For Questions That Don't Merit Their Own Thread

[darthgently]

6 minutes ago, Mr. Kerbin said:

Can a ROCKY PLANET (Earth or less mass) be destroyed by a very close RED GIANT star, via pulse from the star in its Asymptotic Giant Branch , that was like our Sun.

Little pieces as in like Saturn’s moonlets at most.

 

I’m guessing that only tidal or collision forces could do that.  All else would mostly just alter the temperature of the remaining rock after boiling off what could be boiled off and stripping away what gases can be stripped away.

 But, tbh, I have no idea what that pulse entails

[JoeSchmuckatelli]

1 hour ago, Entropian said:

Keep in mind that if you don't gravitationally unbind the planet, the little pieces will simply coagulate back into a single, slowly-cooling object, leaving you back where you began.

@Mr. Kerbin did you miss the above?

FWIW - thermal means heat.  To break up a rocky planet to the degree it's gravitationally unbound would require massive kinetic energy - scattering the remaining pieces around enough so that they cannot collapse back into a planet again. 

So, No?  Thermal pulse isn't going to do it 

[Mr. Kerbin]

1 hour ago, JoeSchmuckatelli said:

@Mr. Kerbin did you miss the above?

FWIW - thermal means heat.  To break up a rocky planet to the degree it's gravitationally unbound would require massive kinetic energy - scattering the remaining pieces around enough so that they cannot collapse back into a planet again. 

So, No?  Thermal pulse isn't going to do it 

Oh.

Yeah I know.

I thought that MAYBE it had enough mass (The stars shed mass this way, remember?) and speed (and heat) to break up an already melting planet.

To quote Wikipedia.

Quote

After enough additional helium accumulates, helium fusion is reignited, leading to a thermal pulse which eventually causes the star to expand and brighten temporarily (the pulse in luminosity is delayed because it takes a number of years for the energy from restarted helium fusion to reach the surface.  Such pulses may last a few hundred years, and are thought to occur periodically every 10,000 to 100,000 years. After the flash, helium fusion continues at an exponentially decaying rate for about 40% of the cycle as the helium shell is consumed. Thermal pulses may cause a star to shed circumstellar shells of gas and dust.

 

[darthgently]

1 hour ago, Mr. Kerbin said:

Oh.

Yeah I know.

I thought that MAYBE it had enough mass (The stars shed mass this way, remember?) and speed (and heat) to break up an already melting planet.

To quote Wikipedia.

 

Well, if the red giant expands big enough it could swallow a planet and between the tidal, collision,  and thermal forces the planet would most definitely be entirely deconstructed eventually

Edited December 28, 2024 by darthgently

[Mr. Kerbin]

17 minutes ago, darthgently said:

Well, if the red giant expands big enough it could swallow a planet and between the tidal, collision,  and thermal forces the planet would most definitely be entirely deconstructed eventually

Okay.

No pretty rings for Calisfinor, I guess. (Close rings)

[Entropian]

4 hours ago, Mr. Kerbin said:

be destroyed by a very close RED GIANT star, via pulse from the star in its Asymptotic Giant Branch , that was like our Sun

AGB evolution is outside my field of study, but I'm pretty sure that with the little data we have about the helium reignition, the luminosity surge would be far from what's necessary to deconstruct the planet.  I do believe that there's evidence for pulsational mass loss in AGBs, perhaps from the reignition, so maybe the ejected mass would ablate away the planet over a long enough time?  Ultimately, granular data on AGB evolution is scarce and the mass loss mechanisms in them is also largely unknown, at least empirically.

[Lisias]

15 hours ago, JoeSchmuckatelli said:

@Mr. Kerbin did you miss the above?

FWIW - thermal means heat.  To break up a rocky planet to the degree it's gravitationally unbound would require massive kinetic energy - scattering the remaining pieces around enough so that they cannot collapse back into a planet again. 

So, No?  Thermal pulse isn't going to do it 

Nope, it's possible - you heat rock enough, it will vapourize. You heat it fast enough, the vapour will create kinetic energy while expanding. You keep the kinectic energy for time enough, it will break the gravity well.

As matter is expelled from the gravity well, the body's gravity will decrease, and easier will be for the remaining vapourize matter to be expelled.

So, yeah. A "thermal pulse" big enough will scatter a planet into space wandering dust.

It only happens that a Red Giant will never reach a point in which such thermal pulse would be remotely possible.

Edited December 28, 2024 by Lisias
Tyops, as usulla...

[K^2]

21 hours ago, Lisias said:

the maths suggests it may be possible in the same way light was seen to exit a medium before entering it

The math says nothing of the sort. The news article you link has this quote from the scientists especially for you:

Quote

Still, Steinberg and Angulo are quick to clarify: no one is claiming time travel is a possibility. "We don't want to say anything traveled backward in time," Steinberg said. "That's a misinterpretation."

The fact that phase velocity can exceed group velocity when traveling through certain media is well known, and there have been similar experiments with excitation being detectable on the far side of the medium before the near side. Both, however, are delayed by more than time required for light to travel from the original activation of the lasing medium. In effect, it's the side closer to the laser that's getting a delayed response due to the weird way the wave propagates through the medium, allowing intensity to build up to a detectable level on the far side before the near side. (You can't have a perfectly instantaneous laser pulse, because physics.)

This is sometimes waved away as quantum weirdness, but really, the effect has been known, at least on paper, in classical electrodynamics for a suitable choice of μ and ε of the medium and a given source spectrum. I don't know if we've had experimental verification until now, and if not, kudos to this particular team. But again, this doesn't involve FTL, which the scientists themselves are fast to point out, precisely because they don't want somebody running away with it like you just did. It's just waves being waves.

 

Your second link is to an article about quasi-particles. Again, it's about an excitation in a medium - in this case, not even a real particle, and yeah, you can make waves in matter do weird stuff. None of it allows a wave to arrive at a destination faster than a beam of light in a vacuum would.

 

I've spent what, 5 or 6 years in grad school basically just doing particle/wave propagation and interaction. I might be rusty, because it's been over a decade, and I might need to look up a reference or derivation here and there, but that's one topic I can talk about confidently. There are topics in cosmology and gravity that I'm very rudimentary in. Like, if you ask me about how the universe expansion is accelerating (which is required for a strict horizon) or something about the observations of background gravitational waves, I only know the barest of basics. Yes, with a little bit more math than most people, but still nowhere near the levels of anyone actually studying these things. But if given an expanding universe, you ask me about how waves propagate through it, be they light, particle, or gravitational waves, that's my domain.

In short, locality is built into the space-time itself and comes down to the fact that no matter how weird the curvature gets, if you zoom in far enough, you'll find a patch of space-time that's basically flat, and that will have a metric where distance is x²+y²+z²-t². It's that final -t² that guarantees that no matter what else is going on, an excitation in a vacuum, be it a force field, a particle field, or curvature of space-time itself, cannot propagate faster than c. And in a universe that expands at an accelerated rate, that means you can pick out two points far enough apart, that signal from one can never reach the other.

If I had to design a prison universe, I cannot think of anything more secure than what we have going on in this one.

[darthgently]

6 hours ago, K^2 said:

The math says nothing of the sort. The news article you link has this quote from the scientists especially for you:

The fact that phase velocity can exceed group velocity when traveling through certain media is well known, and there have been similar experiments with excitation being detectable on the far side of the medium before the near side. Both, however, are delayed by more than time required for light to travel from the original activation of the lasing medium. In effect, it's the side closer to the laser that's getting a delayed response due to the weird way the wave propagates through the medium, allowing intensity to build up to a detectable level on the far side before the near side. (You can't have a perfectly instantaneous laser pulse, because physics.)

This is sometimes waved away as quantum weirdness, but really, the effect has been known, at least on paper, in classical electrodynamics for a suitable choice of μ and ε of the medium and a given source spectrum. I don't know if we've had experimental verification until now, and if not, kudos to this particular team. But again, this doesn't involve FTL, which the scientists themselves are fast to point out, precisely because they don't want somebody running away with it like you just did. It's just waves being waves.

 

Your second link is to an article about quasi-particles. Again, it's about an excitation in a medium - in this case, not even a real particle, and yeah, you can make waves in matter do weird stuff. None of it allows a wave to arrive at a destination faster than a beam of light in a vacuum would.

 

I've spent what, 5 or 6 years in grad school basically just doing particle/wave propagation and interaction. I might be rusty, because it's been over a decade, and I might need to look up a reference or derivation here and there, but that's one topic I can talk about confidently. There are topics in cosmology and gravity that I'm very rudimentary in. Like, if you ask me about how the universe expansion is accelerating (which is required for a strict horizon) or something about the observations of background gravitational waves, I only know the barest of basics. Yes, with a little bit more math than most people, but still nowhere near the levels of anyone actually studying these things. But if given an expanding universe, you ask me about how waves propagate through it, be they light, particle, or gravitational waves, that's my domain.

In short, locality is built into the space-time itself and comes down to the fact that no matter how weird the curvature gets, if you zoom in far enough, you'll find a patch of space-time that's basically flat, and that will have a metric where distance is x²+y²+z²-t². It's that final -t² that guarantees that no matter what else is going on, an excitation in a vacuum, be it a force field, a particle field, or curvature of space-time itself, cannot propagate faster than c. And in a universe that expands at an accelerated rate, that means you can pick out two points far enough apart, that signal from one can never reach the other.

If I had to design a prison universe, I cannot think of anything more secure than what we have going on in this one.

Thank you

[JoeSchmuckatelli]

8 hours ago, Lisias said:

Nope, it's possible - you head rock enough, it will vapourize. You heat it fast enough, the vapour will create kinetic energy while expanding. You keep the kinectic energy for time enough, it will break the gravity well.

I don't dispute this - but the difference between the kinectic energy needed to break up a planet vs the thermal energy needed to vapourize it makes it seem unlikely.  Theia smacked into us and we got a moon out of the exchange. 

Generating the thermal energy required to replicate that event on a point target like a planet (given that you cannot actually aim a star) would probably reduce the star to a gas cloud again. 

[Entropian]

23 hours ago, JoeSchmuckatelli said:

Generating the thermal energy required to replicate that event on a point target like a planet (given that you cannot actually aim a star) would probably reduce the star to a gas cloud again.

Keep in mind that if you pull energy out of a star's core, it will just shrink until hydrostatic equilibrium is reachieved.  If you somehow reduce it to a gas cloud, I'm pretty sure that the mass and density would put it above the Jeans mass, which means that it would just re-collapse into a star.  The time it would take to collapse is definitely a lot longer than a human timescale, but is still very short in the grand scheme of things (Kelvin-Helmholtz timescale).

[JoeSchmuckatelli]

27 minutes ago, Entropian said:

reduce it to a gas cloud

"Reduce" was probably the wrong word; I envisioned the star having to go SN to pulse out enough therms to vaporize the planet.

All the things said above - Roche limit, kinetic strike (whether another planetary body or a significant portion of stellar mass during SN, etc) are much more likely to break up the planet than vaporization through thermal means alone.

I mean - this planet has conditions so hot it vaporizes iron... and remains a planet:

A Planet Hot Enough To Vaporize Iron Looks To Be Even Hotter

 

[SunlitZelkova]

Is there like a master list of possible (or proposed) applications for Earth satellites somewhere?

There’s all this talk about a space economy in the near future as Starship allows for satellites to come down in cost, but I’m interested in what types of businesses are expected to profit from this.

New competitors in existing applications, or is it expected new businesses will arise out of this?

[StrandedonEarth]

3 hours ago, SunlitZelkova said:

Is there like a master list of possible (or proposed) applications for Earth satellites somewhere?

There’s all this talk about a space economy in the near future as Starship allows for satellites to come down in cost, but I’m interested in what types of businesses are expected to profit from this.

New competitors in existing applications, or is it expected new businesses will arise out of this?

I’m hoping someone will take advantage to launch fleets of asteroid prospectors (could double as locator beacons) while figuring out how to mine and hopefully refine  asteroidal regolith. And then get the product to somewhere useful. Of course, it would help if the target had some volatiles for propellant as I’m not keen on filling space with streams of rubble from mass drivers…

[AckSed]

No master list for everything. This gives a fair approximation: https://www.factoriesinspace.com/

Spoiler

We may have some rather mad ideas tried, and most will fail. No-one in the industry saw Starlink's breadth and scale succeeding, though OneWeb was first, and Iridium and Echostar satellite telephones were before that.

Any in-space manufactory that orbits the Earth is a potential application. There are lots of things that are difficult or downright impossible inside a gravity well, that are easier in orbit: crystallisation is the big one, as that's the final stage behind forging, semiconductors, pharmaceuticals and more. In microgravity it's more controlled and even. You can also magnetically or electrostatically suspend materials without touching the walls of the crucible, while heating it in freely-available vacuum - a further advantage for semiconductor manufacturing. Then you can take your boule and go home.

Cargo storage in, and delivery from, orbit is an application I couldn't quite believe, but the USA's Space Force is throwing money around to make this Helldivers mechanic happen IRL.

Cheap mass to orbit may be the dawn of Big Dumb Flat-pack Satellites, and K2 Space are hopefully building the bus for your application.

Cheap kick-stages and on-orbit delivery vehicles to higher orbits will eventually lead to true space-tugs, that shift satellites around, reboost and/or refuel from depots. This may also lead to high-impulse rocket engines.

What else...

The classic wishlist of any astronomer - larger telescopes. However, someone will have to stick their neck out and volunteer to sell a mass-produced version. Cheaper cube-sat versions are being proposed, but some entrepreneur with more gumption than brains could break into this (small?) market.

Asteroid mining will have to be after higher-impulse engines, or cheaper space-tugs, or both.

[darthgently]

3 hours ago, SunlitZelkova said:

Is there like a master list of possible (or proposed) applications for Earth satellites somewhere?

There’s all this talk about a space economy in the near future as Starship allows for satellites to come down in cost, but I’m interested in what types of businesses are expected to profit from this.

New competitors in existing applications, or is it expected new businesses will arise out of this?

Probably, and sadly, the big obvious killer app for a small launch would truly be debris deorbiting.  After that I’m as curious as you.  I’m sure militaries around the world have lots of ideas.

Rapid constellation deployment of basic sat based comms and imaging and GPS after an altercation or big solar flare probably has a value for govs wanting to be able to recover quickly.

Lastly, maybe power generation?

When I think orbital economy I mostly imagine larger propellant depots, tourism stations, and manufacturing stations not sats

As for debris, would be cool if every constellation Sat has a bit of extra props aboard such that it could deorbit the old sat it is replacing if it is unresponsive

[DDE]

On 1/3/2025 at 4:49 AM, AckSed said:

Cargo storage in, and delivery from, orbit is an application I couldn't quite believe, but the USA's Space Force is throwing money around to make this Helldivers mechanic happen IRL.

...when instead, it already takes shape of a COTS quadcopter lobbing a bottle of water and a pack of smokes to a lone stormtrooper in some shell crater.

Complete with at least one reported case of an air-to-air kill with a water bottle.

[K^2]

23 minutes ago, DDE said:

Complete with at least one reported case of an air-to-air kill with a water bottle.

I don't know about water bottles, but use of literal sticks tied to a drone is well documented. Einstein was off by one in the most horrifying way imaginable.

Any military still trying to figure out the most efficient way to deliver troops to the contact line is investing resources into falling further behind. The future is clearly unmanned. Delivering the equipment, though, that's still going to be relevant.

[Lisias]

2 hours ago, K^2 said:

The future is clearly unmanned. Delivering the equipment, though, that's still going to be relevant.

You don't occupy territories without... Occupying it.

Wars will never be unmanned, someone must be there so the enemy sign their rendition.

Airforce and Mechanized Infantry will be eventually unmanned, part of the Navy too. But there will be always Infantry - Hooah!

[K^2]

5 hours ago, Lisias said:

You don't occupy territories without... Occupying it.

I don't know if you've seen any footage from the ongoing, but the cities don't get occupied. They get leveled.

Yes, once you firmly establish territorial control, you need to bring in supplies, establish new infrastructure, possibly rebuild and repopulate in time. But at the point of actual contact? It's a meat grinder, and there is zero reason to send in humans when unmanned means of destruction are clearly doing a better job at everything from scouting, to laying mines, to clearing trenches and buildings.

I'm not saying equipment like APCs is becoming obsolete in this kind of warfare. You still need evacuation transport for when the battle lines shift quickly or general transport along threatened routes. But the current use as an infantry delivery vehicle? That's just a waste of resources now - both human and materiel.

[Lisias]

58 minutes ago, K^2 said:

I don't know if you've seen any footage from the ongoing, but the cities don't get occupied. They get leveled.

Cities are just collateral damage if what you want is the control over the land. We have two major conflicts right now (Middle East and European East) clearly demonstrating it at the present time.

There's money on rebuilding cities, anyway, someone need to pay for the expenses...

It's about money. It's always about money...

 

58 minutes ago, K^2 said:

<...>That's just a waste of resources now - both human and materiel.

Or a cheap way to get rid of excessive/surplus stock.

War is hell, dude. Really, really hell.

Edited 1 hour ago by Lisias
Hit "Save" too soon