Time cannot change by definition. Nothing can move in spacetime for the same reason. This is why the late Sir Karl Popper (of falsifiability fame) once compared spacetime to Parmenides' block universe and called it "Eintein's block universe in which nothing ever happens". (Source: Conjectures and Refutations).
In his textbook, "Relativity From A to B", renown relativity expert Robert Geroch wrote, "There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes." Very few physicists know this but it's the truth, a nasty little truth for some, but the truth nonetheless.
In conclusion, any talk of time travel in any direction (forward or backward) is pure crackpottery. There is only the NOW, the ever changing present. Don't mod me down because you have a different opinion. Incessant propaganda and sci-fi movies like Star-Trek have duped a lot of people. Just think about it and figure it out on your own.
You're not explaining that very well. Yes, classic relativity is a deterministic theory which doesn't have a time arrow. You can look at it as a single, static universe defined as the sum of all moments. But that's neither here nor there. Classic relativity is, strictly speaking, wrong: the real universe is, as far as we understand, provably non-deterministic.
And in any case, it has nothing to do with this article, which is about the time arrow defined by entropy.
I am not sure exactly what you explained. First off, relativity, like Newtonian mechanics, is a classical physics theory. I am not aware of any such thing as non-classical relativity. So why even say classical relativity? At the very least, it is redundant.
Second, of course the universe is probabilistic, a fact that falsifies both relativity and Newtonian physics.
Third, the universe is probabilistic precisely because time cannot change. Why? Because, since time is not a variable and is thus non-existent, the universe cannot calculate precise temporal durations. Thus, in order to properly conserve energy, it is forced to use the next best thing: probability.
Fourth, this has everything to do with article since entropy, as explained in the text books, assumes the passage of time and thus a time direction or arrow. Since time is abstract, it follows that an arrow of time is imaginary. As a result, it makes perfect sense that one cannot reverse entropy. Or anything else, for that matter.
The purpose of my comment was to get people to think and to stop accepting everything they hear on face value. If time cannot change, which is trivially shown to be true (changing time is an oxymoron because it is circular), then all the so-called time-travel conjectures by famous physicists like Kip Thorne, Stephen Hawking, David Deutsch, and many others, are pure crackpottery.
I don't think you get it. A block universe in which nothing happens cannot possibly exist since it is clearly falsified. We observe change, do we not? So speaking of loops within a block universe is like arguing about how many angels can dance on the head of a pin. Is it me, or do other people go out of their way to be illogical?
"nothing ever moves" does not mean that no blocks in the block universe are related in such a way that we can reasonably say the same object is in both. and if the same object is in two or more blocks of the universe, which are different times, then it exists at different times, or in other words travels through time. this doesn't prove traveling back in time, or skipping forward in time is possible, but the concept does make sense in a block universe, and the standard time travel via time passing still works fine.
I think the voting problem is a serious one. Apparently, only a minority of readers and posters vote and they seem to have a gang mentality that works like this: "If I don't like you, I'll vote you down regardless of what you write." This sucks the big one.
The same problem is happening on every site where voting is allowed. There is usually a loud, highly emotional and political minority with a lot of time on their hands that invariably takes over and impose a fascist dictatorship on the rest of the community. Digg, Slashdot and Wikipedia are cases in point. I wish there was a way to motivate a greater percentage of readers to take part in the voting process.
Another problem is that a lot of people receive updates via RSS news readers and I suspect that most go directly to the link and rarely check the comments or attempt to vote. YC needs a way to entice people to visit the site and incorporate the number of times a link is clicked to the formula that computes the popularity value of the story. Just one man's opinion.
"I think the voting problem is a serious one. Apparently, only a minority of readers and posters vote and they seem to have a gang mentality that works like this: "If I don't like you, I'll vote you down regardless of what you write." This sucks the big one."
Maybe fade the commenter's name when a comment is posted and restore it to full visibility, say 24 (or 48 or 100) hours later? This way you are forced to focus on the content of the comment and not the commenter.
Amazon has had the problem of bi-modal review distributions for a while (most reviews are either 5 or 1 stars.) They've done some ineffective things to try to change that, like specifically requesting reviews from people. But then, unless people are emotional about a product, why bother?
Skinner: [Looking at political buttons at Cockamamie's] Hmm. These campaign buttons are all partisan. Don’t you have any neutral ones? "May the better man win," "Let's have a good, clean election," that sort of thing?
The best solution would be to do what governments have always done: Limit the amount of votes per person.
There are more subtle ways. Raising karma needed for downvote, better as a function of site size. Making downvotes cost you karma. Giving "objetive" scores to certain comments so voting them has an effect on voters' karma. Hiding comments score so you don't get influenced by others' votes. Delaying application of karma so you have to behave instead of probing how to game the system.
One thing that I've seen that doesn't work is to use simplistic algorithms that operate automatically based on karma and agreement. That method results in groupthink and, if the site is popular enough, people gaming the system for profit. Other times it generates two confronted bands. It seems that an external human feedback is needed peridically to inform the system what's undesirable.
Also to give modding quotas, so one only receives a fixed number of mod points that can be applied before having to wait to receive more. That would make each user have a similar impact on the board, whereby an upper limit is placed to curtail people from going on an unthinking modding binge.
That creates a strong bias for people with lots of time on their hands which I reckon tips the voting bias towards people not actually running a startup.
Karma isn't a function of usefulness to the community, it's a function of time spent on the site, broadly speaking. As such, I suspect that those that have the most experience with startups on average tend to be below the mean in the karma pool. Thus giving those with the most karma an additional boost in shaping the site dynamics would push the site further in the direction of "fans of startups" as opposed to "people working on startups".
Aren't most people here fans of his to some degree? I mean, I don't accept his writing as The Word of Landru, but I thought most people found the site due to his writings and linking to it?
Why does almost every startup have to be a social web site or some other web app? The web is surely not the only thing in the hacker universe, is it? The biggest opportunities in computing today are in parallel programming tools and multicore architecture and design. How come nobody seems to care about those things?
I note that your Phd dissertation was titled, "Prefetch mechanisms by application memory access pattern". Surely this qualifies you for all sorts of computing projects.
Parallel programming tools may make for interesting research, but that doesn't mean that it will be a good business. In general, tools startups haven't been terribly successful.
I see what you're saying and I think you're probably right. But if you can design and build a kick-ass multicore processor that blows everyone else out of the water in terms of performance, energy efficiency and ease of programming, it makes sense to give all your dev tools away for free. Heck, you could even throw in an OS and a nice browser for good measure.
I realize that I'm biased since I happen to think that multicore design is the most exciting thing out there. In my opinion, whoever solves the multicore/parallel programming problem will dominate computing for the rest of the century. The rest of the industry, including Intel, IBM, AMD, APPLE, etc... would flock like migratory birds to come and worship at your feet.
If you could design and build a flying car that runs on tap water, that would be even better. Unfortunately, that's easier said than done. Competing with Intel, AMD, etc in the processor market is also not easy -- many have tried, and generally failed.
Yeah, but this is a different ball game. The big players have an Achilles' heel. They are clueless as to what the future holds for multicore processors and they don't seem close to a solution. Parallel programming is a pain in the ass. There is even panic in the air because the big vendors have no real idea how to proceed. The solution is out there though. Some unknown startup may sneak behind them and steal the pot of gold while they're busy fighting amongst themselves.
Peakstream may not have reached their "peak" but they were bought by Google for an undisclosed sum, which was probably good timing given that larger players are now entering that field.
The new company is entering the public eye with $17 million in funding and a leadership roster that includes former executives and tech guys from Sun, VMWare, NVIDIA, and NetApp. PeakStream's Chief Scientist is Prof. Pat Hanrahan of Stanford, who was formerly involved with Stanford's stream processing research endeavor, the Brook project. The Brook project's work on using GPUs as stream processors formed the foundation on which PeakStream has built their newly announced product.
Which parallel programming startups are you referring to? Sure, the established companies are adapting their exisiting tools to address the new multicore processors but I am not aware of any new parallel programming tools startups that failed. Most of the multicore processor startups are still around. Tilera, Ambric, Pico, etc... are still hanging in there. Pico is doing great. Israel's Plurality is just now beginning to get recognition for its self-balancing 64 to 256-core hypercore chip.
My point is that there are very few new multicore startups and I think that the reason is not that too many of them failed in the past but that only a few have had anything really interesting or disruptive to offer. It remains that there is a big problem that needs to be solved right now and whoever solves it will grab a lion share of the CPU market in this century.
To what end? What specific value add is a multicore processor to mom and pop that is not being addressed by an intel quad core? The only thing that moves units is applications. As far as the general user is concerned, the processor does not exist. And that is how it should be.
Are you kidding me? Once cheap massive parallelism becomes the norm, you're going to see amazing applications for the average person, especially intelligent programs. For examples, intelligent answering systems, voice recognition, handwriting recognition, face recognition, dog walker, housekeeping robots, portable language translators, self-driving vehicles, sentries, etc... The possibilities are endless.
Depends on the tools... it's usually done in C or C++ with low-level locking primitives and that can be pretty tricky to make efficient. You can easily write code that's correct and slow, or fast and error-prone.
IMO there's a lot of room for improvement on the tools side. I don't think a new architecture is needed/warranted given the improvement we could get just from better programming models and tools.
If I gave you $100k could you build me a kick-ass multicore processor that beats Intel+AMD? Seems like its not a good space to be a startup in. But I don't know that much about it...
Not $100k, of course. But I think $5 or $6 million dollars could do it. For that, you'd get a scalable, self-balancing 16 or 32-core processor compatible with existing motherboards and chip sets, visual dev tools using multi-touch screens, and a fully built computer with an extensible parallel OS including a good set of device drivers.
The whole engineering/design phase would take about two years. After that, you enter the marketing and production phase which will require several busloads of dough but that's not my department.
In my opinion, that's exactly what they are doing. They have adopted a paralllel computing model (multithreading) that is known to be a pain in the ass to program. So far, they have no plans to change the model. They either don't know how or they are stuck in a rut because they need to maintain compatibility with legacy systems. They are in a state of panic right now, spending money left and right trying to find a solution that does not exist for their chosen model. This is a great opportunity for some other company (or a startup) to come on the scene and make a killing.
Also, forgot to mention the fact doing a web startup in these areas is cheap, quick, easy, and more likely to have a bigger payoff compared to building the kind of tools you mention.
Its not because nobody cares but more to do with business.
Web apps, social sites, news, ecommerce and so on, is what consumers want and where the money is.
The computer science and computing issues are the enablers, not the products.
After 8 years bleeding my motivation waiting for week- or month-long simulations to run, I strongly believe nobody should work on problems where the feedback loop isn't insanely short.
I care far more about working someplace small than about working on something web-based. There's just a lot less communication and bureaucracy, better odds of avoiding dysfunction.
Web-based startups just happen to satisfy both these constraints - the web as delivery mechanism yields instant feedback[1], and the web as eco-system encourages small and agile organisms.
[1] And high quality feedback. As an academic I was separated from my readers by an advisor and a dissertation committe, or by a set of anonymous reviewers and a program committee. Large companies separate you from the customer by layers of hierarchy. In a startup you're right next to your customers.
The real killer app would be a low level development tool that does not require you to use 4-5 different tools and wait near to 5 minutes to test your design on hardware.
Bravo. You're the only commenter who had something interesting and intelligent to say about the article. The others are jumping up and down and foaming at the mouth. LOL. In the future, when parallel programming becomes easy and powerful parallel computers become the norm, we will find that most applications are significantly more parallel than sequential. The coming intelligent programs will have huge numbers of sensors (visual, auditory, tactile, etc...) and effectors. These naturally call for massive parallel processing.
You Turing worshippers are so full of hate. You sound like somebody just blasphemed against your two-bit god. LOL. Too bad for you that the parallel programming crisis is about to bring Turing down from his pedestal. Then you'll shut the hell up. I have a wide grin on my face just thinking about it.
Money always talks and no chicken-shit cult of propeller heads can stop that. LOL.
I logged in just to mod you down, due to the dull sadness I feel at your apparent sense of obligation to spew such bile.
This blog post is full of misconceptions and appears to be written by an individual who has not sufficiently delved into algorithms, parallel computing, or operations research. Similar problem has been around for decades, such as controlling the flow of tasks on parallel factory assembly lines. Guess what helps us find near-optimal flows? That's right: algorithms.
It could really use some examples of what the hell he's talking about.
Wide ranging examples, too. I'm sure he could come up with one or two, but can he come up with a whole bunch, which span a reasonably wide swath of algorithm space?
Show me how to, say, invert a matrix, which is a possible-yet-annoyingly-hard problem to parallelize ordinarily, and I'll take it seriously.
I am not sure why the drug dealers think that these delivery crafts have to have human pilots on board. With the kind of money that these guys have, it would be relatively easy to implement a self-piloting craft that can go anywhere.
Sure, but the more complicated it gets, the more expertise they need. That means they need some specialized people and by that they are just augmenting the risk of getting caught at some point in the process.
Why put up this strawman? There is nothing in the article about either the limits of computation or a mathematical proof. Pretty much all it says is that the Turing sequential (or algorithmic) conmputing model is inadequate and I agree. We need a better model.
Not sure about the straw. Running a process on a multi-core machine just makes it go faster. We have always had speed improvements - this is just the latest way of achieving them. While running multiple parallel processes is going to be an interesting challenge for us programmers it is not going to change the fundamentals one jot.
You're kidding me? The computing world is about to witness the most drastic paradigm shift in its history. After all is said and done, the threaded or sequential process programming model will not only be superseded, we will kick ourselves in the ass for having been so stupid for so long.
In his textbook, "Relativity From A to B", renown relativity expert Robert Geroch wrote, "There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes." Very few physicists know this but it's the truth, a nasty little truth for some, but the truth nonetheless.
In conclusion, any talk of time travel in any direction (forward or backward) is pure crackpottery. There is only the NOW, the ever changing present. Don't mod me down because you have a different opinion. Incessant propaganda and sci-fi movies like Star-Trek have duped a lot of people. Just think about it and figure it out on your own.
Nothing can move in spacetime.