Construct · 2 fields · 2 citations

lens: one construct, many systems

One name. One construct. Different systems. One map.

● invariant · one construct, three systems Nearest construct by meaning·not indexed
Einstein's "lens-like action" carried the focusing idea to mass bending lightlens2 SYSTEMSGravitational lensEINSTEIN · 1936Optical lensREFRACTION · GLASS

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1936Gravitational lens2017Optical lens
2026

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Astrophysics

Mass that bends and focuses starlight

In astrophysics, a gravitational lens is a massive body, such as a galaxy or a cluster, whose gravity bends the paths of light passing nearby, focusing and distorting the image of a more distant source into arcs, rings, or multiple copies. Einstein's 1936 Lens-like action of a star by the deviation of light in the gravitational field worked out the effect and named it directly after the optical device. It is the same construct, something that bends light to form an image, achieved not by refraction in glass or tissue but by the curvature of spacetime around mass, and it is read off in deflection angles and magnification rather than focal length.[1]

Unit
The light-bending deflection angle and image magnification set by the mass
Recovery means
Not applicable
Measured by
Inferred from deflection angles, the Einstein-ring radius, multiple images, and the magnification of the background source

Optics

Shaped glass that refracts light to an image

In optics, a lens is a shaped piece of transparent material, curved so that it refracts light to converge or diverge it and form an image, the workhorse of spectacles, cameras, microscopes, and telescopes. Hecht's Optics develops how a lens's curvature and refractive index set its focal length and govern image formation and aberration. The referent is a manufactured refracting element defined by focal length and aperture; it is the same image-forming construct the eye realises in living tissue and that gravity mimics on cosmic scales.[2]

Unit
The focal length and aperture of the refracting element
Recovery means
Not applicable
Measured by
Characterised by focal length, f-number, and the aberrations of the image it forms

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Nearby constructs

astigmatism2 fields · 2 citationsinvariant · one construct, two systemsaberration4 fields · 4 citationsjingle · one word, four constructsaccommodation4 fields · 5 citationsjingle · one word, four constructs

References

  1. Einstein, A. (1936). Lens-like action of a star by the deviation of light in the gravitational field. Science, 84(2188), 506–507. https://doi.org/10.1126/science.84.2188.506
  2. Hecht, E. (2017). Optics (5th ed.). Pearson. ISBN 9780133977226

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