Wikipedia:Reference desk/Archives/Science/2009 November 22

= November 22 =

Meissner Effect
Explain Meissner Effet —Preceding unsigned comment added by 59.164.72.230 (talk) 11:34, 22 November 2009 (UTC)


 * Have you read our article on the Meissner effect yet?  Sp in ni ng  Spark  11:51, 22 November 2009 (UTC)

Removed responses that stem from a breach of our guidelines - see talk page. SteveBaker (talk) 16:24, 22 November 2009 (UTC)

looking for full moons
I am trying to find out when recently or in the next few years there might be a full moon on the first monday of january, but it seems no moon phase calendars use days of the week. Does anyone know of a better one, or possibly when these particular full moons might have occured.148.197.114.207 (talk) 17:48, 22 November 2009 (UTC)


 * The last one was 4th January 1988. 5th January 2015 is the next one, then 6th January 2042. I am using Michelsen's "American Ephemeris" which has days of the week. Note that the local date of the full moon might vary from these dates which are UT, i.e. for London.--Shantavira|feed me 18:14, 22 November 2009 (UTC)


 * On timeanddate.com you get a calendar with weekdays coupled with dates for the moon phases, but you'd have to browse some years for rare events of course. EverGreg (talk) 20:14, 22 November 2009 (UTC)

The question is underspecified -- the date of any event depends on what time zone you are talking about. So, what time zone are you talking about? --Anonymous, 05:44 UTC, November 23, 2009.

Relativity of simultaneity help in the following case
Please click on the following link

http://en.wikipedia.org/wiki/Relativity_of_simultaneity Section: The train-and-platform thought experiment

Let the train shown in above link (picture) is moving from north to south and the figure represents the front elevation for observer standing on the platform.

There are two other observers A and B in middle of track such that A is in front of the train and B is on back of the train.

For A, front of the train is front elevation while for B back of the train is front elevation.

For observer standing on a platform, A is on his south; B is on his north side while train is moving from north to south in between A and B.

Now a flash of light is given off East and West (instead of north and south) at the center of the train.OR

If the two bolts of lightning strike the longitudinal sides (instead of front and rear) of the Einstein’s train in thought experiment. How the relativity of simultaneity be expressed (for A or B and onboard observers) in aforementioned case? —Preceding unsigned comment added by 68.147.38.24 (talk) 19:28, 22 November 2009 (UTC)


 * The thought experiment is about when different observers observe something. It's not clear in your version how the east-west flash would be seen by anyone but the guy on the platform. EverGreg (talk) 20:21, 22 November 2009 (UTC)

Thanks for your reply. Better, draw a diagram on a piece of paper, it'll just take a minute.

My intent is if we perform the Einstein experiment in such a way that a platform guy change his position and stand either in front or back of moving train and if the two bolt of lights strike the longitudinal sides of train instead of its front and rear then would the onboard the train observer and a guy who stand in front or rear of the train, observe the striking of lights at the same time?

OR

In the same moving train (article picture) if the flashes of lights are fired towards its longitudinal sides (instead of towards cockpit and tail) from the light source at the middle of the train then would the observer that is in front or rear of the train and the onboard the train, observe the striking of light at the same time? Because in this case, to me, velocity of train “v “has no role which is added and subtracted (c+v and c-v) in the subsection of the article for platform observer.68.147.38.24 (talk) 00:08, 23 November 2009 (UTC) K
 * Ok. If the light ray starts in the centre of the train and goes towards the side of the train, the observer in the back cannot see it. You may imagine that he would move forward and intersect the light ray before it hits the wall of the train, but when you draw this you will find that then the train would then have to be moving faster than the speed of light. EverGreg (talk) 09:31, 23 November 2009 (UTC)

My intent is if we perform the Einstein experiment in such a way that a platform guy change his position and stand either in front or back of moving train and if the two bolt of lights strike the longitudinal sides of train instead of its front and rear then would the onboard the train observer and a guy who stand in front or rear of the train, observe the striking of lights at the same time?
 * Yes. Dauto (talk) 16:08, 23 November 2009 (UTC)

If an observer at the back of a moving train use a binocular and starts zooming (condition; zooming speed = speed of train) the aforementioned pulses which were given off from the light source at the center, towards longitudinal sides of train, then? 68.147.38.24 (talk) 07:40, 25 November 2009 (UTC) zarmewa k

Question about gull behaviour (could apply to any reasonably intelligent animal, really)
What's the scientific term used to describe the behaviour that occurs when an animal is feeling conflicted about two courses of action, so instead does a third behaviour, which may be completely nonsensical?

I've been considering this in relation to gulls. Supposing that you know a nesting gull and the nesting gull somewhat trusts you because you feed her regularly. If you approach her nest (say by getting too close to the rooftop she's built in on), her instincts are telling her to swoop down and attack you to drive you away - but she also knows from experience that you're the guy who feeds her regularly, doesn't really want to attack you and possibly gets the urge to fly down and beg for food at your feet (as she has learned that this is how it's done).

So she does neither. Instead, she shifts around uncomfortably, makes odd gabbling noises, alternatively tenses and relaxes her muscles and stares down at her feet until you go away. Yes, this really happens. A gull that doesn't know you will just attack if you don't back off.

Anyone know the name for this? I was thinking displacement, but from reading our article, this term doesn't seem to entirely cover it. --Kurt Shaped Box (talk) 23:36, 22 November 2009 (UTC)
 * This seems to have been discussed here: Reference_desk/Archives/Science/2009_October_3. --Mark PEA (talk) 08:58, 23 November 2009 (UTC)


 * The article Displacement activity seems to deal more specifically with behaviors such as the one you note. This discussion of "sparking over" may also be of interest. Apparently, such behaviors have been especially noted in birds. Further discussions (such as the one beginning at the bottom of this page) can be found by Googling for "displacement reactions" +birds and similar combinations of terms. Deor (talk) 09:12, 23 November 2009 (UTC)


 * I don't know if this would be of interest. Bus stop (talk) 09:19, 23 November 2009 (UTC)