There are four fundamental forces at work in the universe; the strong force, the weak force, the electromagnetic force, and the gravitational force. The one we are all familiar with, the one that keeps us from floating off into space as we walk around, gravity is the weakest of the four. How can that be? Let’s see:
Gravitational Force
In Greece, Aristotle believed that objects fell toward the Earth because the Earth was the center of the Universe and attracted all of the mass in the Universe towards it.
While this was widely accepted other thinkers such as Plutarch[1] correctly predicted that the attraction of gravity was not unique to the Earth. In physics, gravity is a fundamental interaction that causes mutual attraction between all things with mass or energy. In this book, Newton described gravitation as a universal force, and claimed that “the forces which keep the planets in their orbs must [be] reciprocally as the squares of their distances from the centers about which they revolve.”
- on Earth, gravity gives weight to physical objects
- the Moon’s gravity is responsible for sublunar tides in the oceans
- growth of plants through the process of gravitropism[2]
- influencing the circulation of fluids in multicellular organisms
- investigation into the effects of weightlessness has shown that gravity may play a role in immune system function and cell differentiation within the human body
- the gravitational attraction between the original gaseous matter in the Universe allowed it to coalesce and form stars which eventually condensed into galaxies
- Gravity has an infinite range, although its effects become weaker as objects get farther away
Electromagnetic Force
Electromagnetism is a branch of physics involving the study of electromagnetic forces, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force is carried by electromagnetic fields composed of electric fields and magnetic fields, and it is responsible for electromagnetic radiation such as light.
Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force, which includes both electricity and magnetism as different manifestations of the same phenomenon.
Originally, electricity and magnetism were considered to be two separate forces. This view changed with the publication of James Clerk Maxwell’s 1873 “A Treatise on Electricity and Magnetism” in which the interactions of positive and negative charges were shown to be mediated by one force. The Aurora showing light created by charged particles and magnetism is a fundamental concept to electromagnetism study.
- the electromagnetic attraction between atomic nuclei and their orbital electrons holds atoms together
- responsible for the chemical bonds between atoms which create molecules, and intermolecular forces
- governs all chemical processes, which arise from interactions between the electrons of neighboring atoms
- widely used in modern technology, and electromagnetic theory is the basis of electric power engineering and electronics including digital technology
Strong Force
The strong interaction or strong nuclear force is a fundamental interaction that confines quarks into protons, neutrons, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, which is called the nuclear force.
Most of the mass of a common proton or neutron is the result of the strong interaction energy; the individual quarks provide only about 1% of the mass of a proton. The strong force is odd, though, because unlike any of the other fundamental forces, it gets weaker as subatomic particles move closer together.
It actually reaches maximum strength when the particles are farthest away from each other, according to Fermilab[3]. Once within range, massless charged bosons called gluons transmit the strong force between quarks and keep them “glued” together.
A tiny fraction of the strong force called the residual strong force acts between protons and neutrons. Protons in the nucleus repel one another because of their similar charge, but the residual strong force can overcome this repulsion, so the particles stay bound in an atom’s nucleus.
Weak Force
In nuclear physics and particle physics, the weak interaction, which is also often called the weak force or weak nuclear force, is one of the four known fundamental interactions. It is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms:
The weak interaction participates in nuclear fission and nuclear fusion. The theory describing its behavior and effects is sometimes called quantum flavourdynamics (QFD); however, the term QFD is rarely used, because the weak force is better understood by electroweak theory (EWT)[4].
The effective range of the weak force is limited to subatomic distances and is less than the diameter of a proton. The weak force is critical for the nuclear fusion reactions that power the sun and produce the energy needed for most life forms here on Earth. It’s also why archaeologists can use carbon-14 to date ancient bone, wood and other formerly living artifacts. Carbon-14 has six protons and eight neutrons; one of those neutrons decays into a proton to make nitrogen-14, which has seven protons and seven neutrons. This decay happens at a predictable rate, allowing scientists to determine how old such artifacts are.
Strength of the Force(s)
There are four fundamental forces at work in the universe: the strong force, the weak force, the electromagnetic force, and the gravitational force. They work over different ranges and have different strengths.
Gravity is the weakest but it has an infinite range. The electromagnetic force also has infinite range but it is many times stronger than gravity. The weak and strong forces are effective only over a very short range and dominate only at the level of subatomic particles.
The weak force is weaker than the strong force and the electromagnetic force, but it is still much stronger than gravity. The strong force, as the name suggests, is the strongest of all four fundamental interactions.
Three of the fundamental forces result from the exchange of force-carrier particles, which belong to a broader group called “bosons”. Particles of matter transfer discrete amounts of energy by exchanging bosons with each other.
- Strong Force – gluon
- Electromagnetic Force – photon
- Weak Force – W and Z bosons
Although not yet found, the “graviton” should be the corresponding force-carrying particle of gravity.
The outstanding question of the four fundamental forces is whether they’re actually manifestations of just a single great force of the universe. If so, each of them should be able to merge with the others, and there’s already evidence that they can.
Footnotes
- Plutarch was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo in Delphi. He is known primarily for his Parallel Lives, a series of biographies of illustrious Greeks and Romans, and Moralia, a collection of essays and speeches. Upon becoming a Roman citizen, he was possibly named Lucius Mestrius Plutarchus. [Back]
- Gravitropism is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either “artificial gravity” or natural gravity. It is a general feature of all higher and many lower plants as well as other organisms. Charles Darwin was one of the first to scientifically document that roots show positive gravitropism and stems show negative gravitropism. That is, roots grow in the direction of gravitational pull (i.e., downward), and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing upwards. [Back]
- Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Fermilab’s Main Injector, two miles in circumference, is the laboratory’s most powerful particle accelerator. The accelerator complex that feeds the Main Injector is under upgrade, and construction of the first building for the new PIP-II linear accelerator began in 2020. Until 2011, Fermilab was the home of the 3.90 mile circumference Tevatron accelerator. The ring-shaped tunnels of the Tevatron and the Main Injector are visible from the air and by satellite. Fermilab aims to become a world center in neutrino physics. It is the host of the multi-billion dollar Deep Underground Neutrino Experiment (DUNE) now under construction. On-site experiments outside of the neutrino program include the SeaQuest fixed-target experiment and Muon g-2. Fermilab continues to participate in the work at the Large Hadron Collider (LHC); it serves as a Tier 1 site in the Worldwide LHC Computing Grid. In the public realm, Fermilab is home to a native prairie ecosystem restoration project and hosts many cultural events: public science lectures and symposia, classical and contemporary music concerts, folk dancing and arts galleries. The site is open from dawn to dusk to visitors who present valid photo identification. [Back]
- In particle physics, the electroweak interaction or electroweak force is the unified description of two of the four known fundamental interactions of nature: electromagnetism and weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of the same force. Above the unification energy, on the order of 246 GeV, they would merge into a single force. Thus, if the temperature is high enough — approximately 1015 K —, then the electromagnetic force and weak force merge into a combined electroweak force. During the quark epoch (shortly after the Big Bang), the electroweak force split into electromagnetic and weak forces. [Back]
Further Reading
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