Three Trips in a Tardis Trip 1

When I was offered the idea of three trips in a Tardis I thought that I would like to visit Mr. Eratosthenes. Then I decided that just one trip would not be enough so I have unilaterally decided that the Eratosthenes idea should be a project which would involve several trips.

It is well known that the Doctor can speak in English to any aliens he meets and they reply in English. (This excludes the episodes of Dr. Who seen in most other countries in Europe. In which cases Dr. Who and his adversaries speak in French, German or some other common language.) I will therefore assume that I will be able to communicate with Mr. Eratosthenes in English. Nevertheless, it would seem that Mr. Eratosthenes was no mean linguist in his own right. He was born in Libya and died in Alexandria at the age of 62. In his life he went to Athens and became the director of the Great Library of Alexandria. He was a pretty bright fellow for his time.

Mr. Eratosthenes is famous for being the first man to try to measure the circumference of the Earth. His works were recorded by a Mr. Pappus, another bright man for his time.

Mr. Eratosthenes found that on one day a year that the sun was exactly overhead in the region we now know as Aswan. This was confirmed by the reflected image of the sun in the water of a very deep well. He also noticed that on the same day at the same time of year, the shadow of a stick at Alexandria was at its shortest. (Mr. Eratosthenes also worked on calendars so he knew his dates.) He able to compute the circumference of the Earth from this limited amount of data. His figure is reckoned to be around 25,000 miles. The approximation is because there was no standard for the length of a stadium - the ancient equivalent of the mile or kilometre - and land surveying was in its infancy at the time. I would guess that Mr. Eratosthenes would have tried hard to make his measurements accurately but his equipment and resources were rather limited. This is why I want to meet Mr. Eratosthenes. I could help him quite a lot with the aid of the Tardis.

History does not record when Mr. Eratosthenes did his measurements so I will assume that he did his work when he was between 25 and 30. This gives us a date of around 250 BC. We can guess that he was in or around Alexandria at the time. He must have been quite famous so it would be fairly easy to track him down. Once he had been found he would be offered a trip in the Tardis to our present day. We would then look for any landmarks which have existed for more than 2,000 years in Aswan and Alexandria. We would then get their positions with GPS and calculate their great circle distance apart. (The Tardis would make commuting between Aswan and Alexandria much simpler.) We would then pick a convenient time to be in both places at midsummer. (The Tardis is ideally suited to being in two places at the same time.) The elevations of the sun at Aswan and Alexandria would be noted to compare the circumference calculated by this means with that obtained by GPS.

It would be explained to Mr. Eratosthenes that our GPS receiver would not be of much use to him in his own time but he could keep it as a souvenir. Then we would begin to make the return journey to his own time. We would stop by at Mr. Harrison's workshop and obtain one of his chronometers for Mr. Eratosthenes to keep.

When we got back to Mr. Eratosthenes' time, I would tell him to remove the batteries from the GPS receiver because they could leak and corrode the works.

For all I know, someone may have had the equivalent of a Tardis and visited Mr. Eratosthenes in Alexandria. If there were any records of such a visit, they were lost when the Great Library of Alexandria was burned down 1700-odd years ago.

Three Trips in a Tardis Trip 2

My second Tardis project would be to visit Tycho Brahe.

Tycho was the first person to put the stars in their proper places on the map of the heavens. He had special instruments made so that he could observe the right ascension and declination of stars with fair accuracy. He was supported by the then King of Denmark who gave him an island to use for his observatory.

Tycho was unfortunate because he died before Christiaan Huygens invented the telescope. The fact that he did not have a telescope to use made his observations particularly remarkable for the time when he made them.

Tycho devised his own modified version of the solar system devised by Mikolaj Kopernik. If he had had the use of a simple telescope, he would have been able to to obtain a much better understanding of the movements of the planets.

He discovered a nova in in Cassiopeia and proved that there was a star at its centre. I feel that he should have had a bit more help with his observations and should be rewarded for his efforts.

I wanted to take him a big present but the door of the Tardis is too narrow for anything very large to be carried through it. After some consideration I have come the the conclusion that a 12 inch Meade telescope would be both big enough and small enough at the same time.

When King Frederick II died, Tycho's supply of funds dropped to almost zero so he left his island observatory and went to Prague. He was only able to take a few of his instruments with him so he could not carry on with his observations with the same degree of accuracy as before. If he had had a reasonable telescope, he could have produced even more outstanding observations and saved Galileo a lot of problems with politicians masquerading as priests.

Tycho's pupil was Johannes Kepler. If Tycho had had a good telescope to use, his observations would have been more accurate and Johannes would have been saved a large amount of work. With the aid of the telescope, he and Johannes could put together a more accurate star catalogue. When they had produced it, it should be kept a secret. Johannes should keep a copy of it to be taken to England by a trusted young person. The young person should arrange that on his death, the catalogue should be addressed to a Mr. John Flamsteed of Greenwich.

I would also take Tycho to see and visit the crater on the moon that was named after him. After that he could die happy in the knowledge that he had a monument which will outlast the pyramids.

Tycho's great work made it possible for sailors to plot their routes more accurately. A 12 inch Meade telescope would be but a small acknowledgement of the debt that all navigators owe to him.

Three Trips in a Tardis Trip 3

After, or before, or at the same time as visting Tycho Brahe I would also like to visit one of Tycho's contemporaries, Gerard de Cramer. While Tycho was looking at the skies, Gerard was looking at the earth. Gerard de Cramer is not well known today under his original name because he adopted another name which every schoolby knows - Mercator.

Gerard became an instrument maker and gained an interest in geography. He was an excellent calligrapher and desisigned his own italic typeface. He had a bit of trouble with religious authorities and was imprisoned for seven months. He was lucky enough to be found innocent of heresy in the end and was able to get on with his work. He was sponsored by the Duke of Cleve in Duisburg and did an amazing amount of biblical work in addition to his map making.

Mr. Mercator wanted to produce a way of making maps more consistent and useful to marine navigators and eventually ended up with a cylindrical projection. This enabled mariners to plot straight courses from A to B on his maps. Although his lines of longitude were parallel, and the shape of the earth was distorted to fit, his maps made life easier for navigators. At all points along a route, the course was always at a constant angle with respect to lines of longitude. If seamen steered with a compass pointing in a constant direction, their tracks would follow fairly short routes. (Great Circle routes are marginally shorter.) The course corrections required because of the curvature of the earth would be almost unnoticeable during a long sea journey.

Everyone is familiar with the appearance of Greenland as large as Africa on a Mercator projection but nobody seems to mind very much. Humans cannot handle three or four dimensional maps very well so the distortions produced by a flat, two dimensional map have become acceptable. It is a different story on Gallifrey where four dimensional maps are an essential requirement for Tardis navigation.

I have wondered what I should take from our time to Mr. Mercator to give him a reward for his work and a way of inspiring him to continue with it. At first I thought that I would take a copy of the latest Times Atlas of the World to honour Mr. Mercator's invention of the term Atlas. Then I thought that it would discourage him because he would see how modern technology has made his work seem pitifully crude. After some consideration I decided that I would treat him in a similar manner to the way I treated Mr. Eratosthenes.

I would arrange to visit him just before the end of his term of imprisonment and bring him back to our time for a few days. With the aid of the Tardis I could show him the whole Earth from a height of 1000 miles. We could spend a day or two suspended above local Earth noon and watch the scenery go by. (Please remember that the Tardis does not have to orbit to maintain a constant height above a planet.) I would guess that he would like to spend an hour or two at fifty miles above the German-French border so that he could get a clear view of Lorraine. As I am British, I would also like to give him the chance to see the whole of the British Isles for a day so that he could visualise the map of Britain that he would produce later.