Modern Physics
Modern Physics
In this lesson, you will learn about recent developments in physics. Start by clicking each step in this interactivity. Click the player to begi,.
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Our current understanding of atomic structure is based upon the notion that neutrons and protons are not fundamental particles. The neutrons and protons in the nucleus are each made of three quarks. The quark model was proposed in 1964 by Murray Gell-Mann and George Zweig. Electrons are part of a class of particles called Leptons. Leptons are fundamental particles.
Neutrons and protons are made of three quarks
Up quark has a charge of +2/3 e
Down quark has a charge of -1/3 e
The two types of quarks that make up neutrons and protons are called up and down quarks. A neutron is made of two down quarks and one up quark. A proton is made of two up quarks and one down quark. In the image shown, you can see the up quark represented by a blue "U" sphere and the down quark represented by a purple "D" sphere.
There are actually six types of quarks, but only up and down quarks are commonly found. Quarks have fractional charge. An up quark has a charge of plus two-thirds of an electron charge and a down quark has a charge of negative one third of an electron charge. For neutrons, the total charge of the quarks adds to zero. For protons, the total charge of the quarks adds to positive one electron charge.
View this video clip on Quarks from Discovery EducationTM streaming to learn more about atomic structure.
The Big Bang Theory explains the beginning of the universe. Time, as defined by our universe, only goes back about 15 billion to 20 billions years. In the beginning, the universe was a very small and dense entity which scientists name a "singularity". After a miniscule moment of time, the universe rapidly expanded in an event called "The Big Bang." Right after the big bang, the temperatures and energy present turned everything to what physicists call a quark soup. At this time, all the interactions in physics behaved in the same, unified way. As the universe expanded and cooled during its first second of existence, the fundamental forces differentiated from each other and matter formed.
View this video clip on The Big Bang Theory from Discovery EducationTM streaming to learn more.
Modern Physics Practice
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