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In the past, ancient civilizations like the Chinese and the Greeks marveled at the vastness of the sky, puzzling over its mysteries. Though they made significant discoveries, the real breakthroughs came with the advancement of technology in the 20th and 21st centuries. Some of these revelations might be hard to comprehend for the average person, but they are undoubtedly true.
10. Space-Time Curvature
The concept of space being either flat or curved may seem odd, and even hard to believe, but it’s a reality.
Albert Einstein discovered that the space around objects with gravity is curved, which explains phenomena like orbits (more on that in a moment). One way to figure out whether space is flat or curved is by applying Euclidean geometry, the same geometry developed by the ancient Greek mathematician Euclid, whose formulas you studied in high school geometry.
For instance, in Euclidean geometry, the sum of the angles in a triangle equals 180 degrees. Not so in curved space. The curvature of straight lines (a bit of a paradox) results in larger angles. In fact, you could even draw a triangle with three 90-degree angles.
Take a moment to think about that.
9. Gravity: Not Quite a Force
Remember back in high school physics when you studied Isaac Newton’s Three Laws of Motion and the concept of gravity? Force equals mass times acceleration, or 9.8 m/s? Forget about it. Well, almost.
Newton wasn’t entirely wrong with his laws of gravity; however, he wasn’t entirely right either. His formulas could, in theory, produce results like infinite gravity, which didn’t quite make sense, and Albert Einstein recognized that. He then developed his own equations that addressed questions about gravity that Newton’s couldn't. This led to our understanding of curved space, which is responsible for gravity.
Visualize space as a rubber sheet. Now, place a bowling ball, symbolizing Earth, on the sheet. You should see a dip in the rubber around the ball. Keeping that in mind, if you were to roll a smaller, lighter ball (the Moon) towards the edge of this curved rubber, it would get caught in the curvature (gravity) and start orbiting the Earth. This is Einstein’s explanation of gravity.
The main point here? Gravity isn’t a force, so forget what you learned in high school physics—well, just that part.
8. Einstein’s Theory of Relativity
Einstein’s theory of relativity is quite intricate, so buckle up, everyone. It connects with the concept of curved space and gravity not being a force, but it stands as a theory all on its own.
On a larger scale, as an object moves farther away from an observer, time appears to slow down from their perspective. For example, if you hold a clock in front of you, it ticks normally. But as you move that clock farther away, the seconds and minutes seem to slow down. They don’t actually slow down, but they appear to.
This effect applies to many things, such as aging and light. If you hold a blue light up close, it appears blue. But as it moves farther away, it starts to look red because red has a longer wavelength. This is also why sounds change pitch as they move. When a train horn approaches, the wavelengths shrink, raising the frequency and pitch. As it moves away, the wavelengths stretch, causing the frequency and pitch to drop.
On Earth, these relative differences are so small they’re almost undetectable, which is why Newton’s laws are still useful and taught in school. They work perfectly well here, with one exception: Global Positioning Systems.
GPS systems depend on Einstein’s theory of relativity to operate correctly. Time passes more slowly on satellites orbiting Earth, from our viewpoint, than it does on the ground. Conversely, time runs faster for the satellites due to Earth's gravity. These time discrepancies are significant enough that they would drastically distort your travel time. To ensure accurate navigation, GPS devices rely on Einstein’s time.
7. Black Holes
Black holes remain one of the greatest mysteries of the universe. Their very nature is what makes them so elusive. For starters, they are invisible. Their gravity is so intense that nothing, not even light, can escape. To break free from their gravitational pull, matter would need to travel faster than the speed of light, which is impossible. This is why black holes are called what they are: no light escapes, so they appear black. Straightforward, right? Well, it’s not that simple.
A black hole is essentially the remains of a star. When a massive star (much larger than our Sun) dies, it explodes in a supernova and then collapses into a neutron star or a black hole. The latter is very different from a star. Black holes possess a gravity so strong that it causes a singularity, a point where density becomes infinite, where all the mass is compressed, and where time completely halts. The event horizon is the boundary around the black hole, the 'point of no return,' beyond which the escape velocity exceeds the speed of light and both space and time are locked into one direction: forward.
Once you cross the event horizon, there’s no turning back. If you reach the singularity, you’ll meet a quick, but brutal, demise. The tidal forces are so overwhelming that your body will be stretched unnaturally, getting crushed from every direction. You’ll end up looking like a string, which is another reason why we know so little about black holes—studying them is far too dangerous.
6. Alternate Realities
At first, this may seem like pure science fiction, but in reality, it's a legitimate concept that scientists have been wrestling with for over a century.
During World War I, Karl Schwarzschild formulated the first equation about black holes, including their size and, more intriguingly, what lies within them. He proposed that at a singular moment, the singularity (the point where you're crushed) connects to an infinite number of parallel universes—each entirely independent but still within our universe.
What’s even more mind-boggling is the work of Roy Kerr, who developed equations for a rotating black hole. This changes everything—quite literally. His equations transform the singularity from a dot into a ring, which acts almost like a portal leading to infinite universes. If you were to pass through this singularity (without touching the ring, as it would be fatal), you would enter a completely different space, and once there, you couldn't return through the same singularity. The space you'd enter would be inside a white hole, which, as the name implies, is the opposite of a black hole—nothing can enter it, only be expelled. Theoretically, you could exit that white hole and find yourself in a universe identical to ours, but not actually ours. You could repeat this journey—enter another black hole, come out through a white hole into yet another universe—endlessly.
Naturally, all of this is purely theoretical and exists only in mathematical equations, not in observable reality. While it's likely not true, considering factors like mass addition, it's a concept that scientists are forced to seriously consider and investigate today.
5. White Holes
A white hole is the complete antithesis of a black hole: nothing can enter it. It shares a similar structure with a Kerr black hole, with a ring-shaped singularity that acts as a portal to other universes. It also has an event horizon, preventing anything from re-entering once it's crossed, as the forces of space and time are too powerful.
White holes do not exist in our universe. They are purely theoretical constructs that arise from the mathematical models of black holes. Even if such hypothetical white holes existed in imaginary universes within hyperspace, we would not be able to reach them due to the inherent nature of black holes.
4. Wormholes
Wormholes, like black and white holes, are outcomes of the equations describing these cosmic phenomena, though they don’t directly involve alternate universes or hyperspace. Instead, they pertain to the structure of our own universe.
According to the theories, wormholes could serve as shortcuts through space-time. To picture this idea, imagine a large concrete block in front of you. To reach the other side, you would typically have to go around it. However, the quickest route would be to walk directly up to it, brushing your shoulder against it as you pass by. To make it even shorter, imagine you could cut a hole in the concrete and pass through it instead. Same destination, same universe, just a very different—and much harder—way to get there.
Admittedly, this analogy oversimplifies things, but it conveys the general idea. Wormholes could, in theory, bypass the conventional space-time, providing a shortcut from one region of the universe to another without needing to travel through the universe's regular space-time.
Wormholes begin at a black hole and emerge from a white hole somewhere else in the universe. However, as with much of this topic, it remains purely theoretical. The fact that it's under serious investigation is already a truly astounding concept.
3. Gravitational Lensing
This one might not be as mind-boggling as the others, but it still makes you pause and think. And unlike the other concepts on this list, it has been conclusively proven, though that doesn't make it any less wild.
Gravitational lensing occurs when an object appears to be located in a certain part of space, yet it isn't actually there. This happens because the light from its true position bends around another massive object’s gravity, refracting the light in the process.
Gravity bends light. Let that sink in.
2. Whatever It Is The Universe Is Expanding Into
A profound cosmological question remains: What lies beyond the boundaries of our universe?
It’s widely understood that the universe is infinite, lacking both an edge and a center, yet it continues to expand. The space between galaxies is growing, a phenomenon evident in the redshift observed in nearby galaxies. Redshift occurs when an object moves away from us, stretching the wavelengths of its light, thus causing the light to shift toward the red end of the spectrum.
The universe is expanding, but what is it expanding into? What could exist on the other side? This idea is mind-boggling and almost impossible to wrap our heads around, yet it’s the reality we live in.
1. Dark Matter
One of the more perplexing and mind-boggling mysteries of the universe is the vast amount of stuff that exists, yet remains unseen. We don't know what it is, but it's everywhere.
That’s essentially all we can say about dark matter, the mysterious substance that accounts for 27 percent of the universe. On top of that, dark energy—an entirely different, yet equally enigmatic force—makes up 68 percent. Meanwhile, ordinary matter, such as the protons and neutrons that make up your body, constitutes a mere 5 percent.
Vera Rubin's discovery of dark matter came when she noticed that the total mass of galaxies exceeded what could be accounted for by the visible objects in them. This indicated that there must be something unseen within these galaxies that possesses mass.
How is that possible? What exactly is this unseen substance? These are the same perplexing questions that baffle astronomers, and they continue to challenge our understanding of the universe.
