Solar eclipse science – what exactly is a total solar eclipse, what happens and how rare is it?
THE next total solar eclipse isn't until August 2026, until then we will have annular solar eclipses to keep us entertained until the main event.
But what is a total eclipse of the sun and what's the science behind the event? We've got all the details for you...
What is a total solar eclipse?
A total solar eclipse is when the sun is entirely blocked out by the moon.
The sun is exactly 400 times bigger than the moon but it is also 400 times further away from the Earth.
These are the perfect ratios for the moon to completely eclipse the sun, provided the alignment on the Earth's surface is exactly right.
If an eclipse is "total" i.e. the sun is completely covered when viewed from any point on the Earth, it is referred to as a "total solar eclipse", even though from other places, it may only be partial.
How rare are total solar eclipse?
Total solar eclipses are not that rare, and occur roughly once ever 18 months.
However it is much less common for a total eclipse of the sun to be visible from the Earth's surface.
Recently a Belgian scientist Jean Meeus calculated that the average frequency of a total solar eclipse for any given point on the Earth's surface is once in 375 years.
What was the Great American Eclipse, August 21, 2017?
The total solar eclipse is the first over any part of the US since 1979 - and the first over the entire continent since 1918 - but it will be travelling so fast you couldn't even chase it in a supersonic jet.
It first entered the US on the West Coast over Oregon on August 21 of 2017, from 10am local time.
The eclipse then sped in a 67-mile path south east across the country at an astonishing 1,700mph.
Only lasting for around an hour-and-a-half, it left the US on the East Coast near Charleston, South Carolina, at 2.48pm local time where it was not visible from land again.
What was eclipse over South America, July 2, 2019?
Two years later, another solar eclipse over the Southern Hemisphere darkened skies over the South Pacific and parts of South America.
A limited number of countries will see the Moon pass in front of the Sun, but it won't be visible for those in the UK.
The countries in best view to see the eclipse are Chile, Argentina and British Overseas Territory of Pitcairn Island.
The earliest places to see the eclipse will be on the ocean east of New Zealand.
For those who can't see the event in person, NASA will live stream the phenomenon for free in partnership with the San Francisco Exploratorium.
NASA said: “NASA has partnered with the Exploratorium in San Francisco to bring live views to people across the world of a total solar eclipse, occurring Tuesday, July 2, over South America.
“The eclipse will only be visible directly to observers within the path of totality, which stretches across parts of Chile and Argentina."
What are the conspiracy theories around the solar eclipse?
Online conspiracy theorists went wild in the run-up to the "Great American Eclipse" with some suggesting that the world could come to an end.
Some doom-mongers issued a warning about the possibility of a secret planet called Nibiru smashing into Earth.
According to the conspiracy theory, when this gigantic alien world - whose existence has never been confirmed by scientists - crashes into Earth, it's be the end of humanity.
A Christian numerologist called David Meade said the eclipse was a warning sign.