14
But even the geologically inert Moon does not have rocks dating back to the birth of our planet,
since it too required a substantial period of crust formation, due to its own internal heat and a
large early bombardment of meteors whose history is still etched onto the Moon’s surface in the
form of innumerable craters. Indeed, we see such meteor craters covering the surfaces of all
planets and moons in the solar system that have been geologically inert. However, meteorites
themselves actually provide us with some of the most pristine samples of the earliest period of
the solar system. Specifically, meteorites found on Earth appear to have been essentially isolated
while spread out in the solar system, until eventually being captured by the Earth. While iron
meteorites have been found not to have the long-lived radioactive isotopes needed for dating,
they are invaluable for dating the Earth, since they provide us with pristine samples of primordial
lead, whose isotopic ratios yield the original lead isotopic ratios on Earth, which have since then
been modified by the daughter products from Uranium and Thorium decays. By this method we
find the Earth to be 4.6 billion years old [21]. This is confirmed using stony meteorites, which
have been dated using Rubidium decays [24]. In fact, nearly all meteorites are dated to within
1% of their mean age of 4.53 billion years [17], indicating that they truly have been isolated
since the birth of our solar system. During this earliest period the Earth would have been in its
initial stage of formation, a much different Earth than we see today.
Stellar Astronomy
Are there non-radiometric methods, which can be used to determine such vast ages? Yes, and
the natural clocks they depend upon are very reliable. If you can count on the Sun rising in the
morning, then you can put faith in the process by which its energy is produced, the process of
nuclear fusion. Nuclear fusion is a powerful source of energy we can understand by means of
Einstein’s famous equation, E = mc
2
. Energy is equivalent to mass. Nuclear fusion is the
process whereby mass is converted to energy. The primary constituent of the Sun is the lightest
element Hydrogen. When Hydrogen is fused together with other Hydrogens to form heavier
elements such as Helium, matter is converted into energy and given off in the form of new
particles such as photons and neutrinos. This energy conversion has been occurring steadily in
the core of our Sun, where temperatures are sufficiently high enough, for as long as Earth has
been around, thus bathing the Earth with heat. From the rate of energy produced and the supply
of fuel initially inside the reaction core of the Sun, we can determine its lifetime. As mentioned
previously, this is approximately 10 billion years. Stars the size of our Sun or smaller burn their
nuclear fuel at a fairly steady rate during nearly their entire lifetimes. The present brightness and
temperature of our Sun indicate that nearly half of its lifetime supply has been exhausted so far
[17]. Specifically, solar models indicate that it is approximately 35% brighter today than when it
began its nuclear fusion process. But don’t start worrying about its eminent depletion yet, since
it has another 5 billion years worth of fuel left.
Other stars have been dated to be much older than ours, up to 14 billion years old. In fact,
innumerable stars have already exhausted their supply of fuel and met their deaths. A star dies
by running out of the very fuel that sustains an outward pressure to prevent its own self-gravity
from collapsing it. The larger stars die rather violently, in a process called a supernova. These
titanic explosions thrust matter, including some heavy elements, throughout interstellar space
and contribute to new star formation elsewhere. In fact, it is necessary that a few cycles of this
re-seeding of star formation with new matter to have occurred prior to the formation of our solar
system. Otherwise the heavy elements, which are so abundant in the Earth, would not have been
present in sufficient amounts. We can verify this by checking the oldest stars in our galaxy for