Some of the earliest forms of life have been found in Western Australia, as announced in a study ; the researchers found tiny filaments in 3. Other studies suggest that life originated even earlier. Hematite tubes in volcanic rock in Quebec could have included microbes between 3. Researchers looking at rocks in southwestern Greenland also saw cone-like structures that could have surrounded microbial colonies some 3.
In an effort to further refine the age of Earth, scientists began to look outward. The material that formed the solar system was a cloud of dust and gas that surrounded the young sun. Gravitational interactions coalesced this material into the planets and moons at about the same time.
By studying other bodies in the solar system, scientists are able to find out more about the early history of the planet. The nearest body to Earth, the moon, doesn't experience the resurfacing processes that occur across Earth's landscape. As such, rocks from early lunar history still sit on the surface of the moon. Samples returned from the Apollo and Luna missions revealed ages between 4. How the moon formed is a matter of debate; while the dominant theory suggests a Mars-size object crashed into Earth and the fragments eventually coalesced into the moon , other theories suggest that the moon formed before Earth.
Related : How was Earth formed? In addition to the large bodies of the solar system, scientists have studied smaller rocky visitors that have fallen to Earth. For example, Potassium is unstable and decays into Argon As time passes, a rock will have more and more Argon and less and less Potassium The half-life is the time that it takes for half the radioactive sample to change from one element into the other.
Some isotopes have short half-lives of minutes or years, but Potassium has a half-life of 1. Radiometric dating requires that one understand the initial ratio of the two elements in a given sample by some means.
In this case, Argon is a gas that easily bubbles out and escapes when it is produced in molten rock. Once the rock hardens, however, all the Argon is trapped in the sample, giving us an accurate record of how much Potassium has decayed since that time. So, if we find a rock with equal parts Potassium and Argon, we know that half the Potassium has decayed into Argon, and that the rock hardened 1. Most old rocks have been eroded by wind and water or submerged by continental plates. The oldest reliably dated rock formation is in Greenland, where several different isotopes were used to find an age of 3.
Their pristine interiors give an age that dates back to their formation at the beginning of the solar system. Nearly all meteorites have the same radiometric age, 4. What about the ages of stars and galaxies, and the age of the whole universe? One way to measure these ages is with the travel time of light.
Light travels incredibly fast — , kilometers per second, or , miles per second. On Earth, the delay due to light travel time is a tiny fraction of a second. But in space, the distances are so vast that the light takes a substantial amount of time to travel to us: 8. The calculation of the light travel time is simple once you know the speed of light and have a measurement of the distance.
The speed of light is well known from experiments on Earth, and various astronomical observations confirm that the speed of light has not changed over the history of the universe. Instead, astronomers use several interlocking methods to determine the distances, such as geometric calculations and brightness measurements.
For example, some galaxies look much smaller and fainter than other galaxies of the same kind, showing they are much further away. The Andromeda galaxy, a near neighbor to our own Milky Way galaxy, is 2. That is, we are seeing it as it was 2. But that is just our local neighborhood. In recent decades, astronomers have detected galaxies located several billion light years away. If the light has been traveling billions of years to reach us, then the universe must be at least that old.
People have been trying to figure that out since, well, since the beginning of time. Now That's Interesting. According to NASA , the sun is a yellow dwarf star. It's a hot ball of glowing gases and its gravity is responsible for holding the solar system together. How many more years will Earth survive? Scientists suggest that in about 7. How old is the Earth in human years?
How old is the sun? According to NASA , the sun is about 4. Since almost everything in our solar system formed around the same time, meteorites that reach Earth are, in all probability, the same age as our planet. He used samples of the Canyon Diablo meteorite that landed about 50, years ago in what is now the US state of Arizona, and using lead-lead dating came up with an estimated age range of 4.
Since then, other meteorites have also been used to find the age of Earth.
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