On Monday, August 21, 2017, a total solar eclipse, frequently referred to as the "Great American Eclipse", is visible within a band across the entire contiguous United States passing from the Pacific to the Atlantic coast. In other countries it will only be visible as a partial eclipse.
A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the sun for a viewer on Earth. A total solar eclipse occurs when the moon's apparent diameter is larger than the sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometers wide.
The last time a total solar eclipse was visible across the entire contiguous United States was during the June 8, 1918, eclipse, and not since the February 1979 eclipse has a total eclipse been visible from anywhere in the mainland United States. The path of totality will touch 14 states, although a partial eclipse will be visible in all fifty states. The total area of the path of totality will be about 16% of the area of the United States, although most of this area is over the ocean and not actually over the United States. The event's shadow began to cover land on the Oregon coast as a partial eclipse at 4:06 p.m. UTC (9:06 a.m. PDT) on August 21, and its land coverage will end later that day as a partial eclipse along the South Carolina coast at about 6:44 p.m. UTC (2:44 p.m. EDT). Visibility as a partial eclipse in Honolulu, Hawaii will begin with sunrise at 4:20 p.m. UTC (6:20 a.m. HST) and end by 5:25 p.m. UTC (7:25 a.m. HST).
There are expected to be logistical problems with the influx of visitors, especially for smaller communities. There have also been problems with the sale of fake eclipse glasses.
Future total solar eclipses will cross the United States in April 2024 (12 states) and August 2045 (10 states), and annular solar eclipses—meaning the apparent size of the Moon is smaller than that of the Sun—will occur in October 2023 (9 states) and June 2048 (9 states).
This eclipse will be the first total solar eclipse visible from the United States since the solar eclipse of July 11, 1991 (which was seen only from part of Hawaii), and the first visible from the contiguous United States since 1979.
Some American scientists and interested amateurs seeking to experience a total eclipse participated in a four-day Atlantic Ocean cruise to view the solar eclipse of July 10, 1972 as it passed near Nova Scotia (side note: there is a reference of this event in the Carly Simon hit song "You're So Vain" in the lyric, "Then you flew your Lear Jet up to Nova Scotia to see the total eclipse of the sun"). Organizers of the cruise advertised in astronomical journals and in planetarium announcements emphasizing the lack of future total eclipses observable in the U.S. until this 2017 event.
The August 2017 eclipse will be the first with a path of totality crossing the Pacific and Atlantic coasts of the U.S. since 1918. Also, its path of totality makes landfall exclusively within the United States, making it the first such eclipse since the country's independence in 1776. (The path of totality of the eclipse of June 13, 1257, was the last to make landfall exclusively on lands currently part of the United States.)
The solar eclipse of August 12, 2045 will have a very similar path of totality over the U.S., about 400 km (250 mi) to the southwest, also crossing the Pacific and Atlantic coasts of the country; however, duration of totality will last over twice as long.
An eclipse of comparable length (up to 3 minutes, 8 seconds, with the longest eclipse being 6 minutes and 54 seconds) occurred over the contiguous United States on March 7, 1970 along the southern portions of the Eastern Seaboard, from Florida to Virginia.
Total eclipse viewing events
During total eclipse the stars and 4 planets will be visible, including the star Regulus close to the Sun. Mars will be 8 degrees to the right, and Venus 34 degrees right. Mercury is 10 degrees left, and Jupiter 51 degrees left.
Craters of the Moon – The National Monument and Preserve will host NASA presentations, evening star parties hosted by the Idaho Falls Astronomical Society, high altitude balloon launches by the USC Astronautical Engineering department and NASA, and presentations by the New Mexico Chapter of the Charlie Bates Solar Astronomy Project.
Kansas City – A 5-mile bicycle ride from downtown KCMO (where totality will only last about 30 seconds) to Macken Park in North Kansas City (where totality will last 1 minute 13 seconds) has been organized by KC Pedal Party Club, a local Meetup group.
Columbia – The COSMO Park and the GANS CREEK Park are open for the eclipse. For the Students of the University of Missouri-Columbia there is a watch party on the campus. and the MU Health care has also released eye safety info.
Lathrop – The city will celebrate its 150th anniversary with an eclipse festival.
Atchison – Benedictine College will host thousands in its football stadium. There will be students from schools from Kansas, Missouri, Nebraska and Oklahoma attending, plus numerous other guests who will hear from, amongst others, astronomers from the Vatican Observatory.
McMinnville – celebrating the eclipse by hosting BLACKOUT 2017, an eclipse viewing event to be held in the city square. In addition to the viewing, a selection of food trucks and musical acts which features The Pink Floyd Appreciation Society band who will be performing Pink Floyd's The Dark Side of the Moon in its entirety prior to the totality event. 
Nashville – offering many special events, including the Music City Eclipse Science & Technology Festival at the Adventure Science Center. The Italian Lights Festival is hosting the largest Eclipse Viewing Party in Nashville, a free NASA-Certified Eclipse Event held at the Bicentennial Mall. Two astrophysicists from NASA's Jet Propulsion Laboratory will emcee the countdown.
In some locations in West Africa and western North Africa, a partial eclipse can be seen just before and during sunset.
In northwestern Europe, the eclipse will only be visible partially, in the evening or at sunset. Only those in Iceland, Ireland, Northern Ireland, Scotland and the Portuguese Azores archipelago will see the eclipse from beginning to end; in the rest of the UK, Norway, the Netherlands, Belgium, France, Spain and Portugal, sunset will occur before the end of the eclipse. In Germany, the beginning of the eclipse will be potentially visible just at sunset only in the extreme northwest of the country. In all regions east of the orange line in the map, the eclipse will not be visible.
A large number of media outlets announced plans to broadcast coverage of the eclipse, including television and internet outlets. NASA announced plans to offer streaming coverage through its NASA TV and NASA Edge outlets, using cameras stationed on the ground along the path of totality, along with cameras on high-altitude balloons, jets, and coverage from the International Space Station; NASA stated that "never before will a celestial event be viewed by so many and explored from so many vantage points—from space, from the air, and from the ground."ABC, CBS, and NBC announced that they would respectively broadcast live television specials to cover the eclipse with correspondents stationed across the path of totality, along with CNN, Fox News Channel, Science, and The Weather Channel. The PBS series Nova will present streaming coverage on Facebook hosted by Miles O'Brien, and air a special episode chronicling the event—"Eclipse Over America"—later in the day (which will mark the fastest production turnaround time in Nova history).
In the months leading to the eclipse, counterfeits of light-filtering glasses for safe viewing of solar eclipses began proliferating, leading to concerns regarding safety. To be effective, eclipse glasses must filter visible, ultraviolet, and infrared light. The eye's retina has no pain receptors, and thus damage could occur without a person being aware.
The American Astronomical Society (AAS) stated products meeting the ISO 12312-2 standard would avoid risk damage, and issued a list of "reputable" vendors of eclipse glasses. The organization warned against products claiming ISO certification, even claiming this exact number, but not actually tested by an accredited laboratory, or bearing incomplete certification information. Another problem was counterfeits of reputable vendors' products, even claiming the company's name as in the above external image for American Paper Optics (which published information detailing the differences between its glasses and counterfeits).
The AAS noted determining whether an eclipse viewer was safe required a spectrophotometer and lab equipment, but often the user should see little through the filter except for the Sun, sunlight reflected off shiny metal, or intense light sources such as an LED flashlight.
On July 27, 2017, Amazon required all eclipse viewing products sold on its website have a submission of origin and safety information, and proof of an accredited ISO certification. In mid-August 2017, Amazon recalled and pulled listings for eclipse viewing glasses that "may not comply with industry standards", and refunded customers who had purchased them.
August 21, 2017 total solar eclipse
Umbra (black oval), penumbra (concentric shaded ovals), and path of totality (red).
This video features several visualizations of the event.
During a total solar eclipse, the solar corona can be seen by the naked eye.
2017 eclipse as seen from Seattle
Officials inside and near the path of totality have been planning – sometimes for years – for the sudden influx of people. Smaller towns struggled to arrange viewing sites and logistics for what could be either a tourism boom or a disaster.
In the American West, illegal camping is a major concern, including near cities like Jackson Hole, Wyoming. Idaho's Office of Emergency Management noted that Idaho was a prime viewing state, and advised jurisdictions to prepare for increased loads on their services; nearly every hotel and motel room, campground, and in some cases backyards for nearly 100 miles (160 km) miles north and south of the path of totality had been reserved several months if not years in advance. The state anticipates up to 500,000 visitors to join its 1.6 million residents.
Oregon has deployed six National Guard aircraft and 150 soldiers inasmuch as the influx of visitors coincides with the state's fire season. Hospital staffing, and supplies of blood and anti–snake bite antidote, have been augmented along the totality line.
There have been widespread traffic problems across the United States. Michael Zeiler, an eclipse cartographer estimated that between 1.85 and 7.4 million people will travel to the path of the eclipse.
In North Carolina, the Department of Transportation added cameras, message boards and safety patrols in the counties where the total eclipse would take place, as well as stopping road work. The department warned that due to "unprecedented" traffic, ordinary activities requiring driving might be difficult, and people were advised to act as if there were snow. In Oregon, an estimated one million people are expected to arrive, with traffic becoming so bad in Madras that the Oregon National Guard was called in. In Idaho, traffic more than doubled along I-15, however, traffic is only slightly slowed down overall. Planning for the eclipse began more than a year ago, and state officials planned to have a patrol stationed every 15 miles between Shelley and the Utah border. In Wyoming, on Saturday, traffic increased 18 percent over a five-year average, with an additional 131,000 vehicles on the road.
Impact on solar power
The eclipse is likely to cause a reduction of solar power generation where the moon shadow covers any solar panel. The North American Electric Reliability Corporation attempts to measure the impact of this eclipse,  and aims to predict minor impacts. In California, solar power may decrease by 4–6,000 megawatts at 70 MW/minute, and then ramp up by 90 MW/minute as the shadow passes. CAISO's typical ramp rate is 29 megawatts per minute. Around 4 GW mainly in North Carolina and Georgia are expected to be 90% obscured. The Solar eclipse of March 20, 2015 caused manageable solar power decreases in Europe; in Germany, solar power dropped from 14 GW to 7 GW, of a 38 GW solar power capacity.
This solar eclipse is a part of Saros cycle 145, repeating every 18 years, 11 days, containing 77 events. The series started with partial solar eclipse on January 4, 1639, and reached a first annular eclipse on June 6, 1891. It was a hybrid event on June 17, 1909, and total eclipses from June 29, 1927, through September 9, 2648. The series ends at member 77 as a partial eclipse on April 17, 3009. The longest eclipse will occur on June 25, 2522, with a maximum duration of totality of 7 minutes, 12 seconds. 
The metonic series repeats eclipses every 19 years (6939.69 days), lasting about 5 cycles. Eclipses occur in nearly the same calendar date. In addition the octon subseries repeats 1/5 of that or every 3.8 years (1387.94 days).
21 eclipse events, progressing from north to south between June 10, 1964, and August 21, 2036
^"Thousands Go West for a Total Solar Eclipse Tomorrow; Data May Aid Energy Research Partial Eclipse for New York Best Types of Film Image of Sun on Screen", The New York Times February 25, 1979. p. 26.
^"2016 Long-Term Reliability Assessment"(PDF). North American Electric Reliability Corporation. December 2016. p. 70. Retrieved April 18, 2017. causes substantial effects to wide-scale solar generation within a very short amount of time. The output generated by PV/solar systems will be either diminished or drastically reduced within the window of this event. Sudden widespread diminishing of solar irradiance may heavily affect areas with large amounts of utility scale PV energy installations or behind-the-meter DERs.