Theoretical Physics [OT thread]

[a philistine]

quote:

---

Originally posted by Derek:
Ok, couple of things:

Gravity waves: physicists are spending large amounts of money on gravity infereometers to detect the presence of gravity waves. No-one has done so yet, but there is hope. Gravity wave detection is extremely difficult (if they even exist), because it is very hard to account for all disturbances possible. However, it is known that gravity, like other forces, travels at c (speed of light in a vacuum)
{snip}Derek

---

Wasn't there observational (non-experimental) proof of gravity waves from rotating pulsars? I think it resulted in 1993 Physics Nobel?

--A Philistine

[Darwin]

God, I've got to fresh up on my physics. Wow, yeah when I was talking about nothing going faster then the speed of light I was leaving out theorical particals for the sake of simplicity.

Isn't there something weird about the mass of Tachyons? Like having a zero mass? Or is that Neutrinoes?

[Derek]

Negative mass.

Or imaginary mass.

It depends on how you look at the equations.

By the way, by imaginary, I mean i, as it sqaure root of negative one style imaginary.


Derek

Physics is fun!

[apache]

"Kimball: I love it when engineers talk physics. It adds humor to my day..."

Hmm, us engineers love it when scientists try to talk about theoretical impossibilities. Nothing has yet proven to be impossible. Flying? Nope, done that. Speed of sound? Nope, done that too. Flat Earth? Heh, yeah right. The moon? Yep, been there. Weightless environments near the surface of the Earth? Thats old news. Some day we will be saying the same thing about going faster than c.
Some things I would never hope for, though, are time travel (throws all conservation laws out the window, while creating fantastic paradoxes), getting 'out' of a black hole (you have a spec of dust that was your space ship, try getting that out of infinite gravitational force), and creating matter/energy (how do you create something from absolute nothing?).

[Suicide Junkie]

Hate to tell you, but black holes do emit stuff and lose mass.

Hawking Radiation, where the black hole tends to absorb negative energy (and hence mass) from just outside the event horizon, and release positive energy(mass) to the environment.

Just one more thing to include in the list of not-impossible things.

[Derek]

Besides, a black hole is not an area of infinite gravity. It is an area where, after you go through the so-called 'event horizon', the escape velocity is greater than c, the speed of light.

Thats all.

Derek

[Suicide Junkie]

It may have infinite density at the centre, but it only has finite mass.

If it had infinite mass, the entire universe would be inside the event horizon. (as soon as the gravity's effect spread out)


------------
PS. as for the 'weightless environments near earth' Might you be referring to the Vomit Comet, or something more dramatic that I can't remember?

[This message has been edited by suicide_junkie (edited 01 March 2001).]