Water is to heavy

Ah, not exactly. Photons have no inherent mass. But put a lot of photons in a box, and that box will have a part of its mass due to the presence of those photons.

And once again, if it were a conversion, the equation would be:

E + m = constant

Please note that this is similar to the equation for conservation of energy when dealing with just kinetic and potential energy:

KE + PE = constant

But the energy/mass equation is not the above. It's:

E = m
(the c^2 is just a consequence of the units we use, and has no physical meaning)

So mass is not like potential energy. Mass is a measure of all of the energy in a system, both kinetic and potential.

 

That's funny because I started as a chem major and I was told that mass is conserved in chemical reactions. I asked for a reference, you haven't yet provided one.

-FUDie

 

Mass is not considered to be a conserved value in any interaction, not at a fundamental level. It is, of course, approximately conserved in chemical reactions because the reaction energies are small compared to the "rest mass energy" of the particles involved. But not exactly (by the calculations I listed above, the difference will be on the order of a 10^-8 difference...it probably won't vary by more than one or two orders of magnitude in either direction for any chemical reaction). I can look for a link, but I'm talking from a fairly extensive knowledge of basic physics.

 

Btw, found a couple of links:
http://www.newton.dep.anl.gov/askasci/chem03/chem03534.htm
http://www2.yk.psu.edu/~jhb3/cotw06.htm

Please note that while in the first link, the person states that there is no loss of mass in chemical reactions, if you read his first explaination, you may note that what he actually means is that the loss of mass is so small as to be negligible for the reactions involved.

One thing he misses, however, is that the equivalence of mass and energy is much more important in high-energy physics than it is in nuclear physics.

In nuclear physics, this equivalence is used as a method to calculate the energy output of a nuclear reaction: you take the mass of the components of the reaction, then of the individual resultants. Take the difference, and that's the amount of energy released in the reaction. In principle one could do a similar thing with chemical reactions, though it'd be much cheaper just to react the substances and find the result than to concoct an extremely careful experiment in measuring the mass difference.

In high-energy physics, however, this equivalence takes on a whole new meaning: physicists make use of the equivalence of mass and energy as a process for creating particles. Basically, the idea is this: it isn't mass that is conserved, but rather energy. Colliding a proton and an anti-proton at very high energies (today we're doing it in the range of 1000 times the mass-energy of the proton), and the resulting reaction can create basically anything that holds with all that is conserved for the particular force that mediates the interaction.

As a side comment, it turns out that all forces basically must conserve energy because all forces are independent of time. That is to say, no force of which we are aware changes its strength or properties as time passes. Mathematically, it turns out that this invariance in time translates to the conservation of energy in reactions involving this force.

 

Ok, I've thought about it some more and I guess I can see where you are coming from. Even in the fusion reaction I described (2 deuterium nuclei fusing to forum a helium nucleus), no matter is destroyed, yet mass is lost due to the energy released (mass of a helium nucleus is a little less than the mass of two deuterium nuclei).

Thanks for the explanation.

-FUDie

 

Yup, simple conservation laws. But bear in mind that this is also proposed to be an approximation.

Consider, if you will, that the early universe was just a hot soup, so hot that the ambient temperature was much, much higher than the rest mass energy of the particles we know and love today. This would mean that these particles would be popping in and out of existence all the time, but always in equal amounts of matter and anti-matter. This picture, which is all that the physics we currently "know" tells us, clearly doesn't describe our universe, which is dominated by matter, not an even mixture (note: if there was an equal mixture, but the anti-matter just contained in different galaxies today, then we would expect to see, every once in a while, a matter galaxy colliding with an anti-matter galaxy, causing a massive explosion and very distinctive energy signature....no such events have been seen).

So, at some high energy, the conservation law that today says that matter can't be created or destroyed (except in matter/anti-matter pairs) must have been violated. There are many ideas as to how this conservation law could be violated, but we have not yet seen any experimental evidence of the violation (though physicists are looking for it intently).

 

Weren't some experiments done measuring the effects of gravity on matter and anti-matter by dropping each through long holes drilled in ice in Greenland or something? I'm pretty sure the results showed small differences in the behavior between the two, but I have no idea if those results have been invalidated.

-FUDie

 

I think I've heard some rumors of such a thing, but it's just so incredibly hard to do that experiment carefully that I don't think we can really say there has yet been a signal of any difference.

On the surface, though, I would tend to believe that there shouldn't be any difference. As far as I know, gravity couples purely to momentum-energy, and as such even if a unified theory of gravity and the other forces predicts some TCP violation (difference between reactions with matter/anti-matter), I wouldn't expect to see any on the macro scale. This is more just intuition, though, and I don't really know if any TCP-violating theories actually predict any difference in the force of gravity on anti-matter as opposed to matter.

 

From the original post...

This is a chemical question, not a physical one. The mass differences you get from creating water from molecular oxygen and hydrogen are so small that you would be laughed at by your peers for even considering it. So plitting up water to its molecular compenents is ruled out.

Another solution is to use an isotope of oxygen that's lighter than O-16. However, the only common isotopes that are stable are O-16,17 and 18. O15 and O14 have half-lives of 2 minutes and a minute ten respectively. Lower isotopes of oxygen are even more unstable. That's kind of an unusable state. As speciation might occur due to the decay and you may not end up with water. Not to mention that radioactivity tha you'd have to contain.

Density wise, you can heat up the water sample just below the boiling point. The density will decrease (though I don't know by how much) and you sample of water will get lighter. This assumes though an poen system and you're only concerned with a cubic yard of water. Though the savings in terms of mass will still be negligable. To make things clear, water at 80 centigrade should be light than water at 25 centigrade at the same volume, hotter matter generally are less dense so are less pact. Ignore the fact that ice is less dense than liquid water as that has to do with te crystal structure of water.

So there is no realistic way to lighten up water.

In terms of replacing water in our bodies for a substitute, well... you'd die if you tried. Our bodies evolved in such a way that the normal biological function of our body rely on the chemical properties of water. Namely hydrogen bonding. So unless you can account for everything that water does in our body it would take a gargantuan effort to find a substitute that won't kill us.

 

Short answer - can't be done to lighten water. You'd really just need a storage device that takes anything and seperates it from the gravitational field surrounding it. Big problem - if it can be done you be kinda famous instantly.

On energy and matter equivalence - Chanloth is basically correct in his understanding. Think of it as you have something (Baryons or Leptons) that can manifest its properties in a number of ways. It is one inherent thing - the manifestation or interaction of this thing can be a form energy at work (force), curvature of spacetime - gravity or physical representation - matter. They are all just different faces of a deeper underlying reality. Energy and matter are just two sides of the one coin - they are not just two transferable things that are deeply connected - they are equivalent representations of one deeper thing.