Chapter 1: Time Travel Through Telescopes

The most advanced telescopes function like time machines, allowing us to observe the universe as it was in the past. However, the challenge lies in the fact that light has not always been present for us to see.

Thousands of galaxies, each hosting billions of stars, were captured in a stunning 2022 image taken by the James Webb Space Telescope (JWST).

The James Webb Space Telescope, commonly referred to as JWST, is one of the most sophisticated telescopes ever constructed. The planning phase for JWST began over 25 years ago, with a decade dedicated to its construction. It was launched on December 25, 2021, and reached its designated orbit approximately 930,000 miles from Earth within a month. This unique position allows it to observe the universe with minimal obstruction.

The design of this telescope was a global collaboration spearheaded by NASA, aimed at expanding the horizons of astronomical observation through groundbreaking engineering. Its mirror spans about 21 feet (6.5 meters) in diameter, nearly three times larger than that of the Hubble Space Telescope, which has been operational since 1990.

The mirror is essential for collecting light, and JWST's large mirror enables it to detect the faintest and most distant stars and galaxies. Its cutting-edge instruments provide insights into the composition, temperature, and movement of these faraway cosmic entities.

As an astrophysicist, I constantly look back in time to understand what stars, galaxies, and supermassive black holes looked like when their light began its journey to Earth. This knowledge aids in comprehending their growth and development. For many space scientists, the James Webb Space Telescope acts as a portal to the enigmatic universe.

How far can JWST look back into the cosmos? Approximately 13.5 billion years.

Section 1.1: The Nature of Light Travel

Astronomers do not see stars, galaxies, and exoplanets as they exist today. Instead, they observe how these objects appeared in the past due to the time it takes for light to travel through space. Essentially, gazing into space is akin to journeying back in time.

This concept applies even to nearby objects. For instance, the light we perceive from the Sun left its surface roughly 8 minutes and 20 seconds ago — the duration it takes for sunlight to reach Earth.

Light, regardless of its source—be it sunlight, a flashlight, or a light bulb—travels at a speed of 186,000 miles (around 300,000 kilometers) per second, translating to over 11 million miles (approximately 18 million kilometers) every minute. With the Sun situated about 93 million miles (150 million kilometers) from Earth, this results in an 8-minute, 20-second delay.

The farther an object is, the longer its light takes to arrive. For example, light from Proxima Centauri, the closest star after our Sun, is four years old, as it is situated around 25 trillion miles (approximately 40 trillion kilometers) away.

Recently, JWST detected Earendel, one of the most distant stars observed, with light approximately 12.9 billion years old.

JWST can peer deeper into the past than any previous telescope, such as Hubble, which can detect objects 60,000 times fainter than the human eye. In contrast, JWST can observe objects nearly nine times fainter than what Hubble can achieve.

Section 1.2: The Big Bang and Cosmic Evolution

But is it feasible to observe the universe's inception?

The Big Bang is the term that describes the origin of our universe, believed to have occurred approximately 13.8 billion years ago. This theory is widely accepted among physicists as the explanation for the universe's history.

The term can be misleading, as it evokes the image of an explosive event like fireworks. In reality, the Big Bang signifies the rapid expansion of space throughout the universe. The conditions right after this event resembled a cosmic fog that hindered the travel of light. Over time, galaxies, stars, and planets began to emerge.

This period is often referred to as the "cosmic dark ages." As the universe expanded, this fog dissipated, allowing light to traverse freely through space. Several satellites have detected the light remnants from the Big Bang, which occurred about 380,000 years post-event. These telescopes focus on the patchy glow left by the Big Bang, observable in the microwave spectrum.

However, even 380,000 years after the Big Bang, stars and galaxies were nonexistent, and the universe remained in darkness. The cosmic dark ages did not conclude until hundreds of millions of years later, when the first stars and galaxies formed.

While the James Webb Space Telescope was not specifically designed to observe the Big Bang itself, it aims to investigate the era when the universe's first luminous objects began to take shape. Before this epoch, the early universe lacked sufficient light for JWST to capture, given the sparse presence of stars and galaxies.

Looking back to the time close to the Big Bang involves more than just having a larger mirror; astronomers have achieved this using other satellites that detect microwave emissions shortly after the Big Bang. Therefore, JWST focusing on the universe a few hundred million years after the Big Bang is not a limitation but rather the telescope's intended purpose. This focus reflects where astronomers believe the first light from stars and galaxies will emerge.

By examining ancient galaxies, scientists aspire to comprehend the unique conditions of the early universe and gain insights into the processes that enabled their formation. This includes studying the evolution of supermassive black holes, the life cycle of stars, and the composition of exoplanets—worlds beyond our solar system.

The first video, "What Did James Webb Really See At The Beginning Of Time?", delves into the groundbreaking discoveries made by the James Webb Space Telescope, shedding light on the early universe.

The second video, "We'll Soon See Back to the Beginning of Time. James Webb Space Telescope's Big Reveal is Hours Away," discusses the anticipation surrounding the upcoming revelations of JWST's findings.