Editing 2926: Doppler Effect
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==Explanation== | ==Explanation== | ||
− | [[Miss Lenhart]] is teaching | + | {{incomplete|Created by an ALARMED BOT THAT GOES NYOOOOM, updated by I AM NO SIREN EXPERT BUT... - Please change this comment when editing this page. Do NOT delete this tag too soon.}} |
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+ | [[Miss Lenhart]] is teaching a class about the concept of {{w|redshift}} in the light from distant galaxies. She states that why this occurs is an interesting question, then follows this by talking about the {{w|Doppler effect}} of sirens. While this is commonly used as an analogy for the concept of the Doppler Shift, and is hence relevant to the preceding topic, [[Miss Lenhart]] appears to have raised it for a completely unrelated purpose - she simply has a special interest in sirens. This becomes apparent as her explanation quickly becomes extraneous to the preceding topic of astronomy, the field in which she teaches, similar to [[1519: Venus]]. | ||
− | + | Emergency vehicles usually have different siren tones, which they can switch between for different circumstances : long NYEEEOOOWWW to alert people in a distance and short PYEEW PYEEW when they are closer to drivers (for example when crossing an intersection). | |
− | In the second and third panels, Miss Lenhart talks about the strange | + | In the second and third panels, Miss Lenhart talks about the strange noise sirens (and cars) make when the pass you. The usual explanation of Doppler effect is that the source of the sound waves is moving and the sound/wavelength can be different depending on whether it is coming towards you or away from you (for details/explanation see the {{w|Doppler effect}} wiki link above). |
− | Redshift is the same concept applied to | + | Redshift is the same concept applied to wavelength of light. Red has a longer wavelength than blue, so light-emitting objects get red when they move away from us and blue when they move towards us. We usually talk about redshift and not blueshift because while stars in our galaxy can move in any direction relative to us, most other galaxies are moving away from us. The fact that more distant galaxies are moving away quicker the farther away they are shows that the universe is expanding. |
− | Unlike the usual explanation of redshift as equivalent to the Doppler effect for sirens, a major component of the redshift of light from distant galaxies is due to the expansion of space in between us and the light source. This effect is not an important component of the Doppler shift for sirens. | + | Unlike the usual explanation of redshift as equivalent to the Doppler effect for sirens, a major component of the redshift of light from distant galaxies is due to the expansion of space in between us and the light source. This effect is not an important component of the Doppler shift for sirens. Redshift has been mentioned multiple times before, such as in [[2764: Cosmological Nostalgia Content]] and [[2853: Redshift]]. |
− | The title text claims that the Doppler effect particularly affects sirens. This isn't actually true, but it may seem like it because | + | The title text claims that the Doppler effect particularly affects sirens. This isn't actually true,{{cn}} but it may seem like it because sirens tend to employ a recognisable tone (or a given sequence of them), which most people who aren't {{w|Amusia|totally tone deaf}} would have experienced a shift of from a passing vehicle's siren, whereas something less distinctinve like engine noise could change according to differences of speed and the gearbox. Then it claims that the emoji for sirens is red because they're associated with redshift. Actually, the emoji is a picture of the rotating light on top of emergency vehicles; these tend to be used in conjunction with sirens, and they're red because this color typically signifies danger or warning. |
==Transcript== | ==Transcript== |