When it pertains to the fundamental laws of nature, we can break every little thing down right into four forces that room at the main point of whatever in the Universe:

Thestrong atom force: the force responsible because that holding atom nuclei and also individual protons and neutrons together. Theelectromagnetic force: the force that attracts and also repels charged particles, binding atoms together into molecules and also life, and also causes electric current, among other things. Theweak atom force: the pressure responsible for some species of radioactive decay and the transmutation the heavy, unstable an essential particles right into lighter ones. Andgravity: the pressure that tie the Earth, the Solar System and also the stars and galaxies together.
The four basic forces in our Universe. Image credit: Wikimedia Commons user Kvr.lohith, under... <+> a c.c.a.-by-s.a.-4.0 worldwide license.

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Depending on how you look in ~ it, each force has a scale and a circumstance under which that shines over all others.

A helium atom, with the nucleus to approximate scale. Picture credit: Wikimedia Commons user Yzmo,... <+> under a c.c.a.-s.a.-3.0 unported license.

Go under to the smallest scales -- 10^-16 meters, or a million times smaller sized than one atom -- and also the strong nuclear pressure can get rid of all the others. Take it the helium nucleus, for example: 2 protons and two neutrons, bound with each other in a steady configuration. Even the electromagnetic repulsion between the 2 protons isn"t enough to get rid of the glue-like solid force holding the cell nucleus together. Even if you take a spirit away, leaving you through two protons and also just one neutron, the isotope that helium is secure as well. The solid force, at the tiniest distances, will certainly consistently get over all the others, and also hence under many circumstances have the right to be considered the strongest.

The galaxy Centaurus A, through its high-energy jets led to by electromagnetic acceleration. Image... <+> credit: NASA/CXC/CfA/R.Kraft et al.

But shot building her atomic nucleus too large and the electromagnetic force takes over. Uranium-238, for instance, will certainly spit out a helium cell nucleus every therefore often, together the repulsion in between the different parts the the cell core is too good for the solid force to hold it every together. Top top larger, cosmic scales, it"s the extreme magnetic fields generated by collapsed stars and also rapidly rotating, chargedmatter that can accelerate particles to the best energies in the Universe: the ultra-high power cosmic rays that bombard united state from all directions in the sky. Uneven the strong force, there"s no limit to the selection of the electromagnetic force; a proton"s electric field can be felt indigenous the various other side that the Universe.

Schematic illustration of nuclear beta decay in a substantial atomic nucleus. Photo credit: Wikimedia... <+> Commons user Inductiveload, produced in Inkscape and released right into the windy domain.

The weak atom force can seem the lousiest candidate for the the strongest force, given its name, however even this family member weakling has actually its moments to shine. Under the ideal conditions, the electromagnetic pressure (working come repel like-charged components) and also the solid nuclear force (working to bind nuclei together) have the right to cancel each various other out, permitting the very-short-range weak force to increase to prominence. Once it does, it deserve to make every the difference to the stability of a system, as it can reason radioactive (beta) decay, whereby a ghost transforms right into a proton, electron and also an anti-electron neutrino. Free neutrons, plenty of heavy elements and even Tritium, the rough isotope found in radiation (tritiated) water, all to mark of the strength of the weak force.

But on the largest scales -- ~ above the scale of galaxies, clusters of galaxies and more -- nobody of the above forces issue all that much. Even electromagnetism, whose range can extend across the Universe, doesn"t have actually much effect, because the number of positive dues (mostly protons) and also the number of an unfavorable charges (mostly electrons) shows up to be exactly equal. Even observationally, we deserve to constrain the charge difference inthe cosmos to be less than one part in 10^34. The cosmos is informing us that even though electromagnetism could be lot stronger 보다 gravity between any kind of two particles, if girlfriend get enough particles with each other that are as whole electrically neutral (or close to it), gravitation will be the only force that matters. Nuclear combination and the associated radiation press can"t even rip stars apart, together their gravitational attractive force overcomes the energetic outside push.

photo credit: Sloan Digital sky Survey, of IC 1101, the largest known individual galaxy in the... <+> Universe.

Clusters the galaxies and tremendous, large structures deserve to be found spanning an ext than a billion light years in size throughout the Universe. And yet, if friend go looking for structures 8, 10 or 15 billion irradiate years across, you will findabsolutely zero in the whole cosmos. The reason for it, quite puzzlingly, isn"t early to any of the forces we"ve mentioned, however rather come a phenomenon completely unexpected: dark energy.

The El Gordo Galaxy swarm (lower right), together imaged by the Dark power Camera. It is not bound to... <+> the various other structures in the image. Picture credit: Dark energy Survey.

On the largest scales, the fundamental, tiny amount of power inherent to space itself -- less than one Joule that energyper cubic kilometre of room -- is sufficient to overcome even the gravitational attraction in between the most enormous galaxies and clusters in the Universe. The result? An accelerated expansion, as the most far-off galaxies and clusters move farther and farther away from one an additional at ever before faster prices as time go on. On the biggest cosmic scales, even gravity doesn"t obtain its way.

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So who"s the strongest? Onthe smallest scales, it"s the strong force. To reach the highest possible energies, it"s the electromagnetic force. Because that the biggest bound structures, it"s gravity. And on the biggest scales the all, it"s the mysterious puzzle the dark energy. In terms of absolute magnitude, dark energy is the weakest point of all: it take it the world nearly fifty percent its age just to begin revealing that effects, and it wasn"t even uncovered by mankind until 1998. However the cosmos is a very huge place, and also when you add up the entire volume of an are and look come the much future, dark energy will be the only force that matters in the end.


I to be a Ph.D. Astrophysicist, author, and also science communicator, that professes physics and astronomy at miscellaneous colleges. I have won numerous awards for scientific research writing

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I to be a Ph.D. Astrophysicist, author, and also science communicator, who professes physics and astronomy at assorted colleges. I have actually won many awards for scientific research writing since 2008 because that my blog, Starts v A Bang, consisting of the compensation for ideal science blog through the academy of Physics. My two books, Treknology: The science of Star Trek indigenous Tricorders come Warp Drive, past the Galaxy: how humanity looked beyond our Milky way and found the whole Universe, are accessible for purchase at Amazon. Follow me ~ above Twitter