Every Day Is Special: electromagnetic radiation

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March 19 – A Gamma-Ray Bursts the World Record!

Posted on March 19, 2017

Do you know about the dreaded GRB?

A gamma-ray burst is the brightest electromagnetic event known to occur in the universe - a super-duper high-energy explosion. We think that most GRBs are caused by supernovas or even bigger-than-that star-explosions, which are called hypernovas. Scientists speculate that the burst might occur just as the exploding star collapses into a neutron star, a quark star, or a black hole.

Some GRBs might be caused by two neutron stars that had been revolving around each other (in other words, binary stars) finally collapsing together to merge into one star.

Most GRBs are short-lived. Like, really short-lived - just a matter of milliseconds or seconds. After the flash of gamma rays, there is a longer period of "glow," which is made up of less energetic forms of electromagnetic radiation: X-rays, ultraviolet rays, visual light, infrared light, microwaves, and radio waves. A GRB can last as long as several hours.

Gamma rays are very damaging to living things, and a nearby GRB that happened to be pointed at our planet could cause "a mass extinction event." (Think dinosaurs.) But, luckily, GRBs are really rare. Like really, really rare. There may be only two or three in an entire galaxy every MILLION years! The ones we have detected (thanks to our satellites) are billions of light years away.

Today's historical anniversary is for a record-breaking gamma-ray burst that was detected on this date in 2008. What was the record that was broken, you may ask? GRB 080319B is the farthest object that was observable with the naked eye. It had an apparent magnitude of 5.8 and was visible for about 30 seconds.

(Apparent magnitude means how bright the object seems to us. It is a combination of how bright the object really is - the absolute magnitude - and how far away the object is. It's one of those tricky scales - the smaller the number, the brighter the object is, because ancient Greeks classified the brightest stars in the night sky as 1 and the dimmest stars visible as 6. The Sun is - 26.7 (notice that is a negative number!), the Moon is - 12.6, Venus is -4.4, and the brightest nighttime star, Sirius, is -1.4.)

Note that the GRB is, at 5.8, only barely visible to the human eye. On a really clear night with no light pollution, there were still thousands - maybe around 4,000! - stars brighter than this gamma-ray burst was, back in 2008. A tiny pebble burning up in our atmosphere (a "falling star") would have been more noticeable that night.

But that's still amazing - because the GRB was 7.5 BILLION light-years away from us. When the electromagnetic radiation started traveling Earthward, there was no Earth, and there was no Sun. Our solar system wouldn't form until the GRB was about halfway to us!

W - O - W!

Also on this date:

Sydney Harbor Bridge's birthday

Artist Betty Goodwin's birthday

Saint Joseph's Day in Valencia, Spain

Battle of March 19 in the Dominican Republic

Swallows Day at Mission San Juan Capistrano

Anniversary of the discovery of electric eels

National Quilting Day

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February 28 – National Science Day in India

Posted on February 28, 2016

One of India's most recognized and respected scientists is C.V. Raman.

I like referring to him as “C.V.” because his full name is Chandrasekhara Venkata Raman. Which is a lot to type.

On the other hand, like Charles Darwin and Albert Einstein, at least spell check know's Raman's full name and didn't allow me to accidentally type something like Chardrasekhara or Chandrasakhara or....whatever else my flying fingers blundered out.

And since 1929, Raman's full name ALSO included “Sir,” because he was knighted by Britain.

So, why am I bringing up Sir Chandrasekhara Venkata Raman today? Just because he was an Indian scientist and today is National Science Day in India?

Actually, it is because of Raman that today was chosen to celebrate and promote science in India – because today is the anniversary of his most important, Nobel-Prize-worthy discovery: the Raman effect.

So...what's the Raman effect?

Simply stated, the Raman effect is the inelastic scattering of light.

You probably know that visible light is a form of electromagnetic radiation, along with infrared, microwaves, X-rays, radio waves, and ultra-violet light. All electromagnetic radiation travels in little “packets” called photons.

I bet you have heard that, on a clear day, the sky looks blue because of scattering. But what is being scattered by what?

Air is not empty space – it's full of lots of different particles and molecules, most of which are invisible to us. When light from the Sun hits particles or molecules, some of the photons's paths are disrupted, and the various photons scatter about randomly. And blue photons have the tiniest wavelengths of all visible light, so they tend to get scattered more than green or yellow photons, and especially more than orange or red photons.

This is called Raleigh scattering, or elastic scattering. The photons that scatter shoot off on other, random paths, but they don't change their frequency and wavelength. In other words, a photon of blue light stays a photon of blue light.

In 1923, a physicist predicted that a few photons would scatter in another way. They would scatter by excitation – in other words, they would change frequency and wavelength, either gaining or losing energy. A photon of blue light might become a photon of red, or vice versa.

In the diagram above, the incoming Sun's light is yellow,
as is the Raleigh-scattered light. The two pink arrows
show the Raman-scattered light.

In the diagram above, the green laser shines through a crystal.
Some of the light is scattered. Most of the scattered light is
still green (Raleigh - elastic), but a bit of it is now pink
(Raman - inelastic).

On this date in 1928, Raman and K. S. Krishnan discovered the predicted behavior. Only about one photon in 10 million changes wavelength as it scatters, but they were able to observe it as light passed through a liquid.

(Actually, two Soviet scientists discovered this same sort of scattering as light traveled through crystals about a week before Raman and Krishnan's discovery! The reason that the “effect” is named after Raman – and the reason that Raman and Krishnan share a Nobel Prize for the discovery – is that the Indian scientists published their findings before the Russian scientists did.)

In 1928, the Raman effect seemed important to scientists, especially those in the field of spectroscopy (the study of light that has been emitted from, reflected from, or shone through a gas, liquid, or solid). But I don't know that the Raman effect had much...um...effect on the rest of us. However, these days there are a lot of utilities in many different fields. Here's a practical one: a Raman scanner is a hand held device used to detect drugs, explosives, hazardous chemicals, gases, and so forth. It is used by narcotics squads, airport security, forensic detectives, and security experts.

For more...

Check out this article on other Indian scientists.

Also on this date:

International Sword Swallowers Day

Kalevala Day in Finland

National Tooth Fairy Day

Andalusia Day in Spain

French Scientist Day

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February holidays
February birthdays
Historical anniversaries in February

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November 20 – Happy Birthday, William Coblentz

Posted on November 20, 2014

William Coblentz, born in Ohio on this date in 1873, didn't finish high school until he was 22 years ago.

You might assume that means that he wasn't all that bright. If so, you'd be wrong! Coblentz's family was economically disadvantaged, and he had to work and help provide rather than study and earn credits for graduation. But eventually, graduate he did – and Coblentz ended up earning BS, MS, and PhD degrees in physics from fine universities!

And he accomplished a lot in his science career, with hundreds of scientific publications, talks, and abstracts, plus ten patents.

One of the things that Coblentz is best known for was his work on infrared radiation (IR).

Do you realize that all sorts of things that people do not consider “light” – radio waves, x-rays, microwaves – are actually the same sort of phenomenon as visible light? All of these are forms of electromagnetic radiation (EMR) that travel at the same speed (yes, it's called “the speed of light”) and that share other characteristics. All these forms of radiation travel in “packets” or particles called photons. And the different forms of EMR differ only in their frequency and wavelength.

Infrared “light” is not visible to the naked eye. It has longer wavelengths (and lower frequencies) than the red visible light – hence its name infrared. This kind of radiation can be released as heat, and people using infrared scopes and sensors can see and photograph living things that shine brighter than cooler nonliving objects.