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Comment: Credit Card Charge (Score 1) 138

by Roger W Moore (#48603505) Attached to: Amazon UK Glitch Sells Thousands of Products For a Penny

So, once the order has been placed, haven't you effectively entered into a contract for sale or something?

No, not until your credit card has been charged. If they have done that then you have them under the credit card agreement but before that they can wriggle out of it as a mistake under their own terms.

Comment: Re:Entropy (Score 1) 107

by Roger W Moore (#48598793) Attached to: 2 Futures Can Explain Time's Mysterious Past
Given the context - which is a post of Slashdot and not a paper - I'd stick with countless as in "too many to be counted" or "very many" given that I'm not willing to put in the large amount of effort that would be required to actually count them. Rather than the hugely overly technical considerations you are engaging in there is a very easy way to simplify this.

If I start with the glass on the table then there are is a very large range of momenta I can give the glass to arrive at the state where it is shards on the floor so long as I don't care which particular set of shards it makes. To convert from any given set of shards on the floor back to a glass I have to give each shard a precise linear and angular momentum such that they will reassemble themselves into the glass. Hence in the phase space of all possible momenta for all the shards I have to hit a single point where as for the reverse just have to hit a large area in a far lower dimensional phase space. The same applies to glasses colliding in space.

In the high energy limit the same will apply. The nuclei of the glass will collide to produce hadronic showers, each particle of which will have its own 4-momentum. However in this case it is clear that you cannot reverse the system since some of the interactions and subsequent decays will involve the weak force which we know is not symmetric under time reversal.

Comment: Ever been to London? (Score 2) 295

by Roger W Moore (#48598705) Attached to: French Cabbies Say They'll Block Paris Roads On Monday Over Uber

As such, I take a lot of taxi rides each year. But it doesn't matter if I'm in NYC, London, Paris, Berlin, Toronto, LA....

Have you actually ever taken a cab in London? The problem is the exact opposite of what you describe with only ~5% from minorities to the extent that they are trying to recruit more. As for "untrained hipster" they are required to pass The Knowledge before they get a license. They may have somewhat colourful characters but I've never had one who is not extremely competent, knowledgeable and driving a clear, well repaired cab.

Comment: Entropy (Score 1) 107

by Roger W Moore (#48559733) Attached to: 2 Futures Can Explain Time's Mysterious Past

Eggs turn into chickens at a different rate than chicken turns into eggs. This is proof either that A) time must go forwards, or B) my proof has a logic flaw in it.

....or C) that you forgot to account for entropy. To study time reversal violation you must have two states with identical entropy or you must account for the effects of entropy. The reason that a glass falling from a table and shatters is far more likely than all the pieces of glass coming together, leaping off the floor and forming a new glass is because of entropy. There are countless ways in which a glass on a table can be converted to broken shards on the floor but starting with the shards there is only one way that that process can be reversed.

Scale the system up, and they're just little birds that fly in boring ways, don't time travel, don't fly faster than light,...

Ummm...yes but the reason for that is because the fundamental physics governing the particles of which the starlings are made up prevent time travel and moving faster than light (which are actually one and the same). Assuming you are building a model out of simple, plastic lego bricks then regardless of what you are building we know that it will not be a conductor of electricity because the bricks you are building it from are all plastic insulators. Studying the fundamental physics of a system lets you know what is possible.

For example we know that there is a fundamental arrow of time despite the fact that at an everyday scale this is completely obscured by entropy. You could study all the flocks of starlings you like but it would be impossible to show that you have time reversal violations in it...and yet since the particles in that system are subject to the weak force we know that at some incredibly tiny, insignificant level it is there.

Comment: Simple Explanation (Score 1) 107

by Roger W Moore (#48559491) Attached to: 2 Futures Can Explain Time's Mysterious Past

Because GP (and some physicist) think that if particle physics correctly describes matter/anti-matter....

Whoa there it is a LOT simpler than that. If you have a system in state A and it changes into state B then your process is A-->B. If you reverse time then the process you have is B-->A. Now if both these states have identical entropy there are no phase space arguments to favour one state over the other and so both processes (A-->B and B-->A) should be equally likely if the laws of physics are the same with regard to the direction of time.

What these experiments showed are that for some systems A-->B is more likely than B-->A and so the laws of physics define an arrow of time. If time were reversed then A-->B would become less likely than B-->A which is how you could detect it. It's the temporal equivalent of looking in a mirror. If you have a perfect left-right symmetry you cannot tell wether the image you are looking at is the real object or the reflection. However if the object is not left-right symmetric it is easy to know which image you are seeing.

So it does prove that there is an arrow of time. Perhaps you ought to spend a little time understanding the physics before you start applying simple logic: it tends to lead to more accurate conclusions.

Comment: Arrow of Time (Score 5, Informative) 107

by Roger W Moore (#48553781) Attached to: 2 Futures Can Explain Time's Mysterious Past
Actually we can do better than that. The arrow of time is baked into fundamental particle physics and we have known this since the 1990's when an experiment, CPLEAR, showed that kaons turn into anti-kaons at a different rate than they switch back. This is completely independent of entropy and the result was further improved on by the Babar experiment only a few years ago showing that the 'T violation' occurs in B-mesons as well.

The article is wrong when it says that the laws of physics work the same going forwards or backwards in time. They do not and there is data to prove it. So the 'arrow of time' does not need any entropy to define it - it is baked into fundamental particle physics.

Comment: Re:What late afternoon sun? (Score 1) 327

by Roger W Moore (#48540239) Attached to: You're Doing It All Wrong: Solar Panels Should Face West, Not South

Pro tip: "afternoon" means before sunset, by definition.

Clearly you are not a pro at English and should not be giving tips. 'Afternoon' means, quite literally, after noon. Evening is usually taken as roughly from 6pm to ~10-11pm. Those living further north in the arctic circle still have a morning, afternoon and evening even if the sun does not rise at all.

Comment: What late afternoon sun? (Score 3, Insightful) 327

by Roger W Moore (#48512469) Attached to: You're Doing It All Wrong: Solar Panels Should Face West, Not South

a homeowner can buy a device called a tracker that will pivot them

For those of us up in Canada or Northern Europe you need to mount the pannels on a vehicle which heads a long way south or west trailing a cable if they are going to be pointing at the sun in the late afternoon since the sun sets here around 15:30-16:00 this time of year. Simply pivoting or pointing west is just not going to cut it.

Comment: Python + ROOT "C++" = Python (Score 2) 34

by Roger W Moore (#48508021) Attached to: The Life of an ATLAS Physicist At CERN
Possibly because it often isn't coding in real C++. In ATLAS, and particle physics in general, we use this awful data analysis package called ROOT which is about the worst example of C++ code you can possibly imagine (although it has significantly improved over the years). This package uses a C++ interpreter so that you can write C++ scripts. Sadly this interpreter cannot implement the full set of C++ so major bits of functionality are missing like virtual functions so it's hard to really call this C++.

Unfortunately, while there are many issues with ROOT, it is incredibly fast at I/O and has lots of features which do what we need (if you can navigate past the bugs, memory leaks and dodgy documentation). One way to do help with this is to use the Python interface so many of us use the Python interface as a shield from the full horror of ROOT. The other alternative is to write compiled C++ code which gives you the complete C++ functionality but still leaves you with the minefield of linking to ROOT. To give an example of how bad this can be a few years ago they had a bug which made you code dependent on the comments i.e. by adding a comment line the code generated a duplicate symbol error when linked. After a day of tracking this down to a pre-processor macro I was told by the root development team that they already knew about this bug but could not fix it...that was also the day I switched to using the Python interface!

Comment: Re:Knee-jerk... (Score 5, Insightful) 256

It's probably just more leverage to encourage people not to drive drunk.

Agreed but they had better not make any mistakes and accuse someone who does not subsequently get convicted. While it is hard to see how someone arrested for drunk driving would be not convicted they do have a history of mistakes like this. A few years ago they busted an online child pornography ring and then went around and named people whose credit cards were used without stopping to think that some of those cards were stolen and used fraudulently.

I'm all in favour of doing what we can to stop drunk driving but deliberately naming and shaming people before they have a conviction is dangerous at best and just plain wrong if those people are not found guilty.

Comment: Re:Writing Maths (Score 1) 523

by Roger W Moore (#48498381) Attached to: Finland Dumps Handwriting In Favor of Typing
Clearly you have never done experimental physics. Not only are there plenty of 'back of the envelope' calculations that would take far longer to input into a CAS system than to solve but we also use notation that I've no clue how to put into a CAS system. For example in the Standard Model Lagrangian I have 'vectors' to represent spin and colour. These are written into the same term as a multiplication and yet each colour vector must only multiply with colour matrices and other colour vectors. This is achieved by the summation convention but I've never seen a CAS system that supports this properly in a way that is simple enough for 'everyday' calculations.

Comment: Re:Girls, girls, girls... (Score 5, Insightful) 333

I can just see having to explain to a 7-year-old-child that heard about the program and doesn't understand why he can't try to be involved that it's because he's a boy.

We've already had to have that conversation with our 10 year old son. The Engineering faculty of our local university runs a Raspberry Pi programming course...but only for girls. My wife contacted them to ask about programs for our son. The super enthusiastic airhead who responded suggested that they had lots of programs for boys but really it boils down to a few places in a summer program and even then much of that program is for girls only. My wife got as far as asking them how their blatant sexism was consistent with the Alberta Human Rights act but got a typical email full of PR but empty of content. In the EU such practice would actually be illegal under gender discrimination laws in Alberta it is less clear since they have this get-out clause 'unless there is a justifiable reason'.

So we had to explain that there were no programs for him because he is a boy which he had a really hard time understanding because he has always been taught that sexism is wrong. Since actions speak louder than words this has undermined the lesson that he had learnt and I've already heard him once tease his older sister that she shouldn't use computers until she has had the 'special lessons for girls'! So as a scheme to eradicate sexism this is an epic way to shoot yourself in the foot. Even simple logic tells you that you cannot eradicate sexism while actually practicing it!

"Why waste negative entropy on comments, when you could use the same entropy to create bugs instead?" -- Steve Elias