Earth and Space

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Across
  1. 3. The second lightest element, created alongside hydrogen in the first few minutes of the universe.
  2. 7. A giant interstellar cloud of gas and dust from which our solar system was born.
  3. 8. The invention that allowed 17th-century scientists to finally disprove the Geocentric model.CMB – (Abbreviation) The "Cosmic Microwave Background" radiation that serves as evidence for the Big Bang.
  4. 10. Ancient philosopher who argued the Earth was a sphere but wrongly believed it was stationary.BRAHE – The Danish nobleman who made the most accurate naked-eye observations of the stars before the telescope.
  5. 12. The flat, spinning disk of gas and dust surrounding the young Sun where planets began to form.
  6. 13. The "building blocks" of planets; small objects formed from the collision of dust and rock.
  7. 15. Observation that light from distant galaxies is stretched to longer wavelengths, proving the universe is expanding.
  8. 16. The "middle" layer of the atmosphere where most meteors burn up upon entry
  9. 18. The hypothesis that explains how our solar system formed from a spinning cloud of gas and dust.
Down
  1. 1. The first to use a telescope to observe the moons of Jupiter, proving not everything revolves around Earth.
  2. 2. The ancient model (championed by Ptolemy) that placed the Earth at the center of the universe.
  3. 4. The modern model that places the Sun at the center of the solar system.PTOLEMY – The Greek-Egyptian astronomer who refined the Earth-centered model using "epicycles."
  4. 5. He used Tycho Brahe’s data to calculate the three laws of planetary motion.
  5. 6. The theoretical starting point of the Big Bang: an infinitely hot and dense point.OZONE – A molecule (O3O 3) in the upper atmosphere that protects life on Earth by absorbing harmful UV radiation.
  6. 9. Johannes Kepler discovered that planetary orbits were not perfect circles, but this elongated shape.
  7. 11. The Polish astronomer who first proposed a mathematically detailed Heliocentric model.
  8. 14. The apparent "backward" motion of planets in the sky that confused early astronomers.NEWTON – He explained why planets stay in orbit by identifying the law of universal gravitation.
  9. 17. The astronomer who used redshift to prove the universe is expanding and exists beyond our galaxy.