The messiness of science

Brooke Kuei
Sep 7, 2018 · 6 min read

I can’t decide — is science more exciting when it confirms a well-known theory, or when it goes against everything you know?

As a graduate student, I must admit that I prefer the former (read: have an all-consuming panic attack every time I think a new experiment is about to disprove everything I’ve worked on), but sometimes evidence for the opposing side is equally — if not more — valuable to pushing progress.

In this post, I wanted to talk about two stories in science news that I came across last week — one about the long-sought decay of the Higgs boson that further bolsters a famous physics model that describes our universe, and one about a fossil study that boldly opposes everything we know about the extinction of dinosaurs. I am sharing these stories because I’ve been in a science rut lately — bored of my project, tired of repetitive experiments, frustrated by confusing results — but these stories remind me that scientific progress is nearly never linear, and perhaps that’s the beauty of it.

Decay of the Higgs boson — where you at bb?

Everything is made up of atoms, atoms are made from electrons and protons and neutrons, and protons and neutrons are made from even tinier particles called quarks and gluons. Electrons, quarks, and gluons are examples of what physicists call elementary particles — essentially, the smallest building blocks of matter. Other elementary particles include photons, W bosons, and Z bosons, and their classification and behavior are described by the Standard Model. The most important part of the model, though, is the Higgs boson.

The Higgs boson is the reason you have mass. Basically, Higgs bosons create a field that other elementary particles interact with, such that particles that interact with it a lot (like quarks) have more mass while particles that do not interact with it (like photons) have no mass. Higgs bosons are like weights at the gym: if you’re lifting weights all the time you’ll look buff and muscular, but if you’re lazy like me and find a new way to avoid the gym every day, you will be forever tiny.

Higgs bosons can be created by high energy collisions between protons, which is exactly the type of experiments that are conducted at the Large Hadron Collider (LHC) in Geneva. However, due to its 10^-22 second lifetime, the Higgs boson itself cannot actually be observed. Instead, the Higgs boson can be detected by elementary particles that it decays into, such as pairs of bottom quarks, W bosons, Z bosons, tau leptons, photons, and some more complicated configurations. In fact, the famous 2012 discovery of the Higgs boson relied on the detection of W bosons, Z bosons, and photons. (Side note: when yours truly was but a wee high school student applying for college, I distinctly remember declaring in my personal essay that I would discover the Higgs boson! Too bad some Nobel-prize winning physicists beat me to it before I even started my sophomore year…)

Although the 2012 discovery was monumental, there was still a missing piece in the puzzle. Despite the fact that the Higgs boson decays into a pair of bottom quarks (bb) the majority of the time, these decay particles were the most elusive to detect. So why is the most common decay product also the hardest to see? The problem is that so many other interactions produce bottom quarks that the signal from a pair of bottom quarks that originated from a Higgs boson simply gets drowned in background noise. Last week at the 2018 International Conference on High Energy Physics, the experimental collaborations ATLAS and CMS reported the observation of the decay of the Higgs boson into pairs of bottom quarks at a rate consistent with the Standard Model. So how did they do it?

The decay of the Higgs boson into a pair of bottom quarks is difficult to detect because many other interactions also produce bottom quarks.

The trick is that instead of looking for the Higgs boson decay directly, researchers looked for a different type of event known as “associated production.” This is a collision in which a Higgs boson is produced at the same time as a W or Z boson, both of which decay in easily identifiable ways. By using the signatures of associated production to both identify events in which a Higgs boson is generated and reduce the background noise, the Higgs boson was finally observed decaying into a pair of bottom quarks.

So there you have it. The Higgs boson was initially predicted by Peter Higgs in 1964, yet it wasn’t until 48 years later that it was discovered, and another 6 years after that for it to be better understood. That sure puts my fourth year of graduate school into perspective!

The dinosaur extinction — who done it?

66 million years ago, a massive asteroid impacted Chicxulub, Mexico, clouding the planet with debris, triggering tsunamis and earthquakes, and causing global ecological disruptions that wiped out three-quarters of life on Earth, including dinosaurs — right?

Wrong.

Well, maybe. But the fact that the Alvarez hypothesis, the cause of dinosaur extinction that I was taught in school, watched in movies, and learned in museums is even up for debate was a surprise to me.

The basis of the asteroid impact theory is the discovery that a layer of rock found all over the world that is dated to the same time as the mass extinction event is rich in the metal iridium. While iridium is rare on Earth, it is found in meteorites at the same concentration as was found in this layer, leading scientists to postulate that iridium was scattered across the planet following the impact and vaporization of a large asteroid. When the Chicxulub crater was found under Mexico’s Yucatan Peninsula and dated to around the same time as the dinosaur extinction, the asteroid impact theory became a widely accepted explanation for the end of the Cretaceous period. Case closed.

Except…iridium is also found in the Earth’s core and the Earth’s core is the source for magma. An alternative hypothesis for the mass extinction of dinosaurs is the gradual, compounding effect of a series of colossal volcanic eruptions in a part of western India known as the Deccan Traps. These eruptions would have spread iridium around the world while simultaneously spreading dust, soot, and greenhouse gases, slowly leading to mass extinction.

Although most people still associate the mass extinction of dinosaurs at the end of the Cretaceous period to an asteroid impact, new science suggests that volcanic eruptions may be another explanation.

Gerta Keller, professor of geosciences at Princeton University, recently took a trip to India to collect new data for a paper showing that the biggest Deccan eruptions occurred during the 60,000 years before the mass extinction, suggesting that the Deccan Traps, and not the Alvarez asteroid, caused the death of our beloved dinosaurs.

Keller’s theory is not a new one, though. 30 years ago, Keller presented her findings from a study of fossils of single-celled marine organisms called foraminifera, or “foram” for short. Because foram fossils are abundant and well preserved, they are a useful marker for studying extinction patterns. Interestingly, Keller found that all around the world, foram populations had started to decline 300,000 years before Alvarez’s asteroid impact. Even more interestingly, the foram near Chicxulub did not seem to experience any sudden drop in population during the time of the asteroid impact.

Although Keller was laughed off stage when she presented her first foram study supporting the gradual extinction of dinosaurs as a result of volcanic eruptions of the Deccan Traps, she has gone on to lead a successful career and published over 100 articles supporting her theory.

I definitely don’t know enough about paleontology, geology, or physics to posit which theory I support, but the decades long dispute just goes to show how disordered scientific progress can be. Even if the Deccan Traps hypothesis has a minority support, the perseverance of scientists like Gerta Keller to disprove a theory that many have already taken as the truth is, in my opinion, healthy for the scientific community as a whole.

The observation of the Higgs boson decay into bottom quarks supported the well-established Standard Model of particle physics while the Deccan Traps eruption timeline goes against the widely accepted asteroid impact theory — both scientific findings are equally monumental,

and for me, as I write this after a long day of experiments, they are a reminder that discovery doesn’t follow a straight path. It will take time, debate, and creativity, but the end result — *fingers crossed* — will be worth your while.

*This is my first science blog post! Please follow if you want to see more :)

phd student and amateur science writer

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