It takes just 3 seconds for a landmine to detonate after it's stepped on. And it's the reason billionaire entrepreneur Richard Branson opened a new immersive installation steps from New York City's Ukrainian village, asking visitors to imagine just 3 seconds to say goodbye. The Russians have put down hundreds of thousands of mines.And if a young Ukrainian, you know, 20-year-old steps on one of those mines, he'll hear it. It takes three seconds before it goes off. So, they've got three seconds before they kn ...