How would you figure out what the universe is made of? 

You might want to use the so-called Large Hadron Collider- a circular machine 17 miles around located near Geneva, Switzerland. It smashes protons together– and in the mess of particles flying out, there might be undiscovered particles that tell us something new about the universe. We can’t let them get away! That’s why international teams of physicists build machines called “detectors” around the collision point. A detector is like a camera, recording traces of particles so we can study them.

The collider is about to get a powerful upgrade, and the detectors we have now will be completely overwhelmed. So we need to build new detectors.

One team, named ATLAS, is building a detector made of thousands of square silicon sensors like these. Each square is divided into over 5000 tiny strips, and each strip can detect passing particles. Without this detector, we cannot effectively study particles at the new collider! 

This detector is currently breaking. Catastrophically.

The problem has to do with temperature. We need to run this detector cold, around -30 F. When materials get cold, they contract, and some contract more than others. The sensor is built like a sandwich of materials, with electronics, mostly made of copper, glued down to silicon. Here’s the catch: copper contracts more than silicon when cold.

The force of the copper contracting pulls on the silicon through the stiff glue between them, and the silicon bends and bends, until it cracks. This is REALLY bad! When the silicon cracks, the entire sensor is unusable, and we miss any particles passing through!

So I am working with a global task force to redesign this detector! We tried remaking the electronics with less copper– but the silicon still cracked. We tried spacing them out more to disperse the stress– still cracked. Then we added more support underneath the silicon, and… cracked! 

Now we are left with one potential solution. The idea is to place a new layer of soft glue between the copper and the stiff glue, like adding mayo to this sandwich. So now when the copper contracts, the force should be absorbed by the squishy glue underneath and won’t bend the silicon.

We’ve started building detector pieces with the new soft glue. And we’ve tested them colder than ever, -95 degrees, colder than the south pole in winter. And we found… not a single crack!

We have thousands of pieces left to build, BUT this is a successful proof of concept! At long last we have a promising solution to the cracking problem, so this detector will be ready to track down new particles and answer the big questions about our universe.

Let me take you back to your childhood. It is summer, the vacation just started, your best friend came over. You’re sitting on the carpet in the living room, and have a big box of LEGO bricks all over the place. Just a few simple bricks and your imagination - enough to construct whole worlds.

Little did your younger self know this is actually how the world works. And I am not talking about molecules or atoms, but about something much smaller, much more fundamental - elementary particles. Up until now, humanity has found 17 of these elementary building bricks, and they make up everything we see on this planet.

The catch? When we look above the boundaries of earth, at the rotational speed of galaxies or the expansion of the universe we see that these bricks only describe 5% of the energy content of the universe. Imagine having access to only 5% of the box - your imagination would be severely limited and so is our current understanding of the universe.

So how do we find the other 95% Dennis? I am glad your curious inner child asks!

At the beginning of the 20th century, a smart man told us E = mc2. So if we put enough energy at one point in space, we can actually create new mass, and amongst it maybe new particles.

That is why we built powerful particle colliders that smash protons with almost the speed of light. Then, we capture the newly created particles with giant cameras: 50 meters long, 25 meters in diameter, and - fasten your seatbelts - making 40 million pictures each second.

More than 10000 people around the world run these experiments. Around 50 here at Berkeley lab. My group and I specialized in Artificial Intelligence to analyze the massive amount of complex pictures.

Our newest Approach uses two AIs, Alice and Bob. First, we teach Alice which pictures can be created from the 17 particles. Just like ChatGPT knows what a box of LEGO looks like when I asked it to draw one for this talk. Then, we let Bob autonomously compare Alice's predictions with the experimental observations. As the only difference that he can find are things missing in our model, Bob is directly looking for the remaining 95%.

In the past, we have shown that Alice and Bob do a great job together and they already started to explore places that nobody looked before. However, as all AI methods, Alice and Bob are very data-hungry, and we need more pictures to potentially find something.

At this very moment, the collider is running and our detector is taking more and more data. Once the data taking is finished we will invite all our friends, sit down on the carpet in the living room, dump the box of LEGO onto the ground, and start looking for particles beyond our imagination.

From there, I start my detective work. I identify which points are galaxies closest to us, and further away. From the blues to the reds here.

I use the distance of galaxies to turn a two dimensional photograph into a three dimensional map.You know that nothing can travel faster than light.As such, each slice of depth in the 3D map is a snapshot of cosmic history.

A series of pictures in chronological order is… a movie. In this case, the oldest movie in existence.

Now, when the universe was tender and young, it was very smooth.As it grew older, gravity made it clumpier.Each clump follows an underlying primordial pattern made of dark matter. Think of it as the skeleton of the universe. Galaxies live on those clumps. And therefore galaxies highlight the skeleton of the universe.

I use the things that we can see, to learn about the things that we cannot see.

By looking at where the light from galaxies is coming from, I can guess the size and shape of that primordial pattern.Just like by looking at the appearance of any vertebrate, I can get a sense of their skeleton’s size and shape.

My detective self only needs to go back to the oldest movie, measure the size of that primordial pattern at different moments in time, and I have a detailed growth history of the universe… the same way your pediatrician has your growth chart.

Finally, I can compare proposed models of dark energy, to actual data collected.

Once again, I use the things that we can see in the oldest movie to learn about the things we cannot see, in the process, shedding light on the nature of dark energy. 

Ten years from now, this is what the Moon will look like: a permanent human base capable of growing its own food, synthesizing its own fuel, and obtaining its building materials and water directly from the Moon itself. As mind-blowing as this idea sounds, NASA is actively pursuing it through Artemis - an ambitious program whose only objective is to make the Moon our second home.

To make this dream a reality, we must harness the Moon’s local resources. Transporting everything from Earth is not just impractical, but also unbelievably expensive. Luckily for us, despite its barren appearance, the Moon holds a wealth of untapped resources, with diverse terrains - and yes, even water, hidden in shadowy craters. But before we can exploit these resources, we must first locate and quantify them.

Because we’ve never done anything like that in another world before, we need an autonomous rover capable of detecting and measuring these lunar resources - ideally, without having to drill on the surface.

That is why, at Berkeley Lab, I am leading a team of scientists and engineers to develop an instrument that, based on a novel nuclear technique, can peer deep inside the lunar surface and measure its composition with unprecedented resolution. This instrument fires neutrons into the ground, making it temporarily radioactive. By measuring this resulting radiation, we can uncover invaluable information about the Moon’s composition. What makes our nuclear spectrometer unique is that we found a way to pinpoint where each neutron interacts on the surface, allowing us to create a 3D map of the elements beneath the rover. You can think of it as a special kind of flashlight that reveals the hidden makeup of the terrain, wherever it shines.

So, we are going back to the Moon, but this time to stay. And for that, we must learn to live off the land. Therefore, we need new tools and techniques to map lunar resources effectively and with high precision.

Our instrument will help turn this lunar outpost into reality, which will be the stepping stone for us humans to become a truly interplanetary species.

You, your pets, and your favorite TV show, shouldn’t exist. In fact, our whole universe SHOULD NOT EXIST. 

Why is that? Well as far as we know, we should have all annihilated with antimatter. Sounds like science fiction; but antimatter actually exists.

The world around you – including yourself – is made from particles. An antiparticle is something like the mirror image of a particle: it has the same mass but the opposite charge. 

Once upon a time in the early universe, every single particle still had an antiparticle counterpart. Romantic, right? But there is drama!!!

Well, when a particle meets its antiparticle soulmate, they annihilate and release a large burst of energy. 

But wait, doesn’t that mean that once all particles and antiparticles pairs had found their each other, there should have been nothing left but energy. 

This is obviously NOT what happened. Let me tell you, we just stumbled on one of the biggest questions in physics: Why the heck are we still here? 

The answer is …. we don’t know. 

But, in my research I’m trying to figure it. 

There must be some kind of process that created a few more particles than antiparticles. These additional particles did not annihilate - they survived - and make up the universe as we know it today.

Our goal is to proof experimentally that such a process exists. By us, I mean Berkeley Lab as part of an international collaboration called LEGEND. 

We search for a special nuclear decay of an element called Germanium. For the experts, I’m talking about the Germanium-76 isotope. 

If this decay exists, then it would create 2 electrons and ZERO antiparticles. The discovery of such an imbalance would give us a key to solve the mystery of our existence.

We haven’t managed to observe this decay yet, because it is extremely rare. That’s why we are building a huge experiment with 1 ton of Germanium. But even if you let that sit for 5 years, you only expect that 2 nuclei have decayed. Our job is to make sure that we don’t miss these 2 decays!

Now at the end you still don’t know why you exist…but hey, at least we’re into this together and get the chance to figure it out!