Ever since Isaac Newton and the falling apple, surprises have usually pushed physics ahead. Many truths concerning the universe we dwell in and the particles that make up ourselves and the world round us, in addition to the forces that drive them, appeared to come back out of left area after they had been first found. For example, scientists as soon as thought atoms had been the smallest bits of matter in existence till they break up atomic nuclei to search out protons and neutrons, which in flip proved to be made from even smaller basic particles, referred to as quarks. And it was lower than 100 years in the past that researchers came upon the Milky Method wasn’t the one galaxy within the cosmos however somewhat certainly one of billions.

The surprises within the historical past of physics are far too many to comprehensively describe, however we polled quite a lot of physicists for a few of their favorites. Just a few discoveries, resembling the accelerating enlargement of the universe, had been so groundbreaking that a number of specialists picked them as prime selections. And lots of of those occasions occurred comparatively lately, displaying that the sphere of physics continues to astound us. Right here’s a collection of physicists’ responses on probably the most wonderful, gorgeous and flabbergasting findings.

Darkish Power

Some of the stunning findings within the historical past of physics was the invention of darkish power simply earlier than the flip of the millennium. None of us working in physics noticed that coming! The observations that distant supernovae are dimmer than anticipated led to the concept that the universe is not only increasing however accelerating. These objects are very properly understood, regardless of how far again in time they’re noticed, so different explanations simply don’t work. The title “darkish power” was given to the fabric that causes this acceleration. After the preliminary discovery, many different observations of various varieties confirmed this consequence, resembling research of the cosmic microwave background, which is the leftover mild from the massive bang, and research of clusters of galaxies. The record goes on and on. We now have an ordinary mannequin of cosmology by which the peculiar matter and power that we expertise in our each day lives—our physique, the air we breathe, the partitions round us, and all the celebs and planets—add as much as solely 5 p.c of the content material of the universe. Many of the universe is “the darkish facet”: the universe is believed to include 25 p.c darkish matter and 70 p.c darkish power. I, for one, am working to determine the character of those mysterious elements.

This discovery of darkish power particularly created a paradigm shift. The best clarification [for dark energy] could be a cosmological fixed initially launched by Albert Einstein as a doable time period within the equations of the final concept of relativity however then deserted by him as his “greatest blunder.” Now it appears he might have been proper in any case. The difficulty is that the expected worth for the cosmological fixed from calculations utilizing quantum area concept produces a quantity that’s too massive by an element of 10¹²⁰. Editor’s Word: If the fixed was this massive, the universe would have expanded a lot, a lot sooner than it did.] This conundrum has been identified for a while, and theorists conjectured that there should be some physics that drives the quantity all the way down to zero as a substitute [to match the observed expansion history of the universe]. Now with the invention of darkish power, nonetheless, the quantity should be pushed all the way down to a selected tiny worth [rather than zero to explain the accelerating expansion], which is way tougher to elucidate. This cosmological fixed downside is believed by many to be the deepest unsolved issues in all of recent physics.” —Katherine Freese, College of Texas at Austin

Increasing Universe

I believe the accelerating enlargement of the universe needs to be a powerful contender. I’ve learn references revealed round 1990 that speak confidently about how we’ll quickly use supernovae to measure the speed at which the enlargement of the universe is decelerating and the curvature of the cosmos and the way it will inform us concerning the final destiny of our universe (as a result of closed matter-dominated universes bear a ‘massive crunch,’ whereas open ones broaden endlessly)—little or no of which applies to the dark-energy-dominated, spatially-flat cosmos that we seem to really dwell in! I believe this additionally qualifies as a result of even with the advantage of hindsight, it nonetheless appears very shocking that the darkish power/cosmological fixed has its measured worth. —Tracy Slatyer, Massachusetts Institute of Know-how

Charmed Quarks and Accelerating Cosmos

Essentially the most spectacular discoveries in basic physics since I began graduate faculty in 1973 have been the next:

(1) The invention in October 1974 of the J/psi particle, interpreted when it comes to a brand new quark, the charmed quark, which gave dramatic affirmation to the then rising Commonplace Mannequin of particle physics.

(2) The invention within the late Nineteen Nineties that the enlargement of the universe is accelerating, apparently due to a tiny however nonzero power density of the vacuum, upending lots of our concepts concerning the cosmos. —Edward Witten, Institute for Superior Research, Princeton, N.J.

Black Holes

Some of the shocking discoveries within the historical past of physics is Karl Schwarzschild’s black gap answer of the Einstein equation. [Editor’s Note: Schwarzschild calculated the first exact solution to Einstein’s field equation of general relativity, and the solution predicted the existence of black holes.]

It’s apocryphally stated that when Einstein found his extremely nonlinear equation, he thought an actual answer would by no means be discovered, however Schwarzschild proved him mistaken solely months later. But the construction of the answer was so shocking that many thought black holes didn’t exist. Einstein himself wrote in 1939 that [“the ‘Schwarzschild singularities’ do not exist in physical reality”]. It’s only a century later, with the latest direct LIGO [Laser Interferometer Gravitational Wave Observatory] and EHT [Event Horizon Telescope] observations of black holes that the final shreds of disbelief have been stamped out.” —Andrew Strominger, Harvard College

Spacetime

It’s bought to be the pliability of spacetime. Let’s say I hop on a very quick rocket or go very near a black gap after which return to the place I began. If I’m going quick sufficient on the rocket or go shut sufficient to the black gap, I can have solely 10 minutes go by on my watch whereas 10,000 years go by for Earthlings. That is an experimentally verified time machine that allows you to journey to the longer term! —Edgar Shaghoulian, College of California, Santa Cruz

Neutrinos

I believe my favourite occasion in physics was the prediction of the existence of the neutrino [a subatomic particle with no charge and very little mass] as a result of a lot of our basic strategy to physics as we speak grew out of that second. The neutrino prediction by Wolfgang Pauli was one of many first examples of taking power and momentum conservation severely—you will need to both clarify nuclear beta decay [a common radioactive process] by violating this conservation regulation or by introducing a brand new particle. The neutrino could be the primary new particle predicted that wasn’t apparent in on a regular basis life. As we speak predictions for brand new ghostlike particles are nearly a dime a dozen, however within the early a part of the final century, introducing probably unobservable particles merely wasn’t performed. When Enrico Fermi launched the interplay explaining why the neutrino was so unlikely to be noticed, he predicted the primary new drive [the weak nuclear force] past the 2 which are apparent in on a regular basis life (gravity and electromagnetism). As we speak physicists contemplate many new kinds of forces on a regular basis, however again then that simply wasn’t within the image. The concept of unifying forces, which is so important to physics as we speak, grew out of the invention of Fermi’s ‘weak drive’ that the neutrino feels. Some of the wonderful examples that reveals quantum mechanics is sensible as a concept, as a result of it may well occur on kilometer scales, the place we will actually see it, comes from neutrino physics. In order that second, when Pauli predicted the neutrino, is my favourite shock due to all of the paths it led to in physics. —Janet Conrad, Massachusetts Institute of Know-how

Oscillations

I’d say the invention of neutrino oscillations is up there for me. Neutrinos themselves had been predicted to exist by Pauli and subsequently found in a terrific demonstration of the ability of concept. However what makes neutrinos extremely fascinating little particles is the truth that they’ve mass and may change flavors, which requires a modification of the Commonplace Mannequin of particle physics. —Sanjana Curtis, College of Chicago

Leucippity

Way back two historical Greek savants, Democritus and Leucippus, argued that matter consists of atoms, a notion that may be confirmed greater than two millennia later. I lately coined the phrase ‘leucippity’ to characterize these speculative hypotheses that wait a few years for widespread acceptance. My new phrase honors the elder of the 2 proponents of the atomic speculation, Leucippus.

Isaac Newton concluded that mild consists of particles in 1672; Christiaan Huygens developed his wave concept of sunshine six years later. Who bought it proper? The query lingered for 2 centuries till James Clerk Maxwell’s profound and leucippitous discovery that mild favors Huygens’s wave concept. (Afterward Einstein would have his say on this matter.) Leucippity abounds in science. Alfred Wegener’s prescient ‘geopoetry’ of drifting continents emerged because the mature science of plate tectonics half a century afterward. Extra lately, the invention of a boson [the Higgs boson] first imagined by Peter Higgs and some others in 1964 was triumphantly introduced at CERN [the European laboratory for particle physics near Geneva] on July 4, 2012. Lastly, the gravitational waves produced by mergers of black-hole pairs had been detected by LIGO in 2015, a full century after their existence had been proposed by Einstein. Leucippity once more! —Sheldon Lee Glashow, Harvard College

Part Transitions

For my part, some of the unimaginable and shocking experimental findings in physics resulted from when the pioneer of helium liquefaction, Heike Onnes, carried out experiments by which he cooled metals resembling gold, platinum and mercury to liquid helium temperatures. On the identical day that he discovered that {the electrical} resistance of mercury dropped to successfully zero at liquid helium temperatures, he additionally discovered that [using a vacuum pump] on a traditional liquid helium pattern precipitated the liquid to additional cool and aggressively boil earlier than all of the sudden changing into placid. That is unimaginable! On the identical day Onnes found each the part transition to a state of superconductivity in mercury and the part transition to the state of superfluidity in helium. —Charles Brown, Yale College

Bell and Michelson-Morley

Two discoveries—Bell’s theorem and the Michelson-Morley interferometry experiment—upended our understandings of house, time and the character of actuality, so I can’t resist voting for them each.

The American Bodily Society calls the Michelson-Morley experiment “what may be considered probably the most well-known failed experiment thus far.” Till the experiment was carried out in 1887, scientists believed that mild waves propagate via a medium that scientists referred to as the luminiferous aether. In spite of everything, sound waves propagate via air, and surfers’ waves propagate via water. However Albert Michelson and Edward Morley offered robust proof that mild is totally different; it wants no medium. This lack paved the trail for Einstein’s particular concept of relativity (nothing can journey extra rapidly than mild, E = mc² [the c stands for the speed of light in a vacuum], how brief an object seems to be will depend on how rapidly you’re shifting relative to it, etcetera), which led to his basic concept of relativity (spacetime has a form).

Bell’s theorem [named after John Stewart Bell] revealed that quantum programs have wonky relationships with data and with one another. Ordinarily, if you recognize the whole lot a couple of pair of programs—say, the whole lot a couple of pair of individuals named Audrey and Baxter—then you recognize the whole lot about every particular person—the whole lot about Audrey and the whole lot about Baxter. But when Audrey and Baxter are labels of quantum particles, then you possibly can know the whole lot concerning the pair with out understanding something concerning the people. Data might be not in a single particle and never within the different however type of within the relationship between the 2: the entire is larger than the sum of its components in quantum physics. Bell’s perception paved the trail for the quantum computer systems and networks now underneath development the world over. —Nicole Yunger Halpern, College of Maryland, creator of Quantum Steampunk

High 5

Listed below are a couple of shocking discoveries that pop into my thoughts, in no explicit order:

(1) Particular relativity: the truth that the velocity of sunshine is fixed, regardless of the body of reference.

(2) Basic relativity: the truth that gravity represents a curvature of spacetime.

(3) The enlargement of the universe, the following massive bang mannequin and the truth that the enlargement is accelerating.

(4) The ‘unreasonable’ effectiveness of arithmetic in formulating the basic legal guidelines of nature.

(5) The probabilistic nature of quantum mechanics. —Mario Livio, astrophysicist