Theory:

     Duttada could not share his anxieties with anyone around him. He had to participate in and outwardly enjoy the Puja ceremonies, the Diwali celebration and other festivals. His sole daytime relaxation was in the company of Khoka, his eight-year-old grandson, and of course at night looking through Dibya.
 
     He was regularly monitoring the comet, now clearly visible even to the naked eye. On November 18 a special messenger on a scooter from the British Council brought in an urgent telex message for him. The telex operator in Calcutta had wondered what was so special about it to make it so urgent. But on reading it Duttada lost all his lethargy and rushed to his favourite rasagolla shop. The message read:
 
     “I am confident now of buying my Christmas presents on December 15 — John Macpherson.”
Explanation:
 
Despite the fact that Duttada's mind was filled with numerous questions and he was worried about the results of Project Light Brigade, he was in a situation where he couldn't express his worries with anybody since the Project's details were to be kept secret. He was forced to participate in Puja ceremonies, Diwali festivities, and other holidays, which he seemed to enjoy despite the fact he did not. Generally, in the month of October, Hindu festivals such as Durga Puja, Navaratri, Dussehra, Ekadashi, Pradosh Vrat, Purnima Puja, and others will be held across India, followed by Diwali in the first week of November.
 
Spending time with Khoka, his eight-year-old grandson was his only source of daily relaxation. The name 'Khoka' means 'baby' in the Bengali language. Duttada looked through Dibya at night to check on Comet Dutta's progress.
 
Duttada observing stars.jpg
Duttada - observing Comet Dutta's progress
 
Duttada kept a close eye on the comet through his eight-inch Dibya telescope, and he was quite concerned about the outcome of the spacecraft deployed to deflect Comet Dutta. After some days, Comet Dutta became visible to the human eye, letting ordinary people observe it.
 
On November 18, Duttada received an urgent telex message from the British Council through a special messenger. The telex operator in Calcutta had no idea why it was so urgent. After reading it, Duttada lost all sluggishness and raced to his favourite rasagolla shop. The reason for it was that John Macpherson had stated in that message that he was so confident in buying Christmas gifts on December 15th. It indicates that the Project Light Brigade's attempt to deflect Comet Dutta via nuclear explosion was successful. As a result, there was no chance that Comet Dutta would collide with the Earth on December 15th. Duttada was overjoyed and purchased sweets as a result of it.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Lethargy The state of having no energy or zest for doing things
2.
SoleOnly or single
Reference:
National Council of Educational Research and Training (2008). The Comet - II — JAYANT NARLIKAR (pp. 81-87). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.