The Universe can seem inscrutable, but space telescopes are rapidly helping us expand our knowledge base.
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Contemplating the mysteries of the cosmos has an uncanny way of awakening profound reflection. How big is the Universe? How old is it? Is it finite, or is it infinite? Is it growing? What is its shape? Is it a sphere, like a round balloon, or is it formless, even multidimensional?
Continuing along these lines opens up even more avenues of thought. If the cosmos started with the Big Bang, just what existed before that? Can a telescope see so far that it can perceive the beginning of time?
Lucky for us, there’s no quiz. Even if there were, many of these questions have no answer – science hasn’t yet delivered a verdict on many of the granular considerations that add up to an all-encompassing picture of our cosmic home. Pondering the cosmos ever more expansively, we are yet challenged to persevere. Let’s see what kind of a picture we can paint of the nature of the Universe.
For more on the James Webb Space Telescope, check out the MagellanTV original documentary Search for the Cosmic Dawn.
Phases of the Early Universe
Over the past century, a scientific consensus has developed and refined the idea that the Universe began in a dramatic explosion of energy about 13.8 billion years ago – a concept known as the Big Bang. The term “Big Bang” itself was coined in 1949 by British astronomer Fred Hoyle, but the foundations of this model were laid earlier through the combined efforts of observational astronomers like Edwin Hubble and theoretical physicists, including Albert Einstein. These pioneers established the widely accepted framework for understanding the early development of the cosmos.
The growth of the Universe from the Big Bang to its current state is typically divided into three main epochs:
The Energy-Dominated Epoch (~13.8 billion years ago)
The Universe began with an extraordinary burst of expansion that lasted mere fractions of a second. This moment was marked by extremely high energy and rapid events that set the stage for the Universe’s structure. Key developments during this epoch included:
- Inflation: The Universe expanded exponentially, smoothing out irregularities and establishing a uniform foundation.
- Cooling: Expansion continued as temperatures dropped rapidly, allowing fundamental particles like quarks and gluons to form.
- Particle formation: Quarks combined to form free protons and neutrons, the building blocks of atomic nuclei.
- Ionization: In the very early Universe, all matter was highly ionized, essentially existing as a “soup” of protons, neutrons, and electrons. During ionization, there were ions but no atoms.
- Separation of forces: Initially unified, the fundamental natural phenomena – gravity, electromagnetism, the weak and strong nuclear forces – began to diverge.
This epoch laid the groundwork for matter, galaxies, stars, and all the other cosmic structures.
A representation of the evolution of the Universe (Source: NASA/WMAP Science Team, via Wikimedia Commons)
The Matter-Dominated Epoch (~380,000 years after the Big Bang)
As the Universe continued to cool, it entered the era of recombination, during which electrons combined with protons to form the first hydrogen atoms, known as neutral hydrogen. The term “neutral” refers to atoms that had not yet been ionized. (Ionization will happen later.) The formation of these neutral atoms allowed the release of the cosmic microwave background (CMB) radiation – a faint afterglow, which will come up for discussion below.
However, the Universe remained dark because no stars or galaxies had yet formed. This period, known as the Dark Ages, lasted until about 100 million years after the Big Bang. During this time, neutral hydrogen gas filled the cosmos, and gravitational forces began to clump matter together, forming the seeds of stars and galaxies.
The Dark Ages ended when the first stars formed and emitted ultraviolet radiation. This radiation reionized the prevalent hydrogen gas, effectively splitting it into protons and electrons. Then came the era of reionization, a transition to a Universe filled with reionized hydrogen and visible ultraviolet light.
As the post-Big Bang Universe cooled, free protons and electrons combined as “neutral hydrogen,” consisting of one proton and one electron. Later high-energy radiation “reionized” the neutral hydrogen, stripping electrons from the atoms once again.
The James Webb Space Telescope is leading the way in observing this critical period of early star and galaxy formation. It focuses on the early objects, so very large ground telescopes can hone in for detailed looks.
The Dark Energy–Dominated Epoch (~10 billion years after the Big Bang to now)
Roughly 10 billion years after the Big Bang, the Universe entered a new phase dominated by dark energy. Scientists theorize that this mysterious force drives the Universe’s accelerating expansion, which continues today. In this epoch, increasing numbers of galaxies and other large-scale structures formed and evolved, and dark energy began to overpower gravitational forces, causing the rate of expansion to increase.
This is the epoch we live in today, but its implications extend far into the future. In about two trillion years, the cosmos will become so expansive that distant galaxies will recede beyond visibility, leaving any future observers in the Milky Way unable to detect them.
For now, we are fortunate to live in an era when advanced telescopes can look back in time to observe the Universe’s history, from the first galaxies to the CMB. Below, I’ll discuss the tools currently revolutionizing our understanding of the early Universe and the innovations poised to uncover even deeper cosmic secrets.
Imaging the Early Universe
In 1964, while searching for flaws in a proprietary radiometer, two engineers at Bell Laboratories in New Jersey made the astonishing discovery of the early Universe’s cosmic microwave background radiation. While they were testing the radiometer’s ability to monitor radio signals in space, their machine actually recorded the earliest radio wave signal of all time: the “sound” of the Big Bang, what we call the CMB.
A map of cosmic background radiation from when the Universe was around 380,000 years old. Source: NASA / WMAP Science Team, via Wikimedia Commons)
This discovery has allowed scientists to map the effect of the Big Bang’s initial moment. It has given us, in essence, the earliest picture of the cosmos in its formative state. Since the 1960s, there have been numerous telescopes, both operational and planned, whose goal is to capture light from the early Universe. While these telescopes – including the Hubble Space Telescope and the James Webb Space Telescope (JWST) – have indeed recorded amazing images of galaxies and other space structures from the early Universe, none is designed to peer back as far as the CMB. That image is still the earliest evidence we have of the Big Bang.
This is not a fault of the telescopes; rather, these scientific marvels intend to look for light in and even before the Universe’s period of reionization, when the “neutral” hydrogen atoms that filled the early Universe were ionized by the intense ultraviolet radiation emitted from the first stars and galaxies. The earliest galaxies the JWST has detected are in what’s defined as the “Dark Ages,” around 300 million years after the Big Bang. Now, radio telescopes are attempting to enhance our understanding of this light-lacking era.
The Hubble Space Telescope
Science got a huge kick forward with the launch of the Hubble in 1990. Searching for the earliest stars and galaxies that developed during and after the period of reionization around 13 billion years ago, its advances and discoveries have reshaped the fields of physics, astronomy, and cosmology. Among its celebrated successes have been:
- The precise measurement of the rate of expansion of the Universe (known as the “Hubble constant”), recently refined by new data from the JWST;
- The observation of the mysterious dark energy that appears to be driving the Universe’s accelerated expansion; and
- Stunning images of distant galaxies, nebulae, and other cosmic phenomena.
One of the most profound contributions was the discovery that the Universe’s expansion is accelerating, leading to the identification of dark energy as a dominant force in the cosmos’s evolution.
The James Webb Space Telescope
The JWST only became operative early in 2022, but already its discoveries have stunned scientists – and the public – worldwide, leading to some new conundrums that have been presented by the JWST and are not yet explained. These discoveries have expanded our understanding of the cosmos, but they have also raised challenging questions, including:
- What led to rapid star formation in the early Universe? How did galaxies develop such complexity in such a short period?
- What exactly is dark matter, and how does it influence the formation of galaxies and the large-scale structure of the Universe?
- How did supermassive black holes form so early in the Universe’s history? What role do they play in galaxy formation and evolution?
- Could newly discovered exoplanets harbor life, or are the conditions too extreme for any form of life to exist?
As the JWST continues to peer deeper into the cosmos, these mysteries are likely to grow, driving new research and potentially rewriting much of what we know about the cosmos and our place in it.
The Nancy Grace Roman Space Telescope and SPHEREx Missions
The Nancy Grace Roman Space Telescope and SPHEREx are two upcoming NASA missions designed to enhance our understanding of the early Universe.
The Roman is scheduled for launch in May 2027. It features a primary mirror the same size as the Hubble’s but with a field of view 100 times larger. This will enable it to capture a much wider view of the cosmos, which is crucial for studying dark energy and for conducting surveys of exoplanets.
NASA’s Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, or SPHEREx (artist rendering) (Source: NASA)
SPHEREx, or Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, is a smaller mission set to launch in February 2025. It will perform an all-sky survey, measuring near-infrared spectra. This survey aims to map the distribution of galaxies, study the epoch of reionization, and investigate the origins of water in planetary systems.
Both missions are poised to significantly advance our knowledge of the cosmos.
A New Era of Exciting Space Exploration
We are advancing ever closer to new discoveries that will both enhance and challenge our understanding of the early cosmos, how it developed, and what conditions are necessary to foster life of any kind on cosmic exoplanets.
These missions are opening new frontiers in our quest to understand the origins of life. Collectively, they are pushing the boundaries of astrophysics and astrobiology, offering the potential for discoveries that could reshape our understanding of the cosmos and the possibility of life beyond Earth.
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Kevin Martin is Senior Writer and Associate Editor for MagellanTV. A journalist and communications specialist for many years, he writes on various topics, including Art and Culture, Current History, and Space and Astronomy. He is the co-editor of My Body Is Paper: Stories and Poems by Gil Cuadros (City Lights) and resides in Glendale, California.
Title Image: Set to launch in 2027, the Nancy Grace Roman Space Telescope will help settle pressing questions about dark matter and dark energy. (Source: NASA)
