CORE 122S - Life in the Universe: A Cosmic PerspectiveExamines the historical debate on the concept of whether extraterrestrial life exists. Students examine what astronomy and physics tell about the origin and evolution of the Universe, the production of elements that make up living matter on Earth, the evolution of stars like the Sun, and the formation of solar systems. Also examined are the astronomical, geological, chemical, and biological conditions that were responsible for the origin and evolution of life on Earth, and speculate about the possibility of life on other planets in our solar system or on planets around other stars. How would one detect the presence of life on other planets in the solar system; in the galaxy? The development of intelligent life and the possibility of contact between civilizations are examined.Credits: 1.00Corequisite: NonePrerequisites: None Major/Minor Restrictions: NoneClass Restriction: No Junior, SeniorArea of Inquiry: NoneLiberal Arts CORE: Scientific PerspectivesClick here for Course Offerings by term
Life @ The Cosmic Core
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Because of that, no phosphorus was available for life when Earth formed, and it had to come from somewhere else. It also had to arrive on Earth over a long period of time. Previously, scientists hypothesized that meteorites and comets might be the source. But a new study suggests that phosphorus might come from cosmic dust.
After a core collapse supernova, all that remains is a dense core and hot gas called a nebula. When stars are especially large, the core collapses into a black hole. Otherwise, the core becomes an ultra-dense neutron star.
Lying at the very heart of the Milky Way is a supermassive black hole called Sagittarius A*. About 4 million times the mass of the sun, this beast consumes anything that strays too close, gorging on an ample supply of stellar material enabling it to grow into a giant. In 2022, we imaged this glutton at the core of our galaxy for the very first time, through an innovative technique allowing us to view the shadow of the black hole.
We now know that the Milky Way resides within the Local Group of galaxies, made up of over 30 galaxies including Andromeda, Triangulum and Leo I to name but a few. It turns out that it's pretty good to know who your neighbors are, as they may be closer than you think. The Milky Way is currently hurtling towards Andromeda at 250,000mph (400,000 km/h). Though there is no need to worry just yet, this crash of cosmic proportions is not due for another 4 billion years.
The galaxy's evolution is, however, still shrouded in mystery. A discipline called galactic archaeology is slowly unraveling some of the puzzles of the Milky Way's life thanks to the Gaia mission, which released its first catalog of data (opens in new tab)in 2018.
We tend to accept that it is natural for humans to inhabit the cosmos. We ask ourselves how it could be otherwise. What would be the point of the universe if it had not allowed us to exist? This misinterpretation of the so-called anthropic principle, which according to astrophysicist and populariser Ethan Siegel is the most abused idea in science, often leads to a corollary: if we are here, why not many, many millions of others? Another principle, that of mediocrity, suggests that there is nothing special about our galaxy or Earth. And yet, so far, not only are we unaware of the existence of anyone else, but we have yet to find a planet similar to our own. Life is far from inevitable, say scientists, and our presence here may simply be the result of a series of lucky events, like prizes from a cosmic lottery that many other planets missed out on at some point in their history.
The existence of life on Earth rests on five main pillars: the distance from the Sun, neither too close nor too far away, just enough for liquid water; the magnetic core, which protects the atmosphere from the drag of the solar wind and life from cosmic radiation; the atmosphere itself, whose greenhouse effect prevents water from freezing; water, naturally, the universal solvent of life; and finally oxygen, which allows us to breathe.
The emergence and evolution of early life is a field in which science will have to make further progress, as the clues are still incomplete. The first single-celled organisms lived in an unbreathable atmosphere, composed of gases such as methane and ammonia. Around 2.4 billion years ago, the so-called Great Oxidation Event took place, when the atmosphere began to be populated by oxygen in its breathable molecular form, which is attributed to the emergence of photosynthetic cyanobacteria. However, a comparative molecular analysis concludes that these appeared after the Great Oxidation, leaving the emergence of breathable oxygen to other, even more primitive microbes.
However, what made the emergence of complex life possible was at the same time the cause of the first great terrestrial extinction, as oxygen was a poison to other early living things. In turn, the reaction of oxygen with methane consumed this potent greenhouse gas and produced water and carbon dioxide, leading to a brutal change in climate that enveloped the Earth in ice for 300 million years.
Oxygen was thus the first major cause of extinction on Earth, but at the same time it was the engine of life, a turning point in the course of evolution that would give rise to multicellular beings and the explosion of life as we know it today, enormously diverse and complex, a cosmic lottery in which, at least as far as we know, only a first prize has been awarded.
When searching for signs of life in the Universe, we tend to look for very specific things, based on what we know: a planet like Earth, in orbit around a star, and at a distance that allows liquid surface water. But there could, conceivably, be other forms of life out there that look like nothing that we have ever imagined before.
It all depends on how you define life. If the key criteria are the ability to encode information, and the ability for those information carriers to self-replicate faster than they disintegrate, then hypothetical monopole particles threaded on cosmic strings - cosmic necklaces - could form the basis of life inside stars, much like DNA and RNA form the basis of life on Earth.
In 1988, Chudnovsky and his colleague, theoretical physicist Alexander Vilenkin of Tufts University, predicted that cosmic strings could be captured by stars. There, the turbulence would stretch the string until it formed a network of strings.
"Compared to the lifetime of a star, its lifetime is an instantaneous spark of light in the dark. What is important is that such a spark manages to produce more sparks before it fades away, thus providing a long lifespan of the species," the researchers write.
"The complexity evolving through mutations and natural selection increases with the number of generations passed. Consequently, if lifetimes of self-replicating nuclear species are as short as lifetimes of many unstable composite nuclear objects are, they can quickly evolve toward enormous complexity."
What such a species would look like is a feast for the imagination. But we don't have to know what they look like to search for signs of their presence. Because such organisms would use some of the energy of their host star to survive and propagate, stars that seem to cool faster than stellar models can account for could be hosts for what the researchers call "nuclear life". 2ff7e9595c
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