Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Re:Really? (Score 2) 55

My thoughts exactly. Billions of cycles on the client's machine, billions of cycles on the different servers that are needlessly serving this speculative content for the first few incorrect guesses, billions of cycles on all the routers in between...

Where exactly do they think they are saving energy? One second of display power and idling cpu on the client side? I would be highly surprised if this would be net positive.

Yes, it will load pages slightly faster. But at the expense of quite a bit of wasted energy.

Comment Re:Why can't this be detected (Score 2) 108

Indeed quite hard to believe. They just though of the situation where someone would keep guessing the number on the same website, but never thought someone might try different websites. Because, you know, it takes a whole lot of effort to open up a different website...

What I'm wondering, though, is how they can guess all the numbers. Sure, the useless three-digit protection code on the back of the card only takes 1000 guesses in the worst case. And the number of expiration dates is even less, 60 or so. But they said they could guess the number by starting only with the first 6 digits (bank and card type). That leaves 10 digits to guess! Even if there are a few for typo detection (2, probably?) that still leaves 100 million codes to check. Were they using 10 million e-commerce sites?

Comment Re:Crybabies (Score 1) 524

Let me get this straight... An illegal immigrant can register to vote, and nobody checks whether or not he's a US citizen?

When I'm on vacation in the US, can I register to vote using my hotel address and then actually vote for your president?

Mind blown. Maybe it's because I'm European.

Comment Re:Soft target attacked by cowards (Score 1) 734

But Trump has the best words. He has better words than anyone. If anything goes wrong, it will be someone else's fault, he alone will know how to fix it, and he'll tell everyone with so much energy that 51% of Americans will believe it even though the rest of the world is flabbergasted by how gullible they are.

Comment Re:Not spacex (Score 1) 734

GM got subsidized loans from US govt too. And Tesla paid back its loans early.

Credits for electric cars are turning into a disadvantage for Tesla, since the market for credits is oversaturated so they only get 50 cents on the dollar, and they are only valid for a limited number of cars which Tesla is rapidly approaching.

SpaceX is getting lucrative contracts from the US Govt, indeed. But if SpaceX didn't take them, some other company (or country!) would. SpaceX just gets the contracts because they are the cheapest. Free market at work, there.

Meanwhile the oil industry keeps getting subsidies that are orders of magnitude larger than those for renewable energy. Even more so if you count the price of pollution.

Comment Re:You can't (Score 1) 1321

But you don't need to count all of them. If you think something fishy is going on in a whole bunch of districts, just pick a few boxes and count them. If they are OK, then maybe there was no widespread fraud after all.

Also, this counting would only be done by those who really want to. Don't trust the result? Here are the boxes, go ahead and count them on your own time.

Comment Re:You can't (Score 1) 1321

And it's not like this is difficult to do. Let the machine record the vote, and also print out an anonymous paper copy that the voter can verify visually. The paper copies go into an old-fashioned ballot box. If there's any doubt about the electronic results, the paper copies can be counted to verify that the results match.

Also, a few polling stations can be picked at random to have their paper copies counted even if there's no suspicion. This can be done after the electronic results have been announced, it's just a fail safe.

The only remaining problem is people switching their paper copy with one they printed at home, and then claiming the machine was hacked just to sabotage the election. But the incentive for that would be way less as you don't really have much to gain there. Would also be relatively easy to prevent: for example, print one of 100 images on the back of the slip, display the same image on a screen next to the ballot box, and let someone verify that the images match before you put it into the box. There are probably much easier solutions, too, it's just the first one that comes to mind.

Comment Re:This is BIG news - If you want to know more.. (Score 1) 477

Oh my, where to begin...

The only maximum speed for rockets, any type of rocket given enough fuel, is the speed of light. Rockets are not limited by the speed of their exhaust. Do some googling if you don't believe me. In fact, the Apollo 11 mission reached speeds in excess of 11 km/s with an exhaust velocity of less than 5 km/s. As they were powering away from us, their exhaust was also moving away from us. What "currently accepted law of physics" did they break? None whatsoever.

If you are on a boat that's moving forward at 10 m/s, and you jump off the back with 5 m/s (so you are still traveling in the same direction of the boat at 5 m/s), won't that push the boat forward? Same thing with rockets.

The only thing that matters for a rocket in vacuum is the speed of the exhaust relative to the rocket. There are no absolute speeds in space, so if the rocket did have a maximum speed, what would it be relative to? Relative to earth? They're in space, earth is just one of trillions of rocks flying in all directions at vastly different speeds. Why would the rocket have a maximum speed relative to one rock in particular? (Apart from the speed of light, but I won't get into relativity here).

So no, rockets in vacuum produce the same thrust at any speed. This means that, if they are going faster, the engines are producing more kinetic energy per second.

Now I imagine you are probably thinking you caught me on an inconsistency here. Didn't I just say that there were no absolute speeds in space? How can they become more efficient at higher speeds then? Speed relative to what?

Indeed. All speeds are relative, but kinetic energy is also relative. A car coming towards you has lots of kinetic energy (and can therefore cause a lot of damage if it hits you) but if you are traveling in the same direction at the same speed, it has zero kinetic energy from your point of view.

When rockets are flying close to planets, we only care about their kinetic energy relative to that planet because we want to move to an orbit that corresponds to a certain amount of energy, or escape from the planet at a certain speed relative to that planet.

So how do we get as much kinetic energy as possible relative to that planet? By producing thrust (which is constant like I said) at the point where the relative speed of the rocket is the highest (which coincidentally happens to be at the deepest point in the gravity well).

I don't think you read the entire Wikipedia article I linked to, about the Oberth effect. Scroll down to "explanation in terms of work". The derivative of the kinetic energy is thrust (F) times speed (v). Same thrust, higher speed, more energy gain. It really is that simple.

You can also explain it as "leaving the fuel deep in the gravity well where it has less potential energy, so you are throwing away less energy that way" and in a way that's true, but it's not very practical for actual calculations. (If you think it's practical, I won't argue with you).

Slashdot Top Deals

1.79 x 10^12 furlongs per fortnight -- it's not just a good idea, it's the law!

Working...