Free The Time Ships by Stephen Baxter Page B

if I were suspended over an infinite drop, with only this insubstantial Floor to save me.
    All this was quite illogical, of course; but I amhuman, and must needs pander to the instinctive needs and fears of my nature!
    Nebogipfel observed all this. I could not tell if his reaction was curiosity or confusion, or perhaps something more aloof – as I might have watched the antics of a bird in building a nest, perhaps.
    And in these circumstances, the next few days wore away – I think four or five – as I strove to describe to Nebogipfel the workings of my Time Machine – and as well seeking subtly to extract from him some details of this History in which I had landed myself.
    I described the researches into physical optics which had led me to my insights into the possibility of time travel.
    ‘It is becoming well known – or was, in my day – that the propagation of light has anomalous properties,’ I said. ‘The speed of light in a vacuum is extremely high – it travels hundreds of thousands of miles each second – but it is finite. And, more important, as demonstrated most clearly by Michelson and Morley a few years before my departure, this speed is isotropic … ’
    I took some care to explain this rum business. The essence of it is that light, as it travels through space, does not behave like a material object, such as an express train.
    Imagine a ray of light from some distant star overtaking the earth in, say, January, as our planet traverses its orbit around the sun. The speed of the earth in its orbit is some seventy thousand miles per hour. You would imagine – if you were to measure the speed of that passing ray of star-light as seen from the earth – that the result would be reduced by that seventy thousand-odd miles per hour.
    Conversely, in July, the earth will at the opposite side of its orbit: it will now be heading into the pathof that faithful star-light beam. Measure the speed of the beam again, and you would expect to find the recorded speed increased by the earth’s velocity.
    Well, if steam trains came to us from the stars, this would no doubt be the case. But Michelson and Morley proved that for star-light, this is not so. The speed of the star-light as measured from the earth – whether we are overtaking or heading into the beam – is exactly the same! ’
    These observations had correlated with the sort of phenomenon I had noted about Plattnerite for some years previously – though I had not published the results of my experiments – and I had formulated an hypothesis.
    ‘One only needs to loosen the shackles of the imagination – particularly regarding the business of Dimensions – to see what the elements of an explanation might be. How do we measure speed, after all? Only with devices which record intervals in different Dimensions: a distance travelled through Space, measured with a simple yardstick, and an interval in Time, which may be recorded with a clock.
    ‘So, if we take the experimental evidence of Michelson and Morley at face value, then we have to regard the speed of light as the fixed quantity, and the Dimensions as variable things . The universe adjusts itself in order to render our light-speed measurements constant.
    ‘I saw that one could express this geometrically, as a twisting of the Dimensions.’ I held up my hand, with two fingers and thumb held at right angles. ‘If we are in a framework of Four Dimensions – well, imagine rotating the whole business around, like this –’ I twisted my wrist ‘– so that Length comes to rest where Breadth used to be, and Breadth where Height was – and, most important, Duration and a Dimension of Space are interchanged . Do you see? One would notneed a full transposition, of course – just a certain intermingling of the two to explain the Michelson-Morley adjustment.
    ‘I have kept these speculations to myself,’ I said. ‘I am not well-known as a theoretician. Besides, I have been reluctant to publish without