The instrument for measuring atmospheric pressure, the barometer, is calibrated to read zero when there is a complete vacuum; the pressure indicated by the instrument is therefore called absolute pressure. The term pressure gauge is commonly applied to the other instruments used for measuring pressure.
They see what's already there in a different way, and most of the time, they're aware that their altered perceptions are caused by the drug. After taking LSD, the effects -- known as a trip -- usually start within an hour and can last up to 12 hours, with a peak about halfway through the experience.
THE HARMFUL EFFECTS OF LSD. On LSD, which is often taken in tab form, an intense, altered state transforms into disassociation and despair. Often there is no stopping âbad trips,â which can go on for up to twelve hours. âI started drinking at the age of 15. Then I progressed to taking Ecstasy, speed, cocaine and LSD.