In its most general sense, twilight is the period of time before sunrise and after sunset, in which the atmosphere is partially illuminated by the sun, being neither totally dark or completely lit. However there are three categories of twilight that are defined by how far the sun is below the horizon.

There was never a filming in Washington Forks Washington was not a filming area for any part of the twilight. It is 2017 and I just went on my own pilgrimage with my husband to all of the filming scenes. We just stayed in Forks Washington for a week. Some people in Forks are manipulating people to believe sites were in films that were never there

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Astronomers recognize three different stages of twilight: civil, nautical and astronomical. All three stages happen twice in a 24-hour period, between day and night and then repeating in reverse order between night and day.

For mid latitudes, civil twilight lasts a bit longer in summer and winter and is a bit shorter in spring and fall. In spring and fall, the sun rises and sets more directly in the east and west. Therefore, it makes a straighter path downward (or upward), reaching the 6 degree mark in a shorter period of time. In summer and winter, the sun arcs across the sky, cutting across the horizon at an angle. This angle is more pronounced in summer, which is why civil twilight lasts the longest in summer. Civil twilight in mid latitudes can last, on average, 1/2 hour.

Compare this to tropical regions. At the equator, the length of civil twilight hardly varies. The sun around the equator makes a path across the sky that cuts cleanly down toward the horizon at sunset in a nearly perpendicular fashion. Therefore, the sun and its rays disappear faster, giving equatorial regions a shorter twilight than higher latitudes. Near the poles, twilight times last much longer.

For polar regions, the summer sun does not get more than 12 degrees below the horizon. Therefore, these regions have nautical twilight all night long, never reaching astronomical twilight or total darkness. For mid latitudes, nautical twilight can last from about 1/2 hour in spring, winter and fall, to about 45 minutes in summer.

For example, some fish use an adaptation called counterillumination to keep from being seen by potential predators. Since light in the twilight zone comes from above, many predators look up to search for prey silhouetted against the surface. Consequently, some small prey fish have rows of organs called photophores along their bellies that emit light similar in intensity and color to the light of the surface water above, making them nearly invisible when viewed from below.

During World War II, U.S. Navy sonar operators looking for enemy submarines were puzzled when sonar images seemed to show the seafloor changing its depth, from about a quarter mile down during the day, to near the surface after dark. What appeared to be a shifting seafloor turned out to be plankton, fish, and other twilight-zone animals making a nightly migration to and from the surface to find food.

Another fast track for carbon into deeper water is through the daily migration of twilight zone animals that feed near the surface at night then bring the carbon in their food back down into the twilight zone during the day.

About 90 percent of the carbon that gets into the twilight zone remains there, but a small percentage of it sinks to down into the deep ocean when animals die or expel carbon-rich fecal matter. Once there, it can remain isolated from the atmosphere for hundreds or even thousands of years.

Open-water fisheries far from land are currently largely unregulated, and we do not yet know enough to ensure that potential extraction of fisheries from the twilight zone would be sustainable. Nevertheless, countries including Norway and Pakistan have already issued licenses to begin fishing the twilight zone. Work began in 2018 under the United Nations Law of the Sea Convention to promote the preservation and sustainable use of marine biodiversity in areas beyond national jurisdiction, but efforts so far have focused on improving the conservation of surface-water fisheries and the genetic resources of the seabed, not of the twilight zone and its important ecosystem services, which are not well understood.

In 2018, WHOI launched an ambitious mission to explore and understand the ocean twilight zone, with initial funding of $35 million from the Audacious Project. The effort is drawing on the expertise of a team of scientists and engineers, combining research, new technologies, and broad public engagement.

By combining these and other new technologies with more traditional methods such as ship-based sonar and net tows, WHOI scientists and engineers hope to rapidly advance our understanding of the twilight zone and the animals living in it. 0852c4b9a8

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