Classroom Questions

Questions for ‘Scientists caught a black hole ringing like a bell’ 

Two black holes spiraled around each other before combining into one. Here the black holes are shown as two black dots. This is a computer simulation of the gravitational waves (white and blue) released by that merger.

Deborah Ferguson, Derek Davis and Rob Coyne/URI, LIGO, MAYA Collaboration, simulation performed with NSF's TACC Frontera supercomputer

By Science News Explores

To accompany ‘Scientists caught a black hole ringing like a bell’

SCIENCE

Before Reading:

  1. Imagine the toll of a bell. Can you tell the size of the bell from the sound of its ringing? Explain.
  1. A ratio is a way to compare two numbers. You can read about the concept of ratios in this short article. A signal-to-noise ratio compares two things, such as the sound level of some measured signal to the level of background noise. Which do you think is more desirable, a high signal-to-noise ratio or a low one?

During Reading:

  1. What kind of waves were emitted by the newly formed black hole?
  2. How can scientists use the black hole’s “ringing” to estimate its size? Connect your answer to the bell analogy described in the story.
  3. What does LIGO stand for, and what role did it play in this study?
  4. This is not the first time LIGO has played a role in this type of study. How did the signal-to-noise ratio of the 2025 study compare with that of the 2015 study?
  5. How did improvements to the LIGO detectors contribute to this difference?
  6. Explain how the findings of this 2025 study align with predictions made in 1963 by Roy Kerr. What scientific theory does this support?
  7. Describe the second “matching” occurrence noted during this study. Whose predictions did this support? Why is this study an improvement over previous attempts to support this theory using this approach?

After Reading:

  1. Examine the image comparing the signal frequencies of black hole “ringing” detected by LIGO’s detectors. The 2015 and 2025 graphs each show two lines — a purple and a green one. What does the purple line indicate? What does the green line represent? Which line — purple or green — shows the most significant difference between 2015 and 2025?
  2. Imagine in one study, the signal-to-noise ratio is 1:2. (This ratio can also be represented as ½, or even as 0.5.) It is possible for the signal-to-noise ratio to increase, even as the numbers themselves — the signal or the noise — decrease. Explain how one could increase the signal-to-noise ratio by decreasing one of the values in that starting 1:2 ratio. Write this new ratio in one other format of your choice.