The early technical users in ancient Rome had portable sundials.

In the 4th and 5th centuries, you were a wealthy and cosmopolitan Roman tourist, spanning the whole empire, or maybe an armchair traveler, entertaining other well-educated friends for dinner. What can you do to impress your family? A good choice is the portable sundial in geographical location, which is the closest sundial for the Romans to the iPhone.

These sundials are designed to show time on the move, but it turns out that they are really good at becoming fashionable gadgets. Many of them are made of shiny bronze. They sit on one hand and need real technical knowledge to use them correctly. At present, there are more than a dozen known examples, and each example has a coordinate memo for using the equipment in a specific place.

is a powerful tool more than 1 years earlier than GPS, atomic clock and even practical methods to determine longitude. Richard Talbert, a historian at the University of North Carolina, wrote a new book about this device, Roman portable Sundalials. He said, "If the sun is shining, you will take a portable tool or instrument of your own with you. This is a very personal matter, and you can rely on it to tell you what time it is." Roman portable sundial: The empire "buy" in the hands of the ancient Romans

did not measure time in 6 minutes, but divided day and night into 12 increments, which was a system they adopted from the Egyptians. In Rome, this means about 45 minutes in winter and 75 minutes in summer. The time of meetings, courts and dinners is determined by time, but it is not the elaborate way that many of us experience today.

"When you are 15 minutes late, they won't make an appointment, and they will become impatient," said Alexander Jones, the curator of an exhibition entitled "Time and Universe in Ancient Greece and Rome", who studied the ancient world in new york and explored the relationship between ancient times and time. Denis Savoie, an astronomer who specializes in sundials, pointed out that most sundials don't take more than a few hours. < P > is an adjustable working surface with two nested disks and a pointer for measuring time. (vertical dial? Museum of History of Science, Oxford University)

, but time is the key to the Romans' obsession with astrology, which makes certain days or times hopeful or foretell certain activities. Hundreds of epitaphs indicate the time or age of death of the deceased. Time is important, even if it is not a train or a timetable.

It helps to explain the popularity of sundials. More than 5 sundials have been found, and only 36 sundials have been found in Pompeii, Talbert said. Because sundials need to be calibrated by latitude, most sundials are made of stone and installed in places where they are used.

The portable pocket watch model provides more freedom for car owners to travel, and it still looks like it was then, but it brings more restrictions, not just the price tag. They work in half a day, so you must know whether the sun rises or sets, which may be difficult to determine around noon. They are engraved with popular destinations and exotic latitudes, but there is no guarantee that the list is consistent with contemporary measurement results. On the other hand, you can manually set the dial to any latitude you choose. ) They become less accurate in summer and winter when they are taken farther north. Of course, you must know how to use adjustable position. Jones said: "In the real world, this is a lot of assumptions. One advantage is that they don't need to know which direction is north.

there are multiple models. In one type, the user rotates a smaller disk in a larger disk to represent latitude, rotates a pointer on the smaller disk to represent month, and then hangs the device facing the sun to cast a shadow on the hour mark on the pointer. For another design with three nested rings, the user tilts the innermost horizontal ring according to the latitude, and then rotates the assembly, so that a beam of sunlight can pass through the pinhole to reach the hour mark.