Scientists use research to observe changes over time by conducting longitudinal studies or analyzing existing data sets. Here are the general steps they follow:

1. Formulating research questions: Scientists start by identifying specific research questions or hypotheses they want to investigate. These questions should be focused on observing changes or trends over time.

2. Designing the study: Scientists design a study that allows them to collect data at multiple time points. This could involve selecting a sample of participants, determining the duration of the study, and deciding on the frequency of data collection.

3. Data collection: Researchers collect data at different time intervals. This can be done through various methods such as surveys, interviews, observations, or experiments. The data collected should be relevant to the research questions and allow for comparisons over time.

4. Data analysis: Scientists analyze the collected data to identify patterns, trends, or changes over time. They may use statistical techniques to examine the data and determine if there are significant differences or relationships between variables across different time points.

5. Interpretation and conclusions: Based on the analysis, scientists interpret the findings and draw conclusions about the observed changes over time. They may also discuss the implications of these changes and their potential causes.

6. Publication and peer review: Scientists often publish their research findings in scientific journals, where they undergo a peer-review process. This ensures that the research is rigorously evaluated by other experts in the field before it is accepted and shared with the scientific community.

By following these steps, scientists can effectively use research to observe changes over time and contribute to our understanding of various phenomena.