Braneworlds

This article was originally written and published on January 12th 2008.
Translated to English on September 6th 2016 with no revision of its content.

Prologue

I have just read a book entitled “The Fabric of the Cosmos.” One of the comments for the author says “Another Hawking, only better.” The author is Brian Greene from Columbia University, who also wrote “The Elegant Universe” that became a best seller. Aside from books, a three-episode series titled “The Elegant Universe” was produced by NOVA and PBS and is available online. It is highly recommended, especially for those who prefer films rather than books, and is easier to understand. My astonishment towards the universe thickens and it makes me think even deeper.

I posted part of my article in a mailing list on the internet, and received many responses. It was a very serious topic and inspired many to participate in a long discussion that extended to religion.

This article is a summary of several books on physics that I have read, however, I try my best to use simple words so it will be easily understood and I hope it could be a simple reference for everyone.


Classical Physics

Our journey starts from an accident in the past involving the head of a well-known intellectual. An apple that fell off from the tree brought an inspiration to Isaac Newton. The idea of an apple falling from its branch was the beginning of the popularity of force introduced by Newton. The force of gravity caused the apple to fall off. This force also keeps the planets to stay in their orbits around the Sun. Isaac Newton’s book “Principia of Mathematica” is still used today to launch rockets around the moon and to send rover to Mars.

Newton successfully changed people’s point of view. The invisible force of gravity can be measured and becomes real in its application. The gravity is a fundamental force in the universe. However, Newton could not provide answer to the question of what gravity is.

General Relativity

Dr. Albert Einstein
In a patent office in Switzerland, a young scientist named Albert Einstein was studying light. He discovered that light traveled in a high speed and not one object on Earth could travel faster than light. The speed of light was constant and was the same wherever it was in the universe. Einstein introduced to the world, a new concept and a new way of thinking in regards to space-time.

In studying this, Einstein realized that a massive object in the universe such as a star or our sun could bend the space. Imagine a bowling ball on top of a trampoline. The trampoline surface flexes downward due to the mass of the ball. If you roll a smaller and lighter ball, such as tennis ball, across the trampoline surface, it will turn towards the curved trampoline surface. This is the force of gravity that Einstein had discovered.

The planet orbit around the Sun is in fact an orbit that moves in a straight line, however, it is deflected by the curved space caused by the mass of the Sun in the nearby area.

What would happen if the Sun disappeared? According to Newton, the planets would lose the gravity force from the Sun and at the same time would continue to move away. It is not a wrong illustration, however not entirely correct. Einstein added that light needed 8 minutes to travel from the Sun to Earth. If the Sun suddenly disappeared, then the curved space that had been caused by the mass of the Sun would suddenly became flat. Imagine the trampoline surface becomes flat when you take away the bowling ball, or a rippling water surface becomes calm. The gravity force rippled away from the center of the Sun at the same speed as light. Therefore, according to Einstein, Earth would not leave its orbit around the Sun before 8 minutes - the time needed for the gravity force from the Sun to travel to Earth.

Einstein released the General Relativity theory. The gravity force had been successfully explained. Up until today, the General Relativity theory may explain the movement of massive objects in the universe, i.e. planet, sun, and galaxy. The Relativity Theory explains the universe in a macro scale. Einstein believed that the universe worked in an orderly manner because it followed the laws of physics. “God doesn’t play dice”, he said.

Einstein gave a new insight on how we see space and time. They were like a spread fabric. Space-time could be shrunk, stretched, spiraled or distorted by the gravity field of massive objects. 


Quantum Mechanics

From this point on, my writing will be more complicated to follow as I found difficulties in explaining it. The bright ideas and theories that Einstein brought had generated inspiration towards theoretical physicists all over the world. New ideas had been proposed almost simultaneously. In this matter, I will only mention the most important discoveries.

James Clerk Maxwell
Electricity is a force. Magnet is a force. People discovered that electricity and magnet were relevant and mutually influenced. James Clerk Maxwell managed to unite both forces into another natural fundamental force after gravity, which is called Electromagnetic (EM) force. EM force is produced in nature at any moment and each particle carries electricity that significantly affects particle interaction.

Maxwell sent a paper to Einstein to be published. He believed that aside from gravity that bended and rippled through space, the EM force did the same and needed space to travel. WHERE? In order to answer that question, Maxwell proposed an additional space dimension where EM force could travel. Einstein accepted his proposal. It was a momentum for us to correct how we see nature. However, where is this additional dimension? Why can’t we see it?

Other scientists, Kaluza and Klein, proposed that this extra dimension was very small. Imagine an electricity cable from afar. You could only see it as a string that stretched out without having dimension other than length. However, if we looked closer, as in the view of an ant, we could see the ant moved forward, backward, turned to the left and right side around the cable. This is the invisible extra dimension. Kaluza-Klein proposed that the extra dimension existed in each points in space; invisible because it was so small.

Einstein was inspired by EM force and believed that to essentially understand this universe, the force of gravity should be united with EM force. Unification. As of that moment, he spent his life to search for one formula that could explain both gravity and EM forces.

Meanwhile, Neils Bohr introduced his atom model and was widely accepted that an atom consisted of a nucleus that was formed by proton (positively charged) and neutron (neutrally charged), while electron (negatively charged) orbited around the nucleus. 

At this moment, people started thinking about microcosmic universe. To completely understand the universe, one should understand particle interaction. This research brought us to the sub-atomic world, and here is where quantum physics was born. Relativity Theory explains the macro cosmos, while Quantum Physics explains the micro cosmos.

However, there was a contradiction. In the micro universe, gravity was like a drop in a bucket. In other words, gravity force didn’t have any role in particle interaction. Instead, physicists discovered other fundamental forces: Strong Nuclear Force that affixed atom’s nucleus in its place, and Weak Nuclear Force that caused atom disintegration or radiation.

So far, all the fundamental forces of nature had been discovered. They are: Gravity, Electromagnet, Strong Nuclear and Weak Nuclear. From the energy perspective, the Strong Nuclear Force was the strongest. It was proven by the invention of atomic bomb. The detonation of atomic bomb was the release of strong nuclear force caused by particle separation in the atomic nucleus. This separation caused atomic disintegration (radiation), which energy (Weak Nuclear Force) can be detected up until today.

Gravity was the weakest of all three. In comparison with Gravity, the EM force was billions time stronger. The force of gravity could only be seen in objects of huge mass such as planets and stars. In the quantum universe, gravity didn’t count because it was too small to be considered.

Thus, it was a dilemma for physicists. The unification encountered problems.

On other occasion, Roger Penrose and Stephen Hawking were studying a natural phenomenon, which was the collapse of a star. A star could collapse if each and every particle it was built from had lost energy. An out-of-energy Electron would fall into the atomic nucleus. The size of the atom would shrink significantly, thus the size of the star would also shrink drastically. However, the gravity force remained unchanged. In other words, the gravity force was so strong within such small sized object, causing the space to bend indefinitely.

So strong this gravity force was, that the light could not even penetrate it. If the light could not travel there, we would not be able to see the collapsing star. The existence of a collapse star could only be seen from observing massive gravity force in the blackness of space. That was how a collapse star got the name Black Hole. 

Light, or light particle called Photon, which fell inside the black hole, could not escape. However within a certain distance from the core of the black hole where gravity was not as strong, light could manage to stay afloat although still too weak to escape from it. Such distance is called The Event Horizon. It is named Event Horizon because it is believed that when the light stopped, time in the nearby area also stopped.


Singularity and the Creation of the Universe

I feel the need to discuss this topic. The final goal of physics is to understand how nature works, how it is created and what for. The last question sounds like human’s wishes to understand God. However, if God truly created this universe with specific reason, to know it we should first answer the question of how this universe was created.

Penrose gave an idea to Hawking about the origin of the universe. Added by an observation about an evolving universe, it was concluded that this universe in the past was so small in size. Hawking confirmed that this universe started as a single small point. A singularity. 

Singularity comes from the word Singular or “single” by condition. At the starting point of the creation of space-time, all the fundamental forces might have been existed as a single force. Then, just like in a nuclear bomb, the separation of the single force into four forces resulted in a large explosion called “The Big Bang”.

Big Bang is the event of the Creation of the Universe. An event where a single force separated into four fundamental forces.

The universe keeps growing until now, forming stars and planets.

The discovery of Black Hole was like watching the Big Bang from the reverse end. Black Hole is a singularity. Therefore, to understand how this universe was created, is to unite all the existing forces. Up to this phase, human had successfully united EM with Weak Nuclear forces resulted in Electroweak Force. Also Electroweak united with Strong Nuclear resulted in a framework that is believed to be the Standard Model of a final theory that will be able to explain the origin of the universe in one single theory: “The Theory of Everything” (TOE).


Relativity VS Quantum

The Black Hole was like the devil in physics at that time. On one hand they could forget about gravity because it was considered too weak, on the other hand the unification of all the forces resulted in one singularity. How could one object of indefinite small size produce such force of gravity? How to explain the physics of a Black Hole?

The Relativity Theory did not apply in quantum universe because the force of gravity only applied to massive objects. Quantum physics successfully explained the micro universe, but did not include gravity.

Conclusion: Physics disintegrated inside the Black Hole. Black Hole was truly an abyss that science could not reach.    


The String Theory

We go further back into the past where most physicists rushed to study quantum physics and only a handful of physicists in the world stayed behind and did not follow the steps of their peers.

When most people accepted that atom and its particles were in the shape of point or ball, these handful of scientists discovered another possibility in the mathematical equation that brought them to the wild idea that all this time the mistake in physics lied in the ‘shape’ of particle. We had been wrong to believe that particle was in the shape a ball. They discovered that particle was in fact in the shape of a string.

So, what was the implication if the fundamental particle was in the shape of a string?

The string shape was very small. Millions time smaller than quark. To imagine the size of a string, try to picture an atom in the size of our solar system, while the string is the size of a tree on Earth. Because it was very small, it was assumed that it only had length (one dimensional), it was vibrating and that vibration resulted in what we observed as particles. The string theorists believed that String was the only material to form space and time. What we observed as various particles was in fact the variations of vibration of the same string.

Therefore, the calculation and mathematical equation changed drastically. Quantum physics that once ignored the force of gravity, now accepted that gravity was a part of its mathematical equation. To put it briefly, gravity force was found in quantum universe. The Relativity theory and Quantum physics were now unified. The string theory was believed to be the final theory that had been searched all this time; a single theory able to explain how the universe worked; the theory of everything.

How could this happen? How did they find the force of gravity in the mathematical equation of quantum physics? To discuss this matter, we should go back a little bit to learn the long history of string theory development.

The String Theory did not just happen in one night. In 1968, a young Italian physicist named Gabriele Veneziano, now works for CERN, studied mathematical equation on Strong Nuclear force. The discovery of this equation made way to researches on hidden force inside atomic nucleus. This research inspired another scientist named Leonard Suskind from Stanford University, who realized that such equation indicated one hidden thing; a particle that had internal structure capable of flexing and stretching. This particle was not in the shape of a point or a ball, however it was string-shaped and naturally flexible. At first, his discovery did not get any responses from other physicists. 


John H. Schwarz dan Michael B. Green (Pictures from NOVA)

It was another physicist who continued the research on string. In the year 1973, John H. Schwarz from California Institute of Technology, suggested that if the string theory was right, then it could explain many mysteries in the universe. Schwarz managed to draw attention and scientists from all over the world joined to study this radical theory.

However, the Strings Theory faced major problems, where there were several anomalies in the mathematical calculation or equation. Firstly, the strings theory involved a particle with zero mass and tachyon particle, a particle that moved faster than light. I have mentioned above that Relativity Theory did not justify other object in the universe traveling faster than light. Once again the string theory almost lost its prestige.

Michael B. Green from Cambridge University joined Schwarz to study and dissect the string theory mathematical equation. They found out that the strange particle that caused anomalies was in fact ‘graviton’, a particle in gravity force. This monumental moment shook the world. Schwarz and Green discovered the force of gravity in their equation. They had successfully eliminated the anomaly.

More scientists joined to continue the works of Schwarz and Green until they encountered other problems:

1. The String Theory involved extra dimensions. As we know now, we lived in a universe that consisted of 3 space dimensions (length, width, height) and 1 time dimension, thus totaling to 4 dimensions. However, the string theory needed to move in 9 space dimensions, therefore the universe in which we live in, supposedly has 10 space-time dimensions. Where are the other 6 dimensions? Why can’t we see them? Once again Kaluza and Klein proposed that the 6 dimensions were very small in size that we couldn’t observe them. However, people started to accept these extra dimensions because there MUST be extra dimensions for the String Theory to work. The discovery of extra dimensions was phenomenal. 
2. There were 5 Strings Theories. This was a big problem. How could the theory of everything exist in 5 variations? Each theory was equally correct, however with crucial differences in the mathematical equation.

String / M-Theory

Edward Witten (Picture from NOVA)
Only in 1995, in a World Physics Convention, a physicist from Institute for Advance Study who published his paper, Edward Witten, became popular. Edward Witten was named “The true successor of Einstein”; successfully unite the five-string theory into one single theory, which was the M-Theory.

Witten presented that the five-string theory was in fact a way of looking at one thing in different perspectives. It was like five people being in a dark room and each one touch a different part of the same elephant. One got its head; the others got its leg, trunk or body. Only after Edward Witten’s explanation that people realized that they all have touched the same elephant in the room.

The light that was brought in by Witten with his M-Theory was in the form of an additional dimension in the mathematical calculation of the string theory. All the equation worked together and made sense. Now our universe that was believed to have 10 dimensions in string/M-theory changed into 11-dimensional universe.

Edward Witten never mentioned what ‘M’ stood for. 


Braneworlds

M-theory stated that:

1. String was a tremendously small line that only had length (one dimensional), which ends were open loops.
2. Some strings were stretched, causing them to have length and width (two dimensional), forming a membrane (or “Brane” for short) or an extremely thin sheet. We call this 2-brane, while the aforementioned one-dimensional string we call 1-brane.
3. Both ends of a 1-brane string should attach to/stand on a 2-brane string.

After the birth of M-theory, there was a significant difference. People no longer perceived the extra dimension as a strained extremely small dimension. M-theory brought us a perspective of a huge extra dimension. We might be living in 3-dimensional universe or 3-braneworld, and our 3-braneworld was inside a higher dimension – a universe with 4 dimensions or 4-braneworld.

To understand the membrane concept, imagine your TV screen as a 2-dimensional universe. The actors were living inside the TV in a 2-braneworld (having only width and length) and this world did not have a third dimension. They did not know or understand that the distance from your eyes to the TV was the third dimension that did not exist inside the TV. To put it briefly, to understand the extra dimension, the actors who lived inside should come out of the TV.

Can you understand up to this part? Now imagine that our universe was the aforementioned TV with 3 dimensions. Therefore, the distance of the audience outside the TV to the TV set was the fourth dimension that did not exist in our universe. The universe outside ours was a 4-dimensional world.

Then imagine that the aforementioned 4-dimensional world was a television. The distance between the audiences to the TV set was the fifth dimension, and so on.

Let us continue to imagine our universe in the same manner.

Our 3-braneworld existed inside a higher membrane, which was a 4-braneworld. In other words, our 3-braneworld was wrapped inside a 4-braneworld. M-theory stated that our 3-braneworld might co-exist with other 3-braneworld (parallel universe). How many parallel universes are they? Nobody knows.

Where are the 5^th, 6^th, 7^th, 8^th, 9^th, and 10^th dimensions?

Imagine if a 3-braneworld was wrapped in a 4-braneworld, therefore:

3-braneworld wrapped in 4-braneworld (layer 1)

4-braneworld wrapped in 5-braneworld (layer 2)
5-braneworld wrapped in 6-braneworld (layer 3)
6-braneworld wrapped in 7-braneworld (layer 4)
7-braneworld wrapped in 8-braneworld (layer 5)
8-braneworld wrapped in 9-braneworld (layer 6)
9-braneworld wrapped in 10-braneworld (layer 7)

Our universe was wrapped in another universe of higher dimension, and inside each membrane there were parallel universes. 

Opened-loop string, which ends are attached to a membrane (Picture from NOVA)


Graviton

M-Theory was accepted as an elegant theory with high level of mathematical beauty. It is an achievement in human’s modern civilization.

To complete my description, I would like to discuss a little more about the development of this theory.

Closed-loop string (Picture from NOVA)
String is believed to have opened-loop ends, which ends are opened and attached to other membrane. However, it is also believed that there are other strings which ends were connected (plugged in) to form closed loops. With such shape, these closed strings are not attached to any membrane and would be free to float and cross other membranes. This closed-loop string is called Graviton.

Remember the aforementioned gravity force that was believed to be the weakest among other forces? With graviton free nature, the gravity force would be very strong, might even be stronger than Electromagnetic force. It only looked weak because a part of gravity force was able to move to other membranes freely.

Graviton is the only particle today that is believed to be able to move freely to other membranes. Other forces could not. Therefore, we cannot other branes or parallel universes because light cannot travel out of the membrane. Strong Nuclear and Weak Nuclear, Electromagnetic and Light forces are trapped inside one membrane.

One thing that captured the world’s attention is how to prove the existence of string through laboratory experiment. String is an elegant theory that has not been proven trough experiment. However, with conditions set within the theory itself, there are opportunities to prove it and it has become a priority objective. Among others, are the ongoing cooperation between the Massachusetts Institute of Technology (MIT) and California Institute of Technology (CIT) and funded by the National Science Foundation to build a giant observatory that is not based on light or radio, but based on the force of gravity. The goal is to detect graviton that would appear carrying signatures of a universe of another membrane. This facility is called Laser Interferometer Gravitational Wave Observatory (LIGO). It is also planned to build an outer-space version of LIGO named Laser Interferometer Space Antenna (LISA).

Illustration of a Graviton leaving a membrane (picture source: NOVA)

Another research is carried out by Fermilab, a laboratory in Illinois that owns an atom smasher, which is a Particle Accelerator that is used to accelerate Hydrogen’s atomic nucleus inside a 4-mile track to be collided with another Hydrogen’s atomic nucleus on the other end. The collision of the atomic nucleus would result in the disintegration into smaller particles. Before the M-theory, scientists only tried to identify the smaller particles, but now they also try to detect graviton that would appear after the collision. However, graviton would only appear shortly because a single graviton would tend to cross to another membrane. Graviton that appears and disappears in less than a blink of an eye would hardly give the observers enough time to detect it. Therefore, graviton detection is marked by the absent of such particle after the collision.

Fermilab (Picture source: NOVA)

A similar facility is in a development stage, with power 7 times stronger than that of Fermilab. These new atom smasher and giant particle accelerator are owned by CERN, Switzerland.

Large Hadron Collider (LHC) that belongs to CERN, the biggest particle accelerator in the world.

Millions of dollars have been spent to build these giants facilities and they are currently in a race to be the first Graviton finder. If graviton were found, it would confirm the string theory and all its implications; the braneworlds that described our universe as layers with 11 space-time dimensions would be the truth. And the whole universe could be explained in one single theory, “The Theory of Everything.” 


Membranes (Picture from NOVA)


Zero-Brane

Other development of String/M-Theory is the emergence of a group of scientists who discovered irregularity on the statement that string was the only basic ingredient to form space and time. Their question was; if string needed space and time to vibrate and move around, how could they be the fundamental material that formed space-time?

Should there be a fundamental material that formed space-time, this entity should not have been bound by space and time. In other words, it would be space-less and time-less entity. This type of entity could never have been in the form of a string, but a point without dimension or with zero dimension; a Zero-Brane Entity. This proposal should be given serious attention, because it stated that string was not the fundamental material that shaped space-time.

Zero-Brane in the shape of a point without dimension should have marked each point in space, but not bound by it. The points were in order like a grid. This theory became known as the Matrix Theory. “M” as “Matrix” in M-theory. 


Conclusion

We finally arrive in this chapter, in which I have prepared a conclusion, opinions and suggestions for the reader as a food for thoughts and discussions.

Once Stephen Hawking had asked, if space and time were destroyed in one Big Crunch, then where is the place for God? Hawking has been called an Atheist (people who doesn’t believe in God). However, I once had asked the same question. A friend reminded me to tread carefully and avoid the state of becoming an unbeliever. However, I still believe that we all are God’s creation, and we are given brains with ability to ask such question. Therefore, how could we become an unbeliever?

I channel my faith and curiosity through studying spiritual believes, physics and doing interviews to several religious leaders. The conclusion that I made is written as the followings.

People say that God is bigger than the universe. He cannot be destroyed by His creation. It’s true and I believe it! Then, there should be a logical explanation that places God in his Almighty position.

In the universe we are living in, we stay in a planet called Earth. Earth and other planets orbit around the sun in a star system. Our star system is one among millions others in one Galaxy called the Milky Way. Milky Way is one of millions other galaxies in one Galaxy Cluster. And this galaxy cluster is a part of other galaxy clusters. This is how big the universe is. Earth is like a speck of dust. The journey of human’s science has crossed the border of our universe and is now trying to cross to another universe within a higher dimension.

Can human travel to 10-braneworld (the highest universe)? Will we find God there?

There is a term that I mentioned above: God is not bound by His own creation. God could not be in any of the braneworlds. God is not bound by ‘time’ that He created. God is an entity, free of space and time. God must be in charge of a realm where space and time are not relevant: The Zero-Brane Entity.

Others

The ideas for other studies are filling my head, such as: How human would cross to other brane where even light could not? How do Angels go back and forth easily from one braneworld to the others? How powerful human being is to be able to master all that?

Below are the discussion results among my friends:

There is no other particle able to travel to other braneworld except for graviton. Whether there was other particle having a closed-loop, we haven’t found it at this moment. However, if there was one, to be able to travel to other braneworld we should wrap ourselves in graviton. A friend had an idea that human should transform into a closed-loop entity to travel to other braneworld. Or could this entity be that we now call spirit? Could it be that spirit is a closed-loop entity? Does that mean that we should die first to be able to travel to other braneworld?

I imagine about an entity of less dimensional world (i.e.: our 3-dimensional world); if we traveled to another universe of higher dimension (such as a 4-dimensional universe), we should have had insufficient substance to exist there and might even be intangible. Like if you imagine the people inside our 2-dimensional television existed in our 3-dimensional world, they might have been in the shape of very thin sheets and would not survive in our world.

It is the same in the case of us going to a higher braneworld, we might not be able to travel in our current state. The idea that sounds the most logical is if we transform ourselves into an entity that could survive in any braneworld.

And if we managed to transform ourselves into such neutral entity, could we go to Zero-Brane? I don’t think so. Why? Because as a neutral entity, we would still need space and time to exist.

I believe that if human mastered the braneworlds, then human became one with nature. At this level, presumably human had matured to almost perfection to become one with nature in all braneworlds. No walls between physics and metaphysics. Human would be able to hear animal’s laughter, cry of a plant, ants’ conversation and rocks’ complaints. Human would absolutely lead this world.

I close this article at this point. I hope it may arise your curiosity and you would join us in finding explanations and truths in your own way.


Sources:

• Book: "The Fabric of the Cosmos" by Brian Greene
• Book: "The Elegant Universe" by Brian Greene
• Movie: "The Elegant Universe" by NOVA
• Other sources from religious books
• Interviews
• Personal/self Deduction