Our planet is home to another world that is much smaller, but also much, much more infinite. Yet we don't see it. We are surrounded by bacteria, which pass through our bodies every day without us even being aware of it. It is only when they make us sick or when we have to clean our house that they remind us of their presence. However, these tiny creatures are so numerous that it is impossible to ignore them.
The invisible war against bacteria
After we sweep, it seems we've eliminated them. But they're still there, just like when we recover from a cold. What if we could suddenly see them clearly? Of course, to do that, we would have to gather thousands and thousands of them. But what if they did? If all the bacteria in the world were stacked on top of each other, how high would they get? There is actually an answer to this question.
A dizzying number for a tiny universe
Before you fall out of your chair (we hope you're sitting down), let's start by figuring out how many individual cells exist. Between bacteria and archaea (another type of single-celled microbe), it's possible that the number exceeds the incredible figure of 10^30 individual cells. In a single number, that's 1,000,000,0000,0000,0000,0000,0000,0000. Perhaps you have never seen such a large number to talk about something so small.
Although most of them are about one micrometer long (0.001 mm), this is such a colossal number that, placed end to end, these bacteria would stretch over… 10 billion light years! It is clearly impossible for our human eyes to contemplate them individually or even all together.
Germs that could surround the Milky Way
In reality, this bacterial thread would be difficult to see, as Luis Villazón points out from Science Focus, because a micrometer is about 75 times thinner than a human hair. However, Villazón says that if you wrapped this thread around the Milky Way, it would surround it more than 20,000 times, creating a band about 2 cm wide that, then yes, could catch enough light to be visible to the human eye.
Our inability to visualize extreme quantities
Statistics like this show how hard we have it to visualize very large or very small quantities. Ten billion light years is an unfathomable length, but if we put all the bacteria in a cube (and it didn't collapse under its own weight), it would only measure about 10 km on each side, which seems much more manageable.
The fascinating world of bacteria
It turns out that up to 80% of all the bacteria that live with us (and did so long before we did) are found in biofilms on rocks, in soil, in standing water, and in virtually every other habitat, including our mouths and intestines.
These biofilms are a few hundred bacteria thick and may contain bacteria, archaea, and fungi of different species that come together to form a kind of microscopic city. In other words, along with our world, there is another one much smaller, but nevertheless much, much more infinite. Even if we don't see it.
Bacteria in the home: a daily reminder
From now on, you may be reminded more of these bacteria every time you clean your home. In the red, black or brown stuff that sometimes appears on the showerhead, under the rim of the toilet bowl or in the grate of the kitchen sink, you can see their bacterial “cities” or biofilms. In these places alone, there will be tens of millions of bacteria. So the next time you clean, remember that you are fighting an invisible and fascinating world that is hiding right in front of our eyes.