The 11-year solar cycle is tracked by NASA, learn how they do it. <br /><br />Credit: NASA Goddard Space Flight Center<br />-<br /><br />More at: https://www.space.com<br />Facebook → https://www.facebook.com/space.com<br />Instagram → https://instagram.com/cyclingweeklyma...<br />Twitter → http://twitter.com/spacedotcom<br />Pinterest → http://www.pinterest.co.uk/spacedotcom
