You need to have 'Science' as one of your search categories. Why is it left out?
You definitely have 'Science' news items on your home page, so it makes no sense that a user can't search by it.
pedro vera commented
You can get to 'science' by first selecting 'politics' from the tabs and then selecting 'science' from those tabs. I think science should be added to the list of categories shown when 'more...' is selected.