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Checklist for Geo- vs. Heliocentric Model of Universe 1st Century A.D. Criterion Geocentric Model Success Heliocentric Model Success 1. Common Sense It seems obvious that all objects revolve around the Earth We do not detect any motion, therefore the Earth cannot be moving Yes X Objects appear to be attracted to the center of the Earth, which is considered to be the center of the universe There is no detection of stellar parallax, absence of which is compatible with a static Earth and a stationary observer Yes 5. Predicting planetary orbits Very close agreement- the best yet Yes 6. Retrograde path of planets Explained with epicycles and deferents Yes 7. Simplicity Very complicated – epicycles, deferents, equants and eccentrics X 2. Awareness of motion 3. Falling to the ground 4. Stellar parallax Yes Yes Adapted from Singh, 2004, Table 2 on pages 34-35 It requires a leap of imagination and logic to see that the Earth orbits the Sun We do not detect any motion, which is not easy to explain if the Earth is moving The is no obvious explanation for why objects fall to the ground in a model in which the Earth is not centrally located The Earth moves, so the apparent lack of stellar parallax must be due to huge stellar distances; hopefully parallax would be detected with better equipment Good agreement, but not as good as in the geocentric model A natural consequence of the motion of the Earth and our changing vantage point Very simple – everything follows circles X X ? ? Yes Yes Checklist for Geo- vs. Heliocentric Model of Universe Year 1610, after Galileo’s Observations with the Telescope Criterion Geocentric Model Success Heliocentric Model Success 1. Common Sense It seems obvious that all objects revolve around the Earth We do not detect any motion, therefore the Earth cannot be moving Yes X 3. Falling to the ground Objects appear to be attracted to the center of the Earth, which is considered to be the center of the universe Yes 4. Stellar parallax There is no detection of stellar parallax, absence of which is compatible with a static Earth and a stationary observer Yes 5. Predicting planetary orbits 6. Retrograde path of planets Very close agreement- the best yet Explained with epicycles and deferents Yes 7. Simplicity Very complicated – epicycles, deferents, equants and eccentrics Fails to predict the observed phases Problematic – this model emerges from an Aristotelian view, which also claims that the heavens are perfect Problematic – everything is supposed to orbit the Earth X It still requires a leap of imagination and logic to see that the Earth orbits the Sun Galileo was attempting to explaining why we do not sense the Earth’s motion around the Sun The is no obvious explanation for why objects fall to the ground in a model in which the Earth is not centrally located; only later would Newton explain gravity in this context The Earth moves, so the apparent lack of stellar parallax must be due to huge stellar distances; parallax should be detected with better telescopes Perfect agreement, after Kepler’s contributions A natural consequence of the motion of the Earth and our changing vantage point Very simple – everything follows ellipses Successfully predicts the observed phases No problem – this model makes no claims about the perfection or imperfection of heavenly bodies Yes No problem – this model tolerates multiple centers Yes 2. Awareness of motion 8. Phases of Venus 9. Blemishes on Sun and Moon 10. Moons of Jupiter Yes Yes X X X Adapted from Singh, 2004, Table 3 on pages 68-69 ? X ? Yes Yes Yes Yes Checklist for Geo- vs. Heliocentric Model of Universe After Newton’s Discoveries: Post 1704 Criterion Geocentric Model Success Heliocentric Model Success 1. Common Sense It seems obvious that all objects revolve around the Earth X Yes 2. Awareness of motion We do not detect any motion, therefore the Earth cannot be moving X 3. Falling to the ground Objects appear to be attracted to the center of the Earth, which is considered to be the center of the universe There is no detection of stellar parallax, absence of which is compatible with a static Earth and a stationary observer Very close agreement- the best yet Explained with epicycles and deferents X Newton’s explanation of inertia and gravity can support the notion of objects revolving around each other. Newton’s explanation of inertia aids understanding of why we don’t feel ourselves rotating on the Earth. Newton explained gravity in this context. X Detection of small stellar parallax angles indicates that the Earth is not stationary. Yes X Yes Very complicated – epicycles, deferents, equants and eccentrics Fails to predict the observed phases Problematic – this model emerges from an Aristotelian view, which also claims that the heavens are perfect Problematic – everything is supposed to orbit the Earth X Perfect agreement, after Kepler’s contributions A natural consequence of the motion of the Earth and our changing vantage point Very simple – everything follows ellipses Successfully predicts the observed phases No problem – this model makes no claims about the perfection or imperfection of heavenly bodies Yes No problem – this model tolerates multiple centers Yes 4. Stellar parallax 5. Predicting planetary orbits 6. Retrograde path of planets 7. Simplicity 8. Phases of Venus 9. Blemishes on Sun and Moon 10. Moons of Jupiter X X X X Adapted from Singh, 2004, Table 3 on pages 68-69 Yes Yes Yes Yes Yes Checklist for Big Bang vs. Steady State Model Based Upon Data Available In 1950 Criterion Big Bang Model Success Steady-State Model Success 1. Redshift and the expanding universe Expected from a universe that is created in a dense state and then expands Yes Yes 2. Abundances of the atoms Gamow and colleagues showed that the Big Bang predicts the observed ration of hydrogen to helium, but fails to explain the other atomic abundances The Big Bang expansion would perhaps have pulled apart baby galaxies before they could grow; nevertheless, galaxies did evolve, but no one could explain how Young galaxies existed in the early universe and should therefore be observable only at great distances, which effectively provides a window onto the early universe This echo of the Big Bang should still be detected with sufficiently sensitive equipment The universe is apparently younger than the stars it contains There is no explanation of what caused the creation of the universe ? Expected from an eternal universe that expands, with new matter created in the gaps Matter is created in between the galaxies moving apart, so somehow this material has to be transformed into the atomic abundances that we observe X There is more time and no initial violent expansion; this allows galaxies to develop and die, to be replaced by new galaxies built from created matter Yes ? Young galaxies should appear to be evenly distributed, because they can be born anywhere and at any time out of the matter created in between old galaxies There was no Big Bang so there was no echo, which is why we cannot detect it ? The universe is eternal, so the age of the stars is not a difficulty There is no explanation of the continuous creation of matter in the universe Yes 3. Formation of galaxies 4. Distribution of galaxies 5. Cosmic microwave background (CMB) radiation 6. Age of the universe 7. Creation ? X ? Adapted from Singh, 2004, Table 4 on pages 370-371 ? ? ? Checklist for Big Bang vs. Steady State Model Based Upon Data Available In 1978 Criterion Big Bang Model Success Steady-State Model Success 1. Redshift and the expanding universe Expected from a universe that is created in a dense state and then expands Yes Yes 2. Abundances of the atoms The observed proportions of light atoms (e.g., hydrogen and helium) are very close to the Big Bang prediction by Gamow and colleagues; heavier atoms are produced in the stars The Big Bang expansion might have pulled apart baby galaxies before they could grow; nevertheless, galaxies did evolve, but no one could explain how The distribution of galaxies varies with distance, as shown by Ryle; young galaxies (e.g., quasars) are observed but only at great distances, as they would have existed only just after the Big Bang This echo of the Big Bang was predicted by Gamow, Alpher and Herman, and was found by Penzias and Wilson Recent age measurements show that the objects in the universe are younger than the universe itself, so everything is consistent There is still no explanation of what caused the creation of the universe Yes Expected from an eternal universe that expands, with new matter created in the gaps Cannot really explain the observed abundances of light atoms; heavier atoms are produced in the stars There is more time and no initial violent expansion; this allows galaxies to develop and die, to be replaced by new galaxies built from created matter Young galaxies should be evenly distributed, because they can be born anywhere and at any time out of the matter created in between old galaxies, but this is not backed by observation Yes Yes Cannot explain the observed CMB radiation X Yes There is no evidence for anything older than 20 billion years, yet the universe is supposedly infinitely old ? ? There is still no explanation of the continuous creation of matter in the universe ? 3. Formation of galaxies 4. Distribution of galaxies 5. Cosmic microwave background (CMB) radiation 6. Age of the universe 7. Creation X Yes Adapted from Singh, 2004, Table 4 on pages 370-371 X X