Answer:
Radioactive isotopes are unstable and will decay. ... The isotopes will decay into a stable isotope over time. Scientists can tell how old the rock was from looking at the radioactive isotope's half-life, which tells them how long it would take for there to be half the radioactive isotope and half the stable isotope.
The Mayan and other Mesoamerican cultures used a vigesimal number system based on base 20 (and, to some extent, base 5), probably originally developed from counting on fingers and toes. The numerals consisted of only three symbols: zero, represented as a shell shape; one, a dot; and five, a bar.
Prayer, charity, fasting, pilgrimage
1.) Coastal environments, deserts, mountain environments, savanna grasslands, and forests.
2.) Each ecosystem has a different climate and people and animals who have adapted to these climates differently than the other environments. Each environment has its own resources there that the other might not have for them to survive.
~Anything you say huh, well I say sleep well tonight!
