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Its light echoes have aided in mapping the morphology of the immediate vicinity [5] as well as in characterizing dust clouds lying further away but close to the line of sight from Earth. [6] Another example is the SN 1572 supernova observed on Earth in 1572, where in 2008, faint light-echoes were seen on dust in the northern part of the Milky Way.
Human echolocation is the ability of humans to detect objects in their environment by sensing echoes from those objects, by actively creating sounds: for example, by tapping their canes, lightly stomping their foot, snapping their fingers, or making clicking noises with their mouths.
Non-linearity in addition to mode conversion. Two transmitted signals combine to generate a difference frequency, which travels with a plasma wave, and then it is converted back. It could explain amateur VHF/UHF echoes. Hans Rasmussen found echoes delayed by 4.6 seconds at 1296 MHz, [18] and Yurek recorded a 5.75 second delay at 432 MHz. [19]
The Atacama Cosmology Telescope (ACT) was a cosmological millimeter-wave telescope located on Cerro Toco in the Atacama Desert in the north of Chile. [44] ACT made high-sensitivity, arcminute resolution, microwave - wavelength surveys of the sky in order to study the cosmic microwave background radiation (CMB), the relic radiation left by the ...
Radar multipath echoes from a target cause ghosts to appear. Clutter may also originate from multipath echoes from valid targets caused by ground reflection, atmospheric ducting or ionospheric reflection/refraction (e.g., Anomalous propagation). This clutter type is especially bothersome since it appears to move and behave like other normal ...
The waves are sourced by primordial density perturbations, and travel at speed that can be predicted from the baryon density and other cosmological parameters. The total distance that these sound waves can travel before recombination determines a fixed scale, which simply expands with the universe after recombination.
Acoustic location is a method of determining the position of an object or sound source by using sound waves. Location can take place in gases (such as the atmosphere), liquids (such as water), and in solids (such as in the earth). Location can be done actively or passively:
Anomalous propagation refers to false radar echoes usually observed when calm, stable atmospheric conditions, often associated with super refraction in a temperature inversion, direct the radar beam toward the ground. The processing program will then wrongly place the return echoes at the height and distance it would have been in normal conditions.