EDITOR’S NOTE: Part 5 of a series.
Over the past several weeks, we have taken quite a journey through Earth’s atmosphere.
We started right here at the surface in the troposphere, where our weather develops.
We climbed through the stratosphere, home to the protective ozone layer, and continued into the mesosphere, where meteors light up the night sky.
Today, we are completing our journey by exploring the final two layers of our atmosphere, the thermosphere and exosphere.
Our next stop begins roughly 53 miles above Earth’s surface, where we enter the thermosphere. This layer extends hundreds of miles above the planet, and something rather interesting happens here. Temperatures begin increasing dramatically, sometimes reaching more than 2,000°F during periods of intense solar activity.
Now, before you start imagining an enormous oven floating above Earth, there is something important to understand.
The air is so incredibly thin that there are very few molecules to transfer heat. While individual particles possess tremendous energy, you would not experience that temperature the same way you would stand outside on a hot summer afternoon.
The thermosphere is also home to one of nature’s most beautiful displays, the aurora borealis, or northern lights.
These spectacular curtains of green, red, and purple light occur when energetic particles from the Sun interact with Earth’s magnetic field and atmospheric gases.
Oxygen and nitrogen become energized and release light, creating displays that can stretch across the nighttime sky.
During particularly strong geomagnetic storms, the northern lights can sometimes be visible as far south as Missouri.
Another fascinating feature of this region is the ionosphere, an electrically charged portion of the upper atmosphere that overlaps several atmospheric layers, including much of the thermosphere.
The ionosphere plays an important role in radio communications because it can bend or reflect certain radio frequencies, allowing signals to travel far beyond the horizon. It is another reminder that what happens high above Earth can have a very real impact on our lives below.
As we continue climbing, we eventually reach the exosphere, the outermost layer of Earth’s atmosphere.
Beginning roughly 300 to 600 miles above the surface, depending on atmospheric conditions and how the boundary is defined, the exosphere gradually extends thousands of miles into space.
Here, the atmosphere becomes so thin that individual particles may travel enormous distances without colliding with one another.
There is no sharp boundary or imaginary line where Earth’s atmosphere suddenly ends and outer space begins.
Instead, our atmosphere slowly fades into the surrounding environment.
The exosphere is primarily composed of extremely sparse hydrogen and helium atoms.
Some satellites orbit within this outer region, while others travel through the thermosphere below.
Even at these tremendous altitudes, traces of Earth’s atmosphere can still influence spacecraft through atmospheric drag.
What I find most remarkable about our journey is how much happens above our heads without us ever realizing it.
From the clouds drifting past our windows to the auroras glowing hundreds of miles overhead, each layer serves a purpose in the remarkable system surrounding our planet.
Think about it for a moment. We live our entire lives at the bottom of an ocean of air. We complain when it rains, celebrate when the sunshine returns, watch thunderstorms roll across the horizon, and occasionally look up to admire a beautiful sunset. Yet the atmosphere responsible for so much of what we experience extends far beyond anything our eyes can see.
As a meteorologist, I have spent years studying what happens in the lowest portion of our atmosphere. But the more I learn about the layers above us, the more I appreciate how interconnected our planet really is.
The atmosphere is not simply where weather happens. It is part of what makes Earth a place where life can exist.
And that brings our five-part journey through Earth’s atmosphere to a close.
We have traveled from the ground beneath our feet to the outer reaches of our planet’s protective envelope.
Along the way, we discovered that temperatures rise and fall, air becomes thinner, meteors burn, auroras dance, and the atmosphere gradually gives way to space.
My hope is that the next time you look out your window, you see a little more than clouds, sunshine, or an approaching storm.
I hope you remember that above you is an extraordinary system that is constantly changing, protecting us, and reminding us just how remarkable our planet truly is.
Thank you for joining me on this journey through the atmosphere.
There is always something new to discover in the world of weather, and sometimes the greatest discoveries begin with something as simple as looking out the window.
Until our next adventure, keep looking up, stay curious, and remember that there is an entire world of science waiting to be discovered just beyond your window.
