For Questions That Don't Merit Their Own Thread

[AckSed]

The MAVEN satellite and Hubble Space Telescope measured Mars' atmosphere and found that the solar wind and sunlight (which varies over the Martian Sol by 40%) provided the last kick needed to strip the water out: https://science.nasa.gov/missions/hubble/nasas-hubble-maven-help-solve-the-mystery-of-mars-escaping-water/

Then I remembered the electrostatic shielding simulations performed by JPL and JSC: https://arstechnica.com/science/2024/03/shields-up-new-ideas-might-make-active-shielding-viable/

tl;dr a set of stacked charged plates arranged in a cube and Sputnik-like charged rods at each corner shape the fields such that 50% of solar charged particles are repelled, but plasmas pass straight through, reducing the charge needed from 60 million volts down to 1 million, and power required for a crew hab down to 100 watts.

Scaling this up to the size of a planet would be a job of work, and would only slow the bleeding, but it's one component of the bandage.

Fake edit: I searched further, and people have suggested that an artificial magnetosphere at Mars-Sol L1 would shield it enough that the temperature might rise anyway once the rate of loss is slowed: https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html

[DDE]

On 12/9/2024 at 4:05 PM, AckSed said:

Theoretically, you could make a chemical explosive inertial-fusion warhead by means of a set of very precisely-placed staged flyer plates backed with explosives, and a capsule of fusion fuel at the end (scroll down): https://www.projectrho.com/public_html/rocket/spacegunconvent.php

Also reviewed by MatterBeam at length (section "Pure Fusion"): 

https://toughsf.blogspot.com/2022/03/fusion-without-fissiles-superbombs-and.html?m=1

[Lisias]

Assuming a Civilization Level III on the Kardashev Scale would like, by reasons beyound our reasoning, transmit a message to the Universe.

It's known that Light have a horizon that limits the reach of such message, not to mention the shift to red due the spacetime expansion. Yeah, I'm talking about the limits from the Observable Universe.

But since Gravitational Waves are not particles traveling in the spacetime, they are the own spacetime compressing and expanding (waves). So such waves would not have the same limitation of Light, that reaches a point in which the spacetime length it's going to travel "stretches" faster than it's own speed.

Gravitational Waves travel on the spacetime itself, so these waves ends up being stretched together the spacetime itself instead of staying behind.

So, the best way to transmit a one way message to the rest of the Universe would be by modulating Gravitational Waves (how they would do it it's out of the scope of this thought experiment - they are a Level III and not us for a reason!).

Would we, primitive beings stumbling each other on the 3rd rock from the local Star, be able to detect such modulation on Gravitational Waves?

[magnemoe]

11 minutes ago, Lisias said:

Assuming a Civilization Level III on the Kardashev Scale would like, by reasons beyound our reasoning, transmit a message to the Universe.

It's known that Light have a horizon that limits the reach of such message, not to mention the shift to red due the spacetime expansion. Yeah, I'm talking about the limits from the Observable Universe.

But since Gravitational Waves are not particles traveling in the spacetime, they are the own spacetime compressing and expanding (waves). So such waves would not have the same limitation of Light, that reaches a point in which the spacetime length it's going to travel "stretches" faster than it's own speed.

Gravitational Waves travel on the spacetime itself, so these waves ends up being stretched together the spacetime itself instead of staying behind.

So, the best way to transmit a one way message to the rest of the Universe would be by modulating Gravitational Waves (how they would do it it's out of the scope of this thought experiment - they are a Level III and not us for a reason!).

Would we, primitive beings stumbling each other on the 3rd rock from the local Star, be able to detect such modulation on Gravitational Waves?

Gravity waves still suffer from the 1/Distance^3 weakening of power, we can receive events who is massive like colliding neutron stars. I'm also pretty sure gravitational waves is affected by expanding of the universe. 
Might even be more affected? 
Gravity waves is also hard to produce at star level strength, while this is trivial with light or radio. 

[Lisias]

1 hour ago, magnemoe said:

Gravity waves still suffer from the 1/Distance^3 weakening of power, we can receive events who is massive like colliding neutron stars. 

So assume that such Level III civilization can modulate neutron stars collisions!

I'm interested about how we would receive such transmission.

 

1 hour ago, magnemoe said:

I'm also pretty sure gravitational waves is affected by expanding of the universe. 

Yes, they are. And yes, I think this is the worse part of the problem.

 

1 hour ago, magnemoe said:

Might even be more affected? 

Nope. Gravitational Waves are not blocked by matter like light. And there's no Horizon other than the Big Bang.

 

1 hour ago, magnemoe said:

Gravity waves is also hard to produce at star level strength, while this is trivial with light or radio. 

Now, being picky, Gravity Waves are a completely different thing.

And there's no doubt that radio and light are infinitely easier to produce, but they are limited to the Observable Universe of the emitter.

Our current Observable Universe have a 44.5B Light Years Radius  and it's shrinking, so the same will be happening/had happened to theirs.

Given the fabulous distances and the uncertainty about the statistics for the existence of intelligent life, if you have almost infinite resources you will want to use the method that would maximize the chances of someone getting the message.

Under this criteria, modulating Gravitational Waves have a infinite better RoI than Light.

Edited Monday at 09:19 AM by Lisias
tyops. as usulla.

[magnemoe]

5 hours ago, Lisias said:

So assume that such Level III civilization can modulate neutron stars collisions!

I'm interested about how we would receive such transmission.

Yes, they are. And yes, I think this is the worse part of the problem.

Nope. Gravitational Waves are not blocked by matter like light. And there's no Horizon other than the Big Bang.

Now, being picky, Gravity Waves are a completely different thing.

And there's no doubt that radio and light are infinitely easier to produce, but they are limited to the Observable Universe of the emitter.

Our current Observable Universe have a 44.5B Light Years Radius  and it's shrinking, so the same will be happening/had happened to theirs.

Given the fabulous distances and the uncertainty about the statistics for the existence of intelligent life, if you have almost infinite resources you will want to use the method that would maximize the chances of someone getting the message.

Under this criteria, modulating Gravitational Waves have a infinite better RoI than Light.

The main problem is that the observable edge of the universe exist because the part outside it moves faster than light relative to us because the universe expands. More accurate relative velocity at the time from the signal was sent to we received it. Gravity waves can not escape this they will also become longer wavelength as the universe it travel trough expands. Same with particles or spaceships but her velocity goes down.  

And it might exist ways to generate large gravity waves easier if you can manipulate gravity and can build huge structures in space. 
And gravity waves are not blocked by much, yes I assume they get distorted by massive objects like light bends but its not blocked. 

But high frequency electromagnetic waves can have very high frequency so they can handle some red shifting. Gravity waves in the MHz range would be hard at high power levels even if you had gravity generators  

[Lisias]

4 hours ago, magnemoe said:

The main problem is that the observable edge of the universe exist because the part outside it moves faster than light relative to us because the universe expands. More accurate relative velocity at the time from the signal was sent to we received it. Gravity waves can not escape this they will also become longer wavelength as the universe it travel trough expands. Same with particles or spaceships but her velocity goes down.

Yes. But, yet, Gravitational Waves doesn't share this limitation!

https://en.wikipedia.org/wiki/Cosmic_microwave_background#Primordial_gravitational_waves

Granted... The way we detected it nowadays is from their effects on the cosmic microwave background...

Just fount this: https://www.phys.ufl.edu/courses/phz6607/fall20/Reports/Farshad_Kamalinejad_Primordial_Gravitational_Waves.pdf

Note to myself: come back to this later (Working hours right now).

 

5 hours ago, magnemoe said:

But high frequency electromagnetic waves can have very high frequency so they can handle some red shifting.

Yep, but they are still trapped on their Observable Universe.

 

5 hours ago, magnemoe said:

Gravity waves in the MHz range would be hard at high power levels even if you had gravity generators  

Their problem, not ours!! They are Level III for a reason!

[Terwin]

40 minutes ago, Lisias said:

Yep, but they are still trapped on their Observable Universe.

I see no reason that gravity waves would not have the same limitation.

Gravity waves do not get to exceed C just because the points they are traveling between are further apart than they were at some point in the past.

They may get to stay at C instead of occasionally getting absorbed and re-emitted like EM waves, but that is the only difference I see between their travel speeds.

Perhaps you can explain how a gravity wave travelling in a straight line can get ahead of a laser traveling parallel to that wave through a perfect vacuum without breaking relativity?

Without this, gravity waves are stuck in the same light cone as EM radiation, and only have greater coverage within that cone because it is much easier to shield a region from light than it is to shield it from gravity.

A light-wave and a gravity wave traveling through 'stretched' space would travel at the same speed unless blocked by other obstacles, and both would get frequency-shifted by the same amount by the expansion of the universe.  Perhaps you could argue that gravity waves of a high enough frequency and amplitude could be detected more easily at a certain distance than light of the same frequency and amplitude, but the light would still be there, just less of it because light is easier to block or re-direct. 

Edited Monday at 09:30 PM by Terwin

[Lisias]

1 hour ago, Terwin said:

I see no reason that gravity waves would not have the same limitation.

Again, Gravitational Waves. Gravity Waves are a completely different thing.

If we are going to dive on this rabbit's role, we need to communicate our ideas correctly.

Light have such limitation because the photons are "walking" on the space time like you would be walking on a side road. If the side road stretches faster that you can run, you will never reach the other end.

But Gravitational Waves are not a "thingy" walking on the spacetime, they are something on the spacetime itself. So if the spacetime stretches faster than light, so they do the same.

There're stellar bodies running away from us beyound the speed of light at this very moment. How they would be doing it otherwise?

 

1 hour ago, Terwin said:

A light-wave and a gravity wave traveling through 'stretched' space would travel at the same speed unless blocked by other obstacles

No. Gravitational Waves don't travel through 'stretched' spacetime. They propagate on it. If the spacetime stretches, they do the same at the exact very rate, unlike Light that ends up with more spacetime to travel through.

You don't block a Gravitation Wave unless by ripping apart the spacetime (like on a blackrole) to prevent the propagation.

Edited Monday at 11:09 PM by Lisias
Gee... Now I'm switching words?

[K^2]

2 hours ago, Lisias said:

Again, Gravitational Waves. Gravity Waves are a completely different thing.

If we are going to dive on this rabbit's role, we need to communicate our ideas correctly.

Light have such limitation because the photons are "walking" on the space time like you would be walking on a side road. If the side road stretches faster that you can run, you will never reach the other end.

But Gravitational Waves are not a "thingy" walking on the spacetime, they are something on the spacetime itself. So if the spacetime stretches faster than light, so they do the same.

No, that doesn't work this way. Gravitational waves obey locality, just like everything else. You can create a space-time in which you can traverse the distance faster, but you have to do so in advance, because the initial change has to propagate through the space-time with the initial speed of light. That's why a gravitational wave, despite being able to modify space-time behind it, can't reach you faster than a light beam would.

Anything that's beyond Cosmological Horizon for light, is also beyond the horizon for gravitational waves. We cannot interact in any way with matter that's beyond that point, which means that whether or not it even exists is entirely academic unless entirely new principles are discovered. Within classical General Relativity, the Cosmological Horizon is absolute.

Edited Tuesday at 12:14 AM by K^2

[Lisias]

1 hour ago, K^2 said:

No, that doesn't work this way. Gravitational waves obey locality, just like everything else. You can create a space-time in which you can traverse the distance faster, but you have to do so in advance, because the initial change has to propagate through the space-time with the initial speed of light. That's why a gravitational wave, despite being able to modify space-time behind it, can't reach you faster than a light beam would.

Anything that's beyond Cosmological Horizon for light, is also beyond the horizon for gravitational waves. We cannot interact in any way with matter that's beyond that point, which means that whether or not it even exists is entirely academic unless entirely new principles are discovered. Within classical General Relativity, the Cosmological Horizon is absolute.

The information I have, and that inspired this Thought Experiment (®1896 Einstein), it that the Primordial Gravitational Waves can be pushed outside the Cosmological Horizon (thanks for the wording, I was struggling to find them!):

Quote

Primordial gravitational waves are amplified during eras when their wavelengths are pushed outside the cosmological horizon. This occurs in both inflationary and ``pre-big-bang'' or ``bounce'' cosmologies.

https://inspirehep.net/literature/503497#:~:text=Primordial gravitational waves are amplified during eras,density per unit logarithmic frequency%2C denoted Omega.

Granted, we are not talking about PGW, but about "artificial" Gravitational Waves modulated by an advanced (but somewhat ego driven) Level III Civilization. They are probably impossible to be created, but heck, for the sake of this Though Experiment, let's assume that given a wondrously advanced Civilization ever existed on this Universe, they would had discovered things that are currently beyound even our imagination, in the same sense that transmitting a video from Mars would be to the Neanderthals that barely were able to rug dirty fingers on a cavern's wall.

Would we be able to detect modulation in Gravitational Waves?

[magnemoe]

4 hours ago, Lisias said:

Their problem, not ours!! They are Level III for a reason!

Its very doable you just need to be pretty causal launching interstellar mission who fit well with an Kardashev 2 civilization. Repeat.
https://tangent128.name/depot/toys/freefall/freefall-flytable.html#2997

Obviously  Kardashev 3 require faster than light to be an thing, even if you argue earth today is one civilization who has some merit. 
You have an light speed delay of up to 50.000 years, and you would use millions of years to colonize. You would be multiple species just by genetic drift. 
Isaac Arthur makes an argument that this is why you don't have interstellar empires you are just creating aliens. 

[Terwin]

1 hour ago, Lisias said:

Light have such limitation because the photons are "walking" on the space time like you would be walking on a side road. If the side road stretches faster that you can run, you will never reach the other end.

But Gravitational Waves are not a "thingy" walking on the spacetime, they are something on the spacetime itself. So if the spacetime stretches faster than light, so they do the same.

light waves also get stretched in the same manner(called red-shift), but as the amount of space between here and there grows faster than what could be covered when traveling at the speed of light, it can never get  here.

 

1 hour ago, Lisias said:

There're stellar bodies running away from us beyound the speed of light at this very moment. How they would be doing it otherwise?

Those stars are not moving compared to the local space, it is just that there is more space being created between here and there than could be covered if you were moving at the speed of light.

 

1 hour ago, Lisias said:

No. Gravitational Waves don't travel through 'stretched' spacetime. They propagate on it. If the spacetime stretches, they do the same at the exact very rate, unlike Light that ends up with more spacetime to travel through.

If there is more space-time, then both gravity and light must travel the same distance and would get 'stretched' the same amount.  Unless gravity waves can travel faster then the local speed of light, they can never 'pass' light that is traveling through a vacuum, and have the same range limit due to the expansion of space-time.

Just because the speed of sound may be higher in a stretched rubber sheet than in a relaxed rubber sheet, does not mean that gravity waves can travel faster than a photon in a vacuum, regardless of how that space is stretched or warped.

[K^2]

1 hour ago, Lisias said:

The information I have, and that inspired this Thought Experiment (®1896 Einstein), it that the Primordial Gravitational Waves can be pushed outside the Cosmological Horizon (thanks for the wording, I was struggling to find them!):

The source of the primordial waves isn't beyond the horizon. It's the early inflation of the universe itself. Meaning, the source is effectively local. The article merely talks about the fact that the observable universe acts as a resonance chamber. It's not allowing any waves or information from beyond the horizon to reach us.

[Lisias]

1 hour ago, K^2 said:

The source of the primordial waves isn't beyond the horizon. It's the early inflation of the universe itself. Meaning, the source is effectively local. The article merely talks about the fact that the observable universe acts as a resonance chamber. It's not allowing any waves or information from beyond the horizon to reach us.

1 hour ago, Terwin said:

If there is more space-time, then both gravity and light must travel the same distance and would get 'stretched' the same amount.  Unless gravity waves can travel faster then the local speed of light, they can never 'pass' light that is traveling through a vacuum, and have the same range limit due to the expansion of space-time.

So... What I should understand from this statement:

Quote

Primordial gravitational waves are amplified during eras when their wavelengths are pushed outside the cosmological horizon.

Source: https://inspirehep.net/literature/503497#:~:text=Primordial gravitational waves are amplified during eras,density per unit logarithmic frequency%2C denoted Omega.

[kerbiloid]

23 hours ago, Lisias said:

So, the best way to transmit a one way message to the rest of the Universe would be by modulating Gravitational Waves (how they would do it it's out of the scope of this thought experiment - they are a Level III and not us for a reason!).

And this is available only for the most developed outstanding civilisation(s), who thus have no counterpart to talk to.

Conclusion: self-development makes you introvert.

P.S.
Also, as the Allmighty Being's will has no limitation in time and space, it omits the physical laws, including the lightspeed limit, lol.

[K^2]

7 hours ago, Lisias said:

So... What I should understand from this statement:

That the spectrum of the background gravitational waves is going to have features corresponding to the change in dominant mode of expansion of the early universe. It's all in the paper. I have no idea why you think this has something to do with propagation of waves from beyond the horizon, seeing how the paper treats the horizon as a boundary.

[Lisias]

20 hours ago, K^2 said:

That the spectrum of the background gravitational waves is going to have features corresponding to the change in dominant mode of expansion of the early universe. It's all in the paper. I have no idea why you think this has something to do with propagation of waves from beyond the horizon, seeing how the paper treats the horizon as a boundary.

I can't understand the equations, but the few plain English parts I could said

Quote

As is well known, primordial gravitational waves may be amplified to detectable levels by parametric
amplification during eras when their wavelengths are pushed outside the cosmological horizon; this can
occur in both inflationary and “pre-big-bang” or “bounce” cosmologies

and

Quote

The logarithmic slope of Ω is simply related
to three properties of the early universe: (i) the gravitons’ mean initial quantum occupation number
N (n) (≡ 1/2 for a vacuum state), where n = aω is the (invariant) conformal frequency of the mode
and a is the cosmological scale factor, and (ii) & (iii) the parameter γ ≡ p/ρ of the cosmological
equation of state during the epoch when the waves left the horizon (γ = γi) and when they reentered
(γ = γf ).

Emphasis are mine. In both sentences, the waves are clearly said to be able to break from the horizon, clearly contradicting what you had said in your post. Granted, apparently they can reenter too - and if instead of "can", the paper somehow says mathematically "they will", then I'm only partially correct on my presumption.

In a way or another, even if such gravitational waves would not be allowed to permanently escape the Cosmological Horizon, at least the English spoken part of the paper says clearly that they can (even if for a "brief" moment), and even if they wold not be allowed to poke the Horizon nowadays naturally, I'm still talking about a Level III Civilization that hypothetically could had find a way to do it artificially -and so modulating Gravitational Waves still would be better than Light and Radio (not to mention Golden Records - I'm looking on you, V'Ger!!!) to send one way messages to the Infinite (and beyound).

In order that I quote myself (again):

On 12/16/2024 at 4:11 AM, Lisias said:

Assuming a Civilization Level III on the Kardashev Scale would like, by reasons beyound our reasoning, transmit a message to the Universe.

It's known that Light have a horizon that limits the reach of such message, not to mention the shift to red due the spacetime expansion. Yeah, I'm talking about the limits from the Observable Universe.

But since Gravitational Waves are not particles traveling in the spacetime, they are the own spacetime compressing and expanding (waves). So such waves would not have the same limitation of Light, that reaches a point in which the spacetime length it's going to travel "stretches" faster than it's own speed.

Gravitational Waves travel on the spacetime itself, so these waves ends up being stretched together the spacetime itself instead of staying behind.

So, the best way to transmit a one way message to the rest of the Universe would be by modulating Gravitational Waves (how they would do it it's out of the scope of this thought experiment - they are a Level III and not us for a reason!).

Would we, primitive beings stumbling each other on the 3rd rock from the local Star, be able to detect such modulation on Gravitational Waves?

 

[K^2]

12 hours ago, Lisias said:

Emphasis are mine. In both sentences, the waves are clearly said to be able to break from the horizon, clearly contradicting what you had said in your post. Granted, apparently they can reenter too - and if instead of "can", the paper somehow says mathematically "they will", then I'm only partially correct on my presumption.

Horizon is modeled as a potential in this paper. It's like if you shine a beam of light into a mirror. Physically, electromagnetic wave induces a change in the electrostatic potential on the metallic coating of the mirror, which influences electric field near it, generating a reflected wave. Mathematically, we describe this as an incident wave entering a mirror and a reflected wave exiting the mirror. Just because that's how the math works out, doesn't mean the beam physically entered some sort of a mirror dimension that happens to have an identical beam shining back out of it into ours. Light simply got reflected without going past the boundary.

It's a bit more complicated here, because the boundary is asymptotic due to the expansion, but the end result is the same. We model it as outgoing waves reaching towards the horizon and inbound waves from it, because infinities are hard, and sometimes you have to do strange things with math to get useful predictions out. The whole paper just talks about the universe being a resonance cavity that's expanding, producing interesting effects in the wave spectrum. And this only works because there is a boundary that nothing can reach us from beyond. If gravitational waves could pass and go freely, there would be no resonance, and no amplification.