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It was a little more complicated as to whether the priests (and other astronomers) knew he was right. Heliocentrism made a specific prediction of parallax ---

It was a little more complicated as to whether the priests (and other astronomers) knew he was right. Heliocentrism made a specific prediction of parallax --- namely that the stars would move back and forth over the course of a year. But this wasn't observed which is one of the main reasons that many astronomers remained skeptical of the idea. Tycho Brahe proposed an alternative model that adopted many of the advantages of heliocentrism but didn't have the parallax problem. In his theory all the planets revolved around the Sun, but the Sun revolved around the Earth. Of course it turned out that the stars were much, much further away than anyone expected, so the parallax effect was too small to be seen until the 19th century. But your broader point is correct, Galileo's troubles were brought about more due to his political indiscretions than his astronomy per se.

verisimi 4y ago
> Of course it turned out that the stars were much, much further away than anyone expected, so the parallax effect was too small to be seen until the 19th century. How do we know how far away the stars are? (serious question)
- DavidSJ 4y ago
  This very parallax effect. We know how far the Sun is from the Earth, and the Earth has moved twice this distance from January 1 to July 1. This in turn allows us to extrapolate distance to some of the nearest stars by their apparent motion relative to the other, "fixed" stars. https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://www.youtube.com/watch?v=7ne0GArfeMs https://www.youtube.com/watch?v=7ne0GArfeMs
  - avn2109 4y ago
    OK but then how do we know how far the sun is from the earth? Is it like "bounce a signal off it and count time of flight?" (Another serious question.)
    - bombcar 4y ago
      > The first rigorous and accurate scientific measurement of the Earth-Sun distance was made by Cassini in 1672 by parallax measurements of Mars. He and another astronomer observed Mars from two places simultaneously. A century later, a series of observations of transits of Venus provided an even better estimate. http://curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate http://curious.astro.cornell.edu/about-us/41-our-solar-syste...
    - BurningFrog 4y ago
      We can't bounce signals off the sun, but we can do "interplanetary radar" bouncing signals off at least the nearby planets. Knowing those distances, the distance to the sun becomes a trigonometry problem.
    - DavidSJ 4y ago
      The video of Terence Tao I linked addresses that and many other questions about climbing the cosmic distance ladder.
- dylan604 4y ago
  I read this book, "Measuring The Cosmos", a few years ago, and it talks about the various ways we use to establish distances to such far objects. The book describes how we grew our "measuring tape" so to speak. We started with learning accurate distances to things closer, the distance from the Sun to Earth, an AU, being one of those. That's useful for local solar system distances, but the numbers become too big for human consumption when measuring further objects. Light years became the next rung on the ladder. Parsecs next, etc. Now, we use certain types of stars like pulsars that have known brightness for the particular frequencies. Once we find a new pulsar that matches, we can compare how bright it is to others of the same type. If it is brighter, it is closer. If it is dimmer, it is further away. I'm way way oversimplifying it, but hopefully it gets the concept across. https://www.amazon.com/Measuring-Cosmos-Scientists-Discovered-Dimensions/dp/0813534046 https://www.amazon.com/Measuring-Cosmos-Scientists-Discovere...
deleted 4y ago
[deleted]
DavidSJ 4y ago
Another point, discussed in Arthur Koestler's The Sleepwalkers (I'm going from memory, so there may be slight errors), is that the Copernican model was pretty ugly: 1. It actually required more epicycles than the Ptolemaic model. 2. It didn't even have the other planets orbit the Sun! Rather, they orbited the center of the Earth's orbit (???). Kepler's laws fixed all of this, but Galileo ignored all of Kepler's correspondence, except for one time when he found it profitable to use him: He had made claims about the Jovian moons based on observations through his telescope, but he refused to let other astronomers borrow that instrument so they could reproduce his observations. Kepler wrote to Galileo offering to defend him, and Galileo accepted. Then later, after Kepler had already publicly defended him and himself requested access to the telescope to verify the observations, he was ignored, as per all other times Kepler wrote him before and after.
- triknomeister 4y ago
  Well, both things are wrong, planets do not orbit the sun or the center of earth's orbit, but the center of solar system, which is actually outside the sun.
  - cygx 4y ago
    It's true that due to the large mass of Jupiter, the barycenter of the solar system lies outside the surface of the sun. However, the barycenter of any sun/planet 2-body system besides Jupiter lies within the sun's surface, so I'm quite comfortable with the claim that at the very least most planets do orbit the sun...
yeasurebut 4y ago
The Greeks wrote in jest they hope that no one climbs to the top of Olympus, they would revolt upon finding there are no gods there. To an extent those in the upper echelons of human society have always known the magical stories were bogus. But when the flock is dumber than Humperdoo himself, Humperdoo will do.

verisimi 4y ago

> Of course it turned out that the stars were much, much further away than anyone expected, so the parallax effect was too small to be seen until the 19th century. How do we know how far away the stars are? (serious question)

DavidSJ 4y ago
This very parallax effect. We know how far the Sun is from the Earth, and the Earth has moved twice this distance from January 1 to July 1. This in turn allows us to extrapolate distance to some of the nearest stars by their apparent motion relative to the other, "fixed" stars. https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://en.wikipedia.org/wiki/Cosmic_distance_ladder https://www.youtube.com/watch?v=7ne0GArfeMs https://www.youtube.com/watch?v=7ne0GArfeMs
- avn2109 4y ago
  OK but then how do we know how far the sun is from the earth? Is it like "bounce a signal off it and count time of flight?" (Another serious question.)
  - bombcar 4y ago
    > The first rigorous and accurate scientific measurement of the Earth-Sun distance was made by Cassini in 1672 by parallax measurements of Mars. He and another astronomer observed Mars from two places simultaneously. A century later, a series of observations of transits of Venus provided an even better estimate. http://curious.astro.cornell.edu/about-us/41-our-solar-system/the-earth/orbit/87-how-do-you-measure-the-distance-between-earth-and-the-sun-intermediate http://curious.astro.cornell.edu/about-us/41-our-solar-syste...
  - BurningFrog 4y ago
    We can't bounce signals off the sun, but we can do "interplanetary radar" bouncing signals off at least the nearby planets. Knowing those distances, the distance to the sun becomes a trigonometry problem.
  - DavidSJ 4y ago
    The video of Terence Tao I linked addresses that and many other questions about climbing the cosmic distance ladder.
dylan604 4y ago
I read this book, "Measuring The Cosmos", a few years ago, and it talks about the various ways we use to establish distances to such far objects. The book describes how we grew our "measuring tape" so to speak. We started with learning accurate distances to things closer, the distance from the Sun to Earth, an AU, being one of those. That's useful for local solar system distances, but the numbers become too big for human consumption when measuring further objects. Light years became the next rung on the ladder. Parsecs next, etc. Now, we use certain types of stars like pulsars that have known brightness for the particular frequencies. Once we find a new pulsar that matches, we can compare how bright it is to others of the same type. If it is brighter, it is closer. If it is dimmer, it is further away. I'm way way oversimplifying it, but hopefully it gets the concept across. https://www.amazon.com/Measuring-Cosmos-Scientists-Discovered-Dimensions/dp/0813534046 https://www.amazon.com/Measuring-Cosmos-Scientists-Discovere...

deleted 4y ago

[deleted]

DavidSJ 4y ago

Another point, discussed in Arthur Koestler's The Sleepwalkers (I'm going from memory, so there may be slight errors), is that the Copernican model was pretty ugly: 1. It actually required more epicycles than the Ptolemaic model. 2. It didn't even have the other planets orbit the Sun! Rather, they orbited the center of the Earth's orbit (???). Kepler's laws fixed all of this, but Galileo ignored all of Kepler's correspondence, except for one time when he found it profitable to use him: He had made claims about the Jovian moons based on observations through his telescope, but he refused to let other astronomers borrow that instrument so they could reproduce his observations. Kepler wrote to Galileo offering to defend him, and Galileo accepted. Then later, after Kepler had already publicly defended him and himself requested access to the telescope to verify the observations, he was ignored, as per all other times Kepler wrote him before and after.

triknomeister 4y ago
Well, both things are wrong, planets do not orbit the sun or the center of earth's orbit, but the center of solar system, which is actually outside the sun.
- cygx 4y ago
  It's true that due to the large mass of Jupiter, the barycenter of the solar system lies outside the surface of the sun. However, the barycenter of any sun/planet 2-body system besides Jupiter lies within the sun's surface, so I'm quite comfortable with the claim that at the very least most planets do orbit the sun...

yeasurebut 4y ago

The Greeks wrote in jest they hope that no one climbs to the top of Olympus, they would revolt upon finding there are no gods there. To an extent those in the upper echelons of human society have always known the magical stories were bogus. But when the flock is dumber than Humperdoo himself, Humperdoo will do.