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# Tag Info

89

Impacting solar system objects would have relative closing speeds from around 11 to 72 km/s. We could take the optimal case that the asteroid approaches whilst fully lit by the Sun (which I think precludes the minimum and maximum speed in the range quoted above) and then scale from another similar body - say the asteroid Vesta. This has a diameter of around ...

41

The answer is ironic: Without good instruments, there is no evidence. The people who thought that the Sun went around the Earth were perfectly correct as far as the actual evidence went until the early 1700s and mid-1800s when two lines of evidence opened up that showed that the Earth moved. Aberration of Starlight Wikipedia has a correct but over-...

33

Ole Rømer did not measure a change in the frequency of light. He measured an apparent change in the orbital period of Io, one of Jupiter's moons. The orbit of Io can be measured very accurately by observing when it enters or leaves the shadow of Jupiter. When the Earth is moving away from Jupiter, Rømer noted that the orbit of Io appeared to be very ...

29

Kepler's account of how the third law came to be is as follows (Caspar p.286; emphasis mine): On the 8th of March of this year 1618, if exact information about the time is desired, it appeared in my head. But I was unlucky when I inserted it into the calculation, and rejected it as false. Finally, on May 15, it came again and with a new onset conquered ...

27

You make a great point. The reason behind the discrepancy between the dates is due to a complicated history behind it. The calendar is based on the calendar created by ancient Romans, which is based on one Moon cycle. One lunar cycle is 29.53 days. www.universetoday.com/20620/lunar-year/ which does not evenly divide into the 365.25 days of ...

24

Kepler's third law is trivial (in my opinion) compared to his first law. I am quite impressed that he was able to deduce that the orbits were ellipses. To get that, he had to go back and forth plotting Mars' direction from Earth and Earth's direction from Mars. He knew the length of both planets' years, so observations taken one Mars year apart would differ ...

23

Olber's Paradox was created at a time before the idea of a finite universe was accepted. (It was thought of in the 1600's). In order to resolve Olber's Paradox, you have to introduce the idea that either the universe had a beginning or it is of finite size. (Note: the solution does not require an expanding universe). So, at the time, it was a paradox. ...

22

Johannes Kepler Wikipedia: "However, childhood smallpox left him with weak vision and crippled hands, limiting his ability in the observational aspects of astronomy." He made great use of Tycho Brahes great systematic observations in his theoretical work. He did not need exceptional eyesight for his developments in optics and telescopes.

20

The book The Transits of Venus, by Sheehan and Westfall, describes how Aristarchus used Hipparchus' calculation of the Earth-Moon distance, who in turn used Eratosthenes' calculation of the Earth's circumference, to calculate the Earth-Sun distance. Aristarchus of Samos was the first to seriously calculate the distance to the Sun, using geometry. When the ...

20

Following a reference to Darley et al., ApJ 746, 61 (2012) from your Wikipedia link gives a (very technical) discussion of nova progenitors, including distinctions between nova systems where the secondary stars are main sequence or supergiant stars, and distinctions among white dwarfs with different chemistries. The first sentence of that paper is A ...

19

You cannot prove that the Earth orbits the Sun rather than vice versa because this goes very much against the grain of all frames of reference being equally valid (but some make a lot more sense than others). For example, it makes much more sense to use an Earth-centered, Earth-fixed point of view rather than a non-rotating geocentric, heliocentric, ...

18

1. Ancient cultures observed the sky Night skies are naturally dark and there was no light-pollution in ancient times. So if weather permits, you can easily see a lot of stars. No need to tell about the Sun and the Moon. Ancient people had good reasons to study the night skies. In many cultures and civilizations, stars (and also the Sun and the Moon) where ...

15

The authors assume a geocentric universe (first thing that is wrong). They then assume that the planet Mars has the same apparent diameter as a globe 30 yojana in diameter (about 150 miles) in the same orbit as the moon, from a perspective at the centre of the Earth. This is just stated, and appears to be supposition. It is an incorrect figure. It is ...

13

Despite of the explanation of your question, it is a valid question to ask why planets all have Roman names. First of all, the Romans could, like the Greeks and Sumerians, could only see Mercury, Venus, Mars, Jupiter and Saturn. These planets can be seen with the naked eye. However, the fact that the Romans could see these planets, didn't give all the ...

12

From wikipedia, the rings of uranus The definitive discovery of the Uranian Rings [...] use[d] the occultation of the star SAO 158687[...] The star SAO 158687, also cataloged as HD 128598 is a magnitude 8.7, orange dwarf star in Libra. There seems to be nothing special about the star, except that one day, a planet passed in front of it.

12

If you start with the idea that the planets, the sun, the moon and the earth are all bodies that all move through space, exclude the apparently fixed stars, and then see what evidence there is as to how they move relative to each other, then in that context there is some evidence to be found in naked-eye astronomy aided by navigational instruments available ...

11

It was Nova Aquilae 1918. Wikipedia has some detail. https://en.wikipedia.org/wiki/V603_Aquilae Apparently it was discovered by Zygmunt Laskowski, an amateur astronomer.

11

I'm pretty certain it is the 200inch Hale telescope at Palomar Observatory. There is an image galley of the 200 inch telescope. According to Richard Preston's book First Light: The Search For The Edge Of The Universe, Einstein attended the completion of the telescope truss, yoke and horseshoe bearing at Westinghouse Electric and Manufacturing Company in ...

11

I don't have a full historical perspective on this, perhaps someone could add more, but in the past an astronomer could formulate a hypothesis, design an observation schedule, and then hire and coordinate a group of people to cary out the observations and photographic plate exposures develop and analyze those plates measure and reduce the data and then ...

10

Searching for the definition in dictionary.com you can find this under the word origin and history section: Late 14c., "the eye socket," from Old French orbite or directly from Medieval Latin orbita, transferred use of Latin orbita "wheel track, beaten path, rut, course, orbit Astronomical sense first recorded 1690s in English; it was in classical ...

10

After researching a bit more, I think I can answer my own question (or at least share what I have found). When Kepler derived his laws using Tycho Brahe's observational data of Mars, he followed the procedure below: first, the orbital period of Mars must be known. This value was already known in the time of Kepler (aprox. 687 days) $^1$, and can be derived ...

10

It wasn't one person. René Descartes had theorized that planets must be in the shape of prolate spheroids. Christiaan Huygens and then Isaac Newton theorized that a rotating, self-gravitating fluid body would relax itself into an oblate spheroid. So which view was correct? Giovanni Cassini argued strongly that Descartes' view was the correct one, and he ...

9

First off, pairing a classic dob with a DSLR is a bit like a shotgun marriage. A dobsonian is fundamentally a visual telescope. Most manufacturers don't even consider the possibility that these instruments could be used for data collection via a sensor. There are 2 issues here: 1. The dobsonian is not tracking The sky is moving, the dob stays still. You ...

9

It is indeed possible to measure the AU using transits of Mercury, and Edmund Halley tried to do just that in 1677. However, there are two advantages to a transit of Venus. The first is that during the transit, Venus is only 0.28 AU from Earth, whereas Mercury is about 0.7 AU away. This makes the parallactic effect twice as big. The second difficulty is ...

9

A carbonaceous condrite has the same reflectivity as the moon at around 7-13%. If there was ice, if the tail was 10 times smaller than hail bopp, it would have auspiciously covered half of the sky. it could have made an incredible display in the 1-2 days preceding the collision, because it was as close to the sun as hale bopp, the brightest astronomical ...

8

In the absence of the lighting levels in cities, there are a number of objects in the night sky that are easily seen to move against the background of stars: the Sun, the Moon, Venus, Jupiter, Saturn, Mars and Mercury. These are obvious to anyone who looks at the sky regularly from any dark sky site on clear nights, like most places in the pre-industrial ...

8

The seven who convicted were Felice Centini, Desiderio Scaglia, Antonio Barberini, Berlinghiero Gessi, Fabrizio Verospi, Guido Bentivoglio and Marzio Ginetti. And as you note Francesco Barberini, Laudivio Zacchia and Gaspare Borgia did not. These three didn't vote to acquit, they were just absent from the signing of the condemnation - we don't know why All ...

8

As Wikipedia explains in the article on the Zodiac, the Zodiac was originally developed with the assumption of fixed equinoxes. It is assumed this is because the Babylonians who developed the Zodiac were unaware of the precession of the equinoxes. At that time, about 2500 years ago, the vernal equinox did in fact lie in Aries. For this reason, in astrology, ...

8

Everyone expected exoplanets to exist - there was no reason to suppose that the conditions that existed when the sun formed were unique, and we knew that multiple star systems were common. Newton wrote "And if the fixed stars are the centres of similar systems, they will all be constructed according to a similar design" Observations in the 80s were not ...

8

This question is a bit tricky because it's uncertain as to what counts as "discovering" an exoplanet. Today, we count an exoplanet as having been discovered if it can be detected either by two separate techniques or three separate transits (if found via the transit method). Some of the very very early hunts for exoplanets did indeed find them, but many of ...

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