Yes, the ratios of dark energy, dark matter, and baryonic (ordinary) matter have changed over the course of the universe's evolution and continue to evolve. Here's how and why:
### Early Universe
1. **Radiation-Dominated Era**:
- Shortly after the Big Bang, the universe was extremely hot and dense, and radiation (photons and neutrinos) was the dominant form of energy.
- During this time, the contributions of dark matter and dark energy were negligible compared to radiation.
### Matter-Dominated Era
2. **Dark Matter Dominance**:
- As the universe expanded and cooled, matter began to dominate over radiation. Dark matter, which interacts gravitationally but not electromagnetically, played a crucial role in the formation of large-scale structures like galaxies and clusters of galaxies.
- Baryonic matter, although a smaller component compared to dark matter, clumped together under gravity, forming stars, galaxies, and other visible structures.
### Dark Energy Dominance
3. **Emergence of Dark Energy**:
- About 4 billion years ago, the influence of dark energy became significant. Dark energy, responsible for the accelerated expansion of the universe, started to dominate over both dark matter and baryonic matter.
- The current composition of the universe is roughly 74% dark energy, 21% dark matter, and 5% baryonic matter. These values are based on observations such as the cosmic microwave background radiation, large-scale structure, and Type Ia supernovae.
### Future Evolution
4. **Continued Expansion**:
- As the universe continues to expand, the density of dark matter and baryonic matter will decrease because they are diluted by the expanding space.
- Dark energy, often modeled as a cosmological constant with a constant energy density, will remain the dominant component. Its relative contribution to the total energy density of the universe will increase over time.
5. **Asymptotic Behavior**:
- In the far future, if dark energy behaves as a cosmological constant, it will drive the universe towards an accelerated expansion indefinitely. The ratios will shift even more in favor of dark energy.
### Summary
- **Early Universe**: Radiation-dominated, with negligible dark matter and dark energy.
- **Matter-Dominated Era**: Dark matter dominates, aiding structure formation, with baryonic matter forming visible structures.
- **Current Era**: Dark energy is the dominant component, causing the accelerated expansion of the universe.
- **Future**: Dark energy's influence will continue to grow, further decreasing the relative contributions of dark matter and baryonic matter.
In conclusion, the ratios of dark energy, dark matter, and baryonic matter have evolved over time and will continue to do so as the universe expands. This dynamic change reflects the shifting balance of energy components driving the evolution of the cosmos.
