and come up with theoretical methods that can be adopted to draw conclusions regarding the universe at such a large scale. Thus, we are in several senses of the phrase, “light years” away from understanding it.

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