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I'm not convinced that the author is as knowldegeable as he thinks he is. quote: "We might expect to see some stars growing brighter throughout the spring on a
by gcthomas 8y ago
I'm not convinced that the author is as knowldegeable as he thinks he is.
quote:
"We might expect to see some stars growing brighter throughout the spring on account of Earth approaching them, and then growing dimmer throughout the fall. There is a name for this sort of effect: parallax. But no one could see any parallax."
Dimmer and brighter through relative motion is parallax now?
- danielvf 8y agoArticle is totally wrong about parallax. It’s relative apparently motion, nothing to do with brightness.
- btilly 8y agoI have no idea why anyone would vote this correct statement down. See https://en.wikipedia.org/wiki/Stellar_parallax https://en.wikipedia.org/wiki/Stellar_parallax for verification.
- skybrian 8y agoParallax does come in separately, in the part about the relative size of the earth's orbit compared to the distance to the stars.
- joshumax 8y agoI had something of a double-take on this part too. A difference in apparent magnitude throughout the year isn't the same as stellar parallax by any means, and is something of a misnomer.
- CydeWeys 8y agoObjects definitely do get brighter* when coming towards you and dimmer when going away from you, but this is special relativity, not parallax. It certainly wasn't known at that time. * The light becomes more energetic, anyway, thanks to blue shift. Whether you count this as brighter depends on how you define brightness.
- abiox 8y agoi found this: https://en.wikipedia.org/wiki/Photometric_parallax_method https://en.wikipedia.org/wiki/Photometric_parallax_method > The photometric parallax method is a method of data analysis used in astronomy that uses the colours and apparent brightnesses of stars to infer their distances.
- theamk 8y agoFrom that link: > Strictly speaking, it does not actually employ any measurements of parallax and can be considered a misnomer.
- abecedarius 8y agoThat page seems to be saying they estimate the star’s brightness by its color, then distance by its apparent brightness. If so, that’s an unfortunate name because it’s been seriously proposed to measure distance by how much the apparent brightness changes at half-year intervals. (But the particular seasons would of course be different for different stars.)
- Florin_Andrei 8y agoThe word "parallax" is not appropriately used in that context. It's a misnomer.
- Nomentatus 8y agoBut "misnomer" also means an inappropriate designation ("lousy choice of rubric") that is nonetheless the official designation. It's correct to refer to Greenland by that name even though it's mostly ice, and therefore a misnomer. https://www.merriam-webster.com/dictionary/misnomer https://www.merriam-webster.com/dictionary/misnomer So the article's author isn't exhibiting ignorance, he just has to use the only word we have, parallax. My favorite misnomer is "bacterial competence." When damaged and so incompetent they need replacement DNA, bacteria open up to allow spare parts (from other similar bacteria that have been blown up) in. The name for this kind of incompetence in bacteria? "Competence!"
- 8y ago
- sandworm101 8y agoPerhaps this poor choice of words meant to say that the stars become brighter as we move towards them simply because the earth is closer to them. On one side of our orbit we should be closer to some stars and further away from others, resulting in a seasonal dimming. That would be logical to anyone who doesn't grasp the distances involved.
- btilly 8y agoThe dimmer and brighter is because when you are closer to a light source it is brighter, and when you are farther from it it is dimmer. So when we are closer to a star, we expect to see it brighter than when we are farther. This effect is seen with planets.
- danielvf 8y agoYes, that’s a real effect, but that’s not the meaning of the word parallax. “Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines” https://en.m.wikipedia.org/wiki/Parallax https://en.m.wikipedia.org/wiki/Parallax