# WHY DO WE KNOW MORE ABOUT SPACE THAN WE DO ABOUT OUR OWN OCEANS?

Pressure.

But in all seriousness, our planet Earth has a diameter of about 12,500 kilometres (12,742km to be exact), which gives it a radius of approximately 6,250 kilometres, we know it’s roughly spherical (if you believe otherwise then that argument can wait for another post) and anybody who studied maths in school can tell you the volume of a sphere is (where r is the radius). This simple maths puts the volume of the earth at a little over 1 quadrillion cubic kilometres (about 259 trillion cubic miles for anybody using the metric system. For reference 1,000,000,000,000 is one quadrillion.

The observable universe has a diameter of 93 billion light years or 8.8 x 1026 meters, so the volume of the observable universe (I won’t bore you with the maths) is 3.57 x 1021 cubic kilometres. That puts Earth at what is basically an infinitesimally small volume of the whole universe. And so why do we know more about a seemingly infinite space beyond our imagination, than we do about our very finite mass of rock and water? Well first of all, you have to actually ask yourself, can we quantify what we know about space versus what we know about what lies underneath our oceans?

The colonisation of the planet Mars, in my opinion, was one of the biggest events that’s started this debate, why are we looking to settle on other planets, when we haven’t fully explored this one? Which at first seems like a stupid question, it’s completely different areas of science. That’s like wondering why the scientists working on string theory haven’t come up with the cure for cancer yet, because it isn’t what they’re trying to do. However, with the field of space travel making huge leaps and bounds in comparison to sub-aquatic research, it does beg a different question. Why is it easier to explore space than to explore our planet?

Well, in short, space is a vast, empty void of nothingness, it’s very easy to navigate because there are unimaginably large open spaces. And also, there’s the simple fact that it’s a lot easier to design vehicles that can cope in conditions of 0 atmospheric pressure than to cope in conditions where the pressure exceeds 1,071 times that of the pressure at sea level. For every 10 metres you go under water, you experience an extra 14.5 psi of hydrostatic pressure (the fancy way of saying the pressure from the water).

Fun fact: at the bottom of the ocean, the pressure is so great that it would rupture your air drums, your lungs would fill with blood before collapsing, but the good news for you in that situation is that death by suffocation would be pretty much instantaneous, so at least you wouldn’t have chance to think about the pain you’re in. But to add to the good news, it’s very unlikely you’ll find yourself there. In 1960, Jacques Picard and Don Walsh did in fact venture to the deepest part of the Mariana Trench (“Challenger Deep” which is just under 11km below sea level and is thought to be the deepest part of the ocean). In perspective, that’s still only about 1/9 of the way to the Earth’s core.

To give you a way to make sense of those numbers, the deepest part of the ocean we’ve explored is about as far below sea level as an aeroplane flies above sea level. It’s theorised that we’ve explored about 5% of the ocean, and that number hasn’t changed much since the turn of the century.

By definition, when we talk about observing what’s in the ocean, the human eye can only observe objects that are reflecting light, and in the ocean, once you reach a depth of 200 metres, the sunlight levels are so low, that photosynthesis cannot occur, and once you get into the midnight zone, a kilometre deep, sunlight is a thing that only exists in your memory. Now compare that to space, where the waves of visible light can travel, without obstruction, for distances far beyond our imaginations, , and then take into account the satellites that can pick up radio waves, infrared, and all other forms of electromagnetic radiation that aren’t visible light, and it’s no wonder we can get a clear picture of the cosmos.

The thing is, what we know about “space” can’t be quantitively analysed, because if we’re counting celestial bodies, like planets, then what we know about Earth, is a part of what we know about space, and if we aren’t, then most of what’s out there is just empty nothingness (unless you’re getting into dark matter, anti-matter, string theory, and all those fields still mostly built on theoretical foundations). Stars are just ball of gas (and we can do fairly simple spectroscopy to figure out what those gases are, galaxies, basically, are just collections of solar systems that span across unimaginable distances, and that may be a slight over simplification, astronomy, astrobiology, cosmology, they’re all interesting, in depth fields. But so is marine biology, ecology, zoology, they are all interesting, highly researched fields, but they just aren’t comparable, and each of them poses their own difficulties.

There are a lot of things that can be recreated in a lab when it comes to physics and chemistry, but we can’t use a lab to discover a new species of fish, biology is a result of evolution, and evolution, by definition, takes hundreds of thousands of years, and it’s far to unstable to accurately predict with computer simulations.

So really, there isn’t an answer to the question of “why do we know more about space than we do about our own planet?” because the question itself is flawed.  The real question I’d urge you to ask yourself is “How do we know what we do about our planet, and the space it’s in?”.

Thank you,

Ryan.