Understanding Dark Energy and Dark Matter!

-S. Raghavan

We know that the universe is expanding. Scientists thought that the gravity from all the matter in the universe would slow down this expansion over time. But when they looked closely, they found something surprising: the expansion of the universe is actually speeding up. To explain this unexpected acceleration, scientists came up with the idea of dark energy.

Dark Energy

Dark energy is like a mysterious force that's pushing everything apart. It's kind of an invisible energy that makes the universe expand faster and faster. Dark energy is thought to make up about 68% of the entire universe. The rest comprises of mostly dark matter and normal matter (like stars, planets, and us) which makes up just about 5%.

Dark Matter

Dark matter, a strange substance that does not emit light or energy, constitutes about 27% of the universe's matter. Unlike visible matter, or baryonic matter, which includes protons, neutrons, and electrons, dark matter is detected primarily through its gravitational effects on visible objects and its influence on the universe's structure and expansion. Despite being invisible to conventional sensors, dark matter's presence is inferred from the way it bends light from distant objects and interacts with the gas in galaxies.

The concept of dark matter was introduced by Fritz Zwicky in 1933 and was later supported by the observations of astronomers like Vera Rubin and W. Kent Ford in the 1970s, who noticed that the movement of stars in galaxies indicated the presence of more matter than what is visible. This unseen matter, which does not emit light, plays a crucial role in the dynamics of galaxies.

Types of Dark Matter

There are two primary types of dark matter. One is baryonic, composed of familiar particles like protons and neutrons but does not emit light. The other, believed by most scientists is non-baryonic. The leading candidates for non-baryonic dark matter are weakly interacting massive particles (WIMPs), which are theorized to be much more massive than protons and interact very weakly with normal matter, making them extremely difficult to detect.

Additionally, hypothetical particles such as neutralinos, which are heavier and slower than neutrinos, and sterile neutrinos, a proposed fourth type of neutrino that interacts with matter only through gravity, are also considered potential constituents of dark matter. There are other theoretical candidates as well.

Matter, Dark Matter and Antimatter

Some scientists have proposed alternative theories, suggesting modifications to the laws of gravity on a large scale instead of dark matter. However, these theories often fail to explain certain astronomical phenomena, such as the separation of dark matter from regular matter during galaxy cluster collisions, which supports the distinct nature of dark matter.

In contrast, antimatter, another exotic substance, consists of particles like antiprotons and positrons, which have opposite charges compared to their matter counterparts. When antimatter and matter collide, they annihilate each other in an explosion. Unlike dark matter, antimatter can be produced in laboratories, although it is scarce in the universe.

Understanding dark energy and dark matter remains one of the most significant challenges in modern physics, with ongoing research and experimentation aimed at uncovering its true nature and composition. These enigmatic forces hold the potential to unveil unprecedented insights into the fundamental workings of the universe, offering hope for breakthroughs that may one day unlock the mysteries of the cosmos, inspiring generations of scientists and thinkers.