Why cant radiation be turned back into matter?

[humility]

The heat death of the universe says that all energy is eventually lost in the form of radiation. But why cant radiation by gathered up and turned back into matter or turned into the energy needed to turn it back into matter? If its just a matter of ineffeciency then that doesnt sound like an absolute problem. Maybe eventually the solar system could be put into a box and the sun refed its own released energy to keep it from ever going red giant. And one day put the whole universe in a box.

[Delta1212]

That would be a bit like trying to use a battery to recharge itself. The energy has to come from somewhere.

[humility]

But thats because the energy escapes. If you took a full battery, hooked it up to an empty battery, and assume 100% effeciency. Hou would have two half full batteries.

 

And in this case the universe of radiation is the full battery and the matter is the empty battery. So you could turn half that radiation into matter. And that matter just turns back into radiation so you can repeat the process.

[Country Boy]

Theoretically, energy can be "turned back into matter". The "heat death" argument simply says that can't happen naturally. The total entropy in the universe increases and that can be reversed only by an intelligent being acting on it.

[humility]

Good, problem solved.

[Delta1212]

Theoretically, energy can be "turned back into matter". The "heat death" argument simply says that can't happen naturally. The total entropy in the universe increases and that can be reversed only by an intelligent being acting on it.

This is not correct. Intelligent beings cannot produce perpetual motion machines. Once energy has been used to do work, it is no longer available to do further work. The heat death of the universe is the point at which the universe finds itself in equilibrium, and if that is the case there is no longer any energy available to do work.

[Bender]

But thats because the energy escapes. If you took a full battery, hooked it up to an empty battery, and assume 100% effeciency. Hou would have two half full batteries.

This says it all really. If you have two half full batteries and put a light bulb between them, the light wouldn't go on, because the current wouldn't flow.

[imatfaal]

Sorry Guys are you all forgetting all the green stuff on our planet. That green stuff takes energy in the form of radiation and uses it to make complex molecules out of a selection of less complex molecules.

 

It is long wavelength - ie very cold - radiation that we cannot do much with; although Blackholes will be converting it to mass (or whatever is inside a blackhole) for many many times the current lifetime of the universe yet to come

[DrKrettin]

Sorry Guys are you all forgetting all the green stuff on our planet. That green stuff takes energy in the form of radiation and uses it to make complex molecules out of a selection of less complex molecules.

 

 

 

But surely in this process, energy is conserved without any change in actual mass? Radiation is not converted into mass in the relativistic sense, is it? You've got me worried.

[Delta1212]

Sorry Guys are you all forgetting all the green stuff on our planet. That green stuff takes energy in the form of radiation and uses it to make complex molecules out of a selection of less complex molecules.

 

It is long wavelength - ie very cold - radiation that we cannot do much with; although Blackholes will be converting it to mass (or whatever is inside a blackhole) for many many times the current lifetime of the universe yet to come

None of which makes the heat death of the universe reversible, though.

[Bender]

 

But surely in this process, energy is conserved without any change in actual mass? Radiation is not converted into mass in the relativistic sense, is it? You've got me worried.

It is, in fact, turned into mass. A sugar molecule is a tiny bit heavier than the CO2 and H2O it was made from. The difference is too small to be measured, though, because of the c² in E=mc²

 

Of course, it is not really turned into mass, because it has always had mass. Mass and energy are the same thing.

[StringJunky]

Can't two-photon physics produce an electron-positron pair; matter?

 

 

The photon's energy is converted to particle's mass through Einstein's equation, E=mc2; where E is energy, m is mass and c is the speed of light. The photon must have higher energy than the sum of the rest mass energies of an electron and positron (2 × 0.511 MeV = 1.022 MeV) for the production to occur....

https://en.wikipedia.org/wiki/Pair_production

[Janus]

There is pair production, where a pair of photons can combine to form a pair of electrons. However this requires photons of very high energy and frequency, you can't just combine a bunch of lower energy photons and pull off the same trick.

 

Supernovae can convert energy to matter in the sense that they create heavy elements that require a net input of energy to create. This includes fissionable elements which we can use to go the other way again.

However, this again requires an extreme concentration of energy, and that energy originated in a fusion explosion that converted mass to energy. In the end you have a net loss of mass when you compare the total matter used up in the explosion vs. the new elements created.

 

The problem is that any process for converting energy to matter needs a high energy density and in the end takes more energy than the energy equivalent of the mass you get out.

[DrKrettin]

It is, in fact, turned into mass. A sugar molecule is a tiny bit heavier than the CO2 and H2O it was made from. The difference is too small to be measured, though, because of the c² in E=mc²

 

Of course, it is not really turned into mass, because it has always had mass. Mass and energy are the same thing.

 

Yes, I know that, but I'm amazed that the mass of a sugar molecule is larger than the sum of the masses of the CO2 and H2O components. I had just assumed that the sugar is in a higher energy state with no increased mass. If that is the case, why are there headlines like this one? It makes no sense spending 80 years trying to achieve something when it happens all the time anyway. I'm rather confused - can somebody explain?

Edited April 24, 2017 by DrKrettin

[CharonY]

It is, in fact, turned into mass. A sugar molecule is a tiny bit heavier than the CO2 and H2O it was made from. The difference is too small to be measured, though, because of the c² in E=mc²

 

Of course, it is not really turned into mass, because it has always had mass. Mass and energy are the same thing.

 

Actually, the light reaction does not yield sugar. Rather, it uses the light energy to liberate electrons to move through an electron transport chain that powers a proton pump. That proton motive force is used to form ATP at a ATP synthetase. The ATP (as well as formed NADPH) are then used to fuel CO2 fixation in a totally independent chemical pathway (Calvin cycle).

Edited April 24, 2017 by CharonY

[swansont]

 

Yes, I know that, but I'm amazed that the mass of a sugar molecule is larger than the sum of the masses of the CO2 and H2O components. I had just assumed that the sugar is in a higher energy state with no increased mass. If that is the case, why are there headlines like this one? It makes no sense spending 80 years trying to achieve something when it happens all the time anyway. I'm rather confused - can somebody explain?

 

 

Pair production generally happens near a massive particle; this is required to conserve momentum. A single photon turning into a particle/antiparticle pair would not do this (for the same reason, annihilating particles form two or more photons, not one). But it could happen with two counter-propagating photons, which is what they are going to try.

[DrKrettin]

 

Actually, the light reaction does not yield sugar. Rather, it uses the light energy to liberate electrons to move through an electron transport chain that powers a proton pump. That proton motive force is used to form ATP at a ATP synthetase. The ATP (as well as formed NADPH) are then used to fuel CO2 fixation in a totally independent chemical pathway (Calvin cycle).

 

OK - let me try and put my question more generally. Suppose you could isolate a plant and its environment including all gas, water and nutrients which the plant will take up whilst growing. Suppose you could weigh all the components when the plant is a seedling and weigh the fully grown plant. The only difference would be the sunlight it receives. Would the weight of the sum total of the original material be the same as the weight of the finished plant, or would there be an increase in weight directly attributable to the energy of the photons in sunlight converted into mass as mc2 ? I don't know how else to ask what is really a very simple question.

[swansont]

 

OK - let me try and put my question more generally. Suppose you could isolate a plant and its environment including all gas, water and nutrients which the plant will take up whilst growing. Suppose you could weigh all the components when the plant is a seedling and weigh the fully grown plant. The only difference would be the sunlight it receives. Would the weight of the sum total of the original material be the same as the weight of the finished plant, or would there be an increase in weight directly attributable to the energy of the photons in sunlight converted into mass as mc2 ? I don't know how else to ask what is really a very simple question.

 

 

 

Yes, the mass will increase if energy has been absorbed. This has been measured with an isotope of Fe. An excited state has more mass than the ground state.

 

http://blogs.scienceforums.net/swansont/archives/278

 

In this case, the mass difference was 402 keV's worth, since it's a nuclear excitation. In a simple chemistry interaction, the energy difference is typically 4 or 5 orders of magnitude less.

[Bender]

Actually, the light reaction does not yield sugar. Rather, it uses the light energy to liberate electrons to move through an electron transport chain that powers a proton pump. That proton motive force is used to form ATP at a ATP synthetase. The ATP (as well as formed NADPH) are then used to fuel CO2 fixation in a totally independent chemical pathway (Calvin cycle).

And a wind turbine does not generate electricity, it only makes the shaft turn...

 

 

OK - let me try and put my question more generally. Suppose you could isolate a plant and its environment including all gas, water and nutrients which the plant will take up whilst growing. Suppose you could weigh all the components when the plant is a seedling and weigh the fully grown plant. The only difference would be the sunlight it receives. Would the weight of the sum total of the original material be the same as the weight of the finished plant, or would there be an increase in weight directly attributable to the energy of the photons in sunlight converted into mass as mc2 ? I don't know how else to ask what is really a very simple question.

The difference would probably be too small to reliably measure. Suppose the plant consists almost entirely of oil, with a chemical energy content of 37000 kJ/kg.

m = E/c² = 37e6/9e16 = 4e-10 kg

So it would be 0.4 µg/kg. Pretty difficult to measure in the setup you propose. In practice the difference would be much smaller, because plants don't consist entirely of oil.

[DrKrettin]

The difference would probably be too small to reliably measure. Suppose the plant consists almost entirely of oil, with a chemical energy content of 37000 kJ/kg.

m = E/c² = 37e6/9e16 = 4e-10 kg

So it would be 0.4 µg/kg. Pretty difficult to measure in the setup you propose. In practice the difference would be much smaller, because plants don't consist entirely of oil.

 

I'm interested in the principle, even if it's not measurable. I'm gobsmacked, to be honest.

[CharonY]

And a wind turbine does not generate electricity, it only makes the shaft turn...

 

The difference would probably be too small to reliably measure. Suppose the plant consists almost entirely of oil, with a chemical energy content of 37000 kJ/kg.

m = E/c² = 37e6/9e16 = 4e-10 kg

So it would be 0.4 µg/kg. Pretty difficult to measure in the setup you propose. In practice the difference would be much smaller, because plants don't consist entirely of oil.

 

Identifying how the system works is relevant in figuring out net gains and losses. For example one has to assume that quite a bit of energy would be lost at every step of the process. And that is precisely the importance of seeing the reactions as uncoupled. If the initial excitation was all that results in a fixed carbon, it would likely add to the mass.

However, as it basically only excites the photosystem, which then utilizes that energy to initiates several transfer reactions (which are associated with a bit of energy loss along the gradient) it would probably add very little, if at all to the net mass of the system. But to be certain someone with more knowledge in that matter would have to take a look at that. Clearly the mass-energy equivalence is insufficient to fully explain the system.

Edited April 24, 2017 by CharonY

[Bender]

 

Identifying how the system works is relevant in figuring out net gains and losses. For example one has to assume that quite a bit of energy would be lost at every step of the process. And that is precisely the importance of seeing the reactions as uncoupled. If the initial excitation was all that results in a fixed carbon, it would likely add to the mass.

However, as it basically only excites the photosystem, which then utilizes that energy to initiates several transfer reactions (which are associated with a bit of energy loss along the gradient) it would probably add very little, if at all to the net mass of the system. But to be certain someone with more knowledge in that matter would have to take a look at that. Clearly the mass-energy equivalence is insufficient to fully explain the system.

Why is that clear? Why wouldn't it be sufficient?

Sure energy gets shifted about in complicated biochemical ways. The chemical energy content of a molecule is what it is, and it does not matter how it got there and what processes were involved.

 

Likewise, a charged battery is a couple of nanograms heavier than an empty battery, and heating something increases its mass by an unmeasurably small amount.

[humility]

So if we put the universe in a box with green algae coating the walls that has been engineered to absorb long radiation as well as short, tyehe plants will recapture all the radiation and the universe is saved?

Edited April 24, 2017 by humility

[Delta1212]

So if we put the universe in a box with green algae coating the walls that has been engineered to absorb long radiation as well as short, tyehe plants will recapture all the radiation and the universe is saved?

No. The process of capturing that energy increases the entropy of the system. Life is not magic, it is just complex. There will always be less and less useable energy in the universe. There is nothing we can do to change that fact.

[CharonY]

Why is that clear? Why wouldn't it be sufficient?

Sure energy gets shifted about in complicated biochemical ways. The chemical energy content of a molecule is what it is, and it does not matter how it got there and what processes were involved.

 

Likewise, a charged battery is a couple of nanograms heavier than an empty battery, and heating something increases its mass by an unmeasurably small amount.

 

I think it would matter when you measure mass and what the efficiency of the processes involved are. Immediately after excitation (and ignoring that there are several capturing events) one would assume a mass increase of the photosystem as outlined by others above. However, that energy is used to e.g. split water and initiate electron transfer and excess energy is lost as heat and/or fluorescence (i.e. radiation). So measuring the total mass of the system later in the process should yield a different mass as one would expect from the initial absorbed energy alone.