Dr. Mark Lindsay was 5 years old when he first learned that tree trunks were brown. "Up until that point, I believed leaves and trunks were all green. Just lighter and darker shades," Mark said. Mark ...

Is your green my green? Probably not. What appears as pure green to me is likely to look a bit yellowish or bluish to you. This is because visual systems vary from person to person. Moreover, an ...

Add Popular Science (opens in a new tab) More information Adding us as a Preferred Source in Google by using this link indicates that you would like to see more of our content in Google News results.