Earth precesses around its axis every ~26000 years.
But in addition to this precession, there is an extra wobble that was observed by Kustner and later followed up by Seth Carlo Chandler, Jr called the Chandler Wobble that occurs at a much smaller time scale.
In 1888, Kustner found that the latitude of Berlin had changed slightly
during his observations of the night sky.
Therefore in 1891,Chandler. decided to conduct a 14 month study examining this change. The following is a plot of the spiral path taken by the earth’s axis over that 14 month period.
The following plot shows the motion from 1909 – 2001.
Although many theories indicate that this is due to the fact that earth is not a perfect spherical rigid body, it is still not entirely clear on the mechanism that drives earth into this small wobbly motion.
If you took a closer look at the plots you would find that this wobble is of the order of a couple of meters which most certainly does not seem like a lot.
But if you are an astronomer if you do not account for this correction, you might just end up pointing your telescope at the wrong object
Having recently attended a workshop at the Lick Observatory and the opportunity to observe at the telescopes there, this is the raw data of the pillars of creation that we were able to capture using the Nickel Telescope whilst there.
Exposure time: 300 seconds
Location : M16 (Eagle Nebula)
This image needs to reduced even further to correct for the anomalies in
color that one can observe on the image and that’s something we are
currently working on. We hope to share the entire data with you in a month’s time after post-processing.
The overhead lines are kept in tension and dropper wires are placed at multiple locations to ensure that the contact wire does not bend under its own weight.
And since any two objects that rub against each other, constant frictional contact would wear them out, the Pantograph and the contact wires have a sliding contact.
This results in less wear for both the Pantograph and the contact wires resulting in lesser maintenance.
Graphite conducts electricity extremely well while also working great as a lubricant due to it’s self-lubricating properties and therefore most contact strips on the Pantographs are made up of Graphite.
It’s a very simple apparatus with an extremely pivotal role and that’s what makes the Pantograph special. Have a great day!
*** Arcing is a serious problem when we are dealing with any high voltage lines. in bullet trains which operate under higher voltages, the Pantographs are always forced to be in contact with the contact wires through a dynamic lever-spring mechanism. (Source)
One cozy evening, I gazed a lazy look to the surrounding. From the looking glass of a Lazy individual everything looks dull.
But once my vision tuned in on the Smart Phone, it struck me that I had no idea how this thing works but yet have been using it constantly for years. Time to disparage the boredom !
This is an account of the bewitching touch screen world. All Aboard!
The Resistive Touch Screen
If you have used a mobile phone in the distant past that involves you pressing down hard on the screen, then there is a great possibility you have used a Resistive touch screen.
Some examples are the Nokia N800, Nokia N97, HTC Tattoo, Samsung Jet or the Nintendo DS.
How does it work?
This is the traditional form of a touch screen and its working is rather blunt. There are two conductive sheets present that are separated by spacers.
When you press your hand against the screen , the top layer gets pressed and
makes contact with the bottom layer. This completes an electrical
The act of pressing reduces the resistance between the two conductive plates. (because you are reducing the distance between these two conductive plates and resistance is dependent on the length of the medium)
The voltage established as a result of this change in resistance is measured and the coordinates of the point of contact are determined.
The harder you press, the more the change in resistance.
This is one of the frustrating things about this type of touch screen.
Resistive touchscreen require slight pressure
in order to register the touch, and are not always as quick to respond.
But they are used in many low-budget mobile phones like the Freedom 251, which is a touch screen phone for $3.75.
The pixel arrangement on a screen need not be periodic like shown above. In fact ,most manufacturers have their own unique type of representation ( see below )and the type varies with the type of application as well.
As an amateur physicist you do not have a microscope but only a green laser as your tool, how would you go about finding which one of these arrangement your smartphone has ?
Visualizing pixel spacing using a LASER
For a fact, you know that:
if you shine a red light on a green or blue object, it will
Colors are nature’s way of expressing beauty. And we often find ourselves in this situation where we want to capture this ecstasy. A camera rose out of this innate longing to capture and invariably store these memories.
Generally when people are on the lookout for buying new phones/cameras, one of the parameters that is looked into is the MP(Megapixels) of the camera.
2.0 MP means that there are ~2million ‘effective’ pixels on the image that has been captured. *
But,what is a pixel ?
Pixel ( or picture element ) is a small element on the screen that represents a specific color.
But how do you represent any color – with the primary color system of course!! Add the red, blue and green in varying proportions and voila! you can span the entire color spectrum. **
Therefore,every pixel is constituted of 3 ‘compartments’ – Red, Green and Blue to produce the necessary color distribution of an image.
The subtlety of a screen
Wait!! Hold on are you saying that there are millions of red, green and blue lights on my screen ?
Don’t believe me ? Take a took at these images of a smart phone screen under 30x and 60x magnification.
One RGB block is called a pixel. Video Source : Microworld
Now this ‘array type of arrangement’ is not necessarily the case with all manufacturers.
In fact, most manufacturers have their own unique type of representation ( see below )and the type varies with the type of application as well.