We are always looking for something more. And even our best guesses often don't let us know where we will find it. In the 19th century, we argued about why the sun burns - gravity or combustion, without even suspecting that thermonuclear fusion was involved. In the 20th century, we argued about the fate of the universe, without even assuming that it was accelerating into nothingness. But revolutions in science are real, and when they happen, we have to revise a lot of everything - sometimes even everything - that was previously believed to be true.
There are many fundamental truths in our knowledge that we rarely question, but perhaps we should. How confident are we in the tower of knowledge that we have built for ourselves?
How True Is Our Science?
According to the light aging hypothesis, the number of photons per second we receive from each object decreases in proportion to the square of the distance to it, while the number of objects we see increases with the square of the distance. Objects should be redder, but emit a constant number of photons per second depending on the distance. However, in an expanding universe, we receive fewer photons per second over time, as they have to travel long distances as the universe expands, and their energy also decreases during redshift. The brightness of the surface decreases with distance - this is consistent with our observations.
If the faster-than-light neutrinos that were talked about a few years ago turned out to be true, we would have to reconsider everything we knew about relativity and the speed limit in the universe. If Emdrive or another perpetual motion machine turned out to be real, we would have to revise everything we knew about classical mechanics and the law of conservation of momentum. Although these specific results were not reliable enough - those neutrinos appeared due to experimental error, and Emdrive has not been tested at any level of significance - one day we may well face such a result.
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The most important test for will not be whether we get to such an intersection. Our true belief in scientific truth will be tested when we have to decide what to do about it.
An experimental EmDrive setup at NASA Eagleworks, where they tried to conduct isolated tests of a reactionless engine. They found a small positive result, but it was not clear whether it was connected with new physics or with a systematic error. The results did not appear reliable and could not be repeated independently. The revolution has not happened - yet.
Science is simultaneously:
- A body of knowledge encompassing everything we have learned from observing, changing, and experimenting in our universe.
- The process of constantly questioning our assumptions, trying to find holes in our understanding of reality, looking for logical loopholes and inconsistencies, and defining the limits of our knowledge in new, fundamental ways.
Everything that we see and hear, everything that our instruments find, and so on - all of this can be an example of scientific evidence, being correctly recorded. When we try to compose a picture of the universe, we must use the full set of scientific data available. We cannot choose results or evidence that matches our preferred conclusions; we have to collide all our ideas with every example of good data that exists. To do science well, we must collect this data, put it piece by piece in a self-consistent structure, and then subject it to all sorts of tests, in any way imaginable.
The best job a scientist is capable of is trying to constantly refute, not prove, the most sacred theories and ideas.
The Hubble Space Telescope (left) is our largest flagship observatory in the history of astrophysics, but much smaller and less powerful than the future James Webb (center). Of the four proposed flagship missions for the 2030s, LUVOIR (right) is the most ambitious. By trying to reach the dimmest of the universe, see them in high resolution and at all possible wavelengths, we can improve and test our understanding of the cosmos in an unprecedented way.
This means increasing our precision to every additional decimal place we can add; this means chasing higher energies, lower temperatures, smaller scales and larger sample sizes; this means going beyond the known range of validity of the theory; this means theorization of new observed effects and the development of new experimental methods.
At some point, you inevitably find something that does not fit into the framework of acquired wisdom. You find something contrary to what you expected to find. You get a result that contradicts your old, already existing theory. And when that happens - if you can validate this contradiction, if it stands up to scrutiny and actually shows itself to be very, very existing - you will achieve something excellent: you will have a scientific revolution.
One of the revolutionary aspects of relativistic motion, put forward by Einstein, but previously laid by Lorentz, Fitzgerald and others, was that fast moving objects seemed to contract in space and slow down in time. The faster you move relative to something at rest, the more your length contracts and the more time slows down relative to the outside world. This painting - relativistic mechanics - replaced the old Newtonian view of classical mechanics.
The Scientific Revolution, however, involves more than just the "old truths are wrong!" This is just the first step. It may be a necessary part of the revolution, but in itself it is not sufficient. We could move on simply by noticing where and how our old idea is failing us. To move science forward - and significantly - we need to find a critical flaw in our previous way of thinking and rethink it until we arrive at the truth.
To do this, we need to overcome not one, but three major obstacles in our efforts to improve our understanding of the universe. There are three components that go into revolutionary scientific theory:
It should reproduce all the success of an already existing theory.
It must explain new results that were contrary to the old theory.
It must make new, testable predictions that have not been tested before, and which can either be confirmed or disproved.
This is an incredibly high bar that is rarely reached. But when it is achieved, the rewards are unlike anything else.
One of the great mysteries of the 1500s was that the planets move in an apparent retrograde - that is, in the opposite direction. This could be explained by either Ptolemy's geocentric model (left) or Copernicus's heliocentric model (right). However, figuring out the details with high precision required theoretical breakthroughs in our understanding of the rules underlying the observed phenomenon, which led to Kepler's laws and Newton's theory of universal gravity.
The newcomer - a new theory - always bears the burden of proving, replacing the previous dominant theory, and this requires her to solve a number of very difficult problems. When heliocentrism appeared, it had to explain all the predictions of planetary motions, take into account all the results that heliocentrism could not explain (for example, the motion of comets and Jupiter's moons), and make new predictions - such as the existence of elliptical orbits.
When Einstein proposed general relativity, his theory was supposed to reproduce all the successes of Newtonian gravity, as well as explain the precession of the perihelion of Mercury and the physics of objects whose speed approaches light, and moreover, she needed to make new predictions about how gravity bends stellar shine.
This concept extends even to our thoughts about the origin of the universe itself. For the Big Bang to become famous, it had to replace the old idea of a static universe. This means that it had to correspond to the general theory of relativity, explain the Hubble expansion of the Universe and the ratio of redshift and distance, and then make new predictions:
- On the existence and spectrum of the cosmic microwave background
- On the nucleosynthetic content of light elements
- On the formation of a large-scale structure and properties of clustering of matter under the influence of gravity.
All this was required only to replace the previous theory.
Now think about what it would take to replace one of the leading scientific theories today. This is not as difficult as you might imagine: it would take just one observation of any phenomenon that contradicts the predictions of the Big Bang. In the context of general relativity, if you could find a theoretical consequence that the Big Bang does not correspond to our observations, we would really be on the verge of revolution.
And here's what is important: it will not follow from this that everything about the Big Bang is wrong. General relativity does not mean that Newtonian gravity is wrong; it only imposes restrictions on where and how Newtonian gravity will be applied successfully. It will still accurately describe the Universe born of a hot, dense, expanding state; describe the observable Universe with an age of many billions of years (but not infinite age) in the same way; he will also tell about the first stars and galaxies, the first neutral atoms, the first stable atomic nuclei.
The visible history of the expanding universe includes the hot, dense state of the Big Bang and the subsequent growth and formation of structure. The complete dataset, including observations of light elements and the cosmic microwave background, leaves only the Big Bang as a suitable explanation for what we see. The prediction of the cosmic neutrino background was one of the last big unconfirmed predictions to emerge from the Big Bang theory.
Whatever comes up on this theory - whatever goes beyond our current best theory (and this applies to all scientific fields) - the first step is to reproduce all the successes of this theory. Static Universe Theories That Fight the Big Bang? They are unable to do this. The same goes for the electric universe and cosmological plasma; the same can be said about tired light, about a topological defect and cosmic strings.
Perhaps someday we will make enough theoretical progress for one of these alternatives to turn into something corresponding to the full set of observables, or perhaps a new alternative will appear. But this day is not today, and in the meantime, an inflationary Universe with a Big Bang, with radiation, ordinary matter, dark matter and energy, explains the full set of absolutely everything that we have ever observed. And she's one of a kind, for now.
But it's important to remember that we arrived at this picture precisely because we didn't focus on one dubious outcome that could collapse. We have dozens of lines of independent evidence that lead us to the same conclusion over and over again. Even if it turns out that we don't understand supernovae at all, dark energy will still be needed; even if it turns out that we do not understand the rotation of galaxies at all, dark matter will still be needed; even if it turns out that the microwave background does not exist, the Big Bang will still be necessary.
The universe may turn out to be completely different in detail. And I hope I live long enough to see a new Einstein emerge that challenges modern theories - and wins. Our best theories aren't wrong, they're just not complete enough. And this means that they can only be replaced by a more complete theory, which will inevitably include everything, in general everything in this world - and explain it.
Ilya Khel