How old is planet

They've attempted to predict the age based on changing sea levels, the time it took for Earth or the sun to cool to present temperatures and the salinity of the ocean.

As the dating technology progressed, these methods proved unreliable; for instance, the rise and fall of the ocean was shown to be an ever-changing process rather than a gradually declining one. And in another effort to calculate the age of the planet, scientists turned to the rocks that cover its surface.

However, because plate tectonics constantly changes and revamps the crust, the first rocks have long since been recycled, melted down and reformed into new outcrops. Scientists also must battle an issue called the Great Unconformity, which is where sedimentary layers of rock appear to be missing at the Grand Canyon, for example, there's 1.

There are multiple explanations for this uncomformity; in early , one study suggested that a global ice age caused glaciers to grind into the rock , causing it to disintegrate.

Plate tectonics then threw the crushed rock back into the interior of the Earth, removing the old evidence and turning it into new rock. In the early 20th century, scientists refined the process of radiometric dating.

Earlier research had shown that isotopes of some radioactive elements decay into other elements at a predictable rate. By examining the existing elements, scientists can calculate the initial quantity of a radioactive element, and thus how long it took for the elements to decay, allowing them to determine the age of the rock. But rocks older than 3. Greenland boasts the Isua supracrustal rocks 3. Samples in Western Australia run 3.

Research groups in Australia found the oldest mineral grains on Earth. These tiny zirconium silicate crystals have ages that reach 4. Their source rocks have not yet been found.

Meanwhile, scientists have also found 7-billion-year-old stardust on Earth. The rocks and zircons set a lower limit on the age of Earth of 4. When life arose is still under debate, especially because some early fossils can appear as natural rock forms. Hawaii's Mauna Kea volcano is taller from base to summit than Mount Everest, but most of it is underwater.

Earth's longest mountain range is also underwater, at the bottom of the Arctic and Atlantic oceans. It is four times longer than the Andes, Rockies and Himalayas combined. Near the surface, Earth has an atmosphere that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases such as argon, carbon dioxide, and neon.

The atmosphere affects Earth's long-term climate and short-term local weather and shields us from much of the harmful radiation coming from the Sun. It also protects us from meteoroids, most of which burn up in the atmosphere, seen as meteors in the night sky, before they can strike the surface as meteorites. Our planet's rapid rotation and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape in space.

The solar wind is a stream of charged particles continuously ejected from the Sun. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles.

These air molecules then begin to glow and cause aurorae, or the northern and southern lights. The magnetic field is what causes compass needles to point to the North Pole regardless of which way you turn. But the magnetic polarity of Earth can change, flipping the direction of the magnetic field. The geologic record tells scientists that a magnetic reversal takes place about every , years on average, but the timing is very irregular. As far as we know, such a magnetic reversal doesn't cause any harm to life on Earth, and a reversal is very unlikely to happen for at least another thousand years.

But when it does happen, compass needles are likely to point in many different directions for a few centuries while the switch is being made.

And after the switch is completed, they will all point south instead of north. Namesake Namesake The name Earth is at least 1, years old. Size and Distance Size and Distance With a radius of 3, miles 6, kilometers , Earth is the biggest of the terrestrial planets and the fifth largest planet overall.

It takes about eight minutes for light from the Sun to reach our planet. A 3D model of Earth, our home planet. Kid-Friendly Earth Our home planet Earth is a rocky, terrestrial planet. NASA has selected a new Earth science mission that will study the behavior of tropical storms and thunderstorms.

Working together, two instruments could open the door for a more efficient, cost-effective way to gather key information for weather forecasting.

This page showcases our resources for those interested in learning more about ocean worlds. Ocean Worlds Resources.

Use Chemistry. The Antarctic ozone hole reached its maximum area on Oct. NASA is looking into whether mixed reality technology could help with repairs and upgrades on the Cold Atom Lab aboard the space station.

A vivid aurora is seen over Earth from the International Space Station. Behold an Aurora Over the Southern Skies. Full Moon Guide: October - November Satellites are producing a deluge of data, so engineers and scientists are setting up systems in the cloud to manage it. A new paper details how the hydrological cycle of the now-dry lake at Jezero Crater is more complicated than originally thought. We need to go back to the time of Galileo, except that we're not going to look at his work, but rather at the work of one of his contemporaries, Johannes Kepler Kepler briefly worked with the great Danish observational astronomer, Tycho Brahe.

Tycho was a great and extremely accurate observer, but he did't have the mathematical capacity to analyze all of the data he collected. After Tycho's death in , Kepler was able to obtain Tycho's observations. Tycho's observations of planetary motion were the most accurate of the time before the invention of the telescope! Using these observations, Kepler discovered that the planets do not move in circles, as years of "Natural Philosophy" had taught. He discovered that they move in ellipses.

A ellipse is a sort of squashed circle with a short diameter the "minor axis" and a longer diameter the "major axis". He found that the Sun was positioned at one "focus" of the ellipse there are two "foci", both located on the major axis. He also found that when the planets were nearer the sun in their orbits, they move faster than when they were farther from the sun. Many years later, he discovered that the farther a planet was from the sun, on the average, the longer it took for that planet to make one complete revolution.

Here you see a planet in a very elliptical orbit. Note how it speeds up when it's near the Sun. Kepler's third law is the one that interests us the most. It states precisely that the period of time a planet takes to go around the sun squared is proportional to the average distance from the sun cubed.

Here's the formula:. Note that as the distance of the planet from the sun is increased, the period, or time to make one orbit, will get longer. Kepler didn't know the reason for these laws, though he knew it had something to do with the Sun and its influence on the planets. That had to wait 50 years for Isaac Newton to discover the universal law of gravitation.

Closer planets revolve faster, more distant planets revolve slower.