{"id":435187,"date":"2026-01-26T22:45:12","date_gmt":"2026-01-26T22:45:12","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/435187\/"},"modified":"2026-01-26T22:45:12","modified_gmt":"2026-01-26T22:45:12","slug":"a-cosmic-anomaly-suggests-we-need-to-rethink-the-shape-of-our-universe","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/435187\/","title":{"rendered":"A cosmic anomaly suggests we need to rethink the shape of our universe"},"content":{"rendered":"

In recent years, Nobel Prize\u2013winning physicist James Peebles, one of the main architects of the standard cosmological model, has pointed out several mysteries challenging our understanding of the cosmos. While the well-known Hubble tension often takes the spotlight, a lesser-known issue \u2014 the cosmic dipole anomaly \u2014 might be even more fundamental.<\/p>\n

Late in December 2025, Indian-born astrophysicist and cosmologist Subir Sarkar, a colleague of the late Jayant Narlikar, published an article in The Conversation. In it, he presented one of cosmology\u2019s most puzzling anomalies, questioning the reliability of the standard model \u2014 much like the tension between two different measurements of the Hubble constant.<\/p>\n

This isn\u2019t an anomaly that disputes the existence of dark matter<\/a> or dark energy, but rather a subtle disagreement between predictions made before those two elements were added to the Lambda-CDM model and the vast astronomical data we\u2019ve since gathered.<\/p>\n

The discrepancy was first reported by Sarkar and his team in 2022 in a paper on arXiv, later expanded and published in Reviews of Modern Physics.<\/p>\n

It stems from data collected over recent decades \u2014 millions of distant radio sources observed by the NRAO VLA Sky Survey (NVSS) and numerous quasars captured by NASA\u2019s Wide-field Infrared Explorer (WISE).<\/p>\n

These observations allowed scientists to apply a test proposed back in 1984 by cosmologist George Ellis (known for coauthoring The Large Scale Structure of Space-Time with Stephen Hawking) and astrophysicist John Baldwin \u2014 a test now famously called the Ellis\u2013Baldwin test.<\/p>\n

\"\"<\/p>\n

South African cosmologist George Ellis. \u00a9 David Monniaux, CC by-sa 3.0<\/p>\n

A century of relativistic cosmology<\/p>\n

To grasp the significance of this finding, we need to rewind to 1917, when Albert Einstein<\/a> first applied his theory of general relativity to the Universe as a whole. His ideas were groundbreaking \u2014 but risky.<\/p>\n

At that time, scientists were still debating whether the nebulae visible in the sky were other galaxies or part of our own Milky Way. Einstein assumed they were indeed separate galaxies, evenly distributed throughout space (a property called homogeneity). He also believed the Milky Way had no special place in the cosmos, meaning the Universe should look the same in every direction \u2014 isotropic as well as homogeneous.<\/p>\n

He introduced the famous cosmological constant, now understood as a form of dark energy, to maintain a static Universe.<\/p>\n

But soon after, Friedmann and Lema\u00eetre proposed new solutions to Einstein\u2019s equations. They suggested a dynamic Universe \u2014 one that could expand or contract \u2014 with different possible geometries and even different topologies.<\/p>\n<\/p>\n

How the Big Bang theory was discovered: Einstein, Lema\u00eetre, the cosmic microwave background. Documentary excerpt from the magazine Cassiop\u00e9e, episode 4 \u201cThe Big Bang\u201d. \u00a9 Jean-Pierre Lu minet, France Supervision (1995)<\/p>\n

A homogeneous and isotropic cosmos?<\/p>\n

By the 1930s, mathematicians Howard Robertson and Arthur Walker developed what we now call the FLRW metric \u2014 the general model describing a Universe that is homogeneous and isotropic. It could be curved like a sphere, flat like an infinite plane (or torus), or curved negatively like a saddle.<\/p>\n

However, there\u2019s no guarantee the Universe is truly that uniform everywhere, or that it always was in the past. These assumptions simply make Einstein\u2019s equations easier to solve and predict. Fortunately, we can test them with precise observations.<\/p>\n

The cosmic microwave background \u2014 the faint glow left from the Big Bang \u2014 shows that 13.7 billion years ago, about 380,000 years after the beginning, the Universe was remarkably smooth. Temperature variations across the sky are tiny, meaning matter was evenly spread. Observations of distant quasars also support this, albeit with less precision.<\/p>\n

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The Italian mathematician Luigi Bianchi (1856\u20131928). \u00a9 DP<\/p>\n

A zoo of cosmological models<\/p>\n

Of course, reality might be more complicated.<\/p>\n

At the turn of the 20th century, Italian mathematicians were exploring the geometry of curved spaces, and Luigi Bianchi discovered that in three dimensions, several homogeneous but anisotropic models \u2014 ones not uniform in every direction \u2014 could exist. Later, American mathematician Luther Pfahler Eisenhart expanded this classification, showing there were more possible cosmological models than previously thought.<\/p>\n

After World War II, and especially after the discovery of the cosmic background radiation, these models were studied intensively. In fact, most advanced relativity courses \u2014 like Landau\u2019s \u2014 still cover them today.<\/p>\n

Bianchi\u2019s theory, based on the symmetries of space, ties into group theory, notably that of Sophus Lie. But you don\u2019t need to dive into the maths to understand what Sarkar\u2019s research implies \u2014 it can be pictured simply.<\/p>\n

\"\"<\/p>\n

The Bianchi classification of spaces, used in relativistic cosmology to classify various homogeneous but anisotropic models, is very similar to that of the ellipsoids in this diagram, whose symmetries vary depending on the lengths of their axes. \u00a9 Ag2gaeh, CC by-sa 4.0<\/p>\n

Imagine a sphere that looks the same from every direction. Now picture an ellipsoid \u2014 stretched along one axis \u2014 that looks different depending on how you view it. That\u2019s what an anisotropic Universe would be like. In some models, these distortions change over time, sometimes chaotically, as in a Kasner Universe.<\/p>\n

Other models begin with anisotropic expansion early on but gradually evolve toward isotropy. Such models affect how we perceive the cosmic background radiation, influencing the temperature map captured by missions like COBE in the 1990s and later refined by WMAP and Planck, which set tight limits on how much anisotropy our Universe could have.<\/p>\n

\"\"<\/p>\n

This series of false-color images was created from two years of observations of the cosmic microwave background radiation by the CoBE satellite. The colors indicate temperature variations, with the hottest areas in red and the coolest at the bottom. From top to bottom, we see the map including the cosmic dipole, then the contribution of galactic radiation in the center, and finally, at the bottom, the map without these two contributions to the microwave background radiation. The dipole, a gradual variation between relatively hot and relatively cool areas, from the upper right to the lower left corner, is due to the motion of the Solar System relative to the distant matter of the Universe. The signals attributed to this variation are extremely weak, a thousand times less bright than the sky. The following image therefore shows only the reduced map (i.e., without the dipole or galactic emission). Fluctuations in the cosmic microwave background are extremely small, on the order of 1\/100,000 compared to the average temperature of 2.73 kelvins of the radiation field. This radiation is a remnant of the Big Bang; its fluctuations reflect the density contrasts in the early Universe. These density ripples are thought to be the origin of the structures that populate the Universe today: clusters of galaxies and vast regions devoid of galaxies. \u00a9 NASA<\/p>\n

The cosmic dipole anomaly<\/p>\n

Now we can return to the so-called cosmic dipole anomaly, first spotted in data from the COBE satellite and later confirmed by Planck with greater precision.<\/p>\n

These satellites measured microwave background radiation across the sky. Most of this light dates back 380,000 years after the Big Bang, but some contamination \u2014 like dust from our own galaxy \u2014 had to be removed. Cosmologist Laurence Perotto helped clarify these foreground effects, which scientists subtracted to reveal the true signal.<\/p>\n

Because the Milky Way moves relative to the background radiation, scientists expected a Doppler effect \u2014 a shift in temperature appearing as red and blue regions in opposite directions. This pattern, called the dipole, reflects our galaxy\u2019s motion through space at about 370 km\/s.<\/p>\n

In 1984, Ellis and Baldwin predicted that once astronomers could map enough radio sources and quasars, they would detect a similar dipole pattern there too. And if that dipole didn\u2019t align with the one in the cosmic background, it would suggest a violation of the Cosmological Principle \u2014 meaning the Universe might not be as uniform as we thought.<\/p>\n

That\u2019s exactly what Sarkar and his team believe they\u2019ve found: a significant mismatch in over a million radio sources and half a million quasars. The signal, reaching five sigma in significance, suggests it\u2019s not a random fluctuation \u2014 like seeing a face in the clouds when none is really there.<\/p>\n

Still, caution is necessary. As Sarkar wrote in The Conversation:<\/p>\n

\u201cAn avalanche of data is expected from new satellites like Euclid and SPHEREx, and telescopes such as the Vera Rubin Observatory and the Square Kilometre Array. It\u2019s possible we\u2019ll soon gain unprecedented insight into how to build a new cosmological model, using advances in artificial intelligence and machine learning<\/a>.\u201d<\/p>\n

If that happens, the impact on physics \u2014 and our understanding of the Universe itself \u2014 could be truly profound.<\/p>\n<\/p>\n

APC Symposium, June 26, 2023. Speaker: Roya Mohayaee. The origin of the cosmic microwave background (CMB) dipole is attributed to the anisotropic distribution of matter in the local Universe. If the Universe is statistically homogeneous and isotropic on large scales, as proposed by the cosmological principle, then the CMB dipole and the dipole of high-redshifted matter should coincide. Based on a recent sample of quasars from the WISE survey, the CMB\u2019s proper frame of reference and that of matter do not overlap; therefore, the cosmological principle is violated. \u00a9 Astroparticle & Cosmology Laboratory (APC)<\/p>\n

\"\"<\/p>\n

Laurent Sacco<\/p>\n

Journalist<\/p>\n

Born in Vichy in 1969, I grew up during the Apollo era, inspired by space exploration, nuclear energy, and major scientific discoveries. Early on, I developed a passion for quantum physics, relativity, and epistemology, influenced by thinkers like Russell, Popper, and Teilhard de Chardin, as well as scientists such as Paul Davies and Haroun Tazieff.<\/p>\n

I studied particle physics at Blaise-Pascal University in Clermont-Ferrand, with a parallel interest in geosciences and paleontology, where I later worked on fossil reconstructions. Curious and multidisciplinary, I joined Futura to write about quantum theory, black holes, cosmology, and astrophysics, while continuing to explore topics like exobiology, volcanology, mathematics, and energy issues.<\/p>\n

I\u2019ve interviewed renowned scientists such as Fran\u00e7oise Combes, Abhay Ashtekar, and Aur\u00e9lien Barrau, and completed advanced courses in astrophysics at the Paris and C\u00f4te d\u2019Azur Observatories. Since 2024, I\u2019ve served on the scientific committee of the Cosmos prize. I also remain deeply connected to the Russian and Ukrainian scientific traditions, which shaped my early academic learning.<\/p>\n","protected":false},"excerpt":{"rendered":"In recent years, Nobel Prize\u2013winning physicist James Peebles, one of the main architects of the standard cosmological model,…\n","protected":false},"author":2,"featured_media":435188,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[49,48,12448,41938,31234,66,306],"class_list":{"0":"post-435187","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-space","8":"tag-ca","9":"tag-canada","10":"tag-cosmology","11":"tag-dark-energy","12":"tag-hubble-tension","13":"tag-science","14":"tag-space"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/435187","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=435187"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/435187\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/435188"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=435187"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=435187"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=435187"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}