http://van.physics.illinois.edu/qa/listing.php?id=1228 a good explanation van.physics.illinois.edu... http://van.physics.illinois.edu/qa/listing.php?id=1228 http://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228 observer effect https://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228 observer effect Observer Effect 2 van.physics.illinois.edu... https://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228 https://van.physics.illinois.edu/qa/listing.php?id=1228