The Astrophysical Hotseat

[Will]

Can you prove that there is no God with out using any terms of evolution?

[Beartalon]

Will, can you prove there is a God without using any religious terminology?

[This message has been edited by Beartalon (edited 11-19-2002 11:47 PM).]

[Ghost Post]

that's odd, i checked out a book on astrophysics, and there's no chapter on god. could it be the two are unrelated?

[Lepton]

What are you working on now? Probably related, what's your Ph.D. thesis based on? Who are you working with?

Also, would you be willing to come to Saint Mary's University in Halifax, Canada to give a short presentation on your work some time?

Have you seen the "Scientific American" Cosmoslogy issue?

Given the relative uncertainties associated with using quasars and type Ia supernovae to determine interglactic distances, what do you forsee being the next astrophysical "measuring stick"?

Were there scalar fields in the early moments of the universe?

Do astronomical superstrings exist, and if so, why haven't we detected any yet? (they should kinda stick out, shouldn't they?)

A recent slew of new planets has been discovered around other stars than the sun being (a) very large, and (b) very near to the sun. Do these results arise simply because such planets are most easily detected, or because solar systems actually favour Jovian bodies with small orbital radii?

Will supersymmetric string theory or M-theory be able to accurately depict the creation of the universe? Is there a deeper understanding that humankind can determine than string/M-theory? Will Einstein's dream of a single equation to describe the entire universe ever be realized?

[Lucky Wizard]

Will, this is the astrophysical hotseat, not the atheistical hotseat. The words do look similar, but they're different. (And RSA rules.)

Zarriar: I'll let Borodog elaborate, but in the meantime, a google image search for galaxy cluster provides some good results.

Lepton, I can't explain why most of the planets have been close to their parent stars, but the reason most of them have been large is probably because those are the ones we can detect using current methods.

And I'll let Borodog answer the rest.

[Ghost Post]

since other people are answering for borodog, i will too. he'll be at your school next week for a lecture, Lepton.

[Lepton]

Thanks for you answer, Lucky Wizard. Let me now rephrase the question:

A recent slew of new planets has been discovered around other stars than the sun being (a) very large, and (b) very near to the sun. Is there any reason to believe that our solar system is not typical, given this new information? [edit]y'know, besides supporting "intelligent" life[/edit]

[This message has been edited by Lepton (edited 11-20-2002 12:30 AM).]

[Chuck]

Yeah, we're not typical. Plug another 1/1000000 into the Drake equation.

[JediSoop]

This isn't really astrophysical but in the crossword today, the clue was "Satellite of Jupiter". _ L _ R A

Any help is appreciated And yes, I know I can just go online and look up the moons of jupiter but I feel like bugging Dawg with my pedestrian comments. *pokes dawg*

[Evil Empire]

Hey Soopy I know that one...

It's Elara; the reason I know is kinda funny (at least I think so).

One of my cats is named Tsunami. When I first got him he had a lot of gas so I started calling him Jupiter because he was the gas giant. Anyway, my other cat Ella followed him everywhere so I looked up the moons of Jupiter and started calling her

You guessed it, Elara.

Tsunami is better now and Ella doesn't follow him around anymore so the names didn't stick.

Sorry for jumping in Boro but since I'm here...

I saw a show on supermassive blackholes and was interested in your thoughts. It basically concluded that the majority of galaxies have them and that they may be interagal in the actual creation of galaxies.

[edit]sleepy post



[This message has been edited by Evil Empire (edited 11-20-2002 11:13 AM).]

[JediSoop]

THanks empire! *pencils in Elara*

And nice story btw It bothers me slightly that Ella lost her fascination with Tsunami after his problem was solved but hey, to each cat her own...

[Agamemnon]

Borodog old chap,
Do you think it could be possible in the future to harness the light and energy from Active Galactic Nuclei ? Do you think this could be used as an alternative energy source for our planet that can be safe, harmless and non-poluting?

[Buzzsaw]

Agamemnon, Old Bean, what on earth are you drinking?
~takes a shot of whatever 'smart juice' Aga's having~

[firemeboy]

Is it true that if you head out in a space ship at constant speed, you will end up where you started from?

If so, how do you define infinite space?

Can you detect exact spot where the big bang happened? (Kind of like the center of the baloon).

I'm sitting in my chair not moving relative to the things around me. However the earth is spinning, it's revolving around the sun, and the sun is cruising through the galaxy, so in fact I'm moving. We know that the closer you are to the speed of light, the slower time moves for you (everybody experiences time much 'faster' than you do). If that is true, then if you were to slow down, say come to a complete stop (is that even possible), would time effectively stop? You could live 50 years in another person's minute?

Or we basically 'at rest' right now? And any movement can only toward the speed of light? It seems to me that if you can go in one direction (faster toward the speed of light), and you are already moving (cruising through the galaxy), then you should be able to move in the other direction (slower than you were before).

This thread was a good idea by the way...

[firemeboy]

And one more question...

http://www.cnn.com/2002/TECH/space/11/19/blackhole.merger.ap/index.html

Why must everything happen in 'millions of years'? Doesn't the universe know that we want things now? Better yet, during prime time? What is this 'long time' it takes for everythign to happen, hasn't the universe heard of a friggen sound bite?

*Wanders off to watch TV*

[One Skunk Todd]

Actually FMB, the article says the galaxy is 400 million light years away and the collision will take place in a "few" hundred million years, meaning that we won't see it for that long. But it could be that it's happening right now or it's already happened and you just missed it.

How fast does gravity propagate?

[Borodog]

Do galaxies combine to form larger structures? If so what do they look like?

Galaxies do in fact combine; larger galaxies like ours can "swallow up" smaller galaxies such as already mentioned. Smaller galaxies can combine to form larger galaxies. In fact, it is thought that all galaxies formed from the accumulation of smaller "galaxy-lettes", basic dwarf irregular bundles of stars, dust, and gas. Large galaxies can collide and form truly enormous galaxies like M51, that contain trillions of stars (the Milky Way contains about 100 billion stars). But no matter how big they get, they're still called galaxies.

[edit]Galaxies also come in clusters, and galaxy clusters form superclusters, but that's not really galaxies "combining".[/edit]

Could you give an idea of how quickly the shock wave onsets, propagates etc?

After a high mass star completely runs out of fuel in the core, i.e. ther core is (almost) entirely iron, trouble comes on quickly. The star collapses in under a second, bounces, and the shockwave travels outward at thousands of kilometers per second.

Can you prove that there is no God [pointless qualifying clause deleted]?

No.

What are you working on now? Probably related, what's your Ph.D. thesis based on? Who are you working with?

Currently, I am working hard on a project called "procrastination." It requires most of my time.

Seriously, though, my research and thesis focus on the hydrodynamic behavior of accretion disks around compact objects (white dwarves, neutron stars, or black holes) in close binary stars. I use a custom time-dependent, three-dimensional fluid dynamics code to simulate these accretion disks on supercomputers. Most work of this type in the past has been limited to 2D, or to poor resolution simulations. Look here for some examples. This is a little out of date, since I haven't updated it in a month, and things are changing rapidly. For instance, the most important thing may not be difficulty in detecting spiral shocks, but rather the effects I've discovered could be responsible for significant mass and angular momentum transport (i.e., accretion).

Also, would you be willing to come to Saint Mary's University in Halifax, Canada to give a short presentation on your work some time?

Perhaps if they foot the bill; I do not have travel money for such a trip, unfortunately.

Have you seen the "Scientific American" Cosmoslogy issue?

No. What's in it?

Given the relative uncertainties associated with using quasars and type Ia supernovae to determine interglactic distances, what do you forsee being the next astrophysical "measuring stick"?

Once we understand the mechanism, possibly gamma ray bursts. But in truth, I think that it's unlikely that there will be another seminal "yard stick" that ever gets used; the methods we have now get better calibrated every year, meaning that the error bars get slightly less ever year. I think that it's quite likely that the Hubble constant will be nailed down within the decade.

Were there scalar fields in the early moments of the universe?

Do astronomical superstrings exist, and if so, why haven't we detected any yet? (they should kinda stick out, shouldn't they?)

I'm out of my depth on these questions, as I don't generally keep up on this sort of stuff. But I have heard it postulated that dark matter may in fact be superstrings. However these theories are really over my head, and mostly sound like mathematical voodoo until somebody comes up with some observables to disprove them with (to me, anyway).

A recent slew of new planets has been discovered around other stars than the sun being (a) very large, and (b) very near to the sun. Do these results arise simply because such planets are most easily detected, or because solar systems actually favour Jovian bodies with small orbital radii?

You can't discount the latter, but it is almost certainly the former. Given any distribution of planetary sizes and orbital radii, you will be able to detect larger planets at smaller radii first. As techniques and technologies get better, scientists are in fact finding smaller planets, and planets at larger radii.

Will supersymmetric string theory or M-theory be able to accurately depict the creation of the universe? Is there a deeper understanding that humankind can determine than string/M-theory? Will Einstein's dream of a single equation to describe the entire universe ever be realized?

Again, out of my depth. But from what I read of the people who understand this stuff, M-theory certainly looks the most promising. And by purely aesthetic arguments, I believe, that yes, a single equation will be find that describes all of the fundamental "rules" of physics. Such an equation, of course, will not "describe the universe", any more than writing down Maxwell's Equation (a single equation, with appropriate operator definition, that describes all of electromagnetism) describes the sunset. There will always be work for physicists; in fact, I think there will be infinietly more work to do once the "ground rules" are finally understood.

Is there any reason to believe that our solar system is not typical . . . ?

The sun actually is atypical as most stars go; most stars are in multiple star systems. Isolated single stars such as ours are the exception, rather than the rule. However, with regards to the distribution of planets around such stars, it is simply too early too tell. The best way to see this is the fact that from the typical distance we are detecting these planets, we wouldn't be able to detect any of our own solar system's planets (the last I heard, anyway).

I saw a show on supermassive blackholes and was interested in your thoughts. It basically concluded that the majority of galaxies have them and that they may be interagal in the actual creation of galaxies.

The majority of large galaxies, such as ours, certainly should have them. It's a little chicken-and-eggish to say that they "may be integral in the actual creation of galaxies"; it's just as easy and valid to say that supermassive black holes are the inevitable result of the formation of large galaxies.

Do you think it could be possible in the future to harness the light and energy from Active Galactic Nuclei ? Do you think this could be used as an alternative energy source for our planet that can be safe, harmless and non-poluting?

Uh, no. The nearest active galactic nuclei are hundreds of megaparsecs away,

Is it true that if you head out in a space ship at constant speed, you will end up where you started from?

That is unknown. It depends on the topology of the Universe. Remember the cities on the balloon? That would be true on the balloon, since it is round, but it certainly would not be true if (for example) the balloon was an infinite flat rubber sheet that was stretching, instead. Or a hyperbolic paraboloid, for instance. It would be extremely difficult, in fact to determine what topology the world had, since the local curvature will be damn near zero (and equal, for the flat sheet) in all of them. This is why we currently do not even know if the univers is finite but unbounded (like the surface of the earth) or infinite in mass and extent (like the infinite rubber sheet).

Can you detect exact spot where the big bang happened? (Kind of like the center of the baloon).
No, that's the point; the Big Bang happened everywhere. It happened right where you're sitting now, and everywhere else, as well.

I'm sitting in my chair not moving relative to the things around me. However the earth is spinning, it's revolving around the sun, and the sun is cruising through the galaxy, so in fact I'm moving. We know that the closer you are to the speed of light, the slower time moves for you (everybody experiences time much 'faster' than you do). If that is true, then if you were to slow down, say come to a complete stop (is that even possible), would time effectively stop? You could live 50 years in another person's minute?

That's not how it works; it's when you speed up that time slows down for you (relative to an outside observer), not when you "stop". The universe actually does have a preferred rest frame, by the way; it is defined by the cosmic background radiation. Anyway, if you hopped into a spaceship and took off at near the speed of light, your time would slow down relative to me in my fixed inertial frame. You could live a minute in my 50 years.

Or we basically 'at rest' right now? And any movement can only toward the speed of light? It seems to me that if you can go in one direction (faster toward the speed of light), and you are already moving (cruising through the galaxy), then you should be able to move in the other direction (slower than you were before).

Everyone who is not accelerating is "at rest"; they are in an inertial reference framce. We here on the surface of the Earth, by the way, are most defninitely not in an inertial reference frame. We are being accelerated by the floor. You can feel it pushing up on your feet at 9.8 m/s^2. Astronauts floating around in "zero gravity" (a misnomer) are[/] in inertial frames, since they feel no acceleration. Of course the look like they're accelerating to us, since they're moving in a circle, but that's not special relativity's fault. Anyway, any two clocks in different inertial frames will tick at different rates, and two observers with the two clocks will [i]each see the other's clock as the one moving slower. I'll leave it for an excercise to the reader to sort this out.

How fast does gravity propagate?

Gravity propagates at the speed of light. If it didn't, believe it or not, you could use that for faster-than-light communications.


------------------
Insert humorous sig here.



[This message has been edited by Borodog (edited 11-20-2002 02:41 PM).]

[Agamemnon]

Ok then, I'll try again ~sigh~

Do you think it could be possible in the future to harness the light and energy from Active Galactic Nuclei, if we ever find a nearer source or become able in some way to reach the ones we know of ? Do you think this could be used as an alternative energy source for our planet that can be safe, harmless and non-poluting?

[firemeboy]

quote:

---

That's not how it works; it's when you speed up that time slows down for you (relative to an outside observer), not when you "stop". The universe actually does have a preferred rest frame, by the way; it is defined by the cosmic background radiation. Anyway, if you hopped into a spaceship and took off at near the speed of light, your time would slow down relative to me in my fixed inertial frame. You could live a minute in my 50 years.

---

Wait, so it is only when you are speeding up that time 'distorts'? So for example. A twin brother and I are born at the exact same time. Let's say he speeds up to %75 of the speed of light and then stops accelerating. Is time now the same for us? He is moving at a constant, and I'm moving at a constant (on planet earth). While he was speeding up time slowed down for him, but once he hit the constant speed, time is now the same for both of us? Note, I understand that to each person, time never would have shifted, but when you compare the two then there would have been a difference.

The reason I ask is that I always thougth it was just speed. I thought there was an experiment where two atomic clock were placed on a water tower, one at the top, and one at the bottome. They registered time differently.

And about the big bang thing happening everywhere, I thought that they have figure out about how much mass was in a certain area right before the big bang went off. If they are talking about a finite area, doesn't that area have to be a particular place?

I'm getting a bit confused, which is par for the course on this topic.

[Samadhi]

[Borodog]

Wait, so it is only when you are speeding up that time 'distorts'? So for example. A twin brother and I are born at the exact same time. Let's say he speeds up to %75 of the speed of light and then stops accelerating. Is time now the same for us? He is moving at a constant, and I'm moving at a constant (on planet earth). While he was speeding up time slowed down for him, but once he hit the constant speed, time is now the same for both of us? Note, I understand that to each person, time never would have shifted, but when you compare the two then there would have been a difference.

The reason I ask is that I always thougth it was just speed. I thought there was an experiment where two atomic clock were placed on a water tower, one at the top, and one at the bottome. They registered time differently.

It is speed. Perhaps my prose was not clear. Two clocks, not accelerating, in two different inertial frames (i.e. moving relative to one another) will each observe the other to be ticking at a slower rate than themselves. The reason in the "Twin Paradox" that only one of the clocks shows this "time dilation" when the twin comes home from his trip near the speed of light, is that he has not remained in an inertial frame; he has been accelerating. There can be no confusion about who has accelerated and who has not; each can do experiments to verify whether their frame is inertial or not.

And about the big bang thing happening everywhere, I thought that they have figure out about how much mass was in a certain area right before the big bang went off. If they are talking about a finite area, doesn't that area have to be a particular place?

No, because that "area" contains within it what is now all of the space within the universe. The Big Bang did not expell matter into the void; the void expands and takes the matter with it.


------------------
Insert humorous sig here.

[Samadhi]

That's succinct enough. Still hurts my brain. Especially when the mass of the universe affects the acceleration of the expansion, but there's no, like, "central core" that it's pulling it to. Basically it's just difficult to wrap my brain around the fact that while locally our Galaxy and another Galaxy may be accelerating each other there is no overall acceleration towards or away a center (or even by the universe at large).

[Edit: Of course, what I just said is probably rife with misconceptions]



[This message has been edited by Samadhi (edited 11-20-2002 05:35 PM).]

[Lucky Wizard]

Ah, OK. The use of the word "structure" made me think galaxy clusters would answer his question.

And now for my question. Where do the heavier-than-iron elements, such as iodine and uranium, come from?

[OcularGold]

what do most astrologists believe to be the likelyhood of intelligent life existing elsewhere in the universe? the probabilty of intelligent life existing in the milky way? and of simple lifeforms? do you believe there to be intelligent life somewhere else?

and heres one thats been bugging me for a while: what determines the speed of light, exactly? why couldnt it have been 4 X 10^8 m/sec?

do wormholes really exist?

arent leptons and neutrinos smaller than quarks, or am i confused?

where do we stand on using anti-matter as an energy source?

[Athene]

If time slows down under the influence of gravity, why isn't time moving infinitely fast in space? Have astronauts ever noticed any time dilatation while being in space (or on the moon)?

If you were situated in the middle of a perfectly round, masive hollow sphere, would the sphere's gravitation
a) "cancel out" and leave you weightless and floating in the middle, or would
b) each part of the sphere "attempt" to draw you near, as a result pressing you to the walls of the sphere as if it was rotating or would
c) something completely different happen?

[Evil Empire]

Originally posted by Harry Caray on Space: The Infinite Frontier:

---

We all know that the moon is not made of green cheese.
But what if it were made of barbecue spare ribs. Would you eat it then?
I know I would. Heck, I'd have seconds. Then polish it off with a tall, cool Budweiser.

---

[firemeboy]

OK, thanks for the clarification on the expanding matter.

I may be thick headed, but let me ask one more follow up on the clock thing. As I mentioned, on earth we are moving in several different ways. I don't know how fast it is, but it's pretty fast. What happens if you were to get off the earth, escape the gravitational pull of the earth and sun (or rather get in an area where other gravitational bodies cancel the affect), and in affect slow down. Could I live in that state for 20 years, and then go home to find my son has only aged a few days or years?

[Borodog]

Where do the heavier-than-iron elements, such as iodine and uranium, come from?

In the cores of massive stars, heavy elements up to and including iron are created in a process called helium capture, or alpha capture (an alpha particle is basically a helium nucleus, i.e. a helium atom with the electrons stripped of). Now, the core of a star is seething with photons, so some of these elements get broken up, leaving free neutrons floating around (this is called photodisintegration). Because these neutrons are not electrically charged, they can easily be captured by nuclei like iron 56, to create iron 57. But iron 57 is radioactively unstable, and will decay, emitting a beta particle (i.e. an electron), and convert into cobalt 57. Shampoo, rinse, repeat. You can create atomic nuclei significantly heavier than iron in this manner. This is called the s-process, short for slow neutron capture. However, at some point the half life of certain elements is so brief that it is unlikely you can capture another neutron in time to build up certain elements. But during a supernova explosion, the densities around the core become so high that you can simulataneously capture many neutrons at once, breaking this barrier, and creating extremely heavy nuclei such as uranium and plutonium. This is called the r-process, short for rapid neutron capture. The heaviest elements are still so unlikely to be produced, and are so radioactively unstable that they essentially do not exist in the universe unless we go to great lengths to manufacture them.

More questons answered later.


------------------
Insert humorous sig here.



[This message has been edited by Borodog (edited 11-21-2002 05:23 PM).]

[Samadhi]

It seems that the astrophysicist covers many fields (nuclear physics, chemistry, optics,...)

What fields would you say an astrophysicist must know (at least have a grounding in anyway)?

[firemeboy]

Homemaking, first. If you can't cook a nice casserole, you can just forget about the rest...

[Borodog]

what do most astrologists believe to be the likelyhood of intelligent life existing elsewhere in the universe? the probabilty of intelligent life existing in the milky way? and of simple lifeforms? do you believe there to be intelligent life somewhere else?

First, I haven't the foggiest idea what "astrologists" believe.

Assuming you meant astronomers, it's all over the map, since basically, we have no idea and it's impossible to tell.

Personally, I think this most likely the scenario:

Simple life is nearly ubiquitous; you can't keep the stuff down, it grows like weeds, pun intended. There is mounting evidence that Mars once hosted life, and there is mounting evidence that Venus hosts life even as we speak. It would not surprise me at all if the liquid water oceans of Europa, and even the jovian atmosphere itself hosts life.

The reason I think this is that the fossil record on Earth shows that simple life was already on the scene almost immediately after the Earth cooled enough for it to survive. The Earth's crust seems to have cooled and solidified at about 4 GYA (GigaYears Ago), while the first indications of single celled life may be as soon as 3.9 GYA. If it showed up that quickly, it couldn't have been that hard.

Now, on the other hand, I think complex, multi-cellular life may be much more rare. Life on Earth was restricted to single celled life forms for over three billion years. The explosion of multi-cellular life seems to have occurred only about 600 MYA (the Cambrian "explosion"); this was most likely the result of a dramatic climate shift that unfroze the plonet from a state of perpetual, total, ice-locked glaciation (all the way down to the equator). From that point it took another 600 MYA for us to happen along.

So to sum up I think this:

Simple life is common.
Multi-cellular life is rare.
Intelligent life is extremely rare.

Put numbers on any of these? No chance.

what determines the speed of light, exactly? why couldnt it have been 4 X 10^8 m/sec?

As much as some people dislike it, I firmly believe in the Anthropic Principle. If the speed of light, or the mass of the fundamental particles, or the fine structure constant, etc. were evenly slightly different, our Universe would not exist in a way that was conducive to the formation of stars, heavy elements, planets, chemistry, life, intelligence, and us. The numbers are the way we see them to be because they have to be for use to measure them in the first place. I'm confident that there could be billions of universes will all sorts of values for these fundamental constants, and they are either empty voids or collapsed black holes.

do wormholes really exist?

Most likely, but they collapse before you can observe them. Space is probably seething with tiny wormholes, but they don't do us any good.

arent leptons and neutrinos smaller than quarks, or am i confused?

You're confused. As far as we can tell, all of those are "fundamental" particles; i.e. they are not made up of smaller particles. None of them have a "size" in the classical sense; they are all esentially pointlike.

where do we stand on using anti-matter as an energy source?

Nowhere near. Even if you could contain and control it magnetically, it costs about a quadrillion dollars per gram to manufacture (no, I'm not kidding).



------------------
Insert humorous sig here.

[Borodog]

If time slows down under the influence of gravity, why isn't time moving infinitely fast in space?

Because that's not how it works. First of all, space is "full of" gravity. Hence the moon doesn't fly away from the Earth, or the Earth away from the sun. Second, define "time moving infinitely fast". I can't, other than an infinite number of ticks coming out of a clock in an infinitesimal space of time. Third, gravity slows time down, just like brakes slow down your car, but that doesn't mean the absence of gravity means time moves faster than normal, any more than not brakes implies your car is suddenly moving infinitely fast.

Have astronauts ever noticed any time dilatation while being in space (or on the moon)?

Did astronauts notice it? No. The effect is too small. Has it been measured with atomic clocks? Yes. Many, many times. Orbiting satellites must have such relativistic corrections build into their navigational software to even remain useful.

If you were situated in the middle of a perfectly round, masive hollow sphere, would the sphere's gravitation
a) "cancel out" and leave you weightless and floating in the middle, or would
b) each part of the sphere "attempt" to draw you near, as a result pressing you to the walls of the sphere as if it was rotating or would
c) something completely different happen?


A.



------------------
Insert humorous sig here.

[Borodog]

As I mentioned, on earth we are moving in several different ways. I don't know how fast it is, but it's pretty fast. What happens if you were to get off the earth, escape the gravitational pull of the earth and sun (or rather get in an area where other gravitational bodies cancel the affect), and in affect slow down. Could I live in that state for 20 years, and then go home to find my son has only aged a few days or years?

No. We are not, in fact, moving very fast at all (compared to the speed of light, which is what matters).

For example, the surface of the Earth at the equator moves at about 1000 miles per hour. That is about 1 millionth the speed of light. The speed of the Earth about the sun is about 10 miles per second, about 1 200000ndth the speed of light. The speed of the sun around the galaxy is about 20 miles per second,about 1 100000ndth the speed of light. None of these are large enough to produce any noticeable time dilation if you could get away to intergalactic space and "stop" relative to the cosmic background radiation.


------------------
Insert humorous sig here.

[Borodog]

It seems that the astrophysicist covers many fields (nuclear physics, chemistry, optics,...)
What fields would you say an astrophysicist must know (at least have a grounding in anyway)?

All of them, which is why I like it so much. Nuclear physics, particle physics, cosmology, chemistry, optics, quantum mechanics, statistical mechanics, fluid dynamics, magnetohydrodynamics, electricity and magnetism, classical mechanics, celestial mechanics, orbital mechanics, chaos theory, you name it, we've got it. The entire gamut of physics is useful somewhere in astrophysics. That is true in no other branch of physics, from my experience.


------------------
Insert humorous sig here.



[This message has been edited by Borodog (edited 11-22-2002 10:29 AM).]

[Borodog]

Woops, forgot one.

Could you explain what "the universe expanding" means? And/or point me to some good links for the layman?

It means just what it looks like. The space that makes up the universe is "stretching", just as the surface area of a balloon increases when you blow it up. The large scale structures of the universe are along for the ride; like pictures drawn on the balloon they scale up with it.

Rather than links, I would highly recommend Hawking's A Brief History of Time for anyone interested in this type of stuff.


------------------
Insert humorous sig here.

[Pablo]

If you were in a room where all the walls, the ceiling, and the floor were mirrors, and you turned out the light, how long would it take to get dark?

And don't try to bullshit me.

[Pablo]

What advice would you give to all the little kids out there who want to grow up to be astrophysicists?

[Samadhi]

[Borodog]

If you were in a room where all the walls, the ceiling, and the floor were mirrors, and you turned out the light, how long would it take to get dark?

It would get dark immediately. Mirrors are not perfect reflectors, and they would absorb the light faster than you could take your hand away from the switch.

If you want to assume the mirrors are perfect reflectors, then it would still get dark immediately, since you're in the room to observe the scene, and you certainly are not a perfect reflector (though perfect in other ways you may well be).



------------------
Insert humorous sig here.

[Lucky Wizard]

Thanks for the answer, Borodog.