Every day, we conduct science experiments, posing an “if” with a “then” and seeing what shakes out. Maybe it’s just taking a slightly different route on our commute home or heating that burrito for a few seconds longer in the microwave. Or it could be trying one more variation of that gene, or wondering what kind of code would best fit a given problem. Ultimately, this striving, questioning spirit is at the root of our ability to discover anything at all. A willingness to experiment has helped us delve deeper into the nature of reality through the pursuit we call science. A select batch of these science experiments has stood the test of time in showcasing our species at its inquiring, intelligent best. Whether elegant or crude, and often with a touch of serendipity, these singular efforts have delivered insights that changed our view of ourselves or the universe. Here are ten such endeavours that could be hailed as the top science experiments of all time.
1). Reality is different for you and me
A team of physicists designed a quantum experiment that showed that facts actually change depending on your perspective on the situation. Physicists performed an experiment using photons in a tiny quantum computer, finding that the results were different at different detectors, depending on their perspectives. The experiments showed that, in the micro-world of atoms and particles that is governed by the strange rules of quantum mechanics, two different observers are entitled to their own facts. In other words, according to our best theory of the building blocks of nature itself, facts can actually be subjective.
2). Cause and effect might not go hand in hand
Researchers working with quantum gravity, a theoretical construct designed to unify the worlds of quantum mechanics and Einstein’s general relativity, showed that under certain circumstances an event might cause an effect that occurred earlier in time. Certain very heavy objects can influence the flow of time in their immediate vicinity due to general relativity. We know this is true. And quantum superposition dictates that objects can be in multiple places at once. Put a very heavy object (like a big planet) in a state of quantum superposition, the researchers wrote, and you can design oddball scenarios where cause and effect take place in the wrong order.
3). A tiny quantum computer turned back time
Time’s supposed to move in only one direction: forward. Spill some milk on the ground, and there’s no way to perfectly dry out the dirt and return that same clean milk back into the cup. A spreading quantum wave function doesn’t un-spread. Except in this case, it did. Using a tiny, two-qubit quantum computer, physicists were able to write an algorithm that could return every ripple of a wave to the particle that created it, unwinding the event and effectively turning back the arrow of time.
4). A quantum computer saw 16 futures
A nice feature of quantum computers, which rely on superpositions rather than 1s and 0s, is their ability to play out multiple calculations at once. That advantage is on full display in a new quantum prediction engine developed in 2019. Simulating a series of connected events, the researchers behind the engine were able to encode 16 possible futures into a single photon in their engine.
5). Quantum entanglement photographed
For the first time, physicists made a photograph of the phenomenon Albert Einstein described as “spooky action at a distance,” in which two particles remain physically linked despite being separated across distances. This feature of the quantum world had long been experimentally verified, but this was the first time anyone got to see it. Quantum entangled particles “communicate” faster than the speed of light and particles have no objective state until they are observed.
6). Light bends matter
While it’s easy to see matter bending light, just look through a prism, it’s rare to find light bending matter. But scientists saw just that in an experiment reported in March 2010. Researchers assembled flat ribbons of nanoparticles, tiny bits of matter only billionths of a meter long, in a darkened laboratory. Then when the ribbons were exposed to light, they curled up into spirals. The results could help engineers design new types of optics and electronics.
7). New antimatter particle
By smashing particles together at close to light speed inside an atom smasher, scientists created a never-before-seen type of matter: an anti-hypertriton. This particle is weird in many ways. First, it’s not normal matter, but its eerie opposite, called antimatter, which annihilates whenever it comes into contact with regular mass. Second, the anti-hypertriton is what’s called a “strange” particle, meaning it contains a rare building block called a strange quark, which isn’t present in the protons and neutrons that make up regular atoms. The experiment was conducted at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in Upton, N.Y. The results were announced in March 2010.
8). Matter may travel to the future in a black hole
Black holes run into the problem of infinity; a black hole’s mass is crushed to an infinitely dense point that’s infinitely small in size. Physically, this doesn’t make any sense, so researchers have searched for alternative frameworks to get a handle on black holes. One proposal is known as quantum loop gravity, which suggests that the fabric of space-time is curved very strongly near the centre of the black hole. This would result in part of the hole extending into the future, meaning that matter getting sucked into it would time travel forward.
9). Light lost track of time
Time is supposed to flow in one direction, following the path set for it by causality. But in the quantum realm, things are fuzzier. A team of scientists in 2018 sent a photon on a journey, one that should have taken it down path A and then path B, or path B and then path A. But that photon didn‘t follow one path before the other. It followed both of them, without bothering to pick an order.
10). 20 qubits got entangled
Qubits are the fundamental unit of information in quantum computers, and making quantum computers work will involve entangling them with each other. In 2018, an experiment managed to entangle 20 of qubits together and make them talk to one another, then read back the information they contained. The result was a sort of prototype of short-term memory for a quantum computer system.