Humankind and the Universe
Humankind has been observing the universe since the ancient past. In 3000 B.C., many civilizations such as the Sumerians, who carved stars on clay plates, observed and recorded the movements of the sun, moon, and stars in the sky. Egyptians observed the sky and predicted the flooding period of the Nile River, and the ancient Greek philosophers such as Thales, Aristotle, and Ptolemy observed the sky and mathematically organized the movements of stars, systematizing the field of astronomy.
The desire to seek the origin of the universe led to the development of a technology to understand the universe, the telescope. For a long time in human history, telescopes were placed in observatories located high in the mountains. A turning point in telescope history came on April 20, 1990. NASA launched the space shuttle, Discovery, with the Hubble Space Telescope (HST). After longing for so long, humankind had finally placed an eye in the universe. The HST has given clear images of the universe, contributing greatly to the measurement of the universe’s rate of expansion. On Dec. 25, 2021, 31 years after the HST marked a milestone in astronomy history, the James Webb Space Telescope (Webb, or JWST) left for the vast universe on a European Ariane 5 rocket.

How and what Webb aims to discover
An enormous and smooth mirror is required to look back in time to when the first stars start to flicker into life. Only such a mirror can collect the dim light coming from the farthest galaxies in the sky, which helps reveal the evolution of the universe from its early phases to the modern era. Webb’s primary mirror is 6.5 meters in diameter, compared to 2.4 meters of the HST. With the enormous scale of the mirror, Webb has close to 100 times the HST’s resolution. The massive size of the mirror made it hard to fit it into the launch vehicle, so it had to be folded. To fold it, the primary mirror of Webb consists of 18 hexagonal segments. As it reaches the route to its destination, ground operators will be deployed at each part of the telescope. It took 10 billion USD and three decades to realize this technology. Due to the enormous scale of the investment, one engineer put it, “This is a one-strike-and-you’re-out business.” Webb must deploy flawlessly on its first and only try. Therefore, it went through extensive tests such as the “shake test” and the “cryogenic test”, simulating various circumstances which can occur during its departure and in outer space. 

What Webb Will Bring
Many people anticipate what Webb will bring to Earth and to humankind. For astronomers and cosmologists, the data of the first stars are crucial. It is a way to figure out how dark matter works. By using the proto-galaxies, astronomers can deduce the distribution of dark matter halos’—sizes and the point of their formation. This will reveal whether dark matter is made of “cold” slow-moving particles or “warm” fast-moving particles. Astrophysicists have been simulating many possibilities for how structures emerged in the early universe. However, they need more initial conditions such as magnetic fields, and the turbulence in gases. Many theorists are willing that Webb will be their new eye, guiding them back in time. Some hope Webb will find exoplanets containing “biosignature gases”—gases existing in the atmosphere only if there is life. Oxygen is an obvious biosignature gas: due to its high reactivity, oxygen exists on the planet where there is a biosphere doing photosynthesis. However, under particular circumstances, oxygen can fill the atmosphere of lifeless planets. Therefore, it will be better to detect a peculiar mix of gases required for life. This is up to Webb, which is able to see exoplanets without the interruption of clouds and other atmosphere substances.

Edwin Hubble, an American astronomer well known for Hubble’s law and the Hubble Space Telescope named after him, once said, “equipped with his five senses, man explores the universe around him and calls the adventure science.” Truly, the HST has been the vision for humankind in the past 30 years. Now, Webb will deepen our understanding of distant exoplanets and the early time of the universe, promising to give a clearer and better sight of the cosmos.