Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more . CNN  —  The shapes can seem to appear out of nowhere: an undulating S-like spiral streaking across the European skies or a glowing orb trailing above the North American coast. Such strange light shows have been a known feature of rocket launches for years. But as humanity rapidly increases the number of objects propelled into space — more people are