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Our connection with gravity goes all the way back to our elementary school days, when we first encountered this fascinating force. Yet, gravity is far more than the simple force that keeps us grounded on Earth.
While school provides us with fundamental concepts about gravity, these basics often lead to numerous misunderstandings and leave gaps in our true comprehension of this vital physical force. Here are 10 mind-blowing theories and facts you likely never heard about gravity.
10. Gravity Is A Theory, Not A Law
The idea that gravity is a scientific 'law' is a common misconception. If you were to search online about gravity, you’d likely come across many articles referring to the 'law of gravity.' In the scientific community, however, laws and theories are distinct concepts. A scientific law represents a consistent fact based on data and observations, which clearly describe what is happening. Meanwhile, a theory is a conceptual framework that explains why certain phenomena occur.
When we examine gravity through the lens of scientific laws and theories, it’s clear why gravity is considered a theory rather than a law. Scientists haven’t yet been able to measure gravity across every star, moon, planet, asteroid, or atom throughout the universe.
Voyager 1, a human-made space probe, has traveled about 21 billion kilometers (13 billion miles) from Earth. It has technically left our solar system, though not by much. Looking at the decades-long journey of Voyager 1, it becomes evident why scientists have not been able to study the gravity of every star, moon, planet, asteroid, or atom. The vastness of the universe is overwhelming!
9. Gaps in the Theory of Gravity
Once we come to terms with the fact that gravity is just a theory, we’re hit with another surprise. There are several gaps in the theory of gravity that suggest it may not be as solid as we once believed. Many of these gaps are evident within our solar system, and some can even be observed right here on Earth.
For instance, the theory of gravity suggests that the Sun’s gravitational pull would be much stronger on the Moon than Earth’s gravitational pull. As a result, the Moon should orbit the Sun, not the Earth. However, we know from observation that the Moon orbits the Earth, which is evident when we look at the night sky.
In school, we also learned about Isaac Newton, the scientist credited with 'discovering' gravity, who acknowledged a potential flaw in the theory. Newton developed a new branch of mathematics called fluxions, which he used to create the theory of gravity. While fluxions may not be familiar, its evolution led to something we all recognize.
Today, we refer to it as calculus. Although many of us encounter calculus in our studies, this branch of mathematics has its own set of flaws. Consequently, there may be weaknesses in the way Newton 'proved' his theory of gravity.
8. Gravitational Waves
In 1915, Albert Einstein proposed his general theory of relativity (often known as Einstein’s theory of gravity). Around the same period, the concept of gravitational waves was introduced. It wasn’t until 1974 that this idea was proven to be true.
Gravitational waves are disturbances in the fabric of space-time, triggered by powerful events in the universe. These events can range from the collision of black holes to the erratic rotation of neutron stars or even a supernova. When these events occur, gravitational waves spread outward, much like ripples in a pond after a rock is thrown in. These waves travel at the speed of light across the universe.
Since these catastrophic events don’t occur frequently, it takes a long time to observe gravitational waves. This is why it took nearly 60 years to confirm their existence.
For more than four decades, scientists have been tracking the first detection of gravitational waves, the discovery that confirmed their existence. These waves were caused by two dense, massive stars orbiting one another due to gravitational attraction. Over time, it became evident that the stars were drawing closer at the rate predicted by Einstein’s theory. Thus, the presence of gravitational waves was definitively proven.
7. Black Holes and Gravity
Black holes remain one of the most profound mysteries in the universe. They form when a star collapses under its own gravity, leading to a supernova explosion. This explosion ejects portions of the star into space, creating a region where gravity is so intense that not even light can escape—the black hole. While gravity doesn’t directly create black holes, it plays a crucial role in helping us understand and study them.
The gravitational pull of black holes is key to detecting them in the universe. Their immense gravity affects nearby stars and gases, which can be observed by scientists. In some cases, black holes even pull gases into a glowing disc surrounding them. Without the powerful gravity of black holes, we might never have discovered their existence.
6. The Theory of Dark Matter and Dark Energy
Approximately 68 percent of the universe is composed of dark energy, while about 27 percent consists of dark matter. Despite their overwhelming presence, our understanding of both dark matter and dark energy remains limited.
What we do know is that dark energy possesses unique properties. Einstein’s theory of gravity played a significant role in helping scientists realize that dark energy has the ability to drive the expansion of the universe. Initially, based on Einstein’s theory, scientists believed that gravity would eventually slow the expansion over time.
In 1998, the Hubble Space Telescope revealed that the universe was expanding at an accelerating rate. This discovery led scientists to realize that the theory of gravity could not fully explain the universe’s behavior. To account for this unexplained acceleration, they proposed the existence of dark matter and dark energy as potential explanations for the expanding universe.
5. Gravitons
In school, we often learn that gravity is a force. However, gravity may be more than just a force—it could actually be a particle known as a graviton.
Gravitons are thought to be the fundamental particles responsible for transmitting gravitational force. While physicists have yet to detect gravitons, they have numerous theories suggesting their existence. One such theory posits that gravity is the only fundamental force of nature that has not yet had its basic particle detected.
While gravitons might exist, pinpointing them would be extremely difficult. One theory proposes that gravitational waves are made up of gravitons. To detect these waves, we could try a simple experiment where we bounce light off mirrors to observe any changes in their separation.
However, this method wouldn’t work for detecting the tiny distance changes caused by gravitons. In order to observe such subtle shifts, physicists would need to use mirrors so massive that they would collapse and form black holes instead.
Clearly, this isn’t a practical solution in the near future. For now, physicists are focusing on the vast universe itself, the largest system they can observe, to help detect the effects of gravitons.
4. Potential Creation of Wormholes
Wormholes remain one of the greatest mysteries in the universe. Imagine traveling through a space tunnel at the speed of light to another galaxy—sounds amazing, right? If wormholes exist somewhere out there, this could be possible. Though there's no proof of their existence yet, physicists believe gravity could play a role in creating them.
Using Einstein’s general theory of relativity, physicist Ludwig Flamm explained how gravity could bend space-time, potentially allowing wormholes to form. Of course, there are other theories about how wormholes could be created as well.
3. Time Travel
Time travel has been a fascinating mystery for ages. Various theories, including the theory of gravity, might explain why time travel could actually be possible. Gravity causes space-time to curve, influencing objects to follow a curved path. This bending causes objects in space to move slightly faster than those on Earth, with clocks on satellites gaining 38 microseconds every day.
Since gravity in space makes objects move faster than on Earth, astronauts become time travelers when they return home. The effect on them is so minuscule that it's imperceptible. But it raises an intriguing question: Could gravity someday lead to the kind of time travel seen in the movies?
2. Microgravity
Many of us have seen images or heard tales of astronauts floating weightlessly in space, which often leads us to believe there is no gravity out there. However, despite what movies often show, gravity still exists in space.
This phenomenon is referred to as microgravity, as it represents a tiny amount of gravitational pull. It gives the illusion of astronauts being weightless, but without gravity, neither the planets would orbit the Sun nor would the Moon circle the Earth.
Gravity weakens as distance increases. In space, microgravity occurs because the distances between objects are much greater than on Earth, where gravity is far stronger.
Gravity also diminishes on an incredibly small scale. Take atoms, for example. They are so tiny that their gravitational pull is incredibly weak. As atoms come together, their combined gravitational force becomes stronger.
1. Planets Apply Gravitational Force On The Sun
We understand that the Sun exerts a gravitational pull on all the planets in our solar system, causing them to orbit around it. Similarly, the Earth pulls on the Moon, which is why the Moon orbits the Earth.
However, each planet, along with any other mass-bearing object in our solar system, also applies a gravitational force on the Sun, other planets, and any mass-containing object. The strength of this force depends on both the mass of the objects and the space between them.
This is why, in our solar system, every mass-bearing object revolves around the Sun. The Sun holds the greatest gravitational influence. In fact, any object with mass in the universe exerts a gravitational pull on all other objects with mass, even across vast distances of light-years!
