General Physics help!

[GutZ]

I am new and I haven't really joined in much physics discussion because well, I just recently got interested in it. I've read a few books with general introductions to I guess "Modern physics" but there are a few things I don't understand. If you could help me out that would be great.

 

Special Relativity /w General.

 

1) In regards to curvature of space and time, it seem to me that would imply a definite finite universe. Is that correct? Also is the curvature indefinite, like plastic deformation?

 

2) This Time dilation and length contraction, Here is the given example:

 

"Consider two observers, each in a space-ship laboratory containing clocks and meter sticks. The space ships are moving relative to each other at a speed close to the speed of light. Using Einstein's theory:

 

Each observer will see the meter stick of the other as shorter than their own, by the same factor gamma (- defined above). This is called length contraction.

Each observer will see the clocks in the other laboratory as ticking more slowly than the clocks in his/her own, by a factor gamma. This is called time dilation."

 

http://www2.slac.stanford.edu/vvc/theory/relativity.html

 

So does this "Time dilation and length contraction" happens to both observers? How is it that it appears shorter and slower?

 

Quantum

 

1) The uncertainty principle. Is the uncertian based on one particles postion and velocity or does this incorperate other particles?

 

 

I think I have some more but I can add on later right?

[[Tycho?]]

Yes you can add on later. However, I would recomend looking around these forums for a few days. Topics like relativity are very common, and you can learn a lot just by passively reading.

 

SR and GR do not imply a finite universe. They just dont.

 

For the time dilation thing, yes it applies to both. Each would see the effect occuring to the other. There have been numerous threads on exactly this subject in the relativity forums.

 

I'm not really sure what you're asking for the quantum one, but as far as I know the uncertainty principle is based aroung the uncertainty of individual particles; ie you can apply the principal in a one particle system.

[swansont]

I think I have some more but I can add on later right?

 

It's better to segregate topics, and as Tycho? said, read other posts. They abound on the topics you have mentioned.

 

 

[disembodied Obi-Wan voice]Use the search function[/voice]

[Severian]

I am new and I haven't really joined in much physics discussion because well' date=' I just recently got interested in it. I've read a few books with general introductions to I guess "Modern physics" but there are a few things I don't understand. If you could help me out that would be great.

[/quote']

 

I would recommend a different thread for each question in future. Otherwise people tend to answer one and not the others.

 

1) In regards to curvature of space and time, it seem to me that would imply a definite finite universe. Is that correct? Also is the curvature indefinite, like plastic deformation?

 

As has been already mentioned, there is nothing in SR or GR which forces a finite universe. I am not sure what you mena by the second part - if you mean 'does the curvature change?' then yes, the curvature changes in response to the energy/mass present.

 

So does this "Time dilation and length contraction" happens to both observers? How is it that it appears shorter and slower?

 

The crucial point is that the measurment of time and distance are not universal - they are different for different observers. The length of an object for example is not a well defined quantity unless you specify the frame you are observing from. I am not going to rederive this here, but it is a logical consequence of the speed of light being the same in all reference frames.

 

1) The uncertainty principle. Is the uncertian based on one particles postion and velocity or does this incorperate other particles?

 

It is either. Usually it is expressed in terms of one particle because that is the simplest case. But when one has multiparticle systems one still has an uncertainty. notice that this is not an uncertainty inherent in measurement - this is an uncertainty inherent to the particle itself. If the energy of a particle is fixed to one value then the particle is spread out - it doesn't have a definite position, and so we cannot meanure a definite position.

[GutZ]

I didn't want to hijack someone elses thread to ask my questions, so thats why I did it in that form. I will do as you say though from now on.

 

In regards to the first question though, I meant more of when matter curves space and time, doesn't that mean it would have to have a force from a different source acting against it to create the curve? Like a boundry, for example: A sledge hammer hitting a sheet of metal. If the metal didnt resist the impact would it just go through it? I think I am looking at it from a wrong perspective maybe.

 

The third question was basically to find out if the uncertainty was the same for many particles regardless of velocity, position, and amount/concentration like relative uncertainty, ha (joke), I guess it would be called that if it were.

 

I have to look up these reference frames, that confuses me as well. I have a book on modern physics but the vocabulary use is not what I am use too. It makes it seem more complex so subconsciously I believe what I am reading has implifaction (Is that even a word) that I am not picking up, confusing me even more.