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Introduction to Astronomy Concepts and Methods

May 13, 2025

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Astronomy 1P1 - Introduction to Astronomy

Course Introduction

  • Instructor: Professor Barak Shashani
  • Course: Astronomy 1P1 at Brock University
  • Lecture goals:
    • Introduction to basic concepts in science and astronomy.
    • Overview of fascinating topics to be covered.
    • Discussion on scales of the universe.

What is Astronomy?

  • Study of celestial objects outside Earth:
    • Planets, moons, asteroids, comets, stars, black holes, galaxies, and the universe.
  • Astronomy is a science:
    • Science is not a body of knowledge, but a method for obtaining and verifying knowledge.
    • Involves making observations, experiments, and creating hypotheses.
    • Hypotheses lead to predictions tested experimentally.
    • Verified hypotheses become theories.
    • Theories help understand the universe, predict events, and create new technologies.
    • Science is self-correcting; skepticism is key.

The Scientific Method

  • Process of creating and testing hypotheses.
  • Scientists remain skeptical until sufficient evidence supports a hypothesis.
  • No theory is sacred; new evidence may lead to new theories.

Evolution of Astronomical Models

  • Ancient geocentric model with Earth at center was replaced by heliocentric model.
    • The sun is at the center of the solar system, not the universe.
  • Astronomy evolves with new theories and precise instruments.

Unanswered Questions in Astronomy

  • Dark matter and dark energy.
  • Center of a black hole.
  • Existence of life on other planets.

Limitations and Tools in Astronomy

  • Astronomers can't do lab experiments, can only observe using telescopes.
  • Improvements in technology lead to better, detailed observations.
  • Use of instruments for different types of electromagnetic radiation.

Professor's Research: General Relativity

  • Provides description of gravity, space, and time.
  • Revolutionized astronomy by introducing black holes, gravitational lensing, and waves.

Measuring Distances in Astronomy

  • Lightyear: Distance light travels in one year.
  • Light travels at 300,000 km/s or 1 billion km/h.
  • One lightyear ≈ 9.5 trillion km.

Astronomical Distances

  • Distances like the Orion Nebula (1300 lightyears away).
  • Observing celestial objects is like looking into the past.
  • Time machine analogy for observing distant objects.

Tour of the Universe

  • Earth: Diameter ≈ 13,000 km.
  • Moon: Diameter ≈ 3,500 km; Distance from Earth ≈ 384,000 km.
  • Sun: A star with nuclear reactions generating energy.
  • Proxima Centauri: Nearest star (4.2 lightyears away).
  • Solar System Planets: Mercury through Neptune.
  • Galaxies: Collections of billions of stars.
    • Milky Way Galaxy: 100-400 billion stars.
    • Andromeda Galaxy: 2.5 million lightyears away.

Large Scale Structures

  • Local Group: Includes Milky Way and Andromeda.
  • Virgo Supercluster: Part of the Laniakea Supercluster.
  • Laniakea Supercluster: Contains over 100,000 galaxies.

The Big Bang and Universe Expansion

  • Universe began 13.8 billion years ago from a dense state.
  • Expansion started in the Big Bang.
  • Observable universe: Sphere with 93 billion light-year diameter.

Misconceptions and Limits

  • Expansion is not into anything; distances are increasing.
  • Observable universe is limited by light travel time.
  • Universe might be infinite or cyclic.

Smallest and Largest Scales in the Universe

  • Elementary particles: Electrons, quarks (up, down).
  • Protons/neutrons made of quarks.
  • Electrons ≈ less than 10^-22 meters.
  • Observable universe ≈ 10^24 km.
  • Humans located in the middle of these scales.

Potential for Human Space Travel

  • Current technology limits human travel to the solar system.
  • Andromeda and further galaxies unreachable with current technology.

Time Scales

  • Universe: 13.8 billion years.
  • Humans evolved 300,000 years ago.
  • Recorded history 5,000 years.
  • Visual analogy: Universe year; humans appear on December 31st.

Reading and Further Exploration

  • Recommended textbook: OpenStax Astronomy.
  • Chapter 1 and appendices A-D for further reading.
    • Lectures are primary material for exams.
    • Further exploration resources are available for deeper understanding.

These notes provide an overview of the key concepts and ideas discussed in the initial lectures on astronomy.

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