Context:
The universe’s energy distribution involves a delicate equilibrium. Dark energy, comprising 68% of the total, emerges as the dominant force influencing the universe’s expansion.
Relevance:
GS III: Science and Technology
Dimensions of the Article:
- Understanding Dark Energy in the Universe
- Possible Explanations of Dark Energy
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.”
-Source: The Hindu
