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The Big Bang and Cosmology

Should we believe it?

I really don’t know.  Change is afoot (and not before time, we old folk might say).  Much of the cosmologists’ current edifice may yet come tumbling down.

 

Thinkers down the ages have all claimed to understand the cosmos.  They’ve never been right yet, and I see no reason why they should suddenly be right now.

 

We old folk have an advantage here because we’ve seen it all before.  The story has changed beyond recognition in our lifetime, so we are already conditioned to imagine that it is likely to go on developing just as fast.

 

The cosmologists may be getting closer to the truth of the matter, but I don’t believe that they will ever get to the bottom of it.  That cosmologist who, many years ago now, said something like “the most un-understandable thing about the Universe is that we understand it” was being both arrogant and stupid.   (I have to admit though to having been just as arrogant and stupid in my time – though fortunately not in public.)

 

When I was a kid, the textbooks were still telling us that the Universe was eternal and unchanging – mainly the eminent astronomer Sir James Jeans if I remember rightly.  Nobody seemed to worry about the huge amounts of energy were being used up, just keeping the stars going.  And that’s only the first of the impossibilities of it.

 

The Universe was believed to follow Newton’s laws perfectly and there seemed to be nothing more to learn – except for one tiny detail.  Mercury’s orbit didn’t quite fit.  (The planets’ orbits are not perfect circles, they are very slightly elliptical.  And Mercury’s ellipse ‘precesses’.)

 

Then along came Einstein, and others equally remarkable though less famous.  Together they blew this simple story out of the water.  The Universe was far more complicated than astronomers had ever dreamed of.  Oh, and Einstein’s theory of Relativity also explained the Mercury problem.

 

Then there was the ‘debate’ between Big Bang and Fred Hoyle’s Steady-State theory.  Indeed, it was Hoyle who originally invented the name ‘Hot Big Bang’ as a term of abuse. 

 

The history of Science is full of episodes like this.  Before Newton, the astronomers of the time thought they understood things.  

 

At the end of the 19th century, physicists thought that they understood their world too.  Young bloods were actually advised not to take up physics, because there was nothing more to learn.   But Einstein and others transformed Physics as much as they transformed astronomy.

 

The recent crop of cosmologists have made a number of assumptions which they often didn’t realise they were making, but which could easily be wrong.  This isn’t me talking here.  Cosmologists themselves remind each other of it from time to time – in top journals. 

 

For a start they took the Laws of Physics – as derived in one miniscule patch of the Universe and over an infinitesimal period – and assumed that they would apply perfectly throughout the whole of space and time.  In a sense, they could do no other.  If that’s all the information you have, then you must do your best with it. 

 

The problem came when they started to believe it.  I’m an engineer, and we are trained never to believe anything that hasn’t been thoroughly checked out – over its entire envelope of interest. 

 

But the cosmologists did the opposite.  Instead of treating Big Bang and their new cosmology with caution, they raised it to the level of dogma.  You wouldn’t think that scientists would do such a thing but they do.  ‘Behavioural’ scientists also took it as an article of faith that animals were no more than machines (more).  The behavioural folk are only now extricating themselves from the mess that this left them in.

 

An article in Science (3 August 07) suggests that astronomers are now beginning to catch up with us engineers.  It contains the comment that “… this inference requires that Newton’s law of gravitational attraction be extrapolated well beyond where it was established”.  .

 

I’ve not read that Big Bang itself is currently under threat, though please don’t waste too much brainpower on the details!  Astronomers can now actually see what was happening only 400 thousand years after it.  This is the mysterious background radiation that we hear about from time to time.  The radiation is in fact a wall of hot fog, and it represents the instant that the young Universe became transparent.  The Universe has expanded a thousand fold since then.  The radiation that this wall of fog emitted has been stretched out until it’s no more than a faint microwave hiss.  Everything that the astronomers observe from then on seems to fit the cosmologists’ theories.  They fit within limits anyway.  Unfortunately the devil is always in the detail, which is why we have to reserve judgement.

 

Until recently, astronomers and cosmologists were arguing fiercely over how long ago the Big Bang was.  It’s difficult to understand why.  The difference between the two camps was never more than about ‘a factor of two’, which you’d think was pretty good going under the circumstances; especially considering that both camps had to rely on these notorious assumptions.  Now however the different groups seem to have homed in pretty well on a single date – 13.7 thousand million years ago I think – though as soon as you think you’ve nailed it, they change it again!

 

We used to be expected to believe that there was nothing before Big Bang, and that time started at that moment.  This was always a pretty implausible tale to many of us.  And fortunately the cosmologists are beginning to question it too.  They are even looking at the background radiation for clues on what might have been happening in the run-up to it.  The evidence might lie in the tiny variations shown in this NASA map.  The Internet provides conflicting numbers on just how small these fluctuations are.  So all I can say at the moment is that they’re tiny.

 

We also used to be told that the Universe would eventually start contracting again, and would end in a Big Crunch – possibly to be followed by another big bang.  But this would mean that the expansion ought to be slowing down, or at least staying the same.  And a few years ago, the astronomers observed that the expansion actually seemed to be accelerating.   However I’ve recently read that this acceleration could be an artefact, resulting from assumptions that …  You can fill in the rest.

 

For a number of years now, the cosmology that follows Big Bang has been in trouble.  Indeed the Science article that we mentioned above goes on to describe the situation as “preposterous”.  There are too many things that don’t quite fit (where have we heard this before?).  A number of add-ons have been affixed.  Off the cuff, I can remember string theory, multiple dimensions, dark matter and dark energy.  But still things don’t quite work.

 

One fairly basic problem is that there’s not enough ‘observable’ matter in a galaxy to stop it flying apart.  I’ve never understood why this is a problem.  I’d have thought that you could posit enough dead stars to provide all the extra mass the cosmologists need.  But apparently not.  This is why they had to invent a mysterious new form of matter, this dark matter, to get them off the hook.   The experimentalists are now busy looking for dark matter.  At the time of writing they’ve not found it yet, but they are still looking.

 

But others are contemplating more drastic measures, like questioning the basic laws of physics.  Not before time, you might think.  One new theory is ‘Modified Newtonian Dynamics’, or MOND.  MOND points out that ‘Newton’s Second Law’ (don’t worry if you’ve not met it) has only been checked out for ‘large’ accelerations.  Maybe things are different for the tiny accelerations that many cosmic bodies experience.  It turns out that you can explain a lot by a fairly simple modification to Newton’s law – one which only kicks in when the acceleration is extremely small.  Then you don’t need dark matter. 

 

MOND seems to be gaining ground fast.  The Science article describes all the mysteries that MOND explains, plus a few that it doesn’t.  I don’t think we should worry too much about the latter.  It’s only a first stab after all.

 

And once the scientists have started questioning their articles of faith, who knows where they will end up!

 

© C B Pease, February 08