Get ready to be introduced to an elusive character that lurks in the cosmos, amongst our well known matter. It challenges the very foundation of our knowledge of the cosmos. The best-kept secret in the cosmos, meet dark matter. Dark matter, which makes up an astounding 27% of the universe's total mass and energy, is both mysterious and pervasive. It's the cosmic conundrum that has physicists scratching their brains while the rest of us struggle to keep up with their head-spinning theories. This ghost-like matter, which can’t be seen by our telescopes and can be only detected when there are any errors in scientific calculations, is one of the many mysteries scientists are eager to solve till this day.
Dark Matter: The Cosmic Intruder
To understand what dark matter is, we must first understand what it is not. Unlike the matter we are familiar with, dark matter is entirely aloof to electromagnetic radiation; it neither emits nor interacts with light. It is the universe's elusive spectator. While the rest of the universe is busy emitting, reflecting, and interacting with light, dark matter hangs back in the shadows, smirking at the laws of physics like an interstellar trickster.
Well, if dark matter doesn’t interact with matter, how do we know of its existence? Let's go through some modern day proofs.
Proof #1: Galactic Speedsters
Imagine you're at Space 1 (a cosmic ripoff of Formula 1, where galaxies whiz by like Formula 1 cars). According to the laws of gravity, these galaxies should be slowing down as they venture farther from the galactic center. But here's the deal – they're not! Galaxies are spinning around at speeds that defy the gravitational pull of visible matter alone. This is where dark matter comes into the rescue, to provide the extra gravitational muscle (mass) needed to keep those galaxies from careening off into the cosmic void. When astronomers crunch the numbers and observe the way galaxies move, they realize there's more mass at play than meets the eye. And hence the name, dark matter.
Proof #2: Cosmic Lensing
Now, picture a cosmic magnifying glass, one big enough to distort the very fabric of space-time itself. That's gravitational lensing for you, a cosmic magic trick that lets massive objects like galaxy clusters bend and warp the light from objects behind them. This celestial sleight of hand provides some of the most convincing evidence for dark matter's existence. The way light bends around these invisible objects suggests there's a lot more mass in those galaxy clusters than can be observed.
Proof #3: Cosmic Microwave Background (CMB)
Now, let's turn our attention to the afterglow of the Big Bang, the cosmic microwave background (CMB). It's like the universe's baby picture, capturing the universe's early moments in stunning detail. But there's a twist – the CMB reveals an exquisite pattern of temperature fluctuations that align with predictions assuming the presence of both dark matter and regular matter.
Proof #4: Cosmic Structural Formation
In the cosmic infancy, dark matter acted as the scaffolding upon which galaxies and galaxy clusters constructed themselves. Without dark matter's gravitational pull, the magnificent cosmic structures we now behold would resemble a chaotic Jenga collapse.
Proof #5: Bullet Clusters Imagine two galaxy clusters hurtling towards each other at tremendous speeds. The regular matter in these clusters collides and generates a cosmic traffic jam. However, dark matter is unaffected, as if immune to the chaos. The separation between visible matter and dark matter in the Bullet Cluster provides compelling evidence of its existence.
Conclusion: Without dark matter, you and I wouldn't have formed
To comprehend the size, shape, and future of the universe, one must have a solid grasp of dark matter. Whether the universe is open (continues to expand), closed (expands to a point and then collapses), or flat (expands and then stops when it achieves equilibrium) depends on the amount of dark matter in the cosmos. The origin and evolution of galaxies and clusters can be firmly explained with the understanding of dark matter. A galaxy should be split apart as it spins. Something is preventing this, thus the galaxy is held together. The ‘something’ is gravity, but the quantity of gravity needed for this is tremendous and cannot be produced by the matter that is visible in the galaxy.
All thanks to dark matter for causing the formation of nebulas, protostars and eventually the formation of earth, me and you.
References
[1] CERN-Dark Matter- Article [https://home.cern/science/physics/dark-matter]
[3] European Space agency-Dark Matter-Article [https://www.esa.int/Science_Exploration/Space_Science/What_are_dark_matter_and_dark_energy]
[4] A.D. Ernest, Dark Matter and Galactic halos -a quantum approach [https://arxiv.org/ftp/astro-ph/papers/0108/0108319.pdf]