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Why are the laws of nature the way they are? And should they be like that? How do matter and energy, space and time interact to create the cosmos? The ultimate answer to such questions requires what scientists call a theory of everything. But how close are researchers to creating this theory? Let's see what science says. The goal of fundamental physics is quite grandiose. Ideally, we want to create a theory that answers all questions: from the nature of the smallest building blocks of the universe to its origin, evolution, and ultimate demise. We have a name for such a grand theory. We call it the Theory of Everything, or TOE for short. If a theory of everything were ever developed, I would be out of a job because there would be no
physical questions left to study. Actually, finding answers to deep questions in physics is what I do. So, how close are we to developing a theory of everything? So, do I need to update my resume yet? If you follow the press reports on scientific advances, it's easy to get the impression that a reliable theory of everything is just around the corner-whether it's superstring theory, Wolfram Model hypergraphs, twistor theory, or perhaps one of the dozens of, um, creative theories I get in the mail every day. The situation is often presented as if all that is needed to create a definitive theory is a flash of enlightenment from some supergenius, and the deed is done. It would be similar to how Einstein invented
the theory of relativity and turned classical physics upside down. Is such a huge step forward even realistic? Well, everyone has their own opinion on this-from overly optimistic to extremely pessimistic. Some people are fascinated by mathematics, while others have a more down- to-earth perspective on the subject. So let me share my take on this conversation. If you ask most of my colleagues if there is a theory of everything, they will say: probably. Me too. If you ask them what they know about it, they will say that the theory is applicable at energies much higher than those we can achieve with current technology. This is quite logical, since in the past, studies at increasingly higher energies led
to simpler and more universal theories. If you ask them to elaborate, they will say that the energy at which the theory of everything will work most naturally is the so-called Planck energy. Planck energy is just one of a number of ideas: Planck time, Planck length, Planck mass, and so on. During the COVID pandemic, I made a video about Planck quantities, a link to which is in the description. What is important to us is that the Planck energy is the level at which, according to theoretical physicists, the mathematics of the theory of everything most clearly applies, and it is approximately 10 to the 16th power of teraelectronvolts (TeV), where the electronvolt is the standard unit of
energy. This is a unit with 16 zeros. That's all you need to remember. So, 10 to the 16th power of TeV. It's pretty simple. We just need to generate that kind of energy, and-bam!-the theory of everything should be just around the corner . However, here is the harsh reality. The truth is that the Large Hadron Collider at CERN, which is the most powerful particle accelerator ever built, when operating at full power can produce, to round off, about 10 TeV. So let's stop and realize this. Regardless of the units of measurement, the highest energy we have data on is 10. However, the current theoretical belief is that the theory of everything will clearly apply on a scale of 10 to the 16th power. That's.well, let me do the math.
Multiply by five, divide by two, carry over the seven. A quadrillion times higher than what we can study now. A quadrillion is a large number. A theory of everything will require us to extend our knowledge to energies far greater than what we can currently study in order to achieve what we seek. This may take some time to realize. So let me offer an analogy to give you a sense of the scale of what we're trying to do. Imagine that it was 2 million years ago and you were a member of the genus Homo that existed at that time, say, Homo habilis.
You live in East Africa in an arid savannah. This is an ecosystem that you are familiar with. Your height is about a meter, if we take very approximate figures. You know what the world looks like within a meter around you. What can you know about the world at an increasing distance from you? At a distance of 10 meters, or 10 to the first power, you have every reason to expect that what you see around you and what is 10 meters away will be almost the same. Your interest in this is probably quite high. What about 100 meters, or 10 to the second power? Well, it's not that far off. The world there is probably quite similar, although maybe there is an elephant or something like that standing there. There are no elephants where you are, so it's a surprise,
but not too big. And what about 10 to the cube of meters, or about half a mile? Well, half a mile away, the terrain is probably pretty much the same as Dusty and hot African veld. At a distance of 10 to the 4th power of meters, or 6 miles, the picture is likely to repeat itself, the same thing again. African veld. So perhaps extrapolating from the known to the unknown isn't so absurd after all. What about 10 to the 5th power of meters, or 60 miles? Everything still looks similar, looks good. 60 miles is probably a walking distance for an ancient human, which means you are familiar with your environment over shorter distances.
What about 10 to the 6th power of meters, or 600 miles? Well, here's where the fun begins. To the east at this distance you will encounter the Indian Ocean. And to the west are the tropical forests of Congo. So, this is where the surprises begin. At a scale 10 to the 6th times larger than you, you'll encounter giant squids and enormous sharks- things that were simply unimaginable to ancient people. And rainforests bring with them an incredible amount of precipitation. Not at all what you see in the veld. I mean, it rains in East Africa too, but there are also long droughts there. This shows us that at a factor of 10 to the 6th power, which is a million, you start to encounter the unexpected. But we're aiming for a quadrillion.
Let's continue. At a distance of 10 to the 7th power of meters, we encountered truly unexpected things. The icy wastes of Antarctica, the dry Sahara and the majestic Alps in southern Europe. Let's jump to 10 to the 12th power. This is a distance roughly equal to the size of Jupiter's orbit. So there are some real surprises here. The vacuum of space, other planets, Jupiter-everything is different. 10 to the 12th power is a trillion. Let's move on to 10 to the 15th power, a full quadrillion. This distance is about a tenth of a light year, or about 100 times the orbit of Pluto.
Pluto may no longer be considered a planet, but it's a good reference point for the far reaches of the solar system. First, the point is that a quadrillion is a huge number. Second, I hope that your intuition about what the world is like at the scale of a meter does not prepare you for what you will encounter at a distance of a quadrillion meters. You will meet penguins in the Grand Canyon. But you will come across Saturn. You couldn't have predicted this. I mean, you'd have a hard time even imagining that those moving specks in the sky are completely different planets, or even the concept of a
planet. So, this is kind of a challenge that we have set for ourselves. Data from the most powerful particle accelerator on the planet certainly teaches us a lot, but we are still a long way from achieving our goal. And this brings us to a very important question. If the chances of someone coming up with a theory of everything based on what we know now are, well, unlikely, then how do we move forward? I think the answer is simple. We recognize that a final theory is beyond our reach at this time, but we can solve known problems one by one and use this approach to take a step forward in our quest for knowledge. For example, we know that galaxies rotate faster than the known laws of physics can explain.
Either there is more matter than we can see, or we don't know the true laws of physics. This is a problem often called dark matter. Then there's a really interesting problem: our best-studied laws of nature state that the amount of antimatter in the universe must exactly equal the amount of matter. However, our observations show only matter and no antimatter. What's wrong with this? Figuring this out will clearly point us in the direction of better developing that elusive theory of everything. A third example can be found in understanding the laws that make the quantum world seem so strange. Is the universe inherently probabilistic, or is there a deeper theory that explains these probabilities? Such unanswered questions are exactly what large national
laboratories like Fermilab were created for. Well, that, and also developing commercially viable technologies, of course, but as a particle enthusiast, it's this search for fundamental theory that drives me. I figure if we learn something about the laws of nature, one of my more practical colleagues down the hall will figure out how to turn it into a useful device. And there are many historical examples of this: electricity, the transistor, superconductivity, quantum mechanics. These were all breakthroughs in fundamental physics that led to technologies that transformed our society. A win-win for everyone. But we need to be patient. The path from where we are now to where we need to be will not be quick. It's even foolish to
think that this will happen soon. We are still very far away. But we are making progress, and the only way to achieve more is to keep working. I like to compare the search for a theory of everything to a journey whose goal is to conquer the highest peak. Our scientific achievements to date-the theory of relativity, quantum mechanics, the Standard Model, etc.-are just the beginning of a much longer journey. Somewhere in the distance is our goal, which we have not yet reached. There are smaller peaks in between that we need to explore along the way. The paths connecting the peaks are hidden from us, shrouded in mystery, with deceptive turns and precipices we have not yet encountered. It's a great metaphor, and it's going to be an exciting
journey. Let's begin. Okay, finding a theory of everything seems like a pretty noble goal to me, although it's a little sad to realize that I won't live to see the final result. It's nothing. This happens with many things. The main thing is to keep the movement going so that future scientists can take over the baton and take their own steps on this ancient path to knowledge. It may be obvious, but this multigenerational journey is always on my mind when I say, as I often do, that physics is everything.
