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06 Dec 2018 20:07

A-L-E-X wrote:
Source of the post about as habitable as a gas giant in that temp range?

I sort of meant a distinction between HUMAN habitability and that of exo-life. Often people confuse the two - generally in science media "Habitable" means habitable for us, homo sapiens sapiens, at our current biological form. Little thought is given to a given habitability of an environment for say, future transhumanists, or extraterrestrial life unless that is specifically the topic in mind (which it always is for the latter case, even in wildly unlikely scenarios: a recent example would be exoplanet Proxima Cen. b).

Anyway, for humans, anywhere could be habitable with enough technological support - from Venus to Pluto. Pretty much any planetary environment is game if their is incentive for us. Certainly gas-giants of any type could support colonies on their moons, orbiting their bulk or even floating in their upper clouds - supported by lighter gasses like zeplins or strung by orbital support anchors and hanging down into the clouds. As per usual, I would suggest checking out Isaac Arthur's Outward Bound series on colonizing planets - specifically his Neptune and Jupiter videos.

Watsisname wrote:
Source of the post To turn it into something like SE or Starry Night that show what things look like in the sky is not possible -- it would require simulating the interactions of millions or billions of particles, as in the Millenium Simulations, and that would require a supercomputer.  


Soooo... in a few years or so? :P Actually, this is serious question: when might computers be powerful enough to model this 'in-game'?.
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06 Dec 2018 23:00

By pumping all our greenhouse gasses into the atmosphere, are we also simultaneously increasing the air pressure?
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06 Dec 2018 23:31

Understandable Wat.  You do some GREAT work!  Your simulations made me think of something else.  We talk all the time about predictions for the future, whether here in theoretical physics, or meteorology or whatever.  Do you think if humanity survives to see the far distant future we'll be able to alter space-time ourselves and change the fate of the universe if it's something undesirable to us (the alternative would be to create a different universe and enter it.)  Kardashev Level IV I believe is the level Sagan had mentioned that humanity or some other species would need to reach to make this possible.  Obviously it's going to require some enormous leaps in energy acquisition and probably science we have no idea about right now, but I thought it's pretty intriguing if one day we or some other species could tweak the future of our universe or create another to escape it if we were close to heat death or the big rip or whatever else.

Inspiration for this comes from Asimov's The Last Question.  I'm sure you've heard of it but if not, it's available for free online.

https://medium.com/@tworitdash/answer-t ... d868dbc967

that contains an interpretation of it

http://www.multivax.com/last_question.html

the story
 
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06 Dec 2018 23:34

Stellarator wrote:
A-L-E-X wrote:
Source of the post about as habitable as a gas giant in that temp range?

I sort of meant a distinction between HUMAN habitability and that of exo-life. Often people confuse the two - generally in science media "Habitable" means habitable for us, homo sapiens sapiens, at our current biological form. Little thought is given to a given habitability of an environment for say, future transhumanists, or extraterrestrial life unless that is specifically the topic in mind (which it always is for the latter case, even in wildly unlikely scenarios: a recent example would be exoplanet Proxima Cen. b).

Anyway, for humans, anywhere could be habitable with enough technological support - from Venus to Pluto. Pretty much any planetary environment is game if their is incentive for us. Certainly gas-giants of any type could support colonies on their moons, orbiting their bulk or even floating in their upper clouds - supported by lighter gasses like zeplins or strung by orbital support anchors and hanging down into the clouds. As per usual, I would suggest checking out Isaac Arthur's Outward Bound series on colonizing planets - specifically his Neptune and Jupiter videos.

Watsisname wrote:
Source of the post To turn it into something like SE or Starry Night that show what things look like in the sky is not possible -- it would require simulating the interactions of millions or billions of particles, as in the Millenium Simulations, and that would require a supercomputer.  


Soooo... in a few years or so? :P Actually, this is serious question: when might computers be powerful enough to model this 'in-game'?.

lol read that short story I just posted, you will get an answer you did not expect!
I didn't know you asked this question before I posted that haha

As for the habitability of brown dwarfs, I also believe that exotic life could exist just about anywhere- even interstellar space (like Fred Hoyle's intelligent space dust.)
 
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06 Dec 2018 23:37

Watsisname wrote:
Snoopmatt wrote:
Source of the post Thu Dec 06, 2018 2:37 pm

Hey everyone I came across this fairly recent paper:  "A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified ΛCDM framework"


I was thinking of making a post to discuss this paper.  In brief, the paper re-interprets dark matter and dark energy as a single substance with a constant and negative mass density.  In other words, it proposes there is no dark matter, but instead there is a negative matter that is being continuously generated.  So it is like Lambda-CDM cosmology, except changing the matter density to be equal to the baryon density, and changing the value and sign of the dark energy while keeping its equation of state the same at w=-1.

Proposing that there is negative matter being constantly created is a pretty crazy idea, but perhaps no more crazy than proposing additional invisible matter and dark energy were to begin with.  So the motivation itself isn't bad and I think is actually a rather interesting approach.  But does it agree with observations?

I don't think that it does.  It actually makes a lot of incorrect predictions that must then be explained away, which is what the author spends a big portion of the paper doing by either vigorous handwaving or re-interpreting observations.  I didn't find this very compelling.

  • By making the total density of the universe less than the critical density, this model predicts a negative curvature, which contradicts observations showing the universe is very close to flat.  So the author argues the curvature must be very small.  This is problematic for the amount of negative matter needed, plus the removing of the positive-mass dark energy from Lambda-CDM.  The curvature should be very negative in this model, clearly observably so.
  • By adding negative mass with equation of state w=-1, it predicts decelerating expansion.  What we observe is accelerating expansion.  So we have to re-interpret the high redshift supernova observations.
  • It changes the age of the universe!  The more negative matter the model needs, the younger the universe must be, for the same current observed expansion rate.  With too much negative matter, this runs into problems with the measured ages of the oldest globular clusters.
  • It predicts a different age-redshift relation.  The CMB and the first galaxies in this model must have formed much later, for the same observed redshifts.  So we would have to completely re-work our understanding of the early universe.  The paper did not attempt to do this.

I also could not find in the paper a clear, consistent choice of values for the cosmological parameters necessary for the model to work.  It requires very little negative matter to be consistent with the age of the universe and the curvature.  But at the same time, it does need a lot of negative matter to explain the galactic rotation curves.

Probably the simplest and most severe problem?  It doesn't predict the observation of the separation of dark matter from regular matter in the collision of the Bullet Cluster.  This is a natural prediction of proposing the existence of additional weakly-interacting positive matter within galaxies and clusters.  But if we instead remove that and replace it with negative matter, then no matter where the negative matter is located, we would not reproduce this observation.


In summary, I see a lot of outstanding issues with this model.  If I had been reviewing the paper for submission I would have suggested putting a clear explanation of the cosmological parameters used, either overall or in each analysis.  This would have made it much easier for other cosmologists to review and check their work.  I think an explanation of the Bullet Cluster in the context of this cosmology was also crucial. 

For future work, the model should be applied to predict the full CMB angular power spectrum (especially for the relative heights of the acoustic peaks, which are an evidence of dark matter!), and the implications for the early evolution of the universe.  A more thorough statistical analysis of the formation of structure would also make it more compelling.  Just because the model makes something that "looks like" the cosmic web doesn't mean much.  In Lambda-CDM cosmology the precise way the structure appears at different scales and redshifts is incredibly well studied.

Wat, that would be exotic matter, and if that was found to exist even in minute quantities or ever made in a collider, it would open up a lot of fantastic new possibilities.  I've always wondered why negative mass matter doesn't exist.  Maybe it does but we cannot detect it (or it could be it exists for so little a period of time like virtual particles that we dont have time to detect it.)
 
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07 Dec 2018 01:36

Stellarator wrote:
Source of the post Actually, this is serious question: when might computers be powerful enough to model this 'in-game'?.

For context, the Millenium II simulation in 2009 contained a little over 1010 particles.  1010 particles means about 1020 interactions to compute per time step.  The simulation was run for 22,000 time steps.  It took 1.4 million computer hours on 2048 cores, or in other words about a month on a world-class supercomputer.  

If we make the generous assumption that the Moore's Law for the number of computations per second per consumer dollar continues to hold for the future, then when would we expect a computer in typical consumer price range to be able to do something like that in a few seconds or minutes?  Maybe in another 20 years.  But again this assumes that trend continues, that we don't hit a ceiling in terms of transistor density on a chip, or the ability to dissipate the heat away when it has to be doing that many computations that quickly in a confined space...

So, short answer for when you can expect this to be possible?  Don't hold your breath. :P

PlutonianEmpire wrote:
Source of the post By pumping all our greenhouse gasses into the atmosphere, are we also simultaneously increasing the air pressure?

Yes, very slightly!  Burning fossil fuels consumes O2 to create CO2, so for each molecule of CO2 produced, we add 1 carbon atom to the atmosphere.  This increases the mass of the atmosphere, which in turn increases the pressure at the surface.

By how much?  Let's do the math.  This might feel a bit roundabout, but stick with me.  The payoff should be worth it.

The total mass of the atmosphere can be found by integrating the density of the atmosphere with respect to altitude from the surface to infinity, (which gives us the mass of atmosphere over each square meter of surface), and then multiplying that by the surface area of the Earth.

Image

The density of the atmosphere follows an exponential of the form

Image

Doing a simple substitution, we can pull out a factor of kT/mg from the integral, leaving the integral of e-udu from 0 to infinity, which is 1.  The total mass of the atmosphere becomes 

Image

where ρ0 is the density at the surface.

Now we invoke the Ideal Gas Law, PV=NkT.  Divide both sides by VkT to get the number density: N/V = P/kT.  Then multiply by the mass per molecule to get the mass density ρ.  So we can sub this in for ρ0 at the surface, giving us

Image

Now at last we have a relation between the surface pressure P and the mass of the atmosphere.  And we know how much the mass of atmosphere changes when we burn carbon fuels to convert O2 to CO2 in the air.  So solve for P in terms of everything else:

Image

This is a pretty nice and simple result that could also have been found from intuition: the pressure at the surface is simply the weight of the atmosphere, which is its mass times gravitational acceleration, divided by the surface area.

What happens if we change the mass of atmosphere slightly?  Then the pressure changes by

Image

Plug in the values for the radius of the Earth (R = 6371km), g=9.81m/s2, and let ΔM = 1 ton.  Then this tells us the pressure at Earth's surface goes up by

1.92x10-11 pascals per ton of carbon burned.

Note: The mass of a carbon atom is about 12 atomic mass units, while a CO2 molecule is 44.  So for each ton of carbon burned, 44/12 = 3.67 tons of CO2 is "emitted", and 2.67 tons of oxygen is consumed.

Right now, humans are emitting about 10 billion tons of carbon per year into the atmosphere.  So this corresponds to an annual pressure increase of

0.192 pascals per year.  Or 1.9x10-6 atm.

Not very much. :)  Nor is the decrease in atmospheric oxygen associated with the combustion easily measurable.  What is measurable is the effect of the greenhouse gas on the Earth's energy balance, warming the surface and cooling the upper atmosphere.
 
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07 Dec 2018 02:53

 I have two words for you Wat: quantum computers!

ps- what greenhouse emission is also doing is increasing the moisture content of the atmosphere and H2O is an even more powerful greenhouse gas as is methane which is also going into the atmosphere at a higher rate.
 
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07 Dec 2018 03:46

A-L-E-X wrote:
Source of the post I have two words for you Wat: quantum computers!

For the average consumer and as a way to do "games" or Space Engine like programs?  Still not holding my breath.

A-L-E-X wrote:
Source of the post ps- what greenhouse emission is also doing is increasing the moisture content of the atmosphere and H2O is an even more powerful greenhouse gas as is methane which is also going into the atmosphere at a higher rate.

Yes, thanks to the Clausius-Clapeyron relation for water vapor.  This is also a part of the climate feedback effect where increasing the greenhouse gas concentration increases the surface temperature more than you expect just from the radiative forcing.

Thankfully, water vapor condenses and precipitates, so its levels are fixed by that relation and can't really spiral out of control.  CO2 and methane on the other hand do not.  So this leads to the counter-intuitive result that water vapor is the most significant greenhouse gas in the atmosphere (in terms of how much it warms the planet compared to having no atmosphere), while CO2 turns out to be the most important for understanding climate changes, both currently and throughout Earth history.
 
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07 Dec 2018 19:45

A-L-E-X wrote:
Source of the post read that short story I just posted, you will get an answer you did not expect!

That is my favorite Asimov short story. “INSUFFICIENT DATA FOR MEANINGFUL ANSWER.”

There is a great write-up about the story that I read recently here.


A-L-E-X wrote:
Source of the post As for the habitability of brown dwarfs, I also believe that exotic life could exist just about anywhere

Exotic life as you referenced would be unlikely, a brown dwarfs environment could be perfectly suitable for 'mundane' carbon based floaters if specific animo prerequisites are met. Certainly if ET life (if discovered) will be both familiar and utterly alien! 


Watsisname wrote:
Source of the post     A-L-E-X wrote:
   I have two words for you Wat: quantum computers!

For the average consumer and as a way to do "games" or Space Engine like programs?  Still not holding my breath.

Yeah, pretty sure quantum computers are going to be a little out of a armchair scientist or even professional's price range :lol:.


Watsisname wrote:
Source of the post or the ability to dissipate the heat away when it has to be doing that many computations that quickly in a confined space...

Well, space-based computation centers or those in very cold planetary environments would be ideal for this. I could see some actual industry based around this if we ever colonize places like Titan (despite it's tricky environment to overcome and industrialize). 
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07 Dec 2018 23:49

Watsisname wrote:
A-L-E-X wrote:
Source of the post I have two words for you Wat: quantum computers!

For the average consumer and as a way to do "games" or Space Engine like programs?  Still not holding my breath.

A-L-E-X wrote:
Source of the post ps- what greenhouse emission is also doing is increasing the moisture content of the atmosphere and H2O is an even more powerful greenhouse gas as is methane which is also going into the atmosphere at a higher rate.

Yes, thanks to the Clausius-Clapeyron relation for water vapor.  This is also a part of the climate feedback effect where increasing the greenhouse gas concentration increases the surface temperature more than you expect just from the radiative forcing.

Thankfully, water vapor condenses and precipitates, so its levels are fixed by that relation and can't really spiral out of control.  CO2 and methane on the other hand do not.  So this leads to the counter-intuitive result that water vapor is the most significant greenhouse gas in the atmosphere (in terms of how much it warms the planet compared to having no atmosphere), while CO2 turns out to be the most important for understanding climate changes, both currently and throughout Earth history.

I thought someone had already made an affordable quantum computer for the home (it was in the 1500 price range I think) it's not very powerful and more of a prototype, but it's been out there for a few years.
As far as higher humidity levels trust me I have been feeling it :(  I'm very sensitive to higher humidity levels and get really sick in them (it's harder to breathe and I get sinus headaches from higher levels of mold spores)..... there was some crazy stat about this summer, well generally dew points have been on the rise here since the 1980s, but this year exceeded all previous by a great deal.  Prior to 1983 the most number of 75+ dew point days at JFK was 19 and 1983 set the new record at 24 and since then we've periodically been between 20-22 in 75+ dew point days and this year we have had an astounding 42 75+ degree days which beat the previous record by almost double!  Also it's resulted in a huge increase in big precip events (both rain and snow).
I have been reading this increased moisture content is also increasing the risk for infections, particularly tropical infections in the summer, when most of the 75+ dew point days are occurring.
 
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07 Dec 2018 23:54

Stellarator wrote:
A-L-E-X wrote:
Source of the post read that short story I just posted, you will get an answer you did not expect!

That is my favorite Asimov short story. “INSUFFICIENT DATA FOR MEANINGFUL ANSWER.”

There is a great write-up about the story that I read recently here.


A-L-E-X wrote:
Source of the post As for the habitability of brown dwarfs, I also believe that exotic life could exist just about anywhere

Exotic life as you referenced would be unlikely, a brown dwarfs environment could be perfectly suitable for 'mundane' carbon based floaters if specific animo prerequisites are met. Certainly if ET life (if discovered) will be both familiar and utterly alien! 


Watsisname wrote:
Source of the post     A-L-E-X wrote:
   I have two words for you Wat: quantum computers!

For the average consumer and as a way to do "games" or Space Engine like programs?  Still not holding my breath.

Yeah, pretty sure quantum computers are going to be a little out of a armchair scientist or even professional's price range :lol:.


Watsisname wrote:
Source of the post or the ability to dissipate the heat away when it has to be doing that many computations that quickly in a confined space...

Well, space-based computation centers or those in very cold planetary environments would be ideal for this. I could see some actual industry based around this if we ever colonize places like Titan (despite it's tricky environment to overcome and industrialize). 

I'm also wondering about those complex organic chemicals we've found in interstellar gas clouds, those floaters could also exist there.  About exotic life, we really dont know what their requirements are, but inorganic silicon based life would be fascinating!
It would be nice to have a supercomputer that didn't need liquid nitrogen for cooling lol.


BTW I love that literally analysis especially this part

https://literative.com/literary-analysi ... ac-asimov/

  1. The entire course of the story, depicted by several stories, are meant to represent one stage closer to divinity for humanity. In the first story, humans are on Earth. In the next, they’re in space. Then outside the galaxy, then disembodied (minds), and finally, as merging with the AC and becoming the ultimate computer. By this, Asimov could argue that to reach divinity, one has to leave their humanity behind. But then again, he could also be arguing that the cycle of existence itself begins and ends with a bang. We’ll touch more on this next.
  2. “Let there be light” are words famously found in the Bible. Only this time, it’s not in the way you’d expect. In the story, God is really a mixture of humanity, and the technology it created, meshed together as one, after years and years of evolution. Upon finding an answer, AC begins the universe once again, with the Big Bang, knowing well that everything will end once again, in some distant future, and then repeat the cycle. To Asimov, this is the cycle of existence, the explosive beginning, and the reflective end.
  3. Judging by the fact that Humanity merged with AC, who then made the Big Bang, we’re both the creator, and the created.
  4. This is a prime example of the saying “the end is only the beginning.” To Asimov, the ending of something was always the beginning of something else. It can also be taken as we must all try and fail, succeed only to lose it all in the end, then do it again, as we are destined.
  5. We are all one and the same – Humanity – and as one collective being, we are in everything we’ve created, asked, answered, and been.
Whatever your background, or beliefs, I think most would agree that “The Last Question,” definitely does make you think about existence as a whole, and your small presence in the vastness of the universe. From a writer’s perspective, it teaches that a story is nothing but one point in a long spectrum and that in order to achieve greatness, one must never become used to one thing. Nothing is in stasis.
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07 Dec 2018 23:59

Wat: So, if we take past known emissions and projected future emissions, up to 2100 AD for example, the total added pressure by then will have been 1 or 2 pascals?
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08 Dec 2018 18:18

PlutonianEmpire wrote:
Source of the post Wat: So, if we take past known emissions and projected future emissions, up to 2100 AD for example, the total added pressure by then will have been 1 or 2 pascals?

For going out to the year 2100, the answer will depend a lot on what humanity decides to do, in terms of our emissions over time and potentially also carbon sequestration.  This is a crucial question for policy makers which will have important consequences for the magnitude of global warming.

To account for that uncertainty, we can express the pressure change in terms of, say, pressure added per 100ppm of CO2 in the atmosphere.  In that case, it ends up being about 4 pascals per 100ppm.  This is about half of what you expect from our emissions (~10GtC per year), because about half of the CO2 is absorbed into the oceans and biosphere. 
 
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08 Dec 2018 19:20

Well, I dont know if itd be politically correct, but I think human behavior can be partially accounted for region by region as a given anyway. In this case, the Western world will do a better job at fighting emissions because they care. East and Southeast Asia however truly dont give a dang and it is guaranteed the "Business as Usual" scenario is true for them
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08 Dec 2018 23:01

It also has to do with if we can reign in our population growth rate, to maintain a truly healthy environment, birth rate needs to be somewhere in the 1.8-2.0 range, preferably the lower end of that scale.  Some of these developing regions have an extreme birth rate in the 3-4 range, and even the US birth rate is a bit too high for my liking.

The single BEST way to reduce carbon emissions is to have one less child.  That also affects other kinds of pollution, habitat loss, and will slow down and hopefully stop the humanity generated mass extinction event we have going on right now.

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