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This is one of the most advanced images of Earth ever created. It was compiled from data collected during four separate orbits of the Suomi NPP satellite, which were digitally merged into one image. NASA/JPLEverything that begins must eventually come to an end. Just like Earth. It will endure for an immense period, but its final chapter will unfold billions of years after the last person alive today has passed.
Before we discuss the future of our world, let's take a look back at its past and examine when life first emerged on this planet. The history of humankind is incredibly brief when compared to Earth's overall timeline.
Earth Is at Least 4 Billion Years Old
Our planet originated from a massive cloud of gas and dust in space, known as a nebula, around 4.6 billion years ago. The first landmasses may have appeared on its surface as early as 4.4 billion years ago.
In the early stages, Earth's atmosphere lacked oxygen, making it uninhabitable for humans if they had been around. It was vastly different from the oxygen-rich atmosphere we have today, where about 21 percent is oxygen—essential for the survival of many life forms, including humans.
So, where did that oxygen come from? Scientists think that oxygen began accumulating in the atmosphere about 2.4 billion years ago, during a shift known as the Great Oxidation Event.
Tiny microorganisms had already been living on Earth's surface for some time. Some of these organisms developed the ability to harness energy from sunlight, much like the plants of today. As they did so, they released oxygen, which gradually built up in the atmosphere, creating conditions for more complex life forms to evolve.
This process took a considerable amount of time. The earliest animals, likely sea sponges, probably emerged around 660 million years ago. Depending on the definition of humans, they appeared in Africa between 200,000 and 2 million years ago, and from there, humans spread across the globe.
Earth Will Be Here for Billions More
When we consider the future of Earth, it's clear that two key elements are crucial for human survival here.
The sun is the primary source of energy that sustains life on Earth. Plants absorb sunlight to grow and produce oxygen. Animals, including humans, depend on plants either directly or indirectly for food and oxygen.
Another factor that makes Earth livable is the constant movement and shifting of its surface. This dynamic surface produces weather patterns and chemical changes in the oceans and on the continents, which have enabled life to thrive and evolve on our planet.
The movement of Earth's outer layer, made up of large sections known as tectonic plates, is powered by heat originating from the planet's interior. This heat source will continue to keep the Earth's interior hot for billions of years to come.
So, what changes can we expect? Scientists predict that the sun will continue to shine for another 5 billion years. However, over time, it will gradually become brighter and hotter, warming the Earth more and more.
This warming will occur so slowly that we wouldn't even notice it. In approximately 1 billion years, Earth will become too hot to sustain oceans on its surface, making it impossible for life as we know it to survive. Considering that the average human lifespan is about 73 years, this equals roughly 13 million human lifetimes.
Long after that — around 5 billion years from now — the sun will expand into a massive star, referred to by astronomers as a 'red giant,' and eventually consume Earth. Just as Earth existed for more than 4 billion years before humans appeared, it will continue to exist for another 4 to 5 billion years, long after it becomes uninhabitable for humans.
Shichun Huang is an associate professor of Earth and planetary sciences at the University of Tennessee.
This article is republished from The Conversation under a Creative Commons license. The original article can be found here.
