The Signal That Kept Time
In 1967, a strange mark appeared on a long strip of paper at a radio telescope near Cambridge, England. It did not look like the signals the telescope had been built to study. At first, it was just a little patch of “scruff,” as graduate student Jocelyn Bell Burnell called it. Months of careful work would reveal that the mark was evidence of something never seen before: a pulsar.
A radio telescope detects radio waves arriving from space. These waves are invisible to our eyes, so the telescope’s equipment records them in a form scientists can examine. Bell Burnell was helping use the telescope to study distant objects called quasars. She examined many yards of paper recordings, looking for signals that might be worth investigating.
During the summer of 1967, she noticed an unusual bit of signal that appeared again in the same part of the sky. That repeat appearance mattered. Many unwanted signals came from human activity or equipment, but a signal that returned with the stars might have a source beyond Earth. Bell Burnell kept track of the odd signal, even though its first appearances did not show clearly what was causing it.
- investigating:
- looking into something carefully to learn more
- interference:
- an unwanted signal or disturbance that makes another signal harder to study
- artificial:
- made by people rather than occurring naturally
- convincing:
- likely to make someone believe an explanation is true
- milestones:
- important events or stages in a process
- massive:
- very large and heavy
- radiation:
- energy that travels outward as waves or particles
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Preview questions from this passageShowHide
- 11. What is the central idea of the passage, and which two actions support it?
- 22. Why did the signal’s return in the same part of the sky matter?
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About this explanatory article passage for Upper Elementary
“The Signal That Kept Time” is a explanatory article reading passage about Pulsar discovery, written for Upper Elementary. It takes about 3 minutes to read (496 words) and comes with an interactive quiz and a printable worksheet with comprehension questions and an answer key.