By Rosalyn Brady
October 28, 2022
UPDATED 12:00 PM EST
[Photo Credit: “Drawing of a tesseract from ‘Theosophy and the Fourth Dimension’  by Alexander Horne’”, The Worlds of David Darling]
Humans, as three-dimensional beings, can only view the universe in the first three dimensions: length, width, and depth. However, we have been conceptualizing a fourth dimension since as far back as the fourteenth century, and today, there are numerous theories regarding the existence of the fourth dimension and of dimensions beyond it.
Perhaps the best known of these theories is Albert Einstein’s General Theory of Relativity, which suggests that time is a physical, dynamic concept transcending clocks and temporal units, which general relativity suggests are socially constructed in order to measure time intervals between events so that our brains may record them more easily. General relativity also suggests that time and space are one and the same, fused together to form spacetime - said to be the very fabric of the universe. Spacetime is said to be able to curve. fold, and twist, rather than being absolute, and while we as three-dimensional beings could never perceive spacetime, we can feel its effects - one of which is gravity.
According to general relativity, spacetime can bend around objects with mass in the same way that a trampoline bends when people jump on it. Gravity is said to be caused by this bending - stars and planets bend spacetime the same way people do when they jump on trampolines, and in the same way a ball would roll down the curved part of the trampoline and rest at your feet, we stick to the surface of the Earth at the bottom of its curve, and the earth falls into orbit around the Sun slightly farther from the bottom of the Sun’s own curve. General relativity states that everything is in free-fall around gravitational warps which stop the free-fall - including galaxies, which are in free-fall around supermassive black holes, which will bend spacetime to a single point - a singularity.
However, this theory also has its critics. It is said that general relativity is incompatible with quantum theory, which seeks to explain the behaviour of subatomic particles. For example, particles such as photons and electrons have wavelike properties allowing them to occupy space in two places at once by splitting apart the way waves do, and for these split electrons to briefly pass through each other in a phenomenon known as ‘superposition’. However, this idea simply cannot coincide with that of general relativity - if spacetime is warped by matter, and some matter (i.e. particles) can be in two places at once, we cannot tell where the gravitational field will be as it cannot be in two places at once. Additionally, other forces of nature governing particles such as electromagnetism - particles’ magnetic forces - or strong nuclear forces - forces which hold particles together in atomic nuclei - merge together at high enough energy levels, while gravity does not merge.
Despite this, there are theories in place designed to bridge both of these - such as string theory, which suggests that all particles are made of infinitesimally small strings, which vibrate and writhe in different ways that we interpret as our universal building blocks, such as quarks, photons, electrons, and gravity, or quantum loop gravity, which suggests that spacetime - that is, gravity - is made up of minuscule fundamental particles similar to photons and electrons.
Perhaps general relativity is wrong altogether, and the fourth dimension is simply another dimension perpendicular to our three. A common depiction of this is the tesseract, which can be perceived as a cube with each of its two-dimensional faces replaced by cubes and can be unfolded into eight cubic cells that come together to form the tesseract. It often appears as a ‘cube within a cube’. Another example of this is the pentachoron, a pyramid with its five faces replaced by pyramids that appears as a pyramid with a vertex at its center.
Though we have many ways to perceive the fourth dimension, we as three-dimensional beings may never know which is correct.
References Radiya-Dixit, Anika. “Visualizing the Fourth Dimension.” Research Blog, 17 Oct. 2017, researchblog.duke.edu/2017/04/26/visualizing-the-fourth-dimension.
Sutter, Paul. “How The Universe Could Possibly Have More Dimensions.” Space.com, 21 Feb. 2020, www.space.com/more-universe-dimensions-for-string-theory.html.
Shereef, Ashif. “Fourth Dimension, General Theory of Relativity and Time — an Easy Explanation for Everyone.” Medium, 14 Dec. 2021, medium.com/@ashifshereef/fourth-dimension-time-and-god-748747c03d7e
JSTOR: Access Check. www.jstor.org/stable/2298325?seq=1#metadata_info_tab_contents. Accessed 11 Sept. 2022.
Webb, Richard. “What Is Time? The Mysterious Essence of the Fourth Dimension.” New Scientist, 17 June 2022, www.newscientist.com/article/mg25433910-500-what-is-time-the-mysterious-essence-of-the-fourth-dimension.
Ravisetti, Monisha. “The General Relativity Rabbit Hole: Unraveling Space, Time and the Fourth Dimension.” CNET, 8 Sept. 2022, www.cnet.com/science/features/the-general-relativity-rabbit-hole-unraveling-space-time-and-the-fourth-dimension.
“Why Are Gravity and Quantum Mechanics Incompatible?” Astronomy.com, 23 June 2014, astronomy.com/magazine/ask-astro/2014/06/gravity-and-quantum.
Stuart, Colin. “Was Einstein Wrong? The Case Against Space-time Theory.” Space.com, 28 Feb. 2022, www.space.com/end-of-einstein-space-time.
Rafi Letzter, SPACE.com. “Giant Molecules Exist in Two Places at Once in Unprecedented Quantum Experiment.” Scientific American, 8 Oct. 2019, www.scientificamerican.com/article/giant-molecules-exist-in-two-places-at-once-in-unprecedented-quantum-experiment/#:%7E:text=And%20waves%20occupy%20multiple%20places,demonstrated%20it%20using%20small%20particles.
“Physics in a Minute: The Double Slit Experiment.” Plus Maths, plus.maths.org/content/physics-minute-double-slit-experiment-0. Accessed 11 Sept. 2022.
Wood, Charlie, and Vicky Stein. “What Is String Theory?” Space.com, 20 Jan. 2022, www.space.com/17594-string-theory.html.
---. “Loop Quantum Gravity: Does Space-time Come in Tiny Chunks?” Space.com, 23 Feb. 2022, www.space.com/loop-quantum-gravity-space-time-quantized.
Ashish. “What Exactly Is a Tesseract?” Science ABC, 23 Dec. 2021, www.scienceabc.com/pure-sciences/what-exactly-is-a-tesseract-real-life-geometry-4-dimensional.html.