Royston

True, but I am not talking about losing a sock, I am talking about explaining why socks are lost.

I had a quick look on google earth, and the socks are floating just off the coast of Iceland. I have no idea how they got there, or by what means (on the backs of turtles?) in any case, they are there for the taking !

Could gravity be as relative as light

Stop, what do you mean by this ?

and thus could a black hole be "gravity-dilated" due to relative velocity/gravity?

What ?

Why does GR assume relative spacetime and absolute gravitational relations? Is that too abstract a question for this thread?

Not so much abstract, more failing massively to ask coherent questions about GR.

The problem is very similar to that in quantum gravity.

No it isn't, quantum gravity is incredibly complicated....loosing socks is incredibly easy. Anyone in there right mind can loose a sock, but it takes years of dedication to come even close to slightly understanding QG. If genius was based on sock loss, then I am clearly a whopping genius, which I'm not !

Oops, I meant line integral.

Hmm?

IOW, you define the space before you imbed (for want of a better word) the Lorentz transformations, for instance you could start with Cartesian spherical coordinates [math]x^2 + y^2 + z^2 = c^2[/math] expanding the transformations when the space is already defined (and the fact there's nothing physical about doing so) doesn't make much sense. Albeit, you've decided not to go down this route.

Does anyone know where I might be able to find a general boost formula like this one written in spherical coordinates (ct,r,phi,theta)?

I really don't feel like expanding it all myself.

Lorentz transformations only make sense in local non-curved spacetime (i.e Euclidean), they are infintesimal sections on a manifold, where SR holds (part of the Lorentz group). It would make no physical sense to expand this set of linear equations into spherical coordinates...you really should start with a line element or path integral, then build a metric from that.

If the universe is finite, then it is not sphere, or any other 3D shape.

Sorry Sisyphus, but this is wrong, a finite Universe is simply static, you can use a spherical metric to describe a finite Universe....(plus (and I know you know this) a sphere is 2D, perhaps you're referring to a 3 sphere, but I don't see the relevance)

There is no telling if the universe is infinite or finite beyond the observable universe.

The topology of the Universe is around the Hubble volume, i.e there maybe clues to a wrap-around by probing the CMB, (there are no hints of a complex topology, so it's at or around the Hubble volume) so I have no idea what you mean by this.

There is no telling, nor will there ever be, what existed prior to the Big Bang, because it obliterated all traces of what pre-existed it.

Source please.

Our Big Bang (as distinct from other possible BBs consistent with the Type I Parallel Universe theory) created our region of space-time. Space existed prior to the BB. With the introduction of matter, space became space-time. This is not based upon evidence, only on logic.

What do you mean by 'our' big bang, the rest appears to be unmitigated tripe.

err, anyway...

Exactly and if ydoaPs continues with his infantile ravings on this point I shall go ballistic.

A little bit rich considering your language and feet stamping. It's disappointing that even from seasoned members of these boards, a level of maturity is severely lacking when it comes to this subject. I cannot see anything wrong in trying to strictly define your beliefs, (I think ydoaPs has done a sterling job personally) and agnosticism is atheistic...there is no difference in taking the stance of 'not knowing', as there is in 'there is no available evidence.'

Further, Ignosticism is a statement on a set of all theistic beliefs, i.e it's an observation on subjectivity, not a belief in it's own right. So, just because you can't decide which belief is or is not correct, doesn't categorize you into theism or atheism, so you can't bolt it on, despite the subject it encompasses, happy to expand on that point if it's not clear.

Personally I find the idea of creation (which may or may not be ascribed to Godhood) not only absurd, but damaging. If you wish to further your knowledge and believe in creation, then it's a case of shifting the goal posts to accommodate new knowledge, which is logically fallacious. If God is conceived as completely overarching, i.e whatever you throw at the concept, it remains intact, then it's a meaningless concept. If we discover something that fits a preconceived notion of God, then that discovery is shifted into that notion, it's not shifted into a body of study. I find the idea stifling, and unnecessary personally, but perhaps that's me getting old and less tolerant.

EDIT: The above is a happy diversion from my cosmology coursework, which is driving me suitably insane

Are the rotation curves for the galaxies different for the galaxies near the centers of the cluster compared to the galaxies farther from the cluster center?

 

Are there measurements that give the rotation curves for galaxy clusters?

 

Since the effect of Compton scattering is so tiny, do we currently have the sensitivity and resolution at these low frequencies for the SZ effect to give accurate measurements of the clusters? Can the SZ effect determine a rotation curve for the galaxy clusters?

 

What does the information that we have now from star, galaxy, and black hole formation tell us about the cluster structure and evolution of the clusters? What physical mechanisms affect the structure and dynamics of galaxy clusters?

 

Does anyone have any links to (free full text) peer reviewed articles?

 

Thanks!

First, there are two types of SZ effect, thermal is used for distance measurements whereas kinetic deals with bulk motion relative to the cosmic rest frame, so the latter, despite being weak, would give some information on rotation. Cluster rotation is very complicated, although they do rotate (to an extent.) There is generally an accretor, where we're concerned this is M31, however the Milky Way also acts as an accretor. There are star trails where our most closest galactic neighbours are spiralling in towards the Milky Way, and we in turn, are spiraling towards M31 (I'm using the term spiraling loosely BTW, huge distances and timescales et.c). The SZ effect will be used in the next gen of CMB maps, so it's early days.

As for clumping and cluster structure, the general clumping of DM (in the early Universe) is outweighed by young galaxies and their DM halos (see Quasar distribution), I guess that stands to reason where gravity is involved, but I may be missing something. I realize this is a late reply, but I covered the SZ effect recently, so thought I'd add my, albeit, basic knowledge on the subject.

Typo of the day...

However, thinking about blackbody radiation, I'm also curious as to whether or not heating it up with hundreds of billions of watts of electricity would also cause it to emit UV light, or X-ray light... or even gamma gays. How likely would that be to happen?

Found in the Ultra Pink region of the EM spectrum.

But we seem to be allowed to put in our own custom titles now with the new SFN, in Profile under Member Title.

I can't seem to find this, although I'm no longer Snail anymore. My new username has nothing to do with 'The League of Gentleman', if anyone asks or cares.

For windows updates I let it do those automatically, as for GPU & Mobo updates (Which i've not done in a little while) I usually visit http://www.nvidia.com/Download/index.aspx?lang=en-us and use option 2.

 

I'm concerned that the random freezes are not related to the driver issue and have read that this could be related to heat. AI Suite says my internals are never reaching above 65 C though and would have expected this to be a reasonable temperature.

 

Like I said, i'm not a techie so I didnt really see the need to post HDD specs assuming it was just a storage medium and didnt really affect anythign in a significant manner - HD1 = 300GB HD2 = WD Raptor 10,000 RPM with 60gb space ( I generally dont use this much)

The only reason I asked is more storage, generally means more power consumption, so I think we can rule that one out.

Here's a way to create dump files, that you can send to microsoft support...dump files

If you're system is not overheating, the random freezing could just be a driver conflict, you may have something lurking that's causing problems. You could try driver sweeper...Driver Sweeper reboot in safe mode (with internet access) and get everything you need, and reinstall your drivers. But your first port of call really should be with ms support, with your dump files. If they can't find anything, then at least the possibilities of the problem have been narrowed down.

Is it possible that windows updates can interfere with the stability of your machine?

 

Recently my computer has been experiencing random freezes (ctrl, Alt + Delete doesnt work and there is no cursor movement, basically no access to the system at all and forces me to shut down the computer manually) I also experience BSoD "Driver Power state failure" but only when my computer has been on for some time AND only when I run the shutdown sequence.

 

The Machine will show the "shutting down" screen for about 15-20 minutes then go BSOD and reset itself - once the OS has loaded again a subsequent shutdown will happen almost immediately (about 10 secs) after i've told it to do so.

 

Since this problem has begun occuring i've run a full system defragmentation, registry cleaner, virus scan and cleared temporary files. I've even run a version of Memtest 86 incase it was a RAM problem - though i'm not sure how accurate this was because my machine is a dual core and i dont think it's 100% designed for that and opened her up to scrape all the gunk out of the fans.

 

Before I go last resort and do a format of the machine I came up with the idea that this may be a problem with recent updates and patches that windows automagically installs rather than a hardware issue ( I really hope it isnt cause i'm not all that tech savvy and wouldnt know how and what to replace)

 

Do you IT guys reckon I could fix this problem with a rollback to the patches?

 

Asus Striker II Formula MoBo

1010 Watt PSU

2 Nvidia GTX280 in SLI

As the name suggests, it's likely to be a driver problem. How do you update your drivers ? If you let windows do it for you, where you've previously downloaded from a website (especially for display adapters) you'll run into problems. You're probably better off sending your dump files to microsoft support, who'll be able to locate the source of the problem. You've got a new system, with ample power, although you didn't give us your hdd details (unlikely it's a power issue though) and you've checked your ram...so it's probably not a hardware issue. I'm quite envious of your set up btw

Thanks, I did post there. And I'll gladly wait.

You'll be much better off asking here...Maya programming forum or somewhere similar. I'm pretty sure, but don't quote me on this, but most studios use a platform e.g 3ds Max, and design their own plug-ins depending on what they want. IIRC Pixar use Maya, along with a host of other packages such as Marionette. I doubt you'll get much help on a science / physics forum.

Wait... how can this be the biggest? Isn't Canis Majoris supposed to be around 2000 times the size of the sun?

 

- Robert

I think you're referring to the radius, not the mass. However, we can do a quick calculation to get an approximate value for the radius of this beast...

[math]L \approx 4\pi R^2 \sigma T^4[/math] so...

[math]R \approx \sqrt\frac{L}{4\pi \sigma T^4}[/math]

[math]R = \sqrt \frac{3.84 \times 10^{33} W}{4 \pi \times (5.67 \times 10^{-8} W m^{-2} K^{-4}) \times (4.0 \times 10^4 K)^4}[/math] = [math]4.055 \times 10^{10} m[/math]

Apart from the scale (the radius will be huge when it reaches it's red hypergiant stage), I'm more interested in how it's formed, and unfortunately my astronomy module doesn't go into enough detail on cloud fragments for exceptional cases like this...so I'll have a look around. Also, I wasn't aware that at very high masses, the resulting supernova will not leave a stellar remnant, in this case you'd think it would form a BH. It's lifetime as a main sequence star is very short indeed, so this is quite the find.

EDIT: Sisyphus replied while I was posting.

This is the best overview of what tensors actually 'are' that I've found...

http://www.grc.nasa.gov/WWW/k-12/Numbers/Math/documents/Tensors_TM2002211716.pdf

Carroll's lecture notes are hardly an introduction to tensors. GR is one application of tensors, there's many more basic examples that require tensors.

Seems like little is sure about them at the moment...

True, the evidence for neutron stars is very indirect, so it's more of an observational issue.

However there is a wealth of information you can grab from light curves, and it's a case of back tracking i.e we have available solar models (a culmination of observation, lab experiments and maths) and the emission detected from these bodies. So certain systems will give a distinctive light curve, which agree with current models. There's always exceptions of course.

Has anyone heard anything about the theorized life cycle of a neutron star?

Well, being a stellar remnant and due to the longevity of stellar objects, trying to pin down the death of a neutron star is very hard. I can expand on that if you want.

I wonder if at the end of a neutron star's life there is a chance for a black hole to form

Binary systems are common, so for a neutron star with a high mass donor (the donor being a higher mass orbiting star) i.e the neutron star is gaining mass due to the donor overfilling it's Roche lobe, it could in principle, gain enough mass to form a black hole, depending on the stability of the system. Any terms you're not sure of, just google or ask.

From Dexter...

'Science is one cold hearted bitch with a 14 inch strap-on'

BTW, guys, I don't mind taking the ideas and making images...

Break a leg, perhaps we could merge the above with 'It's too big for my genes!' (titter)

So sorry to hear that Paranoia, for what it's worth, I'd feel exactly the same way if my beloved studio equipment was stolen, albeit it will be a bit more drawn out than just shooting them

I think I've found your next purchase, hopefully it'll put a smile on your face...

http://www.smithsonianmag.com/travel/Colombia-Dispatch-7-Turning-Guns-into-Guitars.html

Sorry, that's not how I took it. But I'll hush now.

I appreciate the fact you took the time to reply to someone, who can't read a sentence correctly.

Perhaps I'm just confused

Immortality was bolted on by Paranoia, the initial argument from his son was 'what's the point.'

He wasn't talking about immortality, he was wondering what difference it makes 'ultimately', if he was alive or dead. Which entirely depends on the person asking the question.

It's quite simple, if I'm dead there's no room for something good happening...it's impossible to make a change if you're inanimate, change could lead to something good, (depending on what your Son considers good).

It's a little tricky fitting an AGN into your garage.

Just to echo IA and Severian, but what a complete mess of an election.

I naively thought, that 'this time', we had a three party system, obviously not. I promised myself I would leave the country if the Tories won the most seats, so possibly looking forward to booking my visa once my degree is finished i.e if I can finish it, funding has already stifled my Uni, (which I won't get into right now) but funding for science under a conservative government, is enough to bunk the country on it's own.

If there's anything to perpetuate the political apathy in the UK, it's a shoddy election.

Even in the UK?

My mate Dave managed to remove his underpants whilst his trousers are still up...there's no excuse.

EDIT: I don't actually have a mate Dave, but I distinctly remember a girl managing to do it, when I was on holiday. Albeit her knickers were a long saggy mess after completing the feat. Congratulations.