On Wednesday evening, millions of Europeans will experience a celestial treat: a solar eclipse. A wide band of north and central Spain, plus a sliver of Portugal and parts of Greenland and Iceland will experience a rare total eclipse. The light of the setting sun will be virtually blocked out across much of western Europe, including the UK, France, Belgium, Switzerland and northern Italy.<\/p>\n
What is a solar eclipse?Children use special glasses to watch the solar eclipse in North Sumatra, Indonesia, in 2019. Photograph: Anadolu Agency\/Getty Images<\/p>\n
A solar eclipse occurs when the moon passes directly between the Earth and the sun, resulting in the moon casting a shadow on the Earth.<\/p>\n
Viewers see a total solar eclipse when the sun\u2019s light is fully blocked by the moon \u2013 meaning they are in the umbra of the moon\u2019s shadow \u2013 and a partial solar eclipse when only part of the light is blocked, meaning they are in the penumbra of the moon\u2019s shadow.<\/p>\n
\u201cThe moon and sun have to line up precisely for the moon to fully cover the sun and for you to see a total eclipse,\u201d said Dr Megan Argo, a reader in astrophysics at the University of Lancashire and the vice-president of the Society for Popular Astronomy. \u201cBecause the orbit of the moon is slightly tilted, it doesn\u2019t appear to cross the disc of the sun from our perspective each time it orbits the Earth.\u201d<\/p>\n
Whether viewers see a total or partial eclipse \u2013 or no eclipse at all \u2013 depends upon their location on the Earth\u2019s surface. \u201cYou have to be right in the middle of the shadow to see a total eclipse, and that is quite a narrow track on the Earth\u2019s surface,\u201d said Argo.<\/p>\n
Solar eclipse map<\/a>How rare is Wednesday\u2019s event?<\/p>\n This total eclipse will be the first in mainland Europe in two decades. The last event of this kind visible from the UK occurred in 1999, when parts of Devon and Cornwall were in the path of totality. The next total solar eclipse visible in the UK is not due to occur until 2090.<\/p>\n An information panel displays measures on how to safely view an upcoming solar eclipse on a street in Palma de Mallorca. Photograph: Jaime Reina\/AFP\/Getty Images<\/p>\n While the country will only experience a partial solar eclipse on Wednesday, experts are enthusiastic, noting the next comparable event visible in the UK will be in 2081. \u201cThis is the best [solar] eclipse that we\u2019ve had in the UK since 1999. There have been a few other partial eclipses, but not one that\u2019s this deep, which has this percentage of the sun eclipsed by the moon,\u201d said Argo.<\/p>\n When will it take place?<\/p>\n For those watching in Spain under the path of the total eclipse, it will peak between 20.26 and 20.33 local time, depending on location, shortly before sunset.<\/p>\n A map showing the arc of the total eclipse across Spain<\/a><\/p>\n In the UK, the Royal Observatory Greenwich<\/a> calculates that the partial eclipse will begin for viewers in London at 18.17 BST, before reaching its maximum at 19.13 BST and ending at 20.06 BST. Dr Carys Herbert, an astronomer at Royal Observatory Greenwich, said people in Cornwall would experience about 96% coverage, while people in the west of Scotland would experience 93% coverage and people in London would see about 92% coverage.<\/p>\n Dr Carys Herbert demonstrates wearing solar eclipse glasses outside Royal Observatory Greenwich. Photograph: Jordan Pettitt\/PA<\/p>\n \u201cIt will be low on the horizon,\u201d said Herbert. \u201cSo anyone who is wanting to go and see it should probably find a spot with a nice view to the western horizon without any buildings or trees in the way. Everyone in the UK is going to have a very good eclipse.\u201d<\/p>\n How can I view the eclipse safely?<\/p>\n Experts have stressed it is crucial not to look at the sun with the naked eye, or to rely on sunglasses, noting it can cause permanent eye damage. Instead, they recommend buying special eclipse glasses.<\/p>\n During a 2017 eclipse, Donald Trump was widely mocked for looking up and pointing at the sky during the solar eclipse<\/a> without glasses, despite repeated warnings that doing so can lead to permanent eye damage<\/a>. He later donned eclipse glasses.<\/p>\n Donald Trump points to the sun as he arrives to view the solar eclipse at the White House in Washington. Photograph: Andrew Harnik\/AP<\/p>\n \u201cIf you don\u2019t have eclipse glasses, you can use a colander or something to create a pinhole projector,\u201d said Herbert. This is a way to see the eclipse indirectly \u2013 do not look at the sun through the colander but project the light on to card or paper.<\/p>\n Assuming that clouds don\u2019t block the view, the spectacle will resemble a growing bite being taken out of the sun\u2019s disc as the moon moves in front of it, until only a slim crescent is visible. As the moon moves away, the sun will gradually return in its full glory.<\/p>\n Why are scientists excited?<\/p>\n \u201cThere are scientific things that we can do during eclipses,\u201d said Argo, as it offers one way to study the sun\u2019s outer atmosphere \u2013 or solar corona. \u201cIt can tell us a lot about the chemistry of the sun\u2019s atmosphere, [and] how the atmosphere varies depending on the sunspot cycle and the solar activity cycle, which goes through an 11-year cycle,\u201d she said.<\/p>\n