Feature

The First to See the Light

Much controversy exists as to where the first sunlight will fall in the new millennium. Will it be in New Zealand?

Brian Carter

Who will be the first to see the Sun at the dawn of the new millennium? Before that can be answered, we need to answer the question of "What is the sunrise?". Sunrise is defined as the time when the top limb (topmost edge) of the Sun is level with the horizon. The time of Sunrise varies throughout the year, because:

• the North/South pole axis of the Earth tilts at an angle of about 23.50 with respect to the Sun
• the Earth is moving round the Sun
• the Earth's orbit around the Sun is slightly elliptical

Calculating sunrise times is a complicated spherical trigonometrical problem, as not only is the Earth spinning on its axis but the position of the Sun appears to move because the Earth is moving around the Sun. There are six factors that need to be taken into account when calculating sunrise times.

Longitude
The further east one moves, the earlier the Sun rises, until the International Date Line is reached when the date changes to the previous day.

Latitude
In the Southern Hemisphere's summer, the further south one moves, the earlier the Sun rises, until a point in the Antarctic circle is reached when the Sun is always above the horizon.

Altitude
The higher above sea level one moves, the earlier the Sun rises. This is not a linear function as the correction depends on the square root of the height above sea level. The corrections, in New Zealand, for altitudes of 1,000, 2,000, 3,000 and 4,000 meters are approximately -7, -10, -12 and -14 minutes respectively.

Horizon
The horizon to the east of the observer is critical. If there are hills or mountains to the east, the sunrise will be delayed as the Sun has to rise higher in the sky before it becomes visible over the obstruction. Although it would be feasible to calculate this correction for any location, practically it would not be attempted as the correction makes the sunrise later. For this reason, it is assumed that the horizon is at sea level.

Atmospheric conditions
The Earth's atmosphere refracts -- that is, bends -- the rays of the Sun (or any other astronomical body), making it appear to be higher in the sky than its actual position. The refraction increases rapidly the closer the Sun is to the horizon. The effect of this can be clearly seen soon after sunrise or as the Sun is about to set -- the Sun appears to be squashed, as the bottom of the Sun has been refracted upwards more than its top.

In sunrise calculations, average atmospheric conditions are assumed and an angle of 34" (just over half a degree), is used for the horizontal refraction. To give you some idea of the size of this angle, the Sun is about 32" across. So, soon after sunrise, when you can just see the whole of the Sun, it is actually all still below the horizon. Sunrise times always refer to the Sun as we see it, and not its true position.

Weather
Obviously, if it is cloudy, it will be impossible to see the sunrise. Only on the appropriate day and location will this factor be known.

If, like the Moon or Mercury, the Earth did not have an atmosphere, then only the first four points would need to be considered in sunrise calculations and it would be theoretically possible to determine the time to a fraction of a second.

Fortunately for life on Earth, our planet does have an atmosphere, but unfortunately it makes the sunrise time very uncertain. As stated earlier, average atmospheric conditions are assumed but the actual times can vary by three or four minutes. It is therefore pointless to calculate the sunrise times to better than the nearest minute.

When calculating sunrises (as well as other parameters), I normally use the Interactive Computer Ephemeris (ICE) produced by the Nautical Almanac Office at the US Naval Observatory. ICE only calculates the sunrise times to the nearest minute and does not take into effect altitude, as it was designed for navigation at sea, where, hopefully (not so for the Titanic!), both the ship and horizon are at sea level.

There are several other computer programs available, some of which give the sunrise times to the nearest second or even a fraction of a second (which shows little knowledge of the errors involved in the calculation). They each give different answers, but appear to agree to the nearest minute with ICE. I have little faith in their accuracy when I read phrases like "the minor effects are neglected" and the "formula ignores", but these programs still give answers to a fraction of a second.

Added to all this is the fact that I am uncertain that the average refraction value used in the calculations is valid for positions not at sea level, so you can see why I am sceptical. This would be equivalent to determining the area of a circular field by measuring the diameter by pacing across and using 22/7 as a rough approximation for p, and then saying the area is accurate to a square millimetre!

The Carter Observatory does not wish to get too involved in the debate about which place will see the first sunrise in 2001, mainly because we would not like to spoil the fun of the many contenders vying, for commercial reasons, to be "top dog". However, we have calculated sunrise times for a selection of locations. We do realize all of the islands and some of the locations will have hills or mountains in the vicinity but, apart from the two mountains on New Zealand's mainland, we have assumed an altitude of sea level. We also assume that New Zealand Daylight Time (UT + 13 hours) will still be in operation in 2001. (Balleny Island almost beats the Antipodes Islands but at that time of year the Sun does not fully set below the horizon and therefore cannot rise again.)

The Sting in the Tail

In fact there are two stings in the tail that spell the death knell for a New Zealand location being the first place to see the sunrise in 2001.

Firstly, the date of the start of the new century and new millennium has been fixed, but at what time does it start? An International Conference was held in Washington in October 1884 for the purpose of fixing "A Prime Meridian and A Universal Day". Resolution One resolved to adopt a prime meridian, while Resolution Two decided that it should be through the Airy Transit Circle Telescope at Greenwich in London. Resolution Five decided that the day is to begin "for all the world" at midnight at Greenwich.

This means that the "new dawn" for all the world does not start until 00:00 UT (GMT) which is 13:00 NZDT (1 pm). By that time, the Sun will have already risen in New Zealand and therefore a location to the west of New Zealand will get the honour of seeing the sunrise first in the new millennium.

It has been suggested that the Katchall Island in the Nicobar Islands has this honour, but of course many locations in East Asia could also be in the running. It is however possible the above is negated by Resolution Four at the 1884 Conference which states that the "universal day shall not interfere with the use of local or other standard time where desirable".

Secondly, the Ministry of Foreign Affairs in the Republic of Kiribati announced that from January 1 1995, all the islands in their jurisdiction would be on the same day. This has caused a massive dent in the International Date Line to accommodate the most Easterly Kiribati island. You may ask how can the International Date line be unilaterally moved by a nation.

The simple answer is that it is neither international nor even mentioned in the Conference of 1884 and therefore can be changed by anyone at will. It would, however, seem more logical to move the International Date Line slightly to the west to include the main islands of Kiribati, but this obviously would mean that Kiribati would no longer be a contender! If we accept Kiribati's argument, then Caroline Island (10^o 00" S, 150^o 14" W) has the earliest sunrise.

And finally, you have to bear in mind that the Gregorian Calendar was adopted in 1752 in Great Britain and her Dominions, and is only one of about 40 calendars used in the world today, so it will not be everyone who will be celebrating the coming of the new millennium on January 1 2001.

Brian Carter is senior astronomer at the Carter Observatory in Wellington