How String Theory Reveals the Multiverse

Atoms are made of protons, neutrons and electrons. And they are small. So small that 100 million hydrogen atoms would span the width of your fingernail. String theory proposes that at the most fundamental level of space there are objects that are much smaller than these elementary particles: tiny little filaments of energy, called “strings.”

String theorists believe that these strings are the smallest possible entities that can exist. Their size is called the “Planck length,” the smallest unit of measurement that can exist in this universe. Here’s how small a string is: A string is to a hydrogen atom in size as a hydrogen atom is to the entire universe!

A Multitude of Universes

The photo at the top of this article shows a type of maze or labyrinth, through which matter can enter, move about and exit. The paths that it can take through a particular labyrinth is determined by its shape.

We can only experience the three dimensions of length, width and height. String theory proposes that the space in which the strings vibrate and move about, consists of six additional “curled up” tiny dimensions. The vibrating strings are constrained to move only in certain paths by the way the six hidden dimensions are organized.

The tiny curled-up dimensions can assume many shapes, creating a unique labyrinth that controls the motions of the strings. And those motions of the strings determine the nature of our universe: the constants of nature and the forces that govern their behavior.

In the early years of string theory, physicists thought they were only a few possible shapes for these labyrinths. As the years went on, scientists’ estimate of the number of possible arrangements of the curled-up dimensions started to increase exponentially.

Each arrangement of the six dimensions creates a unique universe.

String theorists now believe that there are a nearly infinite possible arrangements of the curled-up dimensions. If we wrote it out, it would be 1 followed by 500 zeros. This means that a gigantic number of these universes presently exist, and this number is increasing every second. These universes, of which our universe is only one, exist in a hyperspace called “the bulk.”

While this number is much smaller than infinity, it is still vast; more than all of the particles that make up our universe.

And the equations of string theory lead to the inescapable conclusion that all of these universes coexist.

What powers the creation of these multiple universes?

Did you ever wonder how the holes get into Swiss cheese? Carbon dioxide builds up inside the cheese and forms bubbles which grow, causing the holes. String theorists tell us that universes spontaneously appear to grow within a “hyperspace” they call “the bulk.”

An inexhaustible source of energy, called the “quantum foam,” powers this process. And it’s happening continuously.

I like to think of it as a gigantic hotel with 10 to the 500th rooms. Each room represents a unique universe. Open the door to the room numbered 2,345,677,009,567,212,333 and you may see a fiery furnace of a universe, in which no life forms can exist. The room next door is totally black. In this universe, the constants of nature and the laws of physics were such that no stars or galaxies were able to form. At least one of these rooms must contain a universe that is friendly to humans. We know this is true because we exist!

So Why Do We Exist?

You can probably now answer the question, “How is it that we find ourselves in so hospitable a universe?” It’s just one among a multitude of universes. In our universe, the constants of nature and the laws of physics are exactly what we need them to be so that we can exist.

We would only have come into being in a universe that could sustain human life.

It is just a matter of chance that the hidden dimensions were arranged in a way that caused the strings to create our particular universe, one among countless others. From a string theory viewpoint, it’s no more complicated than that.

Detecting other universes

Is it possible for us to detect other universes? Occasionally two universes could collide. Imagine two water balloons bumping into each other. That would cause ripples to form and spread throughout each balloon. Now imagine two universes colliding. The collision should cause similar ripples, only this time they are gravity waves. We are on the verge of being able to detect such waves with current instruments. Should we find a gravitational wave without any apparent source within our universe (a big “if”), we might be able to attribute that to a collision of universes.

Physicists have already detected gravitational waves caused by black holes spiraling into each other. These events caused small ripples in spacetime which were detected in 2015 at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington and Louisiana. So, the current technology should theoretically be able to detect the much larger ripples in space-time caused by the collision the video another universe with ours.

Might there be practical applications of string theory?

If string theory is correct, it points to a way to unify the four forces of nature: gravity, electromagnetism, the strong force and the weak force. All attempts to unify these forces have failed so far. But string theory gives scientists some hope that it can be done.

It’s hard to imagine a practical application of string theory to our daily lives. But the same was said about quantum theory in its infancy. And quantum theory lead to a host of devices that we use and depend on, such as the smart phone and the GPS. The entire computer industry is based on an understanding of the quantum properties of the element silicon. A unified field theory, the “Holy Grail” of physics, may ultimately open doors that we did not even know existed.

We are just beginning to understand such remarkable phenomena as quantum entanglement, where two particles put in close contact and then separated, can communicate with each other over immense distances faster than the speed of light could relay the information. And we are just beginning to develop practical quantum computers that solve problems in a few moments that now would take the rest of the time available in the universe to solve.

A theory of everything, powered by tiny vibrating strings, might advance our technological prowess even further, enabling us to survive the many challenges facing humanity in the future.