Einstein was wrong
Revolutions are the lifeblood of science, as they have been throughout history. Unrest simmers underground until a new regime emerges to take control.
Then everyone's focus shifts to overthrowing their new ruler. The king is no longer alive, but long live the king.
In the history of physics and astronomy, this has happened many times. We used to believe that Earth was at the Centre of the solar system, a belief that had been held for almost 1,000 years.
Then Copernicus put his neck out there and said that if we were just another planet orbiting the sun, the entire system would be a lot easier.
The old geocentric vision gradually fell under the weight of evidence from the newly built telescope, despite strong initial criticism.
Then came Newton, who defined how gravity causes why the planets round the sun. According to him, all mass objects have a gravitational attraction to one another.
We orbit the sun because it pulls on us, and the moon orbits Earth because we pull on it, according to his theories.
Newton ruled for two and a half centuries until Albert Einstein arrived in 1915 with his General Theory of Relativity to replace him.
This new version perfectly explained Mercury's orbital inconsistencies, and it was widely confirmed by observations of a solar eclipse off the African coast in 1919.
Einstein saw gravity as the result of curved space rather than a pull. All objects in the universe, he claims, are wrapped in a smooth, four-dimensional fabric known as space-time.
Massive objects like the sun warp space-time around them, and Earth's orbit is the result of our planet following this curvature.
That appears to be a Newtonian gravitational pull to us. This space-time image has ruled the throne for over a century and has conquered all challengers to its reign.
The discovery of gravitational waves in 2015 was a huge step forward, but like its predecessors, it may be on the edge of collapsing. This is due to the fact that it is profoundly contradictory with the other great theory.
The quantum cosmos is famed for its strangeness. Single particles, for example, can exist in two places at the same time. We can only force it to 'select' by making an observation.
We can only give probabilities to the possible results prior to an observation. Erwin Schrödinger devised a famous technique to expose how preserve this concept is in the 1930s.
He visualized a cat trapped in a box with a vial of poison tied to a hammer. The hammer is connected to a gadget that measures a particle's quantum state.
The measurement determines whether the hammer breaks the vial and kills the cat, however quantum physics indicates that the particle is concurrently in both states until the measurement is made, which means the vial is both broken and unbroken, and the cat is both alive and dead.
A smooth, continuous fabric of space-time cannot rationalize such an image.
Sabine Hossenfelder, a theoretical physicist at the Frankfurt Institute for Advanced Studies, explained, "A gravitational field cannot be in two places at the same time." Matter and energy, according to Einstein, warp space-time, but quantum physics claims matter and energy can exist in numerous states at the same time – they can be here and there.
Hossenfelder questions, "Where is the gravitational field?" "That is a question to which no one has an answer. It's a little awkward, to be frank "she stated
When you try to integrate general relativity and quantum theory, it doesn't work. "You get probability that are larger than one over a certain energy," Hossenfelder explained.
One is the highest possible probability, implying that a result is guaranteed. It's impossible to be more certain than certain. Calculations can also result in the response infinity, which has no physical meaning.
As a result, the two theories are mathematically incompatible. So, like many emperors throughout history, scientists are attempting to reconcile competing factions in order to maintain peace.
They're looking for a quantum gravity theory, which would be the ultimate diplomatic maneuver to get these two rivals to share the throne. As a result, theorists have resort to some far-fetched scenarios.
String theory is arguably the most well-known. The idea is that subatomic particles like electrons and quarks are made up of tiny vibrating strings.
String theorists claim that different combinations of strings produce different particles, much as playing strings on a musical instrument produces different notes.
The theory's attraction is that, at least on paper, it can reconcile general relativity and quantum physics.
To get that particular rabbit out of the hat, however, the strings must vibrate in eleven dimensions, which is seven more than Einstein's space-time fabric.
There is currently no experimental proof that these extra dimensions exist. "It might be fascinating mathematics," said Jorma Louko of the University of Nottingham, "but we won't really know whether it describes the space-time in which we exist until there is an experiment."
Other scientists have come to an alternative termed Loop Quantum Gravity, partly influenced by string theory's alleged flaws (LQG).
They can make the two theories work together if they eliminate one of general relativity's basic tenets: That fabric of space-time is smooth and continuous.
They propose that space-time is made up of a series of linked loops, with structure even at the smallest scales. This resembles a swatch of fabric.
At first glance, it appears to be a single piece of smooth fabric. However, if you look closely, you'll notice that it's actually made up of a network of stitches.
Consider it in the same way you would an image on a computer screen: If you zoom in close enough, you can see that it is made up of individual pixels.
The issue is that when LQG physicists say little, they mean tiny. These flaws in space-time would only be seen at the Planck scale, which is roughly a trillionth of a trillionth of a trillionth of a trillionth of a meter.
That's so little that a cubic centimeter of space would contain more loops than the entire observable universe's cubic centimeters.
"If the sole difference between space and time is on the Planck scale, this would be difficult to demonstrate in any particle accelerator," Louko adds.
You'd need a 1,000-trillion-times more powerful incinerator than CERN's Large Hadron Collider (LHC). So, how do you discover such minute space-time defects? The solution is to scan a broad area of space.
Light has traveled across billions of light years of space-time to reach us from the distant regions of the universe.
While each space-time defect would have a minor effect, interactions with several defects over long distances could pile up to a potentially visible effect.
Astronomers have been searching for evidence of LQG using light from far-off Gamma Ray Bursts over the past decade.
These cosmic flashes are caused by massive stars collapsing at the end of their lives, and there is something mysterious about these far-off explosions.
"Their spectrum has a consistent deformation to it," Hossenfelder said, but no one believes if that's something that arises on the way here or something to do with the bursts' origins. The decision is still out for one.
To make real progress, we may have to go beyond Einstein's suggestion that space-time isn't a seamless, continuous fabric.
Space-time, according to Einstein, is like a stage that remains in place whether or not people are on the stage-space-time would still exist even if there were no stars or planets moving around.
Laurent Freidel, Robert Leigh, and Djordje Minic, physicists, believe that this concept is holding us back. They believe that space-time does not exist without the objects that make it up.
The way objects interact defines space-time. Space-time would therefore become an artifact of the quantum realm, rather than something to be mixed with it.
It may sound strange," Minic explained, "but it is a really accurate response to the problem."
The attractiveness of this theory, known as modular space-time, is that it may be able to help solve another long-standing difficulty in theoretical physics involving locality, as well as a well-known quantum physics phenomena known as entanglement.
Phycisists can create a circumstance in which two particles are brought together and their quantum properties are linked.
They then isolate them by a significant distance and discover that they are still connected.
Change the qualities of one, and the properties of the other will change instantly, as if information had traveled faster than the speed of light between them, in direct violation of relativity.
This phenomena disturbed Einstein so much that he coined the phrase "spooky action at a distance."
By rethinking what it means to be separated, modular space-time theory can support such behavior.
If space-time originates from the quantum world, being closer quantumically is more fundamental than being physically close.
It depends on the situation," Minic explained, "different observers would have different concepts of locality." It's similar to our interpersonal connections.
We can feel more connected to a loved one who lives across the street than to a stranger who lives down the street. "As long as they're modest, you may have these non-local links," Hossenfelder added.
For the past five years, Freidel, Leigh, and Minic have been working on their idea, and they claim they are moving in the right direction.
"We want to be cautious and take things slowly," Minic explained, "but it's fascinating and thrilling."
It's a unique approach, as it seeks to "gravitationalize" the quantum universe rather than quantize gravity as LQG does. However, as with every scientific theory, it must be put to the test.
The three is currently figuring out how to incorporate time into their model.
This may all look particularly abstract, like something only academics should be interested about, yet it has the potential to have a far greater impact on our daily lives.
"We sit in space, we journey through time, and if our knowledge of space-time changes, it will have an influence not only on our understanding of gravity, but also on quantum theory in general," Hossenfelder added.
"Quantum theory is the only reason why all of our latest technology work. If we have a greater understanding of the quantum structure of space-time, it will have an impact on future technologies — perhaps not in 50 or 100 years, but perhaps in 200 ", she stated.
The existing principle is reaching the end of his reign, and a new challenger is long overdue, but we can't decide which of the many alternatives is the most likely to succeed. When we do, the ensuing revolution might benefit everyone, not just theoretical physics.