Physical Sciences and Mathematics Commons^™

The World As We Know It: Maps And Atlases From Special Collections, Archives And Special Collections, Luke Meagher

Library Exhibits

Selections of maps and atlases from Sandor Teszler Library’s Special Collections are presented in this exhibit to show how, over time, cartographers have represented the world as we know it.

The Extent, Nature, And Origin Of K And Rb Depletions And Isotopic Fractionations In Earth, The Moon, And Other Planetary Bodies, Nicolas Dauphas, Nicole X. Nie, Marc Blanchard, Zhe J. Zhang, Hao Zeng, Justin Y. Hu, Merlin Meheut, Channon Visscher, Robin Canup, Timo Hopp

Faculty Work Comprehensive List

Moderately volatile elements (MVEs) are depleted and isotopically fractionated in the Moon relative to Earth. To understand how the composition of the Moon was established, we calculate the equilibrium and kinetic isotopic fractionation factors associated with evaporation and condensation processes. We also reassess the levels of depletions of K and Rb in planetary bodies. Highly incompatible element ratios are often assumed to be minimally affected by magmatic processes, but we show that this view is not fully warranted, and we develop approaches to mitigate this issue. The K/U weight ratios of Earth and the Moon are estimated to be 9704 …

Venus Mountain Waves In The Upper Atmosphere Simulated By A Time-Invariant Linear Full-Wave Spectral Model, Michael P. Hickey, Richard L. Walterscheid, Thomas Navarro, Gerald Schubert

Publications

A 2-D spectral full-wave model is described that simulates the generation and propagation of mountain waves over idealized topography in Venus' atmosphere. Modeled temperature perturbations are compared with the Akatsuki observations. Lower atmosphere eddy diffusivity and stability play a major role in the upward propagation of gravity waves from their mountain sources. Two local times (LT) are considered. For LT = 11 h the waves are blocked by a critical level near 100 km altitude, while for LT = 16 h the waves propagate into the thermosphere. As a result of the small scale height in the Venus thermosphere, for …

Determining If Active Galactic Nuclei (Agn) Jets Can Survive The Cold Fronts Of Merger Galaxies, Stephen Walker, Isabelle Wingate

Summer Community of Scholars (RCEU and HCR) Project Proposals

No abstract provided.

Chandra Revisits Wr 48a: Testing Colliding Wind Models In Massive Binaries, Svetozar A. Zhekov, Marc Gagné, Stephen L. Skinner

Earth & Space Sciences Faculty Publications

We present results of new Chandra High-Energy Transmission Grating (HETG) observations (2019 November-December) of the massive Wolf-Rayet binary WR 48a. Analysis of these high-quality data showed that the spectral lines in this massive binary are broadened (full width at half-maximum, FWHM = 1400 km s(-1)) and marginally blueshifted (similar to-100 km s(-1)). A direct modelling of these high-resolution spectra in the framework of the standard colliding stellar wind (CSW) picture provided a very good correspondence between the shape of the theoretical and observed spectra. Also, the theoretical line profiles are in most cases an acceptable representation of the observed ones. …

Corrected Tilt Calculation For Atmospheric Pressure-Induced Seismic Noise, Richard Raspet, Craig J. Hickey, Bipin Koirala

Faculty and Student Publications

In a literature search on the coupling of wind-generated pressure fluctuations into seismic noise, it was noticed that the expression for the angular tilt induced by pressure fluctuations in the seminal paper “A preliminary investigation into the relationship between long-period seismic noise and local fluctuations in the atmospheric pressure” by G. G. Sorrells was only valid at the surface. A search of the literature which cites the Sorrells paper was performed to see if any subsequent research corrected this error, and what effect the error might have on the research. A recent paper by Tanimoto and Wang notes the correct …

Supertranslations At Timelike Infinity, Sumanta Chakraborty, Debodirna Ghosh, Sk Jahanur Hoque, Aniket Khairnar, Amitabh Virmani

Faculty and Student Publications

We propose a definition of asymptotic flatness at timelike infinity in four spacetime dimensions. We present a detailed study of the asymptotic equations of motion and the action of supertranslations on asymptotic fields. We show that the Lee-Wald symplectic form Ω(g, δ1g, δ2g) does not get contributions from future timelike infinity with our boundary conditions. As a result, the “future charges” can be computed on any two-dimensional surface surrounding the sources at timelike infinity. We present expressions for supertranslation and Lorentz charges.

Tess Giants Transiting Giants. I.: A Noninflated Hot Jupiter Orbiting A Massive Subgiant, N. Saunders, S. K. Grunblatt, D. Huber, K. A. Collins, Eric L.N. Jensen, A. Vanderburg, R. Brahm, A. Jordán, N. Espinoza, T. Henning, M. J. Hobson, S. N. Quinn, G. Zhou, R. P. Butler, L. Crause, R. B. Kuhn, K. M. Mogotsi, C. Hellier, R. Angus, S. Hattori, A. Chontos, G. R. Ricker, J. M. Jenkins, P. Tenenbaum, D. W. Latham, S. Seager, R. K. Vanderspek, J. N. Winn, C. Stockdale, R. Cloutier

Physics & Astronomy Faculty Works

While the population of confirmed exoplanets continues to grow, the sample of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant (M_⋆ = 1.53 ± 0.12 M_⊙, R_⋆ = 2.90 ± 0.14 R_⊙) in the Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as a false positive by the TESS Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline …

Toi-1842b: A Transiting Warm Saturn Undergoing Reinflation Around An Evolving Subgiant, R. A. Wittenmyer, J. T. Clark, T. Trifonov, B. C. Addison, D. J. Wright, K. G. Stassun, J. Horner, N. Lowson, J. Kielkopf, S. R. Kane, P. Plavchan, A. Shporer, H. Zhang, B. P. Bowler, M. W. Mengel, J. Okumura, M. Rabus, M. C. Johnson, D. Harbeck, R. Tronsgaard, L. A. Buchhave, K. A. Collins, K. I. Collins, T. Gan, Eric L.N. Jensen, S. B. Howell, E. Furlan, C. L. Gnilka, K. V. Lester, R. A. Matson, N. J. Scott, G. R. Ricker, R. Vanderspek, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, A. Rudat, E. V. Quintana, D. R. Rodriguez, D. A. Caldwell, S. N. Quinn, Z. Essack, L. G. Bouma

Physics & Astronomy Faculty Works

The imminent launch of space telescopes designed to probe the atmospheres of exoplanets has prompted new efforts to prioritize the thousands of transiting planet candidates for follow-up characterization. We report the detection and confirmation of TOI-1842b, a warm Saturn identified by TESS and confirmed with ground-based observations from Minerva-Australis, NRES, and the Las Cumbres Observatory Global Telescope. This planet has a radius of 1.04 (+0.06)/(-0.05) R_J, a mass of 0.214 (+0.040)/(-0.038) M_J, an orbital period of 9.5739 (+0.0002)/(-0.0001) days, and an extremely low density (ρ = 0.252 ± 0.091 g cm⁻³). TOI-1842b has among the …

Validation Of 13 Hot And Potentially Terrestrial Tess Planets, S. Giacalone, C. D. Dressing, C. Hedges, V. B. Kostov, K. A. Collins, Eric L.N. Jensen, D. A. Yahalomi, A. Bieryla, D. R. Ciardi, S. B. Howell, J. Lillo-Box, K. Barkaoui, J. G. Winters, E. Matthews, J. H. Livingston, S. N. Quinn, B. S. Safonov, C. Cadieux, E. Furlan, I. J. M. Crossfield, A. M. Mandell, E. A. Gilbert, E. Kruse, E. V. Quintana, G. R. Ricker, S. Seager, J. N. Winn, J. M. Jenkins, B. Duffy Adkins, D. Baker, T. Barclay, D. Barrado, N. M. Batalha, A. A. Belinski, Z. Benkhaldoun, L. A. Buchhave, L. Cacciapuoti, D. Charbonneau, A. Chontos, J. L. Christiansen, R. Cloutier, K. I. Collins, D. M. Conti, N. Cutting, S. Dixon, R. Doyon, M. El Mufti, E. Esparza-Borges, Z. Essack, A. Fukui, T. Gan, K. Gary, M. Ghachoui, M. Gillon, E. Girardin, A. Glidden, E. J. Gonzales, P. Guerra, E. P. Horch, K. G. Hełminiak, A. W. Howard, D. Huber, J. M. Irwin, G. Isopi, E. Jehin, T. Kagetani, S. R. Kane, K. Kawauchi, J. F. Kielkopf, P. Lewin, L. Luker, M. B. Lund, F. Mallia, S. Mao, B. Massey, R. A. Matson, I. Mireles, M. Mori, F. Murgas, N. Narita, T. O'Dwyer, E. A. Petigura, A. S. Polanski, F. J. Pozuelos, E. Palle, H. Parviainen, P. P. Plavchan, H. M. Relles, P. Robertson, M. E. Rose, P. Rowden, A. Roy, A. B. Savel, J. E. Schlieder, C. Schnaible, R. P. Schwarz, R. Sefako, A. Selezneva, B. Skinner, C. Stockdale, I. A. Strakhov, T.-G. Tan, G. Torres, R. Tronsgaard, J. D. Twicken, D. Vermilion, I. A. Waite, B. Walter, G. Wang, C. Ziegler, Y. Zou

Physics & Astronomy Faculty Works

The James Webb Space Telescope will be able to probe the atmospheres and surface properties of hot, terrestrial planets via emission spectroscopy. We identify 18 potentially terrestrial planet candidates detected by the Transiting Exoplanet Survey Satellite (TESS) that would make ideal targets for these observations. These planet candidates cover a broad range of planet radii (R_p ∼ 0.6–2.0R_⊕) and orbit stars of various magnitudes (K_s = 5.78–10.78, V = 8.4–15.69) and effective temperatures (T_eff ∼ 3000–6000 K). We use ground-based observations collected through the TESS Follow-up Observing Program (TFOP) and two …

Wallaby Pilot Survey: H I Gas Disc Truncation And Star Formation Of Galaxies Falling Into The Hydra I Cluster, T. N. Reynolds, B. Catinella, L. Cortese, Tobias Westmeier, G. R. Meurer, L. Shao, D. Obreschkow, J. Román, L. Verdes-Montenegro, Juan P. Madrid

Physics and Astronomy Faculty Publications and Presentations

We present results from our analysis of the Hydra I cluster observed in neutral atomic hydrogen (HI) as part of the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY). These WALLABY observations cover a 60-square-degree field of view with uniform sensitivity and a spatial resolution of 30 arcsec. We use these wide-field observations to investigate the effect of galaxy environment on HI gas removal and star formation quenching by comparing the properties of cluster, infall and field galaxies extending up to ∼5R200 from the cluster centre. We find a sharp decrease in the HI-detected fraction of infalling galaxies at a …

A New Galactic Wind Model For Cosmological Simulations, Shuiyao Huang

Doctoral Dissertations

The propagation and evolution of cold galactic winds in galactic haloes is crucial to galaxy formation models. However, modelling of this process in hydrodynamic simulations of galaxy formation is over-simplified owing to a lack of numerical resolution and often neglects critical physical processes such as hydrodynamic instabilities and thermal conduction. In this thesis, I propose an analytic model, Physically Evolved Winds (PhEW), that calculates the evolution of individual clouds moving supersonically through a uniform ambient medium. The model reproduces predictions from very high resolution cloud-crushing simulations that include isotropic thermal conduction over a wide range of physical conditions. I also …

Path Integral Complexity And Kasner Singularities, Pawel Caputa, Diptarka Das, Sumit R. Das

Physics and Astronomy Faculty Publications

We explore properties of path integral complexity in field theories on time dependent backgrounds using its dual description in terms of Hartle-Hawking wavefunctions. In particular, we consider boundary theories with time dependent couplings which are dual to Kasner-AdS metrics in the bulk with a time dependent dilaton. We show that holographic path integral complexity decreases as we approach the singularity, consistent with earlier results from holographic complexity conjectures. Furthermore, we find examples where the complexity becomes universal i.e., independent of the Kasner exponents, but the properties of the path integral tensor networks depend sensitively on this data.

The Subaru Hsc Weak Lensing Mass-Observable Scaling Relations Of Spectroscopic Galaxy Groups From The Gama Survey, Divya Rana, Surhud More, Hironao Miyatake, Takahiro Nishimichi, Masahiro Takada, Aaron S G Robotham, Andrew M. Hopkins, Benne Holwerda

Faculty Scholarship

We utilize the galaxy shape catalogue from the first-year data release of the Subaru Hyper Suprime-Cam (HSC) survey to study the dark matter content of galaxy groups in the Universe using weak lensing. We use galaxy groups from the Galaxy Mass and Assembly galaxy survey in approximately 100 sq. degrees of the sky that overlap with the HSC survey as lenses. We restrict our analysis to the 1587 groups with at least five members. We divide these groups into six bins each of group luminosity and group member velocity dispersion and measure the lensing signal with a signal-to-noise ratio of …

Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams

Faculty Publications

Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of …

On The Horizon: Nanosatellite Constellations Will Revolutionize The Internet Of Things (Iot), Diane Janosek

Seattle Journal of Technology, Environmental & Innovation Law

The Internet of Things has experienced exponential growth and use across the globe with 25.1 billion devices currently in use. Until recently, the functionality of the IoT was dependent on secure data flow between internet terrestrial stations and the IoT devices. Now, a new alternative path of data flow is on the horizon.

IoT device manufacturers are now looking to outer space nanosatellite constellations to connect to a different type of internet. This new internet is no longer terrestrial with fiber cables six feet underground but now looking up, literally, 200 to 300 miles above the earth, to communicate, connect …

Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams, Teviet Creighton, Mario C. Diaz, F. Llamas, Soma Mukherjee, Volker Quetschke, W. H. Wang

Physics and Astronomy Faculty Publications and Presentations

Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of …

Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of …

Detection Of Ongoing Mass Loss From Hd 63433c, A Young Mini-Neptune, Michael Zhang, Heather A. Knutson, Lile Wang, Fei Dai, Leonardo A. Dos Santos, Luca Fossati, Gregory W. Henry, David Ehrenreich, Yann Alibert, Sergio Hoyer, Thomas G. Wilson, Andrea Bonfanti

Information Systems and Engineering Management Research Publications

We detect Lyα absorption from the escaping atmosphere of HD 63433c, a R = 2.67R_⊕, P = 20.5 day mini-Neptune orbiting a young (440 Myr) solar analog in the Ursa Major Moving Group. Using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph, we measure a transit depth of 11.1 ± 1.5% in the blue wing and 8 ± 3% in the red. This signal is unlikely to be due to stellar variability, but should be confirmed by an upcoming second transit observation with HST. We do not detect Lyα absorption from the inner planet, a smaller …

Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, Ligo Scientific Collaboration, Virgo Collaboration, Kagra Collaboration, Tiffany Z. Summerscales

Faculty Publications

Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of …

Coupling Between Alfvén Wave And Kelvin–Helmholtz Waves In The Low Latitude Boundary Layer, Eun-Hwa Kim, Jay R. Johnson

Faculty Publications

The Kelvin–Helmholtz (KH) instability of magnetohydrodynamic surface waves at the low latitude boundary layer is examined using both an eigenfrequency analysis and a time-dependent wave simulation. The analysis includes the effects of sheared flow and Alfvén velocity gradient. When the magnetosheath flows are perpendicular to the ambient magnetic field direction, unstable KH waves that propagate obliquely to the sheared flow direction occur at the sheared flow surface when the Alfvén Mach number is higher than an instability threshold. Including a shear transition layer between the magnetosphere and magnetosheath leads to secondary KH waves (driven by the sheared flow) that are …

Comparison Of Maximum-Likelihood Mapping Methods For Gravitational-Wave Backgrounds, Arianna I. Renzini, Joseph D. Romano, Carlo R. Contaldi, Neil Cornish

Physics and Astronomy Faculty Publications and Presentations

Detection of a stochastic background of gravitational waves is likely to occur in the next few years. Beyond searches for the isotropic component of a stochastic gravitational-wave background, there have been various mapping methods proposed to target anisotropic backgrounds. Some of these methods have been applied to data taken by the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo. Specifically, these directional searches have focused on mapping the intensity of the signal on the sky via maximum-likelihood solutions. We compare this intensity mapping approach to a previously proposed, but never employed, amplitude-phase mapping method to understand whether this latter approach may …

Towards A Quantum Notion Of Covariance In Spherically Symmetric Loop Quantum Gravity, Rodolfo Gambini, Javier Olmedo, Jorge Pullin

Faculty Publications

The covariance of loop quantum gravity studies of spherically symmetric space-times has recently been questioned. This is a reasonable worry, given that they are formulated in terms of slicing-dependent variables. We show explicitly that the resulting space-times, obtained from Dirac observables of the quantum theory, are covariant in the usual sense of the way-they preserve the quantum line element-for any gauge that is stationary (in the exterior, if there is a horizon). The construction depends crucially on the details of the Abelianized quantization considered, the satisfaction of the quantum constraints, and the recovery of standard general relativity in the classical …

Towards A Quantum Notion Of Covariance In Spherically Symmetric Loop Quantum Gravity, Rodolfo Gambini, Javier Olmedo, Jorge Pullin

Faculty Publications

The covariance of loop quantum gravity studies of spherically symmetric space-times has recently been questioned. This is a reasonable worry, given that they are formulated in terms of slicing-dependent variables. We show explicitly that the resulting space-times, obtained from Dirac observables of the quantum theory, are covariant in the usual sense of the way-they preserve the quantum line element-for any gauge that is stationary (in the exterior, if there is a horizon). The construction depends crucially on the details of the Abelianized quantization considered, the satisfaction of the quantum constraints, and the recovery of standard general relativity in the classical …

Dr. Jennifer Hoffman, Anit Tyagi

DU Undergraduate Research Journal Archive

An interview with Dr. Jennifer Hoffman.

Dark And Quiet Skies Ii Working Group Reports:, James Lowenthal, Connie Walker, Piero Benvenuti

Astronomy: Faculty Publications

This Report presents the main results of the Conference “Dark and Quiet Skies for Science and Society II” which took place on-line on 3–7 October 2021. This conference was the logical follow-up of the first one, organized as an on-line workshop with the same title on 5–9 October 2020. Both conferences were co-organized by UNOOSA, IAU and the Government of Spain and were well attended. The focus of the second conference was about the feasibility of implementing the recommendations presented by the first one in its extensive report. The main qualifying difference between the first and the second conferences was …

Deep Extragalactic Visible Legacy Survey: Data Release 1 Blended Spectra Search For Candidate Strong Gravitational Lenses, Benne Holwerda, S Knabel, J E. Thorne, S Bellstedt, M Siudek, L J M Davies

Faculty Scholarship

Here, we present a catalogue of blended spectra in Data Release 1 of the Deep Extragalactic VIsible Legacy Survey (DEVILS) on the Anglo-Australian Telescope. Of the 23 197 spectra, 181 showed signs of a blend of redshifts and spectral templates. We examine these blends in detail for signs of either a candidate strong lensing galaxy or a useful overlapping galaxy pair. One of the three DEVILS target fields, COSMOS (D10), is close to complete and it is fully imaged with Hubble Space Telescope Advanced Camera for Surveys, and we visually examine the 57 blended spectra in this field in the …

Design, Construction And Operation Of The Protodune-Sp Liquid Argon Tpc, The Dune Collaboration, A. Abed Abud, B. Abi, R. Acciarri, M. A. Acero, M. R. Adames, G. Adamov, D. Adams, M. Adinolfi, A. Aduszkiewicz, J. Aguilar, Z. Ahmad, J. Ahmed, B. Ali-Mohammadzadeh, T. Alion, K. Allison, S. Alonso Monsalve, M. Alrashed, C. Alt, A. Alton, Roberto Petti, Et. Al.

Faculty Publications

The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, U.S.A. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of 7 × 6 × 7.2 m³. The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. …

Individual Element Sensitivity For Stellar Evolutionary Isochrones, Guy Worthey, Xiang Shi, Tathagata Pal, Hyun-Chul Lee, Baitian Tang

Physics and Astronomy Faculty Publications and Presentations

Stellar evolution calculations with variable abundance ratios were used to gauge the effects on temperatures, luminosities, and lifetimes in various phases. The individual elements C, N, O, Mg, Si, and Fe were included. Most of the effect relevant to integrated light models is contained in the temperature variable, as opposed to the time-scale or luminosity. We derive a recipe for including abundance-sensitive temperature effects that is applicable to existing isochrone grids. The resultant enhanced isochrones are incorporated into composite stellar population models and compared with galaxy data from the Sloan Digital Sky Survey. A severe oxygen–age degeneracy is apparent, 2–3 …

The Meaning Of Dark, Light And Shadows: Inferences In Art, Materiality And Cultural Practices, Frank Prendergast

Book/Book Chapter

Our visual awareness relies on light acting on the eye to perceive materiality and colour. Medieval thought wrestled to articulate and comprehend its nature. The notebooks of Leonardo Da Vinci, for example, included his descriptions to define light and make comparisons so as to differentiate between light and shadow. His focus was on the illumination of surfaces from the perspective of a painter, seeing shadows as ‘the diminution of light by the intervention of an opaque body’ and ‘the counterpart of luminous rays’. In his mind, a shadow ‘stood between light and darkness’, with darkness being ‘the absence of light’. …