<iframe width="580" height="385" src="https://www.youtube.com/embed/oHAF-tm8lOE?autoplay=1" frameborder="0" allowfullscreen></iframe> <br>Scientists often change their minds or make mistakes, so why is it a good idea to believe what they say? <br><a href="https://www.youtube.com/watch?v=oHAF-tm8lOE">source</a>