From: inteligencialtda
Scientific thought is an evolving process, characterized by the continuous refinement of ideas and the constant pursuit of new knowledge through observation and experimentation [00:41:04].
Origin of Life Theories
The precise origins of life and water on Earth remain subjects of significant scientific inquiry [02:51:57].
Origin of Water
Initially, it was theorized that Earth’s water originated from comets, which are essentially “ice balls” [00:26:08]. This idea gained traction following the 1986 flyby of Halley’s Comet by the European Space Agency’s Giotto probe, which detected water similar in composition to Earth’s [00:27:17]. However, this data was later found to be flawed due to equipment malfunction [00:28:34].
In 2014, the Rosetta probe visited Comet 67P/Churyumov–Gerasimenko, discovering water with a different composition, specifically containing “heavy hydrogen” (deuterium), unlike Earth’s water [00:28:51]. This led to further investigation, revealing that water found in some asteroids has a composition similar to Earth’s [00:29:45].
The prevailing hypothesis today suggests a combination of sources: some water from asteroids, potentially some from comets, and a significant portion from Earth being “born wet” with water embedded in pre-solar dust particles during its formation [00:30:34].
Building Blocks of Life
Life as we know it requires six fundamental elements, often referred to as CHONPS: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur [00:38:05]. Carbon is considered the most crucial due to its ability to form long, complex chains, essential for molecules like glucose and hydrocarbons [00:39:05]. Carbon in our bodies and trees originates from atmospheric CO2, fixed by plants and other organisms [00:39:33].
Primordial Soup Hypothesis and Miller-Urey Experiment
The “primordial soup” hypothesis, stemming from ideas proposed by Darwin and later formalized by Oparin and Haldane, suggested that early Earth’s conditions—ammonia, methane, water, and electrical discharges (lightning)—could have led to the formation of complex organic molecules like amino acids [00:41:19].
Miller-Urey Experiment
In 1953, Stanley Miller and Harold Urey conducted an experiment replicating these early Earth conditions in a closed laboratory system, successfully demonstrating the formation of amino acids from simple compounds and an energy source like electrical discharge [00:41:42]. This groundbreaking experiment provided early evidence for abiogenesis. However, criticisms arose regarding the stability of methane and ammonia in the primitive atmosphere [00:50:11].
Hydrothermal Vents Hypothesis
A significant alternative to the primordial soup hypothesis emerged with the discovery of hydrothermal vents (also known as “fumaroles”) on the ocean floor in 1977 [00:50:42]. These deep-sea environments, found at depths of 2,500 meters, release water rich in minerals and sulfur compounds (like H2S) [00:51:30].
In these conditions, chemosynthesis occurs, where bacteria utilize H2S and dissolved CO2 to create complex carbon compounds [00:52:07]. This process is a more plausible long-term energy source for early life than sporadic lightning strikes [00:52:45]. The Earth’s geological activity, including volcanism and plate tectonics, provides continuous recycling of materials, essential for sustaining life’s cycles [01:00:09].
Panspermia Hypothesis
The theory of panspermia suggests that life’s fundamental building blocks, or even life itself, could have originated elsewhere in the universe and arrived on Earth via cosmic bodies [00:53:12]. While some versions postulate that fully formed life arrived, the more accepted view is that basic organic compounds, such as amino acids, were delivered by asteroids and comets [00:53:24]. Samples from asteroids like Bennu and Ryugu confirm the presence of these “fundamental blocks of life” [00:54:04].
Earth’s early conditions, including a dense atmosphere for protection from solar radiation and a stable temperature, provided the “ideal oven” for these building blocks to combine and form life [00:54:53].
Defining and Studying Life
Life, as defined by scientists, involves three core components:
- Metabolism: The chemical processes that occur within a living organism (e.g., cellular respiration, photosynthesis) [02:52:06].
- Membrane: A structure, like a cell, that encloses and defines the organism [02:53:05].
- Replicating Material: Genetic material (initially RNA, later DNA) capable of self-replication [02:53:40].
With these components, natural selection can act, leading to evolution [02:53:40]. Recent phylogenetic reconstructions, using DNA mutation rates, estimate that the Last Universal Common Ancestor (LUCA) of all life on Earth emerged approximately 4.2 billion years ago, within the first 500 million years of Earth’s formation [01:10:40].
Evolution and its Impact
The term “evolution” in science simply means “change” or “unfolding,” not necessarily an improvement [01:54:19]. Darwin himself preferred “transmutation” [01:56:01]. The theory of evolution is one of the most well-founded and corroborated theories in science, with abundant evidence, including fossil records (like stromatolites) and observable changes in organisms like viruses and bacteria [02:54:13].
The Evolution of Photosynthesis
Approximately 2.4 to 2.7 billion years ago, cyanobacteria began to perform aerobic photosynthesis, releasing oxygen into the atmosphere [01:04:13]. This “Great Oxidation Event” fundamentally changed Earth’s atmosphere, leading to the first mass extinction of anaerobic organisms but also creating conditions for the evolution of oxygen-breathing animals, including humans [01:05:50].
Consciousness and Intelligence
- Intelligence: Defined as the ability to solve various problems, intelligence has evolved across diverse groups of animals, including solitary creatures like octopuses [02:37:43].
- Self-awareness/Self-consciousness: The awareness of oneself, tends to evolve in social animals. It is typically assessed using the mirror test, where an animal recognizes itself in a reflection [02:38:20]. Humans (from about 2 years old), chimpanzees, and orangutans are among the few species known to pass this test [02:39:16].
Search for Extraterrestrial Life
The search for extraterrestrial life is ongoing, with astrobiology identifying key requirements for life on other planets:
- Plate Tectonics: Essential for material recycling and maintaining stable conditions [01:00:43].
- Large Moon: A significant moon helps stabilize a planet’s axial tilt, which is crucial for consistent seasons and the long-term evolution of complex life [02:54:01].
Experiments in Space Environments
Agencies like the European Space Agency conduct experiments by sending organisms into space to test their resilience to extreme conditions like vacuum, radiation, and extreme temperatures [03:06:55].
- Tardigrades (Water Bears): These millimeter-sized animals can enter a state of cryptobiosis, forming a cyst that allows them to survive in harsh conditions, including the vacuum of space, for extended periods [03:06:17]. While they can survive, radiation remains a significant challenge for their long-term viability [03:07:41].
- Lichens: A symbiotic organism of fungi and algae, lichens are highly resistant to extreme environments. Experiments have shown them to survive 18 months outside the International Space Station, enduring near-absolute zero temperatures, space vacuum, and radiation [03:08:06]. They are considered strong candidates for terraforming Mars, but scientists currently avoid sending them to Mars to prevent contamination and preserve potential evidence of indigenous Martian life [03:10:11].
Potential Contamination
In 2019, an Israeli probe, Beresheet, crashed on the Moon, carrying 2,000 tardigrades. The fate of these tardigrades is uncertain, but they could potentially survive if protected by lunar regolith [03:10:25].
The Limits of Interstellar Travel
The vast distances in space pose immense challenges to interstellar travel. Traveling to Alpha Centauri, the closest star system, would take 100,000 years with current technology [03:04:15]. The idea of human colonization of other planets or interstellar travel is largely considered science fiction, with multi-planetary life (e.g., establishing colonies on Mars) also facing significant hurdles [03:05:08].
Current Challenges in Science
Despite the intellectual excitement of scientific discovery [02:28:33], the scientific community faces several challenges:
- Funding: Cutting-edge science requires substantial investment, with countries like China and the United States investing tens of billions of dollars annually [03:17:36].
- Big Science vs. Retail Science: “Big Science” involves massive investments in infrastructure like particle accelerators (e.g., Brazil’s Sirius) or space programs, yielding fundamental discoveries that drive broader technological advancements [03:32:00]. “Retail Science” encompasses smaller, individual research projects [03:49:09]. Connecting fundamental basic science with daily applications is a significant challenge [03:48:42].
- Interdisciplinarity: While scientific advancements often arise from combining diverse fields (e.g., chemistry, biology, geology for the origin of life), academic structures can hinder such integration [03:55:04].
- Brain Drain: Lack of consistent long-term investment and career security can lead highly trained scientists to seek opportunities abroad [04:29:57].
Obscurantism
There is a concern about a rise in obscurantism in recent years, which poses a threat to scientific progress [03:26:27].