Keysh

11 ms·

121.
by Keysh 5y ago
I kind of assumed that a YouTube video on that subject would be a waste of time, and boy was it. That was amazingly ignorant. Galaxies are often isolated. They come in clusters, and also in groups, and in isolation (including isolated gal
122.
by Keysh 5y ago
This seems to suffer from the usual problem of non-astronomers not understanding the breadth of the problem they think they're trying to solve. That is, they've vaguely heard that the problem is in the rotation of disk galaxies, a
123.
by Keysh 5y ago
That's not how epicycles were used. Ptolemy set up the standard geocentric model with epicycles (and deferents and equants), and these were used more or less unchanged for over a thousand years. When, in the late medieval period, some
124.
by Keysh 5y ago
"Chinese astronomers recently published research on 591 high-velocity stars in our galaxy [2, 3], and 43 of these were hypervelocity stars, moving at relativistic speeds and destined to eventually escape the Milky Way entirely." A
125.
by Keysh 5y ago
No; that’s a potential use of upgraded, more capable rotorcraft in future missions.
126.
by Keysh 5y ago
Many dinosaurs were warm-blooded; fossils of dinosaurs have been found in Antarctica (granted, that’s from a time when the global climate was warmer and Antarctica was ice-free, but still...).
127.
by Keysh 6y ago
I think that's perhaps rather generically true for premodern times. I've seen estimates of mortality rates for medieval England that have cities consistently higher than rural areas, so you'd have to have migration to the cit
128.
by Keysh 6y ago
> until the 20th century, with Beijing* as the primary exception, big cities were in Western Asia, North Africa, and Europe > Why did rice-growing areas have villages while wheat areas developed cities? I'm sorry but that's
129.
by Keysh 6y ago
Yes, exactly. (The Triangulum Galaxy, M33, can sometimes be seen; at ~ 3 million light years, it’s further away and thus an even older “snapshot” than Andromeda.)
130.
by Keysh 6y ago
I’ve seen it from fairly high in the Sierra Nevadas, far from any cities, and I still think it’s very faint.
131.
by Keysh 6y ago
To be a bit pedantic: that’s only true for the Andromeda Galaxy (distance ~ 2,4 million light years), which is very hard to see with the naked eye. The Large and Small Magellanic Clouds are easy to see (from the Southern Hemisphere), but
132.
by Keysh 6y ago
If the jet only turned on a finite time ago, then it will only have gotten so far in that time, so it will have a length = (jet velocity) * (time jet has been active).
133.
by Keysh 6y ago
I think you need to take what Loeb is saying with a very large grain of salt. There's a fair amount of annoyance and disgust within the astronomical community at his misrepresentation of what other astronomers have or have not been doi
134.
by Keysh 6y ago
The land bridge connected Australia to New Guinea and the eastern parts of Indonesia , not to India. No one has any idea what the precise relation of Australian languages to any other set of human languages is.
135.
by Keysh 6y ago
There are, even today, languages that lack words for numbers higher than 2, 3, or 4 -- including a number of Australian languages. This tends to be more true for languages of contemporary hunter-gatherer. (See, e.g., Caleb Everett's N
136.
by Keysh 6y ago
A third possibility is one of the stars used to be much brighter for whatever reason. This is an idea that's been tossed around for a while; it has the problem that ancient Greek discussions agree that there were only six stars visib
137.
by Keysh 6y ago
No, because only about 10% of normal (baryonic) matter is actually in the form of stars. The rest is mostly in the form of hot, dilute gas in intergalactic space. The idea that about 5% of the total mass-energy budget of the universe is in
138.
by Keysh 6y ago
Well, nor can Occam's Razor, but we don't seem to have a problem quoting that! Occam's Razor is not an argument or explanation. It's a heuristic for discriminating among different arguments/explanations. And anthr
139.
by Keysh 6y ago
The bee paper referenced in the original article (Dacke & Srinivasan 2008) is about real bees, and does a pretty good job of showing that the bees must somehow be keeping numerical track of how many instances of a particular landmark th
140.
by Keysh 6y ago
Not really, because "missions without sample returns" (aka "flyby/impactor") is one of the options considered.
141.
by Keysh 6y ago
No one in astronomy uses TIFFs. Most scientific images are stored in FITS format, either in integer form for some raw data or in floating-point form.
142.
by Keysh 7y ago
"it took another 200 years to detect parallax" However, the aberration of starlight was detected in the early 1700s. Although no one had thought to predict its appearance, people quickly realized it only made sense if the Earth wa
143.
by Keysh 7y ago
And what observations were these? (And I wish you'd stop this nonsense of implying that Galileo had his own special heliocentric model. He didn't; he was advocating the model of Copernicus .)
144.
by Keysh 7y ago
That would be difficult, since it isn't true. The Church had banned Copernicus's book and the general concept of heliocentrism in 1616, which was a full 16 years before they went after Galileo for promoting heliocentrism.
145.
by Keysh 7y ago
No, it is pretty random, just as the orbits of binary stars are randomly oriented. The scales of star and solar-system formation are much, much smaller than the scale of the galaxy, so the memory of the latter has been scrambled by all
146.
by Keysh 7y ago
The period of the vertical orbit is closer to 1/3 that of the planar orbit: roughly 70 million years, versus about 225 million years for the azimuthal ("horizontal") period. Since the periods aren't in an integer ratio (
147.
by Keysh 7y ago
It's basically random; the rotation of a solar system depends on the rotation of the gas clump that collapses to form the star and its system, and that depends on local details about the relative orientation of local gas clumps, the
148.
by Keysh 7y ago
We don't define galaxies in general to spin in the opposite direction. Just the Milky Way. (The reason for this seems to be that Galactic "North" was defined long before we had the data to determine which way the Milky Way
149.
by Keysh 7y ago
> Multiple hominid species on Earth have had a technology gap on an unfathomable timescale. Indeed, the Denisovans developed stone tools tens of thousands of years before our own species. Nonsense. Hominin toolmaking and tool use go back
150.
by Keysh 7y ago
That the church rejected heliocentrism because it clashed with scripture is a common misinterpretation. No, it's the simple truth, as the Church and other documents from the time attest. Galileo's model did not match the observ

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