Why in the News?

The article becomes relevant at the start of a new year, as it reflects on Earth’s continuous journey around the Sun at nearly 1,07,000 km per hour. It points out that even at such enormous speed, life remains stable because gravity keeps everything in balance. The piece recalls an important scientific milestone, the rejection of the ether theory in 1887, and pays tribute to Prof. Jayant Narlikar, founder of IUCAA, after his recent passing. It contrasts old beliefs about “aether” with today’s scientific understanding of vacuum and gravitational forces. The striking figures, Earth travelling nearly 1 billion kilometres in a year and about 40,000 kilometres in an hour, highlight how vast this motion is, even though we do not feel it in everyday life.

What is Gravity?

1. Gravity is a fundamental, invisible force of attraction that pulls any two objects with mass toward each other. 
2. Its strength depends on the mass of the objects and the distance between them
3. Gravity governs both terrestrial and cosmic systems. 
4. It explains falling objects, planetary motion, and Earth’s stable revolution around the Sun. 
5. The Earth completes one revolution in 365 days while travelling nearly one billion kilometres annually at high velocity. This motion remains unnoticed due to gravitational balance and absence of resistive friction in space.

How Does Gravity Function as a Centripetal Force?

1. Centripetal Mechanism: Gravity acts as the centripetal force pulling bodies towards a centre, ensuring orbital motion.
2. Bicycle Analogy: Pulling a string tied to a rotating object redirects its motion inward, similar to gravitational pull maintaining planetary orbits.
3. Planet-Sun Interaction: Earth does not fall into the Sun because forward motion balances gravitational pull.
4. Universal Application: The same mechanism explains the Earth-Moon system and other celestial rotations.

Why Do Objects Fall Toward Earth?

1. Universal Gravitation: Objects fall toward Earth because Earth is the heaviest nearby mass.
2. Mass Attraction: All objects with mass attract one another.
3. Everyday Example: Falling bodies move toward Earth’s centre unless acted upon by another force.

How Fast Is Earth Travelling in Space?

1. Annual Distance: Earth travels nearly 1,000,000,000 km in one year.
2. Hourly Speed: Approximate orbital speed equals 1,07,000 km per hour.
3. Comparative Illustration: A car travelling at 100 km per hour without stopping would take around 1,000 years to cover a comparable distance.
4. Temporal Perspective: Earth covers nearly 40,000 km in about one hour.

Why Is There No Friction in Space?

1. Friction Concept: Friction arises due to surrounding particles resisting motion.
2. Earthly Examples: Air slows a bird; water resists a fish; road friction stops a car.
3. Vacuum Condition: Space lacks resisting medium, preventing deceleration of planetary motion.
4. Energy Continuity: Continuous motion persists without need for refuelling unlike vehicles requiring oil.

What Was the Ether Hypothesis and Why Did It Fail?

1. Ether Assumption: Earlier belief held that an invisible material called “aether” filled space.
2. Michelson-Morley Experiment (1887): Attempted to detect ether; failed to find evidence.
3. Scientific Outcome: Demonstrated absence of ether, marking a major conceptual correction.
4. Modern Understanding: Space functions as vacuum without a resistive medium.

What Is the Significance of Space Studies in India?

1. Institutional Role: IUCAA in Pune advances astrophysics research.
2. Scientific Leadership: Prof. Jayant Narlikar contributed to cosmological theories and public science communication.
3. Recognition: Awarded Padma Vibhushan in 2004.
4. Public Outreach: Science communication through television series such as “Brahmand.”

Conclusion

Earth’s silent, high-speed journey through space is sustained by the precise balance of gravity and motion. What once required speculative ideas like “ether” is now explained through tested scientific principles. By reflecting on these discoveries, and the contributions of scientists like Jayant Narlikar, it reinforces the importance of scientific temper in understanding our place in the universe.

PYQ Relevance

[UPSC 2017] How does the Juno Mission of NASA help to understand the origin and evolution of earth?

Linkage: Juno’s study of Jupiter’s gravitational structure reinforces the article’s explanation of gravity as the fundamental force shaping Earth’s origin and sustaining its motion through space.

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