Why does relativity mean that mass changes with speed?

Everyone knows that relativity plays hell with time, and that it can do a number on space, but what about mass? Why do objects get more or less mass depending on their relative speed? We're going to give you a quick explanation of why running can make you gain weight. No, we don't think it's fair either. » 1/09/13 11:19am 1/09/13 11:19am

Mass Extinctions Rise Among Plant Species

Entire species of plants are dying off in droves, just like mammals. And there's no way to save them all, say scientists. How do you decide which plant species to preserve at all costs, and which ones to consign to oblivion forever? Answering that question may mean the difference between selective extinction for someā€¦ » 10/22/08 8:40am 10/22/08 8:40am