According to the science channel “we live in a world with three spatial dimensions (length, width and depth) and one dimension of time. This means that it only takes three numbers to determine our physical location, which on Earth breaks down to longitude, latitude and altitude/depth. Time naturally comes into play by identifying when we’re at that particular point in space. Some physicists, such as string theorists, believe that additional dimensions also exist but are folded away in each point of space and are invisible to the human eye.”

On Earth, these coordinates break down to longitude, latitude and altitude representing the dimensions of length, width and height (or depth). Slap a time stamp on those coordinates, and you’re pinpointed in time as well.

In string theory(/theories) the additional dimensions are “wrapped” on very small length scales, so small that our senses cannot experience them. I do not share the enthusiasm about these theories, because apparently they cannot be proved nor disproved: in this case they remain a mere mathematical exercise.
But the general idea of additional dimensions is not, in my opinion, to be rejected. Just like our senses cannot register great part of the electromagnetic radiation spectrum, maybe they are not able to “see” many other things (without entering in the realm of spirituality).

The understanding of the ancient Greeks regarding a multi-dimensional universe is quite different from the modern concept of higher dimensions in physics. The ancient Greeks did not possess a comprehensive scientific framework or mathematical language to describe multi-dimensional spaces as understood in contemporary physics. However, they did engage in philosophical and speculative discussions on the nature of reality and the possibility of alternative realms.

In ancient Greek philosophy, there were various theories and concepts that hinted at the existence of multiple dimensions or alternative realities:

• Plato proposed that the physical world is a mere reflection or imperfect copy of a higher realm of perfect and eternal Forms. These Forms were considered to exist in a separate, transcendent realm beyond the physical world, suggesting the existence of a multi-dimensional reality.
• The Pythagoreans, including Pythagoras himself, believed in the existence of a hidden or unseen world underlying the observable reality. They speculated that this unseen world was composed of mathematical entities and principles, suggesting a potential multi-dimensional nature to reality.
• Neoplatonic philosophers, such as Plotinus, developed the ideas of Plato and incorporated mystical and metaphysical concepts. They proposed the existence of multiple levels of reality, ranging from the physical realm to higher realms of spiritual and divine beings.

In addition to the ancient Greeks, other ancient civilizations also had their own beliefs and understandings regarding the nature of the universe, which may have included ideas about multi-dimensional reality:

• Hinduism: In Hindu philosophy, particularly in texts like the Upanishads and Vedas, there are references to higher realms and dimensions of existence. These realms, known as “lokas,” are considered to be inhabited by different deities, celestial beings, and enlightened souls.
• Buddhism: Buddhist cosmology describes a multi-dimensional universe consisting of various realms or planes of existence. These realms include the human realm, animal realm, heavenly realms, hell realms, and realms inhabited by various gods and other beings.
• Mayan Civilization: The ancient Maya had a complex cosmology that included multiple layers of existence. They believed in various celestial realms inhabited by gods and spirits, as well as an underworld realm known as Xibalba. The Maya also developed an intricate calendar system that reflected their understanding of time and cosmic cycles.
• Norse Mythology: Norse mythology, as depicted in texts such as the Prose Edda and Poetic Edda, describes a cosmology with multiple interconnected realms. These realms include Asgard (home of the gods), Midgard (the human world), and other realms inhabited by giants, elves, dwarves, and other mythological beings.

It is important to note that the understanding of multi-dimensional reality in ancient civilizations was often intertwined with their religious and mythological beliefs. These understandings were primarily expressed through religious texts, mythologies, and cultural traditions, rather than through scientific or mathematical frameworks.

The concept of higher dimensions as understood in modern physics is a product of the scientific advancements and mathematical formulations developed in recent centuries. It is within these frameworks that the idea of dimensions beyond the three spatial dimensions we commonly experience has been explored and investigated.

While these ancient philosophical ideas may suggest a notion of multi-dimensional reality, it is essential to note that their understanding was more metaphysical and conceptual rather than scientific or mathematically rigorous. The ancient Greeks lacked the mathematical and scientific tools necessary to explore and describe dimensions beyond the three spatial dimensions we commonly perceive.

The modern concept of higher dimensions emerged with the development of mathematical frameworks like geometry, algebra, and later, the theory of relativity and quantum mechanics. These mathematical models and physical theories allow for the exploration of dimensions beyond the three spatial dimensions, such as time as the fourth dimension or additional dimensions in string theory and other branches of modern physics.

In summary, while the ancient Greeks contemplated the existence of alternative realms or dimensions in a philosophical and speculative sense, their understanding differed significantly from the mathematical and scientific frameworks employed in contemporary discussions of higher dimensions in physics.

By the late 1980s and very early ’90s, string theory was definitely the theory that everyone felt would eventually lead to the TOE. There were just two basic problems with it.

Modern-day string theory is a theoretical framework in physics that aims to provide a unified description of the fundamental particles and forces of nature. It suggests that the fundamental building blocks of the universe are not point-like particles but tiny, vibrating strings. These strings exist in a space-time with more than the three spatial dimensions we perceive in everyday life.

Here are some key points about modern string theory:

1. Higher Dimensions: String theory proposes that space-time consists of more than the three dimensions of space (length, width, and height) and one dimension of time (which gives us the familiar four-dimensional space-time of Einstein’s theory of relativity). String theory suggests the existence of additional spatial dimensions, typically six or seven in total, curled up or compactified to a size too small to be detected directly.
2. Vibrating Strings: According to string theory, particles that we observe in nature, such as electrons, quarks, and photons, are not fundamental but rather different modes of vibration of the underlying strings. The specific vibration patterns determine the properties and behavior of the particles, including their mass, charge, and interactions.
3. Quantum Gravity: String theory is often regarded as a candidate for a theory of quantum gravity. It attempts to reconcile the principles of quantum mechanics, which govern the behavior of particles at the microscopic level, with general relativity, which describes gravity on a macroscopic scale. By incorporating gravity into the framework of quantum mechanics, string theory seeks to provide a consistent description of the universe at both small and large scales.
4. Mathematical Framework: String theory relies heavily on advanced mathematical concepts, such as differential geometry, topology, and algebraic structures. The mathematics involved in string theory is highly complex and sophisticated, making it a challenging field of study.
5. Multiverse and String Landscape: String theory has led to the proposal of the “multiverse” and the “string landscape.” According to this idea, there may be numerous possible configurations or solutions of the fundamental equations of string theory, each corresponding to a different universe with its own set of physical laws and constants. This concept has implications for the anthropic principle and the idea that our universe’s specific properties are the result of a selection process.

It is important to note that string theory is still a highly active area of research, and many aspects of the theory are still being explored and refined. As of now, experimental evidence supporting string theory is limited, and it remains a subject of intense debate and investigation within the physics community.

• Physicists had developed five different versions of string theory. Without spending the next five chapters telling you all about them, I’ll just give you their names. We have Type I, Type II, Type IIB, Heterotic O, and Heterotic E. They are all fundamentally the same, but the way that they incorporate supersymmetry and explain the vibrational patterns vary from theory to theory.
• These five versions each ended up having many possible solutions to the equations that defined them. There were different possible ways to curl up the extra dimensions with each solution corresponding to a universe with different properties. What lies at the heart of this problem is that the equations in string theory are so complicated that no one knows their exact form.