Cosmology Curiosity

UC Berkeley's 'Physics for Future Presidents'

The video above is the first of 26 in a series of lectures on physics.

Prof. Richard A. Muller of the University of California, Berkeley is the lecturer. Prof. Muller is quite an effective and interesting lecturer. The series is described by UC Berkeley as:

"Physics 10: Physics for Future Presidents. Spring 2006. Professor Richard A. Muller. The most interesting and important topics in physics, stressing conceptual understanding rather than math, with applications to current events. Topics covered may vary and may include energy and conservation, radioactivity, nuclear physics, the Theory of Relativity, lasers, explosions, earthquakes, superconductors, and quantum physics."

All of the 26 video lectures can be seen from here, here, and here.

If you'd like to give physics a second chance, the lecture series is a good place to start.

Technorati Tags: lectures, physics, Richard Muller, UC Berkeley, video, webcast, Youtube

How fast are you moving when you are sitting still?

Unimaginably and incomprehensively fast would be the answer.

We've actually touched on this subject before.

This other article by Andrew Fraknoi gives other insights, however. Click here to see the whole story.

An excerpt: "And how fast is the Milky Way Galaxy moving? The speed turns out to be an astounding 1.3 million miles per hour (2.1 million km/hr)! We are moving roughly in the direction on the sky that is defined by the constellations of Leo and Virgo. Although the reasons for this motion are not fully understood, astronomers believe that there is a huge concentration of matter in this direction. Some people call it The Great Attractor, although we now know that the pull is probably not due to one group of galaxies but many. Still the extra gravity in this direction pulls the Milky Way (and many neighbor galaxies) in that direction."

The image above is the Leo Triplet in the constellation Leo. So the next time you look up the night sky, look for the constellations Leo and Virgo. Apparently that's where we are heading.

[Image by Anttler, per GNU Free Documentation/ Free Software Foundation.]

Related post: Earth's speed around the universe
Related post: CMBR Dipole: Speeding Through the Universe

Andrew Fraknoi, astronomy, cosmology, Leo, speed around the universe, speed of light, Virgo

The Arrow of Time

‘Time is but the stream I go a-fishing in.’ said Henry David Thoreau.

What is the arrow of time?

Here's the current thinking of the scientific establishment on the subject, from Cosmic Variance:

The [arrow of time says that the] past is different from the future. One of the most obvious features of the macroscopic world is irreversibility: heat doesn’t flow spontaneously from cold objects to hot ones, we can turn eggs into omelets but not omelets into eggs, ice cubes melt in warm water but glasses of water don’t spontaneously give rise to ice cubes. These irreversibilities are summarized by the Second Law of Thermodynamics: the entropy of a closed system will (practically) never decrease into the future.

But entropy decreases all the time; we can freeze water to make ice cubes, after all.

Not all systems are closed. The Second Law doesn’t forbid decreases in entropy in open systems, nor is it in any way incompatible with evolution or complexity or any such thing.

So what’s the big deal?

In contrast to the macroscopic universe, the microscopic laws of physics that purportedly underlie its behavior are perfectly reversible. (More rigorously, for every allowed process there exists a time-reversed process that is also allowed, obtained by switching parity and exchanging particles for antiparticles — the CPT Theorem.) The puzzle is to reconcile microscopic reversibility with macroscopic irreversibility.

And how do we reconcile them?

The observed macroscopic irreversibility is not a consequence of the fundamental laws of physics, it’s a consequence of the particular configuration in which the universe finds itself. In particular, the unusual low-entropy conditions in the very early universe, near the Big Bang. Understanding the arrow of time is a matter of understanding the origin of the universe.

Wasn’t this all figured out over a century ago?

Not exactly. In the late 19th century, Boltzmann and Gibbs figured out what entropy really is: it’s a measure of the number of individual microscopic states that are macroscopically indistinguishable. An omelet is higher entropy than an egg because there are more ways to re-arrange its atoms while keeping it indisputably an omelet, than there are for the egg. That provides half of the explanation for the Second Law: entropy tends to increase because there are more ways to be high entropy than low entropy. The other half of the question still remains: why was the entropy ever low in the first place?

Is the origin of the Second Law really cosmological? We never talked about the early universe back when I took thermodynamics.

Trust me, it is. Of course you don’t need to appeal to cosmology to use the Second Law, or even to “derive” it under some reasonable-sounding assumptions. However, those reasonable-sounding assumptions are typically not true of the real world. Using only time-symmetric laws of physics, you can’t derive time-asymmetric macroscopic behavior (as pointed out in the “reversibility objections” of Lohschmidt and Zermelo back in the time of Boltzmann and Gibbs); every trajectory is precisely as likely as its time-reverse, so there can’t be any overall preference for one direction of time over the other. The usual “derivations” of the second law, if taken at face value, could equally well be used to predict that the entropy must be higher in the past — an inevitable answer, if one has recourse only to reversible dynamics. But the entropy was lower in the past, and to understand that empirical feature of the universe we have to think about cosmology.

Does inflation explain the low entropy of the early universe?

Not by itself, no. To get inflation to start requires even lower-entropy initial conditions than those implied by the conventional Big Bang model. Inflation just makes the problem harder.

Does that mean that inflation is wrong?

Not necessarily. Inflation is an attractive mechanism for generating primordial cosmological perturbations, and provides a way to dynamically create a huge number of particles from a small region of space. The question is simply, why did inflation ever start? Rather than removing the need for a sensible theory of initial conditions, inflation makes the need even more urgent.

The rest of the article can be seen here.

[Image by Andreas Tille, per GNU Free Documentation/ Free Software Foundation.]

arrow of time, Cosmic Variance, cosmology, physics, quantum mechanics

Stephen Hawking quotes

The idea of the Hawking image plus the quotes came from here.

Here's another set of quotes from the cosmologist Stephen Hawking, from BrainyQuote:

"Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?"

"God not only plays dice, He also sometimes throws the dice where they cannot be seen."

"I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image."

"If we do discover a complete theory, it should be in time understandable in broad principle by everyone. Then we shall all, philosophers, scientists, and just ordinary people be able to take part in the discussion of why we and the universe exist."

"It is no good getting furious if you get stuck. What I do is keep thinking about the problem but work on something else. Sometimes it is years before I see the way forward. In the case of information loss and black holes, it was 29 years."

"It is not clear that intelligence has any long-term survival value."

"My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all."

"Someone told me that each equation I included in the book would halve the sales."

"The usual approach of science of constructing a mathematical model cannot answer the questions of why there should be a universe for the model to describe. Why does the universe go to all the bother of existing?"

Earlier this year, Hawking said that "with luck" the team of scientists he is working with might be able to answer "some of the ultimate questions".

[Image: Brickshelf]

cosmology, Hawking, Lego, physics, quotations, quotes, Stephen Hawking

[Off-topic] Turn One Computer Into Two, Free

If you have a PC running on Linux, this software from Userful turns the computer into two.

The software, Desktop Multiplier, allows a single computer box to support multiple users (up to 10) at the same time. All you need to do is connect an extra monitor, USB keyboard and mouse to your computer box. See diagram.

From an article regarding Desktop Multiplier: "How much it slows down your computer depends largely on how fast your computer is and what you plan on using the computer for," said [Sean] Rousseau [Userful's marketing manager]. "For an example of what you can do we recently tried overloading one of our 10 user stations just to see if we could. All 10 had office programs and email open, they each had multiple YouTube videos playing, and six of them were playing RuneScape all at the same time without any slowdowns at all."

The current promotion comes with free two-user licences, so all you need is an extra video card (or a card that enables two monitors to be plugged in), a USB keyboard and a mouse.

You can download the software from here.

[Image: Userful]

Desktop Multiplier, freeware, linux, PC, software, Userful

'Cosmology Quest' -- Plasma cosmology video

Universe: The Cosmology Quest is the definitive video for those interested in plasma cosmology.

Plasma cosmology says that electromagnetism rather than gravitation explains better the observations in astronomy. Plasma cosmology disputes the big bang theory. It advocates instead a variant of the steady state theory (i.e., eternal universe).

Part 1:

Part 2:

Part 3:

Part 4:

[Image: Cosmology Curiosity]

Related post: Plasma cosmology

cosmology

If you go too fast do you become a black hole?

The question is, if you go too fast do you become a black hole?

Here's the anwser, from an article that's better quoted in full --

According to relativity the following are true facts:

• As an object approaches the speed of light, its kinetic energy increases without limit.
• Energy is related to mass by the formula E=mc2.
• As an object approaches the speed of light, its length contracts towards zero.
• If enough mass is squeezed into a sufficiently small space it will form a black hole

Put these facts together and it looks like we should be able to conclude that an object which moves at a speed sufficiently close to the speed of light should collapse to form a black hole. We could even argue that if you move fast enough relative to a star then that star must appear as a black hole to you because of its increased energy as observed by you. This would be paradoxical since we would expect things to appear very differently to an observer who is stationary relative to the star. So what has gone wrong?

In fact objects do not have any increased tendency to form black holes due to their extra energy of motion. In a frame of reference stationary with respect to the object, it has only rest mass energy and will not form a black hole unless its rest mass is sufficient. If it is not a black hole in one reference frame, then it cannot be a black hole in any other reference frame.

In part the misunderstanding arises because of the use of the concept of relativistic mass in the equation E=mc2. Relativistic mass, which increases with the velocity and kinetic energy of an object, cannot be blindly substituted into formulae such as the one that gives the radius for a black hole in terms of its mass. One way to avoid this is to not speak about relativistic mass and think only in terms of invariant rest mass (see Relativity FAQ Does mass change with speed?).

The statement that "If enough mass is squeezed into a sufficiently small space it will form a black hole" is rather vague. Crudely speaking we would say that if an amount of mass, M is contained within a sphere of radius 2GM/c2 (the Schwarzschild radius) then it must be a black hole. But this is based on a particular static solution to the Einstein field equations of general relativity, and ignores momentum and angular momentum as well as the dynamics of space-time itself. In general relativity, gravity does not simply couple to mass as it does in the Newtonian theory of gravity. It also couples to momentum and momentum flow; the gravitational field is even coupled to itself. It is actually quite difficult to define the correct conditions for a black hole to form. Hawking and Penrose proved a number of useful singularities theorems about the formation of black holes, and from astrophysics we know that the theorems should apply to sufficiently massive stars when they reach the end of their life and collapse into a small volume.

[Image by Ute Kraus, per Creative Commons Attribution ShareAlike 2.0 Germany.]

black hole, cosmology, E=mc2, Einstein, field equations, invariant mass, relativistic mass, relativity, Schwarzschild radius

Black hole misconception

Nope, a black hole is not a cosmic vacuum cleaner.

Wikipedia explains, in a list of common misconceptions:

"The gravity of a black hole is slightly weaker than, not stronger than, the gravity of the star which formed it (at distances greater than the star's radius). Isaac Newton's laws of gravitation state that, for an object with a spherically symmetric distribution of mass, two things affect how much gravitational force is felt by an observer: the mass of the object and the distance between the observer and the object's center of mass. A black hole has slightly less mass than the star which formed it, because when a star becomes a supernova, some of the star's mass is converted into energy according to Einstein's equation E = mc², and a great deal of the star's mass is returned to the interstellar medium. Only when a distance of (slightly less than) the star's original radius is passed does the force of gravity become greater. The event horizon is usually much smaller than the original star's radius. As such, black holes are not similar to "cosmic vacuum cleaners". Objects can settle into stable orbits around them just as they would around any other mass in space, including stars."

The entire list of common misconceptions on various subjects can be found here.

[Image: Wikimedia Commons]

black hole, cosmology, relativity

Biggest black hole in the cosmos discovered

The biggest black hole in the cosmos was recently discovered.

[The caption of the above image: The quasar OJ287 contains two black holes (this slightly dated illustration lists the larger black hole's mass as 17 billion Suns, though researchers now estimate it is 18 billion Suns). The smaller black hole crashes through a disc of material around the larger one twice every orbit, creating bright outbursts.]

New Scientist reports:

"The most massive known black hole in the universe has been discovered, weighing in with the mass of 18 billion Suns. Observing the orbit of a smaller black hole around this monster has allowed astronomers to test Einstein's theory of general relativity with stronger gravitational fields than ever before.

"The black hole is about six times as massive as the previous record holder and in fact weighs as much as a small galaxy. It lurks 3.5 billion light years away, and forms the heart of a quasar called OJ287. A quasar is an extremely bright object in which matter spiralling into a giant black hole emits copious amounts of radiation.

"But rather than hosting just a single colossal black hole, the quasar appears to harbour two – a setup that has allowed astronomers to accurately 'weigh' the larger one.

"The smaller black hole, which weighs about 100 million Suns, orbits the larger one on an oval-shaped path every 12 years. It comes close enough to punch through the disc of matter surrounding the larger black hole twice each orbit, causing a pair of outbursts that make OJ287 suddenly brighten.

"General relativity predicts that the smaller hole's orbit itself should rotate, or precess, over time, so that the point at which it comes nearest its neighbour moves around in space – an effect seen in Mercury's orbit around the Sun, albeit on a smaller scale."

Click here to view the rest of the story.

[Image: VISPA]

black hole, cosmology, Einstein, OJ287, quasar, relativity

[Off-topic] Free classical music: Musopen, etc.

Download free public domain music over at Musopen.

Musopen music are mostly classical music. They were "recorded by individuals and college/community orchestras throughout the United States and stored online so it can be accessed for free through [the] website. Musopen is copyright free classical music."

Other sources of free music include: Wikipedia, the Columbia University, Accuclassical, Classical Archives, Magnatune podcasts, and Amazon.com.

[Image: Wikipedia]

Accuclassical, Amazon, Classical Archives, Columbia University, free music, Musopen