In the Ted Talk on your LMS, Allan Adams describes an event that was detected by LIGO in 2016. When did it occur?

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BlackTom AI · Accepted Answer

First, let’s restate the scenario to set the context: the question asks about a specific event detected by LIGO in 2016, as described in Allan Adams' Ted Talk. The options present different timescales for when that event occurred.
Option 1: 'Hundreds of years ago' — This is inconsistent with the nature of LIGO detections of gravitational waves, which come from astronomical sources far beyond our current human timescale. Gravitational-wave events from black hole or neutron star mergers observed by LIGO are not something that happened within the last few centuries; such events lie on cosmic timescales. Therefore this choice mischaracterizes the temporal scale.
Option 2: 'Millions of years ago' — While millions of years is not a trivial timespan, LIGO-detected events originate from events billions of light-years away in terms of age of the universe, and the actual mergers occur long before any human-era times. However, saying 'millions of years ago' still incorrectly localizes the event to a relatively recent geological timescale rather than a cosmological one. This makes the statement inaccurate in context.
Option 3: 'In the present time' — LIGO detects gravitational waves that are traveling to Earth now, but the actual event being referenced (the source merger) occurred long ago in the distant past. Saying the event occurred in the present time ignores the cosmological travel time of the waves and the large timespan between the merger and detection. This is misleading about the timing of the event itself.
Option 4: 'Over a billion years ago' — Gravitational-wave events detected by LIGO, such as binary black hole mergers, originate from systems that merged billions of years ago, with the gravitational waves taking substantial time to reach Earth. Describing the event as occurring over a billion years ago aligns with the understanding that the source existed and merged deep in the cosmic past, even though we detect the signal now. This framing matches the typical description of such events in educational talks and aligns with the general scale of cosmic evolution involved in these detections.
In summary, the incorrect options either project an inappropriate near-term timeframe (hundreds of years, present time) or underestimate the cosmological timescale (millions of years). The accurate characterization, reflecting the astrophysical and cosmological context of LIGO detections, places the event in an era over a billion years in the past, consistent with the large distances and ages involved in such gravitational-wave events.

My LMS Subjects Quiz Topic 1: The Big Bang

In the Ted Talk on your LMS, Allan Adams describes an event that was detected by LIGO in 2016. When did it occur?

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