h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The trouble with the laws of physics is that they tend to change whenever someone notices 'the impossible' happening somewhere.

NaCl is table salt. he was refering to HCl (hydrocloric acid)

Ok let's say you are traveling at the speed of light, and as such have aquired infinate mass (and also infinate gravitational atraction) so everything in the universe is accelerating twards you. but wait we're forgeting something... if we are traveling at the speed of light, time for the rest of the universe will have seemed to have stopped, (in relation to you and your vehicle) and as such, nothing would have time to accelerate twards you. Can someone prove me wrong on this?

Gravity travels at the speed of light... you would be generating a gravitational 'boom'

Not true - gravitational effect is instantaneous no matter what the distance. We could send information faster than the speed of light if we could find a way to easily modulate gravity, and detect these modulations at a distance. We can't yet, though.

Is it *really* instantaneous?
Surely that would mean if we did have a good gravity-wave detector we could detect major events such as supernovas, stars falling into black holes, etc long before the light from them reached us. I don't remember hearing anything along those lines before.

If we could build a sensitive enough detector, I'm sure we could tell that they had happened, but not *where* they had happened - being instantaneous, triangulation becomes a case of measuring relative field strength rather than time delays, meaning that the sensors have to be so far apart that the speed of light becomes a limiting factor once more in gathering data from them...

Seriously, though, the gravitational perturbations of rabbits having sex nearby would probably be stronger than a distant supernova.

I just did a quick search and found the following

http://math.ucr.edu/home/baez/physics/grav_radiation.html

It seems that gravity waves probably travel at, or slightly below the speed of light.

*nods*

Of course, they are both gauge boson effects. The speed of light is the speed of an object of zero mass.

I slouch corrected - I had previously been told in a most convincing fashion that every mass in the universe interacted gravitationally with every other mass simultaneously, but with the scale of the effect becoming undetectably small at fairly short distances (on a cosmic scale ). I must be getting my physics info from the wrong pub.

As the speed of a moving object increases, lengths in the direction of travel seem to contract. Taking this to the extreme of the speed of light, would it be correct to say that from the perspective of a photon it is not travelling at all since the distance from 'origin' to 'destination' is reduced to zero?

The same person who told me that gravitational interactions were instantaneous also did a pile of differentiation on the back of a couple of beermats to show that there was only room in the universe for one photon, which from our point of view was simultaneously travelling both forwards and backwards in time. That time he really *was* pissed!

Yeah, according to Einsteins theories gravity travels with the speed of light. Problem is, if it does then how can it escape a black hole? The gravity should pull itself in, isolating it entirely from the surrounding universe. So there´s something we don´t know yet.

Gravity should pull itself in? Do gravitons interact with gravitons?

From the perspective of a mass warping space-time, surely there's no problem? God knows (or Hawking!) what's inside but the outside will still be warped space-time which will surely have an influence on the rest of the Universe in the normal way. Yeah?

Bumble bees can't fly.. So I'm sure eventually we'll discover that the speed of light was only an artificial barrier.. if we survive that long.

'Nonnie

Duh, the bumble bee thig is not much but a joke. The reason they can fly is that they rotate their wings at the same time they flap them, and in that way get more of an up-thing.

Duh, the bumble bee thig is not much but a joke. The reason they can fly is that they rotate their wings at the same time they flap them, and in that way get more of an up-thing.

Duh.. yes, but at one point we didn't know that. It was thought at the time that it was aerodynamically impossible for the bumblebee to fly, so the 'joke' at that time was "but nobody told the bumble bee".. The 'experts' then went about the task of finding out -why- the bumble bee obviously -could- fly, and man's perceptions of what was possible changed.. Which brings us to the whole point. Many things that have previously been thought 'impossible' and are now simple facts of everyday life. Things are only impossible until we figure out how to do it. Eventually things that are "Science Fiction" become "Scientific Reality" (to the demise of some darn nice shows, too ).

Have faith.. The speed of light barrier will be broken, too... As I said before... IF we survive long enough.

'Nonnie

Hmm, in the case with the bumble bee we already knew it was possible, just not how it happened. It is in other cases where you believe something is impossible, and one day it just happens. Which is why you always have to account for the impossible to happen in your planning. As some science dude once said, "The only way to find out what is impossible, is to do it." That was the short version, I can´t remember it all.

There´s the Staying Alive song on the radio, why is there no Staying Alive smileys?

light can not stand still in vacuum it must travel at c (light speed). The only way to stop time is to move at the speed of light and that can not be done unless you are massless.