Scientific evidence

Scientists look for clues to learn about our world. These clues are called evidence. Evidence can help a new idea. It can also show an idea is wrong.

Sometimes, two people see the same thing. But they might think different things. One person might use what they already know to explain it.

Evidence can even help make new ideas. It can help scientists build new tools. It can also help solve real problems.

Scientists use math to check their clues. This helps them see if the clues are strong. They want to find the truth. It is fun to find clues!

Scientists use clues to test their ideas. These clues are called scientific evidence. Evidence can help support an idea. It can also show that an idea is wrong. Scientists use a set of steps called the scientific method to study evidence. They use math to see if their clues are strong. This is called statistical analysis.

Sometimes, two people look at the same clue. They might still reach different conclusions. This happens because of their background beliefs. These are things they already think are true. For example, two scientists once saw the same changes in a chemical. One used an old idea to explain it. The other used a new idea about oxygen.

Evidence does not just test old ideas. It can also help make new ones. This is called abduction. This means using clues to build a new theory. Some people think we can find absolute proof in science. However, many scientists say that is not possible. They believe new evidence might always change what we know. Instead, they look for a high degree of acceptance for their ideas.

Scientific evidence is a special kind of clue used by researchers. These clues help support an idea or show that an idea is wrong. Scientists use this evidence to solve practical problems too. They follow a set of rules called the scientific method. This way of working ensures the clues are fair and useful. The strength of evidence often depends on math and careful controls.

How a person uses evidence depends on what they already believe. These are called background beliefs. For example, people once thought the Earth did not move. This was because it did not look like it was moving. Later, new evidence showed the Earth moves around the sun. Two people can look at the same clue and see different things. In the past, Priestley used an old idea to explain a chemical change. At the same time, Lavoisier used the idea of oxygen to explain it.

Many thinkers have studied how these clues work over many years. Karl Popper was a famous thinker in 1959. He said evidence can prove a theory is wrong. However, he said evidence cannot prove a theory is always right. This is because new clues might be found later. In the 1950s, Rudolf Carnap suggested three ways to look at evidence. He looked at if it confirms, compares, or measures the strength of an idea.

There are many important names in the history of these ideas. Peter Achinstein wrote a book called The Book of Evidence in 2001. He talked about different kinds of evidence, like subjective or potential evidence. In 1990, William Bechtel described how biologists use four factors to check evidence. These include things like making sure others can repeat the same results. Other thinkers like Carl Hempel and Wesley C. Salmon also studied these rules. These people helped us understand how to trust what we see.

Evidence is not just for testing old ideas that we already have. It can also be used to build brand new ideas. This is called abduction, which means using clues to create a new theory. Ernest Rutherford used this method during a famous experiment. He shot particles through gold foil to learn about the center of an atom. This helped him create a new model of how atoms work. Even though people talk about "scientific proof," many say it does not exist. Instead, scientists look for ideas that most people in their field accept.

Scientific evidence consists of empirical information used to support or counter a scientific theory or hypothesis. Scientists also apply this evidence to solve practical problems or to develop new experimental tools and techniques. For information to be considered scientific evidence, it must be empirical and interpretable through the scientific method. The strength of this evidence is not a fixed value. Instead, it varies based on the specific field of study. Generally, the strength of evidence is determined by the results of statistical analysis and the quality of scientific controls used during testing.

How a person interprets evidence is heavily influenced by their background beliefs. These are the assumptions or prior knowledge a person holds about the world. These beliefs act as a filter for how observations are utilized. For example, the apparent lack of motion of the Earth once served as evidence for a geocentric cosmology, where the Earth was the center of the universe. However, once enough evidence was presented for heliocentric cosmology, that same observation was discounted as evidence for a stationary Earth. This shows that the observer, rather than the observation itself, creates the causal link between a fact and a hypothesis.

One formal way to understand this influence is through Bayesian inference. In this mathematical approach, beliefs are expressed as percentages to show a person's level of confidence. A researcher starts with an initial probability, known as a "prior." They then update this probability using Bayes' theorem after observing new evidence. Because two independent observers might have different priors based on their previous observations, they may rationally arrive at different conclusions from the same event. This demonstrates how personal history shapes scientific reasoning.

Philosophers have long debated the logic of how evidence relates to theories. In 1959, Karl Popper introduced influential ideas regarding the scientific method. He noted an asymmetry between proving a theory right and proving it wrong. Evidence can prove a theory wrong by establishing facts that are inconsistent with it. However, evidence cannot prove a theory is absolutely correct. This is because new, undiscovered evidence might eventually emerge that contradicts the theory. Because of this, many scientists argue that true, infallible "scientific proof" does not actually exist.

Throughout the 20th century, different frameworks emerged to categorize evidence. In the 1950s, Rudolf Carnap suggested three distinct categories. These were classificatory evidence, which confirms a hypothesis; comparative evidence, which supports one hypothesis over another; and quantitative evidence, which measures the degree of support. Later, in 1990, biologist William Bechtel identified four specific factors used to settle scientific controversies. These factors include the clarity of the data, replication by other scientists, consistency with results from alternative methods, and consistency with plausible mechanical theories.

In 2001, philosopher Peter Achinstein published "The Book of Evidence," which organized evidence into four concepts. He identified epistemic-situation evidence, subjective evidence, veridical evidence, and potential evidence. Veridical evidence provides a good reason to believe a hypothesis is true. Achinstein argued that while scientists primarily seek veridical evidence, they also rely on other forms of probability. This work helped distinguish between the different ways researchers weigh the importance of their findings.

Evidence is not only used to test existing ideas; it is also used to create them. This process is sometimes called abduction. A famous example is the Geiger-Marsden experiment involving alpha particles and gold foil. The scientist Ernest Rutherford used the resulting data to calculate the mass and size of an atomic nucleus. He did not just test an old idea; he used the evidence to develop an entirely new atomic model. This shows that the relationship between evidence and science is an iterative process of competition between plausible rival hypotheses.