The universe contains far more than just observable matter; astronomers have discovered that a large portion of the universe is filled with two mysterious components—dark matter and dark energy—that cannot be directly observed but whose existence is inferred from gravitational effects.

Dark Matter: The Skeleton of the Universe

Dark matter is a type of matter that does not emit or absorb light, making it undetectable through direct observation. Its existence has been proven through observations such as the unexpectedly fast rotation of galaxies, the gravitational binding of galaxy clusters, and gravitational lensing on cosmological scales.

Why do we need dark matter?

The amount of observable matter is not sufficient to provide the gravitational force needed for galaxies and galaxy clusters to stay together. Dark matter supplies the missing gravitational force, helping to hold the structure of the universe together.

Properties of dark matter: Dark matter interacts weakly with normal matter and, being insensitive to electromagnetic forces, it neither emits nor absorbs light, making it undetectable through direct observation.

Candidates for dark matter: Scientists have developed various theories about what particles could make up dark matter. Research continues on candidates such as WIMPs (Weakly Interacting Massive Particles), axions, and MACHOs (Massive Compact Halo Objects).

Dark Energy: The Force Expanding the Universe

Dark energy is a form of energy believed to be responsible for the accelerated expansion of the universe. It behaves as if it is spread throughout all of space, creating negative pressure that accelerates the expansion of space.

Why do we need dark energy?

While the expansion of the universe was expected to slow down over time, observations have shown that the universe is instead expanding at an accelerating rate. The concept of dark energy was introduced to explain this acceleration.

Properties of dark energy: Dark energy is a form of energy that is homogeneously distributed throughout the universe, creating negative pressure. Its nature is not yet fully understood.

Models of dark energy: Various models for dark energy have been proposed, including the cosmological constant, scalar fields, and modified gravity theories.

The Role of Dark Matter and Dark Energy in the Universe

The energy content of the universe is approximately 68.3% dark energy, 26.8% dark matter, and only 4.9% normal matter. This shows that a large portion of the universe is dominated by these two components, which cannot be directly observed.

In conclusion, dark matter and dark energy are among the greatest mysteries of the universe. Understanding the nature of these mysterious components will help us gain a deeper insight into the formation, evolution, and ultimate fate of the universe. Scientists continue to conduct new experiments and observations to learn more about them.