Big Bang Theory: Origin and Structure of the Earth

Started with a Bang: Origin and Structure of the Earth

• The Big Bang theory is the most widely accepted explanation for the origin of the Universe.
• Observations suggest galaxies are moving away from each other at great speed, implying an ancient explosion.
• Before the Big Bang, all matter and radiation in the observable universe existed as a hot, dense mass, only millimeters across.
• This state existed for a tiny fraction of the first second.
• A massive blast, roughly 10 to 20 billion years ago, allowed matter, energy, space, and time to spring from an unknown energy source
• In a trillion-trillionth of a second, the universe expanded from a pebble-size to astronomical scope.
• Expansion has slowed over billions of years

Origins of the Theory

• Georges Lemaitre, a Belgian priest, proposed the Big Bang Theory in the 1920s
• He theorized that the universe originated from a single primordial atom.
• Edwin Hubble's observations of galaxies speeding away provided key support
• The discovery of cosmic microwave radiation by Arno Penzias and Robert Wilson also bolstered the theory.
• The glow of cosmic microwave background radiation is remnant light from the Big Bang.
• The cosmic microwave background radiation is similar to radiation used to transmit TV signals.
• The original cause of the Big Bang is a major unanswered question.

NASA Technology Views Birth of the Universe

• Gravitational waves rippled through the early universe during inflation, an explosive growth period.
• Evidence for gravitational waves strongly supports cosmic inflation theories
• Cosmic inflation theories claim the universe expanded by 100 trillion times incredibly rapidly.
• NASA-developed detector technology on the BICEP2 telescope at the South Pole made the findings possible
• The BICEP2 telescope operated in collaboration with the National Science Foundation.
• The universe came into existence 13.8 billion years ago in the Big Bang.
• Space expanded exponentially in the period called inflation.
• The cosmic microwave background holds tell-tale signs of the universe's early history.
• The Planck satellite (a European Space Agency mission with NASA detector and cooler technology) previously confirmed aspects of the Big Bang theory
• Researchers sought direct evidence of inflation in gravitational waves.
• "Small, quantum fluctuations were amplified to enormous sizes by the inflationary expansion of the universe"
• Density waves are produced in addition to gravitational waves
• Gravitational waves create a swirly pattern ("B-mode" polarization) in polarized light.
• Light becomes polarized when scattered off surfaces, like cars, ponds, or electrons (in cosmic microwave background).
• The BICEP2 team detected B-mode polarization at the South Pole using expertise and new technology.
• Key contributions or collaborators with the BICEP2 team include Caltech, JPL, Stanford University, Harvard University, and the University of Minnesota
• Experiments since 2006 have produced compelling evidence for the B-mode signal and cosmic inflation.
• Novel superconducting detectors are key and they superconductors chilled allow electrical current to flow freely.
• The technology combines superconductivity with microscopic structures, manufactured using micro-machining.
• Anthony Turner manufactures the tiny components using specialized fabrication equipment at JPL's Micro devices Laboratory
• The B-mode signal is extremely faint
• Bock and Turner developed an array of multiple detectors, akin to digital camera pixels, but able to detect polarization.
• The detector system runs at 0.25 Kelvin (just 0.45 degrees Fahrenheit above absolute zero).
• The BICEP2 experiment used 512 detectors, speeding up cosmic microwave background observations 10-fold.
• New experiments use 2,560 detectors.
• Experiments help understand the exotic forces that drove space and time apart and confirm the universe inflated dramatically.
• Results of the study have been submitted to the journal Nature.
• JPL is managed by the California Institute of Technology for NASA

How Did the Sun and Planetary System Form?

• The Solar System consists of the sun and revolving celestial bodies like planets, satellites, comets, and meteors.
• Nicolaus Copernicus described the modern heliocentric system.
• Before Copernicus in 1543, in the Ptolemaic System, the Earth held the central place in the universe.
• Copernicus placed planets in circular paths around the sun, with Earth as the sixth planet with the moon as its satellite.
• Some scientists have formulated theories to explain the solar system's origin.
• Immanuel Kant (1755) and Laplace (1796) proposed related hypotheses.
• The solar system came from the condensation of a dispersed gaseous atmosphere around the sun.
• Increased rotational velocity of this atmosphere led to a discoidal shape.
• As velocity reached a critical point, rings of gas broke off, eventually forming gaseous globes that became solid planets.
• Most gaseous globes abandoned rings, which formed satellites.
• The Nebular Hypothesis suggests solar system formed with regular motions.
• The Planetesimal Theory claims the planetary system came from materials removed from the sun by a passing star's tidal action.
• Projection became gases which revolved around the sun which become masses.
• The larger bodies attracted smaller ones to become planets.
• The smaller bodies became asteroids, meteors, and satellites.
• Carl Friedrich von Weizacken and Harold C. Urey formulated the Dust Cloud Theory in 1945.
• The nebula was mainly hydrogen and helium, like the sun, with 1% heavier elements.
• This "Dust Cloud" was originally 10% of the sun's mass, or 100x the mass of planets and satellites.
• The nebula was flattened by rotation.
• Gas molecules moved faster near the sun and interacted, accelerating lighter ones to escape the nebula.
• Interactions created swirls and lumps that grew into planets and satellites.
• Gerald P. Kuoper proposed the Protoplanet Hypothesis in 1949.
• The original nebula was massive and broke into protoplanets upon contraction and flattening.
• Protoplanets remained stable in the sun's tidal field.
• They contracted, formed denser cores, and developed large atmospheres of lighter gases.
• The shrinking sun emitted corpuscular and ultraviolet radiations.
• Radiations drove away nebula remnants and planet atmospheres, appearing as comets with tails.
• This hypothesis explains planetary systems around many stars.
• Most yellow stars, like the sun, may have planets.
• The boundaries and origin of the universe are currently unknown, with no proof if did/didn't originate suddenly in an explosion or has it been in a process of creation without a definite beginning or end.

Subsystems of the Earth

• Earth includes Lithosphere, Hydrosphere, Biosphere, and Atmosphere.
• Litho means stone, hydro means water, atmo means air, and bio means life.
• Lithosphere: rocky crust of the earth, inorganic, composed of minerals.
• It includes the uppermost mantle and crust.
• Mantle surrounds the core, characteristics vary with depth.
• The outermost mantle (100 km depth) is cool, strong, and hard.
• The layer below 100km is hot, weak, soft, plastic, and flows slowly.
• Deeper, mantle rock becomes strong again as pressure overwhelms temperature.
• Crust (outermost layer): a thin veneer below soil and ocean water.
• It is made of almost entirely solid rock.
• Hydrosphere: all waters that circulate on Earth (oceans, seas, rivers, lakes, moisture).
• Oceans cover 71% of Earth and currents transport heat, changing climate.
• Atmosphere: mass of air surrounding our planet, has layers of different densities.
• Air is comprised of 79% Nitrogen and fewer than 21% Oxygen.
• The remaining amount is Carbon Dioxide and other form of gases.
• Atmosphere is held to Earth by gravity.
• Atmosphere thins rapidly with altitude.
• Ninety-nine percent is in the first 30 kilometers.
• Traces remain as far as 10,000 kilometers.
• Atmosphere helps because animals need oxygen, plants need carbon dioxide and oxygen.
• The atmosphere supports life indirectly via climate regulation.
• Air is a blanket and filter, retaining heat and shielding from radiation.
• Wind transports heat from equator to poles, cooling/warming regions.
• Biosphere: all living organisms from bacteria to whales.
• Includes plants, animals, single-celled organisms, uppermost geosphere, hydrosphere, lower atmosphere.
• Sea life concentrates near the surface because sunlight is available.
• Plants grow on Earth's surface, roots go a few meters underground.
• Bacteria live in rock (up to 4 km deep).
• Microorganisms drift at 10+ km height.
• Plants and animals are affected by Earth's environment (air, water, temperature).
• Earth's environment is altered and formed by plants/animals.
• Living organisms contributed to the evolution of the modern atmosphere.
• Subsystems interact, influencing climate, geological processes, and life.

Characteristics of Earth that are Necessary to Support Life

• Key ingredients are needed for life to exist
• There is debate about the limits of life.
• Even Earth hosts strange creatures in extreme environments.
• Liquid needed for reactions, for example a place where molecules can go react
• A soup such as DNA and proteins can swim around and interact with each other to carry out the reactions needed for life to happen.
• Water supports earth life and is an excellent solvent.
• Ice insulates underlying fluid from freezing further.
• If instead water sunk when frozen, this would freeze everything.
• Astronomers focus on planets in habitable zones (orbits neither too hot nor too cold) for liquid water.
• Earth is within the habitable zone.
• Mars and Venus are outside it; if Earth's orbit was further inside/outside, life may not have arisen.
• Alien life may not play by our rules.
• Astrobiologists suggest looking beyond habitable zones.
• Liquid water might have existed on Mars/Venus.
• Life might have evolved, then fled underground or adapted.
• Other solvents might host life, for example Saturn's moon, Titan, with liquid methane and ethane.
• Life needs energy for reactions.
• The most obvious source of energy is a planet's host star, for example photosynthesis
• Sunlight drives photosynthesis, and produced nutrients become the fuel utilized by life.
• Countless organisms subsist on other energy sources, such as chemicals in deep water vents.
• Scientists debate if habitable worlds need stars that live for billions of years for life to evolve.
• Some stars only live a few million years.
• Life might originate very fast.
• Earth is 4.6 billion years old.
• Oldest organism appeared 3.5 billion years ago, so life might evolve in 1.1 billion years or less.
• Complex life took longer (multicellular animals 600 million years ago).
• Our sun is long-lived, allowing higher order of life.
• Plate tectonics is important for recycling (broken plates that move constantly).
• Plate tectonics recycles molecules life needs
• Carbon dioxide helps trap heat, but gets bound in rocks over time, freezing the planet.
• Plate tectonics drags rock downward to melt, releasing carbon dioxide through volcanoes.
• Plate tectonics is useful but probably not imperative.
• Volcanism might provide enough fresh supplies of whatever life might need.
• Bonus: Earth has low variation in sun's radiation and a magnetic field.
• Magnetic field protects from charged particles of the sun.
• Violent radiation bursts could have scoured life from early Earth.
• People are rethinking these factors and how important they are.
• Scientists are trying to be more open-minded about alternate possibilities for life.
• Earth remains the only known planet to host life due to a unique combination of factors.
• Monitoring other worlds might reveal other life or other ways life can blossom.

Habitable Planets

• Even planets near other stars are not guaranteed to be habitable.
• Astronomers have proposed conditions needed to make a planet habitable.
• The central star must last long enough for sustained life to evolve (at least 2 billion years) and will not kill evolving life with UV radiation which breaks down organic molecules.
• A central star should be at least 0.3 Mo to create a large orbital zone where a planet could retain liquid water.
• Central star needs to be stable, not flare violently or emit strong x-rays, giving the planet long-term stability.
• A planet must orbit the right distance from the star for liquid water to exist.
• A planet's orbit has to be stable at a proper distance to prevent large seasonal changes.
• A planet’s gravity must be strong enough to hold a substantial atmosphere.