Aleksandr Friedmann believed that the general theory of relativity required a theory of the universe that was in motion. At the time Einstein proposed the general theory of relativity, many believed that the universe was static. It would be Friedmann who would suggest that the universe was created by a “big bang,” which was then followed by a rapid expansion.
According to Friedmann, the universe would then experience a contraction and eventually a “big crunch” as everything came back together. The original universe theory by Friedmann suggests a closed universe model where entropy will eventually cause it to die. He also suggested that the universe could be open, expanding infinitely, or that it could be flat and expansion would eventually approach a rate of zero.
Friedmann shared his calculations with Einstein, who thought that the expanding universe solution was originally erroneous. They would later come to an agreement and Edwin Hubble would help to confirm the observations in 1929.
Alexandr Friedmann would have his life cut short due to typhoid fever and he would die at the age of 37 before his theories were confirmed.
How the Friedmann Universe Theory Works
The development of the Friedmann universe theory begins with equations that start with a simplified assumption that the universe is isotropic and homogenous spatially. It must be a three-dimensional metric that includes flat space, a sphere of constant positive curvature, or a hyperbolic space with constant negative curvature.
The equations show that the geometry of the universe is determined by the overall density of mass and energy. If it is equal to the critical density in the equations, then the universe would have zero curvature. That’s the flat universe alternative that Friedmann suggests. If it is less than critical, then the curvature is open. If it is greater than critical, which is the option that Friedmann preferred, then it offers a closed configuration.
This means the universe is potentially dynamic. The size of the universe may change over time. This theory was the first to suggest the term “expanding universe.” It also means that the structure of the universe could have been born from one lonesome singularity.
Hubble and a Belgian physicist, Georges Lemaitre, discovered that when a galaxy is far away, its light is shifted to lower frequencies. The further away the galaxy happens to be, then the greater the shift in frequency. This occurs because the expansion of the universe causes emitted light to be stretched out in its frequency as it travels to our location.
That creates a new question: if the universe is indeed expanding, then what is it actually expanding into?
What the Friedmann Universe Theory Suggests
Because of our planetary perspective, we think of space and distance as being rigid measurements. When we apply that perspective into special coordinates, we think of the distance between our solar system and any other location in the universe as having a fixed distance. Einstein tells us in the theory of general relativity that this isn’t actually true.
The universe has the ability to bend, to stretch, and to even wrap around itself if it wished to do so. That means our universe is not necessary expanding into anything. It is the actual space within the universe, the distance that occurs between two points, that is actually expanding over time, though that applies on a macro scale where gravity has less of an influence.
The voids between galaxies are believed to have little or no influence from gravity. That is what allows the expansion of distances to occur. Within a galaxy cluster, however, gravity stops the process of expansion from occurring.
Think of the universe as if it were a balloon. We are on one point of the balloon. As it expands when air is blown into it, the shape of the balloon changes. What was once close to our starting point is now further away, but we are still on the balloon itself. Add more air and the distance becomes further and further apart. If you travel in any one direction, however, you will eventually come back to your starting point.
Yet when you blow up a balloon, its expansion takes up space. It becomes “larger.” Yet, at the same time, your house does not get larger when you blow up a balloon. The surface of the balloon expands, but what lies outside of the surface of the balloon does not. What could lie outside the universe?
That brings up the question of “Hubble Volume,” or what lies beyond our current perspective. Does the universe have a “boundary surface” like the exterior of a balloon which can hold air? And what would happen if a rupture occurred in that surface?
Data observed in 2008 and confirmed in 2010 called Dark Flow suggest that something outside of our universe could be exerting gravity on our universe. Evidence shows that galactic clusters are all streaming in the same direction at immense speeds, which defies how the distribution of mass throughout the universe should operate from an explosive singularity.
Yet, at the same time, if something is outside of the Hubble Volume, it is still within our universe. If air comes out of a balloon, it is still air within our home. It may seem different, but it really is still the same.
What Does the Universe Theory Means for Us Today?
One of the greatest debates about our existence is how the universe initially formed. We have holy books tell us of creation. We have scientists who discuss evolutionary processes. Matter came from a singularity or it was created by a divine being or it happened for an unknown reason.
Humanity tends to argue with itself over opinion instead of focusing on fact. The universe theory is just an idea, but it is one that has some confirmed principles. We argue over those principles because we want belief systems to be validated.
What Friedmann offers us is a glimpse into those belief systems, no matter what they may be. For those who focus on creation, Friedmann offers the idea of an active God in an expanding universe creating a supportive system for life. For evolutionists, Friedmann offers a doorway which suggests natural causes and systems that support our bubble of existence. In essence, what separates perspectives is what draws people together.
Perhaps that is the best outcome of the Friedmann universe theory. The flexibility of space and the universe as a whole allows for shifting perspectives. Instead of there being a constant “right,” there is what is “right” in this moment. Shifts and changes can create new structures, new curvature, and new perspectives. Maybe the distance does grow further with expansion, but that doesn’t change the fact that the journey is still present.
The universe is not constant. That is the primary observation we get from the Friedmann universe theory. Beyond that one point of common ground, the rest may be open to interpretation – and there is nothing wrong with that.