--- title: "Probes, light and measurement: reading the evidence" description: "Twenty-three bilingual articles follow the apparatus, observations and limits behind diffraction, microscopy, spectroscopy, light control and wireless propagation." canonical_url: "https://sandboxphysics.com/stories/probe-evidence/" language: "en" page_type: "story" alternate_languages: zh-CN: "https://sandboxphysics.com/zh/stories/probe-evidence/" last_modified: "2026-10-22" --- [Quantum physics: reading the evidence](https://sandboxphysics.com/stories/quantum-evidence/) 23 articles · 6 reading paths · English and Chinese # Probes, light and measurement: reading the evidence Twenty-three bilingual articles follow the apparatus, observations and limits behind diffraction, microscopy, spectroscopy, light control and wireless propagation. An image, a spectral line and a delayed pulse preserve different information. Start with the measurement you want to understand. Each article follows an apparatus to its observations, then asks which conclusions those observations support. ## Diffraction, phase and surface structure Start with what a detector retains, then ask which structure models those measurements can distinguish. 1. ### [Laue and the Braggs: from spots to a crystal model](https://sandboxphysics.com/stories/probe-evidence/laue-bragg-crystal-inference/) What extra measurements turn a diffraction photograph into evidence for an atomic arrangement? 2. ### [Zernike: a reference wave makes transparent structure visible](https://sandboxphysics.com/stories/probe-evidence/zernike-phase-reference/) Why can a transparent specimen change a wave without making an ordinary image visibly darker? 3. ### [STM: a current contour is not simply a height map](https://sandboxphysics.com/stories/probe-evidence/stm-current-and-surface-inference/) How did tunneling current resolve surface structure, and why can the same surface look different at another bias? 4. ### [Electron diffraction: two experiments, one wavelength test](https://sandboxphysics.com/stories/electron-evidence/electron-diffraction-crystal-records/) How did angular currents and photographic rings turn a matter-wave proposal into a quantitative test? 5. ### [Ruska: making an electron image was only the beginning](https://sandboxphysics.com/stories/electron-evidence/ruska-electron-microscope-resolution/) What separated a magnified grid from a microscope capable of revealing finer structure? 6. ### [Kai Siegbahn: when electron energies began to reveal chemistry](https://sandboxphysics.com/stories/electron-evidence/siegbahn-electron-spectroscopy-chemical-shifts/) What turns a resolved photoelectron peak into evidence about bonding near a surface? ## Interference as a record and a ruler Compare a length reference, a depth record of colour and a reconstructible wavefront. 1. ### [Michelson: a fringe count becomes a length](https://sandboxphysics.com/stories/probe-evidence/michelson-fringes-and-length/) Why did a stable spectral line matter as much as a precise moving mirror? 2. ### [Lippmann: colour stored through the depth of a plate](https://sandboxphysics.com/stories/probe-evidence/lippmann-recorded-colour/) How can a colourless photographic material return a coloured reflection? 3. ### [Gabor: a photograph that preserves a wave reference](https://sandboxphysics.com/stories/probe-evidence/gabor-recording-and-reconstruction/) How can an intensity record later reconstruct the direction and curvature of a wave? ## Controlled light and precision measurement Follow preparation, spectral discrimination, frequency reference, transmission loss and pulse compression. 1. ### [The maser: selected molecules sustained a field](https://sandboxphysics.com/stories/probe-evidence/maser-inversion-and-feedback/) What made a beam of excited molecules a working oscillator rather than just another emitting gas? 2. ### [Laser spectroscopy: a narrow feature inside a broad line](https://sandboxphysics.com/stories/probe-evidence/laser-spectroscopy-doppler-tests/) How did nonlinear laser measurements reveal transitions hidden by thermal motion? 3. ### [Glauber: coherence needs more than visible fringes](https://sandboxphysics.com/stories/probe-evidence/glauber-coherence-and-counting/) What can photon coincidences reveal that a spectrum or interference pattern cannot? 4. ### [Frequency combs: measuring where the ruler starts](https://sandboxphysics.com/stories/probe-evidence/frequency-comb-self-reference/) Why is a known pulse repetition rate insufficient to identify an absolute optical frequency? 5. ### [Kao: guiding light was only half the problem](https://sandboxphysics.com/stories/probe-evidence/kao-loss-and-fibre-communication/) Why did measuring material loss change the prospects for fibre communication? 6. ### [CPA: amplify the energy while the pulse is long](https://sandboxphysics.com/stories/probe-evidence/cpa-stretch-amplify-compress/) How did stretching a pulse make a shorter, more energetic output practical? ## Molecules, forces and ultrafast dynamics Each probe measures a different coordinate. Shared words such as vibration or pulse do not make the instruments equivalent. 1. ### [Raman: the displaced lines moved with the source](https://sandboxphysics.com/stories/probe-evidence/raman-shift-and-molecular-evidence/) What distinguished molecular energy exchange from ordinary scattering or fluorescence? 2. ### [Optical tweezers: holding a bead is not yet measuring force](https://sandboxphysics.com/stories/probe-evidence/optical-tweezers-force-calibration/) What turns a trapped Brownian particle into a quantitative force probe? 3. ### [Attosecond pulses: a broad spectrum still needs a clock](https://sandboxphysics.com/stories/probe-evidence/attosecond-pulses-and-metrology/) How did electron spectra establish a pulse train or an isolated pulse shorter than a femtosecond? 4. ### [Neutrons: separate where atoms are from how they move](https://sandboxphysics.com/stories/probe-evidence/neutrons-structure-and-motion/) What does energy analysis add to a diffraction measurement? ## X-rays: discovery, characteristic radiation and precision spectra Keep transmission images, emitted photons and photoelectrons on separate measurement paths. 1. ### [Röntgen: what a shadow could establish](https://sandboxphysics.com/stories/probe-evidence/rontgen-rays-and-shadow-evidence/) How did a glowing screen become evidence for a new radiation, and what did it leave unexplained? 2. ### [Barkla: why the target material changed the radiation](https://sandboxphysics.com/stories/probe-evidence/barkla-characteristic-x-rays/) How did absorption measurements distinguish characteristic radiation from a scattered copy of the source? 3. ### [Manne Siegbahn: precision changed the atomic diagram](https://sandboxphysics.com/stories/probe-evidence/manne-siegbahn-x-ray-lines/) What did more accurately separated X-ray lines add to the picture of an atom? ## Wireless links and the upper atmosphere Reception establishes a link; interference and pulse delays constrain the atmosphere. 1. ### [Wireless and the ionosphere: reception was only the beginning](https://sandboxphysics.com/stories/probe-evidence/wireless-signals-and-ionosphere/) How did distant reception become a measurement of the upper atmosphere?