What primary physical constraint inherent in large lenses drove Isaac Newton toward the reflecting telescope around 1668?

Answer

They could not be made perfectly achromatic and would sag

The evolution toward the reflecting telescope, constructed practically by Sir Isaac Newton around 1668, was motivated by overcoming fundamental physical limitations associated with large refractors. Lenses, by their nature as refracting elements, struggle to focus all colors of light perfectly onto a single point, resulting in chromatic aberration, a problem difficult to fully correct even with advanced grinding techniques. More critically, constructing very large objective lenses presented a severe structural challenge: glass, even when precisely shaped, would inevitably sag under its own immense weight, distorting the optical surface. By substituting a curved mirror for the objective lens, Newton completely bypassed the chromatic aberration problem and eliminated the sag issue associated with massive glass elements, allowing for larger light-gathering surfaces.

What primary physical constraint inherent in large lenses drove Isaac Newton toward the reflecting telescope around 1668?

Related Questions

What was the initial magnification range of early Dutch spectacle-makers' devices?In what year did Galileo Galilei receive word of the Dutch perspective glass?What specific observation in the Moon revealed celestial imperfection to Galileo?What implication did the discovery of Jupiter’s moons have for the geocentric model?How did Galileo's observation of Venus support the Copernican heliocentric system?What major characteristic of the Milky Way was revealed by the telescope?What methodological shift did Galileo’s work establish in astronomy after 1610?What specific optical feature made early Galilean refractors problematic for faint astronomical objects?How did the Keplerian Refractor, proposed around 1611, improve upon the Galilean design?What primary physical constraint inherent in large lenses drove Isaac Newton toward the reflecting telescope around 1668?Which observer finally demonstrated stellar parallax in 1838, confirming Earth's motion?What key methodological difference existed between Galileo's approach and later Royal Society astronomers?
inventionHistoryastronomytelescopescience