Well, one cannot start early enough I guess.

What I would like to know if any of you know of some simple experiments I could incorporate in my christmas seminar. The topic is "the science of christmas" (based on the book "the physics of christmas" which I don't have yet but is on its way from amazon).

If you know a nice experiment (with dry ice, or something electrical, or ...) relating in some way to Xmas, please tell me.

Thanks a bunch
M

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
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“A good scientist has freed himself of concepts and keeps his mind open to what is”
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You could calculate the speed Santa would need to remain at in order to get enough time dilation to have time to drop off presents at all those houses. He'd have to essentially "orbit" each house for, let's say, a minute to offload the packages. His acceleration would cause no difficulty for the time dilation, but it might produce gravitational radiation for all I know. Anyway, if it's 1 minute per house and it's 50 million households (at least for the U.S., other countries are responsible for their own myths!), that's about a million hours that has to get compressed into at most 10, so we'll need a gamma of 100,000, which means better than 1 part in 10¹⁰ below c. That could also explain why he's never seen!

Perhaps the percentage of naughty kids is much higher than you think.

You can explain the events of frostbite and how it effects a human being, but thats not a experience. Well I guess I didn't help you oh well.

You could measure the solstice. Fix a stick (or a sheet with a hole allowing the sunlight through to a point marker) so it casts a clear shadow/point on a marker page set perpendicular to the sunbeam at noon. Mark the heights of the shadow every day at noon from December 15-31, and hopefully show the shortest days and longest shadows (if you are in the northern hemisphere) are from 22-25 December.

Lets make this thread legitimate.. re; A question about christmas.... or not.

Why?
or to expand on this, ... why bother?

Although wildly excepted by the western nations as a festival of the birthday of Christ. It is not well understood what any of that has to do with this Santa Clause falla... and as to why this religious event has become such a commercial occasion is beyond me... and I can not draw any astronomical significance into or from any of it, can you?
But then there was that star * Could that have been Omega cent.,?

Winter solstice ? The days become longer again...

I saw one episode of Mythbusters where they did the "Christmas lights on a tree overnight will catch fire" myth and showed that they don't, but that it was possible to overload sockets with multiple extension blocks and cause a fire that way.

Of course the obvious one if you want to keep the religious theme and astronomy, although you may have to had astrology (history of) but only in the anthropological sense and discuss the Star of Bethlehem. What could it be and what could it not be, so you get to discuss all sorts of astronomical phenomenon and use images and simulations to keep interests.

BTW my favourite explanation for the SOB would be a conjunction of Saturn and Jupiter in the constelation of Aries the Ram. The two planets meant a king was to be born, Aries was the symbol representing the Israelites. Because the Israelites shunned astronomy, it was astrologers / astronomers from other lands that spotted it.

Another idea, if you can get a large piece of meat, a microwave and a band saw, show how something may look cooked but isn't. This was also done on Mythbusters when they did Microwave Oven myths

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SOB...good one, Sticks!

My favorite theory about the SOB is it's obviously the product of someone's imagination.

The only celestial object that would have remained for days over a particular location in the land just east of the Mediterranean would be a geosynchronous satellite. Instances of these occurring naturally are quite rare.

BTW, Sticks, did you know your BAUT number is 1069666?

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Umm.. well... err... I live in New Zealand so its near to our sumer solstice. Just four days off... But the original idea from Europe might have been the date for some celebration of the solstice, yep I'm happy with that.

Well, I did the history of christmas already a few years ago, including the SOB. I am looking for small experiments:
e.g. baking cookies with liquid nitrogen

But thanks for the replies and all, they are well appreciated. Keep them coming!

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善數, 不用籌策 (shàn shù, bù yòng chóu cè)
He who is good at counting, uses no counting tools
“A good scientist has freed himself of concepts and keeps his mind open to what is”
道德經, 二十七 (dào dé jīng, 27)

Do an experiment to see which "Star" the 3 wise guys were really following, and what time of year it really would have been AND which year!

How about the idea that all snowflakes are different? Maybe you could get them on a frozen slide in a microscope.

How about Xmas food - where it comes from?

In the UK, we eat turkey, from North America, garnished with potatoes from South America, gather around a Scanadavian or at best Germanic fir tree and eat dates and tangerines from the Middle East.

John

A colonization ship leaves for Alpha Centauri accelerating at ¼ gravity. Santa's sleigh can accelerate at ½ gravity for each reindeer pulling. Eating one reindeer can keep Santa alive for a month. A reindeer can't pull at all while being eaten. How long will it be before Santa is physically unable to deliver toys to the kiddies on the ship each Christmas.

Trying to stay on Astronomy or at least science...

What about where Jesus went when he ascended?

Was it to another place? Or time? Was he even earthly?

Was he interdimentional?

There have been many times in history where people used knowledge of astronomy to screw with simple people. Even as simple as knowing when there would be the next Solar eclipse.

Comets were thought to be sailing ships of the gods.... etc.....

Or maybe...

Try to study how much time need for the Three Kings to travel from where they came from by Camels, there's no means of transportation that has engine and needs fuel at that time, compare it if they used a car and see the difference.

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25 December is the day the point of sunrise starts moving north, after three days (from 21/22 December) apparently standing still at its southernmost point on the horizon. Hence the name solstice means "Sun Still". In the Northern Hemisphere 25 December is the first day that is longer than the previous one, after months of lengthening nights, and so marks the start of the movement towards warmer weather in summer.

It would be a handy experiment to fix a telescope pointed towards the sun at dawn or noon or dusk over a few weeks around Christmas and (without looking at the sun!) mark the positions at the same time each day on a fixed surface where the sunlight is focused through the telescope lenses. Scientifically, this can show how the angle of the axis of the earth determines the annual cycle.

Re the astronomy of the solstice and the role of Christmas in Christianity, I have heard it said that the three days each year in which the dawn point is the same from 22-25 December have a link, through the idea that the sun metaphorically dies and comes back to life, to the Easter story, in which Jesus dies and comes to life on the third day.

I have news for you.

The winter (in the northern hemisphere) solstice is an instantaneous event occurring at a particular second, minute, hour, and day for any given year. As soon as that moment is past the Sun apparently starts moving north in the sky again.

Since the angle of the ecliptic at sunrise around the time of the winter solstice is very oblique (for the northern hemisphere), the point of sunrise also starts moving north immediately.

The winter solstice for 2007 is at 12:08 AM CST. This is also the shortest day of the year. By the time December 25th rolls around the day is 12 seconds longer for folks near the 45th parallel.

Here's a calendar of sunrise and sunset times, plus day lengths for Chicago, Illinois, USA. As you can see, the shortest day is the day of the solstice.

Of course for folks well north of the Arctic Circle, all this sunrise stuff is meaningless, since, depending on their location, latitude-wise, it will be some time before they see the sun again. Plus it's interesting how actual sunrise/sunset times are calculated in the realm of astronomy. Here's a précis from the US Naval Observatory that sheds light on this subject.

There is nothing special about December 25th, except as an example of the inexact calendar, astronomy, and math skills of the early Jesusian church fathers when they attempted to commandeer the winter solstice celebrations.

Therefore what you've written about December 25th being the first day the point of sunrise moves north and its being the first day to be longer than the previous one is wrong.

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However, it is true that it is probably one of the earliest days upon which the lengthening and motion of the sunrise would begin to be noticeable given the astronomical methods available when the date of christmas was set on the 25th...

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I doubt that is what happened since the difference in day length is only a few seconds. It's quite a while after the solstice that the days become noticeably longer qualitatively, even by marking time, due to the very inaccurate timekeeping technology of that period in history. The solstice was instead marked by calendar keeping and in many places devices that allowed for light or shadows only when the Sun had reached its lowest point at noon. In short, the difference between evidence by attributes and evidence by variables.

I would tend to go with Robert Tulip's theological explanation (exclusive of any kind of input of observational evidence) as the reason for choosing the 25th. Just numerology, plain and simple.

Since accurate information about astronomy and geometry had been either lost or suppressed at that time, the PTB would not have realized that the crest or nadir of a sine wave is not flat.

Coming to an incorrect conclusion due to a lack of precision and accuracy in one's measurement methods or in one's fundamental knowledge, is still coming to an incorrect conclusion.


Meanwhile I see it appears the problems created by the reports of a star-like object remaining above a particular Earth location for many days are being conveniently ignored. Remember, due to the Earth's rotation, everything in the sky, except geosynchronous satellites and the occasional meteor, appears to move from east to west as the hours go by.

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The actual day of Jesus' birth was closer to April 19th and not 2007 years ago. Closer to 2011 or 12

The wise men showed up around December.

oh.. and you do something about sociology too. (still scientific)

Mary was likely only about 12 or 13 when she married Joseph, and likely was not his only wife.

By “apparently” I meant to the ancient stargazers. The movement north of the sun is of course instantaneous on the moment of the solstice, but for amateurs its measurement can be done by checking its position at the same time each day. It is interesting to link observation and mathematics by experiment.

This is what I was suggesting people could do as a scientific Christmas experiment – like Stonehenge or Karnak. - http://sunearthday.nasa.gov/2005/locations/elkarnak.htm

However, in this case for the three solsticial days the sine curve of the solar position on the horizon was flat enough to make the days seem the same length, especially before people had clocks, compared to the more rapidly changing length of the days before and after.

Is there a northern latitude above which the sun disappears for three days until Christmas?

I always thought the date issue sounded like a calendar conversion error. Most of the Christmas traditions are simply pagan winter solstice holiday traditions relabelled, and they knew how to determine the day of solstice. But the calendars that were used in the past weren't the same as ours, so the solstices in the past could have been on different dates from the ones we expect now, before some new rule for calendars took effect.

Looking at the planets at Christmas is interesting. Attached picture shows Jupiter and Pluto near each other and Venus on the ecliptic on 23 January 2008, soon after the Christmas conjunction of Jupiter, Pluto, Sun, Mercury and the plane of the galaxy. Counting Pluto in and 2000 out (if I may), this passage of Jupiter past Pluto is the first trans-Martian planetary conjunction of the millennium. Jupiter is now next to the red giant Antares in Scorpius in the evening sky, moving towards the Milky Way and Sun and Pluto in Sagittarius at Christmas. (And on a non-Christmas point), in the picture attached I call the ring of stars in Pisces next to Uranus the Vitruvian Man. It is right on the equinoctial point where the ecliptic crosses the celestial equator.

Attached Images

Sky 23.1.08.jpg (140.0 KB, 10 views)

I agree with you on dates, Dennis-le-Petite made an error in the sixth century, but I suspect that discussing this further is a violation of forum rules concerning no religion.

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Same site gives attached for length of days in Sydney Australia at the Christmas summer solstice. It shows 7 consecutive days that are the same length - 14 hours 25 minutes - from 19-25 December 2007, and two weeks from 15-28 December when the length is within one minute of that (>=14h24m). By comparison over two weeks in November the day lengthens by 27 minutes. The rate of change of day length slows close to zero at Christmas.

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Sydney Solstice 2007.JPG (85.3 KB, 9 views)

Delvo is correct about the calendar conversion issue. According to the Julian Calendar, which was established by Julius Caesar, the actual Winter Solstice fell on December 25. It was celebrated as Dies Natalis Solis Invictus, the birthday of the unconquerable sun. Because people would never give up these celebrations, the church basically co-opted them and re-assigned them Christian meanings (i.e., the birth of the Son instead of the rebirth of the sun). Sometime in the 1500s, Pope Gregory (I don't what number) substituted a new calendar called the Gregorian calendar for the Julian, which was out of sync with the seasons because of having too many leap years. The Gregorian calendar tried to correct for that by eliminating years that begin centuries (1700, 1800, 1900) from being leap years unless they are divisible by 400, which is why 2000 was a leap year. However, the date of Christmas celebrations had by that time become so entrenched; the church discouraged any connections with the solstice, so the now incorrect date of December 25 simply stuck.

Even leading authorities of most Christian denominations today acknowledge that the most unlikely season for Jesus' birth was winter, as the Romans would not have conducted a census requiring travel during what in Israel is the rainy season.

As for the star of Bethlehem, one theory is simply that it is another symbolic interpretation of the distant sun, a lone light shining during the darkest time of year. The sun was in fact viewed by ancients as dying and coming back to life at the winter solstice. Another conjecture is that the star was Halley's Comet, which made a very close approach to Earth around 11 BCE.

Jesus was a real human being. I am not discussing religion.

I'm discussing the point of the topic. Science involving Christmas.