The Earth is flat

[JEDI]

<groan>

 

[BoomerD]

Then how do they put bubbles in beer or soda?

 

[TheELF]

Then how do they put bubbles in beer or soda?

It took me a while as well and I had to look it up but that exactly is the joke here, beer that has no foam is flat soda that has no bubbles is flat so Earth without bubbles is also flat.