It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest – everything on Earth, everything ever observed with all of our instruments, all normal matter – adds up to less than 5% of the universe. Dark energy and dark matter are two mysterious phenomena in astrophysics that have been observed indirectly but have not yet been directly detected or fully understood.
Dark matter is a hypothetical form of matter that does not emit, absorb, or reflect light, which is why it is “dark”. It is thought to make up about 27% of the total mass energy in the observable universe, whereas ordinary matter (the stuff that stars, planets, and we are made of) makes up only about 5%. Dark matter is inferred to exist because its gravitational effects can be seen on visible matter, such as stars in galaxies and galaxy clusters. Astronomers believe that dark matter is composed of yet-undiscovered subatomic particles that interact with ordinary matter only through gravity.
Dark energy is another mysterious phenomenon that is causing the expansion of the universe to accelerate. Unlike dark matter, which has a gravitational effect that pulls matter together, dark energy has a repulsive effect that causes the universe to expand at an accelerating rate. Dark energy is thought to make up about 68% of the total mass energy of the universe. It is currently not well understood, and scientists are exploring different theories to try to explain it, such as the possibility of a “cosmological constant” or a dynamic scalar field.
Both dark matter and dark energy are areas of active research in astrophysics and cosmology, and scientists are continuing to study them in order to better understand their properties and the role they play in shaping the universe as we know it.