We are lucky that by pure chance the Sun is both approximately 400 times larger and 400 times further away than the Moon. This means that whenever the Moon passes in front of the Sun from our view point we have one of the most incredible sights in nature known as a total solar eclipse. The Moon’s orbit is inclined by around 5 degrees to the Earth’s orbit around the Sun, resulting in a total eclipse once every 18 months or so. If the Moon’s orbit were on the exact plane as the Earth’s orbit around the Sun then the moon would cover the Sun every new moon and we would have an eclipse once a month.
You may have seen on the news recently that there is a total eclipse of the Sun this month that will sweep across the USA from the West coast to the East. It will actually begin over the Pacific Ocean before passing over the coast of Oregon and across the USA. The map below shows the path of the total eclipse and the amount of partial eclipse visible across the USA. You can see the band of the shadow moves across the country, where the eclipse will be visible at different times. At locations North or South of the path of totality there will be a partial eclipse, where not all of the Sun is covered by the Moon. The further away from the path of totality the less of the Sun will be covered.
A slight partial eclipse, where the moon only cover a small section of the sun, will be visible in the UK. Please DO NOT LOOK DIRECTLY AT THE SUN AS IT WILL DAMAGE YOUR EYES. LOOKING DIRECTLY THROUGH BINOCULARS OR A TELESCOPE IS LIKELY TO CAUSE BLINDNESS. If you don’t have specialist equipment you can project the sun – the Society for Popular Astronomy has a solar observing guide http://www.popastro.com/solar/solarobserving/index.php
If you do happen to be in the USA on the 21st August, then you may be lucky enough to catch sight of this amazing spectacle. Should you decide to try and see the partial eclipse in the UK them make sure you read the guide to observing the sun, do not risk your eyesight with direct vision.