Final answer:
The universe's destiny is largely determined by the balance between dark matter and dark energy, with dark energy causing an accelerated expansion that suggests the universe will expand forever.
Step-by-step explanation:
The amount of dark matter and dark energy in the universe plays a crucial role in its long-term evolution and fate. Dark matter contributes to the gravitational forces that hold galaxies and their clusters together, while dark energy is responsible for the acceleration of the universe's expansion.
If only dark matter and ordinary matter were present, the universe might eventually stop expanding and begin to contract.
However, with the discovery of dark energy, which appears to be growing more significant over time and acts over large scales, the current evidence strongly suggests that the universe will continue to expand forever at an accelerating rate. This conclusion is further supported by observations showing that the expansion has been speeding up since the universe was about half its current age.
The Cosmic Tug of War concept describes the competing forces at play: gravitational attraction pulling matter together versus dark energy pushing spacetime apart.
Astronomical measurements, such as the observed galactic redshifts, suggest that dark energy is winning this tug of war, indicating an eternally expanding universe. Scientists attribute a staggering 68.3% of the energy content of the universe to dark energy, with 26.8% to dark matter, leaving only a small fraction for the mass-energy of ordinary particles.