Useful for calculating today's activity for any
radioactive isotope. You may also back decay sources to find out the original activity (or for any date), knowing the current activity. If the isotope that you wish to decay
is not on the drop down list, check the 'not listed' check-box and manually enter the isotope name and
its half-life to perform the calculation. You may enter date or time or a combination
of both. Calendar pickers are included for date entry convenience.