Nuclear-powered submarines are equipped with nuclear reactors that allow them to remain submerged for extended periods, as they do not need to surface frequently for air or fuel.

Air Independent Propulsion system

• AIP is a technology for conventional non-nuclear submarines.
• Submarines are essentially of two types: conventional and nuclear.
• The conventional submarines use diesel-electric engines, which require them to surface almost daily to get atmospheric oxygen for fuel combustion.
• Advantages of AIP system:
  • It allows the submarines to stay for longer hours in the water.
  • It decreases the noise levels made by the submarines. This makes it hard to detect the submarines.
• AIP is mostly implemented as an auxiliary source, with the traditional diesel engine handling surface propulsion.
• AIP technology can be installed on existing, older-generation submarines by inserting a new hull section during a retrofit.
• Types of AIP: Open-cycle systems, Closed-cycle diesel engines, Closed-cycle steam turbines Stirling cycle engines and Fuel cells.

• Defence Research and Development Organisation (DRDO) has indigenously developed an Fuel Cell Based  Air- Independent Propulsion (AIP) system.
• In a fuel cell based AIP, an electrolytic fuel cell releases energy by combining hydrogen and oxygen, with only water as the waste product ensuring less marine pollution.
• The cells are highly efficient, and do not have moving parts, thus ensuring that the submarine has a low acoustic emission of sound.

Nuclear-Powered Ballistic Missile Submarine (SSBN)

• Features:
  • Nuclear propulsion: SSBNs are powered by nuclear reactors, enabling them to stay submerged for long durations without surfacing, limited only by food supplies and maintenance.
  • Ballistic missile capability: They are equipped with submarine-launched ballistic missiles (SLBMs), allowing them to serve as a platform for nuclear deterrence with a second-strike capability.
  • Stealth: The submarines are designed for stealth, reducing their detection by enemy forces, making them a key asset for strategic deterrence.

• Recently, India launched its fourth nuclear-powered ballistic missile submarine (SSBN) at the Ship Building Center (SBC) in Visakhapatnam, enhancing its nuclear deterrence capabilities.
• The fourth SSBN is codenamed S4*.
• It boasts nearly 75 percent indigenous content and is equipped with K-4 ballistic missiles, which have a range of 3,500 km and are fired through vertical launching systems.
• While the first of its class, INS Arihant carries750 km range K-15 nuclear missiles, its successors, INS Arighaat and INS Aridhaman, are all upgrades of the previous ones and carry only K-4 ballistic missiles. 

The 4 km-long Kartarpur Corridor provides visa-free access to Indian Sikh pilgrims to visit Gurdwara Darbar Sahib, the final resting place of Sikhism founder Guru Nanak Dev.

Additional Information

• • Kartarpur marks the most significant and constructive phase in the life of Guru Nanak Dev. It was here on the banks of the river Ravi that he laid the foundations of a new faith in a commune he set up. 
  • Guru Nanak Dev finally came to Kartarpur rich with experiences gained from his interactions with rulers, common people, clergymen, and thinkers. 
    • The janam sakhis on Guru Nanak’s life say he was offered this piece of land by a ‘karori’ (administrator of a pargana) who was initially against him, but subsequently became his disciple.
    • Guru Nanak called it Kartarpur, and started living here with his parents, wife Mata Sulakhni, and two sons, Sri Chand and Lakshmi Chand, thus demonstrating that he preferred the life of a householder to that of an ascetic.
  • Guru Nanak believed the supreme purpose of human life is to gain enlightenment or a state of union with God. It was at Kartarpur that he taught his followers the way to liberation by practising it.
  • At Kartarpur, Guru Nanak practised what he preached—“naam japo, kirrt karo, wand chhako (worship, work, and share)” — as the path to liberation.
  • He and his followers cultivated the land at Kartarpur, and also reared cattle. As per the janam sakhis, Guru Nanak used to bring his cattle to graze at the well of Ranjita Randhawa, a landlord at Pakhoke Randhawa, now called Dera Baba Nanak from where the Kartarpur Corridor starts, a few kilometres from Kartarpur.
  • Nanak believed in the importance of singing the praises of God as a way to gain liberation. 
    • He set up a ‘dharamsal’ (a place where dharma or merit is earned) at Kartarpur, where he and his followers would sing his compositions in the morning and evening.
  • It was at Kartarpur that Nanak started the concept of ‘langar’, a community meal prepared in a community kitchen where everyone would sit on the floor and eat together regardless of their social background.
  • The distinctive feature of SIkh identity — Service before Self — was formulated by Guru Nanak at Kartarpur. Nanak preached that every human being, regardless of his family, caste, creed or gender, can attain liberation by following the three principles of work, worship and sharing. His programme was of universal liberation and redemption.
  • “It was at Kartarpur that Nanak gave the three Gs — Gurdwara, the Granth, and the Guru himself — that underpin the Sikh faith
• The Guru-disciple tradition

• • It was at Kartarpur that Nanak chose his successor, Angad Dev. 

Bioluminescence 

• Bioluminescence is light produced by a chemical reaction within a living organism. Bioluminescence is a type of chemiluminescence, which is simply the term for a chemical reaction where light is produced. (Bioluminescence is chemiluminescence that takes place inside a living organism.)
• Most bioluminescent organisms are found in the ocean. These bioluminescent marine species include fish, bacteria, and jellies. Some bioluminescent organisms, including fireflies and fungi, are found on land. There are almost no bioluminescent organisms native to freshwater habitats.
• The chemical reaction that results in bioluminescence requires two unique chemicals: luciferin and either luciferase or photoprotein. Luciferin is the compound that actually produces light.
• The bioluminescent color (yellow in fireflies, greenish in lanternfish) is a result of the arrangement of luciferin molecules.
• Some bioluminescent organisms produce (synthesize) luciferin on their own. Dinoflagellates, for instance, bioluminesce in a bluish-green color. 
• Some bioluminescent organisms do not synthesize luciferin. Instead, they absorb it through other organisms, either as food or in a symbiotic relationship.
• The appearance of bioluminescent light varies greatly, depending on the habitat and organism in which it is found.
• Most marine bioluminescence, for instance, is expressed in the blue-green part of the visible light spectrum. These colors are more easily visible in the deep ocean. Also, most marine organisms are sensitive only to blue-green colors. They are physically unable to process yellow, red, or violet colors.
• Most land organisms also exhibit blue-green bioluminescence
• Few organisms can glow in more than one color. The so-called railroad worm (actually the larva of a beetle) may be the most familiar.
• Some organisms emit light continuously. Some species of fungi present in decaying wood, for instance, emit a fairly consistent glow, called foxfire.
• Bioluminescence is used by living things to hunt prey, defend against predators, find mates, and execute other vital activities.

• Bioluminescence is not the same thing as fluorescence, however. Florescence does not involve a chemical reaction. In fluorescence, a stimulating light is absorbed and re-emitted. The fluorescing light is only visible in the presence of the stimulating light.

• Most scientists point to two reasons why so few freshwater organisms exhibit bioluminescence.
  • First, freshwater habitats have not been around as long as marine habitats—evolution is a slow process and freshwater habitats do not yet have the biodiversity of oceans.

• Second, freshwater species wouldn’t really benefit from bioluminescence. Freshwater habitats are often murkier, and deepwater species use other adaptations (such as a catfish’s sensitive “whiskers”) to hunt and defend in the environment.

This money has to increase to at least $30 billion every year by 2030.

Kunming-Montreal Global Biodiversity Framework

• • The Kunming-Montreal Global Biodiversity Framework that was concluded at COP15 in Montreal in 2022, lays down four goals and 23 targets to be achieved collectively by 2030.
• Legal nature

• • The GBF is not an international treaty and is therefore not legally binding on Parties.
  • It also doesn’t require a mandatory system that forces parties to step up their efforts at a specific time.

What are the Key Targets of the GBF?

• 30×30 Deal:
  • Restore 30% degraded ecosystems globally (on land and sea) by 2030
  • Conserve and manage 30% areas (terrestrial, inland water, and coastal and marine) by 2030
• Stop the extinction of known species, and by 2050 reduce tenfold the extinction risk and rate of all species (including unknown)
• Reduce risk from pesticides by at least 50% by 2030
• Reduce nutrients lost to the environment by at least 50% by 2030
• Reduce pollution risks and negative impacts of pollution from all sources by 2030 to levels that are not harmful to biodiversity and ecosystem functions
• Reduce global footprint of consumption by 2030, including through significantly reducing overconsumption and waste generation and halving food waste
• Sustainably manage areas under agriculture, aquaculture, fisheries, and forestry and substantially increase agroecology and other biodiversity-friendly practices
• Tackle climate change through nature-based solutions
• Reduce the rate of introduction and establishment of invasive alien species by at least 50% by 2030
• Secure the safe, legal and sustainable use and trade of wild species by 2030
• Green up urban spaces

                                                                                Most asteroids reside in a dense belt between Mars and Jupiter. The asteroid belt itself consists of millions of asteroids swept around and marshalled by the gravitational force of Jupiter.

Additional Information

• Meteoroids: These rocks still are in space. Meteoroids range in size from dust grains to small asteroids.
• Meteors: When meteoroids enter Earth’s atmosphere, or that of another planet, at high speed and burn up, they’re called meteors. This is also when we refer to them as “shooting stars.” Sometimes meteors can even appear brighter than Venus – that’s when we call them “fireballs.”
• Meteorites: When a meteoroid survives a trip through the atmosphere and hits the ground, it’s called a meteorite.
  • Most meteorites found on Earth come from shattered asteroids, although some come from Mars or the Moon. In theory, small pieces of Mercury or Venus could have also reached Earth, but none have been conclusively identified
  • They are commonly designated as three types: stony meteorites, iron meteorites, and stony-iron meteorites..