Category Archives: Physics

Wisdom From Inigo

Posted on by

You keep using that word. I do not think it means what you think it means.

Newly born identical twin stars show surprising differences

The identical twins were discovered in the Orion Nebula, a well-known stellar nursery, that is 1,500 light years away. The newly formed stars are about 1 million years old. With a full lifespan of about 50 billion years, that makes them equivalent to one-day-old human babies.
[…]
By measuring the difference in the amount that the light dipped during the eclipses, the astronomers were able to determine that one of the stars is two times brighter than the other and calculate that the brighter star has a surface temperature about 300 degrees higher than its twin. An additional analysis of the light spectrum coming from the pair also suggests that one of the stars is about 10 percent larger than the other, but additional observations are needed to confirm it.
“The easiest way to explain these differences is if one star was formed about 500,000 years before its twin,” says Stassun. “That is equivalent to a human birth-order difference of about half of a day.”

So they have different brightness, surface temperature and possibly size. Maybe we shouldn’t be using the baby analogy (it’s not like they share DNA) and should stop calling them identical twins.

Update: Scientific Blogging does a better job, calling them fraternal twins, but the link has an auto-starting video with no means (that I can find) to turn it off!

The Necessity of Mathematics

Posted on by

Awesome megapost over at Science after Sunclipse, covering many overlapping issues on the topic.

To use mathematics in the natural sciences, we first decide how we wish to represent some aspect of the world in mathematical form. We then take the diagrams and equations we’ve written and manipulate them according to logical rules, and in so doing, we try to make predictions about Nature, to anticipate what we’ll see in places we have not yet looked. If additional observations corroborate our expectations, then we’re on the right track. (It’s rarely so clean-cut as that — the process can spread across thousands of people and multiple generations of activity — but that’s the gist of it.) Several skill sets are involved: one must know how to idealize the world, and then how to work with that idealization. Remarkably enough, our schools fail to teach either skill.

It's So Big! It's Just So Big!

Posted on by

A splash of astronomy news. Astronomers create first four-continent telescope

Astronomers have long combined observations from individual telescopes. The process, called interferometry, produces the same resolution as a single dish as wide as the distance between the antennas.

Recently, the Arecibo Observatory in Puerto Rico joined a project called Electronic Very Long Baseline Interferometry (e-VLBI), which can make temporary radio telescopes that rival the size of the Earth.

Crime Scene Investigation Investigated

Posted on by

I stumbled across a dead body couple of posts over at Quantum Moxie on the thermodynamics of post-mortem cooling of a body: Mistakes were made . . . and the followup, Post-mortem body cooling in variable environments.

[T]he standard post-mortem body cooling method used to estimate time of death (TOD) does not take into account a varying environmental temperature (i.e. it assumes a constant ambient temperature when applying Newton’s Law of Cooling).

And since were on the subject of physics and dead bodies, Zapperz notes a brouhaha about a physics exam question involving a gunshot victim and bullet trajectories.

"Classic" Timekeeping, Part III

Posted on by

Part I, Part II

Timekeeping measurements always rely on the comparison of two oscillators; when you check to see if your clock or watch is running fast or slow, you do this by comparing it to another clock. Finding disagreement between two clocks won’t tell you a priori which one is the culprit, just as in the adage that a man with two clocks is never sure what time it is. But comparing three clocks allow pair-wise comparisons, and begin to allow one to assign a stability to the individual clocks.

Comparisons are what the scientists did in the second paper in my review, “Time, Analysis of records made on the Loomis chronograph by three Shortt clocks and a crystal oscillator.” The quartz crystal oscillator gave the input to the Loomis chronograph, and the three Shortt clocks were compared to crystal, and could then be compared with each other by differencing the data, which removes the crystal from the measurement.

The interesting (to me) part of the paper begins a few pages in, where they begin discussing the influence of the moon. The moon should give rise to a change in amplitude that would occur over an interval of 24h 50m, and should be distinguishable from diurnal terms present in the pendulum clocks. Two different time series were analyzed, one having a duration of 54 days, and the other having a duration of 146 days. This was long enough to average out noise terms, since the preliminary estimate of the effect was 153 microseconds per half-period of oscillation (i.e. one second)

The theory of the effect of direct attraction is presented in terms of tidal potentials, and it, of course, ends up depending on the angular position of the moon and the latitude of the observer. There are secondary effects as well. The tidal effect of the moon is not only on the water, but on the solid earth as well, though because it is not particularly elastic, the earth’s deflection is smaller, and this changes the radius by a small amount. There is a redistribution of mass when this occurs. Further, there are the local effects of the depression of the ocean bed and coast at high tide (as this was fairly near new York City), and the change in mass that occurs because of the water. It turns out that these indirect effects very nearly cancel, and the results should be close to the 153 microseconds predicted by direct attraction.
Continue reading →

Shakin' it Here, Boss

Posted on by

Chladni Plate using salt.

You might want to turn the volume down — it starts to get pretty annoying about halfway through, as the frequency goes up, and you may be summoning all the dogs in the area.

You need to a flashplayer enabled browser to view this YouTube video

Some Chladni solutions for a plate constrained at the center.

Popcorn Update

Posted on by

Via Built on Facts, it turns out that the cellphone-popping-the-popcorn movie was A FAKE! Gasp, thud. Making popcorn with a cellphone happens only in the movies.

(or should that be “only happens in the movies?”)

More than 6 million people have watched our little videos since May 28, 2008. We are very happy to have made this contribution to an important international public debate.

Important international public debate? Jane, you ignorant slut.

Getting My Pants On

Posted on by

A lie gets halfway around the world before the truth has a chance to get its pants on. Churchill, inspired by Twain, pre-internet.

Genepax Unveils a Car That Runs on Water and Air

Try again, you sensationalizing hacks. Versions of this story have spread across the web like a bad rash.

Their new “Water Energy System (WES),” generates power by supplying water and air to the fuel and air electrodes using a proprietary technology called the Membrane Electrode Assembly (MEA). The secret behind MEA is a special material that is capable of breaking down water into hydrogen and oxygen through a chemical reaction.

If there’s a chemical reaction taking place, then it’s not running on water and air!

As said in the press release

The main feature of the new system is that it uses a membrane electrode assembly (MEA), which contains a material that breaks down the water to hydrogen and oxygen.

Got that? It contains a material that breaks down the water to hydrogen and oxygen. There’s a chemical reaction going on, for Odin’s sake! There are materials that like Oxygen even more than Hydrogen does. Introduce them, let them get acquainted, and they’ll get busy producing Hydrogen. But — and this is very important — the other material will eventually run out, and you’ll have to “refuel.”

To give an example, you can generate Hydrogen with water, Aluminum and Gadolinium (the latter is a catalyst which keeps the Al from forming an oxide layer, which would shut the reaction down, and the reaction is not exactly a “new process”). I don’t know if this is what’s going on here, but something sure is, because in this house we obey the laws of thermodynamics.

Update: good takedown over at Good Math, Bad Math

It's Kinda Like 'Where's Waldo?'

Posted on by

Volunteers asked to help find dead spacecraft on Mars

HiRISE software developer Guy McArthur, also at the University of Arizona, has invited the public to scan these images for signs of the Mars Polar Lander. It’s a huge challenge because although there are only 18 images, each of them is enormous – typically 1.6 billion pixels.

“If your computer screen is 1000 by 1000, that means you need 1600 screenshots to view one image,” says McEwen. “On the HiRISE team, we haven’t put much effort into looking for this – we’re too busy with other things.”

h/t to CD