How Do Scientists Figure Things Out?

What You'll Learn

• Science starts with a question, not an answer
• A hypothesis is a careful guess you can actually test
• A fair test changes only ONE thing at a time and keeps everything else the same
• Evidence is what you actually observed, not what you hoped for
• A wrong hypothesis is still a win — it tells you something true about the world

Words to Know

Hypothesis

A careful guess you can test

"My hypothesis is the sunny plant grows taller."

Experiment

A test you set up to see if your guess is right

"We ran a two-week plant experiment."

Evidence

What you actually saw, heard, or measured

"The evidence was 18 cm versus 9 cm."

Fair test

A test where you change only one thing at a time

"Same water, same pot — only the sunlight changed."

Variable

The one thing you change on purpose

"Sunlight was our variable."

Check What You Learned

Fun Facts

• A scientific investigation starts with a question that can actually be tested and measured

  Source: NGSS Science and Engineering Practice 1, Asking Questions

• A hypothesis is a proposed explanation you can test, not a random guess — it comes with a reason behind it

  Source: NGSS Appendix F, Science and Engineering Practices

• A fair test controls variables: you change one thing at a time and keep everything else the same, or you cannot tell what caused the result

  Source: NGSS 3-5-ETS1-3

• Plants need light to make their own food by photosynthesis, which is why sunlight changes how they grow

  Source: NASA Science, Plants and Photosynthesis

• Evidence is what was actually observed or measured, and in science the evidence outranks what the scientist hoped for

  Source: NGSS Science and Engineering Practice 7, Engaging in Argument from Evidence

• Scientists write down their methods so other scientists can repeat the same test and check the result — being checked is part of the process

  Source: National Academy of Sciences, Science and Engineering Practices