Thursday, 18 October 2012

Starry, Starry Night.

    Blank nights can be wonderful.  Not if you are intent on having a good night's sleep in your comfortable centrally heated 5 star bivvy of course, but to sit out under the stars on a warm still night amongst the woods and wildlife, can be so much more satisfying.  Everyone should have a few good old blanks each year.
    And so, a couple of weeks ago I approached the lake, carrying a minimum of gear, chose my spot, seeing two or three carp swirl even as I prepared my tackle.  All looked good for the fishing to come.  It wasn't to be, and neither rod registered so much as a twitch all night, despite good fish being obviously present and moving well.  As darkness fell, the wildlife started to move.   Skeins of Canada geese had already passed over, heading towards other, nearby, lakes, flying in noisy and untidy V formations.  The first woodmice had stirred, scuttling around my feet.  And only a little later the tawny owls started to hoot in the trees behind me.
    The sky was very clear, unusually so for the UK, and three prominent planets were visible during the night, 3 very bright dots of silver in the sky. I am fairly sure they were Venus, Saturn and Jupiter.  Not a cloud obscured them at any time during the night.   I sat there, with little to do, other than watch the heavens rotate about me.  The Milky  Way was just about visible, and it is now many a year since I last saw it clearly in the UK. The eye naturally wanders (or so I tell my wife), its attention is so easily caught by any shiny little trinket, and aeroplanes suddenly appearing, whether directly in front, or at the limits of peripheral vision, seem to become instantly visible, with the very first distant flash of their navigation lights.  Their lights, be they ever so dim, are instantly spotted.  Many planes flew over and around the area overnight.  I suspect I saw most of them.  Our eyes may have far less acuity than those of the predatory birds, the hawks and eagles, but they are still astonishingly capable. I made one of my many daft mistypes whilst writing this paragraph.   So I will now define the word "Earoplane"  as being any aircraft that you can hear but not see.
    Other things moved, and were seen, in the sky.  Several meteor trails angled down above the horizon, rapid, short streaks of light, dust particles burning up in the atmosphere.  Only 4 or 5 on this occasion, but there have been nights when thousands were to be seen. One or two man made satellites also silently drifted across the sky, far too high and too fast for aircraft. Had I recorded their times and directions, there are web sites that would have identified them for me.  A sort of Observer's Book of Satellites. The silhouette of one or two herons were seen as they flew over. Herons are far more nocturnal than most people suspect.  I often see them flying up and down above rivers, in the middle of the night.  It seems likely, therefore, that they fish at night too?   Usually they see me.   I may be completely stationary, in dark combat gear, at 1 a.m. in the morning, but, when it gets to within 20 yards or so, the bird will suddenly shear off a previously straight flightpath, as it takes a panicked avoidance route.  Can it see in infra red?  There seems initially little point in it having such, fish being cold blooded, and therefore at a temperature very similar to their environment.  But once or twice, there have been pictures in the daily papers, of herons swallowing rats, or even small rabbits.  I saw one heron, perched atop a metal structure that crossed the river.  It was trying to catch bats, stabbing at them as they flew past.   I didn't see it succeed in its aims, and would have been very impressed had it done so. 
    I do a lot of thinking at night.  As a kid, maybe 7 or 8 years old, I would lie in bed, wondering how big was the universe. For kids that age, everything has to have a size, and so I wondered how large it really was.   Surely it could not go on forever?   But if not, how does it end?  Maybe, like so many other things, it ends at a wall?......But what is on the other side of that wall?   Dunno.   Maybe the wall just goes on and on, an extremely thick wall?....but even a wall cannot just go on and on, too many bricks would be needed, if nothing else.    Hence I concluded, aged maybe 8 years old, that the universe was infinite.
   Later, when I heard about the "Big Bang" I was immediately sceptical.   How? Why?   Suddenly, when I asked such questions, the scientists seemed to be going almost religious on me.
"What caused the Big Bang?   What was there before the BB?"   
And the scientists were saying "It makes no sense to ask such questions, time did not exist before the big bang."  Ask a religious person:"Where did God come from?"  and you get similar answers:  "God has always been there."   The last thing I want is for science to go all religious on me.
It seems, to a religious person, quite credible for a God to have created the amazing miracle of "Life, the Universe, and Everything Else" that surrounds us. But point out that, for such a creative God to actually exist in the first place, would be an even bigger miracle, and you make, apparently, an invalid argument. You just cannot use logic with women, anyone upholding religion, or small kids wanting an ice-cream.
     But it has pleased me greatly , that, over the last ten years, the cosmologists have started to ask those same questions about before the Big Bang.    Others, like myself, are even starting to say that the Big Bang was impossible.   I have long suggested, only partly with tongue in cheek, that Hubble got it completely wrong with red shift.   Why could that change in frequency not be due to a loss of energy?   Red light is less energetic than blue light, the energy of a photon being E=hf.  Energy of a photon is therefore proportional to the light frequency.  Maybe the photon loses energy as it fights its way across all those billions of light years, struggling through all the dark matter that our astrophysicists have so carelessly misplaced.  Put simply, a blue photon is ejected by a star some billions of years ago.   It then hits our eye as  a photon of red light at about half past breakfast this morning.   Where has the extra energy gone?    Hubble obviously got it wrong.   That should be the JayZS telescope up there, floating in orbit around the earth.
   Back to the blank night. I was staring up at the clear sky, with all the many stars that were visible, thinking how great it was to be able to see so many ...and...whizzz.....back to the photons!   How many, I wondered, how many photons does a star emit per second, for us all to be able to see it?  Now, you may be thinking that this is not the sort of question to be answered over a commercial break during the latest episode of "Shameless", but out there under the stars, it seemed entirely appropriate... at least for an idiot like myself.  But how to do it? How to calculate it?
I made the assumption that at least one photon would have to hit the eye, and assumed that the eye could detect that,  and with a  frame rate of 10 per second. I had a number: 10,  of photons per second making little dents in my retina.  I then chose to work with the furthest star visible to the naked eye.  I struggled with the internet on my phone, eventually finding that Deneb is a bright star, but at an estimated 1425 light years away, is possibly the furthest visible star.  Choosing this distant object would provide my minimum number of photons required to see a star in the eye.  All that was necessary now was to work out the surface area of a sphere 1425 light years in radius. :-)   The old 4 pi r squared cuts in at this point,  added to a conversion to square metres, and a quick estimation of how many night time eye pupils would fit into a square metre, and suddenly Bob's your auntie.
My answer, worked out with a stick, in the mud at my feet, was 2.4 times 10 to the power 44 photons per second, emitted by the chosen star.   That is quite a lot,
 240,000,000,000,000,000,000,000,000,000,000,000,000,000,000 in real money. Or 2.4e44 to those of you with grade C GCSEs. My sincere apologies to the person who was next to fish the swim.  The mud writings must have confused him.  I am sure he can have no idea of how momentous a calculation had been performed at the very spot where he was standing.  But I had no idea whether that answer was anywhere near being correct.
Later that night, and actually well into the early morning, I wondered whether anyone else had done a similar calculation, and fairly quickly  found one on the internet. A scientist had approached the question from an entirely different angle, and had obtained an answer of 4.2e44.  I was astounded!  His answer was less than a factor of two different from my own, my own answer, engraved in front of me, in the mud, using just a bit of bent stick.  He probably had a slightly bigger star than me. :-( 
I may have caught no fish, but I went home with equally as great a sense of achievement, as I would have had, had I caught a double figure tench that night. 

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