Tom found out that life on the road wasn't as easy as he thought it would be.
- Tom discovered that life on the road wasn't as easy as he thought it would be.
I heard that footprints of an abominable snowman were found in the Himalayan mountains.
- I heard that footprints of an abominable snowman have been discovered in the Himalayas.
... particles were being discovered. ...
... of them discovered and downloaded by teachers in ...