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Although I’m rather new to physics and this site, I wanted to ask a question because it’s been sitting on my mind recently and I can’t figure it out... Forgive me if I’m missing something but here goes.

It is said that when an object approaches the speed of light, it’s mass increases very, very much. However, If an object travelling nearly light speed is also not a black hole seen as how it is not a black hole in its reference frame, what happens to the mass gained by the object due to this speed?

What I mean is, although it is not a black hole in its reference frame, thereby not allowing it to be a black hole in any other reference frame, it will still be a very heavy object when seen in its own reference frame, with tons of mass relative to volume due to the approaching of light speed. Doesn’t this mean that, in the object’s frame of reference, it will become a black hole, thereby allowing it to become a black hole in all frames of reference.. Provided I’m not missing anything, this means that objects approaching near light speed will produce a black hole in all frames of reference. I say this because: A.) if we say that the object isn’t stationary because of how heavy it is, this means that the near light speed velocity of the object is absolute because, in the object’s own reference frame, it has a definite velocity that is non-zero, thereby meaning that the object can become a black hole at near-light speeds; B.) if the gained mass is of the object in its own reference frame is seen as “not there” due to the lack of velocity of the object in the current reference frame, that means that mass is as referentially dependent as velocity, which doesn’t make sense to me.

I apologize if this didn’t make sense, I tried my best and please forgive my lack of experience with this information.

Qmechanic
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TP110011
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"When an object approaches the speed of light, its mass increases" is NOT true. If it were, you could do something like put that person on a weighing machine which triggers a bomb if its reading were above a fixed value (e.g. $100 kg$). This would be contradictory to what that person sees, since it is equally valid for them to consider themselves at rest and everything else in the universe to be moving backwards at nearly the speed of light.

The point of the thought experiment above is that all observers agree on the weight registered by the weighing machine, and that value is the one which would have been recorded if the person were at rest.

Once past this misconception, the rest of the question becomes moot. There simply isn't "extra mass", and so no black hole either.

Allure
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    Thanks, mate. I appreciate you helping me solve my brain conundrum... I must've gotten my information wrong... – TP110011 Aug 07 '20 at 07:11
  • Relativity used to be taught using the term 'relativistic mass', but it's not done that way anymore (in general) as it was quite confusing to students - as you've just shown! It's a concept that is a) confusing and b) not actually needed. Sadly, that means that the web contains a lot papers/tutorials/presentations that use it, and there are text books containing it still in circulation. – simon at rcl Aug 07 '20 at 15:06