Our Universe and the Forces that Hold it Together

A few key concepts you need to know first!

Only a theory?

Some basic definitions

• Fact: an observation that has been repeatedly confirmed (If you drop a pencil on Earth, it falls)

• Law: a descriptive generalization about how the physical world behaves (Laws of Motion)

• Hypothesis: a testable statement that can be used to make explanations

Some basic definitions• Theory: a well-substantiated and

accepted explanation that incorporates facts, laws, and tested hypotheses.

In science, you don’t get any better than a theory.

2. Elements-substances that consist of just one type of atom; they cannot be brokendown to other substances

1. Atom-the basic unit of all matter; the smallest unit of matter that retains the properties of an element

Is brass an element?

What about: Oxygen O2

Water H20 Helium He

The structure of the atom

ELECTRON negative,

orbits outside the nucleus

in the ELECTRON

CLOUD

PROTON positive, also

in nucleus

NEUTRON neutral, located in

the NUCLEUS (center of atom)

Force

• The effect on a particle due to another particle's presence.

The Four Fundamental Forces

Gravity

• Gravitational force is the attraction between the masses of two objects.

• The larger the masses, the bigger the attraction.

• The force of gravity can be calculated by:

• Fg = G x m1 x m2 r2

Electromagnetism

• It is necessary to understand that electrical charge (positive/negative) and magnetism (north/south) are different aspects of the same force -- electomagnetism.

• Oppositely charged objects, such as a proton and an electron, attract one another, while particles with the same charge repel each other.

Strong Nuclear Force

• Protons are positively charged so they want to repel against each other.

• The strong nuclear force is what keeps them together

Weak Nuclear Force

• Little is known about the weak nuclear force

• We know that it is responsible for the decay of a neutron into a proton