After thousands of years of research into nature and the laws that govern it, scientists have determined that four fundamental forces govern all matter-energy interactions.
These forces, and the fundamental particles that make up all matter quarks, leptons, gauge bosons, and scalar bosons , are part of The Standard Model of particle physics. These forces are:. The first three forces are all described by the field of Quantum Mechanics and are associated with specific subatomic particles. Electromagnetism is associated with electrons a lepton , which are responsible for electricity, magnetism, and all forms of electromagnetic radiation.
That includes visible light color , heat, microwaves, radio waves, ultraviolet radiation, and gamma rays. The weak nuclear force deals with interactions between subatomic particles responsible for the radioactive decay of atoms and is associated with particles smaller than a proton bosons.
At higher energies, this force merges with electromagnetism, which has given rise to the unified term "electroweak force. The strong nuclear force governs particles that are the size of protons and neutrons hadrons and is so-named because it is approximately times as strong as electromagnetism, millions of times stronger than the weak nuclear force, and 10 38 times as strong as gravitation.
It causes quarks to come together to form larger protons and neutrons and binds them to create atomic nuclei. Finally, there is gravitation, which is the weakest of the four forces and deals with interactions between massive objects asteroids, planets, stars, galaxies, and the large-scale structure of the Universe. Unlike the other three forces, there is no known subatomic particle that describes gravitation or gravitational interactions.
This is why scientists are forced to study physics in terms of QM or GR depending on the scales involved , but generally not both combined. Because of this, scientists have been trying to come up with a theoretical framework for unifying gravity with the other forces. Attempts to do so generally fall under the heading of "quantum gravity" or a Theory of Everything ToE.
Attempts to create a unified field theory of gravitation and electromagnetism can be traced to German physicist Theodor Kaluza — In , he published a paper where he presented an extended interpretation of Einstein's Field Equations. This theory was built on the idea of a 5D Universe, which included a dimension beyond the common 4D of space and time.
In , Swedish theoretical physicist Oskar Klein offered a quantum interpretation of Kaluza's 5D theory. In Klein's extension, the fifth dimension was curled up, microscopic, and could take the form of a circle that had a 10 cm radius. In the s, w ork was undertaken on the Kaluza field theory by Einstein and his colleagues at Princeton. By the s, the theory was formally completed and given the name Kaluza-Klein theory.
Each of these theories entails the existence of "extra dimensions," "hyperspace," or something similar. To summarize, ST states that the point-like particles of particle physics are actually one-dimensional objects called "strings. In one state, the string corresponds to the graviton, which is what causes gravitation.
Superstring theory, a variation on ST, requires the existence of 10 spacetime dimensions. These include the four dimensions immediately apparent to us length, width, depth, time and six more that are not. These extra six dimensions are curled up into a compact space. On order the string scale 10 cm we wouldn't be able to detect the presence of these extra dimensions directly because they're just too small. According to the theory, the fifth and sixth dimensions deal with possible worlds that began with the same initial conditions.
The fifth dimension encompasses worlds with slightly different outcomes than ours, while the sixth is where a plane of possible worlds would be visible. The seventh dimension is where one could see possible worlds that started with different initial conditions and then branched out infinitely — hence why the term "infinity" is used to describe them. The eighth dimension would similarly give us a plane of these "infinities," while in the ninth dimension , all possible Universes and laws of physics could be seen.
In the tenth dimension , anything and everything possible in terms of cosmic evolution are accessible. Beyond that, nothing can be seen by living creatures that are part of the spacetime continuum. M-theory , which combines five distinct superstring theories, posits the existence of 11 dimensions — ten spatial and one time.
If extra dimensions were large enough to allow the death bubble to form, the researchers found, it would have happened thousands of times already. The fact that we still exist is one circumstantial piece of evidence that other dimensions are ultra-tiny. The team calculated that they must be smaller than 16 nanometers, too small for their gravity to influence much in our world and hundreds of times smaller than previous calculations, Grossman reports.
The new study comes on the tail of another study about extra dimensions published in the Journal of Cosmology and Astroparticle Physics published in July.
Mara Johnson-Groh at LiveScience reports that one of the big questions in physics is why the expansion of the universe is accelerating. Once we know a dot's altitude, longitude, latitude, and position in time, we have the tools needed to plot its existence in the universe as we know it. String theory, also known as "superstring theory," aims to unify two main theories describing how the universe works: general relativity which applies to very large objects and quantum mechanics which applies to very small ones.
After coming up with a theory that hinges on the existence of 10 space dimensions, string theorists then had the job of explaining where those new dimensions were hiding.
Their answer: They are just as real as the "big" dimensions we can see, but the extra dimensions are curled up so tightly that they're too small for us to notice directly. Our basic understanding of physics makes this hard to process, but string theorist Brian Greene does a great job of framing the concept in terms most people can understand.
In his TED Talk , Greene compares these invisible dimensions to the cables connected to telephone poles: From a window, a wire looks like a one-dimensional line. But if we were to study it up close we'd see that the cord is actually round, making it three-dimensional. No analogy comparing unobservable dimensions to objects in the observable world can ever be perfect, but this illustrates how something so fundamental to reality could be hiding in plain sight.
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