The collision of black holes is one of the most shocking things that will happen in the universe. The collision of two black holes leads to the release of a huge amount of energy that is hard to compare. Black holes are technically the most profound holes in the universe, where the gravitational force is too forceful that even the light can escape. However, when two black holes collide they produce the waves of energy that shake the entire space-time. The event is not only an exciting astronomy event, but it has given us an occasion to learn the basic laws of nature.

Why merging black holes isn’t so simple

At first glance, it might seem like two black holes are destined to merge, as their nature is to engulf everything around them. But the reality is much more complex. Black holes are “black” because anything that enters their event horizon—not even light—can return. The question then arises: how does energy escape when they collide?

The secret lies just beyond the boundary where the objects are about to cross the event horizon. Before the collision, the two black holes orbit each other, releasing their orbital energy in the form of gravitational waves. These waves are generated outside the event horizon, so they can freely propagate through the universe. This process causes their orbits to shrink, and they gradually move closer to each other.

Black holes born from binary star systems

Often Stellar-mass black holes are born from binary star systems, where two massive stars orbit each other. Over time, these stars end in supernova explosions, and their cores collapse to form black holes that can have masses many times that of the Sun. Such pairs are extremely rare, and even rarer are systems where the two black holes are close enough to eventually collide.

If two black holes are born very far apart, their union could take longer than the current age of the universe. But if the gravity of a passing star nudges them slightly, they can come closer, and then gravitational waves begin to play out.

Gravitational Waves and Albert Einstein Principle

According to Einstein’s theory of general relativity, when a massive object moves at high speed, it creates ripples in the fabric of space-time called gravitational waves. Everyday activities also create such waves, but they are so weak that they are impossible to detect.

In contrast, black holes are extremely massive, and when two black holes orbit each other at speeds equal to a large fraction of the speed of light, they produce powerful gravitational waves. As energy is released, their orbits shrink. This further increases their speed, which in turn creates more waves—a positive feedback loop. In the final moments, they merge, spinning at nearly the speed of light, leaving behind a larger, more massive black hole.

Explosion of Energy: The Power of E = mc²

When two black holes merge, the mass of the resulting black hole is not equal to their total mass. About 5 percent of the mass is converted to energy. This transformation is governed by Einstein’s famous equation, E = mc². If we calculate the collision of two relatively small black holes, the energy released in less than a second could be as much asThe Sun will emit more energy in trillions of years. At that moment, they can release more energy than the combined light of billions of galaxies.

Supermassive Black Holes and Galactic Collisions

Some black holes are so massive that their mass can exceed that of the Sun by millions or even billions. These supermassive black holes are found at the centers of large galaxies, including our own. Sagittarius A*, located at the center of our galaxy, is relatively light, yet it weighs millions of solar masses.

When galaxies collide, their central black holes eventually begin orbiting each other. Their final merger can be so powerful that the energy released in a single second can exceed the combined energy of all the stars in the visible universe by thousands of times. It’s a truly cosmic-shaking moment.

Invisible but real: Gravitational waves challenge

Despite being such powerful events, they remain hidden from our eyes because gravitational waves themselves are invisible and often not accompanied by any light. These waves weaken with distance, and supermassive collisions typically occur billions of light-years away. By the time they reach Earth, they are fainter than a whisper.

Future missions like the Laser Interferometer Space Antenna may provide us with more clear evidence of these mysterious phenomena. The data it generates in the coming years could prove just how common these mind-boggling events truly are.

Silent Echoes of the Universe

Every moment you’re reading this article, gravitational waves generated by black hole collisions somewhere are passing through your body. They come from so far away that their power is almost exhausted—and that’s a good thing for us. Still, it’s chilling to think that such unimaginably energetic events are constantly occurring in the universe. These silent echoes of black holes remind us that we are part of a universe that is as beautiful as it is mysterious and awe-inspiring.

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