I recall that if an object is at or near the speed of light. Additional energy added will mostly or completely be converted to mass.

Does that really act as mass? Does the object exhibit a gravity field equivalent to a more massive object? If not. What is happening with additional energy? If two such objects were traveling parallel. Would they interact as if they were more massive? Or see each other as their usual mass without the added energy to mass amount. ( some fuzzy idea about relativity in my thinking )

Or am I not recalling the concept correctly at all.

Warning. Off work for a while. Prepare for more stupid questions.

You’re probably correctly recalling what you were told, but unfortunately, what you were told was wrong. Mass is mass, and doesn’t change with speed. It is true that, as an object’s speed approaches c, its energy increases without bound, but that energy does not manifest as mass.

The whole notion of “relativistic mass”, that depends on energy, is nothing but the result of some people trying to make the equations look more like the equations they were used to, but doing it in entirely the wrong way. Which is a shame, because it is possible to make the equations “look right” in a way that’s correct and just as simple.

Thanks for the info.
I was pondering how a photon can have more or less energy while retaining the same mass and speed. I know about the equation for it. Wavelength etc. But that seems more a description than an explanation. I always felt that relativistic mass scheme seemed a bit off. For the reasons I was asking about.

Maybe I can word a google search more accurately now.

It seems counter intuitive that the wave length of a lower energy photon is longer than a higher energy one. In actual practice a longer antenna captures the energy of a low frequency wave better. A short antenna captures shortwave energy better. What is contracting the wave length? It seems a more energetic photon should have effect that is wider, longer wave length.

That is why I was considering the relativistic mass idea. Some force contracting the energy inward. In some inverse way. Add energy, something increases to pull that energy field inward.

It might be more intuitive to think of high frequency as being high energy. Something changing a trillion times per second has more energy than something changing a billion times per second.

Photons themselves are fairly counter intuitive, so trying to use intuition to figure out how they “should” behave is not a good approach.

But try thinking of it this way. You’re traveling towards a wave emitter at some speed, observing waves hitting you with a certain energy pr. time and, with the right instruments, those waves consisting of photons.

Now speed up a little. The waves increase in frequency and in energy and that has to be true for the individual photons too.