Top 4 Bonkers things about the universe
As a science writer, I am constantly amazed at how much stranger science is than science fiction; how much weirder the Universe we find ourselves in is than anything we could possibly have invented. Here are my Top 4 Bonkers Things About the Universe.
Number 4: If the sun were made of bananas, it wouldn't make much difference
This is because the reason the Sun is hot is that it contains a lot of mass. All that mass weighing down on the core squeezes it and makes it very hot. In fact, the centre is about 15 million degrees. Crucially, at such temperatures, all matter – regardless of its composition - dissolves into an anonymous state called a "plasma". So it doesn't much matter what the Sun is made of. Actually, it is about a billion billion billion tonnes of mostly hydrogen gas. But if you were to put a billion billion billion tonnes of microwave ovens in one place - or a billion billion billion tonnes of bananas – then you’d get something equally hot that looked pretty much like the Sun.
Number 3: You could fit the entire human race in the volume of a sugar cube
This is because matter is incredibly, mind-bogglingly empty. An atom is like a miniature Solar System, with a tight nucleus playing the role of a Sun orbited by electrons like planets. But the nucleus is incredibly tiny compared with the orbits of the electrons. Tom Stoppard, the playwright, had the best image. He said, if the nucleus is like the altar of St Paul's cathedral, an electron is like a moth in the cathedral, one moment by the altar, the next by the dome. Imagine squeezing all the space out of an atom. Well, if you did that to all the atoms in all the people in the world, you could indeed fit the entire human race in the volume of a sugar cube.
Number 2: 98% of the universe is invisible
Only four per cent of the mass of the Universe is in the atoms that make up you and me, the stars and planets. And we’ve only ever seen half of that with our telescopes. 23 per cent of the mass of the Universe is invisible, “dark”, matter. We know of its existence only because its gravity tugs on the visible stars and galaxies. No one knows what it is. And 73 per cent of the mass of the Universe is dark energy. Discovered only in 1998, this invisible stuff fills all of space and it has repulsive gravity. To say we are at sea in understanding dark energy is a bit of an understatement.
Our best theory of physics is quantum theory. It has given us lasers and computers and nuclear reactors, an understanding of why the sun shines. But when quantum theory is used to predict the energy of the vacuum – of the dark energy – it gets a number which is one followed by 120 zeroes times bigger than what we observe. This is the biggest discrepancy between a prediction and an observation in the history of science.
Number 1: Out there in the universe there are an infinite number of copies of you reading and infinite number of copies of my Top Four Bonkers Things About the Universe
This takes a bit of explaining. Basically, the Universe was born about 14 billion years ago. That means that we can see only the stars and galaxies whose light has taken less than 14 billion years to get here. Objects whose light would take more than 14 billion years – well, their light hasn’t got here yet. It’s still on its way. The consequence of this is that we can only see a portion of the Universe. We call it the “observable universe”. And the observable universe is surrounded by a horizon. It’s pretty much like the horizon at sea. Just as we know there’s more of the sea over the horizon, we know there’s more of the Universe over its horizon.
How much? Well, according to the standard picture which is called “inflation”, there is an infinite amount. So, imagine the observable universe is like a soap bubble. Well, beyond the edge of it, there are an infinite number of other soap bubbles. All of them would have had a big bang, and in all of them different galaxies and stars would have congealed out of the cooling debris of the big bang fireball. In short, they would all have different histories.
But they key thing – and this has got to do with quantum theory and I won’t go into it – the key thing is that there are only a finite number of possible histories. Now, if we have only a finite number of histories and an infinite number of places for those histories to be played out, then it follows that every possible history happens an infinite number of times.
So there are an infinite number of places where you never started reading this article. There are an infinite number of places where the dinosaurs were not wiped out by an asteroid 65 million years ago but went on to develop intelligence and build motor cars.
If you’re wondering why I’ve picked this as my Number 1 Bonkers Thing About the Universe, it’s simple. Even if this is the worst article you have ever had the misfortune to waste your time on, I can console myself with the thought that, in an infinite number of other places in the Universe, you thought it was the best thing you had ever read and raved about it to all your friends and family!
Marcus Chown covers some of these ideas in his new book We Need to Talk About Kelvin: What Everyday Things Tell Us About the Universe (Faber & Faber).
You can also catch Marcus on his blog tour.
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