DARK MATTER (Syllabus: GS Paper 3 – Sci and Tech)

Context: New research in Physical Review Letters (PRL) has proposed a novel method to detect light dark matter candidates using laser interferometry to measure the oscillatory electric fields generated by these candidates.

Dark Matter

• About: It is a hypothetical form of matter that is believed to exist in the universe but is invisible and does not interact with light. It makes up over 80% of all matter in the universe.
• Dark Energy: Dark energy is an invisible force that works against gravity, thus, causing the universe to expand.

oOn the other hand, Dark matter exercises a gravitational pull on the universe, and more dark matter means universe will contract, and have a closed geometry, ending in a Big Crunch.

• Universal Pressure: Dark energy is a form of energy that fills the entire universe and exerts a negative pressure, pushing galaxies and other matter away from each other.
• Features: Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot (It has not been discovered so far).
• How do we know Dark Matter exists? - Dark Matter has mass, hence the gravitational pull. Thus, it can only be detected by its gravity effects. We can sense the dark matter present in the galaxy based on the distortion it causes (for e.g. bending of light etc.)
• Importance of Dark Matter

oStructural Explanation: Dark matter is essential to explaining the observed structure of the universe.

oGalactic Distribution: It helps to account for the distribution of matter in galaxies and the cosmic web.

oUniversal Understanding: Understanding dark matter is important for developing a complete understanding of the universe and its evolution.