Mysterious Dark Matter - invisible !

Swiss astrophysicist Zwicky was the brainy human who did a research on "Missing Mass Problem."

He did a close comparison.He examined the galaxies and analyzed their brightness which inturn helped him to calculate the mass.The interesting result was that he got 400 times more mass than expected.Based on this conclusion, Zwicky inferred that there must be some other form of matter existent in the cluster which we have not detected, which provides enough of the mass and gravity to hold the cluster together.A small portion is contributed by Baryonic dark matter.It is the dark matter (matter that doesn't emit light) composed of baryons, i.e. protons and neutrons.In cosmology, dark matter refers to matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation to be detected directly

Evidence of Dark Matter

Many of these appear to be fairly uniform, so by the virial theorem the total kinetic energy should be half the total gravitational binding energy of the galaxies. Experimentally, however, the total kinetic energy is found to be much greater: in particular, assuming the gravitational mass is due to only the visible matter of the galaxy, stars far from the center of galaxies have much higher velocities than predicted by the virial theorem.

Dark matter affects galaxy clusters as well. X-ray measurements of hot intracluster gas correspond closely to Zwicky's observations of mass-to-light ratios for large clusters of nearly 10 to 1. Many of the experiments of the Chandra X-ray Observatory use this technique to independently determine the mass of clusters.

Composition of Dark Matter

Since it cannot be directly detected via optical means, many aspects of dark matter remain speculative.

Galaxy rotation curves, gravitational lensing, structure formation, and the fraction of baryons in clusters and the cluster abundance combined with independent evidence for the baryon density, indicate that 85-90% of the mass in the universe does not interact with the electromagnetic force. This "dark matter" is evident through its gravitational effect.

Hot dark matter consists of particles that travel with relativistic velocities, one of them is known as "the neutrino". Neutrinos have a very small mass, do not interact via either the electromagnetic or the strong nuclear force and are therefore incredibly difficult to detect.

MOND THEORY
Modified Newtonian Dynamics proposes to modify (F = ma), which then modifies the gravitational effects of mass. MOND predicts that Newton’s law is valid except when mass is accelerating very, very slowly. And, galaxies and systems of galaxies indeed accelerate very, very slowly over very, very long times.The MOND theory is as successful at explaining the astronomer’s observations as more standard models that assume the existence of dark matter.But this theory also has its own set of problems.

In the end, I would like to leave you with a quote

"If we accept a departure from the standard laws of physics, we might do away with dark matter."

Reverse Sprinkling

Herez a puzzle:

I hope every1 has seen those water sprinklers spraying water in a garden. Nice little things they are, for they rotate by themselves throwing water around! Its obvious that laws of momentum conservation are the secret behind the working of this interesting gadget. But here comes the catch. Imagine that water is not made to gush out of the sprinkler. Instead, it is dipped in a tank and by some means, water is made to flow inside it. There can be 2 such possibilities :

• The pressure outside is increased
• The pressure inside the pipe is decreased.

The question now is ... if water flows as shown in the figure, which way would the sprinkler rotate ? ( Aniclockwise or clockwise ? )

Plz don't post you answers here, email them to twishmay@gmail.com with a satisfactory explanation.

~ Twish ~

...Tidbits...

BIO - FACTS

1. A woodpecker can peck twenty times a second
2. If you go back 25 generations, there are 33,554,432 people in your direct line of descent (parents, parents of parents, etc.)
3. The total length of all the DNA strands n our body if laid along would cover 200 trips from the moon to earth!
4. The total number of possible combinations of human DNA is 10 3,480,000,000 (a 1 followed by more than 3 billion zeros). Does this mean that if so many animals were born already, nature would start making clones, left with no more combinations possible ?
5. Our body has 10 thousand-trillion cells. Not only this, it 100 thousand-trillion bacteria at any average point of time!
6. The simplest yeast cell is 5 microns across and has more parts than a Boeing 777.
7. A chameleon's tongue is twice the length of its body.
8. Lightning strikes about 6,000 times per minute on this planet!
9. A cow gives nearly 200,000 glasses of milk in her lifetime.

~ TS ~

PS: Bio for a change ;-)

Ever Expanding Universe

One fine day, Edwin Hubble noticed a red-shift in the radiations coming from different galaxies. Doppler's Effect made him conclude that other galaxies were moving away from us! The universe was expanding! This was a breathtaking discovery in those times. This has resulted into the creation of various theories on how the universe began.

The discovery of the expanding universe soon abolished the ideas of the steady-universe people previously believed in. Physicists started making models of how the universe might behave. One such person was Alexander Friedmann. He predicted that according to the mass of the universe (which would determine the gravitational attraction) and the rate of expansion, the universe could follow one of the following three models:

One of the models predicts that our universe starts with a Big Bang and keeps expanding. In another model, the universe starts of likely, but the expansion converges towards a finite size. Although the universe tends to that size, it never attains it. In the third model the universe starts contracting after a critical time and ends up at a singularity similar to the Big Bang called the Big Crunch.

Which of the models our real universe follows has been a debatable issue. It would depend on the current rate of expansion as well as the mass-density of our universe.
The density of our universe was estimated. The next thing was to measure the rate at which the expansion was decreasing. But then, the discovery which resulted startled the scientific community! The universe was expanding, nevertheless, instead of decreasing; the rate of expansion was increasing!

To appreciate the mysterious nature of this discovery, we must realize that the force acting at such cosmic level is gravity. Now mass is always positive and hence gravity is always attractive. Then what was this force which made our universe expand? All ready to decide which Friedmann model to take up, we get an all new picture in which some mysterious force favors the expansion! It makes the galaxies accelerate away from each other at an ever increasing rate!

It is herein that the concept of Dark Energy comes it. It is hypothesized that there is another kind of mass (or energy) which has not yet been detected for some reason, which is in a sense negative! For it makes gravity repulsive! A calculation to estimate how much of such energy would be needed for the present rate of expansion showed that 70% of the mass of the universe was this Dark Energy!

Another explanation for this weird expansion is in terms of the cosmological constant. This term follows an interesting history of its own. It was originally in Einstein’s equations for Gravity, to account for the steady universe which was then observed. It made gravity act as a repulsive force for very large distances. When an expanding universe was discovered, Einstein called this ‘the biggest mistake of his life’. However this constant was reintroduced when the rate of expansion was found to be increasing.

Today the Dark Energy explanation is largely accepted by the scientific community. They are just waiting patiently for someone to announce the discovery of this strange form of matter/energy. For more info on Dark Energy, keep reading REALITY QUANTIZED.

~ Twish ~

Hot New Science

This blog is dedicated to the very latest developments in various fields in modern science and technology. The spectrum of topics dealt here range from the modern creation theories, through the various interesting laws, to the very interesting but baffling topics of relativity and quantum mechanics. An effort would be made to keep up with the latest developments while relating to the old theories.

Stay Tuned for Facts, often stranger than any Fiction you would be aware of !!!

~ TS ~