Why we’ll never meet aliens


First page from the manuscript explaining the ...
First page from the manuscript explaining the general theory of relativity (Photo credit: Wikipedia)

Well, the answer is pretty plain: Einstein‘s theory of general relativity – which even in the last month has added to it’s already impressive list of predictive successes – tells us that to travel at the speed of light a massive body  would require an infinite amount of propulsive energy. In other words, things are too far away and travel too slow for us to ever hope to meet aliens.

But what if – and it’s a very big if – we could communicate with them, instantaneously? GR tells us massive bodies cannot travel fast, or rather along a null time line – which is what really matters if you want to be alive when you arrive at your destination – but information has no mass as such.

Intriguingly, an article in the current edition of the New Scientist looks at ways in which quantum entanglement could be used to pass information – instantaneously – across any distance at all. Quantum entanglement is one of the stranger things we can see and measure today – Einstein dismissed it as “spooky interaction at a distance” – and essentially means that we can take two similar paired particles and by measuring the state of one can instantaneously see the other part of the pair fall into a particular state (e.g., if the paired particles are electrons and we measure one’s quantum spin, the other instantly is seen to have the other spin – no matter how far away it is at the time).

Entanglement does not allow us to transmit information though, because of what the cosmologist Antony Valentini calls, in an analogy with thermodynamic “heat death”, the “quantum death” of the universe – in essence, he says that in the instants following the Big Bang physical particles dropped into a state in which – say – all electron spins were completely evenly distributed, meaning that we cannot find electrons with which to send information – just random noise.

But – he also suggests – inflation – the super-rapid expansion of the very early universe may also have left us with a very small proportion of particles that escaped “quantum death” – just as inflation meant that the universe is not completely smooth because it pushed things apart at such a rate that random quantum fluctuations were left as a permanent imprint.

If we could find such particles we could use them to send messages across the universe at infinite speed.

Perhaps we are already surrounded by such “messages”: those who theorise about intelligent life elsewhere in the universe are puzzled that we have not yet detected any signs of it, despite now knowing that planets are extremely common. That might suggest either intelligent life is very rare, or very short-lived or that – by looking at the electromagnetic spectrum – we are simply barking up the wrong tree.

Before we get too excited I have to add a few caveats:

  • While Valentini is a serious and credible scientist and has published papers which show, he says, the predictive power of his theory (NB he’s not the one speculating about alien communication – that’s just me) – such as the observed characteristics of the cosmic microwave background (an “echo” of the big bang) – his views are far from the scientific consensus.
  • To test the theories we would have to either be incredibly lucky or detect the decay products of a particle – the gravitino – we have little evidence for beyond a pleasing theoretical symmetry between what we know about “standard” particle physics and theories of quantum gravity.
  • Even if we did detect and capture such particles they alone would not allow us to escape the confines of general relativity – as they are massive and so while they could allow two parties to theoretically communicate instantly, the parties themselves would still be confined by GR’s spacetime – communicating with aliens would require us and them in someway to use such particles that were already out there, and perhaps have been whizzing about since the big bang itself.

But we can dream!

Update; You may want to read Andy Lutomirski’s comment which, I think it’s fair to say, is a one paragraph statement of the consensus physics. I am not qualified to say he’s wrong and I’m not trying to – merely looking at an interesting theory. And I have tracked down Anthony Valentini’s 2001 paper on this too.

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Review of “The Black Cloud”


Cover of "The Black Cloud"

My interest in astronomy and astrophysics comes from childhood and when I was much, much younger I had an (unscientific) fondness for the “steady state” theory of cosmology, which, in the early 1970s was not as thoroughly discredited as it is today (though, of course, many newer cosmologies borrow from it or show similarities to it – for instance Roger Penrose‘s proposal in Cycles of Time).

Part of the attraction of the steady state cosmology was the figure of Fred Hoyle, or at least how I imagined him: blunt speaking, no nonsense, scientific genius. But until I read The Black Cloud I had not read any of his scientific or literary works.

The book is fascinating as a period piece and not a bad read as a piece of science fiction either – though the overall tone and dialogue reminds me of “Journey into Space” – a 1950s BBC science fiction radio serial recently re-broadcast.

But here is a novel with differential equations, computer program listings (presumably in machine code of some sort as it certainly is not a high level language) and a description of the (then) pioneering technology of pulse code modulation.Not all the science is good though, but Hoyle cannot be blamed for that: although it does not use the term, the view of artificial intelligence here is the conventional one of the time, but also one that fifty years of rapidly advancing computing power has failed, thus far at least, to sustain.

Mixed, with that, though is a fair dose of of Little Englandism, enormous doses of sexism and a quite frightening view into how Hoyle thinks society should be organised – namely with politicians, the people we chose, removed and the dictatorship of the scientists instituted. Stalin ruled in the name of science too.

Hoyle’s preface implies it would be a mistake to ascribe the views of Chris Kingsley, the chief advocate of crushing politics, to himself, but the character sounds far too much like him – the man who once exploded with anger when a snotty PhD student called Stephen Hawking pointed out a flaw in his calculations because he thought it would weaken his attempted blackmail of politicians – for the denial to be credible.

It’s a great book and an easy read, so I do recommend it.

It’s official: we’re getting bigger all the time says Nobel Committee


Prevailing model of the origin and expansion o...
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The decision to award this year’s Nobel Prize for Physics to three astrophysicists who, through measuring the brightness of distant supernovae showed that the expansion of the universe is accelerating, is simply the highest possible confirmation of what most if not all in the field have accepted for a decade or more.

That idea is a decisive break from the cosmology I was taught in 1987 – then the argument was whether the geometry of space time was circular (ie., the big bang would be followed by a big crunch as like a ball thrown in the air,eventually  everything fell back to the starting point), parabolic – ie., the expansion and mass were in exact balance and that at an infinite time in the future the expansion would halt – or hyperbolic, with the expansion too fast for gravity to eventually halt or reverse it.

What has been honoured today does not directly affect these three choices – presumably the expansion could accelerate and then slow and then reverse – but the theory seems pretty clear – the acceleration and the “dark energy” (code for “we don’t know”) that is causing it means the space-time will not stop expanding.

So, does this mean our universe is a “one shot deal” – began with the Big Bang and extending for ever? Not necessarily. Designing experiments to deduce what might have existed before the Big Bang is obviously very difficult (how can you find out what happened before time began?) but there are physical (as opposed to meta-physical) theories and arguments about observational evidence.

Roger Penrose‘s Cycles of Time has one theory (though I’ve not got that far yet) and I have seen Neil Turok on TV outline another (an aside: I don’t now Professor Turok, but I used to know his parents who were leading anti-apartheid activists and members of my local branch of the Labour Party – small world, very big universe).

The second law of thermodynamics and the history of the universe


Oxford Physicist Roger Penrose to Speak at Bro...
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I had to go on quite a long plane journey yesterday and I bought a book to read – Roger Penrose‘s work on cosmology: Cycles of Time: An Extraordinary New View of the Universe

I bought it on spec – it was on the popular science shelves: somewhere I usually avoid at least for the physical sciences, as I know enough about them to make hand waving more annoying than illuminating, but it seemed to have some maths in it so I thought it might be worthwhile.

I have only managed the first 100 pages of it so far, so have not actually reached his new cosmology, but already feel it was worth every penny.

Sometimes you are aware of a concept for many years but never really understand it, until some book smashes down the door for you. “Cycles of Time” is just such a book when it comes to the second law of thermodynamics. At ‘A’ level and as an undergraduate we were just presented with Boltzmann’s constant and told it was about randomness. If anybody talked about configuration space or phase space in any meaningful sense it passed me by.

Penrose gives both a brilliant exposition of what entropy is all about in both intuitive and mathematical form but also squares the circle by saying that, at heart, there is an imprecision in the law. And his explanation of why the universe moves from low entropy to high entropy is also brilliantly simple but also (to me at least) mathematically sound: as the universe started with such a low entropy in the big bang a random walk process would see it move to higher entropy states (volumes of phase space).

There are some frustrating things about the book – but overall it seems great. I am sure I will be writing more about it here, if only to help clarify my own thoughts.

In the meantime I would seriously recommend it to any undergraduate left wondering what on earth entropy really is. In doing so I am also filled with regret at how I wasted so much time as an undergrad: university really is wasted on the young!

(On breakthrough books: A few years ago I had this experience with Diarmaid MacCulluch’s Reformation and protestantism. People may think that the conflict in the North of Ireland is about religion – but in reality neither ‘side’ really knows much about the religious views of ‘themuns’. That book ought to be compulsory reading in all Ireland’s schools – North and South. Though perhaps the Catholic hierarchy would have some issues with that!)