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ASTR 1P01 Lecture 1: Introduction

Barak Shoshany・70 minutes read

Astronomy introduces basic concepts about celestial objects and the universe using the scientific method and observation, including the transition from a geocentric to heliocentric model. The vastness of cosmic distances, the composition of galaxies and atoms, and the scale of the universe are key topics, highlighting humans' position in the cosmos and the evolution of astronomical knowledge.

Insights

  • Astronomy is a science that uses the scientific method, involving observations, experiments, and hypotheses that are rigorously tested and verified to become established theories.
  • Ancient astronomers initially believed in a geocentric model with Earth at the center, but more precise measurements and observations led to the acceptance of the heliocentric model with the sun at the center of the solar system.
  • Understanding cosmic distances allows astronomers to observe the universe's history by looking at objects millions or billions of light-years away, providing insights into the evolution of the universe over time.

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Recent questions

  • What is astronomy?

    The study of celestial objects and the universe.

  • How do astronomers measure distances?

    Using light-years to showcase vast astronomical distances.

  • What is the Milky Way galaxy?

    The galaxy where Earth is located.

  • What is the Big Bang theory?

    The origin of the universe 13.8 billion years ago.

  • What are atoms made of?

    Nucleus with protons and neutrons, surrounded by electrons.

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Summary

00:00

Exploring Astronomy: From Earth to Universe

  • Astronomy 1 P1 at Brock University, taught by Professor Barak Shashani, introduces basic science and astronomy concepts, including celestial objects like planets, moons, asteroids, comets, stars, black holes, galaxies, and the universe.
  • Astronomy is a science that uses the scientific method, involving observations, experiments, and hypotheses that are rigorously tested and verified to become established theories.
  • The scientific method emphasizes skepticism, requiring evidence to support hypotheses, leading to the continuous improvement of understanding through new theories.
  • Ancient astronomers initially believed in a geocentric model with Earth at the center, but more precise measurements and observations led to the acceptance of the heliocentric model with the sun at the center of the solar system.
  • Astronomy constantly evolves with new theories, technologies, and instruments like telescopes and radio telescopes, enabling observations of celestial objects and phenomena.
  • General relativity revolutionized astronomy, introducing concepts like black holes, gravitational lensing, and gravitational waves, aiding in understanding the universe's origin through the Big Bang theory.
  • Distances in astronomy are often measured in light-years, with one light-year equaling approximately 9.5 trillion kilometers, showcasing the vastness of astronomical distances.
  • The Orion Nebula, located 1,300 light-years away, serves as an example of astronomical distances, highlighting how light from distant objects can take years, even centuries, to reach Earth, providing a glimpse into the past.
  • Earth, the Moon, and the Sun are significant celestial bodies, with Earth being the only known planet with life, the Moon being the only celestial body visited by humans, and the Sun being a star that generates energy through nuclear reactions.
  • Understanding cosmic distances allows astronomers to observe the universe's history by looking at objects millions or billions of light-years away, providing insights into the evolution of the universe over time.

24:29

"Exploring the Vast Universe Beyond Earth"

  • Centor is a star located 4.2 light-years away, approximately 40 trillion kilometers, with no other stars in between.
  • The solar system consists of eight planets orbiting the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
  • Planets and moons reflect the sun's light as they do not generate their own light.
  • Galaxies contain between 100 million to 100 trillion stars, with interstellar gas and dust between them.
  • The Milky Way galaxy, where Earth is located, contains 100 to 400 billion stars and is 100,000 to 200,000 light-years wide and 1,000 light-years thick.
  • The Milky Way galaxy is believed to be a spiral galaxy similar to the NGC 173 galaxy, with spiral arms and a central bar.
  • The sun is located between 25,000 and 29,000 light-years from the center of the Milky Way galaxy in the Orion arm, orbiting at 230 kilometers per second.
  • At the center of the Milky Way galaxy is a supermassive black hole called Sagittarius A*, with a mass equivalent to four million suns.
  • The Milky Way galaxy is part of the Local Group, which includes the Andromeda galaxy and at least 80 smaller galaxies, forming the Virgo Supercluster.
  • The Virgo Supercluster is 110 million light-years in diameter, containing at least 100 galaxy groups and clusters, with the Milky Way orbiting its center of mass.

47:43

"Exploring the Universe: Galaxies, Expansion, and Notation"

  • The center of mass can be calculated based on the masses and positions of all galaxies, known as the center of the local group.
  • The Milky Way orbits the center of mass, which is an imaginary point representing the average of all masses.
  • The Virgo super cluster is part of the Lania super cluster, containing over 100,000 galaxies with a diameter of 520 million light years.
  • The most distant known galaxy, GN-z11, is located 32 billion light years away.
  • The universe began expanding from a hot and dense state 13.8 billion years ago at the Big Bang, leading to the formation of stars and planets.
  • The expansion of the universe is not an explosion but a continuous process, with distances becoming longer over time.
  • The universe's expansion may lead to the heat death scenario, where the universe becomes too cold for any activity to occur.
  • The observable universe is a sphere with a diameter of 93 billion light years, with the edge being 46.5 billion light years away.
  • Light from objects beyond the observable universe has not reached us due to the ongoing expansion of the universe.
  • Scientific notation, involving numbers multiplied by powers of 10, is used to represent large distances and time scales in astronomy.

01:10:33

"Scientific Notation, Universe Scales, Atom Structure"

  • To multiply two numbers in scientific notation, multiply the coefficients and add the exponents.
  • For example, 1.2 * 10^3 * 3 * 10^6 equals 4.2 * 10^9.
  • Understanding the concept is crucial, even though calculators can be used.
  • The size of the observable universe is 93 billion light years, or 10^27 meters.
  • One light year is 9.5 trillion kilometers, or 9.5 * 10^12 kilometers.
  • The observable universe is approximately 10^24 kilometers, or 10^27 meters.
  • The size of the observable universe is approximately 10^24 kilometers, or 10^27 meters.
  • A video on YouTube illustrates the scales of the universe from human to cosmic levels.
  • Negative powers of 10 represent fractions, like 10^-3 for 1/1000.
  • Atoms consist of a nucleus with protons and neutrons, surrounded by electrons in a fuzzy cloud.

01:30:33

"Atomic Matter: From Quarks to Universe"

  • Quantum mechanics was developed in the 1920s and 30s, leading to the realization that the previous atom model was incorrect.
  • There are currently 118 known chemical elements, which make up all Atomic matter in the universe.
  • The number of protons in an atom determines its atomic number and type of chemical element.
  • Hydrogen, with one proton, is the most common element, making up 74% of Atomic matter, followed by helium at 24%.
  • Atoms are made of a nucleus containing protons and neutrons, which are composed of up and down quarks.
  • Elementary particles like electrons, up quarks, and down quarks make up all known atoms.
  • Quarks and electrons are treated as point particles in calculations due to quantum mechanics' fuzziness.
  • Quarks are smaller than 10^-19 meters, while electrons are smaller than 10^-22 meters.
  • Humans are positioned between the smallest (electron) and largest (observable universe) scales in the universe.
  • Traveling to the nearest galaxy, Andromeda, would take billions of years at the fastest human-made spaceship speed, making it practically impossible with current technology.

01:53:51

"Humanity's Brief Existence in Cosmic Timeline"

  • Humanity's existence is a mere fraction of the age of the universe, with humans appearing in the last 25 minutes of a hypothetical year representing the universe's timeline, and recorded history starting only 10 seconds before the year's end, showcasing the vastness of time in comparison to human history.
  • The lecturer recommends exploring the textbook "Open STS Astronomy" for further insight, particularly focusing on reading Chapter One and Appendices A to D, while emphasizing that the lectures are the primary material for the course, with exams based on them, and additional resources like books, websites, and videos suggested for those seeking deeper understanding beyond the lectures.
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