IN SCIENCE

HYPOTHESES, THEORIES, AND LAWS

HYPOTHESIS• A hypothesis is a reasonable guess based on what you know or observe

• A hypothesis is part of the scientific method (so hypotheses are proved and disproved all the time)

• A hypothesis must be tested and retested many times before it is accepted as true by the scientific community

THEORY

• Theories are explanations of natural phenomena based on repeated evidence

• A theory consists of one or more hypotheses that have been supported through MANY repeated tests

• Theories are widely accepted as true in the scientific community (although they can be improved upon or disproven)

• Examples include:

• Theory of gravity

• Cell theory

• Theory of evolution

LAW

• A law is always true

• A law cannot EVER be shown to be wrong (which is why there are lots of theories in science but very few laws)

• Laws are often expressed as mathematical equations

• Laws of thermodynamics

• Boyles’ law of gasses

• Laws of gravitation

BIG HISTORY

DEEP TIME

BIG HISTORY

Ted Talk: The History of Our World in 18 Minutes

https://www.ted.com/talks/david_christian_big_history?language=en#t-1035293

HOW OLD IS EARTH?

Roughly 4.5 BILLION years old!

Arguably, a number that is a bit hard to grasp, so let’s put it on a timescale that we’re familiar with.

HOW DO WE KNOW?• Hubble

• Measuring the age of stars

• Measuring speeds and distances of galaxies

• Fossils & Sedimentary rock

• Stratigraphy

• Radioactive decay

• Using known decay rates of certain isotopes

“Mystic Mountain”

GEOLOGIC

CLOCK

JURASSIC WORLD

BUT… TIME IS CRAZY!

Less time separates us (humans) from the Tyrannosaurus Rex than separates the Tyrannosaurus Rex from the Stegosaurus!!!