🌏 The Earth is not just the home of humans (मनुष्य)
👉 It is the abode (निवास स्थान) of all living (जीवित) and non-living (निर्जीव) things too!
💚 From tiny insects 🐜 to massive mountains 🏔️ – everything exists on Earth.
How did the Earth originate? 🤔
🔬 This question has always puzzled (उलझन में डाला है) scientists.
🌌 To understand the Earth, we must first know how the universe (ब्रह्मांड) and all celestial bodies (आकाशीय पिंड) came into existence.
📖 This chapter gives a brief (संक्षिप्त) yet fascinating description of the origin process.
Development Stage of the Earth 🌍🔥
🪨 In the beginning, Earth was:
•Rocky (पथरीली)
•Extremely hot (बहुत गर्म)
•Deserted (निर्जन)
🌫️ Its atmosphere (वायुमंडल) was very thin — mainly made of hydrogen (हाइड्रोजन) and helium (हीलियम) gases.
Earth Began to Transform 🌦️🌱
🌀 Over time, many natural events (घटनाएँ) took place...
🌍 Slowly the Earth turned beautiful (सुंदर) and suitable (अनुकूल) for:
💧 Water
🌿 Life
🌟 These changes made Earth a habitable planet (रहने योग्य ग्रह)!
Life on Earth 🌱⏳
🧬 Life evolved about 460 million years ago (लगभग 460 करोड़ साल पहले)
🔍 Earth’s structure became layered (परतदार):
From the outer atmosphere (वायुमंडल)
To the deep core (गर्भ) — all layers are different in composition.
🪨 The lithosphere (स्थलमंडल) and 🌫️ atmosphere formed later.
🌱 The origin of life (जीवन की उत्पत्ति) occurred during the final stage of Earth’s formation
Development of Atmosphere on Earth 🌫️🌍
🌬️ The development of Earth’s atmosphere happened in 3 main stages:
1️⃣ First Stage:
☀️ Due to solar wind (सौर हवा), light gases like hydrogen (हाइड्रोजन) and helium (हीलियम) were blown away from Earth.
2️⃣ Second Stage:
🌡️ As the Earth cooled (ठंडी हुई) and went through differentiation (परतों में विभाजन), gases came out from inside:
💨 water vapour (जल वाष्प), nitrogen (नाइट्रोजन), carbon dioxide (कार्बन डाइऑक्साइड), methane (मीथेन), and ammonia (अमोनिया) – but very little oxygen (ऑक्सीजन) was present.
3️⃣ Third Stage:
🌋 Continuous volcanic eruptions (ज्वालामुखी विस्फोट) released more vapour and gases.
💧 Water vapour condensed (संघनित हुआ) into rain 🌧️ → oceans 🌊 formed → life 🌱 began.
🌿 With the rise of photosynthesis (प्रकाश संश्लेषण), oxygen levels increased in the atmosphere 🌬️.
Initial Concepts of Earth’s Origin 🌍✨
📜 Some ancient theories (प्राचीन सिद्धांत) about how Earth formed:
🌫️ Nebula Hypothesis (ग्रहांडीय नीहारिका सिद्धांत) – by Immanuel Kant
🌀 Planets formed from a rotating cloud of gas (घूमती हुई गैसों की बादल) and dust.
🔧 Laplace's Improvement:
🌪️ As the angular momentum (कोणीय संवेग) increased, the nebula compressed (संपीड़ित हुई) and its outer parts formed rings (छल्ले) → which became planets (ग्रह).
🌟 Chamberlain and Molton's Theory:
🌠 A fast-moving star passed near the Sun.
🌞 Its gravitational force (गुरुत्वाकर्षण बल) pulled out a cigar-shaped (सिगार-आकार का) piece from the Sun’s surface →
🪐 This piece later turned into planets!
Division of Earth’s Geo-scientific Chronology 🌍🧪
📊 Earth’s geological time scale (भूवैज्ञानिक समयक्रम) is divided into:
🔹 Eon (Ian – आयन) – Largest
🔹 Era (Mahakalpa – महाकल्प)
🔹 Period (कल्प)
🔹 Epoch (Yug – युग) – Smallest
🕰️ From Earth’s origin till now, its history is grouped into 4 major Eons (चार प्रमुख आयन).
🌀 The current Eon is called Phanerozoic Eon (प्रकटजीवी आयन).
📘 This Eon is divided into 3 Eras (महाकल्प):
1️⃣ Paleozoic Era (पुराजीवी महाकल्प)
2️⃣ Mesozoic Era (मध्यजीवी महाकल्प)
3️⃣ Cenozoic Era (नवजीवी महाकल्प)
📆 These Eras are further divided into Periods (कल्प) and Epochs (युग).
Key Terms + Age of Earth 🪐⏳
❇️ Nebula (नीहारिका) –
A rotating cloud (घूमता हुआ बादल) of gas, dust, and
other substances 🌫️
💭 It is believed that planets formed from such nebulae.
🪐 Asteroids (उल्का-पिंड) –
A band of millions of small bodies (लाखों छोटे खगोलीय पिंडों का पट्टा)
📍 Found between the terrestrial planets (पृथ्वी जैसे ग्रह) and the outer planets (बाहरी ग्रह) in the solar system.
🧠 How old is the Earth?
🌍 Earth is approximately 4.6 billion years old (4.6 अरब वर्ष पुरानी)!
Big Bang Theory 🌌💥
🧠 The Big Bang Theory (बिग बैंग सिद्धांत) is the most widely accepted explanation for the origin of the universe (ब्रह्मांड की उत्पत्ति).
🌀 According to it, the universe developed in 3 main stages:
1️⃣ All the matter (पदार्थ) in the universe was once packed in a tiny atom (सूक्ष्म परमाणु) with:
•Extremely high density (अत्यधिक घनत्व)
•Very small volume (बहुत छोटा आकार)
•
2️⃣ Due to too much energy (ऊर्जा) in it, the atom exploded (विस्फोट हुआ)
⏱️ And the universe began to expand (फैलना शुरू हुआ) — all within a second!
3️⃣ After about 3 million years (30 लाख साल), the temperature dropped (तापमान गिरा) to 4500° Kelvin
🌡️ → and atomic particles (परमाणु कण) started forming.
Formation of Planets 🪐✨
🌌 Scientists believe that planet formation (ग्रहों की संरचना) happened in 3 main stages:
1️⃣ Initial Stage:
⭐ Planets formed from stars (तारों).
💫 A core (केंद्र) developed due to gravity (गुरुत्वाकर्षण)
🌪️ Around it, a swirling disc (घूमती हुई थाली) of gas and dust formed.
2️⃣ Middle Stage:
☁️ The gaseous cloud (गैसीय बादल) began to condense (संघनित होना)
🟠 Around the core, small spherical bodies (गोल पिंड) formed — called planets (ग्रह).
3️⃣ Final Stage:
🧲 Due to increasing gravitational force (गुरुत्वीय बल), these planets stuck together
🌍 Forming larger bodies (बड़े खगोलीय पिंड) – the final shape of planets!
Terrestrial vs. Jovian Planets 🪐🌍
🔭 Scientists classify planets into two main types:
🌍 Terrestrial Planets (पृथ्वी जैसे ग्रह)
🟢 Mercury, Venus, Earth, Mars
•Closer to the parent star (मुख्य तारा)
•🌡️ Too hot (गर्म) — gases couldn’t condense (संघनित नहीं हो सकीं)
