Editing 2226: Recombination And Reionization
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The {{w|hydrogen line}} is a {{w|spectral line}} of neutral (un-ionized) hydrogen atoms. The electrons in an atom have a property called spin, equal to either 1/2 or -1/2, and one "spin state" of the electron in neutral hydrogen has slightly more energy than the other spin state. This means that when the electron in a hydrogen atom spontaneously switches its spin state, it releases a photon at a certain frequency called the hydrogen line. This line falls in the {{w|microwave}} region of the electromagnetic spectrum, with a frequency of ~1.42 gigahertz (GHz). The wavelength corresponding to this frequency is about 21.1 centimeters, giving it the common name of the 21-centimeter line. In this comic, [[Ponytail]] is attempting to detect the signal of this emission line from the ancient universe, although due to {{w|redshift}}, the line's frequency has decreased from 1.4 GHz to only ~100 megahertz (MHz), putting it in the current {{w|FM broadcast band}}. In most parts of the world, FM radio makes use of frequencies from 87.5 to 108 MHz. | The {{w|hydrogen line}} is a {{w|spectral line}} of neutral (un-ionized) hydrogen atoms. The electrons in an atom have a property called spin, equal to either 1/2 or -1/2, and one "spin state" of the electron in neutral hydrogen has slightly more energy than the other spin state. This means that when the electron in a hydrogen atom spontaneously switches its spin state, it releases a photon at a certain frequency called the hydrogen line. This line falls in the {{w|microwave}} region of the electromagnetic spectrum, with a frequency of ~1.42 gigahertz (GHz). The wavelength corresponding to this frequency is about 21.1 centimeters, giving it the common name of the 21-centimeter line. In this comic, [[Ponytail]] is attempting to detect the signal of this emission line from the ancient universe, although due to {{w|redshift}}, the line's frequency has decreased from 1.4 GHz to only ~100 megahertz (MHz), putting it in the current {{w|FM broadcast band}}. In most parts of the world, FM radio makes use of frequencies from 87.5 to 108 MHz. | ||
| β | The problem that FM radio and the signal for which Ponytail is searching overlap in frequency quickly becomes apparent when tuning to the frequency detects a local radio station rather than the desired signal. The radio station is called Hot 92.7: The Vibe; this indicates that Ponytail is searching for a signal at 92.7 MHz, but there is a [https://vibe927miami.com/ radio station] interfering with it. She demonstrates this to [[Cueball]] by playing the live signal for him, but says that once the radio DJ stops talking, their research will result in a {{w|Nobel Prize}}. This is unlikely, as most radio stations broadcast 24 hours a day without ever stopping (except in cases of power failure, which | + | The problem that FM radio and the signal for which Ponytail is searching overlap in frequency quickly becomes apparent when tuning to the frequency detects a local radio station rather than the desired signal. The radio station is called Hot 92.7: The Vibe; this indicates that Ponytail is searching for a signal at 92.7 MHz, but there is a [https://vibe927miami.com/ radio station] interfering with it. She demonstrates this to [[Cueball]] by playing the live signal for him, but says that once the radio DJ stops talking, their research will result in a {{w|Nobel Prize}}. This is unlikely, as most radio stations broadcast 24 hours a day without ever stopping (except in cases of power failure, which would also affect Ponytail's radio telescope). An unstated joke is that Ponytail's observational setup receives the FM radio signal at all; any actual {{w|radio telescope}} would have incorporated methods from its inception to exclude local sources of radio signals such as FM radio. |
Cueball points out that perhaps the signal is what the supposed primordial hydrogen line actually sounds like during the phase of universe formation called {{w|reionization}}. Ponytail jokes back that the primordial universe must enjoy playing popular singer {{w|Selena Gomez}}. Although it is theoretically possible that a naturally occurring radio transmission might sound like music to humans, it would not contain clearly understandable coherent sentences in a language that did not exist when the transmission was created.{{fact}} | Cueball points out that perhaps the signal is what the supposed primordial hydrogen line actually sounds like during the phase of universe formation called {{w|reionization}}. Ponytail jokes back that the primordial universe must enjoy playing popular singer {{w|Selena Gomez}}. Although it is theoretically possible that a naturally occurring radio transmission might sound like music to humans, it would not contain clearly understandable coherent sentences in a language that did not exist when the transmission was created.{{fact}} | ||
