Sometimes science means looking for the extremes — the biggest, smallest, oldest, and furthest.

2019 was no different.

Here are three of the science-est things we found this year.

First up, in June, scientists published a letter in the journal Nature announcing

they'd found microscopic fossils of what might be the world's oldest fungus.

The fossils were found in shale rocks from Arctic Canada that scientists sliced up and put into an acid bath.

This is a well-established technique that dissolves the rock but can leave fossil material intact.

The end result was a kind of organic paste the scientists could examine under a microscope.

There they were able to identify long, thin, branching cells that looked remarkably like

hair-like structures called hyphae found in modern fungi, as well as spores.

And chemical analysis revealed signs of a substance called chitin, which fungi use to build their cell walls.

It was enough evidence for the scientists to declare these microfossils to be the world's oldest known fungus.

They dated the surrounding rocks to somewhere between eight hundred ninety million and one billion years old.

This would be amazing, because it's roughly twice as old as the previous oldest known fungus,

though genetic analyses of fungi actually predict they should be about a billion years old.

It's nice when the fossil record and laboratory methods agree.

However, not all researchers agree with these claims.

For example, they're not convinced the material in the fossils really was chitin.

But if these are microfossil fungi, they could help us understand how the group came to be.

More broadly, it could also teach us about how life first spread from the ocean to the land.

Where these fossils were found was likely once a shallow estuary.

In modern times, many plants partner with fungi.

Perhaps these early fungi helped plants get a foothold on land too.

Now, from biology to physics.

In March, scientists publishing in the journal Science announced they'd designed a circuit

to detect the weakest radio signal physically possible.

Radio is the name we give a specific range of wavelengths in the electromagnetic spectrum.

The most basic unit of electromagnetic radiation is the photon.

So the weakest possible radio signal would be a single photon.

But detecting a single photon can be harder than you'd think.

You need a device precise enough, for one thing.

And when you're trying to zoom in that much, even minor background events can be a problem.

It's possible for photons to just pop in and out of existence, especially in warm environments,

adding to the difficulty of detecting a specific one and creating “noisy” background signals.

To get around these problems, the team invented something new

a device that could both stabilize and listen to a radio photon, and get rid of that noise.

The design used a qubit, the principle behind quantum computers.

Qubits, which can be electrons or photons or any other kind of quantum object, can store information,

sort of like a traditional computer uses bits.

And a special kind of circuit is used to hold on to that qubit.

The team needed to tinker with the basic quantum circuit design,

which doesn't work super well with radio photons, to work better with their target wavelength.

Their design was also able suck away noisy background photons,

effectively “cooling” things down, and letting them detect precisely the one photon they were trying to tune into.

A weak signal might sound not that useful, but there are times scientists might like to be able to spot a single photon.

Tech like this could one day be used to improve MRIs, or give a boost to radio astronomers studying super-faint sources of radio waves.

Finally, let's talk geology.

In February, also in Science, scientists announced they'd found what might be the biggest “peaks” on Earth: like giant mountains, but... not on the surface.

The Earth is composed of many different layers.

There's the crust, mantle, and core, but those main layers are subdivided into smaller ones.

In this case, the scientists were studying a boundary in the mantle, about 660 kilometers down, called the… 660-km boundary.

They wanted to know how significant that boundary was.

Previous research had suggested the two layers of rock had chemical differences, implying that they weren't smoothly mixing.

We can't dig that far down to check, of course.

The deepest hole we've ever dug is just twelve kilometers.

Instead, they analyzed seismic waves detected after a huge earthquake struck Bolivia back in 1994.

Seismic waves can travel like ripples on a pond through the Earth, and, like ripples,

they will bounce, bend, or refract if they hit an object or if there's a change in density.

The scientists used powerful computers to analyze data collected from that old earthquake.

They revealed the boundary was a craggy mess, smooth in some places, but riddled with huge dips and peaks in others.

Overall, the topography was more extreme than the Rocky Mountains.

These underground peaks between the layers, if they were on the surface,

could potentially rival the Himalayas as the biggest mountains on Earth -- though it was hard to tell for sure.

Besides being a cool way to peer into the center of the Earth, this can also give us a better understanding of how the mantle mixes.

For instance, the chemical differences between layers might be due to

the remains of ancient tectonic plates that were drawn down into the mantle.

2019 saw science tackle some of the biggest, smallest, and most ancient questions out there.

But then again, that's what science does every year.

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