Science: A Never-Ending Journey

   

In previous chapters^[1], we discussed various aspects of the nature of science: the pursuit and accumulation of objective knowledge, the harmony between theory and observation, the emergence of new questions, and the efforts to resolve them consistently within an established framework. To illustrate these principles, several examples of scientific inquiry were highlighted across different contexts. In this chapter, we focus on a few fundamental queries to demonstrate how science perpetually seeks knowledge, answers questions, and enriches its base with new observations. This dynamic quality is precisely what distinguishes science from other epistemological traditions.

 

In recent years, a section of scholars and intellectuals has frequently engaged in a form of "treasure hunting"—attempting to locate established scientific theories within religious scriptures and philosophical texts such as the Vedas, Upanishads, Quran, and Bible, often in an effort to shield these traditions from modern scrutiny. For instance, a scholar might claim to have discovered Einstein’s theory of relativity within the Vedas or Upanishads, drawing on scholarly prowess to connect the metaphysical phrasing of a Sanskrit verse to the equivalence of mass and energy. Yet, such claims routinely ignore a simple, essential question: what followed this supposed ancient discovery? Why did such a profound realization thousands of years ago not lead to a systematic description of the material world as we know it today? Why, instead, was it followed by cosmologies centered on heavens and hells? Undeterred, these proponents rarely make a genuine effort to answer this critique. Instead, they retreat into arguments about the obscurity of ancient texts and reiterate an unwavering faith that scientific truths lie hidden within the labyrinth of ancient wisdom. Attempts to retroactively reinterpret ancient mantras to fit modern scientific contexts ultimately result in intellectual hooliganism.

 

In contrast to static views of ancient wisdom, the scientific pursuit of understanding the material world is a continuous, never-ending journey. To illustrate this, we examine how science has progressed in addressing fundamental questions over the past two decades. As established in earlier chapters, science expands its knowledge base through empirical experimentation and real-world evidence. Any newly acquired insight must align with established scientific theories; if it does not, it signals the need for deeper investigation and highlights the limitations of existing frameworks. Below are examples from recent decades where previously unsolved problems were fully or partially resolved—sometimes offering tangible evidence for a theoretical model, and at other times providing decisive support for one side of an ongoing debate.

 

 

 

Gravitational Wave and Higgs Boson

 

To date, scientific research has identified four fundamental forces operating in nature: the gravitational force, the electromagnetic force, the weak nuclear force, and the strong nuclear force.

 

• Gravitational Force: The universal force of mutual attraction between any two objects with mass.
• Electromagnetic Force: The force of mutual attraction or repulsion between electrically charged particles. Although magnetism and electricity were initially regarded as distinct phenomena, physicists later unified them upon realizing they are manifestations of a single underlying interaction—hence the term electromagnetic force. Moving electric charges generate magnetic fields, demonstrating their intrinsic link.
• Weak Nuclear Force: An interaction responsible for subatomic decay processes within the atomic nucleus. For instance, during certain interactions—such as when a neutrino interacts closely with a neutron—the weak force mediates the transformation of the neutron into a proton, emitting an electron and an antineutrino in the process.
• Strong Nuclear Force: The powerful short-range force that binds protons and neutrons together inside the nucleus, overcoming the strong electrostatic repulsion between positively charged protons.

However, physicists believe that the actions of all four fundamental forces might ultimately be explained through a single, unified theory. Albert Einstein (1879-1955) devoted much of his later life to pursuing this goal, drawing the attention of the broader scientific community to the problem. Through his theory of general relativity, he demonstrated that the trajectories of planets and stars under the influence of gravity are dictated by the curvature of four-dimensional spacetime—a continuum combining three dimensions of space with one of time.

 

Einstein sought to extend this geometric framework to account for electromagnetism, but his efforts were ultimately unsuccessful. Electromagnetism was instead successfully explained within the framework of quantum mechanics—a field Einstein himself helped pioneer. Indeed, in explaining the photoelectric effect[2]—a key manifestation of the electromagnetic interaction—he proposed that light consists of discrete energy packets (photons) whose absorption causes the emission of electrons from material surfaces. To this day, a complete synthesis of general relativity and quantum theory remains elusive. Consequently, gravity has yet to be reconciled within the same theoretical framework that accounts for the other fundamental forces.

 

A major limitation of Newtonian mechanics is its assumption of instantaneous action-at-a-distance. According to Einstein’s special theory of relativity, no physical object or signal can travel faster than the speed of light in a vacuum. Consequently, forces cannot act instantaneously across a spatial separation—a conceptual flaw that rendered the classical Newtonian model untenable in modern physics. To resolve this issue regarding gravity, Einstein introduced the concept of gravitational waves through his theory of general relativity. He demonstrated that when two massive bodies, such as a binary system of dense stars or black holes, orbit closely and accelerate around each other, they generate ripples in the fabric of spacetime. These ripples—gravitational waves—propagate outward in all directions at the speed of light, carrying energy away from the system and causing the orbiting bodies to gradually lose mass-energy and coalesce. Although Einstein mathematically predicted the existence of gravitational waves during such catastrophic cosmic events, he remained skeptical about whether these extremely weak disturbances could ever be experimentally detected.

 

Einstein’s prediction of gravitational waves first gained strong indirect support in 1974, when Russell A. Hulse (1950 - ) and Joseph H. Taylor Jr. (1941 - ) discovered that the decaying orbit of a binary pulsar matched the energy loss expected from gravitational radiation—an achievement that earned them the 1993 Nobel Prize in Physics. However, direct observation remained extraordinarily difficult due to two main hurdles: the extreme weakness of the waves by the time they reach Earth and the unpredictability of the cosmic events that generate them.

 

To capture these minuscule ripples in spacetime, scientists built the Laser Interferometer Gravitational-Wave Observatory (LIGO) across two locations in the United States: Livingston, Louisiana, and Hanford (near Richland), Washington, separated by 3,002 kilometers. At each facility, a laser beam is split down two perpendicular 4-kilometer arms. By analyzing the interference pattern when the beams recombine, LIGO can measure path-length changes as tiny as one-thousandth the diameter of a proton. Operating two distant stations allowed researchers to confirm genuine cosmic signals occurring simultaneously at both sites while filtering out localized terrestrial noise.

 

Initial observations between 2002 and 2010 yielded no detections. After several years of technical overhauls, the upgraded system—Advanced LIGO—came online in 2015. On September 14, 2015, both detectors simultaneously recorded a signal. General Relativity calculations confirmed that the wave was produced by the merger of two black holes with masses approximately 36 and 29 times that of the Sun.

 

Following months of rigorous verification and data analysis, scientists officially announced the direct detection of gravitational waves on February 11, 2016, conclusively validating Einstein's century-old theory. In 2017, Rainer Weiss (1932-2025), Barry Barish (1936 - ), and Kip Thorne (1940 - ) were awarded the Nobel Prize in Physics for their decisive contributions to the LIGO detector and the historic discovery.

 

Beyond describing fundamental forces through wave propagation, modern physics also theorizes force mediation through particle exchange. For gravity, this hypothetical quantum mediator is known as the graviton. However, while gravitational waves have now been directly observed, their individual particle nature remains unverified. Much like a unified theory bridging general relativity and quantum mechanics remains elusive, the graviton itself has yet to be experimentally confirmed in the laboratory.

 

Unlike gravity, the particle-exchange theory for the remaining three fundamental forces is supported by extensive experimental evidence:

• Electromagnetic Force: Mediated by photons.
• Strong Nuclear Force: Mediated by gluons.
• Weak Nuclear Force: Mediated by W+, W-, and Z0 bosons.

Because these force-mediating particles obey Bose-Einstein statistics and possess integer quantum spin (0, 1, or 2), they are classified as bosons.

 

In contrast, the building blocks of matter—which form electrons as well as the protons and neutrons inside atomic nuclei—obey Fermi-Dirac statistics and possess half-integer quantum spin. Known as fermions, these elementary particles are categorized into quarks and leptons:

• Quarks: Combine to form composite particles called hadrons. Up quarks carry a fractional electric charge of +2/3, while down quarks carry -1/3. A proton consists of two up quarks and one down quark, resulting in a net charge of +1 (equal and opposite to the electron). A neutron consists of one up quark and two down quarks, producing a net charge of 0.
• Leptons: Include fundamental particles such as the electron, which carries a unit negative charge and orbits the nucleus.

Together, force-carrying bosons and structural fermions form the core architecture of the Standard Model of particle physics, which accounts for 17 fundamental particles (along with their corresponding antiparticles) categorized by their physical properties:

• Fermions (12): 6 quarks and 6 leptons, which constitute the matter of the universe.
• Gauge Bosons (4): The photon, gluon, W boson, and Z boson, which mediate force interactions.
• Scalar Boson (1): The Higgs boson, which plays a unique role in mass generation.

The Higgs boson holds a special place in this framework. In 1964, Peter Higgs (1929-2024) and several other theoretical physicists proposed that elementary particles acquire mass through their interactions with an all-pervading quantum field—the Higgs field. The quantum excitation of this field corresponds to the Higgs boson.

 

Building on broader research into spontaneous symmetry breaking (including work by Jeffrey Goldstone (1933 - ), physicists Sheldon Glashow (1932 -), Steven Weinberg (1933 -2021), and Abdus Salam (1926 – 1996) incorporated the Higgs mechanism to show that the electromagnetic and weak nuclear forces are two manifestations of a single, unified electroweak force at high energies. For establishing this foundational unification, Glashow, Weinberg, and Salam were awarded the 1979 Nobel Prize in Physics.

 

Although theoretically essential for explaining how fundamental particles acquire mass, the Higgs boson remained undiscovered for decades, making it the last unverified particle of the Standard Model. Confirming its existence required an extraordinary leap in technological engineering and global scientific collaboration.

 

Beginning in the 1980s, international efforts spearheaded by CERN (the European Organization for Nuclear Research) set out to build particle accelerators capable of accelerating subatomic particles to high energies and smashing them head-on. Thousands of scientists from hundreds of laboratories worldwide—including research teams from India—joined this historic endeavor.

 

The platform of this search was the Large Hadron Collider (LHC) near Geneva, Switzerland. Constructed over ten years, the LHC was installed inside a circular, 26.7-kilometer underground tunnel buried 50 to 175 meters beneath the Franco-Swiss border—originally excavated between 1983 and 1988 for the Large Electron-Positron Collider (LEP). Following technical upgrades, the LHC began high-energy collision experiments in 2010 to search for physical evidence of the Higgs boson.

 

Nearly four decades of collective international research culminated in rapid breakthrough milestones:

• July 4, 2012: CERN announced the discovery of a new particle consistent with the predicted Higgs boson.
• March 2013: After rigorous analysis of its mass, electric charge, zero quantum spin, and decay signatures, scientists officially confirmed the particle as the Higgs boson.
• October 2013: Peter Higgs and François Englert (1932-2026) were awarded the Nobel Prize in Physics for their theoretical prediction of the mass-generation mechanism.

The discovery stands as a monument to the scientific method, proving the power of large-scale international collaboration to verify the fundamental laws governing the material universe.

 

Black Hole

 

The theoretical possibility of black holes emerged shortly after Albert Einstein published his general theory of relativity. In 1916, German physicist and astronomer Karl Schwarzschild (1873-1916) derived the first exact solution to Einstein's field equations. He demonstrated that if matter were compressed to an extreme density, its gravitational field would warp spacetime geometry to create a gravitational singularity.

 

Within a region surrounding this singularity—the event horizon—the gravitational pull is so extreme that no particle, not even light, can escape. Because these cosmic objects emit no light, they came to be known as black holes, making direct optical observation impossible.

 

Although Einstein acknowledged Schwarzschild's mathematical solution, he remained skeptical of its physical reality. He believed that natural mechanisms would always intervene to prevent matter from collapsing into such an extreme state, concluding that black holes were merely fascinating artifacts of mathematical logic rather than entities that could exist in the physical universe.

 

Over time, observational evidence transformed black holes from theoretical curiosities into confirmed astronomical phenomena. In 1967, Jocelyn Bell Burnell’s (1943  - )  discovery of pulsars (rapidly spinning neutron stars) proved that matter could indeed collapse into ultradense states. Shortly after, in 1971, astronomers identified Cygnus X-1—a strong X-ray source in a binary star system—as the first widely accepted stellar-mass black hole candidate.

 

These discoveries reinforced the model of stellar evolution: when a massive star exhausts its nuclear fuel, its core collapses under its own gravity. While nothing—not even light—can escape once inside the boundary known as the event horizon, black holes can still be detected through their indirect gravitational and energetic effects on surrounding matter.

 

Astronomers identify black holes through several key phenomena:

• Accretion Disks and Quasars: As infalling matter spirals inward toward the event horizon, intense gravitational friction heats the gas into a superheated ring—an accretion disk—that emits bright X-ray and ultraviolet radiation. In the early universe, supermassive black holes feeding on vast amounts of gas created extremely luminous energetic beacons known as quasars.
• Orbital Dynamics: By tracking the high-speed orbits of visible stars moving around an invisible point, scientists can calculate the mass and location of the central compact object.
• Tidal Disruption Events: When a black hole gravitationally pulls apart a nearby star, the stream of consumed matter flares brightly across the spectrum, revealing the location of the black hole.

Today, observations indicate that supermassive black holes reside at the center of nearly every galaxy[3].

 

Science requires empirical evidence before accepting theoretical models as objective truth. Despite compelling indirect support for black holes, capturing direct observational proof remained a crucial goal. To overcome the extreme distance and tiny angular size of these cosmic targets—which render them invisible to standard radio telescopes—an international collaboration established the Event Horizon Telescope (EHT).

 

By linking eight high-altitude radio observatories across six mountain sites on four continents using Very Long Baseline Interferometry (VLBI), the EHT synthesized a virtual telescope with an effective aperture as large as Earth itself, achieving the unprecedented resolution required to resolve a black hole shadow.

 

In April 2017, the EHT targeted M87*, a supermassive black hole at the center of the galaxy Messier 87 in the Virgo cluster. Following two years of intensive computational data analysis and digital image reconstruction, the team officially unveiled the historic image on April 10, 2019.

 

The image revealed a dark central region—the black hole shadow bounded by the event horizon—encircled by a bright ring of emission. Asymmetric brightness caused by Doppler beaming confirmed that the surrounding superheated material was orbiting the black hole in a clockwise motion.

 

This milestone provided direct observational proof of black holes, validating General Relativity in the universe's most extreme gravitational field and achieving a level of direct confirmation that Einstein himself doubted would ever be possible.

 

Exoplanet

 

Humanity has long pondered whether Earth is unique or if life exists elsewhere in the cosmos. For generations, Mars captivated our collective imagination, inspiring countless childhood science fiction stories. Today, that speculative fiction has yielded to scientific reality: robotic spacecraft routinely journey to the Red Planet, while sophisticated, Earth-controlled rovers actively navigate its terrain. With agencies like NASA actively planning eventual crewed missions, the fantastical myths surrounding Mars have given way to empirical exploration.

 

Yet, far from dampening enthusiasm, modern exploration has refocused scientific curiosity onto a fundamental question: whether life ever existed beyond Earth. Current research concentrates on analyzing Martian soil and rock formations for traces of ice, ancient water channels, and biosignatures that could reveal the past or present existence of primitive microbial life.

 

Beyond our solar system lies an immense cosmos filled with countless stars and galaxies, prompting a fundamental question: could life exist on a planet orbiting another star? Blockbuster films like Avatar captivated public imagination by depicting vivid, fictional alien worlds, but science carefully distinguishes imaginative speculation from empirical reality.

 

A foundational premise of modern science is the universality of physical laws—the principle that the rules governing nature operate identically across time and space. Guided by this principle, scientists hypothesize that planetary systems are common throughout the cosmos and that some must harbor conditions conducive to life, much like Earth. However, the scientific method demands rigorous empirical proof; until direct observational evidence of habitability or extraterrestrial biology is obtained, the existence of such worlds remains a compelling hypothesis rather than an established fact.

 

For decades, astronomers struggled to detect extrasolar planets (exoplanets) due to the immense difficulty of directly imaging small, dim worlds situated next to glaring host stars. Early ground-based telescopes could only spot massive gas giants orbiting far from their stars, leaving Earth-sized planets hidden from view. To overcome this limitation, scientists turned to indirect detection techniques, primarily the transit method.

 

By measuring the slight, periodic dimming of a star as an orbiting planet passes in front of its disk, astronomers can confirm the  presence of a planet and deduce key properties, including its orbital period, radius, and estimated mass.

 

To eliminate atmospheric interference and expand observational reach, space agencies deployed specialized space observatories:

 

• Kepler Space Telescope: Launched by NASA in 2009, Kepler (the space telescope) continuously monitored approximately 150,000 main-sequence stars[4] in a targeted patch of sky. By the end of its operational life in 2018, it had discovered more than 2,500 confirmed exoplanets, proving that planets are abundant throughout our galaxy.
• TESS (Transiting Exoplanet Survey Satellite): Deployed to succeed Kepler, TESS performs an all-sky survey targeting bright, nearby stars to identify prime candidates for atmospheric characterization.

Together, space- and ground-based observatories have confirmed over 5,000 exoplanets. Among these are worlds orbiting within their host star's habitable zone—the region where temperatures allow liquid water to exist on a rocky surface. Notably, in January 2020, scientists announced the discovery of TOI 700 d, the first Earth-sized exoplanet in the habitable zone discovered by TESS.

 

As observational technology advances, the search for atmospheric biosignatures and potentially habitable alien worlds continues to intensify—proving that real-world scientific discovery is every bit as captivating as science fiction.

 

Deciphering the code of Life

 

Curiosity regarding the origin and fundamental nature of life has driven human inquiry since the dawn of civilization. Ancient mythologies, religious doctrines, and early philosophical traditions attempted to address this profound mystery alongside questions about the cosmos—weaving the emergence of life into broader creation narratives of the Earth, Sun, Moon, and distant stars. In particular, early thinkers were captivated by how self-aware, creative human beings arose within the broader animal kingdom.

 

Defining life, however, remains far more elusive than characterizing inanimate matter. While non-living physical systems can be comprehensively understood in terms of mass, charge, and energy, the true essence of biological life—how inert chemical constituents organize to manifest metabolism, self-replication, and consciousness—remains one of science’s deepest frontiers.

 

The modern scientific understanding of life began to take shape in the seventeenth century, driven by pioneering advances in microscopy. In 1665, English natural philosopher Robert Hooke (1635-1703) examined thin slices of cork tissue through a compound microscope. Observing a network of tiny, porous compartments reminiscent of monastic rooms, he coined the term “cells”.

 

Inspired by Hooke’s publication Micrographia, Dutch microscopist Anton van Leeuwenhoek (1632-1723) crafted exceptionally powerful single-lens microscopes. He became the first human to observe living unicellular organisms—including bacteria, protozoa, and blood cells in droplets of water—revealing a vast, previously invisible microscopic realm.

 

By the mid-nineteenth century, these observational breakthroughs coalesced into formal biological theory:

• Foundations of Cell Theory: In 1838-39, German botanist Matthias Schleiden (1804-1881) and zoologist Theodor Schwann (1810-1882) established that all living organisms are composed of one or more cells, identifying the cell as the fundamental structural and functional unit of life.
• Cellular Origin: In 1858, German biologist Rudolf Virchow (1821-1902) expanded cell theory by demonstrating that all cells arise exclusively from the division of pre-existing cells (Omnis cellula e cellula).

Over subsequent decades, advances in staining and microscopy allowed scientists to peer inside the cell, uncovering specialized organelles—such as the nucleus and cytoplasm—and illuminating the complex structural machinery that powers life.

 

During the nineteenth century, two revolutionary frameworks transformed the scientific understanding of how life originates, diversifies, and persists on Earth: Charles Darwin's Theory of Evolution by Natural Selection and Gregor Johann Mendel's Laws of Inheritance.

 

Evolution by Natural Selection

In 1859, British naturalist Charles Darwin (1809 – 1882) published his landmark work, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Darwin proposed that complex biodiversity arises gradually from simpler ancestral forms through natural selection acting on inherited variations. Although Darwin initially faced intense opposition—particularly from religious authorities and conservative establishment thinkers—empirical evidence eventually cemented natural selection as the foundational pillar of modern evolutionary biology.

Laws of inheritance

Concurrently, Augustinian friar and scientist Gregor Johann  Mendel (1822 – 1884) unraveled the mechanism of heredity through meticulous crossbreeding experiments on pea plants (Pisum sativum) between 1856 and 1863. Mendel demonstrated that traits are passed down in discrete units (what we now know as genes) rather than blending together continuously. His key propositions and observations are as follows:

·       Discrete Units: Traits remain distinct across generations rather than merging into a blended average.

·       Dominant and Recessive Behavior: In a given trait pair, one unit may express itself externally (dominant) while another remains unexpressed (recessive).

·       Statistical Rigor: Mendel's observed offspring ratios closely matched his theoretical mathematical predictions.

Despite its brilliance, Mendel’s work was largely ignored during his lifetime, as contemporary science favored the flawed theory of blending inheritance. Darwin himself remained unaware of Mendel's findings. It was not until the turn of the twentieth century that scientists rediscovered Mendel’s laws, giving birth to modern genetics. The fusion of Darwinian evolution and Mendelian genetics established that self-replication and adaptation are the defining hallmarks of life. Reflecting this modern consensus, NASA concisely defines life as a "self-sustaining chemical system capable of undergoing Darwinian evolution."

 

In the late nineteenth and early twentieth centuries, German biologist Theodor Boveri (1862-1915) (alongside American geneticist Walter Sutton (1877-1916)) formulated the Boveri–Sutton Chromosome Theory of Inheritance. By synthesizing Mendelian genetics with microscopic observations of cell division, Boveri demonstrated that the fundamental units of heredity reside directly on chromosomes within the cell nucleus.

 

Chromosomal composition is species-specific and remains remarkably stable across healthy cells. In sexually reproducing organisms, chromosomes exist in matching pairs called homologous chromosomes. One chromosome of each pair is inherited from each parent, allowing multiple versions of a single gene (alleles) to coexist—explaining trait variations such as flower petal coloration. The number of homologous chromosomes  also varies across species. Accordingly the organisms are categorised as follows:

• Diploid: Organisms with two matching sets of chromosomes. For example, humans possess 46 chromosomes (23 pairs), while chimpanzees possess 48 (24 pairs).
• Polyploid: Organisms with more than two sets. Commercial bread wheat, for example, is hexaploid, possessing 42 total chromosomes structured as 6 sets of 7 distinct types.
• Haploid: Cells containing a single, unpaired set of chromosomes, typical of reproductive gametes and certain simple organisms.

Simple prokaryotes (such as bacteria) lack a membrane-bound nucleus and typically organize their genetic material into a single circular chromosome. In contrast, eukaryotes harbor a true nucleus containing multiple linear chromosomes—even single-celled baker's yeast possesses 16 distinct chromosomes. Crucially, chromosome count does not correlate with biological complexity or evolutionary standing. A species' chromosome tally reflects its specific evolutionary history rather than its advancement—highlighted by the fact that common garden snails possess 54 chromosomes compared to a human's 46.

 

DNA:  key components of chromosomes

Chromosomes derive their function from deoxyribonucleic acid (DNA), the organic macromolecule that encodes genetic instructions. DNA is composed of repeating structural units called nucleotides, characterized by four chemical bases: Adenine (A), Guanine (G), Thymine (T), and Cytosine (C).

 

In 1953, British researchers Francis Crick (1916-2004) and American biologist James Watson (1928-2025) proposed the structural model of DNA as a double helix. Analyzing critical X-ray diffraction images  produced by Rosalind Franklin (1920-1958) and her graduate student Raymond Gosling (1926-2015), Watson and Crick deduced that DNA resembles a twisted ladder in the following manner:

• Backbone ("Rails"): Alternating sugar and phosphate groups form two outer strands running in opposite directions (antiparallel orientation).
• Rungs: Paired nitrogenous bases link the two strands via chemical bonds following strict complementary base-pairing rules, so that Adenine (A) pairs exclusively with Thymine (T) and Guanine (G) pairs exclusively with Cytosine (C).

To fit within microscopic nuclei, long DNA strands wrap tightly around specialized protein spools called histones, condensing into compact chromosomal structures. For their discovery, Watson, Crick, and Maurice Wilkins (1916-2004) were awarded the 1962 Nobel Prize in Physiology or Medicine[5].

The unique order of base pairs along a strand constitutes its genetic sequence. Because one strand runs from 5' end to  3' end and the opposing strand runs 3' end to 5' end[6], knowing the sequence of one strand automatically defines the complementary sequence of the other. Consider the following example, given a primary strand 5'- A T A C G T G -3', its complementary strand could be derived as 3'- T A T G C A C -5'. However, following the standard reading direction of a DNA strand, the DNA sequence should be taken as  5'- C A C G T A T -3'. Due to this property, DNAs in chromosomes are capable of duplicating through the process of separation of  its strands and forming new complementary strands for each of them. This intrinsic duplication mechanism allows DNA to faithfully replicate genetic information during every cell division.

 

Across any single species, the core DNA sequence remains remarkably conserved. In humans, for example, the genomic sequence across all 46 chromosomes is approximately 99.9% identical between any two individuals. The remaining 0.1% variation accounts for the entire spectrum of human diversity—dictating phenotypic traits such as height, skin pigmentation, hair texture, and individual health traits.

 

The totality of an organism's hereditary information is defined as its genome. While the vast majority of eukaryotic genetic material resides within nuclear chromosomes, a complete genome also includes organellar DNA—specifically the DNA found inside mitochondria and, in plant cells, chloroplasts.

 

Because DNA sequences record evolutionary history, comparative genomics has revolutionized evolutionary biology. A few such distinguished features of  evolutionary footprints in DNAs are summarized below:

 

• Molecular Clocks: By measuring genomic divergence between different species, researchers can estimate when lineages split from shared ancestors.
• Primate Lineage: The overall human genome differs by only about 1.2% from the chimpanzee genome, providing definitive molecular proof of a relatively recent common ancestor.
• Darwinian Synthesis: Direct DNA sequencing provides the precise, quantitative foundation that validates Darwin's model of common descent at the molecular level.

By decoding genetic sequences, scientists can now map the evolutionary tree with unprecedented mathematical precision.

 

Central Dogma of Molecular Biology

The realization that DNA sequence directs cellular function led to one of the most fundamental principles in modern life sciences: the Central Dogma of Molecular Biology. Formulated by Francis Crick, this framework describes the directional flow of genetic information within a biological system: DNA is transcribed into RNA, which is then translated into protein. Understanding this pathway requires looking at these two partner biomolecules:

 

• Ribonucleic Acid (RNA): Unlike double-stranded DNA, RNA is typically single-stranded. It shares a similar nucleotide composition, except Uracil (U) replaces Thymine (T) and pairs with Adenine (A).
• Proteins and Amino Acids: Proteins are linear chains built from 20 standard amino acids (e.g., Methionine [M], Proline [P], Lysine [K]). Proteins perform nearly all structural and functional tasks in the body—forming muscle fibers, catalyzing metabolic reactions as enzymes, and defending against pathogens as antibodies.

Specific segments of DNA that encode functional products are known as genes. The process of converting a gene’s sequence into a functional product—termed gene expression[7] —occurs in two sequential stages:

 

• Transcription: The gene region within the chromosome temporarily uncoils, allowing machinery to synthesize a complementary single-stranded messenger RNA (mRNA) molecule. For example, a DNA coding sequence of 5'-ATGCATTTC-3' produces an mRNA sequence of 5'-AUGCAUUUC-3'. Once transcribed, the DNA folds back into its supercoiled state.
• Translation: The mRNA transcript travels to cellular ribosomes, which read its molecular signal to construct a specific amino acid chain.

The Genetic Code and Triplet Codons

The mRNA coding sequence is organized into three-base units called codons. There are a few codons which also plays the role of  control signal of transcription. For example,

• Start Codon: AUG signals the start of translation and specifies the amino acid Methionine.
• Stop Codons: UAA, UAG, and UGA signal translation termination and do not code for any amino acid.

The rest of the codons are translated to one of the 20 amino acids. Because four bases arranged in groups of three yield 4³ (= 64) possible codons to specify 20 amino acids, multiple codons can encode the same amino acid. This degeneracy makes the genes more robust against point mutation while translating to a protein, essential to sustain life. Remarkably, this genetic code is nearly universal across all known life on Earth—from microscopic bacteria to human beings—reflecting a single, shared evolutionary origin for all terrestrial biology.

Because messenger RNA is copied directly from DNA, mapping a cell's genome allows scientists to locate protein-coding genes and uncover how they drive life processes or cause disease. This potential triggered a race to decode living DNA starting in the mid-20th century.

 

British biochemist Frederick Sanger (1918-2013) and American scientist Walter Gilbert (1932 - ) pioneered the field by inventing early sequencing techniques—Gilbert through chemical degradation (1973) and Sanger through chain termination (1977). Their discoveries earned them a shared Nobel Prize in 1980[8].

 

While Sanger sequencing dominated for two decades, reading long chromosomes posed a challenge. Researchers initially relied on "primer walking"—reading small, overlapping segments step-by-step from one end to the other. Eventually, scientists favored "shotgun sequencing," which breaks DNA into millions of random fragments, reads them simultaneously, and stitches them back together using algorithms.

 

Early progress was gradual, scaling up from simple microbes to complex organisms as briefly outlined below.

·       1976: Bacteriophage virus genome completed.

·       1992: First single chromosome sequenced (Yeast Chromosome III).

·       1995: First living bacterial cell fully decoded (Haemophilus influenzae).

·       1998: First multicellular animal sequenced (the roundworm C. elegans).

·       2004–2022: The initial draft of the Human Genome Project was published in 2004, but the final, truly complete sequence was achieved in 2022.

Today, high-throughput technologies make genome sequencing fast, cheap, and routine. By connecting genetic variation to disease and cellular function, genomics continues to unveil the fundamental mechanics of life—an exploration every bit as breath-taking as discovering new worlds in deep space.

 

Global Warming

 

The idea that industrial carbon dioxide emissions could warm the planet was first proposed by Swedish chemist Svante Arrhenius (1859-1927)  in 1896. At the time, few recognized how profound—and dangerous—this warming trend could become. A major milestone in atmospheric science occurred two decades later with the discovery of the ozone layer, a stratospheric shield sitting 15 to 30 kilometers above Earth that absorbs harmful solar ultraviolet rays. In 1974, scientists Mario Molina (1943-2020) and Sherwood Rowland (1927-2012) made an alarming discovery: widespread industrial chlorofluorocarbons (CFCs) were drifting into the upper atmosphere, where sunlight released chlorine atoms that systematically broke down ozone molecules. The theoretical threat became a proven crisis in 1985, when British scientists studying 30 years of Antarctic records confirmed a severe, annual "ozone hole" forming every October. Recognizing the urgency, policymakers signed the historic Montreal Protocol on September 16, 1987, banning global CFC production. Molina and Rowland earned the 1995 Nobel Prize in Chemistry for their discovery. Today, the Montreal Protocol stands as the most successful global environmental treaty in history; roughly 99% of banned ozone-depleting gases have been phased out, and the ozone shield is expected to fully recover over the coming decades.

 

While the world acted decisively to heal the ozone layer, it has been far slower to confront the dangers of rising greenhouse gas emissions. Naturally occurring greenhouse gases are constantly emitted and absorbed, creating a natural balance that makes life on Earth possible. Without carbon dioxide in our atmosphere, global temperatures would plunge by roughly 33°C, turning Earth into a frozen wasteland instead of maintaining our comfortable 15°C average.

Beside carbon dioxide, major greenhouse gases include methane, nitrous oxide, fluorinated gases, and water vapor. While water vapor fluctuates constantly based on temperature, other greenhouse gases remain stable unless driven up by outside forces. For nearly 10,000 years before the Industrial Revolution began around 1750, atmospheric CO₂ held steady at 280 parts per million (ppm)—creating the stable climate that allowed human civilization to thrive.

During the post-industrial era, human activity began shattering Earth’s natural carbon balance. The first clear proof came from American scientist Charles David Keeling (1928 – 2005), who established continuous atmospheric CO₂ monitoring at Hawaii’s Mauna Loa Observatory in 1958.

Keeling discovered that Earth essentially "breathes." As plants bloom across the Northern Hemisphere during spring and summer, they absorb carbon dioxide, causing atmospheric levels to drop to an annual low in September. In autumn and winter, as vegetation dies back, levels rise to a peak in May—a seasonal swing of about 6 ppm.

But Keeling noticed something far more concerning: underneath these seasonal swings lay a steady, continuous climb in overall CO₂ levels. Though funding agencies like the National Science Foundation (NSF) of USA  initially doubted the findings and threatened to cut support, Keeling’s persistent measurements gave birth to the Keeling Curve — the single most iconic graph in climate science.

What worries scientists most is how rapidly this increase is accelerating as shown below over the period starting from mid-eighteenth century.

·       1750 to 1958: It took over 200 years for CO₂ levels to rise by 35 ppm.

·       1958 to 2005: It took just 47 years to climb another 64 ppm.

·       2005 to 2018: It took only 13 years to jump an additional 26 ppm.

By May 2022, peak measurements at Mauna Loa hit 421 ppm. Atmospheric carbon dioxide is now accumulating at an unprecedented rate of nearly 3 ppm per year, driving global warming faster than at any point in human history.

Rising atmospheric carbon dioxide (CO₂) triggers a cascade of planetary changes, starting with global warming. Solar energy enters our atmosphere as light, warming the surface. Earth then tries to radiate that heat back into space as longwave infrared energy. However, greenhouse gases like CO₂ act like a blanket; they absorb this outgoing thermal heat and reflect it back toward the surface.

Burning fossil fuels is the primary driver of this carbon build-up, amplified by industrial pollution, agricultural expansion, and rapid deforestation. Destroying forests delivers a double blow. It releases stored carbon and destroys nature's primary mechanism for absorbing future emissions. At the same time, industry and farming emit atmospheric dust and airborne particles (aerosols). While these light-reflecting particles offer a slight cooling effect by scattering sunlight, they pollute our air and threaten public health.

The oceans also bear the brunt of rising emissions, absorbing 25% to 30% of human-produced CO₂. This causes ocean acidification, making marine environments increasingly toxic to coral reefs and shellfish. Today, atmospheric CO₂ levels are over 50% higher than pre-industrial baselines, driving a 30% increase in surface ocean acidity and pushing global ecosystems toward critical tipping points.

Scientists have been sounding the alarm on global warming since the 1970s, but world leaders and policymakers have been notoriously slow to act. The reason is simple: modern life runs on electricity, and for over a century, cheap fossil fuels—coal, oil, and natural gas—have been the easiest way to generate it.

Early interest in renewables like solar, wind, and hydro wasn't driven by a desire to save the climate, but by a fear that fossil fuels would eventually run out. When nations did build mega-hydroelectric dams in the 1950s, they often caused unintended ecological damage, altering river ecosystems and eroding shorelines.

Nuclear power was another promising substitute, adopted by many developed nations and countries like India. Yet high-profile disasters—such as Chernobyl in 1986 and Fukushima in 2011—showed how catastrophic a nuclear meltdown can be, leaving vast areas contaminated and driving widespread political pushback.

With nuclear power remaining controversial and renewables still scaling up, thermal power plants fueled by coal and gas continue to generate most of the world's electricity, while petroleum dominates transportation. So long as economic growth depends on burning fossil fuels, political leaders have found it difficult to translate scientific warnings into real policy changes.

Nature doesn't negotiate with politics, and science deals in objective facts—meaning global warming has continued unchecked regardless of political reluctance. By the late 1980s, however, mounting evidence finally shook the international community into action. In 1988, the United Nations established the Intergovernmental Panel on Climate Change (IPCC). Designed as an independent and impartial scientific body, the IPCC brings together world-class researchers to monitor environmental changes and publish regular, rigorous assessments of global climate data. Today, the organization includes 195 member nations, including India, working together to track the evolving planetary crisis.

The IPCC released its landmark First Assessment Report in 1990, delivering a clear message: human activities were trapping heat and warming the planet. Global temperatures had already risen between 0.3°C and 0.6°C over the previous century, and scientists warned that continuing business-as-usual would trigger a rapid warming rate of 0.3°C per decade.

This report sparked global political momentum. At the 1992 Rio Earth Summit, 154 nations formed the United Nations Framework Convention on Climate Change (UNFCCC), based in Bonn, Germany. To turn promises into action, world leaders began gathering annually in 1995 for the Conference of the Parties—better known as COP summits.

Over 30 summits have yielded two milestone international agreements:

·       The Kyoto Protocol (1997): Designed to mandate emission cuts for wealthy countries, Kyoto struggled after the U.S. failed to ratify it and major developing economies like China and India were not required to cut emissions, causing several nations to pull out.

·       The Paris Agreement (2015): A historic breakthrough where virtually every nation agreed to limit global warming to well below 2.0°C—ideally keeping it under 1.5°C. To hit that ambitious target, countries committed to cutting carbon dioxide emissions by roughly half by 2030, offering fresh hope for global climate action.

Seven years after the Paris Agreement, we have reached the halfway mark[9] toward our crucial 2030 climate goals. The IPCC’s Sixth Assessment Report confronted the world with a harsh reality: global emissions are pushing us deeper into dangerous territory at a terrifying speed.

The climate disasters of 2022 offered a grim preview of what an overheating planet looks like as highlighted below.

·       Record-breaking heatwaves scorched India and Western Europe.

·       Major rivers like the Rhine in Germany dried to trickle beds, while massive wildfires devastated forests in Bordeaux, France.

·       Historic ocean storms raged with a violent intensity unseen in centuries.

·       Monsoonal deluge inundated Pakistan, leaving a third of the nation underwater, while cities across India—like Bengaluru—suffered flash floods from cloudburst-like rain.

·       Polar ice caps and glaciers continue to melt at terrifying rates, making the Arctic navigable for the first time in human history.

These are not freak weather events; they are interconnected warnings of a warming world. As global temperatures climb, these destructive extreme events will become our new normal, threatening lives, infrastructure, and human civilization as we know it.

Not  a conclusion

 

We  observe how the realm of scientific discovery continually expands. Yet, every construct in the material universe bound by physical law possesses a beginning and an end, and science—a creation of human intellect—is no exception.  As climate change pushes humanity and global biodiversity toward existential risk, the focus of scientific discovery is shifting. In the coming decades, the defining narrative of science will be our struggle for survival: a chronicle of technological innovation deployed against severe thermal extremes, intense tropical cyclones, prolonged droughts, catastrophic flooding, and cascading ecological disasters. Ultimately, it will be the narrative of our boldest adventure yet—a fight to keep this planet livable, if not for every living creature, then at least for Homo sapiens!  A  pretty selfish agenda indeed!

(Originally written in Bengali in September, 2022;   translated and refined by Google Translate and Google Gemini, respectively.)

 

9th Sept., 2026

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[1] This text is a translation of the eighth and final chapter of the book “Science: Query and Quest” (বিজ্ঞানঃ জিজ্ঞাসা ও অনুসন্ধান)(2nd ed.), originally published in Bengali by Cornerstone Publications, Kharagpur,  in 2022.

 

[2] The photoelectric effect is the emission of electrons from the surface of a material when light or other electromagnetic radiation shines on it.

[3] While Cygnus X-1 is a famous stellar-mass black hole in our galaxy, the supermassive black hole at the center of the Milky Way is actually Sagittarius A.

[4] A main sequence star is any star in the stable, longest-running phase of its life cycle where it fuses hydrogen into helium in its core.

[5] Unfortunately Rosalin Franklin passed away in 1958 and was ineligible for posthumous nomination.

[6]  The 5’ to 3’ direction refers to the direction of polymerization forming the phosphor-sugar backbone  with reference to the positions of carbon atoms in the deoxyribose carbon rings.

[7] Gene expression can also yield functional non-coding RNAs, such as tRNA or rRNA. Both RNA and proteins are dynamic and transient, continuously synthesized, regulated, and degraded by the cell.

 

[8] Remarkably, Sanger had already won a Nobel Prize in 1958 for sequencing bovine insulin.

 

[9] The article was written in 2022.