Lisa Randall "Knocking on Heaven's Door"

What you see depends on how you look. Showing a picture of the Eiffel Tower, theoretical physicist and author Lisa Randall begins by demonstrating the deceptively simple idea of scale.

Example: because humans have until recently only used the visible spectrum to observe the universe, knowing that it’s 1027m in size omits crucial information. Finiteness or infiniteness cannot be determined - that’s just how long the earliest photons has been traveling before emptying into our eyes.

Today, she’s going to talk about what we can’t see.   

“As you probe at smaller and smaller scales you don’t find new objects, but new laws.”

I’m struck by the argument she’s making for theorizing, conceptualizing, and its importance to discovery. It’s the same force used by artists, for example, but their conclusions are deeply meaningful rather than deeply independent.  

She transitions to the Large Hadron Collider, which is now using great energies to produce data that can be collected and matched - potentially - to theory. The best matches add to the knowledge of matter at the smallest scales.

A couple LHC facts: it can reproduce a “tenth of a trillionth of a vacuum” and produce a cold “only 1.9 degrees above absolute zero,” which is colder than space.

What can physicists learn using this massive machine? She suggests a few: how particles acquire mass, why gravity is so weak (think about it, the whole Earth is tugging at you right now, yet you can still jump up and down), suggest (or disprove) the symmetry for space and time, or add new dimensions to space and time.

This is an interesting thought: “Mass is not an intrinsic property of particles, otherwise physics would not make sense.”

The LHC has just this summer produced very good evidence for one of the theorized particles, the Higgs boson. Physicists believe that particles acquire mass by by interacting with the Higgs’ field. An excitation of the field produces the boson.   

As for other dimensions, why even consider that possibility? There are a lot of things we don’t know about until we get to the scales that make the possibility meaningful. Relativity, the science of the very big, is in theory compatible with any number of scales. There are connections that we couldn't have anticipated. Other dimensions might explain why gravity is so weak by suggesting, for example, that these dimensions drain, to use a bad metaphor, gravity from the three dimensions with which we’re familiar. If so, experimental physicists hope of find so-called Kaluza–Klein particles, which would provide evidence of interaction between the colossally massive and fantastically small, and perhaps thereby unify the two into a single physical theory.  

She ends with a quote from Steve Jobs’ well known Stanford graduation speech.

“You can’t connect the dots by looking forward, but only by looking backward. So you have to trust that the dots will somehow connect in your future.”

As a theorist, her role is to suggest where the dots may connect.