The most reasonable estimate of the age of the universe by humans is roughly 13.8 billion years, with a margin of error of a few thousand years. But there is a good way to express this enormous length of time in a way that makes it easy to understand at a glance.
The life of the universe can be summarized in a one-year calendar, according to a method proposed by astronomer Carl Sagan in 1977.
In this calendar, the universe was born at midnight on January 1st and has now reached midnight on December 31st.
The history of the human species occupies approximately four minutes on the calendar (200,000 years in real time).
In contrast, dinosaurs roamed the Earth for 170 million years, appearing at lunchtime on Christmas Day and lasting four days before going extinct on December 29th when the remaining party food ran out.
---From "Page 20, Chapter 1: Huge, Old, and Strange"

It is not known exactly why Copernicus waited until his death to publish his hypothesis, but it may have been because the biblical geocentric model, which states that the sun, not the Earth, revolves around the universe, conflicts with the heliocentric model, if taken literally.
Even if it were merely a question, denying the Bible in 16th-century Europe was a terribly foolish act.
Contrary to popular belief today, Copernicus' ideas were not taken seriously by anyone at the time, and so it is fair to say that they remained unopposed by the Church for a long time.
Copernicus's claim that the Earth revolves around the Sun was pure nonsense, and even the great Martin Luther ridiculed Copernicus's ideas, saying:
“It’s like this these days.
Anyone who wants to seem smart has to challenge other people's opinions.
Copernicus had to do something himself.
But it would be foolish to try to overturn the entire science of astronomy.”
---From "Pages 38-39, Chapter 2: Unraveling the Mysteries of the Solar System"

In 1964, physicists Robert Wilson and Arno Penzias were experimenting with a Holmdel horn antenna installed in New Jersey.
The device was a new, six-meter-tall instrument erected to search for radio waves and microwaves emitted by stars.
Initially, the two scientists used a horn antenna to spectroscopically study the radio waves emitted by our galaxy, but as they began their experiment, they noticed a constant hissing noise in the background of the signal.
Penzias went to the antenna to see what was causing the problem and discovered that two pigeons had built a nest inside the antenna.
Inside the antenna, there were piles of pigeon droppings, which Penzias wittily described as "white stuff."
… … At this point, one of the researchers resorted to the easiest method of killing the pigeon with a shotgun to settle the matter.
However, when the two scientists returned to the signal detector, they found that the microwaves were still being detected.
Not only that, the antenna was continuously picking up microwaves from all directions in the sky.
It was clear that the entire universe was filled with microwave energy, and at this point the two men began to become confused.

---From "Pages 73-74, Chapter 3: In Search of the Beginning of the Universe"

Suppose we launch a light-speed rocket toward a distant galaxy.
The space-time surrounding us continues to expand, and galaxies move further and further away.
The fastest we can catch up with a receding galaxy is the speed of light, but spacetime is stretching faster than the speed of light, so we will never catch up.
It's like riding an escalator that goes down faster than you can go up, but you can't get to the top floor.
The point where we cannot reach even if we try to approach it is called the cosmic event horizon, and this horizon is 16 billion light-years away from us.

---From "Pages 85-86, Chapter 4: The Big Problem of the Big Bang"

The discovery by astronomer Vera Rubin in 1976 changed the game.
The galaxy isn't just spinning fast, it's spinning really, really, really fast.
It also turns out that while planets and nebulae rotate at speeds that are not significantly different from those predicted by general relativity, most galaxies rotate six to eight times faster than we thought possible.
This was not a minor calculation error, but a major problem.
After Rubin's discovery, only two of the various explanations for the galaxy's excessively rapid rotation remained.
One explanation is that Einstein's equations are wrong, and the other is that the mysterious substance that truly fills the universe is hiding somewhere beyond the reach of human detection technology.

---From "Page 101, Chapter 5: Einstein Didn't Make Mistakes!?"

On April 10, 2019, the Event Horizon Telescope, a network of eight radio telescopes located around the Earth, turned the Earth into a giant antenna and focused on the galaxy M87, 5.2 trillion kilometers away, and captured a picture of the black hole at its center.
… … This shot yielded a picture of a ring of orange and yellow that looked like a glowing donut in space.
The reason black hole photos are so exciting is that they neatly prove that black holes really exist, and that their actual shape matches the shape predicted by general relativity.

---From "Page 125, Chapter 6, The Center of Darkness, the Black Hole"

Although energy is slowly being released (black holes are incredibly cold), it is slowly leaking out, causing the black hole to lose energy and contract.
After trillions of years, even supermassive black holes will shrink to nothingness.
We know that this black hole emission, which we call "Hawking radiation" in honor of Hawking, must occur, but we don't know what causes it to occur.
This is not the first time in the history of physics.
Isaac Newton didn't know what caused the planets to orbit, but he knew something was causing them to do so, so he left that part blank so that later scientists could figure out what that something was.
Hawking radiation is quite similar.

---From "Page 144, Chapter 7: Holograms, Loops, and Strings"

Consider our galaxy, which is currently estimated to contain 200 billion stars.
The radiation emitted near the galactic center is so strong that it can destroy complex biochemicals, so the area outside the galactic center, at least a quarter of the way out, is considered uninhabitable and is excluded.
That leaves 150 billion stars.
Next, if we consider that planets are created as byproducts of the star formation process, it is estimated that most stars have planets.
However, conservatively, we can assume that only 90 percent of stars have planets, with each star having one planet.
Then there are 135 billion habitable planets.

---From "Page 177, Chapter 8, Is There Anyone There?"

In 1855, something in the Tau Sagittarius region, about 1,000 trillion kilometers from Earth, generated radio waves.
After traveling at the speed of light through the cold, vast expanse of space for over a century, the radio wave finally entered Earth's atmosphere on August 15, 1977, and was picked up by the Big Ear radio telescope in Ohio.
The radio wave lay quietly in data storage for three days before astronomer Jerry Ehmann printed a week's worth of records to decipher what the telescope had captured.
On August 18th, Eman sat at the kitchen table reading the flow of numbers written on the record, and when he realized what the record meant, he jumped up in surprise.
---From "Pages 199-200, Chapter 9, Goodbye, Insignificant Earthlings!"

We all live in the present, regardless of our upbringing or intellectual ability, and we live in constant anxiety, underestimating our own worth.
Many people sometimes question whether humanity is worth preserving, and many others, realizing the grandeur of the universe, feel insignificant in comparison.
Space science is potentially depressing because it reminds us of our insignificance in the face of the universe.
… … If you look at each and every one of us, it is true that we are all small.
But everyone wants and thirsts to know where humanity fits in.
We embark on an adventure to discover what exists in the universe and marvel at science.
Scientific research isn't just the domain of 150-IQ, genius scientists in lab coats.
Science is for all of us, a burden we all share, an obstacle we all have to bear, a question we all ask ourselves.

---From "Pages 223-224, Chapter 10: Moving Forward Boldly"