Fish swim in an ocean.  You and I also exist in an ocean, though one less dense than water, a cocktail mix of nitrogen and oxygen we call our atmosphere.  It was long suspected, and proven in 2012, that the entire universe exists within an ocean far more fundamental… a Higgs Field.  The Higgs Field is what — by simply being there — determines mass as everything “swims” through it.  Any particle that interacts with this ocean has mass, any particle that does not interact with it has no mass.  The default speed in the universe for anything without mass is light speed.  The default speed in the universe for anything with mass (however slight) is Rest.  The Higgs Field is that determining factor, and the way it slows matter down is what makes our material universe possible.  The atoms in your body could never form (or for that matter, keep that form) at light speed.  Without the Higgs Field creating the slightest resistance the entire universe would be nothing but particles darting around at the speed of light… in other words, light, but no eyes to see it with.