<s>[INST] How old are the earth? [/INST] The age of the Earth is, according to current knowledge, 4.54 billion years.</s>\ <s>[INST] For this result, what is considered to be "the start" of the "existence of earth"? that is, what event or condition is used to mark the beginning of this period? [/INST] The earth formed as a result of accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System.</s>