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February 2013 Archives

The End of the Universe

Fire and Ice

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.

-Robert Frost

Today's two primary theories of physics both hold predictions for the end of the universe. Surprisingly, the possibilities they describe are very different.

General Relativity: The World Ends in Ice

At the time he published it in 1916, Einstein's theory of general relativity contained an odd term called the cosmological constant. This parameter was specifically put in place by Einstein so that his theory describing gravity could allow for a universe that is stationary. This was important to him; there was no evidence to the contrary at that time and it appealed to his powerful intuition. Without a cosmological constant with a certain numerical value, the theory would predict that our universe is continually and forever expanding. 

In 1929, Edwin Hubble discovered that the universe itself indeed is expanding. Peering through the world's largest telescope, everything he saw appeared red-shifted, and the further away the thing was, the more redshifted it was too. (Redshift is to light waves what the sound of a truck horn receding away from you is to sound waves: a drop in frequency as an object moves away. This is referred to as the Doppler effect.) This could only be explained by the spacetime fabric of the universe stretching and pulling everything within it further apart. 

At this point Einstein removed the cosmological constant from his theory, calling it his "biggest blunder." Interest in the idea persisted for decades however, and in 1998 it was actually observed that the cosmological constant does exist, though its value is incredibly small-- almost zero, but slightly greater than zero.

Including this tiny value and what we know about the cosmos, general relativity predicts just what Einstein did not want: a universe that will expand forever, gradually growing thinner and thinner, colder and colder. Stars will burn out, galaxies will spin apart, matter will become less and less dense until, in many billion years, everything is at nearly absolute zero. Death by ice.

The Standard Model: The World Ends in Fire

Preliminary results announced this week give a different possibility for the end of the universe as we know it. The mass of the Higgs boson, discovered at the LHC last summer, have been plugged into the Standard Model to calculate something called vacuum instability. This is an esoteric possibility of quantum mechanics, where space might actually not be a true vacuum. Eventually, some part of the universe would quantum mechanically jump (or be pushed by tremendous energy) into the true vacuum state, and the entire rest of the universe would be sucked in too. The universe would "explode" into the new state at the speed of light, destroying everything that currently exists in an enormous runaway flash.

This theory is still being investigated, and no one is sure how realistic this possibility is. (It's probably theoretically possible, but extraordinarily unlikely.) 

Personally, I'd prefer to have billions of years to prepare for the ice. A chance explosion would confirm my fears-- before death no time to make nice.

(Photo: Universe via Wikimedia Commons)
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February 2013 Archives

Three Plus One Geometries of the Universe

Back in 8th grade, I hated math. Everyone hated math. Maybe the kid who kept their calculator (or slide rule, for you vintage readers) in a case didn't hate math. That kid probably became an engineer. Or a physicist. (Confession: I was later the kid with the fancy calculator.) Our rallying cry as math-haters was, "When are we ever going to use this?!" Here's a wise answer: two basic forms of geometry, learned before high school, are used in almost every engineering project and every physics discovery that has ever been made.

Euclidean Geometry

Greek mathematicians, notably Euclid and Pythagoras (of middle school algebra infamy), laid out the first geometry of the world. They thought of things in terms of shapes made of lines and curves. Their most important discovery was a way to tell how far apart things are:

Take any two places (A and B) and draw a line through each place such that the lines meet (C) at a 90 degree angle. The distance from A to B, squared, is always equal to the distance B-C squared plus the distance from C back to A, squared. (This is the infamous Pythagorean theorem.) This language is perfectly accurate for flat, still surfaces. Notice however, that it only deals in distances between things, not their absolute position. Euclid says "B is five miles north of A" not "B is at 2 Water Lane, Woolsthorpe".

Cartesian Geometry

Descartes wanted a way to make the points A, B and C refer to absolute things so that anyone anywhere can perform the same measurements. Latin, Chinese, Hebrew and English are all languages of words to catalog or refer to concepts. They are phone books that assign words to ideas. Similarly, the math of Descartes is a phone book, but to assign numbers to places in space. This is called Cartesian geometry. In this language, the Pythagorean Theorem is written like this:

Pythagoras Descartes.pngWhere A, B and C are all coordinate numbers, like (0,0) or (-3,5) that you stick into the formula. Euclid would have made you draw lines and geometric shapes and connect them all with theorems!

Descartes's world is an enormous ream of numbered graph paper. You start with zero somewhere, and then you follow perpendicular lines in all directions. Euclid's relative distances are replaced by numbers that tell you where you start and where you end and where you are everywhere in between, relative to the entire world. This mathematical machinery is valid for most experiences in day to day life.

Lorentzian Geometry:

Centuries later, Einstein came along and changed everything. His conclusion that the speed of light is constant, and his fitting of experiments to theory demanded a new geometry. In this geometry, objects always move at the speed of light through four-dimensional space-time. The math was invented by Hendrik Lorentz, a brilliant mathematician and physicist of the late 19th century. Lorentzian geometry is much harder to explain, but you can think of the graph paper of Descartes as actually distorted, or squished, like a cardboard carton being smashed:

Lorentz Transformed Coords.gif

Cartesian geometry is the black perpendicular lines; Lorentz geometry is the green and red lines. (Source: IEP)

Second, distance rules change a bit, so you have to modify the Pythagorean theorem:

Pythagoras Lorentz.png

Where x,y,z,t are the distances you've moved in space (x,y,z) and time (t) and c is the speed of light.

Curved spacetime geometry:

After Einstein revolutionized the geometry by which we measure the universe in 1905, he did it again in 1916, when he completed the theory of general relativity. General relativity is so difficult and so complex, that we only know of a few correct answers to its equations. Luckily, however, Einstein realized that the curved universe looks flat if you look at a small enough area of it. This is just like how the earth appears flat to us, standing upon it. Physicists thus work in Lorentz geometry most of the time, and then use the difficult curved geometry to translate between one almost flat "Lorentzian" place and another.

Four increasingly sophisticated geometrical descriptions of the universe, as created by three millennia of human minds. How much deeper will the rabbit hole go?


Note: phone book analogy borrowed from "The Phone Book": Misner Thorne & Wheeler's Gravitation, a book on general relativity with the authority and heft of a phone book but far greater beauty.

February 2013 Archives

Space Sex and Space Porn

What is it like to have sex in space? Nobody knows. (Well, unless NASA has been conducting juicy secret experiments that they haven't told us about. We'll get to that.) 

Venturing further into the great unknown has fascinated many of us, including Apollo 11 astronaut Michael Collins, famous science fiction authors like Isaac Asimov and Arthur C. Clarke, astronomers and even NASA consultants. In trying to cross the final frontier, we are still frustrated--but some good news for space sex dreamers sprang up this week.

British celebrity rag The Sun is reporting that next year, the first porn star will blast off into space. She will be riding a private rocket, paying her own $100,000 dollar ticket to low earth orbit and completing her own training for the mission. Will the world finally find out about space sex? According to CoCo Brown, star of Big Booty Bomb 2, the answer is no. But wait, there is still hope, according to the article: "Maybe I'll pop my boob out and take a photo of it with the Earth in the background." The first space porn! 

Although no porn has been made in space, erotic film has actually been produced in a weightless environment. As part of what must certainly be a four-star cinema epic, The Uranus Experiment Part II, a sex scene was filmed in a zero-g training aircraft. These airplanes carry humans up to a high altitude, then go down hard. The pilots power-dive, pointing the nose down and accelerating the engines towards the ground at 9.8 m/s/s, the exact pull rate of gravity. The walls of the craft are streaking toward earth at the same rate as the people inside are falling, so they experience apparent weightlessness. Obviously, the plane will crash very quickly if it is not pulled out of the descent, so a zero-g session is limited to about 20 seconds. Apparently the budget only allowed one(!) dive, so the rest of the zero-g sex is tragically fake.

NASA may have licked Coco, Uranus, and everyone else in this particular space race though. In 1992 space shuttle mission STS-47 flew into space with a married couple aboard. Mark Lee and Jan Davis had been married in secret just before the mission, and after they came out there was no time to substitute crew members. (Or so they want you to think.) NASA has since banned couples from flying missions together.

Reproduction in space has actually been studied, though not in humans. Rats and mice have been conceived in space. Fertilization took place successfully in near-zero-g conditions. However, the embryos were then grown in culture and implanted in donor mother rats. Results showed that the birth rate for these space-fertilized embryos was lower than earth-conceived embryos. Gravity also effects gene expression. You might be born with slightly different characteristics in space than on Earth.

The long and short of it: no space sex yet. However we may get to see the first space porn soon. One small step toward a giant leap for mankind!