In addition to what Bandersnatch said, be advised that this is a complete mis-statement of the law, which is actually called the Law of Conservation of Mass and says that MASS cannot be created or destroyed in a closed system. Matter gets destroyed all the time but the destruction results in no loss of mass since the radiation portion has energy which is equivlent to mass in this context.... as per the Law of Conservation of Matter, matter can neither be CREATED, nor be destroyed...
Sure....So, shall we conclude by saying that Universe existed earlier also and would tend to exist forever?
Mass isn't a conserved quantity, though. It's created and destroyed all the time in high-energy reactions and nuclear decays.In addition to what Bandersnatch said, be advised that this is a complete mis-statement of the law, which is actually called the Law of Conservation of Mass and says that MASS cannot be created or destroyed in a closed system. Matter gets destroyed all the time but the destruction results in no loss of mass since the radiation portion has energy which is equivlent to mass in this context.
[to Priyank]...You seem open to the idea. So you might enjoy the Cai&Wilson-Ewing paper. Just read the non-technical parts, if you like---the beginning introduction and the conclusions at the end.
If you google "LambdaCDM bounce" the first hit you get is
http://arxiv-web3.library.cornell.edu/abs/1412.2914v2
they just uploaded an expanded version two days ago, on 28 Jan. I wonder if it is the same as what you get when you click on the standard link for their december 2014 paper:
http://arxiv.org/abs/1412.2914
The total mass-energy in a closed system is conserved. When the mass is destroyed, the radiant energy counts into the sum, right?Mass isn't a conserved quantity, though. It's created and destroyed all the time in high-energy reactions and nuclear decays.
No. Definitely not. A nuclear decay will typically lower the mass-energy of a system, while many high-energy collisions will add to the mass-energy. In these systems, the mass-energy is converted to/from kinetic energy.The total mass-energy in a closed system is conserved. When the mass is destroyed, the radiant energy counts into the sum, right?
OK, I had this wrong. Thanks for straightening me out.No. Definitely not. A nuclear decay will typically lower the mass-energy of a system, while many high-energy collisions will add to the mass-energy. In these systems, the mass-energy is converted to/from kinetic energy.
It is possible to say that energy is conserved locally. What this means is that it's possible to use equations such that the change in energy in an infinitesimally-small region is equal to the energy flowing into that region. The caveat here is that this only works reliably for flat space-time, but since you can always use coordinates where the local space-time is flat, this is always possible to do locally. This is why we generally consider energy to be conserved in reactions on the Earth: the space-time curvature is small, and regardless we typically deal with reactions that are tiny in size. Furthermore, we can write down a gravitational potential energy which allows us to account for the energy changes induced by gravity (this isn't always possible).
But when you've got a curved space-time, much of the time it's impossible to say that energy is conserved across the entire system, regardless of whether it's closed or not. As Bandersnatch pointed out, global energy conservation just doesn't work, because there isn't a unique definition of total energy for a curved space-time.
Yes, this is what I was talking about.I think you are using two different definitions of "mass-energy".
The total energy stored in particle masses is not conserved, but the total energy in a closed system is, and seen as "closed box" the mass you would assign to this system in its rest frame stays the same even with nuclear decays. This is not an exotic model - we do this all the time when we talk about the mass of protons which is mainly QCD binding energy.