Things I learned in physics class

POSTED BY: BadgersHat
UPDATED: Friday, August 12, 2005 15:00
VIEWED: 25158
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SIGMANUNKI

Wednesday, July 20, 2005 5:35 AM

The wife found this :

http://physicsmathforums.com/showthread.php?t=56

EDIT: She just told me that it is in the blog of a string theorist.

----
"Canada being mad at you is like Mr. Rogers throwing a brick through your window." -Jon Stewart, The Daily Show

SIMONSAYS

Wednesday, July 20, 2005 5:57 AM

Quote:
Originally posted by thatweirdgirl:
Quote:
Originally posted by SimonSays:
God I love thatweirdgirl
I bet Physics conflicted with Cheerleading Practice Are you really Cordelia Chase?
Or perhaps Harmony?

Cheerleader? Maybe band or AP French...It was a while ago. Um, no. Never ever been a cheerleader. Geek. Nerd. Dork. Or perhaps weirdo would better explain it. I have A Brief History of Time on my clie...I read it whenever I'm bored. I admit, I struggled through the third chapter. Bet it gets easier as you go.

www.thatweirdgirl.com
---
"...turn right at the corner then skip two blocks...no, SKIP, the hopping-like thing kids do...Why? Why not?"

AP French

, Geek

, Nerd

, Dork

....thatweirdgirl will you marry me and have my children?

Remember what LOUIS VUITTON said: "It's in the bag!"

ZOID

Wednesday, July 20, 2005 7:13 AM

SigmaNunki:

I am hesitant to reply to your latest post. Here's my assessment:

1. I never claimed to be a physicist or scientist of any kind. I never claimed to be a mathematician. I have always and ever been very honest about who I am and what 'paths' I have walked during my chameleon-like existence. I have never claimed expertise in physics. Somehow, you have equated my statements, based on books I have read -- written for laypersons like myself by authors like Einstein, Feynman, Hawking and Greene among many others -- as being authoritative indictments of the scientific community.

2. I only intended to present a speculative viewpoint, hoping to get informed opinions from those who work in scientific and other research careers. I also ventured to comment that the differing viewpoints -- many of which have been duly pointed out by each author I have read -- as well as the fantastic basis of QM, reminded me of religion: 'Believing' in something totally unrelated to everyday experience, and which you have very little hope of ever actually observing (i.e, like 'God'), and then settling into 'interpretation groups' regarding the best guess of what is really going on at the most basic level (i.e., like differing sects of the Protestant faith). I said those things and it made you angry. Are you really so easily offended by a confessed layperson? Have I really so grievously sullied the honor of the scientific community that you personally feel the need to lay me low? If so, the scientific community has a much thinner skin than I had credited. Any similarity I might have envisioned between science and religion stopped well short of righteous anger...

3. As stated above, I get the distinct impression that my layman's viewpoints and commentary make you very angry. Does either of us know precisely why? I certainly do not. Based on what you said in your last post, it's because I haven't admitted that you proved me wrong a year ago. I have no emotional investment in being 'right' or in winning a battle of wills. I've always viewed debate as a sport, and I've been known to switch sides in the middle of the match because I felt the other side had valid points that weren't being made (or just to shake people out of their 'comfort zones'). For me, the value of debate is to fully illuminate all the aspects of a topic, not to come to a consensus or declare a winner/loser. But this isn't a sporting debate as far as you're concerned, is it? It's personal, right?

So here's the only question(s) I have: Is there some way of overcoming our differences? Or are you planning on carrying this grudge forever?

I, for my part, am ashamed that I have failed so miserably with another human being. I am well-known in my career field for being able to forge professional working relationships with people whose personal philosophies are adversarial to my own. (NB: Put two controllers in a room; chances are they are adversarial toward one another. Type 'A' personalities rarely settle comfortably into a pecking order.) I'm not saying we should join each other's fan clubs; but, we should at least be able to share our differing opinions on any topic without resorting to negative behavior of this kind. At least that's my opinion, and I am an expert on being me...

Respectfully,

zoid

P.S.
I don't have much hope that this is gonna succeed; but I had to give it one last try.
_________________________________________________

"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein
(NB: Unfortunately, humans are not very good at 'new' thinking.)

THATWEIRDGIRL

Wednesday, July 20, 2005 10:20 PM

Sigma and Zoid,

How can two people I so thoroughly enjoy communicating with not enjoy communicating with each other? Eh. I am glad the physicists and mathematicians can explain the bits and theories to us non-physicists, It's nice. Folks like Zoid (and me) get our info from sources we think are legitimate scholarly sources. We don't know which theorists the physics community rolls their collective eyes. We rely on folks like Sigma to point us in the more accepted direction. I don't know what happened or when to sour your relationship. I'm not sure it is salvageable. I want you both to know that I value your opinions...loud and aggressive though you both may be at times.

Anyway, I'm still reading and learning from this thread. Keep up the discussion.

Respectfully,
TiPpY

www.thatweirdgirl.com
---
"...turn right at the corner then skip two blocks...no, SKIP, the hopping-like thing kids do...Why? Why not?"

THATWEIRDGIRL

Wednesday, July 20, 2005 10:41 PM

Quote:
Originally posted by SimonSays:
AP French , Geek , Nerd , Dork ....thatweirdgirl will you marry me and have my children?

I figured out what class it was! It was Latin. I knew it wasn't anything like Calc since the other kids were able to take it. And then I remembered our valedictorian was in French with me, so it wasn't that either. Latin. I waited to take it my senior year because of all the other stupid classes I just HAD to take kept conflicting with Latin. I gave up physics for Latin. (I was planning a Music major at the time...studying root words seemed more relevant.)

I am spoken for.

Random info: For some reason my Latin classmates nicknamed Sabine.

www.thatweirdgirl.com
---
"...turn right at the corner then skip two blocks...no, SKIP, the hopping-like thing kids do...Why? Why not?"

ZOID

Thursday, July 21, 2005 3:44 PM

TiPpY:

Thank you for your kind words. I'd have to agree that there's some unnavigable gulf separating SigmaNunki and myself. The problem is that I like physics, similar to how I like baseball and basketball: I never played (not to the level of techniques, tactics and strategy) those games, but I do have a fan's appreciation of the techniques, tactics and strategies. I like to consider and discuss these topics; but everytime SigmaNunki sees my name on a physics thread, he lays into me. And I'm not going to stop posting simply because someone tells me I should be quiet and let the people with brains talk. I'm too stubborn (mea culpa) and, frankly, that kind of intellectual elitism offends my sensibilities. So, everytime a physics thread comes up, we're going to have this gruesome exchange. Very disappointing for everyone involved, especially the other readers who wanted to read something enlightening, not these embarassingly adolescent exchanges...

On a more serious note, what's this, "I'm spoken for" nonsense? I was planning on leaving my wife and kids for you, you vixen! But then I remembered what I look like, and realized the probability of success for the plan was on the extreme fringe of the scatter chart, so I snuffed the plan. Still, with Feynman's "sum-over-histories" approach ( http://en.wikipedia.org/wiki/Path_integral_formulation ), the electron of my fantasy actually explores all possible paths (including making out with the green chick from the Star Trek TOS pilot) before striking the "zoid loses" phosphor.

In this scenario, "It's the thought that counts", since that's what generates the 'fantasy electron'. And in the case of the 'multiverse' ( http://en.wikipedia.org/wiki/Many-worlds_interpretation ) my 'fantasy electron' actually creates an infinite number of separate universes, one for each possible outcome, so right now, in another universe, I'm making out with Anne Francis (TV's Kitty West and lone female star of "Forbidden Planet"). Every fantasy of mine's got Anne in it somewhere...

Now, perhaps, you can understand why I like physics so much: I'm an incurable hound...

Historically,

zoid

P.S.
Anyone: Quantum mechanics + gravity? Pretty please? Or how about one or two of those predicted but experimentally unobserved (as yet) particles? "Inquiring minds want to know".
_________________________________________________

"Sure as I know anything, I know this: I aim to misbehave." -Capt. Mal Reynolds, Serenity, a.k.a. 'the BDM'

FOURSKYS

Thursday, July 21, 2005 4:19 PM

Ok, so I thought I'd pop back into this thread after about a week of absence. Anyway...

My only real comment on the whole "belief in physics" (mostly becuase I like philosophy, phyiscs, and debating) argument is that they really are two separate things. There is the "Philosophy of Physics" which entails the Many-Worlds theory versus Copenhagen and such, and there the "Mathematics of Physics". The philosophy of physics is primarily the untennable things that are debated and people will adhere to much like a belief system. People will tell you that the Copenhagen interpretation of QM is right or wrong, but there is absolutely no proof either way. Belief? Yes. Like a religion? Um...Sure.

But then there is the mathematics. The math is undeniable. Anybody who starts with the same set of assumptions gets the same set of answers. There are no "belief" systems involved. The math just works. The only possible room for aargument here is in those assupmtions. But there really is no "belief" in the scientific community about those assumptions. Everyone agrees that they are just assumptions, and could be proved wrong at any moment. People publish papers with topics like "what happens if asusmption A is wrong?" It's not a matter of believing in the assumptions, its a matter of making the proper assumptions such that our math reproduces the observed results. Belief? No. Acceptance? Yes. Like a religion? Certainly not.

An example: Scientists don't "believe" (=like a religion) that the speed of light is constant. It can be observed to be the case, at least in our local universe. But there are camps of scientists who think that it may NOT have been constant over the entire history of the universe. It's an assumption in the math that may or may not be right. It's what is used now because it's commonly accepted. It can change, and it'll cause a stir in the scientific community if it does, but show some proof (or a reasonable argument) and you'll sway people over to your side. Religious tennets just don't have that kind of flexibility...

FourSkys

P.S.
"Quantum Mechanics + gravity? Pretty please?"
Good luck with that :-)

QBEAM

Thursday, July 21, 2005 5:01 PM

Quote:
Jayne gets hit and goes flying back a few metres. Looking at it from a conservation of momentum point of view, the guy who fired it should have flown back about the same distance to conserve momentum. Basically, when the alliance guy fired the weapon, it should have pushed him back with the same force that hit Jayne.

Imagine the sonic gun as being like a cannon. You remember what happens to cannons that arent tied down? hehe...

Something like this was on mythbusters a few weeks ago.

You're going about this all wrong--you have to assume that what you observe is true, and then deduce why it happens that way. That's the experimental method!

So, how could the gun knock Jayne down, but not push the guy holding it backwards? Obviously, there must be some kind of back-blast. Guys who fire Bazookas don't get knocked backwards at all...

QBeam

QBEAM

Thursday, July 21, 2005 5:28 PM

Quote:
I like your idea about constant 1g acceleration, though I'd have to sit down and do the math (after remembering) to figure out how long it would take you to get to any significant speed. As far as your thought of a brief period of freefall: You could simply have your ship make a wide turn using some sort of RCS - without cutting the main drive - until it pointed in the opposite direction. That would eliminate any weightlessness. If you stretched that manouver out over a long enough period of time, the passengers/crew would barely notice the change in direction.

I once did the calculation, and discovered that, for a ship that continuously accellerates at 1g, it takes roughly 6 years (subjective) to get anywhere, regardless of how far away it is. It takes about 2.5 years to get to a relativistic speed, and, of course, 2.5 years to slow down again. The year in the middle is enough to travel an effectively infinite distance, since time is essentially stopped for you.

In objective time (an oxymoron, but you know what I mean), you can approximate pretty well using newtownian mechanics. If you approximate 1g as 10m/s, and c as 4*10^8m/s, that means you spend 2*(4*10^7s)--otherwise known as about 1 and 1/4 years--to get to c. You get another 15 months decellerating, so that's a total of 2.5 years at 1/2c, and the rest of the time, obviously, at c. Convert all that to light-years, since that's how we generally think of interstellar distances, and it turns out it takes 2.5 years to go the first 1.25 light years, and 1-for-1 after that. So just take the distance in light years and add 15 months. Easy!

Sadly, I don't think any of this applies to Firefly, because my understanding is all the places Serenity goes are all in the same star system. That means, even at 1g, Serenity never travels far enough to build up relativistic speeds, as far as we know.

QBeam

SKYDANCE

Thursday, July 21, 2005 5:30 PM

Quote:
Originally posted by TheGreyJedi:
The guns the alliance uses, to me at least, seem to be sonic based. Sound, no matter how focused, isn't going to do a whole lot to a heavy metal door with a solid lock. Not for a while at least. A human, however, with it's squishy fleshy bits is likely to catch the sonic wave like a sail and go flying back like a plastic bag in the breeze.

Hmph.

The key here is the wide dispersion of the energy. You can see from the distortion in the air that the energy expands in a cone, and strikes the target more or less evenly over an area about a foot in diameter. If you're tackling someone with 100 lbs of force, they'll fly backwards. 100 lbs applied to a steel door isn't going to make it budge (although it might rattle).

You're wrong about "no matter how focussed," though. If you could focus sound well, and you had enough energy behind the blast, you could certainly damage a door. It's all about the amount of force being applied (actually, physicists calculate this type of interaction as an "impulse," not a force, but go ahead and think of it as force). This weapon is designed to stun people, not damage buildings, so the amount of energy delivered is relatively low.

In other news ... don't try to overanalyze the physics of Firefly. *sigh* There's a lot of Hollywood Physics in the series.

Did we establish already the extremely high amount of gravity present in space? It takes an awful lot of energy to accelerate out of the Earth's gravity well, to "escape velocity." It takes even more energy to reach "escape velocity" for our Sun, and tremendous amounts of energy to reach escape velocity for our galaxy. You're just being confused by the fact that gravity moves the ship the exact same way it moves you: you're both falling/orbitting at the same acceleration. You feel pushed when the ship's engines are running because the engines push the ship (changing its velocity), and then the ship has to push you to get you to match its velocity. If gravity is doing all the work, then it reaches through the walls of the ship to move you directly (and even through your body to move your liver directly), so there's no transfer of energy between you and the ship (or between your liver and the muscles in your body).

I'm not a physicist, but I did get my bachelor's degree in physics.

__________________________
"They weren't cows inside. They were waiting to be, but they forgot. Now they see the sky and they remember what they are."

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