Math Is Fun Forum

Ciao Libera!

Io sono inglese, vivendo a Londra, e studio l’italiano da quindici anni; mi piace molto questa bella lingua. Ho diversi amici italiani a Londra e mi piace parlare con loro in italiano.

Credo che una versione italiana di questo sito sarebbe un’ottima idea!

Un saluto.

Q: What radio station do chemists like to listen to?
A: 100 Fm.

(Fermium has atomic number 100.)

And I get …

[list=*]
[*]

… tada! Is it right? Is it? Yes, I’m very sure it is.

Let me check … first:

[list=*]
[*]

so it is indeed a unit vector. Now

s0 DÔA = CÔD. And … drum roll …

– so CÔA = 2·DÔA = 2·CÔD!

YES!!

Okay, let me try something else. I will assume OC to be in the plane formed by OA and OD and let (r,s,t) be a nonzero vector perpendicular to this plane. We have

[list=*]
[*]

which leads, on eliminating s and t, to

[list=*]
[*]

Now we can’t have r = 0, otherwise s = t = 0 as well. Therefore:

[list=*]
[*]

Now substitute for z from my previous post and we can pin down x and y a bit more.

My life is just like English grammar. Although the past might be irregular, the present is perfect and so I need not be tense about the future.

—Vinnie Jones

Q: Why do geometers never get lost?
A: Because they can use compasses.
* * *
Q: How did the awkward mathematician go off?
A: At a tangent.

It comes from the formula for relativistic momentum:

[list=*]
[*]

where p is momentum and m₀ is rest mass. Simply put p = 0 for a particle at rest.

It’s a good article. Here are a few of my suggestions.

Firstly, I think the little story between Alex and Sam can be omitted. I don’t see how it’s relevant to relativity – more like having to do with theories of expanding space (e.g. by viewing 3D space as embedded in a larger 4d hyperspace – much like the 2D surface of a sphere is embedded in 3D space).

Secondly, I would mention that things like length and mass also depend on speed: the faster an object moves relative to an observer, the shorter (in the direction of motion) and more massive the observer will measure it to be.

And thirdly, you didn’t mention the most famous equation in all of physics: E = mc²! Most people who are not familiar with special relativity may still be familiar with this equation, so I think it would be a give them some background information on it.

Never fight fire with fire. Always fight fire with water. It’s more effective.
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Like attracts like. (With the exception of electric charges and magnetic poles.)
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Be a member of the Self Preservation Society: do whatever it takes to stay alive, even if it kills you!
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Thanks for your replies.

I don’t know what I’ve done but I hope it’s nothing wrong. For the moment I can get around using a proxy server. I just have to be extra cautious now or the proxy will get banned as well!