For what it's worth, I've heard YECs say there was a vapor canopy which
shielded the earth from harmful radiation until it collapsed with the
Flood. Concidentally, the ages of the patriarchs drops exponentially
after the Flood. Plotted on a graph, the ages look something like
X X X X
F X
L
O X
O
D X
X
X X X
Kent Hovind, a YEC (http://www.drwebber.com/dino/), has a chart in his
notebook listing the years each patriarch lived, beginning with Adam and
going through Jacob's son Joseph. According to Kent's chart, Methuselah
(969) and Lamech (777) both died in the Flood. Enoch doesn't count
because he got raptured at 365 years. The other pre-Flood partriarchs
lived from 895 to 930 years.
Adam 930
Seth 912
Enos 905
Cainan 910
Mahalaleel 895
Jared 962
Enoch 365
Methuselah 969
Lamech 777
Noah 950 THE BIG ONE
Shem 600
Arphaxad 438
Salah 433
Eber 464
Peleg 239
Reu 239
Serug 230
Nahor 148
Terah 205
Abraham 175
Issac 180
Jacob 147
Joseph 110
I've heard Hugh Ross say there is a nearby supernova which might have
showered the earth with radiation and somehow related to the reduced
life spans. Hugh was not pushing this as the explanation, just a
possibility.
Bill