Last month's solar flare created a mysterious pulse on Earth that seemed to 'answer' sun's blast

After an unusually long quiet period, the sun unleashed a solar flare on May 17 this year - but scientists are now puzzling over what happened on Earth.

Neutron monitors all round the world lit up in response to the blast for the first time in six years, despite the fact it was an M-Class, or moderate, flare.

The 'answering' pulse shouldn't have happened at all. Now scientists are trying to unravel what happened - and why our planet 'pulsed' in response. Read more