BellGab.com Archive

Quote from: onan on February 10, 2016, 05:59:21 AM
Yeah you probably ebayed your character.

Don't tell anyone

LIGO press conference regarding gravitational waves is set for Thursday Feb. 11, 10:30 AM EST
http://www.ligo.org/news/media-advisory.php

This Friday the Japanese space agency launches the ASTRO-H mission, which will revolutionize our understanding of the Universe at X-ray energies. The launch can be viewed through the website on Friday at 3:30 AM EST (for those dedicated few)
http://astro-h.isas.jaxa.jp/en/

Quote from: Coffeeman on February 09, 2016, 07:58:58 PM
Sorry, it means "turn-based strategy". Honestly, I couldn't get into the new XCOM to finish it; though that it worked well as a console game was neat. The original Microprose game can be played on modern machines now through OpenXCOM. http://openxcom.org

Sort  of what I thought, if you liked the original, you'd probably like Invisible Inc.   
Kind of retro-themed, 50's scifi (not obnoxious, though) espionage strategy where every map, every campaign you start goes differently.

Looking forward to the new XCOM, but I really only bought it because of how much I loved the original and Terror from the Deep. I will check out openXCOM, I've been playing it through dosbox which works well enough. I also messed with Amiga emulation for a while but the Amiga and dos versions are pretty much indistinguishable to me.
I like the sound of Invisible Inc., I really loved the original Syndicate and a mashup of that with XCOM would really hit the spot. As for the 50s motif, remember Evil Genius?

Anyway I wish I would have figured out TBS on my own, now I've lost all cred and have been demoted to noob

Quote from: Coffeeman on February 09, 2016, 05:53:07 AM
Klei makes some great games. If you like TBS/tactical games, Invisible Inc. is another one by them I recommend. The procedurally-generated maps brought a lot of that tense, "what the hell's on the other side of that door" moments the original X-COM had.

I've never heard of Klei before but after the ninja game I'll be hungry for more.
I loved the original XCOM from back in the day, have not yet had the chance to play the latest one though it is installed on one of the machines in this house. What's TBS stand for anyway?

Quote from: ziznak on February 08, 2016, 10:39:34 PM
check out the virtual console stuff... lotsa old school games from the nintendo menu there.  check out Monster Hunter 4 ultimate... i'm going to hit 1000 hours someday soon just playing that game.

Will do, I haven't yet looked at all at the store. I got into the emulation thing a few years ago and haven't looked back since. So I feel I also owe Nintendo as well
MAME on a handheld would be really cool...

Quote from: area51drone on February 09, 2016, 03:07:18 AM
Cool, I don't really remember seeing that one.   You should check out the movie King of Arcades, it was pretty good too.   

I almost got the GORF working tonight.. the screen is scrolling horizontally, and doesn't play quite right but I got some sounds and you can sort of see the gameplay which was exciting.   Dusting off a game from 1981 that probably hasn't seen any action since the mid to late 80's is like a time capsule.  It even had an old analog multimeter sitting in the bottom of it.   I know virtually nothing about fixing vids, but I'll get it working.    I really bought it to turn it into a mame machine..  I think it's got cool art and the joystick is the same as Tron.   But I'll keep all the parts so I can put it back into a gorf at any time.

That's a really nice project. The end result is going to be so satisfying once you're up and GORFing.

Quote from: ziznak on February 08, 2016, 11:09:48 AM
what games have you been playing?

So far I have played New Super Mario Bros and Super Mario 3D Land, which came with the system. Both of them are 10/10 and gave the Nintendo quality I expected. I understand that A Link Between Worlds is also a must-play for this system, so I think that's going to be the one I try next. I haven't had a handheld around in many years, it's nice to be able to take a break from work, pop it open for a level or two and then go back. Takes no time to wake up from sleep when the screen is opened, so it's like having a game always on the go.

Also, I recently found this gem on steam and have had fun with it:

https://youtu.be/rI_r-g4VnsY
Haven't finished it yet but I'm hoping to have a bit more time with it soon. The stealth gameplay is great, reminds me of a cross between Metal Gear and Tenchu: Wrath of Heaven.

Quote from: area51drone on February 08, 2016, 09:52:43 AM
Make sure you get yourself one of these...   

http://www.sc3ds.com/

Whoa! Thanks for the heads up. Never heard of such a thing before.

Received a nintendo 3ds as a Christmas gift, I have not had this much fun with games in a long time. I'm impressed with the glasses-free 3d.

Quote from: Camazotz Automat on February 06, 2016, 06:42:58 PM
Fuckers.

Scientists and engineers are the worst.

REPORTED

Alright, on topic, I've been meaning to post about this lately and making the time for it today.

So not only can individual galaxies act as lenses, but entire clusters can too. This makes images on much larger scales, and can stretch individual galaxies out into arcs many times longer than wide. This takes the entire mass of the cluster - both luminous and dark - and the difference between the mass modeling and observations give the dark matter in the cluster, the stuff we can't directly measure from electromagnetic radiation. The presence of strong lensing features put strong constraints on the total mass distribution of the clusters and in general many images can be formed. Not only can you find long arcs, but these arcs can often be seen more than once. As an example, the cluster in the image below gives us many lines of sight to the blue galaxy, which shows up many times in this image of the lensing cluster. In fact these are all the same object!

The inset shows how these lensed arcs can be inverted to give back a view of what the source may look like. A good lens model will give consistent results between all of the images and as we can see aside from projection effects, the same features are identifiable and present in all of these projections. Now, what's interesting is that not only do we get multiple views of these background objects, the path length along each of these lines of sight is different. This means the light takes a different amount of time to get to us from along each path, so there is a time delay between the images as well. So if something happens at the source, we would see it first in image A, then after some time the change would show up in image B, then in image C and etc. So we could watch a "replay" of an event through a lens like this.

This is particularly significant because in the winter of 2014, multiple images of a supernova were found occurring in the background galaxy seen through the cluster MACS J1149.5+2223. We are able to detect this distant supernova only because of the magnification boost that the lensing effect provides, since it's too distant to see otherwise. The supernova is seen in a cross-like configuration below:

Now, since the host galaxy is multiply imaged, there should be another path the light could take to get to us, which will show up later, after we see this quad-view of the supernova. The mass models of the cluster all predicted it should happen a little more than a year later, and in fact a recurrence of the supernova, now called SN Refsdal after a pioneer of strong lensing studies was seen in December 2015.
http://frontierfields.org/2016/01/29/predicted-reappearance-of-supernova-refsdal-confirmed/
http://www.spacetelescope.org/news/heic1525/
The supernova should also have been visible in 1998, though no archival images from the time-frame exist.

This is amazing and jaw dropping for a few reasons. First, we are seeing the replay of an event that occurred 10 billion years ago in it's host galaxy, the details of which have been deflected and warped through the curved space-time of this cluster. Second, using gravitational mass models for this cluster we were able to predict the appearance of this object a second time accurately, so it shows that we have a good handle on the gravitational potential of this cluster that the models were all able to give consistent results. Third, we can learn a lot about cosmology, specifically the expansion rate of the universe, and the distribution of matter within the cluster itself. Finally, it's an exquisite example of scientific observation and theory in action. The models made a prediction and observations were able to bear it out.

This event is on the cutting edge of ongoing research, and I wish more media outlets had covered it. This has to be one of the most interesting and awe-inspiring releases from astrophysics I've ever come across.

Quote from: GravitySucks on February 06, 2016, 05:46:45 PM
I will pm you

Thanks, looking forward to it (and Onan's frustration)

Quote from: GravitySucks on February 06, 2016, 05:03:48 PM
AO, I really appreciate the time and effort you put into your thoughtful answers. It has helped me understand a little bit better, and given me some new things to go read about. I worked for 32 years as a NASA contractor, mostly dealing with the flight software of manned and LEO spacecraft. Generally we would have to take a systems engineering approach beginning with the spacecraft requirements. Usually I would have to rely on the scientists and PIs for all of the equations and instrument design for the various detectors. There was only so much IV&V we could do, we often had to just accept the fact that they knew more about the physics than we could ever hope to obtain.

Gravity became an interest of mine while working on the flight software and simulator software for the TSS missions. The thought of being able to use tethers to reboost or deorbit just fascinated me. I know that the physics of tethers only has gravity as a component, but that is what got me interested. I've been trying to understand it ever since.

Again, thanks for your patient response.

My pleasure, I love to discuss this stuff. I haven't had much time to spend online with bellgab in the past year and I've been enjoying some extra free time online lately.
Can you give a bit more detail on the contract work with NASA that you did and some more background on the TSS missions?

Amazing what you can do with just 1/r^2, isn't it?

To follow up the discussion on gravitational lensing, my favorite lensed galaxy image:

Among the background galaxies, the nearly complete blue ring is an extreme example of gravitational lensing. The red elliptical galaxy at the center is called LRG 3-757. it's a luminous red galaxy (the LRG part of it's name) and over a hundred times more massive than the milky way. A distant blue galaxy lies nearly exactly behind it and the gravity of LRG 3-757 stretches this distant galaxy out, distorting it's appearance into the ring seen here. For this kind of extreme distortion to occurs the galaxies have to be almost exactly aligned along our line of sight, so someone else looking a this system from some other galaxy would not see this cosmic illusion since the galaxies would not be aligned to them. From our point of view though, looking at this ring is like staring into a hall of mirrors. This example shows the effect of a lens made of space-time itself. Which is a mind-blowing concept to me. This image is particularly striking to me.
Also interesting is the huge amount of modeling work that's been done on these systems. That is to say the goal is to take an image like the one above, postulate some mass distribution for the lensing galaxy and then "unscramble" the blue ring to see what it might look like in the absence of any lensing effects. It's reassuring that the models for both the source and lens turn out to be relatively simple - see for example the analytical models on page 18 of this paper (
http://arxiv.org/pdf/0805.1931v1.pdf) and the more general results shown here pages 11 to 20 (http://arxiv.org/pdf/1307.4764v1.pdf).

Quote from: GravitySucks on February 06, 2016, 03:56:57 PM
I guess my fundamental questions aren't really specific to the lensing, but the effect of gravity on a grand scale. I was trying to wrap my mind around the effects of gravity on light and trying to determine how you would figure out the exact source/location of light without knowledge of the mass between the origin and the observation. All I could come up with is relative position.

Sometimes you do know how far away the lens itself is, since the lens can be seen. Then you can measure the redshift of the light from the lens to get an idea of how far away from you it is. That then just leaves the distance to the source, which you can include as part of the modeling scheme. This is why galaxy scale lenses are so nice to work with. Not only do you get the distance between you and the lens (hopefully) you also can observe the shape of the light-emitting bits of the lens. This is interesting and useful since total mass (luminous and dark) affect the path of light from distant objects. With extended scale sources you can also in many cases measure the redshift of the source as well which eliminates that part of the problem altogether. With stellar scale lenses, ideally you know the position of the source from observation and have to include lens distance as part of the model. This kind of microlensing was used to determine the fraction of dark matter in the Milky Way that can be made of planetoid-scale bodies that don't emit much light, stellar mass black holes, etc. This turns out to be only about 40% of the total mass needed for the kinematics of our galaxy to work out. The rest must be dark in a form we can't directly detect yet.

Quote from: GravitySucks on February 06, 2016, 03:56:57 PM
I still have troubles with the effect of gravity on light, especially when comparing the effects of black holes and regular massive objects. If a black hole can keep light from escaping past the event horizon, why wouldn't a massive object slow down the light? Or speed it up?  Just makes my head hurt. I still have troubles accepting the speed of light as a constant. Especially when I start thinking of Doppler shift. I know most of these are basic concepts, but when you throw in the concept of gravity warping space time, it really makes my head hurt.

I don't think they're basic concepts at all, really. You need relativity to describe these effects so they're sufficiently advanced imo.
We're used to thinking of light as particles, you do it above when you say it should slow down or speed up. But this is a complicating picture classically because light has no mass. More generally light is a wave, and with GR it's the wavelike properties that are most easy to understand. When a light ray loses energy it doesn't slow down like a conventional particle, instead the frequency of the light decreases and it's wavelength increases. The ratio of these quantities is always invariably the speed of light. This is the origin of the gravitational Doppler shift. The energy and momentum that an electromagnetic wave carries can change, but it's velocity remains the same.
In most of the literature, light is described simply as a "ray", and the trajectories that these light rays travel along are called null geodesics or null paths. These paths have a number of interesting properties that are distinct from the paths that observers with a non-vanishing mass. 

Quote from: GravitySucks on February 06, 2016, 03:56:57 PM
What type of mass does it take to warp space time?  All mass has gravity, does that mean the smallest molecule warps space time?

This is a fundamental question many scientists are grappling with and you've nailed the core question to quantum gravity right here. Since gravity is so weak to begin with measuring gravitational effects on tiny masses is very difficult. So the question if gravity behaves the same way beneath some limiting distance is a fundamental one. Right now using the most precise equipment the inverse square law of weak field GR can only be measured down to a cm, maybe a bit below that. No one really knows what happens at smaller scales. Some have speculated that there is a phase change that occurs or that the gravitational constant itself is different below some distance and that's how GR and quantum mechanics can be sewn together neatly. But right now we just don't know for sure from observation.

Quote from: GravitySucks on February 06, 2016, 03:34:28 PM
http://www.urbandictionary.com/define.php?term=chasing+rabbits

With gravitational lensing, how in the hell do we know where anything was really at when the photon was emitted?

Well, what kind of lensing are you talking about? Lucky for us, most large things like galaxies and galaxy clusters evolve on long timescales so their positions are pretty constant with respect to one another. When individual stars lens one another the timescale of the event can usually be measured.

Of course there is also the overall travel time so with any lensing we're seeing these things happen back when everything was lined up. The relative positions of the lens and source "now" (at the time of our observations) are a snapshot in time since the speed of light is finite. All that goes into lensing models are the relative positions of the source, lens and observer, which may vary on short enough timescales to be measurable (which is the case for microlensing which involves a stellar-scale lens).

Quote from: onan on February 06, 2016, 02:22:05 PM
So, Thor's Hammer, what is the story with it and gravity? To explain (probably not necessary because everyone knows about Thor's Hammer), it is too heavy for anyone to pick up except Thor. Yet when he rides an elevator, the elevator is not strained. I need help with this.

To fly, he throws the hammer and then holds onto it tightly. I might need some help with this too.

Quote from: GravitySucks on February 06, 2016, 01:07:19 PM
I just got finished chasing rabbits.  Gravitational lensing. My head hurts. I gave up.  Gravity sucks.

Is chasing rabbits a book? Or what?

I love gravitational lensing

Quote from: ziznak on February 06, 2016, 03:34:07 AM
hey man was great hearing you call in the other night! you should volunteer to host some time homie

That would be a lot of fun.
It was my first time talking to Art

Quote from: area51drone on February 06, 2016, 03:03:58 AM
Have there been any published false positives from shot noise across multiple detectors?

No idea, offhand. I don't have much experience with interferometry at all or have any intuition about the effect photon counting statistics have on the noise floor. Since lasers are used in the interferometer arms you expect Poisson type processes to add background but these are incoherent events. The team has been able to detect injected test signals from the background, which is a good sign of course. Details about these blind tests can be found here (http://www.ligo.org/news/blind-injection.php). But the detection is all about signal to noise ratio, like any other measurement on a CCD.

Also, the rumors around the apparent LIGO gravitational wave detection next Thursday keep on growing:
http://www.sciencemag.org/news/2016/02/woohoo-email-stokes-rumor-gravitational-waves-have-been-spotted
Huge news if confirmed next week.

Edgar Mitchell passed away
http://phys.org/news/2016-02-astronaut-edgar-mitchell-6th-moon.html

Spoilers ahoy!

First off, let me say that I liked both of these episodes, they both sort of feel like they fit with the older seasons of the show in terms of tone. But there were some things I disliked too.

I really hoped that Mulder & Scully would have gone their separate ways in the years following the closing of the X-Files and that we would not be left with this broken relationship baggage. Maybe part of what made the original so interesting was the tension in the show between Mulder and Scully, though that tension was probably gone by the end of the show anyway. But after such a long hiatus I was hoping to see a bit of it back, and maybe some of that flame could be rekindled. Instead they both seemed a bit burned out and that maybe that's an aspect of the show that won't return until we have some new agents working X-Files cases? I also thought it was awkwardly handled when Tad was making moves on Scully in the first episode, it felt forced and badly written to me. Joel McHale was a bad choice for the character of Tad also imo. 

I'm also a bit confused with respect to the setting of the show now as well. During the first episode Mulder and Tad rolled all the conspiracies under the Sun together in a big ball. But other than Roswell, very little of that had to do directly with aliens, and in fact the big "revelation" was that humanity has had no contact with aliens, and that the government is behind it all. I have some problems with this. Wasn't there an out and out war going on between humans and aliens in the last iteration of the show? We saw green blood being thrown around and other such business even when the main characters weren't around. All of that was apparently just a war between factions of the government, or what? And also I think this whole idea that the military industrial complex was responsible for all of it was already explored in an earlier season? Was Tad O'mally completely a set up by the cigarette smoking man to throw Mulder off the trail? Even the brief glimpse of the CSM was definitely more sinister at the end of the show than I remember him.

I didn't like that despite everything from the earlier seasons, Scully is still a hard-line unbeliever and that she is completely closed minded. She has been taken aboard a UFO, had embryos harvested and given cancer from a conspiracy centered on aliens. Also I had hoped that when Mulder was re-introduced he may have been doing a podcast or web show from a camper in the high desert for some portion of the intervening years.

Anyway overall not bad, I will continue to watch. 7.0/10

Waiting until tomorrow night's episode to comment. Will say I'm a bit confused right now, hope tomorrow nights show clears up some of my questions.

Quote from: FearBoysWithBugs on January 20, 2016, 09:04:00 PM
Yah, I got interested and looked into it, and as you say, the matter seems to have been settled to everyone's satisfaction within the last few years as being caused by anisotropic heat radiation from the RTG. 

One thing I discovered in this look at the issue that I didn't see (or maybe didn't understand) was why the Voyager spacecraft couldn't be used for additional data.  The Voyager spacecraft used thrusters to orient the craft, and that activity introduced uncertainty in the motion of the craft that couldn't be screened out.  Pioneer, by contrast, used spin stabilization to keep the antenna pointed towards Earth. 

The New Horizons craft used spin stabilization for most of the journey, plus it had an instrument aboard that could be used to analyze the Pioneer effect.   Yay?  Well, this was of course designed in and flown years before the more recent conclusions about the thermal recoil.  Also, it has the RTG located near one end of the spacecraft, for heat management purposes in the inner solar system if I'm understanding it correctly (always a risk), so the data that's gathered might not be as reliable.

Yes. It seems as though there's a chance for New Horizons to take a shot at a measurement but disentangling heating and minuscule dynamical effects are difficult since the effect is expected to be small anyway. The impression I have is that none of the spin-stabilized spacecraft to pass by Earth has shown evidence of the flyby effect, but I may be mistaken about that. Juno did not show such an effect, and I have not yet found anything in regard to Hayabusa2 which looped past us in December.

Quote from: Shaz on January 20, 2016, 02:03:22 PM
Fresh out of Fermilab...
http://news.fnal.gov/2016/01/dark-energy-survey-releases-early-data/

Oooooooo
Cant wait to see what comes of this, the project has very lofty goals

Quote from: Northern Nights on January 20, 2016, 07:36:58 PM
It will be interesting to hear what RCH has to say about this.

Strap in for 19.5 gs of crazy

Quote from: FearBoysWithBugs on January 20, 2016, 07:27:54 PM
People have been predicting the existence of Planet X since Neptune was discovered.   A prediction is not a discovery.  And these guys, for some reason, are passing up the priceless opportunity to discover an actual fuckin planet by releasing their prediction to the media.

Yeah, okay, whatever.  They're talking about something that orbits the Sun once every ten or twenty thousand years.  IF it exists, it hasn't made a complete orbit in recorded history, much less during the time when its effects could have been observed.

I think whatever is responsible for the Pioneer anomaly is also responsible for the deviations from predicted orbits or trajectories that have been observed.  It's relativity and the orbit of Mercury all over again.

Hay A:O, dint they put something on New Horizons to test for that?  Any results thus far?

That's interesting, I haven't heard anything about the status of New Horizons with respect to the Pioneer anomaly, it was suggested as a test but I have not heard anything about it.
I am very skeptical of the pioneer anomaly especially since it can apparently be explained by non-uniform thermal effects.
There's also an interesting flyby anomaly which is also on shaky ground. The effects are really small, so difficult to measure. Talking about mm/s on each pass.

A short article about asymmetric heating aboard Pioneer: http://www.nature.com/nphys/journal/v8/n9/full/nphys2428.html
And an indepth discussion of the flyby anomaly:
http://issfd.org/2015/files/downloads/papers/153_Jouannic.pdf

Quote from: onan on January 20, 2016, 06:56:36 PM
The story I heard had a large qualifier, that it was all speculation, lots of numbers pointing to a gas giant but no proof.

In 2014, the far-infrared view of instruments aboard the WISE satellite eliminated the possibility of Jupiter and Saturn size planets in the outer solar system. But there has been talk of smaller bodies that may explain the orbital behaviors of objects in the outer Kuiper-belt / inner Oort cloud. So now it has been again predicted by this group, 10 Earth masses is large but within the limits checked by WISE. Whether such an object is really there, no one knows yet. However it sounds like it should be detectable provided it's not at its maximum distance from the Sun.

Wait and see

A very large body out there is pretty surprising, apparently Planet Nine is about half the mass of Neptune, which is big. But there's got to be a lot of interesting stuff out in the depths of the Kuiper belt on elongated orbits we don't know of yet. It's interesting how many questions regarding orbits of other bodies it can tie up in a seemingly nice bow. Would be amazing if it were discovered.

I loved the last scene. After being presented with his legendary weapon Luke turns his back on thirty years of pacifism to set galactic affairs right.

The more I think about the movie the more details are tucked away into single lines that were glossed over. When we first see him, Snoke calls Kylo Ren "leader of the knights of Ren" or somesuch, and in Rey's force induced trip we saw Luke put his robot hand on R2, as well as Rey surrounded by a gang of dudes in armor with bodies scattered around. So are those the knights of Ren, and does it mean we'll see them trash Luke's Jedi school and kill his students in the next one, or is that what they were going for? I think that's an interesting set up, it would be awesome to see Luke throw down with those guys.

And I'm guessing Kylo Ren will be a lot more badass when he kills Luke!