BellGab.com Archive

http://youtu.be/7yxaUi8LIzE

Love the new avatar Cam, glad to see you put on the damn glasses

Hey noobs, how's it going?

Quote from: DigitalPigSnuggler on October 23, 2014, 08:33:11 AM
Fear not Onan, the movie is not about boners.  Rather, it is the patrons sitting next to you like me and A : O who have boners.  Nothing to fear.  So go, watch and enjoy!

Protip: Don't reach into any offered popcorn buckets during a showing of Interstellar

Quote from: DigitalPigSnuggler on October 22, 2014, 09:05:11 PM
Okay, that's two boners so far.  Anyone else?

Count mine twice and start with three

Quote from: coaster on October 22, 2014, 08:37:58 PM
The lastest one I've been working on-

This is amazing

Quote from: b_dubb on October 22, 2014, 07:43:52 PM
...

*gush*

A giant in the field, good to hear all of this. Now even more excited!

Quote from: DigitalPigSnuggler on October 22, 2014, 11:01:27 AM
I'm interested to see it too, based on the trailer, and I am going to be really pissed off if it's a letdown.

I noticed a few pretty accurate depictions of gravitational lensing in the trailers, including an accretion disk. That, to me, is a good sign for a sci-fi.

Looks really awesome, and with Chris Nolan's previous films setting a high bar, I can't wait to see what comes of it. The trailer makes it look like they got a lot of small details right, and that gives me hope. Can't wait to watch it.

And a few links from yesterday:

Signatures of starquakes found in giant flares from magnetars:
http://www.nasa.gov/content/goddard/nasas-fermi-satellite-finds-hints-of-starquakes-in-magnetar-storm/#.VEckUEvZAeE_______________________________________________
An equivalent of magnitude 23 quakes act on these neutron stars during their bursts, shattering their crusts and injecting the magnetic fields around them with huge atomic fireballs that are strong enough to affect Earth's magnetic fields even from light years away

POLARBEAR claims to see evidence of cosmological B-modes which measure gravitational lensing by substructure forming between now and the Universe's origin
http://ucsdnews.ucsd.edu/pressrelease/polarbear_detects_curls_in_the_universes_oldest_light
They may also have something to say about the BICEP2 results on primordial B-modes as well, since they also have two other papers in the chute. this makes the upcoming joint planck/BICEP2 paper even more interesting...

Quote from: zeebo on August 25, 2014, 02:01:57 PM
I'm pretty sure even in my 'scope I've only really seen the bright core of Andromeda they mentioned.  To pick up those wispy arms you need more optical horsepower I think. 

I do remember reading somewhere that it is the farthest object away you can see with the naked eye, which is pretty cool.  And I suspect most people don't realize how much crazier far away it really is. 

The bright star Vega is only 25 lt. yrs. away, while Andromeda is 2.5 million lt. yrs. from us ... 100,000 times farther away.   

Quote from: zeebo on August 25, 2014, 03:35:26 PM
Something to ponder whilst checking out Andromeda, is that the light you're picking up started it's journey to us around the very beginning of the Stone Age:

The Stone Age or Paleolithic Period is the name archaeologists have given to the beginning of archaeology--that part of the earth's history that includes the genus Homo and our immediate ancestor Australopithecus. It began approximately 2.5 million years ago, in Africa, when Australopithecus began making stone tools, and ended about 20,000 years ago, with big-brained and talented modern humans spread all over the world.

These posts made the hairs on the back of my neck stand up and gave me goosebumps. This is all converging on an extremely interesting and perhaps also somewhat obscure fact which makes me feel awe and reverence every time I really think about it.

As Zeebo very nicely said, the light rays that enter the pupil of our eye and form an image of the Andromeda galaxy on our retina began their journey to us when our species was still hanging from tree limbs. This is due to the finite speed of light, c, and the huge gulf of space between us and our nearest neighboring galaxy. From our perspective, the light ray takes a huge amount of time to make the trip from Andromeda to us. Now let's think a little more about objects moving close to the speed of light. We know from special relativity that no material object can move at the speed of light itself but you can approach it arbitrarily close if you have enough energy to get yoursef moving that fast. The faster you go, the slower and slower time seems to run relative to an observer at rest with respect to you. Thus, you can spend a year exploring the Universe at 0.99999999c, and return home to find centuries have passed in your absence but you have hardly aged at all. The catch is, no matter how fast you travel you will always age a little bit, because you just can't move at the speed of light. You have a finite, non-zero mass and the consequence of this means you can never get the energy you'd need to propel yourself along at the ultimate speed limit, c, the speed of light itself.

Now, light rays - photons - do not have such a restriction because they have no mass. They always move at c by their very definition. Since they are massless, photons travel on paths through space-time called null geodesics. These paths have very interesting and non-intuitive properties. Time is a little different to the massless particles that move along null geodesics than it is for material particles. While we see a photon taking a finite time to get to us, the photon itself does not experience time at all. To a light ray, no time passes from its emission and its absorption. This implies space doesn't really have much meaning for a photon either. In analogy to material particles this is an extreme example of Lorentz contraction and time dilation. Photons are the limit at which space and time are contracted and dilated away to entirely nothing. A light ray from Andromeda does not perceive any difference between the prehistoric age of the apes and us.

There is something deep and profound about this idea to me.

Since time is maximally dilated along a light ray, all the moments we experience between the photons creation to annihilation are "now" from it's point of view, and all points from the beginning to the end of it's trek is "here". This is an alien, holistic type of description of the Universe that is completely outside our every day experience and gives one of the best examples where mathematics has to lead over our intuition. It is a beautiful example of the truth in Einstein's words when he said "the distinction between past, present, and future is only a stubbornly persistent illusion".

It's pretty mindblowing to look at Andromeda and think about all of this. But even more so, consider what it means for a photon from the cosmic microwave background. For this photon, emitted at the time of last scattering only 300,000 years after the big bang, "today" and "then" are effectively identical, and the path it has taken through the 13 billion plus years getting to us is nothing more than a step. In that sense there is no distinction between the early Universe and today. In some way far outside our own limited perspective we are in direct audience of the origin of the Universe at every moment, no matter where we are, connected in an ephemeral way with the ultimate birth of whatever it is we mean when we say "reality". I'd be hard pressed to say that I have ever found a more awesome (or dare I use the term spiritual?) concept than that in my life.

I dropped Bob in only 5 distance units away from the hole, so there should already be some serious time dilation out there. It's only a few Schwarzschild radii away from the event horizon and innermost stable circular orbit. This means that small displacements cause big changes right out of the gate. Coupled with the somewhat squashed y-axis makes the disagreement look very large. If I had started Bob out further away then the curves would indeed track each other much more closely at the beginning. I should check more closely the scaling but I think it's right.

I agree that it was not the best choice to illustrate the effect, but I'd argue that it still makes the point I was trying to make.

Quote from: DigitalPigSnuggler on September 26, 2014, 01:20:47 PM
Someone traveling into a black hole would not be aware that he had crossed the event horizon.  For him, everything around him would behave as before crossing that line.  At this point, though, his fate is sealed.  He is doomed to be pulled into a long noodle and then pulled apart, his mass accreted by the singularity.  But before that gruesome end, he would see the progress of the universe moving faster and faster into the future.  So quickly that there would be no time to analyze it.  It would be a very exciting way to die, though.

That's not exactly how it works.  We see the star in motion until it slows down to the point that it appears to have stopped.  That image fades out, but the formation of the black hole continues, out of our observation.  The star disappears, and now there is a black hole.  Or so goes the theory.  Since we can't observe a black hole directly, there's often a disclaimer of the type outlined by AO above: it's either a black hole, or something different that behaves like a black hole in all of the ways that we can observe.

There was a short exchange of posts on the nature of black holes and what a collapsing star might really mean. In this case, DPS responded with this excellent post which neatly sums up the general outline of what is thought to happen. All I have to add to this explanation is to say it in a slightly different way (and maybe muddy the waters).

Image that there are two observers, observer A and observer B. It's become sort of customary in discussions of quantum mechanics to denote these two observers as Alice and Bob, so let's stick with that convention. Let's say Alice stays a good distance away from the black hole, and let's say the black hole is completely isolated, with no accretion disk nearby or any other objects that can confuse the situation. Observer B, Bob, decides to see what happens when he gets close (which will be somewhat suicidal, but hey - science).

The question then is what do these observers see when Bob gets near the black hole?

Alice is far away enough that the influence of the black hole on her is negligible. She may be thought of as being a cosmological distance away from it, or if you prefer her distance "approaches infinity" to use a more mathematically suggestive way to say it. Bob, on the other hand, starts at some distance away from the "center" of the black hole and undergoes free-fall toward it. No other effects influence Bob's motion through than the curved space-time around the black hole. Only gravity acts on Bob. Now, suppose that both observers time how long it takes Bob to fall toward the black hole. When Bob is five unit distances away from the black hole, he will record the time from his watch and Alice will record the time from her watch. As Bob gets closer to the black hole, he and Alice will disagree on how much time has passed. Relative to Bob, the clock he carries records what is called "proper time" and Alice's watch will measure what is called "coordinate time". How much does the radial distance vary as a function of these measures of time? How would Bob experience his own sense of time and how would Alice record events involving Bob from her perspective? By taking into account the curvature around a non-rotating black hole (the Schwarzschild solution) and some other simple tools from classical mechanics we can find differential equations that describe both of these interesting quantities. The solutions to these equations of motion produce curves that give the distance of the observer from the center of the black hole as a function of time, both coordinate time (what Alice will measure on her clock) and proper time (as shown on Bob's wristwatch).

I did exactly that and made the following plot to illustrate what should be seen according to general relativity. On this plot the center of the black hole is at r=0, on the lower left of the diagram. Bob begins at rest a distance of five units from the center (the lower right corner). The spherical surface of the event horizon is marked by the vertical dashed line at r=2. For now let's keep the discussion uncomplicated and just say the units are arbitrary. Bob immediately starts free-falling toward the black hole under the influence of it's gravity. The red curve shows how far Bob is from the center according to him, and the blue curve shows how far Bob has travelled according to Alice. 



The equations of motion for bodies near the black hole show that Bob experiences nothing strange as he crosses the event horizon. The red curve that describes Bob's distance from the black hole center is a continuous function, meaning it is nice and smooth everywhere. In fact, we can see that Bob takes only about five units of time to reach the center of the black hole. In other words, he sees nothing unphysical and passes easily and happily directly into oblivion at the center of the black hole. There are no stable circular orbits within 3 unit distances from the hole, so anything that passes this limit is forced to occupy an orbit either moving toward or away from the black hole. So Bob could not avoid falling in by travelling in a circular path around the black hole. No such orbits exist. His trip into the black hole takes a finite amount of proper time which he could measure from his wrist watch as he fell in. Nothing strange or unphysical happens according to Bob as he approaches the center of the black hole (the left of the diagram). I say that with some grains of salt added. Actually, as DPS pointed out, the difference in gravity between Bob's head and feet become greater than the tensile strength of known materials somewhere to the left of the event horizon at r=2. So Bob is spaghettified at some point before he reaches the left
of the figure. But his atoms, at least, continue on to oblivion on the left hand side of the figure. And according to them, the proper time they would experience would behave no differently than it did on the outside in less hostile environments for squishy astronauts.

On the other hand, Alice sees Bob move according to the blue curve, not the red one. This curve does appear to behave strangely as Bob approaches the event horizon. The blue curve actually has an asymptote, which is the event horizon itself. This means that it never crosses r=2, and can only get closer and closer as time goes on. This is what gives the behavior that DPS mentioned. Alice will see Bob taking a lot longer to approach the event horizon than Bob does according to his own watch. He will never reach it. Time will just appear to move slower and slower for him and his image will slowly fade from visible to microwave to radio and further on to undetectability as the light rays leaving him are redshifted by a more extreme amount.

For this reason, the event horizon singularity is not a real singularity, it's a different kind of thing called a coordinate singularity. It's like a map the Earth that has two poles on it that are singular in the lattitude and longitude system. At the north or south pole, the longitude coordinate becomes undefined. Only the lattitude there has any real meaning (ie, + or - 90 degrees depending on North or South). So the Earth's poles are singularities. But this doesn't mean there is anything physical actually going on there on the surface of the Earth itself, the north and south poles are like anywhere else on Earth and nothing strange with geometry really happens there. They are only singular coordinates on a map of the Earth and not on the actual Earth itself. An observer far from a black hole is like this too, when they are trying to describe what happens to someone falling into the black hole it's like they're trying to describe the Earth's surface from looking at a map. The description from the guy actually falling into the black hole is like you're describing the north pole by actually going to that spot on Earth and examining the physical location: there is just nothing singular about it.

So there is a way around the strange coordinate behavior at the event horizon: just pick a different coordinate system to make all your measurements relative to, one that does not have such problematic behavior from the coordinates and the problem goes away. For the Schwarzschild black hole coordinates which remain finite everywhere except r=0 are Eddington-Finkelstein coordinates or Kruskal coordinate systems. Then the event horizon doesn't look like anything special at all but just like using Cartesian coordinates in place of lattitude and longitude, all of the mathematics and work you have to do in that coordinate system become really complicated. This is why the curvature at the event horizon is finite - because it is not a physical singularity and is only a coordinate singularity. If you want to find a real physical singularity, just think about the center of the black hole at r=0. You can never transform this singularity away because it is a real area where something strange happens, curvature (and therefore the gravitational field) become infinite. No amount of coordinate system wrangling can avoid that, which is why astrophysicists are consistently scratching their heads over questions of what happens at the center.

/end text wall

Good call on Blade, I forgot all about that opening scene. The bloody sprinkler system was a nice touch for a vampire rave.

Another callback to Bruce, the infamous shootout from The Crow that cost Brandon Lee his life

http://youtu.be/Bi8obKLsc9A

I watched Blue Sunshine on someone's suggestion. Weird movie.

Quote from: onan on October 18, 2014, 12:53:53 PM
I bought solar eclipse glasses for everyone on my team... only to find out after the purchase... the sun sets in NC just as the eclipse is getting started... Yay me!

Awwww dammit. Road trip!

Barring that, I hope you kept the receipts

because George Noory sucks.

I wasn't able to watch the Bad Boys scene but Billy Jack sure did some face kicking, all right.

Let's get more fight scenes up here!


http://youtu.be/sEnL3ukPauM

Quote from: Kelt on October 18, 2014, 08:21:01 AM
Pacific Rim was dumber than shit.  One dimensional characters, a plot thinner than Debbie Does Dallas, and an insult to the intelligence of anyone who has two brain cells banging together inside their skull.

However... if you go into this movie knowing it's NOT Shakespeare, but rather giant robots smashing the shit out of giant monsters, accompanied by some of the most glorious CGI you've yet seen, then Pacific Rim is everything you could hope for.  My kid loved it.

Yeah, all of that sounds alright to me. Just looking at the poster and trailers kind of made me expect these things to be selling points and not stuff I can really criticize.

Quote from: area51drone on October 18, 2014, 02:24:13 AM
I was just joking with you, of course.  I hope your family member gets better.

For sure man. Thanks for the well-wishes.

Quote from: area51drone on October 18, 2014, 12:21:47 AM
AO has more time these days, it appears.   How about going back and answering some of the questions we had for you?   (AO slinkers back behind his comet)   

Actually been going through some pretty intense stuff lately besides work. One of my close family members is sick. But I have been slowly accumulating some thoughts about previous posts in a rant-filled text file that I can eventually drop in here.

Quote from: Camazotz Automat on October 18, 2014, 12:37:08 AM
Anytime I suspect I've been subjected to mind control recruitment propaganda, I have an absolutely decadent Mexican dinner with Stella Egyptian beer while re-watching They Live (1988).

I'm here to kick ass  ...  and chew bubble gum ...

Presto! Change-O! Cleaned neural axons!

[attachimg=1]

Along with the best fight scene of all time.

"Put these glasses on."
"FUCK. YOU."

Quote from: Camazotz Automat on October 18, 2014, 12:01:40 AM
I am my own pharmacy. (so that's an automatic 'yes'. heh.)

I'm viewing the new Godzilla next week. I hope they didn't show the best parts in the ads.

I am surprised at how often I am grateful I didn't waste the time or money to see something when it was playing in the theater.

Prince of Darkness is a movie that has the feeling of high school embedded in it. Watching it any kind of sober is just... wrong.

Godzilla was pretty unremarkable. I'm going to try Pacific Rim next, which I heard was pretty okay. To stay on the theme of giant monsters fighting other giant stuff.
Some of the army stuff in Godzilla really felt like a recruitment add, I got the same thing from Man of Steel which I think explicitly had a recruitment tie in. Blech.

Quote from: Camazotz Automat on October 17, 2014, 11:54:47 PM
Prince of Darkness  (1987)

Awesome movie. I hope you were on drugs.

Watched the recent Godzilla film tonight.

Meh.

Quote from: wr250 on October 17, 2014, 09:17:21 AM
np
as an aside , i have 2 welders masks (well 3, but one was at work so unavailible) . so about an hour before the eclipse, i went to the neighbors and told them "theres an total eclipse starting in an hour, i have a couple of welders masks do you and your kids want to see it?"
and sure enough about 10 kids and 5 or so adults were all taking turns with the masks, and the  kids made a pinhole projector out of 2 pieces of white paper.  1 kid brought out a telescope, i told them to take it back int he house, because that will make you blind by burning your eyes. yes i know it could be projected onto a wall or something, but some of the kids were 2 and 3 so didnt want to take any chances.

That's awesome!!
Love it when kids like that can get engaged with this stuff.

Quote from: wr250 on October 16, 2014, 08:42:10 AM
isnt there a way to take the energy from the fusion reaction and directly turn it into say electricity , rather than use the reactions heat to boil water to drive turbines to make electricity , as we do now in nearly all electrical generation?
nuclear power plants, coal, natural gas, and dams all depend on water to make electricity. it seems rather inefficient (with the dams being more efficient than the rest).

The simplest way to get an AC current has a magnet act as a rotor that turns within the coils of a conducting wire. This requires mechanical energy as input to turn the rotor and induces an alternating current in the wire, converting mechanical energy to electrical energy. To scale this up, replace the rotor with a turbine (which converts the energy of motion of a fluid to mechanical energy) and then hook that up with a generator to convert mechanical energy into electricity. As long as you can keep the rotor turning (or turbine blades spinning) you generate a current. This is usually done with steam or water (hydro). Despite the large number of steps, the efficiencies of these conversion processes are pretty good, which is why this method is so widely used.

You can convert thermal energy to electrical energy directly using a device called a thermocouple. This is basically two pieces of different kinds of metals stuck together, and a temperature difference across them will cause a voltage to flow. This is called the Seebeck effect. It is not very efficient but can also be used as a generator (http://en.wikipedia.org/wiki/Thermoelectric_generator).

Quote from: wr250 on October 17, 2014, 05:54:11 AM
here are some i took of a "ring of fire" eclipse through a welders mask :

Quote from: zeebo on October 17, 2014, 02:32:24 AM
As some inspiration to check it out, here's a pic I took of mini sun crescents filtering through some leaves, seen amongst shadows cast on a wall.  This was from the May 2012 total eclipse.  I had remembered seeing this effect during an eclipse I saw as a kid, but thought maybe I'd imagined it, so this time I took some pics so I'd have proof.

Wow these are really cool. Thanks for sharing them.

Quote from: area51drone on October 17, 2014, 06:47:22 AM
We should have some meetups for those of us in this thread in August 2017.  I plan on heading to Oregon that day...

http://www.eclipse2017.org/2017/path_through_the_US.htm

Actually not a bad idea, I definitely plan on heading south to view the eclipse.