A BIG BANG THEORY (Part 3)
Time and motion studies
IN my final article on this topic, we might look at some of the theories surrounding the nature of light, waves, and the fabric of space itself.
Much work is currently ongoing into the curious phenomenon of gravitational waves in space – and how the now famous Higgs Boson and its associated Higgs Field might work.
Scientists for years have wondered about the very nature of space itself. They knew that electricity and magnetism had a link, and had a wave like property.
Sunlight (visible light) is actually part of this electro-magnetic radiation which permeates through space and reaches our eyes after about 8 minutes (despite travelling at 300,000 kilometres per second).
The sun emits electro-magnetic radiation at all wavelengths – but our eyes have evolved to be sensitive to that part of the electromagnetic spectrum which we know as visible light; its radiation happens to be most intense in those wavelengths visible to us.
We see the sun as it was eight minutes ago - in effect 8 ‘light-minutes’ ago. Had the light wave taken a year to reach us, the sun could be described as being one light year away.
Light years, despite sounding like a time measurement, are actually measurements of distance.
When you look at the nearest star, Proxima Centauri, part of the Alpha Centauri system, you are seeing is as it was about four years ago.
The reason for this is that any particular photon of light which carries the ‘information’ about the star set off at light speed from the system about four years ago.
Because light speed is fast but finite, and because the distances between Alpha Centauri and us are immense, the travelling time is the key factor.
Imagine then the Andromeda Galaxy, which is at a distance of some two million light years.
The photon of light which today hits your eyes when you look up into the night sky set off from the galaxy when the very first proto-humans were walking the earth.
As we look back into space, so too are we looking back in time.
This realisation caused many scientists in the early 20th C – Einstein being the key one – to surmise that space was not just a three dimensional entity but a four dimensional ‘continuum’ which involved three dimensions of space and one time.
In one of his two theories of relativity (Special and General), Einstein also realised that light was a key constant in this universe – and that ‘events’ in the universe were also relative to the observer and motion.
His theories also called into question the nature of space itself and how things move within such relative to frames of reference.
Prior to Einstein, scientists thought they had pretty much ‘sussed’ how things worked in relation to the movements and motion of objects in space and around the earth.
By the late 1800s they had Newton’s laws of motion and gravity, Faraday’s study of electromagnetic waves, and thanks to the calculations of James Clerk Maxwell and Faraday, they understood the relationship between light, electricity and magnetism.
But they wondered if there might be an ultimate ‘frame of reference’ against which things moved.
Just as today, when a car moves at 60mph, we say this movement is relative to the road. If you watch Top Gear, Jeremy Clarkson does not say that ‘the McLaren F1 can go from 0-60 mph in 3 seconds relative to the road’. This latter part is taken as a ‘given’.
The International Space Station moves around the earth at a given speed, relative to the earth. But, given the earth is in motion too, we could equally say the ISS is moving at a given speed relative to the orbit around the sun. This would be an entirely different figure to the one relative to the earth.
This led scientists to wonder whether there might be some background reference point against which all speeds could be measured – especially light. They called this substance ‘the ether’.
But this notion troubled Einstein, who began to think about the nature of the speed of light.
Einstein was famous for his thought experiments and he imagined one very similar to this.
Let us imagine you are a photographer with a flash gun stood in the centre of a railway carriage, which is standing still.
Your pal is stood on the station platform nearby watching you set up your apparatus and he also has a stopwatch in his hand.
For argument’s sake, let us say it takes one second for the light from the flashgun to reach both the driver’s position and the guard’s position at the end of the carriages.
As you fire the flash gun, you measure the time it takes for each light beam to hit the ends of the carriage. You both agree on the time it takes to reach each end.
But what if the carriage now starts moving at a constant rate?
The photographer on the train presses the flash gun button and sees the light beams hit the guard and driver’s positions simultaneously (presuming they are equidistant).
But this is not the same for the observer on the platform. Instead, as the train passes him, he sees the light beam hit the guard’s position at the rear of the train a few nanoseconds before the other light beam hits the driver at the front of the train. It’s only nanoseconds but there is a difference nonetheless.
If both photographer and observer stopped their watches at the precise moment they believed the light beam to hit the guard (or the driver), both their watches would disagree on the moment of the event.
Einstein realised by such thinking that simultaneous events are relative to the motion of the observer; and that the notion of time itself depends on our relative motion.
He also concluded that any event is relative to a ‘frame of reference’ of the observer, and that the only constant measurement is the speed of light itself.
If the speed of light is the only constant, this led on to the perhaps bizarre concept that time itself is not absolute (as Newton thought). In other words, it is not possible to assign to every event in the universe, a time of the happening of such with which every observer will agree.
Einstein also realised some very strange things happen with light speed.
Imagine for a moment that you are afloat on an anchored boat, ten metres away from a navigational buoy which has a light on top.
If a seagull lands on the buoy and drops a stone into the water, the waves in the water propagate through the medium, until they reach your boat.
Waves in steady water move roughly at 1 metre per second; the speed of such is a property of the medium itself (the water/lake).
Thus after ten seconds, if you remained stationary in your boat, you could expect to see the first of the waves from the splosh of the seagull’s stone pass the bow of your boat.
If you then turned your boat parallel to the wave and set off at a gentle rate of 1 metre per second, in the direction of the wave, you would ‘track’ the wave as it moved through the medium of the water.
What then if, instead of tracking the wave from the stone, you decided to study the wave of light being emitted from the light on top of the buoy?
The photon of light being emitted from this light moves not at 1m/s but 300,000 kilometres per second, roughly. It’s quick.
If the lamp on top of the moored buoy flashes once, it emits a beam which travels at the above speed and hits your eye in the moored boat at this same speed.
What then if a breeze gets up, untethers the buoy, and it begins to move towards you at a constant 10 kph? You might naturally assume that the flash of light was thus moving towards you at light speed plus an extra 10 kph?
Equally, if you set off in your boat at 10 kph, assuming the buoy was still tethered again, you might assume that it might just take that little bit longer for the flash to reach you as you moved away from such.
But Einstein was clever enough to calculate that the speed of light in a vacuum does not change and is independent of the motion of source and the receiver, and their own frames of reference.
This had profound implications. If you set off from the tethered buoy at close to light speed in your boat, you might then expect the image of the lamp to only very slowly catch you up.
Einstein said that this would not be the case; even if you were travelling at the speed of light – effectively riding a light wave – a light beam from another source would not only catch up with you – but pass you at light speed in your own frame of reference.
So while previous scientists were looking for an ether, a background ‘rest’ frame, as it were, against which all things could be measured, Einstein realised that light speed was the constant and all other things has to be measured relative to this. In effect, he turned the cosmos on its head.
If c (the speed of light) was the universal constant, then this would mean that, counter intuitively, there would be no absolute ‘rest’ frame (or ether), nor a notion of absolute time. By absolute we mean a rock solid benchmark against which things could be measured.
This latter idea is the one that gives most people most problems. Newton thought that time was a property that flowed through the universe against a background ether or absolute frame of space, or frame of rest (inertia).
But Einstein said if c was the only constant, even time would be relative to the motion of the observer, and their individual frames of reference as he illustrated in the railway carriage example.
Even though both observers had observed the same physical event – the flash of light inside a railway carriage – because one was in motion relative to the other, both observers could not agree on the simultaneity/time of the event.
To return to the moored buoy example, imagine instead of utilising waves in the water, you initially are stood next to a friend on the buoy.
If you magically had a motorboat that could travel at the speed of light, and you decide to have a jaunt in such, heading out over a lake which, again magically, extends to, say, a few light years in distance.
If you head out at close to the speed of light, to you, you would experience time within your frame of reference reasonably normally; you might only seem to be gone a few minutes in fact from your friend before you decided to zoom back.
But upon your return, thanks to the strange circumstances and time dilations which occur as you approach the speed of light, not only would your friend be a pile of skeletal dust, but the buoy might have disintegrated and all the surrounds, through the process of time, be almost unrecognisable.
To you, minutes might seem to have passed, but to your pal waiting patiently on the buoy, you would seem to have been gone for years and years.
The notion of light being a constant, and the recent studies about the Higgs Boson, suggest that the universe might not be permeated with an ‘ether’ but a Higgs Field which is important in imparting mass to many of the very small particles of the universe.
Professor Frank Close, in his excellent book The Void, also suggests that space itself - even if you somehow hoovered up every particle and elementary field – has a ‘ground state’ vacuum energy, and that our universe may have emerged from a ‘quantum fluctuation’.
The fact that galaxies, as we look at them today, are ‘red-shifted’ – indicating that they are moving away from us (and not just that but moving away at a faster rate the further we look back into the universe) led Hubble to believe that, by consideration, at some point, the universe must have been a whole lot smaller.
At this stage, at the moment of the so-called Big Bang, the universe would have been, for a very brief moment, immensely hot and immensely small; some believe it may have evolved out of a ‘singularity’ similar to those surmised to exist in the centre of Black Holes.
This in turn may have been caused by a ‘quantum flux’, a seemingly chance imbalance in the ‘quantum void’ from which something seemingly appeared out of nothing. But modern day physics breaks down at this point.
Astronomers today are increasingly looking at the Cosmic Microwave Background Radiation to give clues as to the early state of the universe.
The CMBR is a uniform scattering of radiation at the very far reaches of the universe – and is almost uniform is every direction.
The is best explained as radiation left over from an early stage in the development of the universe, and its discovery is considered a landmark test of the Big Bang model of the universe.
When the universe was young, before the formation of stars and planets, it was denser, much hotter, and filled with a uniform glow from a white-hot fog of hydrogen plasma.
As the universe expanded, both the plasma and the radiation filling it grew cooler. When the universe cooled enough, protons and electrons combined to form neutral atoms.
When it was first hinted at, the scientists detected it as a mysterious background hiss, strong in the microwave portion of the electromagnetic spectrum – which they initially put down to possibly being ‘bird-poo’ on their sensitive outdoor equipment.
At that time, unbeknown to them, they had detected the afterglow of the Big Bang.
It is this background microwave field which is still being probed today in the hope of detecting minute fluctuations which might give a clue as to the conditions at the time of the origin of the universe in which the speed of light seems to play such a key role.