Let's assume you gave one of your skin cells to a forensic scientists and asked them to extract and uncoil its DNA. How long would this string of DNA be? Estimates vary between 2 and 3m. Let's go conservatively with 2m for what follows:
Most of our body cells contain a full copy of our DNA. How many cells are in a human body? Nobody has counted them yet, but estimates are in the 37 trillion range. That's 37,000 billion cells - a 37 with twelve zeros. In full: 37,000,000,000,000.
37 trillion cells each having 2m of DNA, that's 37 trillion x 2 metres = 74 trillion metres of DNA in just one human body.
How much are 74 trillion metres? Divide by 1,000 and we are dealing with a more comfortable scale of kilometres: 74 billion km. That's still a lot. Let's put this into perspective.
From Perth to Brisbane, we travel some 4,000 km.
Around the globe: 40,000km.
The distance between the Earth and its moon is 384,000km.
To the sun? 150 million kilometres.
We have to go further to the edge of our solar system.
The distance between Earth to the dwarf planet Pluto is 7.5 billion kilometres, a mere 10% of the combined DNA of one human being. It took NASA's New Horizons Spacecraft 9 years, 5 months and 25 days to get there. But we are making progress in finding a suitable scale to visualise the length of our DNA chain.
So, the equivalent distance of the length of DNA of just one person is 5 return trips from Earth to Pluto.
The Voyager 1 spacecraft, launched in 1977, is now the furthest space probe from Earth at a distance of 21 billion km. It has travelled just over ¼ of the length of our DNA chain. You can track its progress here at NASA's Jet Propulsion Laboratory website at Caltech.
What about humankind?
Well, let's say we have (rounded) eight billion people on this planet.
We multiply the world's population by the length of one person's DNA:
8 billion people x 74 billion km = 592 billion billion km.
How much are 592 billion billion km? We are now truly entering astronomical scales well beyond our solar system. Let's express this distance therefore in light years. One light-second is the time it takes light to travel about 300,000km in the vacuum of space. And because one year is 60 sec x 60 x 24 x 365 = 31,530,000 seconds, therefore 1 light-year is equivalent to 9,461,800,000,000 km. (9.5 trillion km)
We divide our combined human DNA length of 592 billion billion km through 9,460,800,000,000 km and the result is 62,573,990 light-years.
Let's round this to 63 million light-years so that we can work with this number more easily.
The diameter of our galaxy, the Milky Way, is 100,000 light-years. 63 million light-years of human DNA divided by 100,000 light years is 630 trips across the Milky Way, or 315 return trips.
This is only the code that runs in the human species. We haven't even looked at the DNA of plant and animal life. We are talking about several orders of magnitude.
Let's take this to the cosmic extreme: The diameter of the universe is estimated to be 46.5 billion light-years, which is 740 times the length of the combined human DNA chain. If we included the DNA of all plant and animal life on Earth we should be able to cross the universe with this DNA chain or at least get close to crossing it.
Our cells are processing the information from their respective DNA molecule on an ongoing basis in a massively-parallel effort. They make proteins, regulate cellular activities and communicate with other cells. This makes each cell a computer with a built-in sophisticated 3D protein printer (I am simplifying) that can manipulate matter at the individual electron and proton level. While we usually only consider the brain (nerve cells) when talking about the human-computer analogon, we forget the underlying computing tasks carried out by the rest of our body cells.
So yes, we are supercomputers.