What is reality and what is illusion?

Wikipedia defines reality as Reality is the state of things as they actually exist, rather than as they may appear or may be thought to be.But can reality be so easily defined?? Who defines and who knows what actually exists and what not..When I am writing this blog or you are reading it you are feeling like you are sitting or standing but actually we are zooming through space at amind boggling speed of 67,000 miles per hour. We feel that our body is solid but it is mostly empty spaces...Scientists first thought that the smallest particle that consisted reality was atom but this theory later seemed to be an illusion and the electrons, protons and neutrons were seemed as elementary. Now days this too seems illusion and it is said that there are 16 elementary particles..

But can this even be said as true reality??? Let me make myself clear...every science student knows about young's double slit experiment...In that appearance of multiple patterns of light on the screen is explained by the wave nature of light..but even when only single photons are fired through the slits multiple stripes still appears on screen...How can a single photon pass through single slit and both the slits at the same time is beyond the explanation of physics at present..It can only be explained by the theory of parallel universe and considering the world is a great holographic image of the things occurring at the boundary of our universe..So hindu philosophy has correctly termed the whole universe as maya...If there is only one truth in the universe it is our atman...perhaps....Or who knows perhaps this is also illusion..!!!