Relativistic mass term (split from, "Time dilation, observer vs traveler. Confusion!")

[puppypower]

Try to avoid thinking "real universe".

 

That'll lead to thinking there's absolute time and absolute distance. It's all relative.

 

The conservation of energy implies an absolute reference in the universe. In SR, there is a relativistic mass term, which is connected to the energy balance. Space and time, apart from an energy balance, may appear relative. The relativistic mass term is often discounted and never used as part of relative reference because this is the thorn on the claw of the relative reference assumption.

 

As an example, say we have two space ships in outer space, one with mass M and other other with mass 2M. While all the crews were sleeping, we gave one of the two ships velocity V using energy E. When they awake they see relative velocity V between them but can't tell who is who. With space-time alone motion may appear relative. However, an energy balance will tell us which of the two has tangible motion, since E energy impacts M and 2M differently.

 

The main problem with relative reference is it can violate energy conservation, by unknowingly adding or subtracting energy to or from the universe. The idea of no center of the universe means we don't know the universal energy. Say we didn't know whether ship M or ship 2M had the motion, since nobody tells us the energy balance. Instead we say this is relative and agreed upon M as the moving reference, We have just underestimated the energy by 50%. This of itself is not bad, until we we see an anomaly in space and need to postulate extra mystery energy to close the energy balance. If we had picked the proper reference nothing new is needed.

 

Since we know 2M is in energy based motion, its space-time and relativistic mass effects are tangible since they are based by real energy. If this crew met the other crew they would all be younger.

Edited October 21, 2015 by puppypower

[swansont]

The conservation of energy implies an absolute reference in the universe.

No. It implies there is a symmetry under time translation.

https://en.wikipedia.org/wiki/Noether%27s_theorem#Example_1:_Conservation_of_energy

 

In SR, there is a relativistic mass term, which is connected to the energy balance. Space and time, apart from an energy balance, may appear relative. The relativistic mass term is often discounted and never used as part of relative reference because this is the thorn on the claw of the relative reference assumption.

Relativistic mass is just a proxy for total energy. Pretty sure people use total energy in calculations. A lot. Every time they apply conservation of energy, even.

 

As an example, say we have two space ships in outer space, one with mass M and other other with mass 2M. While all the crews were sleeping, we gave one of the two ships velocity V using energy E. When they awake they see relative velocity V between them but can't tell who is who. With space-time alone motion may appear relative. However, an energy balance will tell us which of the two has tangible motion, since E energy impacts M and 2M differently.

Each would see the other as having more energy, and thus more relativistic mass. (They would see their own ship as unchanged) But gamma would be the same for each ship, as seen by the other, so if gamma = 2 then each mass doubles. The ratio stays the same.

 

IOw, if you give each ship energy E, they will not have the same velocity. The velocity is then not relative. But how can one ship move away from the other at v1, while the other moves away from the first at v2, unless v1 and v1 are equal?

 

The main problem with relative reference is it can violate energy conservation, by unknowingly adding or subtracting energy to or from the universe.

It does no such thing. Conservation of energy applies within a frame of reference. Energy is not invariant — the total energy in one frame will not be equal to the total energy in another frame. That's not just a feature of Einstein's theory — it's true in Galilean systems (i.e. classical physics) as well. Energy is relative. Since it can depend on speed, it has to be.

 

[hypervalent_iodine]

!

Moderator Note

puppypower,

 

Please remember that we do not allow members to drive threads off topic. Keep to the discussion outlined by the OP and if the thread is housed in the main science are of the forum, keep your posts in the realms of mainstream science only.

 

FTR, I have split this post and the subsequent reply from here. Do not respond to this note in-thread.