Summary:
- This article discusses how a medieval Japanese diary entry from the year 860 AD helped scientists detect a dangerous solar event that occurred at that time.
- The diary entry described a "red sign" in the sky, which scientists believe was likely a solar storm or coronal mass ejection (CME) from the Sun.
- By analyzing the historical record and comparing it to modern scientific data, researchers were able to better understand the frequency and potential impacts of these types of solar events in the past, which can help us prepare for and mitigate their effects in the future.