Indirect evidence builds, yet the ‘dark’ universe remains murky
- June 17, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Indirect evidence builds, yet the ‘dark’ universe remains murky
Sub: Science and tech
General Theory of Relativity and Dark Universe
General Theory of Relativity:
- The general theory of relativity has excelled in explaining gravity and phenomena like gravitational waves, lensing, redshift, black holes, and time dilation, refining Newton’s laws by describing gravity as a geometric property of spacetime.
- However, on a cosmic scale, space appears filled with dark energy, constituting about 70% of the universe’s energy, causing the universe to expand.
- This contrasts with Newtonian gravity, which pulls objects together.
Important terms:
Gravitational Waves |
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Gravitational lensing |
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Redshift |
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Black hole |
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Time Dilation |
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Dark Energy:
- Observed at cosmic scales, dark energy permeates space, causing the universe’s expansion.
- Comprises 70% of the universe’s energy from the Big Bang.
- Creates negative pressure, stretching spacetime and allowing stars and galaxies to drift apart.
- Dominates in empty space, whereas gravity prevails in matter-rich regions.
Dark Matter:
- Proposed based on cosmological observations; first indirect evidence published by Vera Rubin 44 years ago.
- Explains unexpected galactic rotation rates, suggesting invisible matter exerts additional gravitational force.
- Remains hypothetical; no direct evidence yet.
Scientific Debate:
- Not all scientists agree with dark matter and dark energy hypotheses.
- Some propose alternate gravity paradigms, but they don’t fully explain observed phenomena like dark matter and dark energy do.
DESI and Lambda-CDM Model:
- Broadband Search for Dark Photon Dark Matter (BREAD) search and the Dark Energy Spectroscopic Instrument (DESI) aims to create a detailed 3D map of the universe.
- By mapping the position of thousands of galaxies over many years, we can keep measuring how much the universe’s expansion due to dark energy is accelerating.
- But for now, we have no choice but to draw all our inferences about dark matter and dark energy from indirect evidence alone.
- Data supports the Λ-CDM model, with Λ (lambda) representing dark energy’s density.
- Λ (lambda) is the cosmological constant: it represents the energy density of space and is closely associated with dark energy.
- It appears in equations of the general theory of relativity.
- Some studies suggest dark energy might change over time, challenging the Λ-CDM model.
- Modified theories like MOND, which don’t require dark energy, face challenges, such as data from the Cassini mission not supporting its predictions.
Source: TH