While many human activities produce greenhouse gases, the greenhouse effect is actually a natural process. Many atmospheric gases help trap heat in Earth's atmosphere, including natural gases like carbon dioxide. So while human activities exacerbate the natural greenhouse effect, it is not solely due to them.
Carbon-12 has 6 neutrons and 6 protons, making it 12.
Carbon-14 has 8 neutrons and 6 protons, making it 14.
It is used to date the age of things that are very old using radioactive isotopes.
It is defined as that force necessary to provide a mass of one kilogram with an acceleration of one metre per second per second. One newton is equal to a force of 100,000 dynes in the centimetre-gram-second (CGS) system, or a force of about 0.2248 pound in the foot-pound-second (English, or customary) system.