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The new blend, basically glass riddled with holes, can be made into thick films and does not shrink -- problems inherent in previous materials for holographic data storage.

This is a very interesting technology, and it seems like some type of three dimensional optical storage would enable a storage capacity one or twe magnitudes larger than the ones used today.

It is usually said that glass is a liquid, and flows slowly, as seen in old church windows that are thicker at the bottom edge.
However, a bit of googling seems to suggest that glass flowing over time is an urban legend (church windows apparently just had an imperfect manufacturing process, and were installed thick edge down). Whether to call glass a liquid or solid seems to be a toughter question.

But aside from flowing, is there something else about glass that could make it unsuitable for longtime information storage?

>Special relativity applies only to inertial frames

No. The POSTULATES of Special Relativity apply only to inertial frames. But these postulates allow you to DERIVE results for accelerated frames, provided that spacetime is flat in the region under consideration.

And no, gravity and acceleration are not the same thing. They are *locally* indistinguishable, meaning only in small regions of spacetime. In an accelerated coordinate system, the pseudo-gravitational field lines are all parallel. In real gravitational fields, they radiate out of the mass source.

You're simply wrong about special relativity not working for an accelerated frame of reference. Granted, the POSTULATES don't apply, and therefore accelerated frames cannot be treated as simply as inertial frames, but accelerated frames *can* be handled using Special Relativity and calculus to integrate over the continuum of inertial frames in the worldline of an accelerated object.

For further details, please see the Usenet Relativity FAQ here . Note specifically the question about whether SR can handle accelerated frames

Hope this helps.

Christopher R. Volpe

>Special relativity applies only to inertial frames

No. The POSTULATES of Special Relativity apply only to inertial frames. But these postulates allow you to DERIVE results for accelerated frames, provided that spacetime is flat in the region under consideration.

And no, gravity and acceleration are not the same thing. They are *locally* indistinguishable, meaning only in small regions of spacetime. In an accelerated coordinate system, the pseudo-gravitational field lines are all parallel. In real gravitational fields, they radiate out of the mass source.

You're simply wrong about special relativity not working for an accelerated frame of reference. Granted, the POSTULATES don't apply, and therefore accelerated frames cannot be treated as simply as inertial frames, but accelerated frames *can* be handled using Special Relativity and calculus to integrate over the continuum of inertial frames in the worldline of an accelerated object.

For further details, please see the Usenet Relativity FAQ here . Note specifically the question about whether SR can handle accelerated frames

Hope this helps.

Christopher R. Volpe

If I remember my general relativity, to an observer at rest matter falling into a black hole will seem to take an infinite time to pass the event horizon.

It's the one who needs more time (the observer falling in the black hole) who will experience becoming a very curved and very thin pancake in a finite amount of time.

I suggest everyone interested to go read John Baez's GR Tutorial

No, unfortunately it seems that we are both wrong. Here is an explanation.

I think that should be John Baez.

This is all horribly wrong. Please check out the Relativity FAQ. Particularly The EPR Paradox and Bell's Inequality and Does Gravity Travel at the Speed of Light?

This is all horribly wrong. Please check out the Relativity FAQ. Particularly The EPR Paradox and Bell's Inequality and Does Gravity Travel at the Speed of Light?

This is all horribly wrong. Please check out the Relativity FAQ. Particularly The EPR Paradox and Bell's Inequality and Does Gravity Travel at the Speed of Light?

Well, it's doesn't work that way. :)

Read this

5. Do black holes really exist? (It sure seems like it.) Do they really radiate energy and evaporate the way Hawking predicts? If so, what happens when, after a finite amount of time, they radiate completely away? What's left? Do black holes really violate all conservation laws except conservation of energy, momentum, angular momentum and electric charge? What happens to the information contained in an object that falls into a black hole? Is it lost when the black hole evaporates? Does this require a modification of quantum mechanics?

1. How do the black holes form? (i.e. Where do babies come from? ;-)

A normal "burning" star is in a state of balance of two forces: 1) the star's gravity, which wants to make it smaller, and 2) the pressure from the nuclear reactions inside which make it want to blow up. Stars eventually run out of fuel; that is, they run out of hydrogen in the core, and start burning helium, and then other elements until eventually you get a bunch of iron. You can't get any more energy out of fusing iron. In fact, it *takes* energy to do it. The pressure from the nuclear reactions drops, gravity wins, and the star collapses. Small stars like the sun become white dwarfs, larger stars become neutron stars, and even larger stars become black holes.

2. Once a black hole is formed, it sucks all nearby matter in. Will it keep growing indefinitely or will it somehow stop at some point?

As long as there is matter around, it should keep growing. Mind you, we think black holes 'evaporate' eventually (Hawking radiation), but it is a very slow process for large black holes.

3. What exactly is meant by the size of the black hole? You can't just go there and measure its size. Heck, you can't even see it. You can only infer its mass by looking at the effects on nearby objects. Right? So what's this talk about small/big black holes?

Usually they are talking about mass, but you can also talk about the radius of the event horizon. The event horizon is the distance you can be from the center of the black hole before you get stuck. As long as you are outside the event horizon, you can still get away (given a big enough rocket :)). The more massive the black hole, the larger the event horizon.

4. (I totally don't get this). When something is being sucked into a black hole it starts accelerating due to the gravitational pull of the black hole. At some point the speed of the sucking object (did I just invent this term? ;-) will approach the speed of light, at which point the time is supposed to slow down...

Well, no. If you throw a ball into the air, it doesn't reach infinite velocity before it reaches the ground, does it? Falling toward a black hole is no different than falling toward anything else with mass. That's not saying that there aren't some odd effects. If someone was watching you fall into a black hole, they would see you move slower and slower as you approached the event horizon, but you would never actually cross it. From your point of view, everything looks normal (apart from being ripped apart by tidal forces) and you cross the event horizon and land on the singularity in a finite amount of time.

There's some good stuff in the black hole section of the Usenet Relativity FAQ

Because you may well be mistaken about what is incorrect and what is just a different notation. Take a look at a random decent reference for a second and scroll down to momentum.

You will see that if you call the mass of the object its rest mass, then you need a relativistic correction term. If you call the mass of the object its total mass including the mass of its kinetic energy, Newton's formulation still holds.

It is entirely a question of definition. Here is a random argument for defining the mass one way. OTOH my background is in math. I learned physics from older texts, and from the point of view of a mathematician the concept of relativistic mass is a lot cleaner than carrying around the correction term.

Now when I am explicit about saying that I am using the word mass to mean mass with the relativistic correction (ie with the mass of the kinetic energy counted as mass), what I said becomes both unambiguous and clearly correct.

I can also point out that from the point of view of a purist it is cleaner to think that way. For instance a fraction of your mass is the mass of the heat of your body, which is just kinetic energy. Likewise a fraction of the mass of the Solar System is from the motion of the planets around the Sun. To me the mass of a system of objects should just be the sum of their masses. Using relativistic masses that is true. Using rest masses it doesn't quite add up.

Regards,
Ben

I sorted out my confusion on this FAQ web site.

I made it a few pages down the FAQ, and I'm afraid I have to say that it's one of the worst that I've ever seen. The author's argument seems to amount to "Well, you can describe the universe mathematically using four dimensions, but because I only see three of them this is purely bunk.".

At this point, I stopped reading.

In point of fact, if you want to see the effects of space being four-dimensional, you need only look at two reference that are moving quickly with respect to each other. The time and space directions measured by observers in each frame are different - this is the Lorentz transform (if I remember the term correctly). Space in one frame corresponds to a skewed space-and-time axis in another frame.

This has been verified experimentally by very careful measurements of atomic clocks moving at different speeds with respect to each other. A more dramatic illustration is measuring the decay times of unstable particles moving at different speeds. As they approach the speed of light, the lifetime as measured by the observer gets longer. This is called "time dilation", and is one of many effects caused by the "time" and "space" axes not being the same for observers moving with respect to each other.

You can find a very good FAQ on relativity here:
http://math.ucr.edu/home/baez /physics/relativity.html

This links to a FAQ on general physics, and many other FAQs that may be of interest.

ReqNG:

• is GPL
• is written mostly in Perl
• captures email between tech support and users
• keeps data in text files
• has tcl/tk (TkReq) and web (WWWReq) interfaces

I created my own HTML forms to generate formatted email input and some perl scripts to generate weekly reports. ReqNG has it's own summary report that's suitable for distributing via email.

ReqNG http://reqng.sycore.net/reqng/
TkReq http://www.cs.wisc.edu/~jmelski/tkreq/
WWWReq http://www.cs.ucr.edu/~cvarner/wwwreq/

"Tyranny, like hell, is not easily conquered; yet we have this consolation with us, that the harder the conflict, the more glorious the triumph. What we obtain too cheap, we esteem too lightly: it is dearness only that gives every thing its value. Heaven knows how to put a proper price upon its goods; and it would be strange indeed if so celestial an article as FREEDOM should not be highly rated." -- The American Crisis (1780) by Thomas Paine

A good reference is the Usenet Physics Faq which says: 'It has been shown by Eberhard that no information can be passed using this effect so there is no FTL communication' on this page.

Its easy to come up with ideas but unfortunately quantum mechanics has a way of screwing things up when you try and cheat :)

Don't worry...from the looks of things you're way ahead most of the posters today...

If you want to check out a really good, credible source of physics information on the net, I suggest the Usenet Physics FAQ if you just can't be bothered to pick up a textbook.

Both questions of yours are really close to a general question known as the Twin Paradox. Basically, who's clock moves slower (or who's actually ageing slower)? The incredibly short answer is that time in the train's frame of reference, for the period that it moves at a relativistic speed compared to you, travels slower compared to time in your frame. In other words, after you accelerate (or the train slows down) for you to compare, your clock will be ahead.

The answer to your second question lies in the fact that the spacetimes of the two ships are fundamentally different from each other. 0.75c is a measurement of speed in your reference, and not the other spaceship's. Therefore, at relativistic speeds, vectors don't add normally. The other spaceship moving towards you is going 0.96c in your frame of reference. (Work out v =((v1-v2)/(1-(v1v2/c^2))) where v1 = 0.75c, and v2 = -0.75c.)

Enough rambling...the FAQ should answer any other questions you or anybody else might have.

telnet://bbs.ufies.org
Trade Wars Lives


telnet://bbs.ufies.org
Trade Wars Lives

There seems to be a lot of people arguing whether or not a photon can have mass. It seems that a lot of these arguments are just differences in semantics.
Here is a good link from the Relativity FAQ which may clear up some of these issues.

There seems to be a lot of people arguing whether or not a photon can have mass. It seems that a lot of these arguments are just differences in semantics.
Here is a good link from the Relativity FAQ which may clear up some of these issues.

The Crackpot Index (http://math.ucr.edu/home/baez/crackpot.html)
A simple method for rating potentially revolutionary contributions to physics.

actually, it's a good thing they're doing this.

i don't know if you remember the dying days of TSR before they were bought by WotC, but they claimed that *anything* created for use with AD&D was a derivative work, and as such, they had copyright on it. anything which used thier terminology (Dungeon Master, Hit Points, etc) was fair game.

the upshot is that they shut down most of the D&D archives on the web, and tried to have everything served off of one ftp site (i think it was ftp.mpgn.com....) and pretty much ended up alienating most of thier fans.

this (to me, anyway) just looks like a promise that, even though they've resolved the issue with AD&D 2nd Ed., that they can't do something this under 3rd ed.

here's a good account of the times.

note that this was TSR that did this - this happened before they were bought out by WotC, and has been completely resolved under WotC's management.

Everyone should read the Pysics FAQ

From the conclusion of the "Liquid Glass" Section:

In any case, claims that glass in old windows have deformed due to glass flow have never been substantiated. Examples of Roman glassware and calculations based on measurements of glass visco-properties indicate that they cannot be true. The observed features are more easily explained as a result of the imperfect methods used to make glass window panes before the float glass process was invented.

What the article at the URL you posted describes is apparent motion as measured by an observer from a third frame of reference. See the paragraph with the heading of "The moon revolves round my head faster than light!"

We are measuring the distance between us and a very distant quasar so the case of special relativity you mention actually does not apply.

--

Question: Does my bathtub drain differently depending on whether I live in the northern or southern hemisphere?

Answer: No. There is a real effect, but it is far too small to be relevant when you pull the plug in your bathtub.

You can use a crystal to create a twin of a photon which will always have the same properties (for example spin or polarisation) as the original photon no matter the distance between them (quantum theory predicts this effect and it has been proven that it exists. The photon teleportation uses it, for example). Now the idea is like this: You create these twins in Paris and send them via fiber to New York and Moskau. In Moskau, I use a filter to polarise my photon and in New York, the polarisation is measured. This doesn't work but why not ?

You can find more information about the EPR paradox and Bell's inequality in the physics FAQ, or by doing a search on the keywords "Bell's Inequality" and "EPR paradox".

-r

Here is a link to the "Art of Assmbler" :-) It's really a good read.

If you want to know *why* ASM is good, go to the homepage of the DGen/SDL project, a genesis emulator for Linux. It uses an ASM memcpy function (using either MMX or "native" mode) as well as an ASM 68k and Z80 CPU core. By doing this, it makes the emulator /much/ faster, and a lot more useable. I'm sure other famous emulators (like GeneCyst, etc) use ASM CPU cores at some point, as it's pretty hard to emulate well without. I'm not even going to go into the ASM wizardry John Carmack did for Wolfenstein, Doom, Quake, etc :-)
---

http://webster.cs.uc r.edu/Page_asm/ArtofAssembly/ArtofAsm.html
Citrix

THE CRACKPOT INDEX (see #7)

Poor Mr. Mills quickly racks up the points.

After reading his claims that his work is ``past the scientific verification stage'' while it won't be until January that he ``will submit [his] findings to a premier [yet unamed] scholarly journal'' it makes me wonder how carefully he paid attention when he was attending Harvard and MIT (if he actually did). Peer review is at the heart of scientific verification.

Mr. Mills: just what grade did you get in your physics class?

That's the weirdest computer programming article I've read in a long time!!! http://webster.cs.ucr.edu/ratc/ratc.html.

• TreadMarks
• The Quarks DSM System (ports to other platforms are here and my port to Linux is here.)
• DIPC (or try here)
• SHRIMP, a high performance parallel system for Linux.
• PVM -- a message passing approach to parallel programming.

Here's a usenet relativity FAQ if your interested in some info.
Here's some info on black holes too, while I'm at it.

Here's a usenet relativity FAQ if your interested in some info.
Here's some info on black holes too, while I'm at it.

Maybe most people dont get a kick out of it, but I personally see it as one of the better parts I've seen of AntiOnline/AntiCode.. Redhat 5.2 ftpd exploit? I could really care less, putting that up only adds to the amount of clueless kids running around there attacking anyone they can, including dialup users. However, The Virii archives seem to add a bit of history to it. I've spent hours before browsing through, looking at some of the more historical Virii that raped newspaper headlines. At work one time half the computers around had gotten a virus that the antivirus said couldn't be removed; I check the archives, analyzed it (which is VERY fun if you know assembly.. (Tutorial). I dont see many people actually going out and compiling them, so just consider them to be historical documentation like text files.

hot water freezes faster [than does cold]

Forgive me for a minor degree of pedantry, but I believe that it may be incorrect to assert that high school science books err when they teach that "hot water freezes faster than does cold". The following URL may prove to be of interest: http://math.ucr.edu/home/baez/ physics/hot_water.html.

For where former Mach people are, see Former Mach Project Members.

Microsoft themselves publicize Rashid's arrival

The Casimir Effect, basically (and don't flame me if I'm wrong! Just post a correction.. ;) consists of two electrically neutral plates placed VERY closely together. So closely together that the distance between them is smaller than the wavelength of some virtual particles. Because there are fewer virtual particles between the plates than outside, the energy density is LESS than the vacuum energy density -- negative energy? Not in large amounts, but a clue as to where to find the stuff, perhaps...

-g.

The Casimir Effect, basically (and don't flame me if I'm wrong! Just post a correction.. ;) consists of two electrically neutral plates placed VERY closely together. So closely together that the distance between them is smaller than the wavelength of some virtual particles. Because there are fewer virtual particles between the plates than outside, the energy density is LESS than the vacuum energy density -- negative energy? Not in large amounts, but a clue as to where to find the stuff, perhaps...

-g.