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College campuses make good alien/futuristic cities. When I was attending UC Riverside, Gene Roddenberry came and turned the campus into the stronghold of the 22nd-century mutant warlords. Which really doesn't say anything nice about the architecture....

"When it comes to black holes, you'd be better off asking someone who does gravity, or astrophysics. What do quantum mechanics know about black holes?"
Actually, no one knows about (the interior of) "black holes". For example, Hawking radiation depends on quantum mechanics and very intense gravity outside the event horizon (which sucks one of the virtual particles back into the "black hole"). (Note: This explaination of Hawking radiation may be completely wrong.) Quantum mechanics plays a huge role in this new theory and in Hawking radiation. By the way, did you read the article? For example:
Quantum transitions

However, as long ago as 1975 quantum physicists argued that strange things do happen at an event horizon: matter governed by quantum laws becomes hypersensitive to slight disturbances. "The result was quickly forgotten," says Chapline, "because it didn't agree with the prediction of general relativity. But actually, it was absolutely correct."

This strange behaviour, he says, is the signature of a 'quantum phase transition' of space-time. Chapline argues that a star doesn't simply collapse to form a black hole; instead, the space-time inside it becomes filled with dark energy and this has some intriguing gravitational effects.

Don't get confused by the nature of Schwarzschild coordinates at the horizon. Light from the horizon never reaches an outside observer, and it's the rate at which light pulses leave a point (or are redshifted) that defines "time relative to an external observer". So by that mathematical definition, nothing ever reaches an event horizon (and you could argue that the horizon "never" forms). However, a more meaningful question is, what does an observer falling into the hole actually experience? And it's easy to show that such an observer does encounter an event horizon, and from which it cannot escape, even if an outside observer can't tell that this has happened. In that sense, black holes very much do exist. See also this FAQ.

or the Bogdanov brothers http://math.ucr.edu/home/baez/bogdanoff/

For the record, the idea that glass flows is an urban
legend

You mean, why isn't the expansion unmeasurable because our measuring sticks are expanding with space? See this FAQ.

One project I've been tempted several times to join, but never quite got the impetus, is the HAL (hyperspatial analog to language) language data structures.

Basically, HAL stores a corpus of text with n distinct words as an n-dimensional array encoding the frequency of co-occurence of various words. This doesn't sound like much, but the results they obtain with it are amazing. Just from scanning a set of writings, they can tell the author's:
* Age
* Gender
* Education Level
* A few other things I can't remember off the top of my head...

Also, HAL gives some great results on word correlations -- including some "duh" relationships and some "wtf?!? oh, right, that DOES make sense..." ones.
Best of all, the server for HAL's web page is called locutus...

John Baez, quantum gravity reseacher have an exellent list on his site of Open questions in Physics
It includes:
sonoluminescence - plasma core in the bubbles of liquid
high temperature superconductivity
turbulence and Navier-Stokes equations -mathematic of chaos
what is meant by a "measurement" in quantum mechanics? Does "wavefunction collapse" actually happen as a physical process ?
What happened at or before the Big Bang?
Why is there an arrow of time; that is, why is the future so much different from the past?
dark energy
dark matter
The Horizon Problem: why is the Universe almost, but not quite, homogeneous on the very largest distance scales
When were the first stars formed, and what were they like
Is the Cosmic Censorship Hypothesis true? Roughly, for generic collapsing isolated gravitational systems are the singularities that might develop guaranteed to be hidden beyond a smooth event horizon?
Why are the laws of physics not symmetrical between left and right, future and past, and between matter and antimatter?
Why is there more matter than antimatter, at least around here?
Is there really a Higgs boson, as predicted by the Standard Model of particle physics?
Why do the particles have the precise masses they do? Or is this an unanswerable question?
Are there important aspects of the Universe that can only be understood using the Anthropic Principle?
The Big Question(TM)
This last question sits on the fence between cosmology and particle physics:
* How can we merge quantum theory and general relativity to create a quantum theory of gravity? How can we test this theory?

I don't think you've quite nailed it either.

Objects that travel at the speed of light have no rest mass. And therefore no "real" mass to speak of. Using the E=mc^2 and using algebra to derive the mass is not really the correct way to do things. See this post and it's reply which has a bit more info. Now if you want the truth I don't know much about the Higgs mechanism which is theorized to be what actually gives rise to mass, but AFAIK mass and energy aren't the same thing. You can turn one into the other and vice versa, pair production or particle/anti-particle reactions, but they have to be converted first by these reactions.

This seems to be a good overview of a photon's mass and why it needs to be zero for certain phenomenon to exist (such as gauge invariance and inverse square law):

http://math.ucr.edu/home/baez/physics/ParticleAndN uclear/photon_mass.html

The Wikipedia article, a nice summary by mathematician John Baez, and another summary and a proof of L4/L5 stability (PDF) by astrophysicist Neil Cornish.

The Wikipedia article, a nice summary by mathematician John Baez, and another summary and a proof of L4/L5 stability (PDF) by astrophysicist Neil Cornish.

It reminds me of item 33 of Baez's Crackpot Index: "40 points for comparing yourself to Galileo, suggesting that a modern-day Inquisition is hard at work on your case, and so on."

It reminds me of item 33 of Baez's Crackpot Index: "40 points for comparing yourself to Galileo, suggesting that a modern-day Inquisition is hard at work on your case, and so on."

Here is a link with a little info:
http://phyun5.ucr.edu/~wudka/Physics7/Notes_www/no de52.html

Having worked in CS and Physics at Uni for a while it has become blindingly obvious that 'rigor and peer review' often mean 'having a friends group that recognises your writing style and has $$ or credibility invested in your work'.

Never heard your PhD supervisor saying, "We'll submit it to *****, because my friend $friend is chairing it and they're bound to approve it"? It is a very common occurence. Pretty much the only person I know who doesn't do that is my current PhD supervisor, who's too bright to need the help, the smug git :)

Peer review is also a bit of a laugh, even anonymous peer review; there are a lot of niche fields of research out there. After all, if you get an article on using [massive bit of experimental equipment] in order to examine [question], it isn't too much of a leap to associate it to its author. A few weeks of peer-reviewing papers for my incredibly lazy ex-boss, and I was recognising papers based on a combination of topic, specialist vocabulary, 'concepts' [assumptions made, cited ideas] and characteristic errors in spelling and grammar.

The grandparent is right that physics suffers less from this... but he/she would be wrong to assume that it doesn't happen in physics. It does. Go look up the Bogdanov affair...

Disclaimer: I don't dislike the concept of peer review. But in practice it's all a bit more complicated than that, and much more political. Peer review just makes one imperfect assumption, the same as those who originally believed that the Internet would 'democratise society'... it assumes that your writing is untainted by identity.

You fail to mention you can download your book for free: http://webster.cs.ucr.edu/AsmTools/Gas/Programming GroundUp.pdf

I didn't find Psyco very helpful, mostly because it didn't play nicely with the profile module.

Anyway, overall, I'd rate Python+pygame very highly. It's really easy to use, and depending on what you need, the performance is usually adequate.

A finite universe has no center. It's analogous to the surface of the Earth (the surface, mind you, not the whole Earth) -- it's finite, unbounded (no edge), but there is no special "central" point on the surface of a globe.

About your paradox concerning the 1g of matter, you're forgetting that "shooting a mass" off the surface of the earth doesn't change the total energy of the system, it merely interchanges kinetic energy with gravitational potential energy. When you let the mass fall back to earth you will make the same interchanging of energy, simply in the other direction. No energy has been added or subtracted from the system so there is no paradox.

And about light being affected by gravity:
"any particles such as photons of light, move along geodesics in general relativity and the path they follow is independent of their mass." (2)

About your paradox concerning the 1g of matter, you're forgetting that "shooting a mass" off the surface of the earth doesn't change the total energy of the system, it merely interchanges kinetic energy with gravitational potential energy. When you let the mass fall back to earth you will make the same interchanging of energy, simply in the other direction. No energy has been added or subtracted from the system so there is no paradox.

And about light being affected by gravity:
"any particles such as photons of light, move along geodesics in general relativity and the path they follow is independent of their mass." (2)

The relativistic rocket.

What the twins see.

No.

No.

And read this for a more detailed explanation of the issue.

1. Quoting:

   Physicists today are groping for this "theory of everything." [...] So far, the leading--in fact, the only--candidate is string theory.

   There is at least one mainstream alternative to string theory, namely loop quantum gravity (see John Baez's This week's finds in mathematical physics, week 134 for a discussion of some of the problems plaguing the various approaches.)
2. And:

   Unfortunately, no one has ever seen negative matter. In principle, it should weigh less than nothing and fall up, rather than down.

   If one holds the equivalence of gravitational and inertial mass, then this is wrong. A negative mass object will fall towards a positive mass, but the positive mass will be repelled. A pair of perfectly matched masses of opposite 'sign' would, if unimpeded, accelerate for ever.

Not quite true, there are speculations on if his experiment did actually do this. A guy named Fransons was the one to point out a possible fault in his experiment (since were talking about Q.M. nothing is certain so the fault is only "possible" :-) ).

See for instance http://math.ucr.edu/home/baez/physics/Quantum/bell s_inequality.html/

I think [..] Eventually, we will have quantum computers capable of brute-forcing even quantum encryption...

Well, you think wrong. Quantum encryption cannot be 'brute-forced'. Because it's not 'encryption' in the conventional sense but rather 'secure transmission'. The data is not encoded, but rather transmitted in a way which makes eavesdropping impossible. Since you can't intercept any 'coded message', there is nothing for you to brute-force.

And this holds as long as what we know of quantum mechanics holds.
(More specifically, the Bell inequality. Which was verified in the famous Aspect experiment.)

So no, nothing in quantum physics is going to invalidate quantum encryption. And I wouldn't get my hopes up for future theories, either, because this 'wierdness' of quantum mechanics so well-verified experimentally that it'd be unlikely that any future theory would change it. (But hopefully explain it)

If someone tries to intercept this stream of photons--call her Eve--she cannot measure both modes, thanks to Heisenberg. If she makes the measurements in the wrong mode, even if she resends the bits to Bob in the same way she measured them, she will inevitably introduce errors. Alice and Bob can detect the presence of the eavesdropper by comparing selected bits and checking for errors.

The real advantage of using entangled photons would be in sending information faster than light. Entangled Photons in Computers actually might solve all the copper issues in speed we're having in chip DIE size vs clock speed (as in how to get a signal from one end of the chip to the other in a single clock signal).

Blackboard is a good idea. Its a common place for professors, TA, students to go for information. Its a common medium to submitting homework to the TA. Blackboard can setup in such a way that you can have class mailing lists, discussion forums, a "whiteboard" for virtual meetings.

It is one interface for ALL classes.

Now the problems with blackboard. It is a PIECE OF SHIT system. You ever try to take a timed quiz with it? Ha! don't press that back button, pray that your browser doesn't crash. Why? Because when you start the quiz, it records that you "took the assessment", even if you didn't submit. So fi you hit the back button or lose your session, bam! bye bye quiz. Email your professor and beg and plead for your quiz to be reset. If your lucky, you can still get those points.

Submitting papers/homework online with blackboard? Well they have a "digital drop box". I've used it before and it's fairly convenient (as in i'm a lazy fatass who doesn't go to lecture every day). So in the digital dropbox, there are two buttons. ADD FILE and SEND FILE. Alot of people get screwed over by ADD FILE and think, oh the TA will see it. WRONG! You have to either ADD FILE and then SEND FILE or the TA won't see it otherwise. In release 6, they fixed that problem by adding the ability to upload files in SEND FILE. Still, many students find it is fairly confusing to see ADD FILE and SEND FILE next to eachother.

Lastly, emailing people in the class. God damned, I get like 10 of these "spams" from fellow students. Basically when you use the email function of blackboard, it doesn't any information about what class/section it was from. So I end up getting these emails "The first midterm scores were really low, anyone want to get together for a study group?" uh huh...and is this for bio or for history?

Lastly. Information control. With plain old webpages, students can troll the internet to find class information professors are covering. This is especially important if one wants to "preview" a class. Well, with blackboard. Unless your registered in the class, you have no access to it.

In a nutshell. Blackboard sucks.
Forest Grump, Blackboard User

Any substance can be a liquid, it's a matter of melting point vs ambient temperature

The issue is the definition of "solid". If you define it by behavior, you're right. But if you take into account the internal structure of the material, glass has similarities with liquids.

Many solids (for example crystalline solids) display short-range order (at least on small distances, but many materials are composed of microscopic crystals). Glass has no such small-scale order; it's therefore classified as an amorphous solid.

Essays in the Brittanica are reviewed for style and content,

signed by their authors

The EB has been many things in it's 200+ years of existence, but a haven for mediocrity, a "democratic" consensus, it is not.

Try 100 billion.

Actually, I believe the estimation was 125 billion. But according to this, there are only 3000 observed galaxies. Which means that it's great for those who push out into unknown space, but the rest of us are screwed.

Let me get this straight. You believe that accelerating a 5000 ton spaceship at 1 G for 25,000 years is more than the power output of the sun?

Ummm... yes. A few BOTE calculations shows that the entire sun puts out somewhere around 8.0e23 watts. From here, a 30,000 light year trip would take 62 tonnes of antimatter per kilogram. 62 tonnes of antimatter times 5000 tonnes of ship works out to 5.58e28 Joules of energy. (I'd work it out for exactly 25,000 lightyears, but it's late, and I'm lazy.)

Now if you could collect ALL of the Sun's output for 19 hours AND convert it to antimatter with 100% efficiecy, you could reach that amount of energy. Unfortunately, the later will never be the case, even if the former is. Converting Solar Energy to Antimatter can never be more than 50% efficient. Currently, it's about 0.0000001% or so. Best estimates put antimatter conversion at about 0.01% with current technology. At 0.01%, you'd need all of the Sun's output for 80 days to reach the necessary level of antimatter.

In short, outstripping our Sun's output is not that hard. If you were thinking that I was referring to extinguishing our Sun, then I apologize for the miscommunication.

How is your 5000 ton spaceship carrying the energy for 1 G acceleration? After all, it only has 5000 tons of mass to begin with.

Whenever ships are discussed, their mass is always referred to in terms of "dry mass" unless specified otherwise. Our ship would need a disposable stage or ten to carry the extra 620,000 tonnes of matter and antimatter. :-)

Regardless, it's a bizarre concept to discuss in the first place

No, I'm merely trying to point out the rediculous energy requirements for doing a little space population. My original point being that all energy in the universe is finite, and that we will eventually bump into that little snafu.

Is there a specific book you can reccommend?

Wrong. At least assuming you mean scientists and other intelligent individuals. The reasons that the average person believes what they believe are not relevant to this discussion.

As for scientists, their view on evolution is usually founded in the scientific method and falsifiability.

I don't think any scientist will tell you that the theory of evolution is complete or proven in every aspect - as with most facets of biology, it's complex, and the data we have is essentially a partial, but extensive, set of samples. The problem with Creationists is that they fail to separate articles of faith ('God is the ultimate creator of the world' - a statement that is not incompatible with falsifiable observations) and science ('the world is 5000 years old' - there is no evidence to support this and many other such claims).

Obviously, it's a complicated fray, and some of the Intelligent Design people make less outlandish claims, and instead try to attack the theory of evolution by finding exceptions or outliers. Unfortunately, they often selectively ignore important research and evidence, and have mostly been debunked (yes, I've read some of this stuff by these people out of curiousity to see how they presented their arguments, and I wasn't very impressed).

Most of the arguments, at a basic level, are elucidated quite well on the talk.origins FAQ. Strangely, the site doesn't read like religious mantra to me.

From this explanation. Twin A stays on Earth and Twin B sets off in a spaceship going 0.995 c (time and space will dilate to 1/10th). He reaches a point C that is 9.995 light-years away and heads back at the same speed. Let's assume accelleration is instantaneous. When Twin B leaves earth, both twins agree their clocks read zero. When Twin B reaches point C, Twin A sees that his clock reads 10 years and Twin B's clock reads 1 year. Twin B thinks his clock reads 1 year and Twin A's clock reads 0.1 year. As soon as he turns around, Twin A still thinks B's clock reads 1 year and his clock reads 10 years, but Twin B thinks his clock reads 1 year and Twin A's clock reads 19.9 years.

Sigh, all I ever hear are bad explanations of the Twin Paradox. Let's be clear - there's no need to invoke General Relativity to explain the Twin Paradox at all. It clears a few questions up, but you still don't need it.

Here is a great explanation using only Doppler shifts, which most people understand quite easily.

The problem that you have is that you're assuming that Twin A sees Twin B reach Point C at the same time that Twin B reaches point C - he doesn't!

From Twin A's frame, he sees Twin B leave at year 0. He calculates twin B arrive at point C at year 10, but he can't see twin B arrive at point C until the year 19.995, because any light signal from point C won't arrive at Twin A before then! Amazingly enough, in the 0.005 years before Twin B arrives home, all of the images of Twin B for his entire trip home arrive all in a bunch! They're all massively blueshifted!

So Twin A sees an outbound leg that took 19.995 years for all of the images to arrive, and an inbound leg that took 0.005 years to arrive. For Twin B, this isn't true - for the outbound trip, he sees Twin A age at 1/10 the speed, and when he arrives at Point C, he's only seen Twin A age 0.1 years. On the way back, however, Twin B will see Twin A age just as rapidly as Twin A sees Twin B age in the last 0.005 years - but he'll see it for an entire year! So Twin A ages far beyond Twin B, and they will both agree that Twin A is older.

There's a terrific spacetime diagram showing this here.

The vacuum energy isn't nearly as large as you think; about 10^-9 joules/cubic centimeter.

I haven't read Froning, but Sheffield's ideas only work if our vacuum is only a false vacuum, and we can extract energy differences between it and the underlying true vacuum. TANSTAAFL.

A government which is abiding by the law would be firing and prosecuting the Secret Service agents and police officials responsible for these outrages, rather than institutionalizing the violation of civil rights under color of law. A government which abuses the power of arrest to "protect" the President from seeing people who disagree with his policies is not a government which is abiding by the Constitution, and to allow it to remain in office one day longer is to place all rights in jeopardy. The bastard has violated his oath of office (so much for his claim of "keeping his word"), and voting him out is the duty of everyone who holds the Constitution to heart.

Which, unfortunately, isn't all that many people these days.

That explains why museums are full of puddles where the roman vases used to be.

You're spreading a myth.

It's an amorphous solid, which is different.

This is much more than a simple issue of consumers not being able to record their favorite shows, not being able to use a homemade PVR or any basic consumer rights. Call me a conspiracy theorist, but we are walking a very dangerous path with government regulation of this type. Our government is telling private companies that they cannot create a particular product not because it's dangerous and not because it interferes with areas in the public domain (e.g. transmitting on unauthorized frequencies). Government is regulating production of equipment by private companies only because another private organization doesn't like it and may lose money without it.

How long is our government is burning books that tell how to circumvent this technology and locking up the authors. The US Government is starting to remind me of the Inquisition and Gallileo - persecuting anyone that might innovate or discover anything new just to keep the status quo.

I believe that anyone should be able to build any type of Television (or any other machine or electronic device) and sell it as long as it meets some reasonable guidelines of public safety, and traditionally this has ben the case. If the MPAA has a problem with the way any item is manufactured, what it does and what it's used for they are free to pursue the case under a civil suit.

There are other tests.

Clarification: if you call the objects A and B, and they are each seen to recede at 0.75c in C's frame, then A recedes from B at 0.96c in B's frame, and B recedes from A at 0.96 c in A's frame. In C's frame, A recedes from B at 1.5c, as you say, but this doesn't violate any tenet of special relativity, because neither A nor B recede from C (or from any other observer) faster than light.

See this FAQ.

Does gravity travel faster than light?

If I send an object in one direction at 0.75*c (3/4 the speed of light), and another object in the opposite direction, also at 0.75*c, aren't they traveling apart from each other at 1.5*c?

If I had a steel rod that was 4,000 miles long, and I pushed on one end of it, would a spectator at the other end see their end of the rod move simultaneously, or would something about relatively cause a delay?

Does gravity travel faster than light?

If I send an object in one direction at 0.75*c (3/4 the speed of light), and another object in the opposite direction, also at 0.75*c, aren't they traveling apart from each other at 1.5*c?

If I had a steel rod that was 4,000 miles long, and I pushed on one end of it, would a spectator at the other end see their end of the rod move simultaneously, or would something about relatively cause a delay?

Does gravity travel faster than light?

If I send an object in one direction at 0.75*c (3/4 the speed of light), and another object in the opposite direction, also at 0.75*c, aren't they traveling apart from each other at 1.5*c?

If I had a steel rod that was 4,000 miles long, and I pushed on one end of it, would a spectator at the other end see their end of the rod move simultaneously, or would something about relatively cause a delay?

Recently I've read couple of articles speculating the possibility of gravity being faster than the speed of light and also that Kopeikin-Fomalot work on measuring speed of gravity (or rather propagation of gravitational force) is rather controversial.

At the same time, I find this observation by Van Flaudern very interesting and logical

"Problems with the causality principle also exist for GR in this connection, such as explaining how the external fields between binary black holes manage to continually update without benefit of communication with the masses hidden behind event horizons."

sorry, not Joan Baez (whose word on physics matters I have no reason to trust in particular ;-) but John Baez, who is an eminent mathematical physicist (doing research on quantum gravity) and one of the moderators and chief contributors to the sci.physics.research newsgroup (where I am constantly impressed by his grasp of physics and the explanatory ability (check out his web page, it's fun!)). He was quoted in the New Scientist article I cited, that's why I mentioned the name.

This is a known effect, but it doesn't allow for FTL communication.

This comment further down mentions this link which has some good information on the subject. I definitely have observed the illusion of thinking I'm going downhill visually, but my legs (when on a bicycle) or my car engine tell a different story.