half_lives = {
    "U-238": {"half-life": 4.468, "unit": "billion years"}, # 1e9 years
    "U-235": {"half-life": 703.8, "unit": "million years"}, # 1e6 years
    "Th-232": {"half-life": 14.05, "unit": "billion years"}, # 1e9 years
    "Ra-226": {"half-life": 1600, "unit": "years"},
    "Po-210": {"half-life": 138.376, "unit": "days"},
    "Pb-210": {"half-life": 22.3, "unit": "years"},
    "Rn-222": {"half-life": 3.8215, "unit": "days"},
    "Fr-223": {"half-life": 21.8, "unit": "minutes"},
    "At-217": {"half-life": 32.3, "unit": "miliseconds"},
    "Bi-214": {"half-life": 19.9, "unit": "minutes"},
    "Tc-99": {"half-life": 211100, "unit": "years"},
    "I-129": {"half-life": 15.7, "unit": "million years"}, # 1e6 years
    "Kr-85": {"half-life": 10.756, "unit": "years"},
    "Sr-90": {"half-life": 28.79, "unit": "years"},
    "Y-90": {"half-life": 64.6, "unit": "hours"},
    "Co-60": {"half-life": 5.27, "unit": "years"},
    "Cs-137": {"half-life": 30.05, "unit": "years"},
    "H-3": {"half-life": 12.32, "unit": "years"},
    "C-14": {"half-life": 5700, "unit": "years"},
    "P-32": {"half-life": 14.268, "unit": "days"}
}