Why does front page of Google.com give no feedback when trying to search when nothing’s entered?

Carry out the following experiment:

  1. Go to google.com,
  2. Leave the "search" field empty,
  3. Click "Google search"

I was having a discussion with my friend about how applications should always do something when user clicks a non-disabled button. In this case, there's absolutely zero feedback, not even a bubble saying "please enter something". Is there a clear reason, or is the UX of the front page flawed here, according to the best practices?