{
  "id": 17694707,
  "title": "Could Einstein's equations explain cosmic expansion without dark energy?",
  "url": "https://urgent.news/2026/11/01/could-einsteins-equations-explain-cosmic-expansion-without-dark-energy",
  "topic": "science",
  "section": "Science",
  "published": "2026-11-01T22:25:00.000Z",
  "source": {
    "name": "Times of India",
    "slug": "times-of-india",
    "url": "https://timesofindia.indiatimes.com/science/discovery/einsteins-equations-if-applied-more-carefully-may-hold-the-answer-to-why-the-universe-is-expanding-faster-without-any-need-for-mysterious-dark-energy-say-scientists/articleshow/135431178.cms"
  },
  "original_language": "en",
  "account": "For nearly three decades, the prevailing explanation for the universe's accelerating expansion has been dark energy. However, a team of mathematicians at the University of California, Davis, proposes an alternative theory, suggesting that Einstein's own equations may provide a simpler, more natural explanation without the need for dark energy. Their findings, published in the Proceedings of the Royal Society A, focus on the Einstein-Euler equations, which combine Einstein's general relativity with fluid dynamics. By testing the Lambda-cold dark matter model, the standard framework for explaining the universe's evolution since the Big Bang, the researchers discovered a critical flaw.\n\nThe mathematicians compared the stability of Einstein's equations to balancing a pencil on its tip. Just as a pencil balanced vertically is a solution but ultimately unstable and prone to falling, the standard model's Friedmann spacetimes are also found to be inherently unstable. According to Professor Emeritus of Mathematics at UC Davis, Blake Temple, the standard model is considered unphysical because unstable solutions in physics and science are never observed in nature. If the real universe deviates from this model, the team argues, the accelerating expansion might not require an additional source of energy.\n\nInitially, the researchers investigated whether a massive shockwave could explain the early expansion, with the unusual acceleration stemming from a wave trailing behind it. This inquiry led them to the discovery of a family of self-similar solutions during the radiation epoch of the Big Bang, potentially modeling the expanding wave. The researchers utilized Einstein's equations to examine the stability of the standard model when subjected to minor disturbances. They found that these disturbances grow rather than diminish during the period when matter dominated the universe.\n\nThe results of their analysis are compelling, indicating that the conventional mathematical descriptions of the expanding universe are susceptible to disturbances that grow rather than diminish. This finding challenges the stability of the Lambda-cold dark matter model as a viable solution to Einstein's equations of general relativity, whether or not dark energy is considered. Temple stated that this instability rules out the Lambda-cold dark matter model as a stable solution of general relativity, suggesting that the universe's expansion does not need an additional energy source. The researchers also invoke the Copernican principle, which holds that Earth and its observers are not in a special position within the universe. They argue that both the Lambda-cold dark matter model and a spherically symmetric spacetime imply a special place for observers, which contradicts the principle. If one model is ruled out by this principle, the other must be ruled out as well.",
  "summary": "Researchers from UC Davis have proposed that dark energy may not be necessary to explain the universe's acceleration. They found weak points in the Lambda-cold dark matter model using Einstein's equations. By examining instabilities in Friedmann spacetimes, they suggest alternative explanations for cosmic expansion. Their work raises questions about the Copernican principle in the context of…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}