Young earth vs. Old earth
The evidence for a young earth [≈7,519 years vs. billions and billions of years] is overwhelming. Belief in an old earth today, means either a lack of awareness of the evidence or an ulterior motive for being stubborn. Here are two pieces of scientific evidence for a young earth, not the most compelling that's available, but certainly interesting:
1. Soft-tissue has been found  in a Tyrannosaurus rex that is supposedly 68 million years old.
2. When Voyager passed by Uranus and Neptune [1986 and 1989], as two doctors of physics accurately predicted, the strength of the magnetic fields of these planets measured to indicate that both these planets are some thousand rather than billions years old.
But for the Orthodox Christians the "clincher evidence" is Paradise: that man and all nature, outside Paradise as well, were in an incorruptible state before Adam fell. Scientists, whether they be evolutionists or creationists, have no way to study an incorruptible state, or the miracle of Creation or any of God's miracles for that matter – the Virgin birth, the Resurrection, weeping icons, etc.
Creation, Genesis and Early Man, 2nd edition
by Fr. Seraphim Rose
p.854 p. 903