Chapter 1: Entering the Digital Cosmos

In a remarkable twist of fate, we now have access to a digital version of the universe that transcends traditional gaming experiences. If your computer is equipped with sufficient storage, you can explore this vast cosmos at no cost.

"I never thought I would write 'You too can explore a digital simulation of the universe on your PC' back in 2021, yet here we are," reflects an astonished writer. (Image: Tomoaki Ishiyama, Hirotaka Nakayama, 4D2U Project, NAOJ)

In an era dominated by mainstream digital entertainment, it's easy to overlook the difference between the figurative "Marvel Cinematic Universe" or the "Metaverse" and the actual universe. A recent scientific initiative has introduced a virtual representation of the real universe, aptly named Uchuu, which means "outer space" in Japanese. This is the most extensive and realistic virtual universe ever constructed. If you're tech-savvy and have ample storage on your personal computer, you can interact with it from the comfort of your home.

Uchuu is essentially a computational cube, stretching an astonishing 9.63 billion light-years on each side. That’s right, billion light-years. Within this immense cube, the simulation comprises the existence and interaction of over 2.1 trillion particles, which create galaxies and galaxy clusters. This enables scientists to examine the structure of the universe on a previously unimaginable scale.

While these images may not rival the dazzling visuals of space-themed video games, they are the closest digital representation we have of the actual universe. (Images: Tomoaki Ishiyama, Hirotaka Nakayama, 4D2U Project, NAOJ)

Moreover, Uchuu simulates the evolution of matter throughout nearly the entire 13.8 billion-year timeline of the universe, from the Big Bang to the present. Julia F. Ereza, a Ph.D. student at Spain’s Instituto Astrofísica Andalucía, remarks, "Uchuu functions like a time machine. We can travel forward or backward in time, zoom in on a specific galaxy, or zoom out to observe entire clusters. It provides a real-time glimpse of the universe's dynamics, from its early days to the present, making it an essential tool for cosmic study."

The simulation was crafted using the ATERUI II supercomputer, which is dedicated to astronomical projects in Iwate, Japan. Despite its immense power, the calculations required for Uchuu took considerable time. "We utilized all 40,200 CPU cores available on ATERUI II exclusively for 48 hours each month," explains Tomoaki Ishiyama, an associate professor at Chiba University who developed the code for Uchuu. "In total, we consumed 20 million supercomputer hours and generated 3 petabytes of data—equivalent to nearly 895 million images from a 12-megapixel camera."

Observing these dynamic images of galaxies is as captivating as one might hope—and intriguingly, they resemble neurons in some respects. (Image: Tomoaki Ishiyama, Hirotaka Nakayama, 4D2U Project, NAOJ)

As of 2021, anyone can download the essential simulation files for Uchuu and run this virtual universe on their own computer. The primary requirement? A staggering amount of storage—over 100 TB of compressed data, which translates to eight of the largest hard drives currently available. The silver lining is that since ATERUI II handled the heavy lifting, interested users can experiment with various scripts and datasets for fun, merging scientific inquiry with personal exploration. Scientists aim to use Uchuu to enhance their understanding of Big Data derived from the universe, but for now, take a moment to appreciate this remarkable simulation available to everyone!