The Nature of Science What is science?

Scientific Principles… Science seeks to explain the natural world and its explanations are tested using evidence from the natural world.

…Science can be a roundabout path to the truth.

…Science corrects itself.

…Science is conducted by humans.

Science requires… Evidence Logical Thinking Creativity Skepticism Open-mindedness

Characteristics of Science Conclusions tentative Better information replaces existing info May be biased, subjective Explains natural, not supernatural

Characteristics of the Scientific Process Founded on observations Conclusions developed through reasoning Tests subject to peer review and replication

The Process of Science How does it work?

There is no such thing as "THE Scientific Method."

A Scientific Method Observation Explanation Test AnalyzeCommunicate

Realistic Scientific Process 1. Observe 2. Ask question 3. Form hypothesis 4. Test 5. Repeat test 6. Analyze results 7. Form new hypothesis 8. Ask new question 9. Test 10. Analyze results 11. Repeat test 12. …

Goals of scientific process Disprove hypotheses to weed out explanations Find the best current explanation

There are two possible outcomes: If the result confirms the hypothesis, then you’ve made a measurement. If the result is contrary to the hypothesis, then you’ve made a discovery. – Enrico Fermi

VARIABLES DEPENDENT  Outcome will depend on what you change. – What is being measured – Graphed on the y-axis INDEPENDENT  factors that you consciously change – What is being manipulated – Graphed on x-axis

An experiment… Beta-carotene supplements have been thought to protect against cancer. However, a study published in the Journal of the National Cancer Institute suggests this is false. The study was conducted with 39,000 women aged 45 and up. These women were randomly assigned to receive a beta-carotene supplement or a placebo, but they all followed the same diet and exercise routine. Their health was studied over their lifetime. Cancer rates for women taking the beta- carotene supplement did not differ systematically from the cancer rates of those women taking the placebo. placebo

Can you determine? Experimental group – women taking beta carotene Control group – women taking placebo Independent variable – supplement Dependent variable – cancer rates Control – Placebo Constants – Over 45, diet, exercise routine

Hypothesis vs. Theory Hypothesis – Testable explanation for an observation Theory – A well tested explanation based on evidence, experiments, hypotheses, observations, etc.

Writing a hypothesis (If…then, because) If (independent variable) then (dependent variable), because (reason why the relationship exists). Examples: – IF Family Guy is on, THEN I will accomplish less homework, BECAUSE I will be distracted. – IF a plant gets more sun, THEN the plant will grow more, BECAUSE more photosynthesis will occur and produce glucose for the plant to grow.

Example Ms. Loch noticed that students who came in for extra help were scoring higher on tests than their classmates. IF students come in for 1 hour/week of extra help, THEN they will score 10% higher on tests, BECAUSE they are getting questions answered and studying longer.

Putting It All Together Sarah was interested in studying the effects of lack of sunlight on the height of plants. She took two identical trays and filled them with the same type of soil and planted the same type of seed in each. She then decided that she would keep one tray in a room that was completely dark and the other on the window ledge. She watered each with 50 mL of water a day.

Answers Question – Does light affect the growth of plants? Hypothesis – If a plant is placed in the dark, then it will not grow as tall as plant in normal sunlight, because it will not be able to photosynthesize and grow.

Answers continued… Independent Variable – Amount of light Dependent Variable – Plant growth Control – Plant on window ledge Constants – Amount of water, type of soil, type of seed, trays