How does science know what it knows?


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How does science know what it knows?


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You want answers. Science asks questions.

Got an important decision coming up? Just curious about how the world works? Science can help.

But science isn’t about being 100% sure. In science, we learn by asking questions.

Science is a process.


Ask questions & spark ideas


Observe & experiment


Try it again or see if others can

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Science changes what we know.

Science challenges—and changes—what we know. To test ideas and search for answers, scientists observe and experiment. Through this process, we update and expand our knowledge.

After all, plenty of things scientists “knew” 100 years ago turned out to be wrong. If we keep asking questions and challenging what we know, just think how much we can learn in the next 100 years!

To learn from science, we:

Keep an open mind

Listen to the data

Build confidence when many studies agree

What if scientific studies disagree?

Why scientific studies may have different results, even when their methods are the same

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For stronger evidence, look for multiple studies

Want to know “what the science says”? Look for multiple studies on a topic rather than just one.

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Can science help people make decisions?

Yes, but be sure to look at the broader context and assess the strength of the evidence

Science is a team sport.

Scientists spend a lot of time doing similar studies over and over, testing and building on each other’s work. When many studies come to similar conclusions, we can be more confident that those conclusions are right. This can lead to scientific consensus and help build knowledge.

But what happens if studies point to different conclusions?

When studies disagree, it’s useful to try to find out why. Sometimes, frustration leads to new discoveries! By working together and sharing information, we can make science stronger and have more confidence in the results.

Finding Hope in Failure
Finding Hope in Failure

Can disagreement lead to discovery? In one scientist’s quest to cure cancer, hope rises from the ashes of failure.

Repeat After Me
Repeat After Me

Why scientists repeat studies—and why that’s harder than you might think

Lessons from the Leading Edge
Lessons from the Leading Edge

Early studies on COVID-19 hold lessons for any new area of science: approach with caution and stay open to change

Why can we trust the information provided by scientific research?

Science is the best way we know to develop reliable knowledge. It’s a collective and cumulative process of assessing evidence that leads to increasingly accurate and trustworthy information.


Credit: August Allen, Polar Field Services/NSF

Science can help you.

If scientific knowledge is always changing, how can we use science to inform decisions?

Think of science like a giant web of knowledge. Any particular strand could break or change, but the overall web holds up. Our web of knowledge grows stronger as we do more studies and become more confident in their results.

People use science to inform lots of decisions. You might look to science to learn what products are safe to use or what foods are healthy to eat. Doctors use science to decide how to diagnose and treat disease. Farmers use science to decide what crops to plant.

Science can’t make these decisions for you. But it can help. It’s a good idea to look at the overall body of knowledge, think critically, and consider the context.

Science can offer many useful answers. But remember, there are always more questions to ask!

Test your knowledge about how science works

The materials on this page are based on Reproducibility and Replicability in Science, a consensus report of the National Academies of Sciences, Engineering, and Medicine. The study and these materials were funded by the Alfred P. Sloan Foundation and the National Science Foundation and vetted by experts in the practice, interpretation, and application of science.