Context:
An international team of scientists has unveiled the most comprehensive three-dimensional map of the universe to date. This monumental achievement could potentially provide valuable insights into the mysterious nature of dark energy, a force believed to be driving the accelerated expansion of the universe. By mapping the vast cosmic structures in unprecedented detail, researchers hope to unravel the secrets of dark energy and further our understanding of the fundamental dynamics shaping the cosmos.
Relevance:
GS III: Science and Technology
Dimensions of the Article:
- Ordinary Matter vs. Dark Matter
- Understanding Dark Energy in the Universe
- New Map of the Universe Using DESI
Ordinary Matter vs. Dark Matter
Normal Matter:
Definition:
- Normal matter encompasses everything we can directly observe, from the vast galaxies to the smallest particles.
Characteristics:
- Visibility: Observable in visible light using our eyes or specialized telescopes that can detect other light spectrums like ultraviolet or infrared.
- Composition: Predominantly consists of atomic particles such as protons, neutrons, and electrons.
- States: Can exist in various states – gas, solid, liquid, or plasma (charged particles).
Presence:
- Despite being omnipresent in our daily lives, normal matter constitutes less than 5% of the universe’s total mass-energy content.
Dark Matter:
Definition:
- Dark matter is a mysterious form of matter that doesn’t emit, absorb, or reflect light, making it invisible to current detection methods.
Characteristics:
- Visibility: Lacks visibility due to its non-reflective nature, making it undetectable by conventional telescopes.
- Composition: Despite comprising 27% of the universe’s content, its exact composition remains elusive.
Scientific Theories and Observations:
- Gravitational Effects: Scientists have inferred its existence through its gravitational effects on visible matter. Dark matter forms a vast, web-like structure known as the cosmic web, which exerts gravitational influence, pulling galaxies and other cosmic structures towards it.
- Unknown Particles: Current understanding suggests that dark matter isn’t composed of the known particles of ordinary matter. The ongoing quest involves identifying the elusive particles or entities that constitute dark matter.
Understanding Dark Energy in the Universe
Definition and Significance:
- Dark energy is a mysterious and elusive form of energy constituting a substantial portion of the total energy content in the universe.
- It is believed to drive the observed accelerated expansion of the cosmos.
Energy Distribution:
- Approximately 68% of the universe is composed of dark energy, while dark matter makes up about 27%.
- All observable normal matter on Earth, using various instruments, contributes to less than 5% of the universe.
Key Points on Dark Energy:
- Acts as an unseen force responsible for the universe’s accelerated expansion, contrary to gravity, which pulls objects together.
- Presents a new perspective on space, defining it as a dynamic and stretchable medium responsive to energy presence.
- Different forms of energy, including matter, radiation, and dark energy, uniquely contribute to the non-uniform expansion of the universe.
- Dominates the universe’s energy budget, determining the overall rate of space expansion and maintaining balance with other energy forms.
Implications of Dark Energy Amount:
- The quantity of dark energy holds significant consequences for the observable universe.
- Excessive positive energy could result in galaxies moving away faster than light, limiting visibility to nearby regions.
- Excessive negative energy might lead to the universe collapsing to a tiny point.
Characteristics and Diluteness:
- Despite dominance, dark energy is incredibly dilute across the vast universe, comparable to a single sugar crystal in a cubic kilometer.
- The diluteness raises questions about the nature and distribution of this enigmatic force.
Possible Explanations of Dark Energy
Einstein’s Cosmological Constant:
- Albert Einstein was the first to propose that empty space possesses its own energy.
- The cosmological constant in Einstein’s gravity theory suggests that the energy of “empty space” remains constant, not diluted with the expansion of space.
- This energy-of-space contributes to the accelerating expansion of the universe as more space is created.
Quantum Theory of Matter:
- According to the quantum theory of matter, “empty space” is filled with temporary (“virtual”) particles that continuously form and disappear.
Fifth Force Hypothesis:
- There are four fundamental forces in the universe, and some speculative theories propose the existence of a fifth force.
- To explain this fifth force, various models for dark energy incorporate special mechanisms.
- Some theorists refer to this hypothetical force as “quintessence,” drawing inspiration from the fifth element in Greek philosophy.
- None of these theories have been conclusively proven, leading to the characterization of dark energy as “the most profound mystery in all of science.”
New Map of the Universe Using DESI
About the Dark Energy Spectroscopic Instrument (DESI):
Functionality:
- DESI is an advanced instrument designed to capture the light from an astonishing 5,000 galaxies simultaneously.
Collaboration:
- Over 900 researchers from various global institutions are part of the DESI collaboration. Notably, the Tata Institute of Fundamental Research (TIFR) in India is the sole participating institution from the country.
Location:
- DESI is mounted on the Mayall 4-Meter Telescope located in Arizona, United States.
Achievements:
- With DESI, scientists have managed to measure light emissions from an impressive six million galaxies. Some of these galaxies are remnants from an epoch as ancient as 11 billion years ago.
Key Highlights of the DESI Study:
3-D Map of the Universe:
- Leveraging the vast data collected by DESI, researchers achieved unprecedented accuracy in measuring the distances between galaxies.
- This meticulous data collection and analysis enabled the creation of the most detailed 3D map of the universe to date.
Expansion Rate of the Universe:
- One of the significant findings from the DESI collaboration is the determination of the universe’s expansion rate.
- The study reveals that the universe’s expansion is accelerating at a rate of 68.5 km per second for every 3.26 million light-years of distance, termed as a megaparsec by astronomers.
-Source: The Hindu
