What’s the most interesting science fact you know? x

Question: What's the most interesting science fact you know? x
- Keywords:
  fact
Asked by mrkrabs to Martin, Rob on 14 Mar 2012. This question was also asked by bolzanoweierstrass.
- Martin Zaltz Austwick answered on 14 Mar 2012:
  
  It’s not quite a science fact, but there’s a theory about the “Dunbar number” – which is how many people you can know before it gets too confusing. Not just people you meet or knew in the past, people that you actually know or are friends with. It’s supposed to be somewhere between 100 and 300 (depending on who you ask), but some people think Facebook and other sites on the internet might be making it bigger than it was in the past, because it’s easier to keep up with people. But in some way the Dunbar number would be how many people you can know!
  
  I met someone last summer who was trying to figure out the same thing for bats, and for mice. Turns out animals might have the same thing – more than a certain number of friends and their brains start getting confused!
- Robert Thompson answered on 23 Mar 2012:
  
  Hey MrKrabs and bolzanoweierstrass, i like this one ….
  
  Sound travels much faster through a steel than it does air: Sound travels at about 6000 m/s through steel, 1490m/s through water and 330 m/s through air.
  
  So If you put your ear to a steel rod and some one talks at the other end,you would hear before someone not using the rod

Question: What's the most interesting science fact you know? x