SUPRIYO SAHA

What is Cosmology?

Cosmology is the study of the universe, including its origin, structure, evolution, and eventual fate. It covers everything from the smallest particles to the largest cosmic structures. The universe began with the Big Bang about 13.8 billion years ago and has been expanding ever since.

The Evolution of the Universe

• 0 seconds: The Big Bang - space, time, and matter begin.
• 10⁻³⁶ seconds: Cosmic Inflation - the universe expands exponentially.
• 10⁻⁶ seconds: Formation of protons and neutrons.
• 380,000 years: Recombination - atoms form, and the universe becomes transparent (CMB forms).
• 200 million years: First stars and galaxies form.
• 9 billion years: The solar system forms.
• 13.8 billion years: Present-day universe with galaxies, dark matter, and dark energy.

Today, cosmologists study dark matter, dark energy, and the large-scale structure of the universe to understand its future evolution.

Key Components of the Universe

The universe is composed of several key components, including:

• Ordinary Matter: The visible matter that makes up stars, planets, and living organisms.
• Dark Matter: A mysterious form of matter that does not emit light but has gravitational effects on visible matter.
• Dark Energy: A form of energy responsible for the accelerated expansion of the universe.
• Cosmic Microwave Background (CMB): The afterglow of the Big Bang, providing a snapshot of the universe when it was only 380,000 years old.

My Research Field - COSMOLOGY

As a cosmologist, my research spans multiple areas within this vast field. Below are some of the topics I am exploring:

• Cosmic Inflation: Studying the rapid expansion of the universe in the first moments after the Big Bang.
• Gravitational Lensing: Investigating how massive objects bend light and can be used to map dark matter and study distant galaxies.
• Dark Matter and Dark Energy: Understanding the invisible components of the universe that make up most of its mass-energy content.
• Large-Scale Structure: Analyzing how galaxies are distributed across the universe and understanding their evolution.

The Fate of the Universe

Cosmologists debate the ultimate fate of the universe. Some of the possibilities include:

• Big Freeze: The universe continues expanding, and galaxies, stars, and planets drift apart, eventually leading to a cold, dark universe.
• Big Crunch: The expansion of the universe slows and reverses, leading to a collapse back into a singularity.
• Big Rip: The expansion of the universe accelerates, tearing galaxies, stars, and even atoms apart.

What is Gravitational Lensing?

**Gravitational lensing** occurs when the gravitational field of a massive object bends the path of light from distant sources. This effect, predicted by Einstein's General Theory of Relativity, acts like a natural cosmic telescope, magnifying and distorting distant galaxies. Weak lensing is a powerful tool for cosmologists**, allowing us to probe the distribution of **dark matter** and study the **expansion of the universe**.

Cosmic Microwave Background (CMB)

The CMB is the faint glow left over from the Big Bang, providing a snapshot of the universe when it was just 380,000 years old. It carries information about the early universe, the formation of galaxies, and the distribution of matter.