why can’t a particle with rest mass accelerate to the speed of light

Question

I assume this has something to do with general relativity, but i don’t exactly get it so

In: Planetary Science

Answer 1

The easiest answer I can think of –

What we used to “know” was when you push on something it moves faster, push on something twice as hard, it moves twice as fast. etc. It’s important to note that in this view 100% of the “push energy” goes into the moving energy.

What we now “know” is that not all the push energy goes into the moving energy. Some %, let’s say X% gets “absorbed” by the thing your pushing and turns into mass.

Making it harder, X isn’t even consistent. Basically the faster the thing is moving the bigger X is. So in our daily lives where we don’t see things moving especially fast X is basically 0.0000001%, even bullets are “slow” in this regard.

But if you took a bullet and just kept pushing and pushing and pushing eventually it’s moving fast enough where X is 1% or 5% or 20%.

So at those speeds not only is a lot of your push “disappearing” and not becoming moving energy, ALSO the object is getting *heavier* meaning your next push is going to have less of an effect anyway.

So it’s two exponential problems – Problem 1: eventually all of your push is getting absorbed as mass and none is going to actually making the thing move faster and Problem 2: your thing is getting infinitely heavy as well so pushing it gets even harder until it’s impossible.