About a century ago, scientists found it difficult to reconcile what seemed a contradiction Albert Einstein’s theory of general relativity.
Posted in 1915And already widely accepted worldwide by physicists and mathematicians, the theory assumed that the universe was static – immutable, motionless and immutable. In short, Einstein believed that the size and shape of the universe today were, more or less, the same size and the same shape it had always been.
But when astronomers looked at the night sky with distant galaxies with powerful telescopes, they saw clues that the universe was anything but that. These new observations suggested the opposite – that it was, Instead, the expansion.
Scientists quickly realized that Einstein’s theory did not really say that the universe should be static; The theory could also support an expanding universe. Indeed, using the same mathematical tools provided by Einstein theory, scientists created new models that showed that the universe was, in fact, Dynamic and scalable.
I spent decades trying to understand general relativityincluding in my current work As a physics teacher teaching lesson on the subject. I know that getting around your head around the idea of a constant expansion universe can feel intimidating – and part of the challenge is to replace your natural intuition on how things work.
For example, it is difficult to imagine something as big as the universe that is not at all a center, but physics says it is reality.
https://www.youtube.com/watch?v=BBKV2N550X FrameBorder = “0 ″ ALLOWFULSCREEN =” ALLOWFULLSCREEN “>Space between galaxies
First of all, let’s define what we mean by “expansion”. On Earth, “developing” means that something becomes greater. And with regard to the universe, it is true, in a way. The expansion could also mean “everything goes further from us”, which is also true with regard to the universe. Point a telescope with distant galaxies and they all appear To get away from us.
In addition, the further they are, the faster they seem. These galaxies also seem to move away from each other. It is therefore more precise to say that everything in the universe further from everything elseeverything at once.
This idea is subtle but critical. It is easy to think of the creation of the universe as fireworks that explode: start with a big bangThen all the galaxies of the universe fly in all directions from a central point.
But this analogy is not correct. Not only does this wrongly imply that the expansion of the universe began from a single place, which has not done so, but it also suggests that galaxies are the things that are moving, which is not entirely exact.
It is not so much the galaxies that move away from each other – it is the space between the galaxies, the fabric of the universe itself, it is constantly expanding over time. In other words, it is not really the galaxies themselves that move into the universe; It’s more than The universe itself Takes them further as it expands.
A common analogy is to imagine sticking points on the surface of a ball. When you blow the air in the balloon, it develops. Because the points are stuck on the surface of the ball, they separate further.
Although they may seem to move, the points remain exactly where you put them, and the distance between them is simply growing due to the expansion of the ball.
Now consider the points as galaxies and the ball like the fabric of the universe, and you start to obtain the image.
Unfortunately, although this analogy is a good start, it does not get the details either.
The 4th dimension
Understanding its limits is important for any analogy. Some faults are obvious: a ball is small enough to hold in your hand – so not the universe. Another defect is more subtle. The ball has two parts: its latex surface and its interior filled with air.
These two parts of the ball are described differently in the language of mathematics. The surface of the ball is two -dimensional. If you were walking on it, you can move forward, back, left or right, but you could not go up or down without leaving the surface.
Now it may seem that we are named four directions here – forward, back, left and right – but these are just movements along two basic paths: side by side and front on the back. This is what makes the surface two -dimensional – length and width.
The interior of the balloon, on the other hand, is three -dimensional, you could therefore move freely in any direction, including at the top or bottom – length, width and height.
This is where confusion resides. The thing that we consider to be the “center” of the ball is a point somewhere in its interior, in the space filled with air below the surface.
But in this analogy, the universe looks more like the surface of the balloon latex. The interior filled with balloon air has no consideration in our universe, so we cannot use this part of the analogy – only the surface counts.
So asking: “Where is the center of the universe?” Is a bit like asking: “Where is the center of the ball surface?” There is simply none. You can travel on the surface of the ball in any direction, as long as you wish, and you never reach a single place once, you could call its center because you would never leave the surface.
In the same way, you can travel in any direction of the universe and would never find its center because, just like the surface of the ball, it Just don’t have it.
Part of the reason why it can be so difficult to understand is because of how the universe is described in the language of mathematics. The surface of the balloon has two dimensions, and the interior of the ball has three, but the universe exists in four dimensions. Because it is not only the way things move in space, but how they move over time.
Our brains are wired to think of space and time separately. But in the universe, they are intertwined in a single fabric, called “space-time. “This unification changes the functioning of the universe in relation to what our intuition expects.
And this explanation does not even start to answer the question of how something can extend indefinitely – Scientists always try to remove what feeds this expansion.
So, by asking questions about the center of the universe, we confront the limits of our intuition. The answer we find – everything, developing everywhere, suddenly – is an overview of how our universe our universe is strange and beautiful.
Rob CoyneProfessor of physics teaching, Rhode University
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