Category Archives: Tech

Lethargic Time Flies

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With Earth spinning more slowly, time isn’t flying as fast as before

CHalk this up as another example of an article title not really matching up with what the article concludes. It’s misleading — as the story eventually alludes — because we now use atomic time, so there is no slowing of time. The rate is the same. The explanations of the variability of earth rotation rates have implications on leap seconds, which we add to keep earth rotation time (terrestrial time) in synch with atomic time. We can’t adjust the earth, so we adjust the clocks.

GPS figures prominently in the discussion of technology enabled by atomic time, but there’s an omission in the discussion:

“If we relied on the Earth’s length of day, we could not have any of this,” says O’Brian, whose group at NIST develops, maintains and improves the supremely regular atomic clocks on which all other timekeeping ultimately is based.

GPS is actually synched with Naval Observatory time, and while USNO time and NIST’s time agree to great precision, to say “on which all other timekeeping ultimately is based” is a bit of hyperbole — it makes it sound as if others are adopting technology only after they develop it, and that the international time standard follows NIST, instead of the other way around. Timing labs around the world follow the international standard from BIPM, to whom we all contribute data. (Some of us contribute more than others. And some of us are closer in realizing the international standard.) /ChestThumping

“We have come full circle,” O’Brian says. The rotation of the Earth had long been the most accurate measure of time for humanity, but now such technologies as atomic clocks and GPS devices make it possible to measure tiny variations in Earth’s rotation. And the scientific reverberations are not just for space junkies. In a July paper in the journal Nature, for instance, researchers in England and France argued that sub-millisecond-scale variations in Earth’s rotation that occur on a 5.9-year cycle are probably linked to motions and interactions within the planet’s molten core where no one has ever been to take a look.

I think it’s pretty cool that our timekeeping is such that we can uncover evidence of processes that are redistributing mass inside the earth.

Floating Some Ideas

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What It’s Like To Spend 55 Days in Space

Moreover, it’s not clear that private space initiatives are the answer to the problem. “Space exploration is not an immediate payback, fiscally or otherwise,” Ivins says. “It is a generational kind of investment. And the only group that can afford to make that kind of an investment is a government.”

This is not exclusive to NASA, it’s true of research in general.

Plus, for the benefit of geeks across the universe, Ivins explains why the Borg cube from Star Trek can maneuver just as well as any starfighter that Hollywood has ever dreamed up. “In space, they’re one and the same,” says Ivins.

This is probably the one bit of science that space-based science fiction gets pretty consistently wrong — that maneuvering a craft in space would be anything like a plane or even a submarine. Most of the time the engine exhaust only points to the rear, and the engines are firing even when traveling at constant speed. Which is wrong even before you get to the fancy maneuvering.

This Claim Won't Fly

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One of things I like to do, as you know, is to run an order-of-magnitude calculation when I see a claim that seems off, to see if it’s plausible.

The future of flight: Shape-shifting engines and body heat power

This claim caught my eye

Tan Kai Jun, the team leader, envisions cabin seats upholstered with a thermoelectric fabric that can convert a person’s energy into 100 nanowatts of voltage. Alas, that amounts to about one-millionth of what your iPhone needs to stay on standby. Still, Jun maintains that it does ultimately add up.
“It’s a small amount, but imagine this collected from 550 seats throughout 10 hours of flight. A plane has a lifespan of a few hundred flights — over time that’s a big reduction,” he says.

This one’s pretty easy. Ignoring that nanoWatts is a power, not a voltage, let’s assume a 10 hour flight. That gets you a total of 1 microWatt-hour per passenger. Let’s be generous and assume 1000 flights, which gets you to a milliWatt hour. Another further generous assumption of 1000 passengers gets you to a Watt hour. I think you can see where this is going. US grid electricity costs around ten cents per kiloWatt-hour. Even if we assume that the cost of electricity on a plane is ~100x more than commercial US electricity, because of the inefficiency, this system will save, at most, a penny over the lifetime of the plane. If the components and installation are free, that is, and the weight of the system costs no additional fuel.

So, not a big reduction.

Charge!

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Teen’s invention could charge your phone in 20 seconds

Waiting hours for a cellphone to charge may become a thing of the past, thanks to an 18-year-old high-school student’s invention. She won a $50,000 prize Friday at an international science fair for creating an energy storage device that can be fully juiced in 20 to 30 seconds.

Maddening omission of what the capacity of the system actually is, because this is great, if it actually works as advertised. There is the implication above, that it’s the same capacity as a phone battery, but that’s contradicted in other stories. Which means we don’t know if this will scale up or end up on the list of failed promises, like those room-temperature superconductors on mag-lev trains we were promised were imminent, back in the 90’s.

This report implies that it’s not ready for that just yet.

Her experiment used the supercapacitor to power an LED, but both Khare and Intel believe the same tech can be used to similar effect on a smartphone.

Powering an LED is a far cry from powering a phone. The article doesn’t say how long the LED ran. Several hours? Or just a few minutes?

The INTEL press release is even more confusing.

She developed a tiny device that fits inside cell phone batteries, allowing them to fully charge within 20-30 seconds.

It’s being used to fully charge a battery? That doesn’t make sense. A cell phone battery’s capacity is around 1500 mAh at around 3.7 V. Charging it in 30 seconds would require ~670 Watts, though it’s 180 Amps at 3.7V (but under 6 amps at the wall outlet). The obstacle isn’t the availability of the raw power to the battery, it’s efficiently delivering the charge to the battery without melting anything, including the battery, so without modifying the battery you still run into the problem of the battery not “liking” to be charged quickly — they tend to get hot. It makes more sense that this would be used as a substitute for (or an auxiliary to) the battery, and the supercapacitor is what can be charged quickly.

If it can be scaled up.

Pete Townshend Physics

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Ciudad Blanca, Legendary Lost City, Possibly Found In Honduran Rain Forest

Ciudad Blanca, or “The White City,” has been a legend since the days of the conquistadors, who believed the Mosquitia rain forests hid a metropolis full of gold and searched for it in the 1500s. Throughout the 1900s, archaeologists documented mounds and other signs of ancient civilization in the Mosquitias region, but the shining golden city of legend has yet to make an appearance.
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“We use lidar to pinpoint where human structures are by looking for linear shapes and rectangles,” Colorado State University research Stephen Leisz, who uses lidar in Mexico, said in a statement. “Nature doesn’t work in straight lines.”