## Search found 289 matches

Wed Jan 07, 2009 3:36 pm UTC
Forum: Science
Topic: Magnet Question
Replies: 15
Views: 1691

### Re: Magnet Question

I have nothing to add to the above explanations, but just a thought/question. Based on the explanations, if one took a hammer and smashed one of the magnets how would the fragments orient themselves? I guess for simplicity's sake, imagine the fragments are of equal size and shape. I'm imagining a f...
Wed Jan 07, 2009 2:19 am UTC
Forum: Science
Topic: Magnet Question
Replies: 15
Views: 1691

### Re: Magnet Question

basically, the magnet wasnt held together by its own magnetism at first. It was held together because it was a solid. There was probably an internal stress due to the non-aligned magnetic regions before it broke. Ur gunna need glue now or something.
Mon Jan 05, 2009 8:55 pm UTC
Forum: Science
Replies: 41
Views: 5010

Velifer wrote:(without getting all mathy)

Here is the problem. Has anyone "got all mathy" with many worlds? I feel like everything Ive heard about it glosses over the details. say something has a probability of 1/pi of happening and it happens. How many universes are created?
Mon Jan 05, 2009 3:49 am UTC
Forum: Science
Replies: 41
Views: 5010

also, Ive always wondered about this. If the many worlds theory is true, and a new universe is created for each possible outcome, how would probabilities work? Its not like every wavefunction is an equal combination of 2 states. You usually have an infinite number of possibilities with 0 probability...
Sat Jan 03, 2009 4:47 pm UTC
Forum: Science
Replies: 41
Views: 5010

I have many problems with the many worlds theory. Here are a few. 1. It assumes the universe gives a crap what we do, and can give a crap at all. 2. It assumes distinct timelines, which don't exist due to relativity. 3. It violates occam's razor. Isn't it more likely that, assuming a timeline can ex...
Sat Jan 03, 2009 3:12 am UTC
Forum: Science
Replies: 41
Views: 5010

I dont like the multiple-timeline explanation. An hour before he goes back in time, nobody came and killed him, so he doesn't go back in time and kill himself. Its like asking what if a person falls off a cliff but doesn't?
Wed Dec 31, 2008 1:44 am UTC
Forum: Science
Topic: speed of light in a black hole
Replies: 15
Views: 2185

### Re: speed of light.

it's not obvious without general relativity, a subject about which I know almost nothing, being a lowly undergrad.
Sat Dec 20, 2008 3:18 pm UTC
Forum: Science
Topic: Relative Velocity/Energy Question
Replies: 2
Views: 803

### Re: Relative Velocity/Energy Question

I am pretty sure energy is only conserved in a given reference frame. If you change reference frames, the energy need not be the same.
Sat Dec 20, 2008 3:16 pm UTC
Forum: Science
Topic: Fiery crushy burning death
Replies: 9
Views: 1474

### Re: Fiery crushy burning death

For the first one. Which reference frame? I don't have time to do out the math, but to a proton it might feel like 15 mins if its going 1/3c. Then again Im sure the quoted number is in earth frame time, since that is the only useful one. So I dunno...
Fri Dec 19, 2008 7:35 pm UTC
Forum: Science
Replies: 9
Views: 1093

### Re: A question about motion

ah ok then you should be able to work it out from here. All you need is vertical displacement.
Fri Dec 19, 2008 2:34 pm UTC
Forum: Science
Replies: 9
Views: 1093

### Re: A question about motion

well your problem then is that a pendulum is not a simple harmonic oscillator unless you are considering very small angles (<3-5 degrees) about the eqilibrium. Even if that is the case however, the spring constant k would depend on the length of the rope. Pendulum motion is completely determined by ...
Fri Dec 19, 2008 1:36 am UTC
Forum: Science
Replies: 9
Views: 1093

### Re: A question about motion

if that is the case though, you would have to have been given the length of the rope on the swing.
Thu Dec 18, 2008 10:17 pm UTC
Forum: Science
Replies: 9
Views: 1093

### Re: A question about motion

You are waaaaay overthinking it. Im assuming by pulled back it means vertical height? How much energy does the child/swing have in the beginning? What kind of energy is gained when the child is pulled back? How much energy is this? This can be done in 1 line.
Thu Dec 18, 2008 10:13 pm UTC
Forum: General
Topic: The Spider (Image) From Hell
Replies: 264
Views: 60485

### Re: The Spider (Image) From Hell

Surprised this one hasn't been posted: http://img241.imageshack.us/img241/8521/cil1el2.jpg http://img214.imageshack.us/img214/2755/cil2bo0.jpg http://img179.imageshack.us/img179/8398/cil3om4.jpg ...Wouldn't really want to wake up to and see that on you're ceiling in the morning... sometimes I wonde...
Mon Dec 15, 2008 6:03 pm UTC
Forum: Science
Topic: Space question
Replies: 14
Views: 2072

### Re: Space question

Isn't the working theory that time is linked to the exapansion of the universe? Therefore, if you stopped the expansion, time would stop moving forward. If the universe shrank ("Big Crunch") time would go backwards (along with entropy). This would seem to apply to a localized pocket just ...
Sat Dec 13, 2008 1:50 pm UTC
Forum: Science
Topic: A Couple Seemingly Simple Physics Problems
Replies: 7
Views: 1595

### Re: A Couple Seemingly Simple Physics Problems

for the first one, where along the ladder can you say the force is applied? I believe you used that its applied to the top. *hint*
Fri Dec 12, 2008 3:52 am UTC
Forum: Science
Topic: Physics GRE
Replies: 13
Views: 22090

### Re: Physics GRE

ok that makes a little more sense. I added Chicago and U Illinois urbana-champaign to the list. Really all of them are still top 10, but I just need to get into 1.
Thu Dec 11, 2008 10:26 pm UTC
Forum: Science
Topic: Help with schroedinger's cat
Replies: 20
Views: 3266

### Re: Help with schroedinger's cat

I agree with gammashield. It seems a large jump to go from not accepting that something in quantum mechanics is non-intuitive to there exists an infinite number of universes each created when a macroscopic object interacts with a microscopic object. Its like saying little gremlins move particles aro...
Thu Dec 11, 2008 1:31 pm UTC
Forum: Science
Topic: Physics GRE
Replies: 13
Views: 22090

### Re: Physics GRE

that reminds me. Asad, were you applying for theory or experiment? Im going for condensed matter experiment, which I have heard is the easiest to get into. Particle theory is the hardest. This might make sense how somebody (you) with such high scores etc could get rejected by so many places. If you ...
Thu Dec 11, 2008 3:56 am UTC
Forum: School
Topic: "Ouch" moments in school
Replies: 514
Views: 54361

### Re: "Ouch" moments in school

I hate it when profs take offense to a student being good at their subject. A long time ago, in 8th grade band, we had a written music theory test that I apparently got a 97 on. Everyone else BOMBED it. I had taken piano lessons since I was 6 so I knew music theory pretty well. Anyway, when we got t...
Thu Dec 11, 2008 1:23 am UTC
Forum: Science
Replies: 58
Views: 6059

Its because you have already failed. Causality goes in the forward time direction. Since before you went back in time, you had not killed your grandfather. Even if there is some story of him almost getting killed by somebody looking suspiciously like you, he didnt die. So when you go back, he wont ...
Wed Dec 10, 2008 3:46 pm UTC
Forum: Science
Topic: Physics GRE
Replies: 13
Views: 22090

### Physics GRE

Hey I just got my physics GRE scores and I wanted some people's opinions. I am applying to top schools including MIT, Harvard, Yale, and UC Berkeley along with 1 or 2 not so top schools as safeties. I have good research experience (published twice), a gpa of 3.87 with a physics gpa of 3.97. On pract...
Wed Dec 10, 2008 12:43 pm UTC
Forum: Science
Replies: 58
Views: 6059

Its because you have already failed. Causality goes in the forward time direction. Since before you went back in time, you had not killed your grandfather. Even if there is some story of him almost getting killed by somebody looking suspiciously like you, he didnt die. So when you go back, he wont d...
Thu Dec 04, 2008 7:52 pm UTC
Forum: Science
Topic: [Physics]Light (it's speed and fun things to do with it...)
Replies: 27
Views: 3440

### Re: [Physics]Light (it's speed and fun things to do with it...)

it means within your reference frame, light takes x/c seconds to reach an object, where x is the distance and c is the speed of light.
Thu Dec 04, 2008 1:26 pm UTC
Forum: Science
Topic: [Physics]Light (it's speed and fun things to do with it...)
Replies: 27
Views: 3440

### Re: [Physics]Light (it's speed and fun things to do with it...)

Diadem wrote:That's actually not that hard to see it done. It's done in any 1st year physics course on relativity.

fix'd unless you're a really really smart freshman, or copying notes.
Wed Dec 03, 2008 4:38 am UTC
Forum: Science
Topic: What's up with Polyyne?
Replies: 18
Views: 2110

### Re: What's up with Polyyne?

why is it explosive? Probably because you have lots of carbons with very little oxygens. Carbon likes oxygen. Same reason gas burns.
Mon Dec 01, 2008 4:27 am UTC
Forum: Science
Topic: You might be a physics major if...
Replies: 540
Views: 62546

### Re: You might be a physics major if...

Alefgard wrote:... when you lay down and look at clouds you start thinking about flow and liquid mechanics, regardless of how hard you try not to.

I do this every time when I see a river flowing over small stones...
Sat Nov 29, 2008 2:47 am UTC
Forum: Science
Topic: Childhood (not so) crackpot theories
Replies: 435
Views: 72730

### Re: Childhood (not so) crackpot theories

I have read that some here thought of the number line as a circle. When I was about 14, I took this one step further: a 2D coordinate system was an infinitely big ball (which, being infinite, would make the coordinate system flat again!), so on the other side, exactly opposite of (0|0), there would...
Tue Nov 25, 2008 6:10 pm UTC
Forum: Science
Topic: Dark matter and energy
Replies: 11
Views: 1400

### Re: Dark matter and energy

nobody really knows so you can speculate all you want. Physics isn't done by saying I feel like x is true. For this reason I am NOT a proponent of the multiverse theory because there is no evidence for it and it is more of a what-if-this-were-true type thing.
Mon Nov 24, 2008 5:41 am UTC
Forum: Science
Replies: 58
Views: 6059

The past has already happened. The time traveler only has one personal past; if (s)he goes back in time and meddles around, that's already happened. This is consistent with Consistent Histories. This is my favorite and personal belief. Why make up the idea of many universes and all that crap when y...
Wed Nov 19, 2008 2:36 am UTC
Forum: Science
Topic: You might be a physics major if...
Replies: 540
Views: 62546

### Re: You might be a physics major if...

*proud that his off-topic remark from many posts ago is causing strife*

Tue Nov 18, 2008 2:53 am UTC
Forum: Science
Replies: 39
Views: 4222

Dredging up this topic with a question: I'm thinking of taking a gap year between this job and going to school to travel a bit, and more specifically, teach English somewhere exotic (Thailand or Japan). I'm pretty set on this being a positive experience, but have a passing hesitation about it being...
Sun Nov 16, 2008 6:02 pm UTC
Forum: Science
Topic: Free energy?
Replies: 39
Views: 3905

### Re: Free energy?

if it does give any net increase in energy it will be taken from the atmosphere, and will not really be free.
Fri Nov 14, 2008 9:17 pm UTC
Forum: Science
Topic: Measuring Released Energy
Replies: 2
Views: 707

### Re: Measuring Released Energy

I am not a chemist but maybe do it in an insulated enclosure and measure the temperature? You'd have to know the specific heat of the mixture, which would probably change as the reaction happens, so maybe not the best method. edit: never mind, the reaction sounds explosive and the energy would not l...
Thu Nov 13, 2008 5:46 pm UTC
Forum: Science
Topic: Traveling Faster Than The Speed Of Light.
Replies: 12
Views: 1977

### Re: Traveling Faster Than The Speed Of Light.

What they said, and as to the why question, there really is no answer to that. It's like asking why the big bang? Science strives to model nature, but can never explain nature's purpose. So we observe that no matter how fast you are moving relative to another object, light for both you and the objec...
Wed Nov 12, 2008 4:26 pm UTC
Forum: Science
Topic: Help! Need more graphic representations of science!
Replies: 46
Views: 12664

### Re: Help! Need more graphic representations of science!

Which religion is your roommate? If he is catholic, tell him the Catholic church officially accepted evolution (and the big bang). http://en.wikipedia.org/wiki/Evolution_and_the_Roman_Catholic_Church I fail to understand how any catholic can believe ID when their own church has accepted evolution.
Thu Nov 06, 2008 5:05 pm UTC
Forum: Science
Topic: None like it hot!
Replies: 11
Views: 1696

### Re: None like it hot!

Well, since the last ice age was only a few degrees colder than the current average temperature, Id say only a small amount. Its really impossible to quantify though. 10% would be quite enough.

Also, its not all about human survival in cold temps. If all our food dies, so do we.
Mon Nov 03, 2008 5:49 am UTC
Forum: Science
Topic: You might be a physics major if...
Replies: 540
Views: 62546

### Re: You might be a physics major if...

Oh me yarm I use ansatz all the time and people give me funny looks.

Also, saying "it's only quantum mechanics", because I am realizing more and more that it is in fact one of the easier branches of physics (at least at my level). This also gets funny looks.
Thu Oct 30, 2008 7:33 pm UTC
Forum: Food
Topic: silly rabbit! Cereal is for Dinner!
Replies: 98
Views: 14534

### Re: silly rabbit! Cereal is for Dinner!

Am I seriously still the only one who loves Cinnamon Toast Crunch the most? You're all crazy...
Wed Oct 29, 2008 9:28 pm UTC
Forum: Science
Topic: idea about perpetual motion and want to know why wont work
Replies: 29
Views: 3656

### Re: idea about perpetual motion and want to know why wont work

Friction kills most perpetual motion ideas This would be true if "perpetual motion" meant simply moving forever. This can easily be achieved by being in orbit etc. Its more about doing work, but needing no energy input, ie the creation of energy. [/nitpickiness] Also yes, there will be an...