For Questions That Don't Merit Their Own Thread

[K^2]

2 hours ago, JoeSchmuckatelli said:

what are the possibilities of bombardment periods or 'Dinosaur Killer' asteroids being caused by the sun (and hence the planets) passing through a 'star forming region' or heavy 'dust' cloud during its orbit of the galactic center?

It seems like we ought to be able to tell if a bunch of asteroids suddenly came from outside Solar System during some specific time period in the past. We have found some debris that came from long-ago impacts. I don't know if any go quite that far into the past, though. So maybe there really is nothing for us to analyze. But if we have some rocks that we can identify with specific impact events as likely being from that impactor, we ought to be able to analyze their composition which should tell us where they came from. It's not an exact science, as you can find odd rocks with odd things in them, but if you get a large enough sample, there are patterns. Sol formed from a remnant of a supernova which seeded the system with heavy metals. Relative concentrations of all the things the asteroids and comets are made out of, while varying greatly across the system, taken together form a sort of signature of origin of our Sol. It would be highly unlikely that, given a large enough sample, we would not be able to establish if a bunch of asteroids originated outside Sol.

That said, I don't know if we have a large enough sample size or if anyone tried to look for these particular anomalies.

[kerbiloid]

The passing through a star forming region would probably sterilize the planet.

[magnemoe]

5 hours ago, JoeSchmuckatelli said:

Seeing as meteor showers are often caused by (or attributed to) the earth passing through comet trails... what are the possibilities of bombardment periods or 'Dinosaur Killer' asteroids being caused by the sun (and hence the planets) passing through a 'star forming region' or heavy 'dust' cloud during its orbit of the galactic center?

 

(I know that the presumption is that 'bombardment' periods were only during the remnants of the planet forming period of the vestiges of the dust cloud that formed the sun and planets... but isn't there a possibility of us being dragged through a heavy dust cloud left over from another star forming region as the sun orbits?)

Think its more likely that comet showers are caused by stars passing close, over geological timescales its pretty common for stars to get within one light year of the sun, the comets will however use over an million year before they get into the inner solar system 

[JoeSchmuckatelli]

6 hours ago, K^2 said:

It seems like we ought to be able to tell if a bunch of asteroids suddenly came from outside Solar System during some specific time period in the past. We have found some debris that came from long-ago impacts. I don't know if any go quite that far into the past, though. So maybe there really is nothing for us to analyze. But if we have some rocks that we can identify with specific impact events as likely being from that impactor, we ought to be able to analyze their composition which should tell us where they came from. It's not an exact science, as you can find odd rocks with odd things in them, but if you get a large enough sample, there are patterns. Sol formed from a remnant of a supernova which seeded the system with heavy metals. Relative concentrations of all the things the asteroids and comets are made out of, while varying greatly across the system, taken together form a sort of signature of origin of our Sol. It would be highly unlikely that, given a large enough sample, we would not be able to establish if a bunch of asteroids originated outside Sol.

That said, I don't know if we have a large enough sample size or if anyone tried to look for these particular anomalies.

 

4 hours ago, kerbiloid said:

The passing through a star forming region would probably sterilize the planet.

 

4 hours ago, magnemoe said:

Think its more likely that comet showers are caused by stars passing close, over geological timescales its pretty common for stars to get within one light year of the sun, the comets will however use over an million year before they get into the inner solar system 

All excellent answers - and all in line with the prevailing wisdom. I won't quibble - nah, I'm going to anyway because it's fun! 

I recently read this article https://www.scientificamerican.com/article/a-new-map-of-the-milky-way/

...where the authors point out that our sun lies in a 212 million year orbit of the galactic center, and that the last time the Earth and Sun were in this part of the orbit, dinosaurs roamed the land. 

Like magnemoe wrote, I've often read speculation about passing stars as potential sources of disturbed KB or Oort cloud bodies that become comets or asteroids. But I wonder if we really would see significantly different chemistry in a ʻOumuamua- like visitor to be able to distinguish between it and a local impactor. 

My understanding is that a SN created the dust cloud from which the Sun, planets etc formed. I think we can presume that, aside from some local clumping, the star forming region enjoyed a grossly uniform distribution of chemistry.  After some shock, the heavier elements and rocks clumped together into protoplanets and the proto star. All planets likely have heavy metal cores - but when the Sun lit off and started producing a wind, the lighter parts of the cloud (gasses, etc) were pushed out, allowing the gas giants to collect far more of the lighter elements - and because of this adjustment in the distribution of the 'stuff' in the stellar/planetary nursery we can chemically distinguish between an asteroid belt object and a KBO.   - - But if this process is correct, must we assume that bodies like ʻOumuamua would be sufficiently distinct to know from an impact that it was extrastellar?  Is it possible that all we could say is that it came from a region around a star that was more metal rich or ice rich, and possibly attribute a foreign KBO type impactor with a domestic KBO? 

I'll agree with kerbiloid that passing directly through another stellar nursery would be a disaster - but just as comet trails have rocks and dust trails at enormous distance from the comet that create our annual meteor showers - I wonder if during the 212 million years of orbit if the sun can drag us through 'regularly scheduled' clouds of junk. 

I think the answer to this isn't likely to be known, given that with the timescales involved terrestrial craters weather and slide under tectonic plates. But I read another article (can't find it) that suggests that we've been seeing a multi-million year 'dip' in the number of impactors as determined by the estimated ages Lunar and Martian craters... And if that is the case - then could it not be that if we are in a 'clean' region of the sun's orbit, that we might again at some point be in a 'dirty' region that causes more impactors? 

 

{this assumes that the authors of the paper I read that suggests the 'dip' in the frequency of impacts is correct.  I'll try to find it.  Note: they did not suggest what I've suggested here.  AFAIK they are presuming the impactors are 'domestic'} 

[kerbiloid]

37 minutes ago, JoeSchmuckatelli said:

My understanding is that a SN created the dust cloud from which the Sun, planets etc formed. I think we can presume that, aside from some local clumping, the star forming region enjoyed a grossly uniform distribution of chemistry. 

Afair, there were three close SN, in a star cluster.
The largest one (of the 2nd star generation, already rich with metals and giving them to us) had created the gas cloud of several tens sun masses, and two more had enriched it with specific isotopes not usual for such protostar, and also their shockwaves made the cloud to separate and start condensing.
So, probably the Solar System has syblings, but who knows where.

Also afair, there are two main versions about what happened next.
One hypothesis tells that the Solar System periodically passes through the galactic arms.
Another one that it's drifting in the gap between two major arms, from one of them to another one.
As the Solar System galactic orbit is placed in the galactic corotation zone, so its angular orbital velocity matches the angular velocity of the arms, looks like it's currently rotating between two blades of a fan, and we can only guess what happens if one of them hits.

[JoeSchmuckatelli]

Side note - in case you missed it; this is cool 

Black hole seen eating a star - https://www.google.com/amp/s/www.space.com/amp/black-hole-star-death-spaghettification

The authors' paper is linked at the end of the article 

 

Edited October 14, 2020 by JoeSchmuckatelli

[magnemoe]

1 hour ago, kerbiloid said:

Afair, there were three close SN, in a star cluster.
The largest one (of the 2nd star generation, already rich with metals and giving them to us) had created the gas cloud of several tens sun masses, and two more had enriched it with specific isotopes not usual for such protostar, and also their shockwaves made the cloud to separate and start condensing.
So, probably the Solar System has syblings, but who knows where.

Also afair, there are two main versions about what happened next.
One hypothesis tells that the Solar System periodically passes through the galactic arms.
Another one that it's drifting in the gap between two major arms, from one of them to another one.
As the Solar System galactic orbit is placed in the galactic corotation zone, so its angular orbital velocity matches the angular velocity of the arms, looks like it's currently rotating between two blades of a fan, and we can only guess what happens if one of them hits.

As in the blender or the solution to the Fermi paradox.

On the other hand if you have an dyson swarm it will not be much more expensive than the regression because of the current pandemic to block it. 
10% of the suns output is plenty of energy. 

[JoeSchmuckatelli]

Absurdism?  

 

 

 

(or am I missing something; inside joke?) 

[StrandedonEarth]

3 hours ago, JoeSchmuckatelli said:

My understanding is that a SN created the dust cloud from which the Sun, planets etc formed.

My understanding is that the Sun formed as part of a cluster of stars (seeded by a SN) and was slung out due to gravitational interactions. Otherwise a solitary yellow star is unusual. 

I would be surprised if there were not occasional passing stellar masses slinging KBOs and other detritus inwards. 

[Mitchz95]

If planet X got captured by planet Y, and got stuck in its L2 Lagrangian point for however long, would it be considered a moon of Y or still just a planet?

[JoeSchmuckatelli]

1 hour ago, Mitchz95 said:

If planet X got captured by planet Y, and got stuck in its L2 Lagrangian point for however long, would it be considered a moon of Y or still just a planet?

It would not be a moon - because L2 is a solar orbit - not a planetary orbit (as I read the question posed) 

 

Took me a while to get this through my thick skull.  Because planets clear their orbits, there are very few places in a given planet's orbit that anything can be relatively stable in co-orbiting the sun.  The Lagrange points are these - but for planet X to reside for any time in one it must be significantly smaller than Y

 

Thus when they eventually launch Webb, and presuming successful insertion - it won't orbit Earth like Hubble - it will orbit the sun with Earth. 

Edited October 14, 2020 by JoeSchmuckatelli

[Mitchz95]

4 hours ago, JoeSchmuckatelli said:

It would not be a moon - because L2 is a solar orbit - not a planetary orbit (as I read the question posed) 

 

Took me a while to get this through my thick skull.  Because planets clear their orbits, there are very few places in a given planet's orbit that anything can be relatively stable in co-orbiting the sun.  The Lagrange points are these - but for planet X to reside for any time in one it must be significantly smaller than Y

 

Thus when they eventually launch Webb, and presuming successful insertion - it won't orbit Earth like Hubble - it will orbit the sun with Earth. 

That makes sense, thank you!

[ARS]

Taking account of heavier mass and payload, but at higher speed and engine power, does modern carrier-based aircraft need longer or shorter runway on carrier's flight deck for takeoff and landing compared to WW2-era carrier-based aircraft?

Edited October 15, 2020 by ARS

[magnemoe]

43 minutes ago, ARS said:

Taking account of heavier mass and payload, but at higher speed and engine power, does modern carrier-based aircraft need longer or shorter runway on carrier's flight deck for takeoff and landing compared to WW2-era carrier-based aircraft?

Generally longer as in jet planes need catapults who was not common during WW2, landing is also different, think they started using tail hooks but they did not have angled flight decks.
Exception is planes like harrier and other VTOL planes, even they often use runway for takeoff as they can then be heavier. 

[SOXBLOX]

2 hours ago, ARS said:

Taking account of heavier mass and payload, but at higher speed and engine power, do modern carrier-based aircraft need longer or shorter runways on a carrier's flight deck for takeoff and landing compared to WW2-era carrier-based aircraft?

Generally irrelevant. Modern carriers have high-power catapults and high-strength arresting wires.

STOVL craft are generally also VTOL capable, but they use the "ski-jump" ramp to take off when fully loaded. A good example at sea now is the HMS Queen Elizabeth.

So, modern jets use a bit more deck, but they have much larger payloads. Modern fighters can carry more than WWII bombers.

[JoeSchmuckatelli]

4 hours ago, ARS said:

Taking account of heavier mass and payload, but at higher speed and engine power, does modern carrier-based aircraft need longer or shorter runway on carrier's flight deck for takeoff and landing compared to WW2-era carrier-based aircraft?

 

54 minutes ago, SOXBLOX said:

Generally irrelevant. Modern carriers have high-power catapults and high-strength arresting wires.

STOVL craft are generally also VTOL capable, but they use the "ski-jump" ramp to take off when fully loaded. A good example at sea now is the HMS Queen Elizabeth.

So, modern jets use a bit more deck, but they have much larger payloads. Modern fighters can carry more than WWII bombers.

IIRC - WWII aircraft were launched (with the ship full steam into the wind) under their own power back in the day.  AFAIK, no modern military fixed wing (other than VTOL) can do that.  Hence the catapults and wires.  Carrier aircraft these days also have to be specifically designed for the stresses of regular launch by catapult and landing by tripwire, which makes for a pretty tough aircraft. 

Something that often strikes me is the difference between modern US carriers and other nations' "flattops".  US carriers have longer, angled and flat flight decks, while some (RU, CN et.al.) have in line decks with 'ramps' at the end. I suspect this is because they're shorter boats, but catapult tech could be an issue as well. Clearly they need some additional oomph (the ramp) to get the planes airborne and kept dry after launch - and while I don't know for sure, I suspect US carrier planes can be heavier at launch (with all that implies about strength, avionics and payload) than competitors. 

Perhaps @mikegarrisonknows - does building a carrier aircraft require adjustment to the wing shapes and dimensions compared to similar land based craft? 

[SOXBLOX]

20 minutes ago, JoeSchmuckatelli said:

I suspect this is because they're shorter [ships, how dare you call these "boats"!], but catapult tech could be an issue as well.

Yes, and what catapult tech? Besides the USN carriers, only the Charles de Gaulle has catapults, and they're American-designed. The ramps allow VTOL aircraft to take off with heavier loads, by getting a running start to pick up lift. Alternatively, they give modified non-VTOL land fighters *cough* Su-33 *cough* a chance to make it into the air before plummeting into the sea like a rock. I say modified, because they need more lift to avoid stalling at the low speeds they get off the ramp. Moar wings!

20 minutes ago, JoeSchmuckatelli said:

CN

Oh, you mean the People's Liberation Army Navy? What a name for a naval force!  Is their naval air wing called the "People's Liberation Army Navy Air Force"?

 

Edited October 15, 2020 by SOXBLOX

[JoeSchmuckatelli]

1 hour ago, SOXBLOX said:

Yes, and what catapult tech? Besides the USN carriers, only the Charles de Gaulle has catapults, and they're American-designed. The ramps allow VTOL aircraft to take off with heavier loads, by getting a running start to pick up lift. Alternatively, they give modified non-VTOL land fighters *cough* Su-33 *cough* a chance to make it into the air before plummeting into the sea like a rock. I say modified, because they need more lift to avoid stalling at the low speeds they get off the ramp. Moar wings!

Oh, you mean the People's Liberation Army Navy? What a name for a naval force!  Is their naval air wing called the "People's Liberation Army Navy Air Force"?

 

LOL! 

Derogatory term used intentionally by a Marine who spent plenty of time on US Navy ships.  

;D

 

And that said - I wasn't aware that the other flattops did not have catapults.  Thanks for that tidbit. Those pilots must be insane. 

[JoeSchmuckatelli]

"Playable" 3D Model of the Galaxy? 

 

A lot of years ago (when Plait's Bad Astronomy was new) I stumbled upon a 'playable', 3d mapped representation of the Galaxy.  You could scroll out from the Sun, see the planetary orbits and keep scrolling to see where the sun was relative to local stars.  You could also zoom to a star and look back towards the sun to see what the sky would look like from that angle (or look at everything else for that matter).  It was cool to see how a "simple" 40ly jump would eliminate or warp the constellations.  In other words - a really cool app, that I think was web based, and gave users an easy, relatable way to picture where we are and what is in the neighborhood. 

Fast forward to today - and with Gaia's sky survey and numerous more recent studies trying to pinpoint the distance and location of stars... I'm wondering if something similar to what I enjoyed back then exists? 

Ideas? 

[Shpaget]

Not really a question, but here it goes anyway. You guys know about the Red Dwarf uncrop CSI shenanigans?

Well, it's happening for real. That's some real wizardry.

 

 

[ARS]

Does human body has a capabilty to dodge bullets like in The Matrix? I'm not saying about could humans do it, but does a human body has a capacity to do so (Based on how human sensory perception, reflex speed and capabilities), assuming the shootout takes place in pistol range like in the movie

[Entropian]

Not at all.  Muscle tissue only reacts and extends so fast.  Maybe it could dodge by luck, but it's really just trading one random chance of being hit for another.

[Spacescifi]

26 minutes ago, ARS said:

Does human body has a capabilty to dodge bullets like in The Matrix? I'm not saying about could humans do it, but does a human body has a capacity to do so (Based on how human sensory perception, reflex speed and capabilities), assuming the shootout takes place in pistol range like in the movie

 

Hahaha.

It does not matter... size/weight matterss

Notice that tiny insects can sustain 100's of g's and survive.

Larger stuff cannot

[magnemoe]

12 minutes ago, Entropian said:

Not at all.  Muscle tissue only reacts and extends so fast.  Maybe it could dodge by luck, but it's really just trading one random chance of being hit for another.

True, now not running in an straight line make sense if you are shot at but that is to make it harder to aim at you. 
In the matrix they simply slowed down the time for the heroes to less than an 1/100 of normal speed. 
I would done that before the shooting started, safer but less fun to watch  

[monophonic]

On 10/15/2020 at 4:26 PM, SOXBLOX said:

Oh, you mean the People's Liberation Army Navy? What a name for a naval force!  Is their naval air wing called the "People's Liberation Army Navy Air Force"?

Yes. Yes it really is called that. Well, very close anyway.

https://en.wikipedia.org/wiki/People's_Liberation_Army_Naval_Air_Force