Written by Kevin Jennings
There are a lot of bizarre theories about the universe. Some of them are already debunked, bordering on conspiracy theories, or just downright silly. Others are merely cosmic thought experiments; they can’t be proven one way or the other, and are just ideas designed to challenge what we believe about the universe around us.
While insane conspiracy theories and unprovable thought experiments can be fun, today we’ll be looking at four theories that may actually be true, and one that almost certainly is but we’d prefer if it wasn’t.
There’s a Fourth Spatial Dimension
One of the major problems in the standard model of physics is trying to explain why the gravitational force is so weak when compared to the other three natural forces. According to theory, at the time of the Big Bang all four forces should have existed as one before breaking off into the four forces we observe today, but at the point when they split they should have been comparable in strength. Why, then, is gravity so weak?
String theory attempted to address this problem by positing that, at tiny enough distances, the forces could be equal in magnitude. It’s not an ideal answer, and scientists kept searching. In 1983, the idea of brane cosmology was introduced, though the most influential model would not be proposed until 1999 by physicists Lisa Randall and Raman Sundrum.
This idea of brane cosmology, also referred to as Braneworld, is that there is at least a fourth spatial dimension, possibly even more. We’re all familiar with the three spatial dimensions plus the fourth time dimension in which we exist, and that seems to be pretty encapsulating of the entire universe. How then could further spatial dimensions exist?
The answer is that our universe is trapped inside a membrane, hence the “brane” in the theory’s name. Our visible universe exists entirely within this membrane while the majority of what exists, also referred to as “the bulk”, is some sort of higher-dimensional space outside the membrane. It may sound a little farfetched, but this theory is being seriously pursued by scientists as a possible solution to many of the unanswered questions about the universe.
Under this theory, the weak and strong nuclear forces and the electromagnetic force are trapped within the membrane, but the gravitational force has no such restriction. As such, much of the gravitational force leaks out into the bulk, accounting for why it is so comparatively weak. Similarly, other membranes could exist next to ours which also influence the gravitational force.
There could be other universes trapped in their own membranes only a microscopic distance away from ours, but because they could exist in spatial dimensions that are completely imperceptible to us we would have no idea that they were there.
It is regarded as one of the more elegant solutions for the hierarchy problem, and experiments have been designed to try to prove the existence of large extra dimensions. Thus far these have not yielded any results other than to constrain what the extra dimensions could actually be. Then again, because we are trying to test for extra special dimensions that we don’t actually know how to perceive, detecting evidence of their existence may prove more complicated than we’ve realized.
Gravity May Be Wrong
Once again, we find ourselves faced with the issue of gravity. The gravitational force was naturally the first of the four forces that humans discovered: if you drop something, it falls down. Seems pretty straightforward. However, of the four natural forces, gravity is the one that we understand the least.
We do have a pretty good idea of how gravity works, or at least we think we do, despite the hierarchy problem presented by it being so many orders of magnitude weaker than the other forces. However, we have seen other issues related to our understanding of gravity as well.
One such problem is the speed at which celestial bodies move. We can observe galaxies rotating much faster than they should be able to or see galaxies traveling away from us at speeds far exceeding what should be possible.
Scientists have proposed a solution to this dilemma in the form of dark matter. Dark matter is everywhere in the universe, accounting for roughly 85% of all matter. It is six times more abundant than the visible matter we are familiar with. This dark matter, and the gravity exerted by its mass, is the reason we see objects moving in ways that would otherwise be impossible to explain.
However, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect, or emit light, making it completely invisible; that’s how it got its name. The only problem is that because it’s invisible, we have no proof that dark matter actually exists. The only proof for the existence of dark matter is the gravitational effect it has on other objects throughout the universe.
As you may have noticed, there’s a bit of a logical problem there. The only proof we have that dark matter exists is the gravitational effect it has, but dark matter was proposed as a theoretical solution for gravitational effects that we otherwise couldn’t explain. It’s somewhat circular reasoning, which is why experiments like those at the Large Hadron Collider hope to provide more concrete proof for the existence of dark matter.
However, there is another possible solution: we could be wrong. Not just about dark matter, but about gravity itself. In fact, we already know that the current theories of gravity are wrong, and this isn’t the first time we’ve made that discovery.
Gravity as put forth by Isaac Newton worked great for a while. He described gravity as an attractive force, but there were some problems. For example, Mercury’s orbit moved closer to the sun at a faster rate than Newton’s equations predicted. Einstein’s general relativity solved this problem and changed our understand of gravity
Rather than being an attractive force, Einstein saw gravity as warping spacetime around on object, thus creating a well that other things would fall towards. This new understanding remained consistent with everything that was expected from Newtonian physics while also correcting issues in the areas where Newton’s formulas didn’t work.
Unfortunately, general relativity breaks down as well, we just aren’t exactly sure where. We know that at some point within a black hole that Einstein’s theory stops working, and researchers are currently working to figure out where. Once we know the exact point where it breaks down, we may be able to figure out exactly what was wrong.
Until that happens, it’s hard to say exactly what the fate of gravity will be. Perhaps our new understanding of the gravitational force will still require the existence of dark matter, or perhaps we will learn that our beliefs about gravity were so fundamentally flawed that dark matter is no longer necessary to reconcile our expectations with reality.
The Speed of Light May Have Once Been Faster
If you’ve ever taken a physics class, you undoubtedly know that the speed of light in a vacuum is 300,000 km/s (186,000 m/s), and that is the fastest anything in the universe can travel. At colder temperatures, light moves more slowly. Not because of the temperature itself, but because colder temperatures make air more dense and light travels more slowly through denser objects.
But what if this worked in the other direction as well? It’s hard to imagine it being hot enough for a vacuum to somehow become even more of a vacuum. However, one theory suggests that at the origins of the universe it was so hot that light essentially underwent a phase change, like water turning into steam. As a result of this change, light was able to far exceed its current maximum speed, approaching effectively infinite speed.
This theory was proposed as an alternative to inflation theory, the most commonly accepted explanation for the horizon problem and cosmic microwave background, or CMB. The horizon problem is that the temperature across the universe is even, which should not be possible. Likewise, CMB is the oldest measurable light in the universe having been emitted about 300,000 years after the Big Bang, and the light is equivalent everywhere.
The consistency of CMB shows that the temperature across the universe should have been the same, but this doesn’t make logical sense as the universe was so big that light and thusly heat should not have reached all of it.
The inflation theory proposes that a fraction of a second after the Big Bang, the universe underwent a massive, exponential expansion outward that lasted for only a fraction of a second. As spacetime expanded exponentially, the existing light and heat was carried with it and then propagated as normal. It’s an elegant solution that answers a lot of problems, and because it only happened once billions of years ago it is completely untestable.
In addition to being an untestable theory, it raises the question of why. Why would this have happened, why for only such a short time, and why never again? These are questions that we don’t really have answers for.
Because of the untestable and difficult to rationalize nature of inflation, the alternate theory was proposed that extremely high temperatures allowed light to travel at incredible speeds following the Big Bang. This would run contrary to Einstein’s theory of special relativity, but it does hold one advantage over inflation theory: the physicists who proposed the most recent iteration of this theory believe they can prove it.
It is believed that in the near future the idea of a previously variable speed of light could be tested. If so, this theory will live or die by the results of those experiments. It’s impossible to predict what the results would be, but if testing were to confirm this theory, it would require rethinking much of what we believe we know about physics.
Adolf Hitler Could Make First Contact with Extraterrestrials
We’re not proposing that Hitler, at the age of 133, is alive and well in South America and will soon be launching himself into space to make first contact with an alien civilization, though such a conspiracy theory probably exists. Instead, we’ll looking at an idea first presented by Carl Sagan in his 1985 novel Contact, which was later adapted into a 1997 film starring Jodie Foster.
Humanity has been broadcasting messages into space for decades, though much of it wasn’t intentional. Most signals that were transmitted over the airwaves were either at too low a frequency or too low power to escape Earth’s ionosphere. However, as Sagan put forth, the first signal broadcast that was powerful enough to escape Earth’s atmosphere and travel into outer space was the opening ceremony of the 1936 Olympic Games in Berlin. This could make Hitler’s opening speech at the Olympics an alien civilization’s first encounter with humans.
Though Contact was a fiction novel, it was based in hard science. Many scientists dispute the claim that this will be the first transmission received by extraterrestrials, but they do admit it’s possible. Although the signal was relatively weak compared to messages that have been beamed into space with more clear intent, it could easily travel hundreds if not thousands of light years into space.
Those scientists believe that because of the low intensity of the signal, it is likely to be missed. They state that aliens would need to be listening to the void of space extremely intently in order to find the signal. While that is true, there’s no reason to believe that they wouldn’t be doing exactly that. After all, we certainly are.
The bigger obstacle would be that whatever civilization were to encounter this broadcast may have no way to decode it. They would certainly recognize it as a technological broadcast of some kind instead of something naturally occurring, but that doesn’t mean they would be able to separate the audio and visual information from the signal and reproduce the video that was being broadcast around Earth.
It’s understandable that scientists would want to try to debunk this theory as best as possible given the rather noncontroversial sentiment that Hitler was bad. However, there is no denying that the Olympic broadcast was almost certainly the first manmade signal powerful enough to break through the ionosphere, and that if aliens are looking hard enough they could find it.
You Are a Boltzmann Brain at the Heat Death of the Universe
In 1896, Austrian physicist Ludwig Boltzmann first published a theory that tried to account for why the universe wasn’t as chaotic as thermodynamics seemed to predict that it should be. Thermodynamics was a relatively new field at the time, and one of the main principles of thermodynamics is that the universe tries to maximize entropy, or disorder. The universe is over 13 billion years old, which means it’s had a long time to spiral into chaos.
Why then does everything in the universe seem so organized and why does it follow rigid, precise rules? The field of quantum physics didn’t exist yet, and the seemingly random nature of quantum particles had yet to be observed, so this was a pretty logical question to ask. In his paper, Boltzmann presented a hypothesis. The hypothesis was that even after the universe had reached maximum entropy, also known as the heat death of the universe, that it would randomly undergo fluctuations to a more ordered state, possibly creating something like the universe we see today.
Other cosmologists didn’t believe this was likely, and the Boltzmann Brain was proposed as a reductio ad absurdum argument against the theory. The idea is that smaller fluctuations are more likely than larger ones. As such, it is more likely that the random fluctuations formed a single human brain full of false memories than it is to have formed the entirety of our observable universe. It sounds like a silly idea, because it was intended to. Like Schrodinger’s Cat, it was meant to be a ridiculous argument. For a century it remained a ridiculous argument meant to disprove Boltzmann’s theory.
However, in 2002 something changed. As theories about the universe and a possible multiverse became more advanced and better understood, the math showed something startling. Statistically speaking, you are far more likely to be a Boltzmann Brain that randomly formed eons after the heat death of the universe and was filled with false memories including a belief that you exist at a point when the universe was much younger.
Obviously this was never the goal. Nobody is trying to prove that Boltzmann Brains exist, they’re trying to prove that they don’t. Many scientists are able to simply disregard the idea as being far too silly to be worth consideration. But for others, it is a serious problem. In most theories of the universe, it is less likely that the universe actually exists as we believe it does and more likely that everyone who believes they are reading this post right now is a Boltzmann Brain that randomly formed with false memories of having read this post.
Fortunately, even those that view this as a problem with current theories don’t believe it’s the reality in which we’re all living. We just hope that someday the math will agree with them.