| COPERNICUS | Polish astronomer whose theory on the solar system was published in 1543 (10) |
| NICOLAUSCOPERNICUS | Polish astronomer whose theory of the solar system was published in 1543 (8,10) |
| EVOLUTION | Charles Darwin's theory on the origin of the species (9) |
| SUNDOG | Depicted in a drawing by John Sell Cotman, a parhelion on the solar halo as a result of diffraction of light by ice crystals in the atmosphere (6) |
| SUNSPOT | Dark area on the solar surface |
| PTOLEMY | Astronomer whose theory of Earth at the centre of the universe remained undisputed for some 1,400 years until Nicolaus Copernicus's model in 1543 (7) |
| COPERNICAN | Con a prince in disguise of a Polish astronomer |
| PROSTHESIS | Professional's theory on limb replacement (10) |
| ORRERY | 4th Earl of -; title of Charles Boyle, after whom a clockwork model of the solar system was named (6 |
| PTOLEMAIC | The --- system was a theory which stated that the earth lay at the centre of the universe (9) |
| HAGIA | ___ Sophia, 6th century church in Istanbul converted to a mosque in 1543 and turned into a museum in 1935 (5) |
| NEWTON | Isaac, English physicist whose theory of gravity was shaped by an apple falling on his head (6) |
| HOLBEIN | Hans ?, portraitist and court painter to Henry VIII who died in 1543 |
| BYRD | William, English composer and organist born in 1543 (4) |
| INVENTEDSOURCES | My paper on 'Structure of the Amazon River System' was rejected for containing... |
| DECIMAL | Which system was implemented in Ireland on February 15, 1971? (7) |
| RAYLEIGH | Baron -, inherited title of the co-discoverer of argon whose theory or formula of molecular scattering explains why the sky appears blue (8) |
| EINSTEIN | His theory on gravitational waves was verified in 2016 |
| TYCHO | --- Brahe, Danish astronomer whose work was carried on by Kepler (5) |
| HUBBLE | Edwin, American astronomer whose work led to the discovery that the universe is expanding (6) |
