Approaching light speed

[initiate]

I got a, pretty much amateur conjecture i deem of interest for the educated people around here.

 

As we know, the closer a massive body approaches c, the more mass it gains. Now as much as I know, volume isnt subject to change here (correct me if im wrong), so the only value that increases here is density. The asymptotic nature of this scenario means that there is no limit to how much mass a massive particle can gain as it approaches light speed.

 

So my conjecture is this: wouldnt any particle or body with mass become a black hole when it reaches a certain percentage of light speed?

[ajb]

So my conjecture is this: wouldnt any particle or body with mass become a black hole when it reaches a certain percentage of light speed?

You must take care not to mix concepts and reference frames here.

 

The particle reaches a certain percentage of the speed of light as measured in what reference frame?

 

The mass is usually understood as the 'rest mass' and so this does not change. You cannot force a body to be a black hole by just moving away from it fast enough.

[swansont]

No, it wouldn't, which is one way of telling you that mass doesn't actually increase with speed. Energy does, and some people define a mass (called relativistic mass) as E/c², but that's a different mass than appears in most equations. Basically, the conditions of forming a black hole depend on the frame of reference (it's not just mass, as with Newtonian gravity) used to analyze it. If it doesn't form in the rest frame, it won't form in another frame.

[initiate]

mmm, great! thanks! this is so interesting

[Delbert]

So my conjecture is this: wouldnt any particle or body with mass become a black hole when it reaches a certain percentage of light speed?

It seems you're viewing the speed of light as an absolute. In contrast, there is no such thing as absolute speed in the universe. All one needs to do, I suggest, is to ask what speed does one think one is doing right now? If you do I think you could come up with anything from zero to close, if not at, the speed of light.

 

The speed of light is based on physics and not absolute speed, as defined by James Clark Maxwell. What that means is that the speed of light will be the same for everybody - irrespective as to what 'speed' the observer thinks he or she is doing. In other words, speed is relative as defined by Einstein.

 

Which, from your question, implies that mass is also relative. A particle may appear heavier relative to us when it's speed is faster relative to us. But presumably if you or I were to hitch a ride on said particle (just a thought exercise), we'd feel more or less the same, but then it would be the things around us that would be different. For exactly the same reason when taking the question above about what speed one is doing right now (i.e. the Earth), one might come up with a speed close to the speed of light, or maybe at the speed of light, and as far as we can tell we are not a black hole.