Early galaxies observed with JWST
The Suddenly-Aging Universe
As of mid-July 2023 and through the time of this writing, a Google search for the age of the universe might lead you to a perplexing contradiction. Google provides a top answer of 26.7 billion years, while Wikipedia states that it is as 13.8 billion years. This larger number of 26.7 billion years is nearly twice the other value and comes from a new study using novel approaches to reinterpret the age of the universe. I fully acknowledge that my Twitter feed is not a representative sample of scientific opinion, however, if you were browsing through it on July 18th you would have heard the sound of dozens of physicists’ eyes rolling. For example sci-com mavens Chandra Precod-Weinstein (theoretical cosmologist and particle physicist at the University of New Hampshire) and Katie Mack (theoretical cosmologist at the Perimeter Institute for Theoretical Physics) both retweeted University of Texas at Austin Professor, Mike Boylan-Kolchin's, thread describing, in Prescod-Weinstein's words, "why we are fairly confident that the age of the universe is just under 14 billion years." Indeed, the younger age is the more established number, more widely accepted and adopted and many people argue, is better supported by data. And yet Google pronounces the older number with an aura of official correctness. In this age of conspiracies and scientific literacy, it's important to be able to parse truth from fiction. The question of which value should be considered "the correct one" speaks to how we acquire knowledge and who we can trust for answers to complex questions beyond our expertise.
To look at why we are forced to rely on experts, let’s take a step back and consider the arc of humanity from our early foraging past to where we are today. Influenced by the invention of agriculture, specialization has played a crucial role in the progress of human civilization. When no longer directly focused on producing food, people could begin to focus on other tasks. Some individuals became skilled artisans, traders, religious leaders, etc. Focusing on a specific area allows someone to excel in that field, freeing them from the burden of being experts in everything. I am personally quite grateful for the opportunity to specialize in the study of planets. This is a profound and meaningful pursuit that does not directly put food on anyone's table but my own. However, the constraints of my profession mean that I can't be an expert in all the things I might want to be. For example, I'd like to be more versed in law and politics, but constraints on my time mean that I must be able to turn to others as experts in those fields. As much as I rely on experts in law and politics to provide me accurate, fair, clear and accessible information, it's the duty of those who study space science to provide information to the general public in the same way. Given the significance of this reliance on experts, it's troubling when platforms like Google highlight an answer that is probably ... well, likely way off.
Unveiling the Secrets: How the Ages were Derived
How are we able to know the age of the universe, anyway? Fundamentally, we can determine the age of the universe by analyzing the spectrum of starlight from faraway galaxies. It relies on the Doppler effect, which can be explained through an analogy to sound waves. The sound of a train or an ambulance speeding towards you will be increased in pitch because the sound waves are compressed in your direction. Once it barrels past you, the sound it makes decreases in pitch as the space between the sound waves increases. Light from stars behaves in a similar way. When stars move towards us, their light becomes blue shifted, meaning the waves are compressed or shortened. Conversely, when stars move away from our vantage point, their light becomes red shifted, meaning it is stretched to a longer wavelength.
Scientists can identify whether a star is red-shifted or blue-shifted by examining its spectrum, which breaks down the light from a star into its various wavelengths. Remarkably, the starlight from most galaxies shows redshift, indicating that these galaxies are moving away from each other. This observation aligns with the concept of an expanding universe, an idea that gained theoretical support in the 1920s and was subsequently confirmed by Edwin Hubble. He studied the redshift of Cepheid variable stars in other galaxies, using their properties to calculate their approach or recession speed. Henrietta Swan Leavitt's earlier investigation of thousands of Cepheid stars proved crucial in this process. She discovered a relationship between the time it takes for these rapidly pulsating stars to vary in diameter in temperature and their intrinsic luminosity. The stars in the night sky vary widely in brightness, however, their perceived brightness is a function both of their intrinsic luminosity (how bright they actually are) and how far away they are. Since a star will appear much dimmer to us if it further away than another star of identical brightness . With the knowledge of how far these stars were along with how fast they are receding, Hubble was able to estimate the expansion rate of the universe.
By pushing rewind back to the big bang, an age for the universe can be derived using the equation for speed = distance / time. Since the accuracy of the stellar distance calculations is limited by the power of the telescopes, up until the 1990's, the capabilities of the ground-based telescopes available meant that scientists were only able to constrain the age of the universe to between 7 and 20 billion years. The uncertainties on this estimate were narrowed with the launch of the Hubble Space Telescope in 1993, allowing the age of the universe to be constrained to between 9 and 14 billion years old. Another approach has been to measure fluctuations in the cosmic microwave background. These long-wavelength microwaves can be found in every direction and represent the heat leftover from the Big Bang. By using fundamental physics, scientists tested thousands of models of the early expansion of the universe with varying parameters, finding that the ones that best match our current observations give an age of the universe to around 13.8 billion years old.
So, how did we get to 26.7 billion years old? Researchers at the University of Ottawa published a paper on July 7 giving this new age for the age of the universe based on observations that were inconsistent with the previously derived value. The observations in question include the existence of stars like Methuselah, which seem to be older than the age of the universe as previously estimated. Additionally, data from JWST revealed that the earliest observed galaxies, dating back to 300 million years after the Big Bang, appeared more mature than typical galaxies of that age. To explain this new age, the researchers of this new paper invoked the theory of "tired light." According to this hypothesis, the redshift of light from distant galaxies occurs due to the gradual energy loss of photons over immense cosmic distances. They also allowed certain physical constants to vary over time, using these variations to derive the new age value of 26.7 billion years.
The "tired light" theory has not been substantiated by other studies, in fact, it has some problems. UCLA Professor, Ned Wright, has summarized some of these on his website. First, things that change a photon's wavelength and energy over time, also change its momentum (speed and/or direction). If photons did lose energy during their travels as the tired light theory proposes, very distant objects would also change momentum, causing them to become blurry; which is not what we observe. Secondly, the "tired light" theory is unable to account for a consequence of general relativity called time dilation, wherein time can pass at different rates depending on the relative motion between two observers. We have observed this phenomenon in space, for example, under a significant red-shift decay of a supernova can be observed to take longer than average when the exploding star is observed at a significant red-shift.
The Uneasy Journey of Trusting the Experts
The news of this 100% increase in the age of the universe garnered attention from various outlets. The findings in this paper are splashy and the result is a simple number that can be shared in a headline and easily understood (though the nuances of the methods are not). Some news sources added the kind of context and words of caution that scientists generally include in the kind of research paper that passes peer review and in their interviews with the media, however, these often don't end up in the final articles. The depth of the coverage of novel research like this varies, but some of the outlets for this finding with the least context came from news sources like USA Today, Daily Mail, Joe Rogan, though other news outlets like Sci.news and Phys.org also provided little context and eschewed discussions of the drawbacks of this study. As a non-scientist consumer of news media or a student using Google to find simple scientific facts, you might look at these headlines and reasonably conclude that this older number is correct.
This situation underscores the importance of media literacy, as we strive to make informed choices about our news sources. The infotainment filter through which scientific news is delivered to the public can be toxic, obscuring the complexities of scientific concepts. Journalists, under the pressure of today's fast-paced media environment, may lack the time and resources to develop more than the most tenuous grasp of the underlying science. Navigating this information landscape can be challenging for non-experts; there is no simple answer. A robust news system with more resources for in-depth reporting, less dependent on billionaires and corporations, would mean a world of difference for the public. In my view, journalism should not be trapped in the daily meat grinder of capitalism.
Ultimately, the truth is not so easy to wrangle and pin down. We are better served when we can count on messengers of scientific information. For the field of science, it is essential that the data supporting conflicting claims is clearly stated and transparently available - a vital resource for those with the time to look into it. Even with all this, a person can still easily be left craving more certainty. While a seemingly regrettable situation, this state of affairs does provide job security to scientists and ensures that humankind will always have available to them a sense of wonder and an impetus to know more. Regardless of age, the universe is built to keep the thrill of scientific breakthrough ever on the horizon.
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