At a glance, the universe may appear random. Two trillion galaxies just sprawled across the cosmos. Amidst this cosmic chaos scientists detect war. The galaxies present in our universe link up in a huge cosmic network that spans across the entire universe. And how this pattern emerged must be cosmology’s largest mysteries.
As famous astrophysicist Hakeem Oluseyi once said “You do not understand something unless you understand how it came into existence.” Hence, we are on the hunt to understand this cosmic web. To solve this mystery scientists need to go deep into space, all the way to the edge of the observable universe. We observe and study the light from the first galaxies here.
Galaxies are the biggest building blocks of the universe. Chile 2021, scientists point the VLT or “Very Large Telescope” towards the Hubble Ultra Deep Field. The Hubble Ultra Deep Field is the patch of sky famously photographed by the Hubble Space Telescope in 1995. The VLTs power allows astronomers to see much deeper into this region of space.
Imagine you have a grain of sand on the tip of your finger, and you extend your arms out towards the sky. The patch of sky that that very grain of sand will cover, that is the size of the Hubble Ultra Deep Field and yet it contains thousands of galaxies.
The VLT stares at the patch of sky for 155 hours and picks up the faintest glows. Ancient hydrogen gas concentrated along a strand of 15 million light years. It was later discovered that the filaments are just a miniscule part of the grand and spectacular cosmic web- the largest structure known in the observable universe. The scale of the cosmic web is enormous, it is by far the largest thing we can see in the universe.
The cosmic web is a lattice of filaments, linked streams of hydrogen gas that forms an intergalactic network spanning across the entire universe. Inside this marvel you will find galaxies, stars and black holes. It is a beautiful super highway. We see the cosmic web form as far as we look. We also see galaxies that form along the web all the way back. The cosmic infrastructure dates back to the earliest moments of the universe.
13.8 billion years ago the universe ignites in a tiny ball of super-hot energy, it expands and begins to cool. Energy transforms into primitive subatomic particles of matter. The heat from the big bang is so intense that gravity is powerless. The very early universe was super-hot and super energetic, the subatomic particles were zipping around so very fast that not even the force of gravity could hold them together. But regular matter was not the only thing in the early universe.
In the midst of all this chaos, gravity is working on something else- regular matter’s ghostly cousin- the invisible substance known as dark matter. It makes up 85 percent of the matter created in the early universe. Normal matter and dark matter existed since the time of the big bang but the way in which they turned out was very different. Just ten seconds after the big bang the infant universe is billions of degrees of Fahrenheit, too hot for particles to clump together. But dark matter plays by a different rule. It is not affected by the Big Bang’s intense radiation. It is able to cool and clump together in a way that regular matter was not able to. As it clumps together it exerts a gravitational pull and begins to form shadowy structure. As dark matter gets a foot hole there is a bit more stuff, then that attracts more and more dark matter.
380,000 years after the big bang the intense heat went down to a few thousand degrees. Normal particles of matter move around more slowly, protons and electrons bind together and form atoms of hydrogen and helium gas. Then, gravity from dark matter starts to work on regular matter, and before you know it you have this clumpy universe with these huge dark matter halos which start drawing in ordinary matter. A billion-year building project begins as dark matter clumps gas clouds. The foundation for the cosmic web is laid. But the job is not finished. How did these clouds of gas transform into the greatest structure in the universe?
The secretive dark matter that brought the stuff together is managing the build. It's really dark matter that called the shots because it out weighed the ordinary stuff by a factor. Tendrils of material stretch out along the universe. As the sprawling structure builds its gravitational attraction, strengthening and pulling in more dark matter, the clumps begin to collapse and shrink down into filaments. These form even more tight structures that drag in even more hydrogen gas.
Fast forward to now and the web appears in all its star spangled glory.
Bibliography:
Hearle, Alex. “Secrets of the Cosmic Web” Discovery +. 6 Mar, 2022. Video. 18 Sept, 2022.
