The Earth Story

Timelapse of the sky and night over ancient castles of Spain.

What is happening to the Earth’s Magnetic field? Is it the next disaster? Over recent weeks, you may have seen articles about the Earth’s Magnetic Field, specifically focused on the “South Atlantic Anomaly” – a zone in the Atlantic Ocean where the magnetic field is notably weaker than it is elsewhere on the Earth. This zone has been growing larger and the intensity overall weakening over the past few years. Is this something we should be concerned about? The best answer to that comes from geophysics and geology, which allow us to know how the magnetic field is generated and how it has behaved in the past.

How do ice cores preserve temperature records? Cores drilled through the icecaps in Greenland and Antarctica are our best records of the climate over the last 800,000 years. The best cores literally have 1 band of ice per year, so the ice in each core can be precisely dated. The chemistry of the ice can then show whether there were glaciers present or not….but how do geochemists do that?

Where in the Earth would you be the heaviest? Standing on the surface of Earth, or in orbit around the Earth, to a first approximation the gravity of the planet is no different whether the planet has a lot of mass right at the center or has mass evenly distributed throughout, or has all its mass right at the surface. However, if you moved down through the planet, the gravity will change. If all Earth’s mass was at the center, you’d find that gravity increased as you approached the center, then dropped right as you reached it. If most of Earth’s mass was near the surface, you’d find gravity gradually decreased as you moved towards the center.

Travel to the snowy Caucasus mountains of the nation of Georgia along with a group of snowboarders in this video. They're truly surrounded by amazing landscapes the whole way down.

Shaking Shutdown

Much of modern life makes noise that subtly shakes the earth below. Trucks moving along roads, hammers in a building going up, even people walking along the street. To a seismograph, these little vibrations are nothing but “noise” – a constant background shaking that is measured today as little wiggles in the electronic sensors in the device. At the beginning of 2020, something unprecedented happened.

Starry dunes Sandy formations of this type develop when there is no single dominant wind direction, a multiplicity of them combining instead to shape the landform. This process is not confined to our planet, as these examples, which could easily be in the Rub al Khali (the Empty Quarter) of the Arabian Peninsula, were actually snapped on the next planet out from the sun, namely Mars. Loz Image credit: NASA

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Down is up and up is down. Or is it the other way around? Earth and a fortiori the whole solar system, even our home galaxy- endlessly float into space as the universe expands. As the Earth rotates around the Sun and on itself, it gives the impression that the sky is actually moving for an observer on its surface. That’s probably why it took so long for humanity to accept that the Sun was at the center of the solar system and not the Earth!

Gyres and Eddies! I recently stumbled on a really amazing visualisation by NOAA, showing a view of what was described as "doughnuts" in the ocean (original link at the bottom of the post). These donuts are called Gyres and Eddies.

The biggest water cycle As I'm writing this, there are a handful of puffy white clouds in the sky above me. Clouds are part of the water cycle that we experience every day – water evaporates from the oceans, moves around the atmosphere, comes down as precipitation, and makes its way back towards the ocean through rivers, lakes, and groundwater.

Happy #EarthDay2020 🌎🌍🌏 The image shown is called “Earthrise”. Taken by Apollo 8 Astronaut William Anders in 1968, it has been dubbed the “most influential environmental photograph ever taken”, as it was one of the first times that people saw, in true colour, just how beautiful our little planet is. Looking at this image on a screen is humbling enough, but just imagine seeing this with your own eyes. Some lucky people have gotten to experience this, some even multiple times, over the decades. However, regardless of frequency or timing, there is one common realization that is shared among these lucky few: the Earth is precious, life is precious, and we need to mind it. To demonstrate this, here are some quotes from the men and women who have broken through to the darkness of space and observed our planet from above: "[The Moon] was a sobering sight, but it didn't have the impact on me, at least, as the view of the Earth did."— Frank Borman, Astronaut, Apollo 8. "It truly is an oasis and we don't take very good care of it. I think the elevation of that awareness is a real contribution to saving the Earth."— Dave Scott, Astronaut, Apollo 9 & 15. "The view of earth is absolutely spectacular, and the feeling of looking back and seeing your planet as a planet is just an amazing feeling. It's a totally different perspective, and it makes you appreciate, actually, how fragile our existence is." —Sally Ride, Astronaut, STS-7 and STS-41-G missions. “As we got further and further away, it [the Earth] diminished in size. Finally it shrank to the size of a marble, the most beautiful you can imagine. That beautiful, warm, living object looked so fragile, so delicate, that if you touched it with a finger it would crumble and fall apart. Seeing this has to change a man – James B. Irwin, Astronaut, Apollo Program. "It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn't feel like a giant. I felt very, very small."— Neil Armstrong, Astronaut, Apollo 11, Gemini 8. ..and last but certainly not least, "You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, ‘Look at that, you son of a b**ch.” ― Edgar D. Mitchell, Astronaut, Apollo 14. While most of us will never experience Earth from space firsthand, we can listen to those who have and marvel at images like Earthrise. Earthrise reminds us that we are delicate, exceptional creatures living on a delicate and exceptional planet- it is our duty to protect it. Jean Image courtesy of NASA

If you have clear skies tonight, look up and to the West as Venus will be crossing in front of the Pleiades star cluster. https://solarsystem.nasa.gov/resources/2517/whats-up-video-april-2020-skywatching-tips-from-nasa/

Comparing Terran and Martian sunsets The two photos here have been scaled to depict the same angular width, so that the sinking solar orb and the dance of its light in the atmospheres of two worlds could be viewed side by side. The most obvious difference is the colour, an eerie bluish grey on Mars contrasted with the deep multicolour palette of a wordly evening. There are several reasons for this, one being the layered nature of our atmosphere, and the contrasts in dust and aerosol content between the layers. Another may be the nature of the dust: scientists don't understand as yet why the Martian examples have a bluish tint, but speculate that something in the nature of Martian dust and its interaction with light is probably the cause. The Arean orb also appears slightly smaller than ours due to the greater distance of Mars' orbit around the sun. Loz Image credit: Damia Bouic/NASA/CURIOSITY

How far to the Horizon: How to work out if you really can see your house from here!

As a child I was told by my dad that when you look out across a flat plain the furthest you can see is 21 miles due to the curvature of the Earth. I only remembered this recently; a friend of mine having a flat overlooking Manchester and the rising hills of the Peaks beyond. We stood on her balcony debating how far we thought the hills were away, and it occurred to me that it depends very much on how far we could see before the Earth curved away from us.

The picture below shows the view of the English coast from France, so how far exactly can you see given a clear day and no obstructions?

As a geologist I generally avoid maths, especially when the maths in question appears to have stolen several members of the English and Greek alphabets. Despite this I have persevered for you lucky readers and below can now reveal how far away the horizon really is.

Firstly my father was both right and wrong. We can only see so far due to the curvature of the Earth, however this distance isn’t a constant number. This is because it is dependent on how high above the Earth’s surface we are observing the horizon from. For example, you can see far more of the surrounding landscape from the top of a mountain than you can lying on the floor.

Now, I could go on to use pythagoras’ theorem and prove to you all how we get to the two constants I’m about to show you. However, I shall refrain from doing so but if you do enjoy your maths and working things out from basic principles check out the links below because some lovely people of the internet have done all the explaining for me. The rest of you will just have to believe me that these equations make sense.

So to work out the distance to the horizon you need to multiply the square root of your eye height in feet (your actually height in feet won’t make too much difference) by 1.23. This will give you the distance to the horizons in miles. If you want those figures in metric you simply multiply the square root of your eye height in metres by 3.57 to give you the distance to the horizon in kilometres.

Simple right? Well technically you should take into account refraction due to the air being denser closer to the Earth’s surface. So now just use the constants 1.32 or 3.86 respectively and you can work out if from the top of a mountain you would be able to yell ‘I can see my house from here!’.

For example, If you lay flat on the floor the horizon would be less than a mile away, however if you were stood at the top of a 1000m (3,280ft) mountain you would be able to see 112.8km (67.7 miles), pretty cool right?

There are a few other variables such as you can see further when the sun is setting than during the day, but as a rough measure of distance to the horizon these equations are fairly accurate. So the next time you’re wondering just how far it is to that mountain/skyscraper/bar on the horizon thank whatever deity it is you believe in for our Earth being round, because had it been flat that bar would be much further away!

Further Reading:

http://bit.ly/1FK7Pjr

http://bit.ly/1FK7P2N

http://bit.ly/1E8QCuH

Image Credit: Rolf Süssbrich