In the history of Indian science and technology, what important landmark event took place on 21 November 1963?

Introduction / Context:
This question belongs to general science and modern Indian history. It asks you to remember a specific date related to the beginning of the Indian space programme and to distinguish it from other important milestones like satellite launches, nuclear tests and institutional formation.

Given Data / Assumptions:
• The date is 21 November 1963.
• The event is described as a landmark in science and technology for India.
• Options mention rockets, satellites, nuclear tests, power plants and organisational changes.

Concept / Approach:
On 21 November 1963, India launched its first sounding rocket from the Thumba Equatorial Rocket Launching Station near Thiruvananthapuram. This event is widely recognised as the formal beginning of the Indian space programme. The first Indian satellite Aryabhata was launched later, in 1975. The Pokhran nuclear test took place in 1974, and the Indian Space Research Organisation was established as a separate entity in 1969. The Tarapur nuclear power plant was commissioned in the late 1960s. Therefore, only the rocket launch from Thumba matches the date given in the question.

Step-by-Step Solution:
Step 1: Match the given date, 21 November 1963, with known events in Indian science. Step 2: Recall that this date is associated with the first sounding rocket launch from Thumba Equatorial Rocket Launching Station. Step 3: Check the dates of other events. Aryabhata satellite was launched more than a decade later, not in 1963. Step 4: Recognise that the Pokhran nuclear test and Tarapur power plant commissioning also occurred in later years. Step 5: Conclude that the correct answer is the first rocket launch from Thumba, marking the start of space research.

Verification / Alternative check:
Historical summaries of the Indian space programme consistently highlight the 1963 Thumba rocket launch as the starting point of organised space research in India. Timelines show other milestones, such as the formation of ISRO and satellite launches, occurring after this date, confirming the uniqueness of the 1963 rocket launch as the relevant landmark.

Why Other Options Are Wrong:
First underground nuclear test at Pokhran: Conducted in 1974, known as Operation Smiling Buddha, not in 1963.
Launch of the first Indian satellite Aryabhata: Happened in 1975, not in 1963.
Commissioning of the first nuclear power plant at Tarapur: Tarapur Atomic Power Station began commercial operation later in the 1960s, not specifically on 21 November 1963.
Formal establishment of the Indian Space Research Organisation: ISRO was formed in 1969, several years after the Thumba rocket launch.

Common Pitfalls:
Students often mix up dates of different scientific achievements, especially between space and nuclear milestones. The key memory aid here is that small sounding rocket launches from Thumba marked the beginning of space efforts in the early 1960s, while heavy satellite launches and nuclear tests came later. Keeping a basic chronological order of these events helps to avoid confusion in exam questions that focus on specific dates.

Final Answer:
On 21 November 1963, India achieved the landmark of launching the first rocket from the Thumba Equatorial Rocket Launching Station, marking the start of its space research programme.