Rockets 101 – How to turn during flight ? 

To be able to control is what distinguishes a toy rocket from a real one. And it is of quintessence to be able to channel the rocket’s direction. To be able to fly is cool, but you what is ever more cool, to be able to pinpoint the destination and its trajectory.

In most modern rockets, this is accomplished by a system known as Gimbaled Thrust.

image

In a gimbaled thrust system, the exhaust nozzle of the rocket can be swiveled from side to side. As the nozzle is moved, the direction of the thrust is changed relative to the center of gravity of the rocket and a torque is generated. As a result, the rocket changes direction. After necessary corrections are made, the exhaust nozzle is brought back to its initial state.

image

The angle by which the rocket’s nozzle swivels is known as the Gimbaled Angle.

Up, Up and Away! 

image

PC: NASA, learnengineering, achingtentacles,campnavigator

Advertisements

This is what happens when Two Black Holes Collide.

This is the animation of the final stages of a merger between two black holes. What is particularly interesting about this animation is that it highlights a phenomenon known as Gravitational Lensing.

What is Gravitational Lensing?

Mass bends Light. What? 

Yeah, mass can bend Light. The gravitational field of a really massive object is super strong. And this causes light rays passing close to that object to be bent and refocused somewhere else.

image

The more massive the object, the stronger its gravitational field and hence the greater the bending of light rays – just like using denser materials to make optical lenses results in a greater amount of refraction.

Here’s an animation showing a black hole going past a background galaxy.

image

This effect is one of the predictions of Einstein’s Theory of General Relativity 

PC: cfhtlensUrbane Legend

Comets have two tails.

There are two types of comet tails: dust and gas ion.

A dust tail contains small, solid particles that are about the same size found in cigarette smoke. This tail forms because sunlight pushes on these small particles, gently shoving them away from the comet’s nucleus. Because the pressure from sunlight is relatively weak, the dust particles end up forming a diffuse, curved tail.

A gas ion tail forms when ultraviolet sunlight rips one or more electrons from gas atoms in the coma, making them into ions (a process called ionization). The solar wind then carries these ions straight outward away from the Sun. The resulting tail is straighter and narrower. Both types of tails may extend millions of kilometers into space. As a comet heads away from the Sun, its tail dissipates, its coma disappears, and the matter contained in its nucleus freezes into a rock-like material.

Comets don’t like the sun.

Comets lose a lot of mass when they go by the Sun. A lot: some shed hundreds of tons of material per second.
That’s actually a small fraction of the mass of a comet, but given
time, and lots of solar passes, it adds up. Every comet we see is slowly
dissolving in space. Eventually even the mighty Comet Halley will be
gone, broken down into a swarm of rocks, gravel, and dust once its gas
is gone.

From Rayleigh to Raman.

FYP has explored Rayleigh scattering in the past. It is the reason why the sky is Blue, Mars is Red but the martian sunsets are Blue and also why the color of the smoke from a cigarette is colorless, but the puffed out smoke is White and so on.

image

But, Rayleigh scattering is the elastic scattering of light i.e the energy( and therefore, the wavelength) of the incident photon is conserved and only its direction is changed. You can consider the Newton’s cradle as an analogy.

image

But this is not the only mode of interaction that can exist. Inelastic collisions are also a possibility. This likelihood brings us face to face with Raman Scattering.

Principle

image

In Raman Scattering, when light is incident on a molecule, the molecules gets excited. As a result of this excitation, the emergent frequency of light is different that of the Incident light.

Awesome, what can I do with that?

If one can extract all of the vibrational information corresponding a molecule, its molecular structure can then be determined. 

For polarizable molecules, the incident photon energy can excite vibrational modes of the molecules, yielding scattered photons which are diminished in energy by the amount of the vibrational transition energies.

image

The vibrational modes for Water and Carbon Di-oxide.

image

“Fingerprinting” the moon.

image

The spectrum of the Raman-scattered light depends on the molecular constituents present and their state, allowing the spectrum to be used for material identification and analysis.

Since the Raman spectra for different mineral tend to have sharp peaks which form a fairly unique pattern, they can serve as “fingerprints” for minerals.

image

Also,since the Raman spectra can be collected remotely, they show great promise for planetary exploration.

image

Thanks for asking !

PC : Chemwiki, wisegeek

EDIT: This post was a brief introduction to Raman Scattering. If you guys have any more concerns regarding the Raman Scattering, please feel free to ask.

Was the Supermoon a ‘Blue Moon’?

The phrase “Once in a blue moon” has nothing to do with the actual color of the moon! When 13 full moons occur in a year, usually one calendar month has two full moons; the second one is called a “blue moon”. 

So, the Supermoon was not a Blue Moon. But July experienced two full moons- one on 2 and 31 respectively. The full moon on July 31 was termed a ‘Blue Moon’,

Blue Moons are a rarity.The next Blue Moon is set to occur on Janauary 31, 2018!! ( I guess, that explains the origin of the phrase ) 

Can the moon ever be blue?

Famously, after the eruption of Krakatoa in 1883, the moon appeared Blue for nearly two years! This is attributed to the scattering of light due to the tiny particles of dust that are reminiscent from a Volcano eruption or from Forest fires.

Hope you guys had a good time 🙂

PC: earthsky, snowbasin

The Big Moon Illusion.

Photographs like the one above are not exactly real. A lot of people are disappointed that the Moon is not big enough. But hey, nowhere in the world is the moon an exact replication of the photographs!! 

They are done using the compression of a telephoto lens. Longer lenses will magnify the subject, so will make the moon look bigger. It will also make buildings and other objects bigger, but by moving yourself further away from those earthbound objects you can reduce them back to a smaller size. But you can’t really get further away from the moon, so it will remain the same size no matter where you move locally.