{"id":49696,"date":"2023-09-19T08:11:37","date_gmt":"2023-09-19T08:11:37","guid":{"rendered":"http:\/\/5b31543f-5a3d-420d-8aa0-a9e94d1c47f1"},"modified":"2023-09-25T11:33:47","modified_gmt":"2023-09-25T11:33:47","slug":"how-old-is-earth","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-old-is-earth\/","title":{"rendered":"How old is Earth?"},"content":{"rendered":"

A guide to the history of our planet’s formation around the Sun, and just how old current estimates believe Earth to be. <\/p>

By Russell Deeks\n <\/p>

Published: Tuesday, 19 September 2023 at 08:11 AM<\/p>

\n\n

How old is Earth?<\/h1>

How old is Earth? According to most estimates, planet Earth is roughly 4.55 billion years old.<\/p>

While that’s not as old as the Sun itself (for reasons self-explanatory!), our home planet Earth is clearly very old.<\/p>

To understand why Earth is so old, we need to look way back to the formation of the Solar System<\/p>

We’ll also take a look at current theories of planet formation.<\/p>

A primer on planet formation<\/strong><\/h2>
An image of a protoplanetary disc around star HL Tauri. The dark rings could indicate newly-forming planets in orbit, pushing aside dust as they go. Credit: ALMA (ESO\/NAOJ\/NRAO)<\/figcaption><\/figure>

Planets form when gravity causes particles orbiting a star \u2013 in our case, the Sun \u2013 to clump together in ever-larger bodies, a process known as accretion.<\/p>

This is why the disk of material surrounding a newborn star is called an accretion disk<\/a>, or a protoplanetary disk.<\/p>

Put very simply, dust particles collide and fuse to form tiny pebbles.<\/p>

Pebbles collide and fuse to form larger rocks<\/p>

Rocks collide and fuse to form larger bodies called \u2018planetesimals\u2019<\/p>

And so it goes on.<\/p>

In the case of Earth, this process would have begun shortly after the Sun itself started to take shape, around 4.6 billion years ago.<\/p>

We know this through the study of rocks.<\/p>

How rocks reveal Earth’s age<\/strong><\/h2>
\"An
An outcrop of metamorphosed rock from Nuvvuagittuq. Credit: NASA<\/figcaption><\/figure>

The oldest rocks on Earth\u2019s surface can be found in Quebec: forming a rocky outcrop known as the Nuvvuagittuq Greenstone Belt, they are around 4.3 billion years old.<\/p>

But geologists know from analysing lead isotopes found in meteorites that the Solar System itself is 4.6 billion years old.<\/p>

And that Earth\u2019s mantle is formed from much the same material as those meteorites.<\/p>

What was early Earth like?<\/strong><\/h2>
\"A
A molten exoplanet. Credit: Mark Garlick \/ Science Photo Library<\/figcaption><\/figure>

Early Earth was a barren, rocky and extremely hot planet whose only atmosphere consisted of gases pumped out by the many volcanoes on its surface.<\/p>

It was regularly bombarded by meteors, too.<\/p>

It wouldn\u2019t be too long before a collision with another large body that scientists dubbed Theia knocked a huge chunk out of it, forming the Moon<\/a>.<\/p>

As a result, it’s safe to say early Earth wasn’t a good place for a holiday, then.<\/p>

But within half a billion years or so, Earth began to cool.<\/p>

The volatile, volcanic surface became more stable and able to support oceans of liquid water.<\/p>

And incredibly, as early as four billion years ago, the first, single-celled forms of life began to appear. <\/p>

How all that happened, though, is a question for another day\u2026<\/p> <\/body><\/html>\n

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