what's the point of a hash if it can be easily decrypted?

Programmer Question

i asked this question:
http://stackoverflow.com/questions/3143693/working-with-huge-spreadsheet

and got a great answer and i followed the advice. i used this:
http://splinter.com.au/blog/?p=86

and i hashed about 300,000 different elements in a column in an excel spreadsheet

since you can do:

=SHA1HASH('The quick brown fox jumps over the lazy dog')

And you'd get back:

2fd4e1c67a2d28fced849ee1bb76e7391b93eb12

couldnt you go backwards as well?

im saying if it encrypts the same text the same way every single time, what is the point?

if you do know the hash algorithm, is it possible to go backwards?

Find the answer here