Astronomer studying star formation, like myself, use telescopes that can see though the pretty optical exteriors of nebulae into the interiors, where very cold dust radiates in the submillimetre and microwave regimes.

Microwaves, fall on the electromagnetic spectrum, between radio waves and infrared waves. They are usually around the size of a few centimetres and you may well be very familiar with them as they are produced by the microwave oven that might just be sitting in your kitchen.

Microwave ovens use a particular microwave frequency to excite molecules of water. Since water is present in lots of food and drink, this means that microwaves heat up lots of useful stuff - and they do it quickly. The fact that microwaves are now readily available to most of us in the western world and they are only a few centimetres in length, means that you can measure the speed of light in your very own home.

What You Need:

The quickest and tastiest way to perform this little experiment is with marshmallows, but chocolate chips also work. You’ll obviously need a microwave oven as well, and a large, microwaveable dish. You will need a ruler, too.

What to Do:

Get your large, microwaveable dish and place a layer of marshmallows at the bottom of it.Remove the turntable from the bottom of the microwave oven. If you don’t, then this experiment will not work at all. If your microwave doesn’t have a turntable, it means that the turning mechanism is elsewhere and you’ll need to find a regular microwave oven to try this experiment.

Cook the marshmallows on a low heat for a couple of minutes, or until you see parts of the marshmallows starting to bubble. When you do, remove the dish and take a look at the marshmallows.

You ought to see that they have not melted evenly. In fact you should be able to see a regular pattern has formed, drawn out in melted-mallow. It depends on your microwave oven, but you should see a melted/unmelted pattern across the dish in some direction. When I tried it at home, my oven created long melted strips next to long unmelted strips (see above).

This regularity is caused by the same mechanism that heats up the food you place into your microwave oven. The appliance generates microwaves which very quickly form standing waves (see animation above) inside the cavity inside, where you put food. As the food rotates around, it passes through the standing wave nodes and this excites the water molecules, heating the food.

Measure the Microwaves:

Take your ruler and measure the distance between the melted parts of the marshmallows. You should find that there is an even pattern of melting and that the distance between them is something like 5 or 6cm. Why? Because that is the distance between the nodes of the standing waves.

Without the rotating mechanism, the food does not move around and cook evenly, instead it just heats at the nodal points. Using your marshmallows you have created a ‘map’ of the microwaves in your microwave oven!

Find the Frequency:

Finally you need to know the frequency at which your microwave oven operates. It is usually written on the back somewhere in small writing. Most standard microwave ovens operate at 2450 MHz. If you cannot find the value on the back of the oven, you can take it for granted that 2450 MHz is about correct.

Measure the Speed of Light:

Now you have what you need to measure the speed of light. You just need to know a very fundamental equation of physics:

Speed of a Wave (c) = Frequency (f) x Wavelength (L)

The distance between the melted sections of the marshmallow is in fact L/2, because there are two nodes for each wave (see animation). So if you have measured 6cm and your oven operates at 2450 MHz, then your measured speed of light is (0.12 x 2450,000,000) 294,000,000 metres per second.

The agreed value of the speed of light through a vacuum is 299,792,458 metres per second. See how accurately you can measure it? what could you do to make the experiment better, and thus get a closer answer?

Now You Can Eat the Gooey Melted Marshmallows:

…and make yourself sick. Yay!

I had a question via email asking about Comet Holmes. I thought that by answering it on the blog, maybe others would also have some questions answered. so, thanks to Marycie for her question.

Comet Holmes was a very dim, and expected comet. Until October last year. During the period October 23rd to 24th 2007, it suddenly brightened. If you want to know more about why it suddenly became visible, I’d recommend reading Astroprof’s post on Integrated Magnitudes.

The comet was visible to the naked eye after that date, and on about the 26th of October it began to look more like a classic comet, with a tail and nucleus. Comets have a nucleus, a tail and a coma, or halo. The nucleus is the hard, chewy centre. This is rocky bit and really ‘is’ the comet, if you like. The tail and coma are produced when the object passes closer to the Sun and particles of ice and dust begin to sublimate. A cloud of material (the coma) appears to boil off the nucleus and becomes the glowing, cloudy ball that makes comets familiar to most people.

The tail is produced by interaction with the Sun. Particles from the coma and nucleus are blasted back from the comet by the Sun and so the tail always points away from the Sun.

Comet Holmes’ coma grew enormously in size and this became interesting later on in October. Late in the month, the coma had grown to be about half the width of the Moon on the sky. However it was lying about twice as far from the Earth as the Sun is (2 AU), so the true size was around 1 million km. That’s two-thirds the diameter of the Sun.

Here’s an animation from the Comet Holmes Wikipedia entry, showing the location of the comet and the size of the coma on different dates.

In November 2007 the coma became even larger and was in fact bigger than the Sun. However because of this, the coma has become so diffuse that it was hardly visible to the naked eye at all. Although much of the internet was talking about Comet Holmes being bigger than the Sun, most general news and media didn’t care because they couldn’t see it well enough to show the public a good picture.

The final part of Marycie’s question was asking where in the solar system the comet was located. Well I mentioned earlier that it was 2AU away from us. For the time it was visible, Comet Holmes sat just beyond the orbit of Mars. You see its location in this video I’ve made using the excellent Starry Night software.

This video covers the period October 2007 to April 2008. You’ll note that the Earth moves half an orbit during the video. Apologies for the low quality of YouTube.

There is an excellent composite photo of Comet Holmes over the course of the 2007-2008 outburst on the Wikipedia page covering the topic. This image is shown below.

I can hardly type this without thinking of the Muppets’ ‘Pigs in Space’. Whilst writing about space debris recently, and preparing to do a talk on the subject of stuff that we’ve put into space, I got to once again thinking about those frogs that NASA put into space in 1970 (for which this very blog is named).

How many other animals have been put into space and why? Looking into the subject, it’s quite entertaining. so here’s my top ten list of animals sent into space:

10. Flies

In 1942 the first animals were put into space. they were ironically flies. Fruit flies and corn seeds took a one way trip on a US V2 rocket, (you know the ones they built using Nazi technology and slaves).

9. Dogs

On November 3rd, 1957 the first animal in orbit was Laika, the Russian space dog. She flew aboard Sputnik 2 and died during the flight. The Soviets flew 10 more dogs on that programme until April 12, 1961 when Yuri Gagarin became the first man in orbit.

Belka and Strelka (seriously, who named these dogs?) were the first mammals to be successfully returned to the Earth after orbital flight in 1960. you can them in the picture. The other canine record holders are Veterok and Ugolyok, two dogs that spent 22 days in space before returning unharmed in 1966.

Strelka’s puppy, Pushinka was given as a present to the Kennedys and many of her descendants are known still today.

8. Fish

Several fish have visited space. specifically the species Mummichog, Japanese Killfish and Zebra Danio. The Killfish were in fact the only survivors of the Columbia distaster.

More than anything I was simply pleased to find out there is an animal called a Mummichog.

7. Spiders

Experimenting with low gravity environments is obviously a big reason behind putting animals in space. So can a spider build a web in orbit? The answer is yes. Anita and Arabella were two garden spiders that flew on SkyLab in 1973.

The webs were seen to be finer that on Earth and to have variations in thickness throughout each web, unlike the highly uniform webs spun on Earth. Anit’s remains are still kept in a jar at the Smithsonian for all to see. You can see her web above.

6. Cats

Two cats have graced the skies, both put there by the French. The first was Felix in 1963, who survived his trip despite having electrodes implanted into his brain. The second cat’s name does not seem to be obvious, but he did not survive. I can has spacesuit?

5. Newts

In 1985, the Russians sent 10 newts into space after amputating their forearms. They were trying to study the regeneration of cells in low-gravity.

4. Mice and Rats

Many mice have been into space. The US reportedly put loads of them up there in the 1950s, but only the first one survived. In the 1960s, China, the USA and Russia all put many mice into space and into orbit. Nothing much seems to have come of this so far as popular culture is concerned. Douglas Adams, may have had other things to say about that though.

Russia flew rats and mice, as well as hordes of other animals, during its Bion programs in the 60s and 70s. Bion spacecraft (shown above) were designed to test organisms in space. As you can see they look very comfortable. If only NASA had made them, they would have at least had cupholders.

3. Frogs

My favourite space dwellers are the Orbiting Frogs that were sent up in 1970. Why? Well of course it was to sudy motion sickness in space. Don’t you know that frogs get carsick?

The Orbiting Frog Otolith housed the bullfrogs for a week as they circled the Earth. Scientists measured their vital signs and once the experiment was over the simply left the frogs to work it out for themselves. Needless to say it pleases and disturbs me greatly that there are possibly still two frogs up there somewhere.

Also, Toyohiro Akiyama, a Japanese journalist, carried a tree frog with him on a visit to Mir in 1990.

2. Tortoises

The tortoise is held in my esteem on this blog entry because it is the unlikely holder of not one, but two space records! In 1968 a Russian Tortoise became the first animal to go into deep space when it orbited the Moon and returned safely to the Earth.

There must be something about Tortoises that Russian space scientists like (or dislike) because a Tortoise also hold the record for longest flight time in orbit. In 1976 two tortoise and a fish spent 90.5 days in orbit on Salyut 5. They were never recovered and the craft burned up during re-entry in 1977.

1. Monkeys

Of course I had to end with monkeys. On June 11th, 1948 a monkey named Albert was the first to be put into space by NASA the Americans. He was under anesthetic during the launch and never returned. Many other monkeys have famously been put into space.

In 1959, Able and Baker, a rhesus and squirrel monkey respectively, were the first to survive spaceflight. It sounds like the premise of a Warner Brothers’ cartoon. They were placed in the nosecone of a missile and shot nearly 400 hundred miles above the surface of the Earth and over a distance of 1,700 miles. They travelled at 100,000 mph for 16 minutes. Needless to say they experience G-forces above and beyond anything normal (Wikipedia says 16g).

Able died a few days later from complications related to one of his implanted electrodes, but Baker lived until 1984 in the NASA Spaceflight centre in Huntsville, Alabama, possibly running the place.

In 1961, Ham the Chimp was launched into orbit. He was been trained to operate his craft (seriously, Warner Bros again?). He survived and lived a life of luxury afterwards. He appeared many times on television and even starred in a film with Evel Knievel!

17 more monkeys and chimps were flown in the years that followed, by the US, Russia and France, including two that went up on one of the first space shuttle missions.

I would like to end on the tragic is the story of Gordo. A young squirrel monkey from South America, Gordo also flew in the nosecone of a missile. In fact he paved the way for Able and Baker to do so more successfully a year later. He rocketed upward and survived the 10g launch, to the delight of NASA supervisors. However, during the 100,000 mph re-entry, whilst experiencing a whopping 40g, Gordo’s parachute failed to deploy. The squirrel monkey, sealed in the nosecone, sonicly-boomed into the ocean, more than a 1000 miles from Florida. He has never been recovered.