The Astrophysical Hotseat

[BraveHat]

These three questions may seem irrelevant, so I won't get vexed if you refrain from answering them. Did you read the book and/or see the film version of Contact? If so, did you have any lasting thoughts on it? If so, what are some of them?

[Borodog]

I saw the movie. It was ok; nothing special, in my opinion. Radio astronomers certainly do not listen to what comes out of the radio telescopes; that was a complete crock. I also have it on good authority (from an aquaintence who worked at the VLA) that they most certainly do not have big screen graphical computer workstations, and that for cinematic reasons they seemed to have reversed the layout of the inside of the building.


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[Pablo]

What if you are in a room and the walls, floor and ceiling are all perfect reflectors, and there's a light on in the middle of the room. How bright will it get in there?

[Logain]

If you constructed a spacecraft with a hull that had rings all along attached to it (picture a shaft with rings around it, like a person with multiple hula-hoops surrounding their body), and under solar power, these rings would begin to rotate around the hull. If you started with a motionless spacecraft, would angular momentum begin to propel the ship forward once the rings started turning?

[Pablo]

Coincidentally, Logain, that was my senior physics project. Unfortunately, I managed to get the rings on backwards, so they spun the wrong way and propelled the ship in reverse causing it to fall onto my car.

To this day, I still don't understand why it works that way, though. F=ma and momentum is basically mv, so why does momentum propel the thing? I also think Boyle and Charles noodled around with this subject for a while. I'm sure Borodog will enlighten us, but I probably won't understand the answer anyway.

[Borodog]

What if you are in a room and the walls, floor and ceiling are all perfect reflectors, and there's a light on in the middle of the room. How bright will it get in there?

Eventually the light bulb would absorb enough light that it would burst. The light bulb bits would eventually absorb all the light from the room and re-radiate it away as heat. So again, the room would end in darkness.



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[Borodog]

If you constructed a spacecraft with a hull that had rings all along attached to it (picture a shaft with rings around it, like a person with multiple hula-hoops surrounding their body), and under solar power, these rings would begin to rotate around the hull. If you started with a motionless spacecraft, would angular momentum begin to propel the ship forward once the rings started turning?

No. Angular momentum would make the rings continue to rotate once you stopped actively spinning them up, that's all. I imagine it would be really hard to ride a bike if the wheels worked the way you suggest.



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[Pablo]

If there were a parallel universe to ours, what in that universe would correspond to our black holes?

[Borodog]

Their black holes.

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[Samadhi]

Do you think quark matter struck the earth?
http://news.bbc.co.uk/2/hi/science/nature/2502755.stm

Next one is sort of not related, but as you said earlier all science is covered
Do you agree with Sir Arthur or the detractors when it comes to cold fusion?
http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2000/festival_of_science/919953.stm

[Borodog]

Do you think quark matter struck the earth?

Possibly. It's the only hypothesis so far. One thing the theory has going for it is that it actually predicted these types of events, and only subsequently did they go out and find them.

Next one is sort of not related, but as you said earlier all science is covered
Do you agree with Sir Arthur or the detractors when it comes to cold fusion?

I agree with some things, and disagree with others. I agree that it is foolish to dismiss things out of hand. On the other hand, I have not heard of any of these "literally hundreds" of reports of "something strange going on". I completely disagree with the ideo that we're at the end of the "oil age" or whatever he called it; that's just silly (I could expand on why, if anyone is interested). Regardless though, if there's anything to it, the truth will win out. It always does in science.



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[Samadhi]

So you don't think MOND is a viable theory?

What about Matrioshka brains?

[This message has been edited by Samadhi (edited 11-22-2002 07:13 PM).]

[Borodog]

So you don't think MOND is a viable theory?

Well, I'd never heard of it before. While we've certainly modified the fundamental laws of dynamics before (can you say relativity, kids?), I'll put this down for the time being as provacative but unconvincing. First, there are more indications that "dark matter" exists than simply rotation curves in spiral galaxies. There is also line broadening in elliptical galaxies, kinematics of galaxies within clusters, gravitational lensing, and the real killer for this MOND theory, as far as I can tell, hot intercluster gas in hydrostatic equilibrium.

What about Matrioshka brains?

Looks like interesting science fiction. Maybe some day. I am a big believer in Vernor Vinge's "singularity" idea.

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[This message has been edited by Borodog (edited 11-22-2002 03:24 PM).]

[Aarondalf]

[Borodog]

You must be British, right?

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[Pablo]

He's Aussie.

[Borodog]

Same thing, but with crocodiles.


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[Aarondalf]

Brittish?!?! I feel so dirty.

Next you will be saying that I'm a bloody Kiwi... *shudder*

(What made you think I was Brittish?)

[Samadhi]

What's the difference?

[Aarondalf]

!!!

[Lepton]

Kakapoes.

[Samadhi]

I thought that was the difference between the US and Canada. Oh, nevermind I remember now....that's back bacon. And fat comics.

[Borodog]

The British are known amongst Americans for their appreciation of dry wit. The Aussies are only known for crazy guys who fuck with crocodiles and corny phrases like "Crikey! G'dye, mite!"


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[Internet Stranger]

and vegemite.

[extropalopakettle]

To me, they all speak English with a funny accent.

[Zarriar]

Why is it that space does not expand uniformly? It seems that the space between galaxies is "stretching" but not the space within galaxies.

[Borodog]

Why is it that space does not expand uniformly? It seems that the space between galaxies is "stretching" but not the space within galaxies.

If you were to somehow "turn off" the eletromagnetic, gravitational, and other forces that bind together your body, the Earth, stars, and galaxies, then the intermolecular distances in all of these objects would increase, but only by extremely small amounts. For example, if the Hubble Constant is taken to be 65 km/sec/megaparsec, then the velocity of recession between two points a meter apart would be about 2x10^-24 meters per second; effectively zero, esspecially compared to the tremendously strong forces holding mass together like gravity and electromagnetism.


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[VinnyQ]

I just saw "Space Station 3D" at the Lockheed Martin IMAX Theater in D.C.

I so want to work on the project. What does it take to be able to work for the International Space Station?

[pikachamp]

I got this science fiction book from the library by William Slater called Singularity, it says they found the "other side" of a black hole that exists in another universe, and that time sped up around it.
This made me think.
Is there such a athing as a white hole?
Is there such a thing as anti gravity?
Would a white hole have massive antigravity?
Would antigravity speed up time?

[Pablo]

Is it OK for a capricorn and a leo to get married?

[Samadhi]

What do you think our best choice for interstellar travel is? Lightsails?

[Lepton]

How can you explain Pika using mathematical determinsim?

[Aarondalf]

Pablo and Lepton, you both fucking rock! =^_^=

[pikachamp]

what is mathematical determinism?

[Lepton]

for example:

P - I^k/cA + hAM + P' = Pika
where:
P = subject (initial)
P' = subject (final)
I = Irritability
k = a term roughly equal to the inverse of mass (=~ c^2/E)
E = consumed energy (ie. ingested glucose )
c = ideal speed of light in a vacuum
A = an index based on the surroundings of the subject (a happy place is close to 1, the maximum, and a dungeon is close to 0, the minimum)
h = Planck's constant (very small...10^-34 or so)
M = Inverse mental capacity of surrounding individuals

[Aarondalf]

Sorry Pablo, but Lepton rocks even harder! This thread is great.

[Faeriefire]

Borodog, you are my idol! It is my aspiration to get a doctorate in astrophysics. I'm still working on my bachelors.
Where are you going to get your doctorate? Where did you go to get your masters? Would you recommend this place?

[Pablo]

[Borodog]

What does it take to be able to work for the International Space Station?

You'd probably have to be an astronaut or a scientist, well known in your field. But quite frankly, I wouldn't want to have anything to do with the ISS, for reasons of principle. The ISS is a multi-gigadollar boondoggle that, much like the shuttle it was designed to be built, crewed, and serviced from, is draining billions of dollars of taxpayer money from projects that are much more science and results "dense", like mining the asteroids (you knew it had to come up, right?).

Is there such a athing as a white hole?

No. The idea of the "white hole" was originally proposed to explain quasars (QSRS, Quasi-Stellar Radio Sources), pointlike radio sources at enormous redshift and hence distance. Because of their distance, they had to be enormously bright. Now we know that quasars are simply tremendously bright active galactic nuclei; they are powered by accretion disks around supermassive black holes at the centers of galaxies.

Is there such a thing as anti gravity?

Not that we know of, although very soon after the Big Bang, the Universe does seem to have undergone a period of "inflation" (i.e. expanding much more quickly than predicted), and as somebody mentioned earlier, some people have some results that they interpret to imply that the expansion of the Universe might be accelerating (enough qualifiers in there for you?). So, who knows?

Would a white hole have massive antigravity?

Since they don't exist, it's irrelevant.

Would antigravity speed up time?

Who knows? You can't really say until you specify what "antigravity" is. Let's just put it this way; the only "room" in the equations of general relativity for something akin to "anti-gravity" is the "cosmological constant", and I don't think that it can "speed up" time.

Is it OK for a capricorn and a leo to get married?

No. Their child would be the Antichrist.

What do you think our best choice for interstellar travel is? Lightsails?

Lightsails would certainly work. They could be accelerated with orbital lasers, for example. There are simply to many variables to be able to say off the top of my head what the "best" chance would be. Personally, I'm a fan of the Project Orion; nuclear blast propulsion.

Where are you going to get your doctorate? Where did you go to get your masters? Would you recommend this place?

I got my BS and MS at the same place I'm getting my Ph.D. (I know, I know; academic inbreeding; I like it here, so sue me). At beautiful North Carolina State University. I'm sure there are better schools, but yes, I'd recommend it. I love it here. I love the department, the campus, we have a resurgent football team, two hours to the beach, three to the mountains. And my advisor is a great guy.

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[This message has been edited by Borodog (edited 11-27-2002 02:26 PM).]

[Samadhi]