What a new 3-D map of the universe hints about the nature of dark energy?

News Excerpt:

Scientists have known that our universe is expanding at an increasingly faster pace. They believed that 'dark energy' is causing this expansion, but little is known about it. This may change soon.

Key points about the Dark Energy Spectroscopic Instrument (DESI): 

  • DESI is a unique instrument with 5,000 robotic 'eyes', i.e. the capability to observe 5,000 galaxies simultaneously, each capable of separately capturing and processing light from galaxies.
  • It is mounted on the Nicholas W. Mayall 4-meter Telescope at the Kitt Peak National Observatory in Arizona, USA.
  • It has been operating for three years and is scheduled to continue for at least two more years.
  • Data from the first year of DESI observations
    • It captures light from 6 million galaxies, some of which existed as far back as 11 billion years ago, 
    • It has been used to create the most comprehensive three-dimensional evolutionary map of the universe to date.
  • Using the first year's observational data:
    • The DESI collaboration has calculated that the speed of expansion of the universe is increasing at a rate of 68.5 km per second after every 3.26 million light-years of expansion.
  • Some of the calculated values from DESI's observations are not consistent with current well-established theoretical models that describe the universe very well.

Dark energy intensity:

  • Dark energy is causing the universe to expand more rapidly over time
    •  It is considered a constant in the leading model of cosmology.
  •  The confidence level of these observations is currently around 2.5 sigma, or 95% confidence, which is not enough for a scientific discovery of such magnitude and implications. 
    • A higher confidence level of 6 sigma, or near certainty, is required.
  • If the changes in dark energy density are confirmed, it could lead to a complete overhaul of our current understanding of the universe. 
    • It would provide the first glimpse into the nature of dark energy, which is currently unknown.
  • Speculations about the nature of dark energy include it being a new invisible field (like electric, magnetic, or gravitational) or a new particle. 
    • The scientific community is keenly observing the DESI data for further insights.
  • It accounts for approximately 68% of the total energy content of the universe as: 
    • Astronomers have observed other galaxies getting farther away from us over time, they know the universe is expanding. 
    • The pull of gravity implies this expansion should be slowing down—but over the past 7.5 billion years, it’s been getting faster.
  • The new research culminated in a 3D map measuring how the universe has expanded over the past 11 billion years
    • The data was collected by the Dark Energy Spectroscopic Instrument (DESI)
  • The DESI collaboration plans to analyze data from subsequent years of observations immediately to further investigate the potential changes in dark energy intensity.
  • The key points focus on the theoretical implications of constant versus changing dark energy density, the initial hints from DESI data, 
    • The required confidence levels for scientific discovery, and the potential for new physics if changes are confirmed.

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