Posts by Alan Jenney

Units of power cf. units of energy

I have to agree with Olof P and the anonymous post...

A Watt Hour (Wh) is a unit of energy, not power. Domestic electricity meters record the energy you use in kWh (kilo Watt hours). The Watt is a unit of power, which is energy consumed over a period of time.

It's not logical to say watts per hour (watts/hour) i.e. "300 watts in one hour" any more than it is to say the solar cells produced "300 Watt-hours" of power.

It would make more sense that the power systems can store 300Wh of energy per day, as can be read in the article at:

http://www.nasa.gov/mission_pages/mer/mer-20070824.html

MachineID - been there, bought the T-shirt

I could have sworn that Intel had created a unique identifier code that was in each individual chip and difficult to forge, but the clamour amongst privacy and rights enthusiasts led to it being switchable - and defaulting to the "off" state.

Now we want security instead of privacy. There's got to be a balance somewhere.

Light travels below the speed of light (photons vs. waves)

Light is sometimes called a wave, when it's convenient to consider it as electromagnetic radiation. Photons are what light is called when it's convenient to consider it to be made of discreet particles*. So take your pick.

In the near vacuum of intergalactic space, light travels at the quoted "speed of light". The furthest parts of the visible universe are travelling away from us at less than, but near the speed of light, which is why we can see it. If we look in the opposite direction, the furthest parts of the universe are travelling away from us at near the speed of light, so you'd think RELATIVELY, the opposite ends of the universe are travelling away from each other at nearly twice the speed of light. But they don't: a guy called Albert E. went over all of this some time ago. The "Special Theory" explains it succinctly.

On earth, unless in a perfect vacuum, things tend to get in the way and slow the light down a bit and can absord it completely. Create a special sort of super-cold physical state of an element and you can get light to drag its feet in a controlled way.

Fears and disclaimers

Americans want eco-cars, however much a misnomer that is. A lot of existing infratructure has evolved over the last 100 years to accommodate and then necessitate the use of cars. An electric car is not necessarily the answer, whether it is charged from the mains or derived from fuels ranging from petrol to hydrogen. Putting that to one side, let's look at the electric car in general.

The fears over high-voltage batteries are largely unfounded. Let's face it, nobody seems very concerned about carrying gallons of highly flammable gasoline around in their petrol cars. Similarly, if hydrogen leaks, it doesn't create the same vapour risk as petrol - it burns gently with a blue flame. Rupture of a pressure cylinder containing hydrogen is much less likely than a regular fuel tank. Admittedly, the presence of high voltage is not obvious. However, if there's something wrong with the car's powerplant and transmission, it probably going to be simply loaded onto a transporter, not diagnosed at the roadside.

With any (recently) unproven technology there are bound to be some teething problems with control systems, the honesty about this has possibly not generated the best press. Telsa need to be absolutely confident in their product before handing them over otherwise their business will fail.

As for the rechargeability of laptop batteries, if you leave your laptop plugged into the charger all the time and rarely run it on batteries, it will quickly lose its capacity. I tend to run my three-year-old laptop down and recharge each day and it still lasts at least two hours. Similarly with the car - in fact, you cannot leave it plugged in whilst driving, so you are require to partly discharge it with each use!

The batteries will be the most expensive part of the car. Other electric vehicle start-ups like www.think.no are considering leasing the battery at a low rate (including insurance and a contract with countrywide breakdown services) rather than saddling the owner with the risk and cost. As for the idea that charging is inconvenient - you won't be spending 24/7 in the car, so charging overnight and keeping it topped up means that you won't ever need to visit a charmless filling station again!

From a bloke on a waiting list.

Picture reportedly from 2004 expedition

RE: Anyone seen it?

http://www.physorg.com/newman/gfx/news/Tunguskaevent-anartifact.jpg

Looks like a bit of more recent space junk to me...