Thursday, 27 April 2006
But now imagine that this planet has a surface temperature hot enough to melt lead, an atmosphere that would crush you, and where it rained sulphuric acid everyday.
This place is Venus. Venus is named after the Roman goddess of love, but this week on Mr Science, we will discuss a planet that has nothing to do with love and is about as close to Hell as you can possibly get.
Back when the solar system was being formed, Earth and Venus looked quite similar – they were both rocky, inhospitable places with volcanic eruptions spewing carbon dioxide into the air. Both had water vapour in their atmospheres. On Earth, this water vapour turned into clouds and eventually the oceans. On Venus, which is 30 per cent closer to the Sun, it was slightly too hot for liquid water to form and eventually the sun's radiation broke apart the water molecules.
On Earth, the oceans dissolved much of the atmosphere’s carbon dioxide and helped create limestone and other minerals. On Venus, all this carbon dioxide, with no water to dissolve in, continued to accumulate in the atmosphere, until the pressure was 90 times that of Earth’s. This caused a runaway greenhouse effect. With radiation from the Sun not able to escape from this dense atmosphere, the temperature got hotter and hotter until the average temperature reached 450 degrees Celsius. It was liquid water, or the lack of it, that made all the difference.
So could we possibly ever go to this place? The first landing on Venus was in 1966 when a Soviet probe called Venera 3 crash-landed on the surface. In 1967, Venera 4 descended through the atmosphere sending back readings, but its batteries failed before it touched down. Venera 5 and 6 were crushed by intense atmospheric pressures. Finally, in 1975, a descent vehicle from Venera 9 made it to the ground. No human has ever been there.
On April 11 2006, the Venus Express, which is a European Space Agency mission, successfully assumed orbit around Venus, and it plans to map the Venusian surface for about two Venusian days. This may not sound like a long time, but this actual equates to about 500 Earth days. This means that Venus rotates very slowly. Another usual facet of Venus’s rotation is that rotates in the opposite direction to the other major planets – that is, the sun rises in the West and sets in the East. Scientists do not know why Venus rotates so slowly and in the opposite direction, but it is thought that is has something to do with solar heating of the thick atmosphere, friction and tidal forces.
So to survive on Venus’s surface, you would need to be able to withstand incredibly hot temperatures, intense atmospheric pressure and acid rain from the sulphuric acid clouds. It would seem therefore unlikely that life as we know it could live on Venus’s surface.
But some scientists, like NASA’s Geoffrey Landis, think that life may exist up above the clouds. At 50 km above the surface, the temperature range is between 0 and 50 degrees Celsius, the air pressure drops to 1 atmosphere and the gravity is 90 percent that of Earth’s – very pleasant conditions for life, or at least, microscopic life. Indeed, scientists have discovered that the chemical carbonyl sulphide is found in Venus’s atmosphere. This is a compound that is difficult to make using natural processes and is usually found as a bi-product of life.
But it would seem that Venus has nothing to with its namesake, the goddess of love. However, stay tuned for next week’s Mr Science, when we take a closer look at this topic of love, and see whether there is any science behind human attraction.
Listen to this show here
Tuesday, 18 April 2006
Before this time, the solar system was just a massive cloud of gas – mostly Hydrogen and Helium, but with some elements that we see around us every day - like metals - and some necessary for human life - like oxygen.
This cloud started to condense, perhaps because the explosion of a nearby star in a supernova caused a shockwave that started the collapse. As gravity pulled all the molecules in the cloud closer and closer together, collisions between the molecules became more frequent, and so the cloud became hotter and hotter. In the centre of the cloud, it was so hot that the sun began to form.
Further out from the centre, the gases started to cool down, and dust and ice started to freeze out into solids. These solids occasionally ran into each other, and stuck together. As the objects got bigger and bigger, more debris was able to stick to them. Eventually these objects got big enough that they started attracting each other through gravity – these rocky objects are called planetesimals.
One of these planetesimals, about 150 million kilometres from the sun, became the Earth. Another of these smashed into the Earth, tilting it on its side and perhaps creating the Earth’s tectonic plates. This one became the Moon.
The infant Earth was very different from the Earth of today. There were no oceans, and most of the atmosphere was blown off by the solar wind from the infant sun. It was smashed by debris still around from the formation of the solar system, and was so hot that it was fully molten.
Heavy elements sank to the centre of this super hot liquid ball, while light elements rose to the surface. On Earth Day 4.4 billion BC, the Earth’s surface finally cooled enough to form a solid crust, and as this cooling continued, the separation of heavy and light elements caused the Earth’s layers that we see today.
Around Earth Day 4 billion BC, the Earth was in a period of heavy asteroidal bombardment. This caused steam to be released from the crust, and intense volcanic activity released more and more gases, giving rise to an atmosphere. Asteroids also brought water to the Earth in the form of ice, which was quickly evaporated into water vapour. Now clouds could form. The Earth continued to cool, and eventually it rained. It rained so hard and so often that the oceans were formed on about Earth Day 3.8 billion BC.
The Earth’s atmosphere at this stage probably contained mainly ammonia, methane, water vapour, carbon dioxide, and nitrogen. There was very little oxygen, but this is when it is thought that life started to begin. Some scientists think that the energy from volcanoes, lightning and ultraviolet radiation – as there was yet no ozone layer – drove chemical reactions that produced complex molecules from simple abundant compounds such as methane and ammonia. All this continued for a very long time, until by chance there arose a new molecule, a molecule that had the ability to replicate itself. Eventually, and scientists are not yet sure how, DNA was formed. DNA is the replicator that is the basis of all known life, except for a couple of viruses.
Lets skip about one billion years ahead to Earth Day 3 billion BC. At this time, photosynthesis in some primitive life started to occur. We see photosynthesis around us all the time – it is what plants do to convert the sun’s energy into energy it can use to grow. This primitive photosynthesis converted the carbon dioxide in the atmosphere into oxygen. At first, this new oxygen was bound up by minerals on the Earth’s surface. But eventually the minerals could not take up any more, and oxygen started to accumulate in the atmosphere. Some of this oxygen formed ozone that blocked the sun’s ultraviolet rays, which although probably helped to start life, was making life difficult on the surface as it made cells mutate too quickly.
Lets skip a couple of billion years ahead. We’ve now got an atmosphere with plenty of oxygen in it. We’ve got harmful UV light being blocked. At Earth Day 700 million BC, plants are colonising the water’s edge of the supercontinent Gondwana, which was made up of the Earth’s modern southern hemisphere countries. On Earth Day 450 million BC, animals crawled out of the oceans onto the land and ate the plant life, which by this stage had made a happy home on the land. These animals got bigger and bigger, and on Earth Day 230 million BC, dinosaurs appeared. They dominated the Earth for some 150 millions years until they were finally wiped out in a catastrophic extinction, possibly caused by an asteroid impact.
It is thought that on Earth Day 6 million BC – or if the history of the Earth was condensed into a single day, then at 2 minutes to midnight – apes started to walk upright. Soon after, the first human-like species evolved, and on Earth Day 200,000 BC, or 2 seconds to midnight, Homo Sapiens arrived. 10 thousand years ago there were 5 million humans on Earth, now there are 6.5 billion. We are still learning about past human civilisations, and still uncovering artifacts from ancient Rome and China.
The Earth has survived four major ice ages – the first of which iced over the Earth completely. There have been five major extinction events and many smaller ones – the biggest one, the Permian-Triassic extinction event, or the “Great Dying” of Earth Day 251 million BC, wiped out 90% of all marine species and 70% of all land vertebrates. One can only imagine what’s in store for the Earth in the future...
Tuesday, 11 April 2006
What if that island was a lost island of pony-sized elephants, gigantic lizards and even miniature humans? Sound far-fetched? Whilst the idea may be fanciful, scientists think they may have discovered such a place.
The island is called Flores, and is east of Java in Indonesia. A team of Australian and Indonesian paleoanthropologists and archaeologists were looking on Flores for evidence that the Homo sapiens species of humans – the species that we all are – migrated down through Asia and into Australia about 50 000 years ago.
What they found was truly astounding.
They found the remains of at least seven individuals of some type of human, but a type that looks nothing like us. These humans were only about one meter tall, weighed only 25 kg and had brains that were four times smaller than our own.
Scientists now call them Homo floresiensis, on account of where they were discovered, although they are more commonly, and perhaps cruelly, known as Hobbits, after the little human-like species from The Lord of the Rings.
What was even more surprising was that their remains suggested that they may have survived as recently as 12 000 years ago – which means that some of the stories passed down by the local people in the area about seeing little people could possibly be true! Even an editor of the reputable science magazine Nature has suggested that it is not beyond the realms of possibility that one day we may find a human-like species like this still alive and well somewhere in an uncharted part of the world. It is even more likely that, as Homo sapiens and the hobbits were living in the same part of the world at the same time back then, they probably came face to face.
There is currently debate about how to classify these hobbits. It is not sure yet whether they descended from Homo erectus – the same species from which we Homo sapiens descended – or whether they could even be an off-shoot of modern humans – they did have quite sophisticated tools, and although their brains are small, they are big for their size.
It is thought that Homo erectus, a tall not-quite ape, not quite homo-sapiens creature, travelled out of Africa, colonised Asia and then stopped. There’s never been evidence that they travelled over water – simply because they weren’t smart enough. Is this evidence that they did? Or is this evidence that these hobbits are more like us than we think?
What seems clear though is that the reason this species is so small is because of the conditions in which it lived on the island. When they came to the island, and its unsure how that happened at the moment, they would have found a small island with limited resources. As generations passed, they evolved to get smaller and smaller, as in this way they would require less food to survive. Also, having a smaller body in the hot and humid conditions meant that was easier to cool down and less heat was made within the body when they moved around.
Some scientists think that this is an example of island dwarfing, which is a biological phenomenon by which the size of an animal isolated on an island shrinks dramatically over generations. It is a form of natural selection in which a smaller size provides a survival advantage.
But these hobbits were not the only species on the island that were a little strangely shaped. Dwarf elephants were also found on the island and were probably hunted by groups of their hominid counterparts. These animals, called Stegodons, were smaller than modern water buffaloes and also suffered island dwarfing.
Not every species on Flores is small though. In contrast, Flores is still home to a giant rat, which has a head and body size of about 45 cm, and a tail length of up to 70 cm, which means that they can stretch over 1 m! The island is also home to the Komodo dragon, a giant carnivorous lizard that can be as long as 3 m and weigh around 70 kg. If its initial bite doesn’t kill its prey, the over 50 different strains of bacteria in its teeth will. This prey includes pigs and even water buffalo. It might have been able to stay huge on the island, unlike the elephants, because these elephants, and perhaps even our hobbit friends, were the perfect meal size for them.
But whilst the giant rats and dragons survive to this day, the mini humans and elephants do not. Scientists think that they fell victim to a volcano eruption about 12 000 years ago. But could these strange and wonderful species exist somewhere else in the world? Be careful next time you’re shipwrecked and wash up ashore on a deserted island. A race of three-foot high humans who hunt elephants that only come up to your waist, and eat rats as big as dogs may await you. And be careful of the dragons with deadly bacteria-laced saliva. Who ever said science was dull?!
Listen to this show here
Wednesday, 5 April 2006
Time travel and wormholes used to belong to the minds of science fiction writers. But, with a little inspiration, scientists have begun to show us that science fact can be just as strange as science fiction.
Einstein's special theory of relativity shows that time travel into the future is actually possible – there is no reason why we can’t do it. We just don’t know how to yet. Einstein’s theory suggests that the way we feel time going by is related to how fast we are moving. Objects travelling at speeds close to the speed of light (about 300 000 kilometres per second) age slower than objects which are not moving.
In 1975, Professor Carrol Alley tested Einstein's theory using two synchronised atomic clocks. Carrol loaded one clock onto a plane, which was flown for several hours, while the other clock remained on the ground. At the end of its flight, the clock on the plane was slightly behind the one that was left on the ground – that is, time had actually passed more slowly for the clock on the plane than the one on the ground. It had travelled every so slightly forward in time. So to travel into the distant future, somehow scientists need to come up with technology than can allow us to travel somewhere near the speed of light.
But what about time travel into the past? In theory, nothing in the laws of physics is stopping us from doing it, however, no one quite knows how to do it.
According to Einstein's theories, any object with mass will cause a warp in space-time, similar to a bowling ball sitting on a mattress. Because space and time has been stretched, clocks operate slower close to Earth than in the vast areas of space. Previous theoretical designs of time machines have used this concept of mass distorting space-time, however these theoretical machines require a tremendous amount of energy to work.
A professor of theoretical physics named Ronald Mallett came up with another idea. He believes that anything containing energy could warp space-time, and as a result, he has designed a time machine that uses light, rather than mass. His theoretical time machine consists of a ring of two intense beams of light, circling in opposite directions. By slowing the light down in an ultra-cold bath of atoms and increasing the intensity of the beams, he thinks space-time inside the ring would become warped. Eventually, space and time would become so distorted by the circling light that time would become a dimension similar to space - a dimension that you could move along! If you entered the ring and walked in the correct direction, you could walk backwards through time - maybe even passing yourself as you entered the ring!
However, there are lots of problems putting Ronald's theory into practice. The temperature of the ring would have to be close to absolute zero (-273°C), so humans would find it difficult to use. And it would also be impossible to travel back to a time before the machine was switched on. Perhaps this is why we’ve never met anyone from the future!
So, what about these wormholes? Can we travel across the universe instantly using one?
The universe appears as three dimensions in space (up-down, left-right, and forward-backward) and a fourth dimension known as time. Wormholes are connections between two different places in space and time. This is difficult to visualise in four dimensions, but it is easy to see in two. Imagine two points on an sheet of paper. You could travel between the points by following a line on the piece of paper, or you could fold the paper over so that the two points touch. By folding the paper, you are making a 'wormhole' in the two-dimensional paper world.
Although there is no experimental evidence for the existence of wormholes, theorists believe that they may exist. Wormholes first appeared possible in Einstein's theory of gravity, in 1913. However, physicists had almost forgotten about them until the eighties, when Carl Sagan included them in his novel Contact, in which the main character travels to another part of the universe to visit another civilisation.
To be stable, wormholes need lots of what’s called negative energy. Quantum mechanics suggests that it exists, but we haven’t found it yet, and we don't know whether the laws of quantum mechanics allow enough negative energy to be concentrated in such a way as to allow wormholes to exist.
One possible location for wormholes is at the centre of black holes. Travelling through one of these might prove extremely difficult however, since the wormhole would be so unstable that it would collapse as soon as a spaceship (or even a ray of light) entered it. This is because there would not be enough negative energy to hold it open.
So don't pack your bags for a trip to the other side of the galaxy just yet, or for a trip back in time. Scientists haven’t found any wormholes yet, or made a time machine. So we do know that a wormhole is not going to get you across Beijing in time for work after you’ve slept in.
Listen to this show here
Tuesday, 4 April 2006
Listen to this mp3 here
Listen to this mp3 here
Editor: Note that Pluto was demoted from its planet status in 2006 after this show
Monday, 3 April 2006
This version is heavily edited so as to not get in trouble with the Chinese radio people, and because at 5am without any sleep and slightly drunk we were hardly in the mood for radio pleasantries.
The mp3 is here.
This was the debut of the West brothers on China Radio.