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The 11 Greatest Unanswered Questions of Physics
DISCOVER Vol. 23 No. 2 ^ | February 2002 | Eric Haseltine

Posted on 02/17/2002 12:35:18 PM PST by The Raven

Resolution of these profound questions could unlock the secrets of existence and deliver a new age of science within several decades

Here's a tale of modern physics: Two scientists work at the same university in different fields. One studies huge objects far from Earth. The other is fascinated by the tiny stuff right in front of him. To satisfy their curiosities, one builds the world's most powerful telescope, and the other builds the world's best microscope. As they focus their instruments on ever more distant and ever more minuscule objects, they begin to observe structures and behaviors never before seen—or imagined. They are excited but frustrated because their observations don't fit existing theories.

One day they leave their instruments for a caffeine break and happen to meet in the faculty lounge, where they begin to commiserate about what to make of their observations. Suddenly it becomes clear to both of them that although they seem to be looking at opposite ends of the universe, they are seeing the same phenomena. Like blind men groping a beast, one scientist has grasped its thrashing tail and the other its chomping snout. Comparing notes, they realize it's the same alligator.

This is precisely the situation particle physicists and astronomers find themselves in today. Physicists, using linear and circular particle accelerators as their high-resolution "microscopes," study pieces of atoms so small they can't be seen. Astronomers, using a dozen or so new supersize telescopes, also study the same tiny particles, but theirs are waiting for them in space. This strange collision of information means that the holy grail of particle physics—understanding the unification of all four forces of nature (electromagnetism, weak force, strong force, and gravity)—will be achieved in part by astronomers.

The implications are exciting to scientists because bizarre marriages of unrelated phenomena have created leaps of understanding in the past. Pythagoras, for example, set science spinning when he proved that abstract mathematics could be applied to the real world. A similar leap occurred when Newton discovered that the motions of planets and falling apples are both due to gravity. Maxwell created a new era of physics when he unified magnetism and electricity. Einstein, the greatest unifier of them all, wove together matter, energy, space, and time.

But nobody has woven together the tiny world of quantum mechanics and the big world we see when we look through a telescope. As these come together, physicists realize they are getting very close to a single "theory of everything" that accounts for the fundamental workings of nature, the long-sought unified field theory.

About two years ago, after a presentation by the National Research Council's board on physics and astronomy that showed the converging agendas of the two fields, NASA administrator Daniel Goldin suggested a special report that would detail how much astronomers and physicists could benefit from one another's insight. Recently, the council's committee on the physics of the universe released that report. It details 11 profound questions, some of which may be answered within a decade. If so, science is likely to make one of its greatest leaps in history.

But first, what we don't know.

QUESTION 1

What is dark matter?

All the ordinary matter we can find accounts for only about 4 percent of the universe. We know this by calculating how much mass would be needed to hold galaxies together and cause them to move about the way they do when they gather in large clusters. Another way to weigh the unseen matter is to look at how gravity bends the light from distant objects. Every measure tells astronomers that most of the universe is invisible.

It's tempting to say that the universe must be full of dark clouds of dust or dead stars and be done with it, but there are persuasive arguments that this is not the case. First, although there are ways to spot even the darkest forms of matter, almost every attempt to find missing clouds and stars has failed. Second, and more convincing, cosmologists can make very precise calculations of the nuclear reactions that occurred right after the Big Bang and compare the expected results with the actual composition of the universe. Those calculations show that the total amount of ordinary matter, composed of familiar protons and neutrons, is much less than the total mass of the universe. Whatever the rest is, it isn't like the stuff of which we're made.

The quest to find the missing universe is one of the key efforts that has brought cosmologists and particle physicists together. The leading dark-matter candidates are neutrinos or two other kinds of particles: neutralinos and axions, predicted by some physics theories but never detected. All three of these particles are thought to be electrically neutral, thus unable to absorb or reflect light, yet stable enough to have survived from the earliest moments after the Big Bang.

QUESTION 2

What is dark energy?

Two recent discoveries from cosmology prove that ordinary matter and dark matter are still not enough to explain the structure of the universe. There's a third component out there, and it's not matter but some form of dark energy.

The first line of evidence for this mystery component comes from measurements of the geometry of the universe. Einstein theorized that all matter alters the shape of space and time around it. Therefore, the overall shape of the universe is governed by the total mass and energy within it. Recent studies of radiation left over from the Big Bang show that the universe has the simplest shape—it's flat. That, in turn, reveals the total mass density of the universe. But after adding up all the potential sources of dark matter and ordinary matter, astronomers still come up two-thirds short.

The second line of evidence suggests that the mystery component must be energy. Observations of distant supernovas show that the rate of expansion of the universe isn't slowing as scientists had once assumed; in fact, the pace of the expansion is increasing. This cosmic acceleration is difficult to explain unless a pervasive repulsive force constantly pushes outward on the fabric of space and time.

Why dark energy produces a repulsive force field is a bit complicated. Quantum theory says virtual particles can pop into existence for the briefest of moments before returning to nothingness. That means the vacuum of space is not a true void. Rather, space is filled with low-grade energy created when virtual particles and their antimatter partners momentarily pop into and out of existence, leaving behind a very small field called vacuum energy.

That energy should produce a kind of negative pressure, or repulsion, thereby explaining why the universe's expansion is accelerating. Consider a simple analogy: If you pull back on a sealed plunger in an empty, airtight vessel, you'll create a near vacuum. At first, the plunger will offer little resistance, but the farther you pull, the greater the vacuum and the more the plunger will pull back against you. Although vacuum energy in outer space was pumped into it by the weird rules of quantum mechanics, not by someone pulling on a plunger, this example illustrates how repulsion can be created by a negative pressure. ....


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To: leadhead
The big bang clearly marks some kind of first I've always referred to it as the "Primal Fart" but then, I'm an engineer, not a physicist!

Yeah, I learned awhile ago that us engineers are just pond scum to physicists. As an Aeronautical Engineering sophomore at MIT - I interviewed for a summer job in the physics department. After a lengthy explanation as to the experiment they were working on to make helium into a superfluid, I committed the cardinal sin and asked the great professor "Well...what can you DO with it?"

51 posted on 02/17/2002 3:34:00 PM PST by ctonious
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To: Exnihilo
Maybe get your filter checked--tank cleaned!
52 posted on 02/17/2002 3:34:18 PM PST by f.Christian
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To: f.Christian
o.k.
53 posted on 02/17/2002 3:36:19 PM PST by krunkygirl
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To: stlrocket
I'm lost... You bright people leave me in the dust...
54 posted on 02/17/2002 3:43:50 PM PST by krunkygirl
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To: ChadGore
Question 12: What is that stuff between al gores ears ?

Dung.

55 posted on 02/17/2002 3:44:54 PM PST by MotleyGirl70
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To: IncPen
Um, I know the answer to number 6 but I'm not telling.

BZZZZZTTTT...

Sorry - the answer is 42

56 posted on 02/17/2002 3:45:48 PM PST by NY.SS-Bar9
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To: NY.SS-Bar9
"the answer is 42"

- replied Deep Thought, with infinite majesty and calm.

57 posted on 02/17/2002 3:48:20 PM PST by ctonious
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To: f.Christian
It looks like you're saying people who don't understand your bizarre postings are dumb. No, you're dumb. You're a failure of a communicator. The point is to make others understand what you have in mind, not make them understand that you habitually sniff glue.
58 posted on 02/17/2002 4:43:14 PM PST by A.J.Armitage
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To: ctonious; leadhead
asked the great professor "Well...what can you DO with it?"

I was a physics major through sophomore year, and that was my problem with working on the measurement of cosmic rays.

59 posted on 02/17/2002 4:51:48 PM PST by Lessismore
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To: A.J.Armitage
Thanks for the advice...I'm going to need your wisdom to get the... Realatarian Party--off of the ground!

Are you on or off the bridge---gotta map I can look at?

Let me know before I blow it to smithereens!

60 posted on 02/17/2002 4:52:15 PM PST by f.Christian
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To: A.J.Armitage
Maybe your tank is cracked---outta water...some glue could help you!
61 posted on 02/17/2002 5:06:45 PM PST by f.Christian
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To: A.J.Armitage
I did see the map---your age on your bio...

is that mag-lev---super conductivity your on---higher than a liberal---just lower than anarchy?

Floating reality--Libertarianism?

62 posted on 02/17/2002 5:24:49 PM PST by f.Christian
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To: The Raven
Is it wise for physicists to spend so much energy figuring out the microcosmic mysteries of the universe when they still haven't adequately explained Spam to us?
63 posted on 02/17/2002 5:40:54 PM PST by Yardstick
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To: The Raven
How many of these questions are necessitated by the assumption that red shift = recessional velocity?
64 posted on 02/17/2002 5:48:09 PM PST by aruanan
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To: longshadow; vaderetro; radioastronomer; junior
Bump for tomorrow.
65 posted on 02/17/2002 6:22:26 PM PST by PatrickHenry
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To: f.Christian
Isn't there some medication you should be taking?
66 posted on 02/17/2002 6:22:56 PM PST by A.J.Armitage
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To: PatrickHenry
The Unanswered Questions of Physics have never hurt me. The Unanswered Questions of Chemistry in the second semester of my college freshman year nearly flunked me out.
67 posted on 02/17/2002 6:26:37 PM PST by VadeRetro
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To: A.J.Armitage
Realatarians-science on medication...you make me laugh!
68 posted on 02/17/2002 6:29:44 PM PST by f.Christian
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To: f.Christian
What the heck is a "realitarian" supposed to be? You and your cat?
69 posted on 02/17/2002 6:38:01 PM PST by A.J.Armitage
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To: A.J.Armitage
Yeah the cat corners them and I smash em---rats!
70 posted on 02/17/2002 6:42:08 PM PST by f.Christian
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To: aruanan
How many of these questions are necessitated by the assumption that red shift = recessional velocity?

Probably a lot of 'em.

71 posted on 02/18/2002 1:33:41 AM PST by The Raven
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To: VadeRetro
I was hoping to find the answers to those unanswered questions; but so far this thread isn't solving the Great Problems of the Universe. So I shall lurk ...
72 posted on 02/18/2002 7:49:55 AM PST by PatrickHenry
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To: PatrickHenry
Now think..... There can not be any 'missing' matter.

If it doesn't exist in the universe, it doesn't exist.

We are trying to resolve a 4 dimensional (or higher) universe with a 3-dimensional mind.

73 posted on 02/18/2002 9:05:31 AM PST by UCANSEE2
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To: ChadGore
Question 12: What is that stuff between al gores ears ?

I believe the technical tern for that is VACUUM!

74 posted on 02/18/2002 9:15:59 AM PST by MortMan
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To: mrsmith
"the universe has the simplest shape—it's flat. " ...and when you get to the edge you'll fall off. actually, it's more toroise-shell shaped.

Is this the gratuitous ridicule of the flat-universers?

75 posted on 02/18/2002 9:23:29 AM PST by AndrewC
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To: The Raven
"the universe has the simplest shape—it's flat."

Ummmm... I hate to point out an obvious flaw here, but "flat" isn't a shape. A sheet of paper is flat, too, but it has a rectangular shape.

Oh, and the simplest shape in 3 dimensions is a sphere - it only requires one measurement to describe it (diameter or radius). (Sorry - I'm an engineer, too, and people trying to tell me how important their thoughts are using incorrect terminology drive me bananas ;-)

76 posted on 02/18/2002 9:25:14 AM PST by MortMan
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To: The Raven
Question 12: what happens to socks in your dryer to make only one of a pair vanish?
77 posted on 02/18/2002 9:27:40 AM PST by Poohbah
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To: The Raven
Which question was the one that tackled the issue of the first OJ jury?
78 posted on 02/18/2002 9:27:42 AM PST by A CA Guy
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To: The Raven
12. Who hired Craig Livingstone?

1. What is dark matter? ...All the ordinary matter we can find accounts for only about 4 percent of the universe. We know this by calculating how much mass would be needed to hold galaxies together and cause them to move about the way they do when they gather in large clusters

2. What is dark energy? ...That energy should produce a kind of negative pressure, or repulsion, thereby explaining why the universe's expansion is accelerating.

3. How were the heavy elements from iron to uranium made?

4. Do neutrinos have mass?

5. Where do ultrahigh-energy particles come from?

6. Is a new theory of light and matter needed to explain what happens at very high energies and temperatures?

7. Are there new states of matter at ultrahigh temperatures and densities? ...Quarks are extremely sociable and are never observed in nature alone.

8. Are protons unstable?

9. What is gravity?

10. Are there additional dimensions?

11. How did the universe begin?


79 posted on 02/18/2002 9:39:51 AM PST by malakhi
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To: MortMan
"technical tern"??????

Make that "technical term". I fat-fingered my cheeky response:-(

80 posted on 02/18/2002 10:29:13 AM PST by MortMan
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To: MortMan
>>Oh, and the simplest shape in 3 dimensions is a sphere

They're guessing something like 5-7 dimensions these days

81 posted on 02/18/2002 1:20:05 PM PST by The Raven
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To: f.Christian
Yes I expect people posting to be coherant. You are not. I rarely understand any of your posts. You string together a bunch of words interspersed with lots of "--" and in the end I sit there and scratch my head wondering what the hell I just read.
82 posted on 02/18/2002 5:31:10 PM PST by Exnihilo
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To: Self
As much as I would like to follow this discussion, I can't because I'm anticipating the religious nuts to show up at any moment.
83 posted on 02/18/2002 5:50:37 PM PST by balls
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To: Exnihilo
Yes I expect people posting to be coherant.

You are not alone in your observations, and conclusions.

I propose a simple "coherence" test of any piece of text: if it makes as much sense when read backwards as it does when read normally, it is probably incoherent.

I think you will find this tool of immense benefit when applied to "f.christian's" Thorazine-jag ramblings. I predict that most of them will, in fact, appear to be just as sensible when read backwards as fowards: they will make no sense at all read either way!

84 posted on 02/18/2002 5:58:04 PM PST by longshadow
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To: angelo
That was Brilliant angelo. Thanks for the laughs.
85 posted on 02/18/2002 6:30:32 PM PST by WRhine
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To: WRhine
I'm glad you enjoyed it. ;o)
86 posted on 02/18/2002 8:46:32 PM PST by malakhi
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To: longshadow
Don't worry...when I put up the Realatarian manisfesto---maybe after you get the secret code and handshake everything will fall into place for you. Until then...keep trying---practicing...I want to take it easy on you so the... shock-surprise---won't hurt-kill you!
87 posted on 02/19/2002 1:20:01 AM PST by f.Christian
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To: The Raven
OK..I'll bite...what's the answer to #6??

Sorry for the delay, I had to check with my mom.

The answer to # 6 is:

Enitlavo ruoy knird.

88 posted on 02/19/2002 5:27:13 PM PST by IncPen
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To: IncPen
I hate Ovaltine
89 posted on 02/20/2002 12:55:29 AM PST by The Raven
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