How to explain everything

This unique composite view spans the electromagnetic spectrum, from three major space-based observatories. Exploring the Sombrero's high-energy X-ray emission (blue), the Chandra contribution highlights the pervasive, tenuous, hot gas that extends some 60,000 light-years from the galaxy's center. Hubble's optical view (green) shows the more familiar emission from the Sombrero's population of stars, seen from a nearly edge-on perspective and noticeably bulging at the galaxy's bright core. The broad ring of dust that blocks light in other bands, glows in the infrared contribution (red) from the Spitzer Space Telescope. The Sombrero Galaxy is about 28 million light-years away, near the southern edge of the extensive Virgo cluster of galaxies.

It's all about energy. In any good dictionary, energy is defined as `the ability to do work'. Work in this sense doesn't mean just cutting wood or cleaning the floor or even writing this article. It means anything (and everything) that can happen.

In other words, things only happen because there is energy available to make them happen.

The law of conservation of energy

During the eighteenth and nineteenth centuries scientists came to understand that energy cannot be created or destroyed. It can only be changed from one form to another. But, you might ask, if this is the case, why is the world facing an energy crisis?

Well, in most cases, though the energy is not destroyed it is changed from a useful form of energy such as fuel, to a wasted form such as heat, sound or light which tends to spread out and become so weak that, in effect, it becomes useless.

So, without further delay, let me introduce to you the nine types of energy that control everything. You've probably heard of most of them.

Energy transfers

Now let's consider an example. In honor of Sir Isaac Newton I propose that we think about an apple falling from a tree. Clearly something is happening, so energy is involved. Scientists would say an energy transfer is taking place. The question is what type of energy does the apple have before it falls and what type does it have when it hits the ground?

To answer this we need to consider what makes the apple fall. The answer is, of course, gravity. So what type of energy did the apple have before it fell? It must have had gravitational energy.

As the apple fell it got more movement energy. But this movement energy cannot be created from nothing. So where did it come from? The answer is that as the apple fell its gravitational energy was being turned into movement energy.

After hitting the ground the apple stopped. The movement energy was turned into sound and heat which spread out into the ground and the air.

You could pick up the apple, and as you lifted it higher it would get some of the gravitational energy back. (Don't drop it or it'll turn to movement again). If you now eat the apple you can get chemical energy from it. Your muscles, including your heart, can turn this into movement energy.

How are energy types measured?

Energy is measured in joules (J) after James Prescott Joule (1818-1889), an English scientist who carried out much of the most important work in this area. This included a lot of stirring water to see if it got hotter.

Now if energy can't be created or destroyed then there must always be the same amount of it around, just arranged in ever changing ways.

In about 1900, many scientists thought that eventually all the useful energy in the universe would be used up, and that it would all be spread so thinly through space that nothing else could happen. Ever. This idea was known as the Heat Death of the universe.

Later, it was discovered that the universe is expanding, an observation which led to the Big Bang theory. The Big Bang theory states that the universe came into existence at a single point in space about 15 billion years ago. It exploded outwards and has been expanding ever since.

However, gravity is pulling everything back to that point, so the expansion must be slowing down. The law of conservation of energy means that as all the objects in the universe slow down their movement energy is changing into gravitational energy. Some scientists believe that the universe will stop expanding and that this gravitational energy will cause all the objects to fall back towards a single point again. They call this the Big Crunch.

And what would happen next? Well, if all the energy and all the `stuff' in the universe were squashed into a single point, wasn't that what caused the Big bang in the first place?

Don't panic, even if this theory is correct it won't happen for a very, very, very, very long time. The nine types of energy are: heat, light, sound, chemical, electrical movement, gravitational, nuclear and elastic; whereas, the everyday energy transfers are: electrical, sound, chemical, heat, light, gravitational, and movement.

A question for the reader: How did the chemical energy get into the apple? The answer to this and more next time.

Corrin Funnell is a laser physicist with a specialty in laser spectroscopy. He has taught in the UK, Egypt, and at Thailand's own Harrow International School, where he became head of the physics department. Currently, he is head of Physics at Island School, Hong Kong.

Exploding star brightens Nasa's day

A Nasa artist illustrates what the brightest supernova ever recorded, known as SN2006gy, might have looked like when it exploded last week. The star "is a special kind of supernova that has never been seen before," said Nathan Smith, of the University of California at Berkeley, leader of the discovery team. — AP

A massive exploding star _ the brightest supernova astronomers have ever seen _ has scientists wondering if a similar celestial fireworks show may light up the sky much closer to Earth sometime soon.

The discovery, announced today by Nasa, drew excitment for months from the handful of astronomers who peered through telescopes to see the fuzzy remnants of the spectacular explosion after it was first spotted last year.

Using a variety of Earth and space telescopes, astronomers found a giant exploding star that they figure has shined about five times brighter than any of the hundreds of supernovae ever seen before, said discovery team leader Nathan Smith of the University of California at Berkeley.

The discovery was first made last September by a graduate student in Texas.

``This one is way above anything else,'' Smith told ifThe Associated Pressnf. ``It's really

astonishing.''

Smith said the star, SN2006gy, ``is a special kind of supernova that has never been seen before.'' Observations from the Chandra X-ray telescope helped show that it didn't become a black hole like other supernovae and skipped a stage of star death.

Unlike other exploding stars, which peak at brightness for a couple of weeks at most, this supernova, peaked for 70 days, according to Nasa. And it has been shining at levels brighter than other supernovae for several months, Smith said.

And even at 240 million light years away, this star in a distant galaxy does suggest that a similar and relatively nearby star _ one 44 trillion miles (70.8 trillion kilometres) away _ might blow in similar fashion any day now or 50,000 years from now, Smith said.

It would not threaten Earth, but it would be visible to people in the Southern Hemisphere, he said. — AP