Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, January 12, 1995 TAG: 9501200001
SECTION: EXTRA PAGE: 1 EDITION: METRO
SOURCE: JOEL ACHENBACH
DATELINE: LENGTH: Long
A: This is like when you balance your checkbook and find a $3.22 discrepancy between your own records and your bank statement. Only in this case it is the entire universe that is out of whack. Neither situation is anything to panic about, but both are highly annoying.
What happened was that a couple of months ago scientists came up with a new estimate of the age of the universe: 8.1 billion years, roughly. That's young! Astrophysicists who specialize in stars were stunned. For decades they've been staring at the heavens, measuring brightness, estimating chemical composition, etc., and have concluded that the oldest stars have been around at least 10 billion years, maybe 15 or 16 billion years.
This is confounding. You have two separate observations, one of stars, one of the larger universe, and they are in conflict.
``The situation is confused,'' says Alan Guth, professor of physics at M.I.T. ``I am perplexed.''
The stars can't be older than the universe, because they were created as the universe expanded and cooled. Originally the universe was just a hot wad of energy. Matter formed later. At least that's the Big Bang theory, which hardly anyone is ready to abandon.
Are these scientific estimates just wrong? Maybe. But Guth admits that the recent observation ``does seem to be a rather reliable measurement.''
The key to figuring out the age of the universe is the Hubble Constant. This is the number that you plug into an equation to describe the rate at which galaxies are flying away from one another. We don't know exactly what the Hubble Constant is, but the new measurements, using the Hubble Space Telescope (this guy Hubble is everywhere!), puts the Hubble Constant at 80, plus or minus 17. Some scientists are hoping that maybe the margin of error is even greater than estimated, that the whole thing can just be fudged.
There's another, kind of tricky way to solve the problem: Use the Cosmological Constant. This is a number that describes the effect on the cosmos of energy that smoothly permeates space. Albert Einstein dreamed it up. He later called the Cosmological Constant his biggest blunder.
He invented it out of necessity. Early in the century everyone assumed the universe was static, the galaxies just sitting there, rather than flying apart. Einstein knew that, in a static universe, all the galaxies and stars would be inclined to collapse back together. So his Cosmological Constant was a repulsive force that kept everything separated.
Scientists kept the Constant in their equations, usually giving it a value of zero. But maybe it's not zero! Guth says that if the Constant is a positive non-zero number it can alter the equations on the age of the universe, and make an 8-billion-year-old universe suddenly twice as old.
A cheesy way out? Cooking the books? Perhaps. But then again, maybe the real point is that that guy Einstein was right about everything-- even his mistakes were acts of genius.
Q: A revisited question: Why doesn't the sun burn itself out faster? A: You survive this column, you get the astrophysics merit badge.
Naturally you recall that the Why column once explained that the sun isn't on fire. That's why it doesn't just go WOOF! and explode. The energy that warms us comes from thermonuclear fusion, the same thing that happens in hydrogen bombs, and it's an extremely efficient way of turning matter into energy. A little hydrogen gets you lots of heat; the sun can keep ``burning'' for billions of years at this rate.
But Sheldon Glashowe, a Harvard physicist and winner of the Nobel Prize, pointed out something we didn't know. The process of fusion takes place due to what is called the ``weak force.'' It's one of the four fundamental forces in the universe (along with the strong force, gravity and electromagnetism).
The weak force converts a proton to a neutron. Fusion occurs when a proton and neutron collide. The problem is, the weak force is weak. That's why they call it the weak force! Physics is simple after all. The weak force is not very efficient at turning protons to neutrons. It struggles. It labors. And so there aren't many neutrons inside the sun.
And thus the average proton, says Glashowe, spends a billion years bouncing around inside the sun before its number finally comes up and it fuses with another particle.
That's why the sun is going to be around a long time. Those protons rarely get a chance to get ``burned up,'' so to speak. They just slosh around for eons. At the rate things are going, the sun will last another five billion years. Then the hydrogen runs out. The sun turns to its helium supply; about a quarter of the sun is made of that larger element. It ``burns'' hotter.
``That's an explosive development. That's bad news,'' says Glashowe. The sun will collapse and then explode a few times and then finally, lacking the gravitational strength to stay compact, it will swell up into a huge, poofy ball of gas. ``The sun becomes a red giant. It grows to become very big, perhaps big enough to engulf the Earth, and that ain't fun.''
That's a long time away, but you know what? It's still scary. The Earth will die. Nothing we can do about it. Kind of sad, frankly. It's been a good planet, maybe the best.
by CNB