Photo Contest IV: Finalists, Lab Rats

| 13 Comments

We received approximately 30 photographs from 14 photographers. Most of the pictures were excellent. We divided the entries into 2 categories, Lab Rats and General, though we had to fudge a little bit to populate both categories.

Choosing finalists was difficult. We considered what we thought were the scientific and pictorial qualities of the photographs, and also attempted to represent as many photographers and present as much variety as possible. The text was written by the photographers and lightly edited for consistency.

Here are the finalists in the Lab Rats category. Please look through them before voting for your favorite. You will have to be logged in to vote on the poll. We know it is possible to game these polls. Please be responsible and vote only once. If we think that the results are invalid, we will cancel the contest. The photos and poll are below the fold.

The winner in each category will receive an autographed copy of Among the Creationists, by Jason Rosenhouse, which received a very favorable review here. We are indebted to the author for his generosity in providing the books.

Acknowledgement: Reed Cartwright wrote the HTML code.

  • New species of orchids of the genus Teagueia, by Lou Jost—Volcan Tungurahua, Ecuador. The photographer and his students discovered a remarkable and completely unexpected evolutionary radiation of these plants, with up to 16 sympatric new species on a single mountain.
  • Two-headed Xenopus laevis tadpole generated by the injection of RNA encoding plakoglobin (g-catenin) into a fertilized egg, by Mike Klymkowsky. The melanocytes are contracted and extended pigment distributions in the two axes. More information.
  • Banded iron formation—Jasper Knob, Ishpeming, Michigan, Proterozoic eon, ~2.11 Ga, by James Kocher. Kodachrome 64, August, 1992.
  • E. coli by Ryan Kitko.—On the right, a test tube with Escherichia coli that appear green because they contain a plasmid to produce green fluorescent protein (GFP). The middle test tube contains the same bacteria but appears cloudy because it is missing the inducer arabinose. The left test tube is a control containing only growth medium.
  • Light bulb imploding inward, demonstrating that the pressure inside the bulb is less than atmospheric pressure, by Steve Switaj. Photograph was taken ~30 years ago on Kodacolor 100 with two flash units and an exposure of approximately 1/40,000 s.

Which photo best captures both artistic and scientific beauty?

View results

13 Comments

Hey, two of those have bits of modern technology in the picture!

Therefore design!!!1111!!!eleven!!!!!

Hard to choose. I wanted to vote for the banded iron formation because it’s not often that Ishpeming gets into the news outside Michigan. But I went for the orchids. Gerry L

Is it just me, or do most of those orchids look like naughty body parts?

They are shocked and dismayed to think they are naughty when they are such good specimens.

I’ve seen a few good specimens of naughty things.

I should probably take a moment to explain the photo of the light bulb, since it’s a pretty odd subject for a blog mostly concerned with biology.

As I told Matt, his topic was “lab rat”, so I thought I should submit this photograph since its subject was, in fact, an experiment.

I took it 30 years ago when I was a junior in high school, to settle an argument that came up in physics class.

Light bulbs were alleged to contained a vacuum and the question was, if you smashed a bulb, what exactly happens? Does the bulb explode from the fracture, shattering outward, or does it implode from external air pressure, collapsing inward?

To answer the question I did what any 16 year-old would do. I smashed a pile of burned out bulbs I got from the school janitor.

I built a rig using two electromagnets to drop a pair of ball bearings when I interrupted the current. One ball fell on the bulb, the other dropped on a leaf switch which triggered a pair of electronic flashes set to the shortest flash possible. By adjusting the height of the switch I could pick the exact moment the flashes went off.

I set up the bulb in a large cardboard box to control the shrapnel a bit, with some holes cut for the lens and flashes. I turned out the lights, opened the shutter, and dropped the balls.

80 times.

As it turns out, light bulbs implode, as can be seen clearly by the area under the bearing. Here the bearing has just struck the bulb, and the cracks are propagating out through the bulb body. The area directly under the bearing is shattering into small pieces and this material is being sucked into the hole.

In retrospect, this should have been obvious. Even though I eventually found out that bulbs only contain a partial vacuum, they have a good amount of surface area, so the external forces are enormous. The shards of glass are thin and light, so in the instant after a bulb is broken the pieces have a lot of force pushing them in, and only a little momentum driving them outward. Air pressure wins.

Sadly, my efforts would not win the science fair that year ( Damn you Mike Stallo and your carefully sorted shale fossils! ).

The camera details, such as I can recall after 30 years, were: Camera, Canon AE1: lens Vivitar 70-210 macro zoom: Film Kodacolor 100: exposure by two Vivitar 283 flash units, appx 1/40,000 sec.

After a little experimentation I found I was getting more than one flash as the switch bounced when struck, and I needed to add a small circuit to limit the switch to one closure.

Just Bob said:

Is it just me, or do most of those orchids look like naughty body parts?

Ironically, the Ancient Greeks thought the tubers of Orchis sp looked like testicles, hence the name “orchid.”

In retrospect, this should have been obvious. Even though I eventually found out that bulbs only contain a partial vacuum, they have a good amount of surface area, so the external forces are enormous. The shards of glass are thin and light, so in the instant after a bulb is broken the pieces have a lot of force pushing them in, and only a little momentum driving them outward. Air pressure wins.

At a guess, the reduced pressure inside the bulbs is probably a safety precaution, since otherwise bulbs taken to higher elevation than where they were manufactured would have greater pressure inside than out.

BTW, is the gas inside the bulb an insert or mostly insert gas? (nitrogen, maybe?)

Henry

Henry J said: At a guess, the reduced pressure inside the bulbs is probably a safety precaution, since otherwise bulbs taken to higher elevation than where they were manufactured would have greater pressure inside than out.

BTW, is the gas inside the bulb an insert or mostly insert gas? (nitrogen, maybe?)

Henry

Actually, I think the partial vaccum inside the bulb is about preserving the life of the filament.

I actually ended up looking into this pretty deeply at the time. I contacted some of the large manufacturers and they were surprisingly helpful with information. One of them even had an engineer call me back, which was a great thing for a 16 year old kid working on a science fair project..

It’s been a while, but I think that the deal was that the early bulb pioneers quickly found out that you can’t have oxygen inside the bulb or the hot tungsten filament will quickly oxidize itself to death.

So they tried a vacuum, but that didn’t work either. If you have a true vacuum the filament will slowly evaporate, eventually depositing itself on the “cool” inner surface of the bulb as a dark metallic film. A true vacuum also leads to a heavy bulb and it’s difficult to get a good hermetic seal, so eventually atmospheric gas tended to seep inside, limiting shelf life.

The compromise is filling the bulb with a small amount of inert gas, the partial pressure of the gas is just enough to keep the tungsten atoms from boiling away, but there’s not enough atmosphere to react. The glass envelope can be lighter, and the seals are less critical.

One interesting thing I learned, the “atoms boiling off” thing is still an issue in larger lamps, and sometimes when you examine something like a big theatrical lamp there will appear to be a tiny amount of sand in there. This is a apparently a “getter” material that reacts with any tungsten vapor and captures it before it can deposit on the glass.

The Edison bulb was indeed made using a “true vacuum,” taking out as much atmosphere–and thus oxygen–as possible. Carbon filaments and vacuums, at around 3 lumens per watt, it still was rather better (and certainly safer) than gas light.

Edison actually mentioned the possibility of using inert gas to keep the filament from subliming so quickly, but apparently it was harder to put inert gas in than to simply evacuate the bulb. It shouldn’t be forgotten that using a gas instead of a vacuum actually means that you end up with convection losses that don’t exist in the vacuum–however, light output increases so much with increasing temperature (which doesn’t sublime the filament so quickly with gas pressure slowing the process) that it pays to put gas in rather than using a vacuum. Tungsten filaments, helped a great deal as well, for although carbon remains a solid at higher temps than does tungsten, the latter has a lower vapor pressure at filament temperatures.

So why a partial vacuum in bulbs, instead of high pressure gas–which would prevent the filament from evaporating even better? Well, halogen bulbs actually do use higher pressure gas than a regular bulb in their tiny bulbs (often surrounded by a much larger protective bulb), but at operating temps they’re rather liable to break, and are thus banned from some residences like dorms. Regular bulbs need a partial pressure at room temperature because when the bulb is hot the pressures increase greatly. Without partial vacuum at low temps, you’d have an over-pressure bulb at high temps, which could explode glass shards into your eyes, etc.

At least until recently there were still small, low-wattage bulbs made with vacuums instead of inert gas. Incandescent Christmas tree lights, I believe, often had a “real vacuum” instead of inert gas. I don’t know the manufacturing economics of it, however I believe it was just because it was cheaper to do it that way, and how long do you use Christmas tree lights anyhow? So they were particularly low efficiency, run at low temperatures that wouldn’t sublime the tungsten too quickly and thus burn the bulb out. LED lights are a nice change on both efficiency and life of Yuletide light strings.

Glen Davidson

BTW, is the gas inside the bulb an insert or mostly insert gas? (nitrogen, maybe?)

Nitrogen was first used, now it’s mostly argon with some nitrogen included to keep it from being too conductive (noble gases conduct electricity much more than N2–witness neon lights). Why not just nitrogen, which is cheaper than argon? Because argon has a higher molecular weight, and this helps to keep the tungsten filament from evaporating better than N2.

Krypton and Xenon are used in some bulbs, since, being even heavier than argon they do a better job of keeping the tungsten from subliming. Halogen bulbs, I believe, mostly use xenon (probably krypton is sometimes used), and I think at operating temps it’s 5 atmospheres or so. That’s why halogen bulbs (not the protective bulb) are so small, xenon is expensive, and would be costly in a large bulb. The halogen redeposits tungsten on the filament, which does almost nothing to extend the life of the bulb, primarily keeping the dark tungsten film that covers old regular bulbs from covering the little bulb (it would darken very fast without the halogen) and impeding light emission.

Both the pressure and the heaviness of the gas in halogen bulbs allow for higher operating temps and somewhat higher efficiency–although because they’re expensive, heavier tungsten filaments are used to extend the life of the bulb, thus sacrificing much of the efficiency gains to keep from replacing expensive bulbs too often.

Glen Davidson

Yes, the resemblance of the orchids to a certain body part has been noted before.…when I showed the first photos of these flowers to a famous orchid taxonomist, he called them “orchid pornography”.…

The Masked Panda pointed out…

Regular bulbs need a partial pressure at room temperature because when the bulb is hot the pressures increase greatly. Without partial vacuum at low temps, you’d have an over-pressure bulb at high temps

Doh!

OK, you can call me Captain Overlooks-The-Obvious now.

In retrospect it all makes perfect sense. When you turn the lamp on, the gas inside the envelope goes from room temperature to maybe 1000+ degrees.

Since the volume is constant its pressure has to increase maybe three fold.

If you didn’t start with a partial vacuum, you’d be setting up for little tiny glass grenades all over the land.

After 30 years the mystery is solved.

Thanks, Glen.

About this Entry

This page contains a single entry by Matt Young published on October 29, 2012 12:00 PM.

Freshwater: His Reply Brief was the previous entry in this blog.

Royal Society journals open access is the next entry in this blog.

Find recent content on the main index or look in the archives to find all content.

Categories

Archives

Author Archives

Powered by Movable Type 4.38

Site Meter