An Interview With Dr. Lisa Randall

Professor Lisa Randall is an American theoretical physicist working in particle physics and cosmology. She is the Frank B. Baird, Jr. Professor of Science on the physics faculty of Harvard University. Her research includes elementary particles, fundamental forces and extra dimensions of space. She studies the Standard Model, supersymmetry, possible solutions to the hierarchy problem concerning the relative weakness of gravity, cosmology of extra dimensions, baryogenesis, cosmological inflation, and dark matter. She contributed to the Randall–Sundrum model, first published in 1999 with Raman Sundrum.

Here is my interview with her about topics from her book Dark Matter and the Dinosaurs, which is about the universe and our understanding of the invisible dark matter in it:

Armen: There was a concept presented of underdense regions of the Universe expanding and pushing against overdense ones, creating high-density filament regions(nodes) analogous to the busy border enclaves of separate socioeconomic neighborhoods. Have you noticed a strong theme of entities in the universe(from galactic to cellular, to possibly the Internet) reaching high-density or high throughput at edges or borders?

Dr. Lisa Randall: Interesting as this idea is, the edges are not generally what takes over. After all gravity is attractive so dense regions tend to attract more matter, becoming increasingly dense. So the densest regions in galaxies, for example, are in the center. However, we and others have studied speculative ideas about extra dimensions of space where much of the interesting physics might happen at the boundary regions known as branes.

Armen: When you saw and felt the K-Pg boundary line at Itzurun Beach in Spain, were you imbued with a more palpable sense of the Earth’s lifespan, and on a similar note, is there further prehistorical information to be gained by digging to new depths, or is any new information to be found in the Earth’s crust/core likely minor compared to that from space?

Dr. Lisa Randall: When I saw the k-Pg boundary line, I might say the reaction was the opposite to what you describe. This event happened recently enough to be preserved and is among millions of history to be preserved in the limestone on this beach. So on the one hand it can be considered an enormous time span but from other perspectives, such as the Earth’s lifetime or even that of life it is relatively recent.

For your second question, I would be very surprised if there were not more to be learned from digging to new depths. Fossils and new methods keep unearthing new discoveries. We can of course hope to learn more from space as well, but it is likely to be a while before that truly answers a lot of questions about life on the planet for example.

Armen: It is clear from your narration that part of your researching dark matter’s role and effects involves countering logical fallacies, like the look-elsewhere effect of the illusory best-fit, or the hubris of seeing dark matter as having to have properties like Standard Model matter. How much does taking fallacies into account get prioritized during this process?

Dr. Lisa Randall: This is a rather abstract way of framing what good scientists have to do. Scientific theories should be logically consistent. Scientists are supposed to work under that assumption. However, it doesn’t mean they can always address all inconsistencies right away. That is part of the challenge — and fun — of doing science. An advantage to looking for new ideas is often to recognize biases endemic to our thinking and try to go beyond them to see if we are missing something.

Armen: In your Double-Disk Dark Matter paper and related description in the book, you note that the DDDM model could be detected through its gravitational effects. Does the recent finding/confirmation involving gravitational waves sent out by black holes connect with or provide value to the DDDM model, or is it a checked box that exists until key data like the Gaia satellite information is acquired?

Dr. Lisa Randall: The recent observation of gravitational waves succeeded in observing the merger of two enormous black holes that sent a great deal of energy into gravitational waves. Though Gaia will be studying gravitational influences, they are far more subtle effects on the statistical distribution of the positions and velocities of stars in the Milky Way. It will be a while before gravitational wave detection will be sensitive to such subtle effects.

Armen: I noticed your use of analogies to connect the abstract to day-to-day living, and thought of one in connection to the potential current sixth extinction. The extinctions that were based on abrupt impacts or changes are like health conditions that we go to the pharmacy or doctor to remedy right away, and the current human-precipitated extinction is like a chronic bad habit or affliction that has caused physiological harm with no quick fix. However, because all around us is matter and energy, may we be able to find a quick fix to siphon or expel heat from the Earth, and/or process junk in the oceans and landfills back into elementary form, or does a global long-term methodology look to be the way?

Dr. Lisa Randall: Your analogy probably applies to your solution too. There are a lot of diseases that don’t have a simple fix at the pharmacy or doctor. People want to believe that all diseases will eventually have quick remedies, and a description in simple terms, but for many diseases no such remedies and descriptions exist, despite years of searching. Expelling heat from the Earth is itself an energy-expensive proposition. People can search, but the solutions are unlikely to be so simple.

I appreciate Dr. Randall for taking part.

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