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A-L-E-X
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14 Nov 2020 13:24

Wow nice 26 page paper Wat!  I've just started reading it.  Meanwhile I found the quanta magazine article that was where the article from my post appeared in:

https://www.quantamagazine.org/the-orig ... -20191029/

Please read Barry Plotkin's comment (it's the first one at the end of the article.)  Do you concur with his assessment, Wat?  Basically they are claiming that time is an emergent property at the fundamental quantum level.

https://www.quantamagazine.org/what-is- ... -20200316/

https://www.quantamagazine.org/the-blac ... -20201029/

In a landmark series of calculations, physicists have proved that black holes can shed information, which seems impossible by definition. The work appears to resolve a paradox that Stephen Hawking first described five decades ago.

Information, they now say with confidence, does escape a black hole. If you jump into one, you will not be gone for good. Particle by particle, the information needed to reconstitute your body will reemerge. Most physicists have long assumed it would; that was the upshot of string theory, their leading candidate for a unified theory of nature. But the new calculations, though inspired by string theory, stand on their own, with nary a string in sight. Information gets out through the workings of gravity itself — just ordinary gravity with a single layer of quantum effects.

-WAT, is any of this as earthshattering (or universe-shattering as the case may be) as they claim it is?

https://www.quantamagazine.org/physicis ... -20160419/
 
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14 Nov 2020 13:31

Wat your excellent explanation is exactly why I want to see the CMBR in SE.  I also want to see if what Penrose saw is actually there.  I see it's been disputed and it would be wonderful if we could analyze it ourselves in three dimensions.
 
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16 Nov 2020 01:06

A-L-E-X wrote:
Source of the post Wat your excellent explanation is exactly why I want to see the CMBR in SE.  I also want to see if what Penrose saw is actually there.  I see it's been disputed and it would be wonderful if we could analyze it ourselves in three dimensions.

Well, there's nothing really to gain in three dimensions. The CMB photons fill the whole universe, but we only detect the ones that are currently reaching us, having traveled at the speed of light from the time when the universe became transparent. So we see the CMB as a 2D spherical shell, "the surface of last scattering", surrounding us.

There is also not much you could tell regarding Penrose's idea from just looking at a CMB map. I'm sure you've seen many maps of the CMB anisotropies, but you can't really tell any difference between the observed distribution of these variations and what you would expect to see from LCDM cosmology. For example, you may have heard of an anomalous cold spot in the CMB, and sometimes people try to point it out by circling one of the most obvious cold spots. But that cold spot is actually consistent with LCDM expectations. The anomalous cold spot is fairly non-obvious by visual inspection. And whereas the anomalous cold spot is well established, because the methods for testing for it are quite conventional, cosmologists were not convinced by the methods Penrose used to claim evidence supporting CCC, and subsequent analyses do not show these features to be of statistical significance.

Another example is what we just talked about with two-point correlations of galaxies on the sky. The bump in the correlation function at around 150Mpc is statistically significant, but you would never be able to notice it by just doing a visual inspection of a map of the sky, or by looking at the 3D distribution of galaxies in Space Engine (if Space Engine showed the real distribution at those scales).
 
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16 Nov 2020 06:06

Right I saw the subsequent studies and they didn't show what Penrose thought they saw.  

It's mentioned here

https://en.wikipedia.org/wiki/Conformal ... ical_tests

Basically, it's stated Penrose used an undocumented nonstandard approach.

Then in 2013 he used a different approach, one which is not based on simulations ("sky-twist procedure") in which WMAP data is directly analyzed.  In 2015 that data was published after Planck data analysis, including they say "the inhomogeneous distribution of those structures."

Then there's another paragraph about another group in 2018 that concludes that regardless of the validity of CCC that the new research into the CMBR data is important new input and may be indicative of "Hawking Points" indicative of Hawking evaporation of supermassive black holes from an eon prior to ours (previous cycle).  Then more updates in 2020 from another group that it isn't statistically significant followed by another paper from the Penrose group of anomalies in the CMBR that can't be explained by the conventional inflationary model but can be by Hawking points.

My question is why can't they both be right?  Why can't you have a previous contracting universe (deflation) followed by a Big Bounce and then a rapidly expanding (inflation) universe?

https://arxiv.org/abs/1302.5162

https://arxiv.org/abs/1512.00554

https://arxiv.org/abs/1808.01740

https://iopscience.iop.org/article/10.1 ... 020/03/021

https://arxiv.org/abs/1909.09672

https://academic.oup.com/mnras/article/ ... 03/5838759

https://arxiv.org/abs/1808.01740

https://arxiv.org/abs/1512.00554

At the end they even talk about the possibility of intelligent information transfer between eons/cycles.  This is all pretty interesting Wat, but to me at least it seems like they are grasping at straws to try and confirm their conjectures?  Or maybe there is something to it.  What do you think?
 
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16 Nov 2020 10:30

A-L-E-X wrote:
Source of the post Why can't you have a previous contracting universe (deflation) followed by a Big Bounce and then a rapidly expanding (inflation) universe?

It could be possible, but it might also not be possible, and even if it is possible according to a theoretical framework, it might not be the correct description of how the universe evolved.

It might be useful to contrast this with the idea of a Big Crunch. According to general relativity and the Friedmann equations, a Big Crunch is an inevitable end-state for a universe containing more than the critical density of matter, and no dark energy. We may call it a correct description of how a model universe can evolve, but it doesn't appear to be the correct description for the universe we live in, because we observe an accelerating expansion due to a significant amount of dark energy, which leads to a very different kind of end-state.

What would happen to a model universe after it collapses in a Big Crunch? It might be tempting to believe it should do one thing or another. Maybe it expands again in a new Big Bang, or maybe it just remains crunched. But no one actually knows the answer because we don't have an established theory of quantum gravity.
 
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19 Nov 2020 22:21

Watsisname wrote:
A-L-E-X wrote:
Source of the post Why can't you have a previous contracting universe (deflation) followed by a Big Bounce and then a rapidly expanding (inflation) universe?

It could be possible, but it might also not be possible, and even if it is possible according to a theoretical framework, it might not be the correct description of how the universe evolved.

It might be useful to contrast this with the idea of a Big Crunch. According to general relativity and the Friedmann equations, a Big Crunch is an inevitable end-state for a universe containing more than the critical density of matter, and no dark energy. We may call it a correct description of how a model universe can evolve, but it doesn't appear to be the correct description for the universe we live in, because we observe an accelerating expansion due to a significant amount of dark energy, which leads to a very different kind of end-state.

What would happen to a model universe after it collapses in a Big Crunch? It might be tempting to believe it should do one thing or another. Maybe it expands again in a new Big Bang, or maybe it just remains crunched. But no one actually knows the answer because we don't have an established theory of quantum gravity.

I think this theoretical stuff is the most fascinating area of science because it's something we may never know (I hope once we solve quantum gravity, we'll have a better idea.)  My favorite conjecture (as you probably know already lol since I talk about it so much) is the phantom energy scenario with the universe "coming back empty" for which we need special conditions that may or may not be possible.....it'll be close (according to what we know right now.)
PS on another subject entirely.  I hope you have a chance to watch Cosmos:  Possible Worlds at some point.  Season 3 Episode 7 was absolutely fantastic (so are the others but this recent episode really stood out to me.)  
Excellent narration by Neil DeGrasse Tyson.  Season 3 Episode 7- The Four Kingdoms of Life- was particularly memorable.  He mentioned the intelligence and empathy of trees and bees (and the mathematical and astronomical knowledge that bees possess) and how humans first need to realize the sentience that exists on earth itself before they go looking for it elsewhere.
He pointed out some things I had never even thought about with regard to how trees and bees behave.
Talks about empathy, sentience and intelligence among nonhumans (including trees!)  And how human-centricism may prevent us from recognizing it elsewhere.
 
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20 Nov 2020 05:24

I was curious about closest stars to the Solar System in the past/future and I found out about Gliese 710.

I discovered these is an addon by FastFourierTransform that puts that star in the position that is predicted to be in the future, and it's awesome! But I was wondering... did they take gravitational pull of other stars into account to calculate the distance of approach? Also the research says the star is moving very slowly, so I think their attraction must be considered! Or is it negligible?
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20 Nov 2020 09:38

Salvo wrote:
I was curious about closest stars to the Solar System in the past/future and I found out about Gliese 710.

I discovered these is an addon by FastFourierTransform that puts that star in the position that is predicted to be in the future, and it's awesome! But I was wondering... did they take gravitational pull of other stars into account to calculate the distance of approach? Also the research says the star is moving very slowly, so I think their attraction must be considered! Or is it negligible?

I love this add-on!  I just wish we could model the proper motion of at least the main stars to be able to model what our constellations would look like (say) 10,000- 100,000- to maybe even a million years from  now!
 
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25 Nov 2020 00:13

 
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02 Dec 2020 03:09

Just watched the latest mindblowing episode of Cosmos: Possible Worlds with Neil Degrasse Tyson and he talked about the dual nature of light, quantum mechanics, possible parallel universes (MWI style) and higher dimensions.  When discussing entanglement and instantaneous action at a distance and how it violates classical physics and how two particles entangled together though billions of light years apart can change spin at the exact same moment, until an observer interferes by the mere act of observing (and violates relativity for that matter), he brought up the idea of superdeterminism, something I've been considering for awhile now as the only way out of the quantum paradox, that the entire history of the universe was actually decided at its inception (no free will,etc.)  I've always believed free will to be an illusion, and that behavior at the quantum level shows that instead of cause and effect, the entire history of the universe was decided when it was rebooted.  His point though was just because free will is an illusion it doesn't mean we should behave as though we know it's an illusion.
 
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02 Dec 2020 17:54

Salvo wrote:
Source of the post I discovered these is an addon by FastFourierTransform that puts that star in the position that is predicted to be in the future, and it's awesome! But I was wondering... did they take gravitational pull of other stars into account to calculate the distance of approach? Also the research says the star is moving very slowly, so I think their attraction must be considered! Or is it negligible?

It is negligible. :) 

In the paper, they calculate the closest approach by numerically integrating the motion (derived from Gaia data) of the stars within an axisymmetric model of the gravitational field of the Milky Way. But they do not model the attraction of individual stars. By how much would their answer change if they did account for the attraction by the Sun?

Let's say that, without the attraction, the star approaches at a minimum distance (called the "impact parameter"), b, with a speed v. A quick approximation for how much the minimum distance would be changed by attraction is to calculate the acceleration a of the star due to the Sun at the former minimum distance, then apply that through a time Δt equal to the impact parameter divided by the speed, and then double the result.  This gives a reasonably close approximation to the true amount of deflection.

Putting it all together, the correction to the minimum miss distance is Δx = 2*0.5aΔt2 = (GM/b2)(b/v)2 = GM/v2

The star is projected to miss the Sun by about 13365AU with a speed of about 13.8km/s. Plugging those values in with the mass of the Sun, I find the correction to the minimum miss distance is about 4.7AU, which is only about 0.03%. Pretty negligible. You would not be able to see the difference in an orbital overview (it will be smaller than a pixel in a 2048x2048 image).

As a sanity check, I also calculated the actual deflection directly by integrating the path using the Sun's gravitational field, which gave me a change of 3.46AU (0.026%). So the approximation was close but a slight over-estimate.
 
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02 Dec 2020 18:24

Wat would this in any way affect the Oort Comet Cloud or the Kuiper belt objects?  Perhaps we might get a great comet or two nudged our way or perhaps something we dont want to see?

I thought Barnard's Star was supposed to be our closest star in a few thousand years?

PS have you been watching Neil DeGrasse Tyson's Cosmos: Other Worlds series and if so what do you think of it?
 
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02 Dec 2020 20:06

A-L-E-X wrote:
Source of the post would this in any way affect the Oort Comet Cloud or the Kuiper belt objects?

See FastFourierTransform's post, where he did a really nice job discussing this with you in quite some detail. 

A-L-E-X wrote:
Source of the post PS have you been watching Neil DeGrasse Tyson's Cosmos: Other Worlds series and if so what do you think of it?

I have not been watching it, but I watch very little TV these days anyway.
 
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02 Dec 2020 22:11

Yes I'm very picky about what I watch also.  It has to be science based and there isn't much of that around.

I went back and remembered the thread when I read it, but I also remember why I never added it.  I think SE is only capable of capturing single moments of time....I really wish there was a way to simulate the motion of stars using the time indicator where I could actually use the proper motion of stars to see what our skies would look thousands and even millions of years from now.  This add-on would basically be a single snapshot in time rather than modeling the movement of the star as it approaches us.
 
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03 Dec 2020 03:01

A-L-E-X wrote:
I went back and remembered the thread when I read it, but I also remember why I never added it.  I think SE is only capable of capturing single moments of time....

Yeah, as you read in the post it's because stars are rendered within octrees. These kind of problems are a constant in game development, for example I had a very big and detailed map, but if I rendered the whole map in one frame the game goes at 10 FPS, while if I render just a small portion of it depending on where I am (it's called occlusion culling) I can have 60 FPS!

With procedural games it's much more difficult because you can't generate the portions in real-time, since they're different each time, that's why Space Engine generates the octrees once on startup and then the startup is much faster.
I just wanted to explain why Vladimir said it can't be developed, even if I also wish it was possible...

P.S: Sorry for off-topic, even if Information Technology might be considered science  8-)
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