Scientia India

Dark Energy: The Universe’s Mysterious Accelerant If dark matter pulls things together, dark energy tears them apart. It’s the unseen force responsible for the accelerated expansion of the universe — a phenomenon so bizarre, it shocked cosmologists in the late 20th century. Missed our earlier posts? Catch up here: Dark Matter | Spiral vs Elliptical Galaxies 🌌 Discovery of Dark Energy In 1998, two independent teams observed distant supernovae and found that the universe’s expansion is speeding up, not slowing down. Something was pushing galaxies apart — a mysterious form of energy that came to be known as dark energy . 📊 Einstein’s Equation Revisited Einstein’s general relativity field equation includes a term known as the cosmological constant (\(\Lambda\)): $$R_{\mu\nu} - \frac{1}{2}R\,g_{\mu\nu} + \Lambda g_{\mu\nu} = \frac{8\pi G}{c^4}T_{\mu\nu}$$ Originally ad...

What holds galaxies together, controls their spin, and outweighs all the visible stars? Welcome to the mysterious realm of dark matter — the invisible glue of the universe. If you’re joining us now, catch up with previous posts: Spiral vs Elliptical Galaxies | Galaxies | What is the Universe? 🔍 What is Dark Matter? Dark matter does not emit, absorb, or reflect light, making it completely invisible. Yet, scientists know it exists because of its gravitational effects on visible matter. 🧠 Scientific Estimate: About 27% of the universe is dark matter. Only 5% is normal matter. 📈 Evidence for Dark Matter Galaxy Rotation Curves: Stars in galaxies orbit faster than visible mass allows. Gravitational Lensing: Light bends around unseen mass, revealing dark matter’s presence. Cosmic Microwave Background: Tiny fluctuations suggest invisible matter affects early universe structure. ...

The Big Bang: How It All Began The universe wasn't born in silence — it began with a rapid expansion called the Big Bang . At this moment, space and time emerged from a singularity. From nothing came everything: particles, energy, space, and laws of physics. Let's dive deep into its story, timeline, and math! If you're just joining us, catch up on earlier posts: What is the Universe? | Galaxies – Cosmic Cities of Stars | Spiral vs Elliptical Galaxies 🧨 What Was the Big Bang? The Big Bang was the beginning of the universe approximately 13.8 billion years ago. At \( t = 0 \), all matter was concentrated in a point of infinite density and temperature: a singularity. As time progressed, space itself expanded. This is described by the Friedmann Equation derived from Einstein's General Relativity: \[ \left( \frac{\dot{a}}{a} \right)^2 = \frac{8\pi G}{3} \rho - \frac{k}{a^2} + \frac{\Lambda}{3} ...

Spiral vs. Elliptical Galaxies: How Shape Defines Destiny In the grand architecture of the universe, galaxies come in various forms. Among them, spiral and elliptical galaxies stand out as the two most prominent types — each telling a different story of cosmic evolution and stellar life. Before diving in, catch up with our previous guides: What is the Universe? and Galaxies: Cosmic Cities of Stars, Dust, and Dark Matter . 🌀 Spiral Galaxies Spiral galaxies have a flat, rotating disk with curved arms spiraling outward from a dense central bulge. These graceful arms contain young, bright, hot stars and vast star-forming regions. Structure: Central bulge, disk, spiral arms, and surrounding halo Star Population: Mix of young and old stars Gas and Dust: Rich in interstellar material; active star formation Examples: Milky Way, Andromeda 🌌 Fun Fact: The Milky Way is a barred spiral galaxy with arms winding ...

Galaxies: Cosmic Cities of Stars, Dust, and Dark Matter Galaxies are the colossal star-cities of our universe — vast cosmic systems where stars, gas, planets, black holes, and dark matter coexist under gravity. If you're new to space science, start with our previous post What is the Universe? A Beginner's Journey into Astronomy . 🔭 What Exactly Is a Galaxy? A galaxy is a massive system bound by gravity, containing stars, interstellar gas, dust, dark matter, and often a supermassive black hole at its center. These celestial systems can range from dwarf galaxies with a few billion stars to giant ellipticals containing over a trillion stars. Galaxies are the foundational building blocks of the universe. They’re not randomly scattered — they form groups, clusters, and superclusters, shaping the large-scale structure of the cosmos. 🌌 The Milky Way — Our Home Galaxy We reside in the Milky Way Galaxy , a barred spiral gal...

🌌 What is the Universe? – A Beginner’s Journey into Astronomy Have you ever looked up at the night sky and wondered: "What exactly is all this?" That glowing band of stars, the silence of the cosmos, the vast emptiness filled with secrets—this is the Universe. But what is it really? Let’s begin our astronomical adventure to understand it, from the basics to the mysteries that baffle even the brightest scientists. Hubble Ultra Deep Field. Credit: NASA/ESA/Wikimedia Commons 🔭 Definition: What is the Universe? The Universe is everything that exists: space, time, matter, and energy . It includes the smallest atoms, the largest galaxies, the light we see, and the dark matter we don’t. It is estimated to be at least 13.8 billion years old , expanding since the moment of the Big Bang . 🌠 What Does It Contain? Galaxies: Billions of star systems like our Milky Way Stars and Planets: Including our Sun and Earth ...