A Blog for the Curious and the Scientifically Perplexed

This is the story of a great journey that started with a great thought. One day in 1895 a boy looked into a mirror and wondered what the universe would look like if he could travel on a beam of light. That sixteen year old boy was Albert Einstein and that one thought started him on the road to discover his Theory of Relativity. The great man has been reinvented as Albert 2.0 to come back and blog about a journey through space on a beam of light and explain the science behind everything from atoms, blackholes to global warming. If you've just joined and want to start at the beginning use the index on the left. If you're bored try these links below just for fun.


Saturday, April 28, 2007

How Stars Shine

Let’s imagine what was going on back on Earth as we are leaving Deneb. For the first few thousand years of our journey the human race had little inkling that stars and the sun were even related. As to how the sun managed to shine so brightly they were equally misguided. As is often the case, this didn't seem to stop some people having strong views about what it wasn't. In 500 B.C. a Greek gentleman called Anaxagoras of Clazomenae almost got sentenced to death for the heresy of saying that he thought the sun was a very large, very hot lump of rock. He escaped punishment with the help of a powerful friend Pericles, but was forced to leave Athens in disgrace. Anaxagoras also calculated that the sun was 35 miles across and about the same distance from Greece as New York would be when someone finally got around to stealing it from the American Indians. His maths was fine but he thought the Earth was flat, which was why his calculations were a bit off.

"A bit tough almost being stoned to death just for getting the answer wrong, isn’t it?"

It wasn't being wrong that was the problem. It would have been just as bad for him if he'd got the right answer.

"How come?"

By suggesting his own ideas he was saying that everyone else was wrong. The real problem was that back in 400 BC the Sun was thought of as a God. So it's no wonder the rulers of ancient Athens didn't like the hot rock idea.

"So when did they work out what stars really were?"

Well they didn't really make any more progress in next two thousand years either. In the middle of 1800's a German gentleman called Julius Robert von Mayer tried to work out how long the Sun had been shining for. He worked out that without some source of energy it could only shine for around 5,000 years. This was based on getting a rock as hot as a rock can get and seeing how long it would take to cool to its temperature today. This time scale would at least have pleased an Irishman, a Mr James Ussher who ended up becoming Archbishop of Armagh, Primate of All Ireland, and Vice-Chancellor of Trinity College in Dublin. Despite all these jobs he spent a lot of time working out how long all the events and stories in the Bible would have taken and worked out the family tree of all the people in the Bible, back to Adam and Eve. He calculated from this that the world began on October 23rd 4004 B.C. He also worked out that Adam and Eve were driven from Paradise on Monday 10 November 4004 BC so it was a short two week holiday in the Garden of Eden.

For scientists back in the 1800's, a 5,000 year old sun was a rather alarming concept because it didn't give them enough time for their theories on geology and evolution to work. The new sciences of geology and evolution assumed that the shaping of the Earth and the creatures that walked on it was a very slow process. Charles Darwin, the man who invented the theory of evolution, was saying that life must have been for around for much longer for humans to have evolved from fish and tadpoles. In Darwin's first edition of On the Origin of the Species by Natural Selection, published in 1859, he made a calculation that the Earth and therefore the sun must be at least 300 million years old. It was either abandon the hot stone theory, or invent a whole new theory to explain where dinosaur fossils came from. In 1857, just before Darwin published his famous Origin of Species, Philip Gosse had another suggestion for dinosaurs. In his book Omphalos, Gosse claimed that God had planted fossils and other evidence of a non-existent past during the six days of Creation to test our faith. After all if the world was created yesterday complete with your memories, photo albums and tree rings how could you tell?

“You couldn’t I suppose.”

Exactly, but believing something that is unprovable isn’t science it’s faith. As scientists were becoming quite attached to Darwin's theory, they kept looking for ways to explain how the sun could have been burning for millions rather than thousands of years.

"So why aren't stars just like big burning fires?"

Well stars are hot and yellow like fire so thinking that the sun is a large burning lump would make sense. But...if the sun were burning like a coal fire it would last barely a thousand years before ending up as cooling embers. Never mind the fact that fires need air to burn and there is no air in space. A thousand years isn't long enough for history books let alone evolution. There was another theory at this time that was a bit more promising. This new idea was that the gravitational contraction of the sun would generate a lot of heat. This new idea came from Hermann von Helmholtz in 1854 and developed by Sir William Thomson. He became Lord Kelvin after this and I’ve a few entertaining stories about him I’ll tell you one day. Anyway Sir William Thomson as he then was calculated this was enough to give the Earth about 30 million years of free lighting.

"But how does gravity make things hot?"

By squeezing things closer together. When you put your finger over the end of a bicycle pump and pump away. The pump gets hot because when air or anything else for that matter is squeezed together or compressed it gets hotter. So the gravity of the sun squeezing together the inner layers would heat up the sun from the inside. This was a nice idea but it still wasn't a long enough time. Evolution needed hundreds of millions of years not just 30 million years, after all the dinosaurs died out 60 million years ago. But this didn't worry Sir William Thomson at all as he didn't believe in Darwin's theory of evolution anyway.


  1. Anonymous said...
    how did th sun ignite if the tree main elements of the fire triangle are heat, air, and fuel, and there is no air in space???
    albert2.0 said...
    The sun's isn't on fire so doesn't need air. It ignited when the gravity made the temperatures in the centre of the sun high enough to start the fusion process.
    Anonymous said...
    Manhattan Island has always been the same distance from Athens. No need to inject anti-American sentiment.

    Nice blog. But don't let your politics get in the way of your message. Albert wouldn't approve.
    Anonymous said...
    Anonymous: Actually, Athens and Manhattan used to be an ocean closer together. A time frame is needed.

    There's no sentiment in the word "stealing"; no adjectives were used. And no Americans stole New York from American Indians, so the non-sentiment would not be anti-American. Perhaps anti-British, but that's a big stretch.

    Well-written history.
    Anonymous said...
    FYI: Charles Darwin was not the inventor of the theory of evolution. Jean-Baptiste Lamarck published his theory of evolution the same year Darwin was born.
    albert2.0 said...
    Lamarck had a theory of evolution but a now thoroughly discredited one based on acquired characteristics.
    Darwin's theory is the first theory of evolution that has supportive evidence. Hence his fame.
    Anonymous said...
    Albert 2.0,

    you should go back and edit these posts. The posts toward the end are really good. These older posts are in need of editing.
    Anonymous said...
    The curse of the hanging apostrophe! The plural is stars, not star's.
    jonniex said...
    Fuel for thought,There is no such thing as a fire triangle anymore.It is a tetrahedron.It has the same things as the fire triangle but adding chain reaction.which lets fire burn if any of the others are missing.
    Anonymous said...
    When the wise men were looking for the new born baby Jesus, they were "guide by a star above their heads"; so we are told. How come they were not singed to nothing; now that we know what stars are!!!!??? This is because the fiction writer or novelist; call them what you will, thought that stars were like little glow worms in the sky.
    You are going to hear a lot more from me and all about all religion; so fasten your seat belts...Dr.EBF.
    Anonymous said...
    If I were Dr. EBF I should keep my comments about "all about all religion" to myself. There are plenty of other websites whereon our new breed of fanatical atheists can spout their propaganda. This a site about science, not the ideological hatred of God and religious believers.

    The laws of physics do not apply to the miraculous. God is not bound by Newton's Laws of Motion, nor the flight of angels by the principles of avionics.
    albert2.0 said...
    Beautifully put. The universe would indeed be a less enchanting place if angels were guided by the principles of avionics.
    Idelis said...
    In your question, What can travel faster than light? my answer would be THOUGHT.

    By the way, I am delighted with your site...it is just fascinating...I am learning about the physical universe versus our spiritual potentials...my perceptions expanding at the glorious speed of the dawn light.

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