Take an Imaginary Journey Into Deep Space
Imagine traveling a few hundred miles up, into the sky, from the Earth’s surface. At this point, you’d be in the slightly more typical environment of space. But, you are still being heated and illuminated by the sun, and half your view is still taken up by the Earth itself. A typical location in space has none of those features.
So, travel a few trillion miles (1 light year = 5.879 x 1012 miles = 1 trillion miles) further in the same direction. You are now so far away that the sun looks like other stars. You are at a much colder, darker and emptier place. But, it is not yet typical – you are still inside the Milky Way galaxy, and most of the places in the universe are not in any galaxy.
Continue traveling until you are clear outside the galaxy – say, a 100,000 light years from Earth. At this distance you could not glimpse the Earth even if you had the most powerful telescope that humans have built. But, the Milky Way still fills much of your sky.
To get to a typical place in the universe, you have to imagine yourself at least a 100,000 times further out, deep into intergalactic space – finally you would have arrived in a typical location.
A Typical Place in the Universe is Dark, Cold, and Empty
The sky would be pitch black. The nearest star would be so far away that if it were to explode into a supernova, and you were looking directly at it when its light reached you, you would not even see a glimmer. That is how big and dark the universe is.
It’s cold. The temperature is 2.7 kelvin, which means 2.7 degrees above the coldest possible temperature, absolute zero, or about 270 degrees Celcius (518 degrees Fahrenheit) colder than the freezing point of water. That’s cold enough to freeze every known substance except helium, which is believed to remain liquid right down to absolute zero, unless highly pressurized.
It’s empty. The density of atoms out there is below 1 per cubic meter. That’s a million times sparser than atoms in the space between stars, and those atoms themselves are sparser than in the best vacuum that human technology has yet achieved.
Almost all the atoms in intergalactic space are hydrogen or helium, so there is no chemistry. No life could have evolved there, nor any intelligence. Nothing changes there. Nothing happens.
That’s the unimaginably desolate environment which is typical of the universe – it’s a measure of how untypical the Earth and its chemical soup are, in a straightforward physical sense.
David Deutsch, FSR (Fellow of the Royal Society) is an Israeli-born British physicist at the University of Oxford. He is a Visiting Professor in the Department of Atomic and Laser Physics at the Centre for Quantum Computation (CQC) in the Clarendon Laboratory of the University of Oxford.
Deutsch pioneered the field of quantum computation by formulating a description for a quantum Turing machine, as well as specifying an algorithm designed to run on a quantum computer. He is a proponent of the many-worlds interpretation of quantum mechanics.
Books David Deutsch has written:
- The Beginning of Infinity: Explanations That Transform the World
- The Fabric of Reality: The Science of Parallel Universes – and Its Implications
David Deutsch Interview – Which Laws of Nature Are Fundamental?