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How Raganwald Lost His Crown (braythwayt.com)
137 points by braythwayt on Dec 29, 2017 | hide | past | favorite | 47 comments

Binaries almost never form from stars “wandering” and “encountering” other stars. Current scientific understanding is that almost all stars are formed as binaries in the first place.

Thank you!


From Wikipedia: While it is not impossible that some binaries might be created through gravitational capture between two single stars, given the very low likelihood of such an event (three objects are actually required, as conservation of energy rules out a single gravitating body capturing another) and the high number of binaries, this cannot be the primary formation process. Also, the observation of binaries consisting of pre main-sequence stars, supports the theory that binaries are already formed during star formation. Fragmentation of the molecular cloud during the formation of protostars is an acceptable explanation for the formation of a binary or multiple star system.

Thought: Isaac Newton was an alchemist. He was looking for the secret, most especially, of transmuting base elements into gold.

Instead, he discovered the law of gravity.

Which, as expressed in neutron star formation and collisions, is what transmutes base elements into gold.

Score one for the alchemists.

Disclosure: A rare self-post. I'd be very grateful for any and all corrections to the story, as I am far from an expert is astrophysics, geology, or pretty-much anything else.

> At some point, a satellite the size of Mars came crashing into the earth, so hard and so fast that about a third of the earth was blasted into space. It didn’t go far–the debris formed a ring around the earth, and gravity eventually compacted it into a single satellite, our moon, but a satellite much larger than our planet’s gravity would normally be able to capture.

Something seems off about "a third": according to https://en.wikipedia.org/wiki/Moon, the Moon's radius is a bit less than a third of Earth's, but its volume is 2% and its mass is just 1%. I'm no expert, but "about a hundredth" seems more accurate.

For what it's worth, I only looked it up because I've come across this discrepancy before, so perhaps I'm missing something!

I could be wrong about this, but note also that not all of the material ejected from the impact wound up in Earth's orbit.

Small typo: "Neutron stars to not hang, fixed in space"

I'm guessing that it should be "do not"

Probably another typo: "planet our side" -> "planet our size"?

Also, this is a beautiful piece of writing! I love it.


Thank you or sharing your appreciation. I will treasure that.

Another: "May tiny such creatures, when they died"


> I would have found that while my scale tells me that I am about 86 kilograms on Earth, I would have weighed 8.6 trillion kilograms on this neutron star.

Kilograms are a measure of mass, not weight. Pounds would be a more appropriate unit there.

A pound is also a measure of mass [1]. Unless you're thinking of the 'pound-force' which is just the force of gravity applied to one pound-mass. The same definition exists for kilograms (kilogram-force) but is not part of the international unit system. Gravity is slightly different close to the poles etc so a *-force unit will never be precise in this context.

The majority of humanity has absolutely no idea what 'one pound' is when not referring to the currency, and will merrily say they weigh X kilograms.

[1] https://en.m.wikipedia.org/wiki/Pound_(mass)

Honestly, I don't think it is any more correct to use pounds instead of kilograms as a substitute for force, as they are both units of mass. I didn't mind the use of kilogram in your specific context, for what is worth.

My pleasure. Great piece, hope I didn't come off as being a turd or anything.

Most of the people world weigh themselves in kilograms.

They roughly infer their mass (in kilograms) by assuming 9.8m/s/s gravitational acceleration and using a scale to judge how much mass the resulting 'push' would require given that pull. A scale would tell you that you weight slightly less at the top of a mountain than at sea level, though in reality you'd have the same mass. Same is true on a neutron star.

It's an easy shorthand for the most part, since we're not 'weighing' ourselves in space, on the moon, etc, but in an article about space and physics and whatnot, it can come off as a bit sloppy.

Every single thing about life as we know it, humanity, and our brains is exceedingly sloppy. What makes it work? Error correction!

So, thank you.

> A scale would tell you that you weigh[] slightly less at the top of a mountain than at sea level, though in reality you'd have the same mass.

For an illustration of a pedantic distinction, this seems awfully unlikely to be correct. You gain mass by eating and drinking and lose it by urinating, defecating, and breathing; odds are you're not going to have the same mass on the mountaintop.

This is physics, we're clearly assuming a perfectly spherical human with lossless and instantaneous modes of travel.

> pedantic

Think you're maybe projecting? It was meant to be a silly example and taking a super uncharitable interpretation (object x at different times or states with different masses) of my statement just to be able to pick a nit strikes me as more pedantic than responding to a request for corrections with my high school level understanding of basic units.

Because a hike like that will really burn off the pounds ... er, I mean kilograms. (Joke)

9.8 m/s^2 need not be assumed. As long as you have a calibration standard, any scale can be calibrated correctly in any gravitational field.

If you care about absolute masses at the ~percent scale or better, calibration is requisite.

> A scale would tell you that you weight slightly less at the top of a mountain than at sea level, though in reality you'd have the same mass.

A pound of force uses 'standard gravity' as a constant, even though it varies across the earth. Sounds just as bad?

A pound of force is defined [1, 2] as 4.448222 N . No gravity necessary (but the IPK is, until the upcoming redefinition of the SI).

Yes, that definition was reached using a notion of "standard gravity", but once fixed, it is nothing but a number.

[1] https://physics.nist.gov/cuu/pdf/sp811.pdf [2] https://en.wikipedia.org/wiki/Pound_(force)

Still not any more precise than kg to measure human weight (unless you position the human at the exact right spot on earth).

A properly-calibrated scale/balance will correctly determine the mass of any object in any gravitational field (gravity gradients excepted).

Not just as bad, because you'd be measuring the correct thing, which is force. Not mass. That's all I was getting at - they're different things and depending on context, one can change (weight) where the other does not (mass). That's all.

Because they're interested in knowing their mass, not their weight. Weighing is done using scales, which have a hardcoded division by gravitational acceleration of Earth on its... scales.

True, but WaxProlix is correct. Ten kilograms is 22 pounds on Earth, but 2.2 trillion pounds on the given Neutron Star.

I was going to jump in and say that the pound is also a unit of mass. But it turns out its both.

https://en.wikipedia.org/wiki/Pound_(force) https://en.wikipedia.org/wiki/Pound_(mass)

And then there's the foot-pound, a unit of torque much prized by the owners of muscle cars until eclectric vehicles went from obscure to early-adopter status.

Or just general torque in the United States. Electric vehicles still have tires that are joined to wheels which are fastened to an axle by the tightening of a nut on a threaded stud. For safety, we generally state that the nut should have X foot-pounds of torque applied to ensure it doesn't fall off. Unless Tesla et al. have suddenly decided to use a more universal standard in the states, I'd assume they still publish that value in ft/lbs, since 98% of tools designed to measure these things owned in the U.S.A. have this unit on them.

Also, assuming we're talking about rest mass, since without that distinction the word mass is ambiguous in accelerated contexts.

Well, at least you recalled the story toothfully.

Writing is an exercise in literary mastication.

Is that you racing cross on the book cover?

Yes it was, when the stars were younger than today :-)

> Hark to the lesson of this story: Everything has an explanation.

Great writing. But the lesson is wrong. It has been proven that certain things which are true can never have an explanation: Godels incompleteness theorem.


I do not think Incompleteness speaks to the question of whether things that happen in our Universe have explanations. It speaks to formal mathematical systems that have a property of self-reference.

If we are to debate whether the conclusion of my parable is true, I would tend more towards considering the possibility that many things in our Universe may simply be axiomatic, there is no explanation for them, they just are. Uncertainty may be one of those things.

Another line of investigation would be to consider whether some things do have explanations, but we have missed the opportunity to gather the evidence to understand them, therefore we will never understand them. Likewise, the Universe is finite, it will die, and we may never discover all of the explanations.

If something has an explanation, but there is no way for us to discover it, in what sense does it have an explanation?

The incompleteness theorem does not only apply to mathematical systems. It applies to all formal systems in the realm of logic. If we assume that all of reality can be reduced to a formal logical system then the incompleteness theorems apply. Thus even non-axiomatic concepts may be unexplainable.

However, you bring up a good point. Explanations rely on evidence and evidence must be observed. Additionally, the tools which we employ to observe evidence are imperfect. What does this mean?

It means in the world of logic only some things can't be proven, but in the world of science (aka reality as we know it): Nothing can be proven. Nothing can be fully explained because additional evidence can always be observed in a later point in time that disproves an explanation. As Einstein once said:

"The scientific theorist is not to be envied. For Nature, or more precisely experiment, is an inexorable and not very friendly judge of his work. It never says "Yes" to a theory. In the most favorable cases it says "Maybe," and in the great majority of cases simply "No." If an experiment agrees with a theory it means for the latter "Maybe," and if it does not agree it means "No." Probably every theory will someday experience its "No"—most theories, soon after conception."

or Karl Popper who put the concept simply:

"...no matter how many instances of white swans we may have observed, this does not explain the conclusion that all swans are white."

In short, no amount of evidence or explanation can justify any statement.

Interestingly though, it takes only one observed black swan to disprove a statement. Hence the role of falsifiability in the scientific method.

A proper shaggy dog story if I've ever read one! Entertaining and interesting along the way, and the ending snuck up on me.

Thanks for a good read :)

> I might have lifted my Apple Watch and said “Hey Siri, record a note.” If I was using the Apple Neutron Star Edition Apple WatchOS, it would have had to correct for time dilation between time at my waist and time at my shoulder.

Would it, really? Using a back-of-the-envelope calculation using a formula pulled from Wikipedia[1], and assuming:

1. The Apple Watch needs to stay within 50 milliseconds as Apple advertises

2. The neutron star is around two solar masses and has a radius of 10 km, and isn't spinning faster than 1,000 times a second

3. The distance between your waist and shoulder is about a meter

it should take a couple hundred seconds before Apple Watch drifts out of sync. Should be long enough for Siri to record your note :)


> should take a couple hundred seconds before Apple Watch drifts out of sync. Should be long enough for Siri to record your note :)

I wouldn’t be so sure. First of all, siri is pretty slow already in the best of times. Second, the watch doesn’t do the recognition onboard; it sends the audio (or some processed version, I don’t know) to your phone. And a neutron Star, especially a spinning one with lots of junk around it, we be generation an ENORMOUS amount of RF interference. I can definitely see it getting out of sync.

Then again it (and you) are not really rated for neutron sta4 conditions and the tidal forces would definitely tear you apart; just moving your arm would distort the watch, 7nless perhaps you purchased the extra expensive ceramic version.

What a thoroughly enjoyable yarn which took me on a journey from the periodic table, star formation, islands of stability and a good old Wikipedia vortex.

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