Cosmology Curiosity

'Escaping' from the universe

What should be the expansion speed of the universe for it to overcome its own inward gravitational pull?

Continuing on from Paul Davies' The Last Three Minutes (1994):

"... the escape velocity will be about the velocity of light. This is a very significant result, because the most distant galaxies appear to be receding from us at close to the speed of light. Taken at face value, the galaxies seem to be flying apart so fast that they may indeed just 'escape' from the universe, or at least from one another, and 'never to come down.'

"In fact, it turns out that the expanding universe behaves in a manner closely analogous to a body projected from Earth, even if there is no well-defined edge. If the rate of expansion is fast enough, the retreating galaxies will escape from the cumulative gravity of all the other material in the universe, and the expansion will continue forever. On the other hand, if the rate is too slow, the expansion will eventually be brought to a halt and the universe will start to contract. The galaxies will then 'come down' again, and the ultimate cosmic catastrophe will ensue, as the universe collapses."

The Big Rip or the Big Crunch?

Well for now, it looks like it's the former; observations point to an ever accelerating expansion of the cosmos.

[Image credit: NASA]

Related post: Escape velocities

Technorati Tags: Big Chill, Big Crunch, Big Rip, cosmology, Hubble constant, universe expansion

Escape velocities

Escape velocity is the speed at which one can overcome the pull of gravity.

Here's a sampling, from Paul Davies' The Last Three Minutes (1994):

(a) 11 km/sec to leave Earth;

(b) 618 km/sec to escape from our solar system;

(c) a few hundred km per second to leave the Milky Way;

(d) tens of thousands km per second to leave a neutron star; and

(e) the speed of light [300,000 km/sec] to escape from a black hole.

Escape velocity is a function of the mass and radius of the body one is trying to escape from. The more compact the body (e.g., neutron star), the higher the required escape velocity.

[Image credit: NASA]

Related post: 'Escaping' from the universe

Technorati Tags: cosmology, escape velocity, gravitation, Hubble's constant, universe expansion

Dark matter finally found?

The proof is said to be "groundbreaking".

To back track a little, it is believed that the universe comprises of --

(a) 75% dark energy (the repulsive force of 'empty' space that's making the galaxies fly apart faster and faster);

(b) 20% dark matter (the non-visible matter that must be out there, given the stronger-than-expected gravitation holding the galaxies); and

(c) 5% ordinary matter (the stars, planets, galactic dust, and you & me).

It's an embarrassment actually. Man thinks that he finally figured out how the universe ticks and from whence it came, and yet all that he knows about is a mere 5% of it.

Now the first direct proof of dark matter's existence was just announced.

Cosmic Variance's commentary is most elucidating, as usual.

BBC, New Scientist, and Scientific American have articles on dark matter's newly found proof as well.

The Chandra site has an animation of how the image above may have arisen.

Admittedly, more research still needs to be done. Hence, it is too early to tell whether the proof is as conclusive as what the researchers say it is.

[Image credit: NASA]

Technorati Tags: Bullet Cluster, Chandra, dark energy, dark matter, Einstein, gravitation, Newton

Why Newton thought the universe was infinite

Isaac Newton [1643-1727] had to see it that way for his gravitation law to stand.

Newton's thinking was as follows [from Universe by Design (2004), by Dr. Danny Faulkner]:

(a) all matter exert mutual attraction upon each other;

(b) if the universe is finite, then there must be a center of mass;

(c) that center must be the point where all matter will gravitate to;

(d) if the universe was eternal, there should have been ample time for the mass to have amalgamated at the center of gravity; and

(e) since that has not happened and since the universe is eternal, then the cosmos must be infinite.

Faulkner sums it up: "He [Newton] reasoned that if the universe extended indefinitely in all directions, then there would be no center of mass. All matter would be equally attracted in all directions, so that there would be no collapse of all matter into a single heap. The eternality and infinite size of the universe persisted for two centuries."

[Image: Wikipedia]

Related post: Is there an edge to the cosmos?
Related post: Olbers' paradox of the dark night sky

Technorati Tags: astronomy, cosmology, Isaac Newton, Newton, Olbers' paradox

John von Neumann's lesser known side

"Von Neumann [1903–1957] entertained notions which would now trouble many. He dreamed of manipulating the environment by, for example, spreading artificial colorants on the polar ice caps [to] raise global temperatures. He also favored a preventive nuclear attack on the USSR ....

"[He] committed himself to a very large number of military consultancies, primarily for the Navy [he preferred socializing with admirals because they enjoy drinking liquor; generals prefer coffee].

"One noted result in the field of explosions was the discovery that bombs of large dimension are more devastating if they detonate before touching the soil because of the additional force caused by waves of detonation (the media maintained more simply that von Neumann had discovered that it is better to miss a target than to hit it). The most famous (or infamous) application of this discovery occurred on the 6th and 9th of August 1945 ... at the precise altitude calculated by von Neumann himself .... Von Neumann's first choice, the city of Kyoto, was dismissed out of hand by the Secretary of War Henry Stimson.

"After the war, Robert Oppenheimer had famously remarked that the physicists had 'known sin' as a result of their development of the first atomic bombs. Von Neumann's rather cynical reply was that 'sometimes someone confesses a sin in order to take credit for it'."

The Hungarian polymath made significant contributions to quantum physics, functional analysis, set theory, economics, computer science, numerical analysis, hydrodynamics [of explosions], statistics, etc.

[Image: Wikipedia. It is believed that the use of postage stamps to illustrate the stamp in question qualifies as fair use under United States copyright law.]

Related post: John von Neumann

Technorati Tags: Henry Stimson, Hiroshima, John von Neumann, Nagasaki, polymath, quantum physics

World happiness map [off topic]

Adrian White of the University of Leicester recently published the first ever World Map of Happiness.

US ranks 23rd out of the 178 countries surveyed.

Health, wealth, and education in that order were found to be the main factors affecting happiness.

The top 10 ranked are:

1. Denmark
2. Switzerland
3. Austria
4. Iceland
5. The Bahamas
6. Finland
7. Sweden
8. Bhutan
9. Brunei
10. Canada

The three least happy are:

176. Democratic Republic of the Congo
177. Zimbabwe
178. Burundi

[Image credit: Adrian White, Analytic Social Psychologist, University of Leicester]

Related post: World cultures study: the Inglehart Values Map

Technorati Tags: Adrian White, country rank, happiness index, Inglehart map, University of Leicester, World Happiness Map

The unraveling of string theory?

Michael Lemonick in a TIME article reports that more and more are getting critical of the string theory:

" ... next month two books will be hitting the shelves to make the point in greater detail. Not Even Wrong, by Columbia University mathematician Peter Woit, and The Trouble with Physics, by Lee Smolin at the Perimeter Institute for Theoretical Physics in Waterloo, Ont., both argue that string theory (or superstring theory, as it is also known) is largely a fad propped up by practitioners who tend to be arrogantly dismissive of anyone who dare suggest that the emperor has no clothes."

The article elaborates:

"That lack of specificity hasn't slowed down the string folks. Maybe, they've argued, there really are an infinite number of universes -- an idea that's currently in vogue among some astronomers as well -- and some version of the theory describes each of them. That means any prediction, however outlandish, has a chance of being valid for at least one universe, and no prediction, however sensible, might be valid for all of them.

"That sort of reasoning drives critics up the wall. It was bad enough, they say, when string theorists treated nonbelievers as though they were a little slow-witted. Now, it seems, at least some superstring advocates are ready to abandon the essential definition of science itself on the basis that string theory is too important to be hampered by old-fashioned notions of experimental proof."

Here's Woit's blog entry on the above article by Lemonick.

Related post: String theory's woes
Related post: String theory cosmology

Technorati Tags: Brian Greene, cosmology, Lee Smolin, Michael Lemonick, Peter Woit, string theory, superstrings, theory of everything

New Scientist's Top 10 Weirdest Cosmology Theories

From Stephen Battersby, in NewScientistSpace, the Top 10: Weirdest cosmology theories:

1. Clashing branes

2. Evolving universes

3. Superfluid space-time

4. Goldilocks universe

5. Gravity reaches out

6. Cosmic ghost

7. It's a small universe

8. Fast light

9. Sterile neutrinos

10. In the Matrix

The runner-up: 'Good bye, Mr. Anderson'. And the winner is, Slippin' and slidin'.

[Image: Wikipedia. It is believed that the use of scaled-down, low-resolution images of movie posters to illustrate the movie in question, etc. qualifies as fair use under United States copyright law.]

Technorati Tags: anthropic principle, branes, cosmology, New Scientist Space, Stephen Battersby, VSL

John von Neumann

The young ladies had to cover their legs with cardboard because he keeps on gazing at them.

He reads while he drives and and is a hedonist given to wanton eating and drinking.

There are few scientists whose demeanor and views are as unconventional as John von Neumann (1903-1957).

"... János [John], nicknamed 'Jancsi', was an extraordinary prodigy. At the age of six, he could divide two 8-digit numbers in his head and converse with his father in ancient Greek. At the same age, when his mother once stared aimlessly in front of him, he asked, 'What are you calculating?'... He could memorize pages on sight. It was said that he used to bring two books into the toilet with him for fear of finishing one of them before having completed his bodily functions."

When he grew up, "He was a profoundly committed hedonist who liked to eat and drink heavily (it was said that he knew how to count everything, except calories), tell dirty stories and very insensitive jokes (e.g. 'bodily violence is a displeasure done with the intention of giving pleasure'), and insistently gaze at the legs of young women (so much so that the female secretaries at Los Alamos were often compelled to cover up the exposed undersides of their desks with sheets of paper or cardboard.)"

[Image: Wikipedia]

Related post: John von Neumann's lesser known side

No black holes, just MECOs

Black holes don't exist, if Rudolph Schild and Darryl Leiter's findings will turn out to be on track.

As a massive star dies, their research says that it ends up not as a black hole but as a compact ball of plasma called MECO. MECO stands for "magnetospheric eternally collapsing object":

(a) a quasar's radiation is commonly believed to come from a giant black hole devouring its surrounding matter;

(b) now, a well accepted property of black holes is that they cannot sustain a magnetic field of their own;

(c) however, observations of quasar Q0957+561 indicate that the object powering it does have a magnetic field; and

(d) thus, Schild's team believes that rather than a black hole, this quasar contains a MECO and it would be best evidence yet for it.

The New Scientist article adds: "According to the MECO theory, objects in our universe can never actually collapse to form black holes. When an object gets very dense and hot, subatomic particles start popping in and out of existence inside it in huge numbers, producing copious amounts of radiation. Outward pressure from this radiation halts the collapse so the object remains a hot ball of plasma rather than becoming a black hole."

Rudolph Schild is from the Harvard-Smithsonian Center for Astrophysics (CfA). Darryl Leiter is from the Marwood Astrophysics Research Center.

Journal reference: The Astronomical Journal (vol 132, p 420)

Image credit: Christine Pulliam/ CfA. [Artist's impression of a MECO, i.e., the hole in the quasar's core]

Technorati Tags: astronomy, black hole, Darryl Leiter, MECO, quasar, Rudolf Schild