A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth’s surface. But whether the alignment produces a total solar eclipse, a partial solar eclipse or an annular solar eclipse depends on several factors, all explained below.
The fact that an eclipse can occur at all is a fluke of celestial mechanics and time. Since the moon formed about 4.5 billion years ago, it has been gradually moving away from Earth (by about 1.6 inches, or 4 centimeters per year). Right now the moon is at the perfect distance to appear in our sky exactly the same size as the sun, and therefore block it out. But this is not always true.

When is the next solar eclipse?

The last solar eclipse was a total eclipse on March 20, 2015. [Related: Spectacular Solar Eclipse Kicks Off Spring]
The next one will be a total solar eclipse on March 9, 2016. According to Geoff Gaherty of Starry Night Education, the moon will be close to perigee for this eclipse, leading to a long period of totality, just over four minutes. The eclipse will begin over the Indian Ocean, and the moon’s shadow first makes landfall on the island of Sumatra, Indonesia.
It then passes over Borneo, Sulawesi and Halmahera, before heading out into the Pacific Ocean, ending north of Hawaii. The partial eclipse will be visible over southern and eastern Asia, northern and western Australia, and much of the Pacific, including Hawaii. The times of maximum eclipse at major cities (Universal Time):

• Darwin — 00:47
• Fairbanks — 03:08
• Guangzhou — 00:58
• Ho Chi Minh — 00:34
• Hong Kong — 00:58
• Honolulu — 03:37
• Jakarta — 00:22
• Kuala Lumpur — 00:24
• Madras — 00:51
• Manila — 00:58
• Phnom Pénh — 00:34
• Singapore — 00:24
• Tokyo — 02:09

On Sept. 1, 2016, an annular eclipse will be visible over most of Africa, the southern Arabian Peninsula, and much of the Indian Ocean. Maximum eclipse occurs in Antarctica at 09:07 UT.