How to measure things you can’t see Particle physics Dr. Julie Roche I will tell you: -What I study (really small particles you can’t see with your eyes) -And How I study it (by throwing things at them) But I would like to start by playing a little game with you: Take a piece of paper and draw a physicist.

Who’s the physicist? 12 3: both of them are physicists Albert Einstein Physics Nobel Price Marie Curie Physics Nobel Price Chemistry Nobel Price

Who’s the physicist? 12 3: both of them are physicists J. Webster Professor of English Ohio U J. Matthews Professor or Physics MIT

Who’s the physicist? 3: both of them are physicists G. Mavimbela PhD student in Physics Ohio U A nice girl in front of a computer 12

Who’s the physicist? 3: both of them are physicists 1 2 2

To finish our little game: Look back at the physicist you have drawn. Most people will draw an old white man (à la Albert Einstein). But in reality, physicists come in all genders and all races. They also come from all social background: do you know graduate school in Physics is very often FREE? You can become a Physicist if you want to.

What I really want you to tell you today is: You don’t have to choose to become a scientist today but -Act now to keep your career options open (and easy). Take all the math and science class you can. Get involved in science fairs and other extra-curricular science activities. -Nurture your own goals and talents. Read, watch and listen about science, visit web sites, museums, etc… Talk about your future with your parents, teachers, friends.

How to measure things you can’t see Particle physics Dr. Julie Roche I will tell you: -What I study (really small particles you can’t see with your eyes) -And How I study it (by throwing things at them)

What is the world made of? We believe the world is made of 12 fundamental particles. Fundamental means that these particles are not made of anything smaller. What holds the world together? By observing the simplest objects the fundamental particles form, we can learn about the four most fundamental forces of our universe. The trouble is that we can’t see with our eyes these simplest objects because they are so small.

To see, we detect with our eyes the information of the bounced-around light. BY THE WAY, HOW DO WE SEE ? Light is actually a wave of energy. Light carries information about the physical world because it interacts with what it hits. Other animals, like dolphins and bats, emit and detect sound waves. In fact, any kind of reflected wave can be used to get information about the surroundings

Pretend that you are unlucky enough to fall into a cave without a flashlight. However, you are lucky enough to have a bucket of glow-in-the-dark basketballs. Suddenly, you hear a snuffling sound. WHAT’S THAT ???? Basket balls: It’s a big thing… Tennis balls: No much better Marble balls: It’s a bear: RUN!!!

The morals of the preceding story are: Don't throw things at hungry bears To gather the most information about an object, use a probe that matches the object you want to study.

The tool I use to measure the proton is the Thomas Jefferson National Accelerator Facility

BY THE WAY, HOW DO WE SEE ? Just as light carries information about the physical world because it interacts with what it hits, electrons scattering of small target particles reveal the shape and size of these objects. Here are a two examples with light.

Use scattering to guess the shape of an object What is the shape of the object under the cloud? 1.Square 2.Circle 3.Triangle The pink lines represent rays of light. The light bounces off an object that is underneath the cloud.

Use scattering to guess the shape of an object What is the shape of the object under the cloud? 1.Square 2.Circle 3.Triangle The pink lines represent rays of light. The light bounces off an object that is underneath the cloud.

Change the energy of the probe to guess the shape of an object

To see, we detect with our eyes the information of the bounced-around light. BY THE WAY, HOW DO WE SEE ? Just as light carries information about the physical world because it interacts with what it hits, electrons scattering of small target particles reveal the shape and size of these objects.