You flat Earthers might want to read up on this.
http://en.wikipedia.org/wiki/Negative_proof"The argument from ignorance, also known as argumentum ad ignorantiam ("appeal to ignorance" [1]), argument by lack of imagination, or negative evidence, is a logical fallacy in which it is claimed that a premise is true only because it has not been proven false, or is false only because it has not been proven true.
The argument from personal incredulity, also known as argument from personal belief or argument from personal conviction, refers to an assertion that because one personally finds a premise unlikely or unbelievable, the premise can be assumed to be false, or alternatively that another preferred but unproven premise is true instead."
Interesting how it sums up every flat earther.
And of course this would be the flat earther's chosen method of argument:
http://en.wikipedia.org/wiki/Logical_fallacy