MILLIONS+ BC WRITERS ARE SEPARATED BY METHOD OF OBSERVATION / DEDUCTION. MANY TYPES OF SCIENCE COMBINE, WITH EACH BEING LAYERED BY “THE OLDEST IS ON THE BOTTOM” TECHNIQUE.
Superposition, or the layer theory, assumes that the old stuff is on the bottom.
- Law of superposition in geology and archaeology, which states that sedimentary layers are deposited in a time sequence, with the oldest on the bottom and the youngest on the top
- Superposition calculus, used in logic for equational first-order reasoning
- Superposition principle in physics and engineering, asserting the linearity of many physical systems, including:
- In chemistry, a property of two structures that have the same chirality
Radio-isotopic dating follows rocks process of decaying. This releases energy (in the form of radiation) and often changes one element into another.
- The utility of the rubidium–strontium isotope system results from the fact that 87Rb (one of two naturally occurring isotopes of rubidium) decays to 87Sr with a half-life of 49.23 billion years. In addition, Rb is a highly incompatible element that, during partial melting of the Earth's crust, joins the lava melt (rather than remaining in crust minerals). As a result, Rb is enriched in crustal rocks.
- The radiogenic daughter, 87Sr, is produced in this decay process and was produced in rounds of stellar nucleosynthesis predating the creation of the Solar System.
Tephrochronology is uses volcanic ash from a single eruption—to create a time bookmark for that eruption.
The premise of the technique is that each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the bookmark (aka. "tephra horizon") will act as time marker.
Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. Paleomagnetism (or palaeomagnetism in the United Kingdom) is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials.