We use the word universe very often with different meanings. I think, when we think about its meaning, it is possible to understand better why we use it so often… The real meaning of the word and its scientific meaning is that which includes space, time, space, matter and energy; we can say that it is the structure that covers all celestial bodies and everything that exists.
In other words, everything from you, me and the internet, from the place you sit on to the stars that you can’t see at night but can only imagine, is a part of the universe. So if we were to get away and look at the universe from an angle where we could see the whole of it, what shape would we see? Is the universe spherical like a planet or star? Or is it flat like a piece of paper? Maybe it’s neither…
It is difficult to find the shape of the universe when you cannot and will never be able to see the whole universe, and some question marks arise from time to time.
The question of what the shape of the universe is is a compelling subject that has been researched for many years, calculated and examined with various data. Because the universe is so big that we can only observe a very small part of it.
In fact, if you are interested in these issues, you may have heard of the definition of the ‘observable universe’ that you often come across. So there is a part of the universe that we can never observe. Why? Because the universe is constantly expanding and there will come a moment when we will be so empty that we can’t see anything around when we look from the world…
As you can imagine, it is very difficult to determine the shape of a structure with such a size that it is impossible to observe. Fortunately, some scientific methods make this relatively easy.
What could the shape of the universe be?
Science has three basic options for this question;
- It can be as flat as a piece of paper.
- It can be in the form of a sphere, with a positive curve.
- Like a horse’s saddle, it can have a negative curve.
Why does the shape of the universe have to be one of these three? you may be asking. This is where general relativity comes into play. According to general relativity, mass bends the space-time structure, and the shape of the universe becomes related to the amount of mass it contains and the naturally applied gravitational force.
We can also say: How much does the density of all the energy and matter in the universe bend the universe, and what happens if it tilts? The answer to this question reveals the three options we listed above.
Now that we’ve learned about the options, what do these options mean?
What exactly does it mean for the universe to be flat, spherical, or saddle-like? Let’s briefly explain the question;
Imagine two rockets starting to fly side by side in the universe. If the universe is flat, these two rockets could continue to fly parallel to each other forever. In a closed sphere-shaped universe model, the two rockets will first move away from each other, but eventually return to where they started and meet again. In a horse-saddle-shaped universe, after a point, their paths will diverge and they will move forward forever, never meeting again.
Let’s come to the conclusion; What is the shape of the universe?
Scientists use data called cosmic microwave background radiation to understand the shape of the universe. We can explain this concept, whose name seems a bit confusing, as follows; When the universe first formed, it was very dense and hot. However, over time this situation changed, density and temperature decreased. As the temperature decreased and the intensity decreased, photons, the basic unit of light, became more mobile. It took 380,000 years for this to happen. The cosmic microwave background radiation is simply the ‘light’ that began its journey 380 thousand years after the big bang and reached us.
Determining how much this light deviated over 13.8 billion years, and calculating the intensity that caused the deflection, helps scientists determine the shape of the universe.
According to the data obtained and many calculations made over and over again, it is stated that the universe is flat/almost flat with very small margins of error. The rate usually given is that the universe is 99% likely to be flat.
In fact, another study published in the past years, again using cosmic microwave background radiation data, claimed that the detected deviations were so great that the universe was not flat, and that the universe could be a closed system in the form of a sphere. However, this different point of view was left behind when the flatness of the universe was again supported by different studies that followed.
Still, scientists are trying to solve many mysteries of the universe that we do not fully understand, such as dark matter and antimatter, and they say that the probability of the universe being flat is 99%, and they never ignore the possibility that it is not 1%.
What would happen if we knew the shape of the universe, what would happen if we didn’t…
Knowing the shape of the universe affects everything from the formation of the universe to its structure, to the answers to questions such as its end and beginning.
For example, as we explained above, if the universe were spherical rather than flat, everything would one day return to the point where it started. So maybe the universe that expanded with the big bang would be a small dot again… What does that mean? It’s hard to even imagine… In other words, the shape of the universe significantly affects the way we understand the universe. This gives scientists enough reason to know the correct shape.
Resources. Space.com/Paul M. Sutter, Dr. Eleonora Di Valentino, nature.com, phys.org, Scientific American, astronomy.com, space.org
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