question: When it's sunny and hot, why does the image of far objects get warped? And also, why asphalt in the distance looks like a water surface/mirror?
comment: Asphalt heats up very quickly. This means the air right above it also becomes very hot. Hot air rises but once it's not close to the asphalt anymore it cools off quickly. The hot air coming off the asphalt and the cooler air immediately above it have different densities because of the different temperatures, and they refract light differently. From hottest to coolest this creates a lens-like effect. Close to the hot surface it can refract light to look like there's a reflective pool of water. Since the air is constantly in motion and hot and cooler air constantly mix and flow (convection) this means looking through that air can produce a shimmering "warping" effect.
passages: Air temperature variations close to the surface can give rise to other optical phenomena, such as mirages and Fata Morgana. Most commonly, air heated by a hot road on a sunny day deflects light approaching at a shallow angle towards a viewer. This makes the road appear reflecting, giving an illusion of water covering the road.
  
  Section::::Water waves.
   Looming and similar refraction phenomena
  
  While mirages are the best known atmospheric refraction phenomena, looming and similar refraction phenomena do not produce mirages. Mirages show an extra image or images of the miraged object, while looming, towering, stooping, and sinking do not. No inverted image is present in those phenomena either. Depending on atmospheric conditions, the objects can appear to be elevated or lowered, stretched or stooped. These phenomena can occur together, changing the appearance of different parts of the objects in different ways. Sometimes these phenomena can occur together with a true mirage.
  
  Section::::Looming.
   Fata Morgana mirages are most common in polar regions, especially over large sheets of ice with a uniform low temperature, but they can be observed almost anywhere. In polar regions, a Fata Morgana may be observed on cold days; in desert areas and over oceans and lakes, a Fata Morgana may be observed on hot days. For a Fata Morgana, temperature inversion has to be strong enough that light rays' curvatures within the inversion are stronger than the curvature of the Earth.
   Temperature variations in the air can also cause refraction of light. This can be seen as a heat haze when hot and cold air is mixed e.g. over a fire, in engine exhaust, or when opening a window on a cold day. This makes objects viewed through the mixed air appear to shimmer or move around randomly as the hot and cold air moves. This effect is also visible from normal variations in air temperature during a sunny day when using high magnification telephoto lenses and is often limiting the image quality in these cases.
   Inferior mirage of astronomical objects is the most common mirage. Inferior mirage occurs when the surface of the Earth or the oceans produces a layer of hot air of lower density, just at the surface. There are two images, the inverted one and the erect one, in inferior mirage. They both are displaced from the geometric direction to the actual object. While the erect image is setting, the inverted image appears to be rising from the surface.
   BULLET::::- "Gloss" (at least six types of "gloss" may be observed depending upon the character of the surface and the spatial (directional) distribution of the reflected light.)
  
  BULLET::::- "Specular gloss"
  
  BULLET::::- "Distinctness of image gloss"
  
  BULLET::::- "Sheen"
  
  BULLET::::- "Reflection haze, H" (for a specified specular angle), the ratio of (light) flux reflected at a specified angle (or angles) from the specular direction to the flux similarly reflected at the specular angle by a specified gloss standard.
  
  Transmissive objects 
  
  BULLET::::- "Transmittance, T"
  
  BULLET::::- "Haze" (turbidity)
  
  BULLET::::- "Clarity"
  
  Section::::See also.
  
  BULLET::::- Reflection (physics)
  
  BULLET::::- Shading
  
  BULLET::::- Transmittance
  
  Section::::References.
   Astronomical or celestial refraction causes astronomical objects to appear higher above the horizon than they actually are. Terrestrial refraction usually causes terrestrial objects to appear higher than they actually are, although in the afternoon when the air near the ground is heated, the rays can curve upward making objects appear lower than they actually are.
  
  Refraction not only affects visible light rays, but all electromagnetic radiation, although in varying degrees. For example, in the visible spectrum, blue is more affected than red. This may cause astronomical objects to appear dispersed into a spectrum in high-resolution images.
   Fata Morgana mirages tremendously distort the object or objects which they are based on, such that the object often appears to be very unusual, and may even be transformed in such a way that it is completely unrecognizable. A Fata Morgana can be seen on land or at sea, in polar regions or in deserts. This kind of mirage can involve almost any kind of distant object, including such things as boats, islands, and coastline.
   BULLET::::- Mirages. These are optical phenomena in which light rays are bent due to thermal variations in the refractive index of air, producing displaced or heavily distorted images of distant objects. Other optical phenomena associated with this include the Novaya Zemlya effect, where the Sun appears to rise earlier or set later than predicted with a distorted shape. A spectacular form of refraction, called the Fata Morgana, occurs with a temperature inversion, in which objects on the horizon or even beyond the horizon (e.g. islands, cliffs, ships, and icebergs) appear elongated and elevated, like "fairy tale castles".
   Towering and stooping are more complex forms of atmospheric refraction than looming and sinking. While looming and sinking change the apparent elevation of an object, towering and stooping change the apparent shape of the object itself. With towering, objects appear stretched; with stooping, objects seem to be shortened. The apparent stretching and shortening of the objects are not symmetrical and depends on the thermal profile of the atmosphere. The curvature of the rays changes more rapidly in some places because the thermal profile is curved.
  
  Section::::Image example and explanation.
   The term "specular" means that light is perfectly reflected in a mirror-like way from the light source to the viewer. Specular reflection is visible only where the surface normal is oriented precisely halfway between the direction of incoming light and the direction of the viewer; this is called the half-angle direction because it bisects (divides into halves) the angle between the incoming light and the viewer. Thus, a specularly reflecting surface would show a specular highlight as the perfectly sharp reflected image of a light source. However, many shiny objects show blurred specular highlights.
   One typically sees further along the Earth's curved surface than a simple geometric calculation allows for because of refraction error. If the ground, or water, surface is colder than the air above it, a cold, dense layer of air forms close to the surface, causing light to be refracted downward as it travels, and therefore, to some extent, to go around the curvature of the Earth. The reverse happens if the ground is hotter than the air above it, as often happens in deserts, producing mirages. As an approximate compensation for refraction, surveyors measuring distances longer than 100 meters subtract 14% from the calculated curvature error and ensure lines of sight are at least 1.5 meters from the ground, to reduce random errors created by refraction.
   In the first fourteen frames, elements of the Fata Morgana mirage display alternations of compressed and stretched zones. The last two frames were photographed a few hours later, around sunset time. At that point in time, the air was cooler while the ocean was probably a little bit warmer, which caused the thermal inversion to be not as extreme as it was few hours before. A mirage was still present at that point, but it was not so complex as a few hours before sunset: the mirage was no longer a Fata Morgana, but instead had become a simple superior mirage.
   Superior mirages can have a striking effect due to the Earth's curvature. Were the Earth flat, light rays that bend down would soon hit the ground and only nearby objects would be affected. Since Earth is round, if their downward bending curve is about the same as the curvature of the Earth, light rays can travel large distances, perhaps from beyond the horizon. This was observed and documented for the first time in 1596, when a ship under the command of Willem Barentsz in search of the Northeast passage became stuck in the ice at Novaya Zemlya. The crew was forced to endure the polar winter there. They saw their midwinter night come to an end with the rise of a distorted Sun about two weeks earlier than expected. It was not until the 20th century that science could explain the reason: the real Sun had still been below the horizon, but its light rays followed the curvature of the Earth. This effect is often called a Novaya Zemlya mirage. For every the light rays can travel parallel to the Earth's surface, the Sun will appear 1° higher on the horizon. The inversion layer must have just the right temperature gradient over the whole distance to make this possible.
   Looming is the most noticeable and most often observed of these refraction phenomena. It is an abnormally large refraction of the object that increases the apparent elevation of the distant objects and sometimes allows an observer to see objects that are located below the horizon under normal conditions. One of the most famous looming observations was made by William Latham in 1798, who wrote:
  
  Thomas Jefferson noted the phenomenon of looming in his book "Notes on the State of Virginia":
   Defined as the gloss at grazing angles of incidence and viewing
  
  BULLET::::- Contrast gloss – the perceived brightness of specularly and diffusely reflecting areas
  
  Defined as the ratio of the specularly reflected light to that diffusely reflected normal to the surface;
  
  BULLET::::- Absence of bloom – the perceived cloudiness in reflections near the specular direction
  
  Defined as a measure of the absence of haze or a milky appearance adjacent to the specularly reflected light: haze is the inverse of absence-of-bloom
  
  BULLET::::- Distinctness of image gloss – identified by the distinctness of images reflected in surfaces
   Section::::Tessellated Pavement, Eaglehawk Neck, Tasmania.
  
  The most well known example of a tessellated pavement is the Tessellated Pavement that is found at Lufra, Eaglehawk Neck on the Tasman Peninsula of Tasmania. This tessellated pavement consists of a marine platform on the shore of Pirates Bay, Tasmania. This example consists of two types of formations: a "pan" formation and a "loaf" formation.
   Superior mirages are quite common in polar regions, especially over large sheets of ice that have a uniform low temperature. Superior mirages also occur at more moderate latitudes, although in those cases they are weaker and tend to be less smooth and stable. For example, a distant shoreline may appear to "tower" and look higher (and, thus, perhaps closer) than it really is. Because of the turbulence, there appear to be dancing spikes and towers. This type of mirage is also called the Fata Morgana or "hafgerdingar" in the Icelandic language.
   Light is an important factor for identifying the physical texture because it can affect how a surface is being viewed. Strong lights on a smooth surface can obscure the readability of a drawing or photograph, whilst they can create strong contrasts in a highly textural surface such as river rocks, sand, etc.
  
  Section::::Visual texture.
   Other famous observations that were called "mirages" may actually be referring to looming. One of those was described in "Scientific American" on August 25, 1894 as "a remarkable mirage seen by the citizens of Buffalo, New York". Such looming—sometimes with apparent magnification of opposite shores—have been reported over the Great Lakes. Canadian shorelines have been observed from Rochester, New York, across Lake Ontario, and from Cleveland across Lake Erie. The landforms over distant, normally beyond the horizon, were sometimes perceived as away.
   If the vertical temperature gradient is +12.9 °C per 100 meters (where the positive sign means temperature gets hotter as one goes higher) then horizontal light rays will just follow the curvature of the Earth, and the horizon will appear flat. If the gradient is less (as it almost always is) the rays are not bent enough and get lost in space, which is the normal situation of a spherical, convex "horizon".
  
  In some situations, distant objects can get elevated or lowered, stretched or shortened with no mirage involved.
  
  Section::::Superior mirage.:Fata Morgana.
   Heat haze, also called heat shimmer, refers to the inferior mirage experienced when viewing objects through a layer of heated air; for example, viewing objects across hot asphalt or through the exhaust gases produced by jet engines. When appearing on roads due to the hot asphalt, it is often referred to as a highway mirage.
   On tarmac roads it may look as if water, or even oil, has been spilled. These kinds of inferior mirages are often called "desert mirages" or "highway mirages". Both sand and tarmac can become very hot when exposed to the sun, easily being more than 10 °C hotter than the air one meter above, enough to create conditions suitable for the formation of the mirage.
  
  Heat haze is not related to the atmospheric phenomenon of haze.
  
  Section::::Superior mirage.
   In the 1930s work by A. H. Pfund, suggested that although specular shininess is the basic (objective) evidence of gloss, actual surface glossy appearance (subjective) relates to the contrast between specular shininess and the diffuse light of the surrounding surface area (now called “contrast gloss” or “luster”).
   Sinking is the opposite of looming. In sinking, stationary objects that are normally seen above the horizon appear to be lowered, or may even disappear below the horizon. In looming, the curvature of the rays is increasing, while sinking produces the opposite effect. In general, looming is more noticeable than sinking because objects that appear to grow stand out more than those that appear to shrink.
  
  Section::::Towering and stooping.
  