The gold standard in space science is a "theory of everything" that accurately explains everything we see (and everything we can't) in the universe. Understandably, this is no small task: Using available data and their own experience, scientists are constantly creating new theories of the universe, most of which turn out to be wrong.

This is the nature of scientific inquiry. As more information comes to light, most theories don't hold up — but a few change the way we look at the unknown. Consider the "four elements" theory of ancient Greece, which informed scientific inquiry for centuries but was ultimately found to be inadequate. Einstein's quantum theory of light, meanwhile, represented a fundamental shift in our understanding of the universe.

Ready for a theoretical ride? Here are five odd theories that could change everything. Maybe.

1. Insane in the Membrane?

We typically take for granted that our universe has three physical, perpendicular dimensions. The Braneworld theory adds a fourth spatial dimension to the cosmos that sees our three-dimensional universe as a "membrane" floating through the four-dimensional "bulk" of a larger four-dimensional space that we can't actively perceive.

Work by theoretical physicists Lisa Randall and Raman Sundrum introduces the concept of multiple branes within the larger bulk, each of which represents its own universe. They suggest that these other brane-based universes could help solve the problem of subatomic asymmetry in our own cosmos, while other brane theories postulate that branes could eventually collide in what's known as the "big splat" to create new universes with unique physical properties.

Cool name aside, is there any solid evidence for braneworld? Not yet. While the theory could help explain some particle problems, that's not enough in isolation. Any theory can suggest a solution, but testability is key to determine if it actually works. Randall and Sundrum do suggest that black holes could provide a practical platform for testing. Precise measurements of gravitational waves could help determine if we're actually living in a connected, multi-universe membrane.

2. Newton 2.0

Gravity poses a problem. While Newton's theory explains the behavior of objects at relatively small cosmic scales — such as why we don't fall off the Earth and our planet stays rotating around the sun — going bigger gets problematic. Here's why: When scientists measured the amount of matter present in large galaxies and compared it with observed effects, the data didn't match up. Put simply, there wasn't enough matter present to keep these galaxies from flying apart using standard Newtonian mechanics.

Dark matter was the proposed resolution: invisible, undetectable particles that helped bulk up the universe to a point where Newtonian gravity worked as intended. The problem is we still don't have any evidence for dark matter particles.

Israeli scientist Mordehai Milgrom took a different approach. In 1983, he proposed Modified Newtonian Dynamics (MOND), which suggests that gravity at lower accelerations is stronger than Newton's model implies and that the internal motions of objects are determined not only by the object itself but also by the "external field effect," or the gravitational pull from all other masses in the universe. It's a bold claim, but as Sci-News.com notes, recent work detected evidence of this external field in 153 disc galaxies, suggesting that MOND might be the new way forward.

Tom ZÅ‚osnik and Constantinos Skordis of the European Institute for Cosmology and Fundamental Physics have further developed this idea in the form of RelMOND — a theory that adds an omnipresent field to general relativity that behaves differently depending on spatial conditions. For example, where the universe is stretching as it expands, this field acts like what ZÅ‚osnik calls "dark dust," a stand-in for dark matter that provides critical gravitational heft without the need for invisible particles.

While resistance to this theory remains relatively substantial, the lack of recent progress in dark matter detection combined with mounting evidence of potential external fields may suggest a second life for Newton 2.0.

3. A Dream Within a Dream

What if we're all just part of a massive simulation? That's the basis of Nick Bostrom's 2003 theory that suggests everything we see is simply part of a programmed simulation, and we're all playing the parts of seemingly self-aware code.

At first glance, this theory seems more than a little out there — how could we possibly know that we're simply simulations? However, some anecdotal evidence does point in this direction. First is the fact that, as technology evolves, we're inching ever closer to creating our own simulated universes that could contain programs that (from their perspective) are self-aware. If we can do it, it stands to reason that beings in another universe "above" ours could do the same thing, and we're simply living in their simulation.

Other possible indicators of virtual environments are the existence of hard-and-fast limits, such as the speed of light, which could suggest arbitrarily preprogrammed limits that either protect the simulated universe from collapsing or make it impossible for us to discover the truth.

When it comes to potentially provable theories of the universe, this particular approach ranks near the bottom. Interesting speculation aside, we can't really test this theory. Are there universal limits? Seemingly. Can we (almost) create our own virtual environments? Absolutely. However, these things alone don't constitute proof that we're living in a simulation — they simply make it possible. Lacking testable, trackable data makes this a great thought experiment but probably won't change cosmology as we know it.

4. Light, but Make It Faster!

Speaking of light and its absolute speed, there's a theory that suggests this universal constant wasn't always so constant. While current observations indicate that the fixed speed of light is 186,000 miles per second — and much of modern physics relies on this specific speed — current measurements of cosmic microwave background (CMB) radiation pose a problem: Given its uniformity over space and distance, light must have reached every corner of the early universe. But given the current size of the universe and the speed of light, we should observe cooler and denser regions rather than a consistent CMB.

To explain this seeming contradiction, the inflation theory was developed. In the distant past, the universe was much smaller, allowing light to achieve even distribution before expansion took place. But this small universe required unique conditions that can't be replicated or tested. Meanwhile, Joé£o Magueijo and Niayesh Afshordi proposed an alternative: In a much younger, hotter universe, the speed of light was much faster, allowing it to reach greater distances more quickly.

"In our theory, if you go back to the early universe, there's a temperature when everything becomes faster," says Afshordi. "The speed of light goes to infinity and propagates much faster than gravity. It's a phase transition in the same way that water turns into steam."

This theory comes with a fixed value called the spectral index, which is a measure of the initial density ripples in the universe and can be evaluated against future measurements. Magueijo and Afshordi's work puts this value at 0.96478, while current measurements of the CMB show 0.968 — remarkably close to the theory's suggested output. Bottom line? It's entirely possible that light wasn't always so slow.

5. It's Back: Luminiferous Aether Strikes Again

Last but not least on our list of odd universal theories is the potential return of luminiferous aether. Though it's now one of the most famous failed ideas in scientific history, this theory was once widely accepted and held that light traveled through an invisible medium known as aether.

In 1887, Albert Michelson and Edward Morley built a device known as the interferometer to help prove the existence of aether. But the experiment didn't go as planned. When the device split a beam of light in two, Michelson and Morley expected to see the divided beams hit their respective targets at different times as they took different paths through the aether. Since one was moving in tandem with the Earth's rotation and the other was directed at a right angle, the aether should have caused a delay for the right-angle beam. Instead, Michelson and Morley found that, no matter how many times they did the experiment, they got the same result: The beams arrived simultaneously. This was the beginning of the end for aether — and Einstein's 1905 work on special relativity finished the job.

Now, aether is back. As New Scientist notes, several groups of researchers have noticed similarities between aether and the impacts of both dark matter and dark energy. Looking at the RelMOND theory above, the external and effusive gravity field also looks a lot like aether. Although there's no conclusive evidence here to support an aether renaissance, it's an idea worth looking into. Even better is that it offers massive poetic potential for a comeback that few would have predicted.

Thinking Outside the Box

While there's some evidence to support most of these theories of the unknown, they could go either way. Maybe we really are just one of many "branes" floating around an extra-dimensional universe, or maybe our "brains" are simply parts of a massive computer program being run outside our current reality. But right or wrong isn't really what matters here. Instead, it's about the combination of existing data with the human compulsion to make logical leaps of faith.

From Newton to Einstein, the theories we now accept as fundamental (but not immutable) aspects of reality were considered well outside the box when first proposed, and they required continual testing and refinement to gain scientific confidence. At the end of the day, the universe is just full of surprises and doesn't always play by the rules, so we may as well swing for the theoretical fences and see what sticks.

Are you interested in science and innovation? We are, too. Check out Northrop Grumman career opportunities to see how you can participate in this fascinating time of discovery.