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Comment Some basic flaws here (Score 5, Informative) 298

Off the top of my head:

1. "Every year we hear about people dying in plane crashes. This does not have to continue..." But air travel is already the safest mode of travel. Hear all those people screaming for new technology to make road travel safe? No? Well, they're the same ones that will take this up.

2. "Passengers might board a capsule at a local bus station and wake up in another city on the other side of the country, or planet, after a road, air and rail journey during which they didn't leave their seat." They don't seem to realise the blindingly obvious point that this is making air travel *worse*. Air travel already involves sitting in a seat for too long. Why would I opt for a mode of travel that exchanges a few minutes of having to be polite to people in the aisles for one that involves several hours more in the same damn seat?

3. If you want to see just how off-their-faces unrealistic this is, look no further than this sentence: "Clip-Air's researchers, who are also looking into the possibility of using biofuels or liquid hydrogen as alternative fuels, have already initiated some contacts with the aerospace industry." Oh, great! You're launching publicity for a total redesign of the entire global air freight and passenger industry and you've *already* initiated some contacts with the aerospace industry??? Really??? What made you do that so soon??? And looking into hydrogen as a fuel source for this is basically admitting, "It's so far off the page that we might as well throw in any futuristic-sounding crap we can." If you're doing this seriously, get one thing right at a time. Don't complicate it by also trying to introduce a fuel that no-one else has managed to make work yet.

People who consider themselves "aviation visionaries" (yes, an actual term used in the article) always, always get excited about this kind of thing for no good reason. They *think* people want revolutionary concepts that change how they board planes and let them work out then drink themselves silly in a trendy bar while they're in flight. What people *actually* want are revolutionary new concepts that cut the cost of air travel.

Comment You pay WHAT for mobile data??? (Score 3, Insightful) 145

Bloody hell. Here in the newly-independent UK[1], £11 per month gets me 1GB of data, among other things. Another £3 per month turns that into unlimited data. ANOTHER £2 per month turns that into unlimited data with 4GB of data usable by a device tethered to the phone. That's right, £16 per month for unlimited data on the phone and 4GB for tethered devices. "Heightened competitive environment"? Could still use some work, I think. [1] Yes, yes, I know.

Comment Difficulties (Score 1) 324

Two problems I see with this: 1. Safety. If the grid goes away, this thing will have no reaction torque to apply, and it ain't gunna stop in a hurry. 2. Scale. A quick look at Wikipedia suggests that the heaviest goods trains in use anywhere are about 40,000 t. Suppose you have a mountain where you can raise that 1,000m. The energy involved is roughly 40,000 * 1,000 * 10 * 1,000 = 4e+11 J. That's 4e+11 / 3.6e+9 = 111 MWHr. It's not small cheese, but it's also not national grid scale. As I sit at my desk, demand on the UK national grid is ~31GW. It will last 4e+11 / 3.1e+10 = 12.9 seconds supplying the whole country. That 40,000t train is about four miles long, BTW, so there's a limit to how many of them you can put on the same bit of track. As I say, it's not small cheese, but at the same time, in our renewable-powered future, being able to smooth out a few hours of low wind is going to require a lot of trains and a lot of quite large mountains to drive them up.

Comment Re:Cliches (Score 1) 324

I know you meant this to be funny, but you're probably right. For this to work, of course, it has to use regenerative braking to return energy to the grid. So what happens in a grid-fault scenario, when the regenerative braking can't apply any torque to stop the train?

Comment Re:It's wildly unlikely we should exist (Score 2, Interesting) 267

One flaw? Every single sentence in that quote is either false or unknown. Let's review:
  • It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. The universe is not infinite. It may be unbounded (ie have no edges), but that is different.
  • However, not every one of them is inhabited. This one might be true. It is, as far as we know. It might be argued we don't know very much, though. Inhabited with what is not specified.
  • Therefore, there must be a finite number of inhabited worlds. False, as you point out - supposing that the premises are true, the number of inhabited worlds may or may not be infinite.

  • Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero.The first half is true-ish. Certainly the limit as x->infinity of y/x, for finite y, is zero. What relevance this has to the remainder of the sentence is not clear. If the number of inhabited worlds is finite, then so is their population and each populated world will have a finite, non-zero average population. If the number of inhabited worlds is infinite, then so is the total population.
  • From this it follows that the population of the whole Universe is also zero False, since its premises are false. Even if the premises were true, infinity times an infinitesimal number is not zero.
  • and that any people you may meet from time to time are merely the products of a deranged imagination. This depends rather on your personal situation.

Comment Re:AC is by its very nature inefficient (Score 3, Insightful) 245

If you don't understand why this isn't going to happen, you need to be kept away from grid design.

Replacing the AC network with a DC network would mean either replacing or substantially modifying the entire fleet of existing generation plant, all distribution and conversion equipment, all industrial equipment powered by electricity and most appliances. You might well be right that you can achieve better efficiency in a new network with DC than with AC; when you have to replace the entire electricity system, from spinning turbine to phone charger, it just ain't gunna happen.

Comment Re:Efficiency (Score 3, Interesting) 245

Maybe, though Hack-a-Day say it involves an "incredible thermal management solution," which doesn't sound like they've actually bumped the energy efficiency up that much.

Why were Google so keen to have an inverter that maximises power density? Why not maximise energy efficiency?

Ideally you'd like to minimise cost of energy. But I guess it's fairly difficult to construct a competition around this: It depends too much on production scale and the prevailing cost of electricity. But why power density as a substitute?

Comment Re:Largest of its type only (Score 2) 120

...and doesn't require specific large-scale geography to implement.

This doesn't have to get a whole lot more efficient before it could become profitable. If you look at the wholesale electricity market in the UK, the peak cost of electricity is more than double the minimum cost over a week. So something that can store electricity at minimum cost and sell it back into the grid at peak cost only needs to be 50% efficient to be making money. Of course, that's ignoring the capital cost, but still, this is not too far off being profitable.

It's a pretty sad indictment of the state of energy storage, really. It only needs to be 50% efficient to be profitable. If it's profitable, people will do it. Therefore conclude that every practical energy storage system is less than 50% efficient (at least where it doesn't require geography).

Submission + - Ask Slashdot: Simple, Cross-Platform, Video Messaging

DeathToBill writes: I spend a lot of time away from my kids (think months at a time) who are aged 3-8. I keep in touch with them by Skype, but the young ones are not really old enough to concentrate on it and we're often in quite different timezones, so it's not often it can be very spontaneous. We'd like to have some way that we can record short video messages of things we're doing and send them to each other. It needs to have an iPad app that is simple enough for a three-year-old to use with help and for a five-year-old to use without help; it needs to have an Android or web client, preferably one that doesn't require an Apple ID; it needs to be able to record a short video and send it to someone.

As far as I can tell, iMessage requires Apple kit (there is an Android app but it sends all your messages through a server in China...) and Whatsapp works on iPhone but not iPad.

What can slashdot suggest?

Comment Re:Uber/Lyft could probably do this too (Score 2) 92

Not sure if it's just a US thing. In the UK, "click and collect" is available in most supermarkets (and in Australia, for that matter). But then so is web-ordered home delivery.

As I said back when Amazon started trialing this, I think they'll find it hard to compete with the supermarkets. Fresh food can't be stored in a warehouse on one side of the country and posted everywhere; it requires a complex distribution infrastructure, with local stock regularly replenished and without everything passing through a central distribution point to get there. It also requires some well-developed methodology for estimating stock requirements ahead of time. Supermarkets that are regularly out of stock don't do well, nor do ones that significantly over-stock and have to throw goods away.

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