How is energy converted into matter?

[Onceler]

I was wondering this because I was reading about matter into energy but has the opposite conversion been discovered yet?

 

[Mark R]

It is a well recognized phenomenon, and its discovery earned the Nobel Prize.

The simplest example is that of 'pair production'. A photon can convert into a particle/anti-particle pair - e.g. electron and positron, if the photon has sufficient energy to yield the mass of the particles. For reasons of conservation of momentum, this process can only occur if the photon hits an atomic nucleus (the light particles produced absorb a lot of energy, but virtually no momentum - something big and heavy, is needed to absorb a lot of momentum, but virtually no energy).

Pair production is an important consideration when calculating gamma ray penetration into substances - e.g. nuclear shield design, radiotherapy planning.

You also get less pure conversion of energy into matter in high energy collisions. In a particle accelerator, electrons/protons/nuclei are accelerated to very high speeds, giving them huge kinetic energy. They are then collided together head on, so that the kinetic energy must be removed - the result is that the kinetic energy is converted into showers of particles.

This is the aim of experiments like the Large Hadron Collider. By analysing the particles that appear from the debris of high-energy collisions, the scientists are looking to catalog the different types of particles, for use as confirmation for various physical theories. For example, the current 'standard model' of physics predicts the existance of a particle that causes the existance of mass - the, so called, 'Higgs Boson'. However, the existance of the Higgs remains uncofirmed. Scientists intend to run examine many collisions at many different energies, looking for Higgs particles being produced (or not).

 

[Baasha]

All the matter in the known universe is said to have been produced in the first 4 seconds after the Big Bang. This is because of the immense temperatures that were prevalent at the time; upwards of a trillion Kelvin. As soon as the universe cooled down, relatively speaking, energy to matter conversion was not possible and thus matter coalesced to form the subatomic particles etc.

 

[PowerEngineer]

Stars burn out or explode when they run out of fuel for fusion, which I understand to mean that stars only "burn" as long as the fusion process of combining lighter atoms into heavier ones also releases energy. This energy release comes from the fact that the lighter atoms that are being fused start with more mass than the resulting heavier atom (and other particle byproducts). If I remember correctly, there is energy released for fusion all the way up the periodic chart until you get to iron.

My understanding is that everything heavier the iron was formed through supernova explosions where the extreme energies released drove fusion reactions that required an input of energy to make them happen. I think this means that the end products of these fusion reactions actually weigh more than the atoms before being fused. That input energy is converted into the additional mass. (That's obviously true for the really heavy elements that release energy through fission.)

It's Carl Sagan's "star stuff".

 

[Biftheunderstudy]

Close. However, the heavier elements are not created through pair production. During a supernova loads of neutrons are produced which then smash into different elements making heavy isotopes. These isotopes are usually unstable so they start to decay through beta decay into a different element. The flux of neutrons is so high that elements can be built up to very high masses before they can decay and you get radioactive elements all the way up the periodic table. The competing processes here are, creatively named, the rapid and slow neutron capture processes.

As far as pair production goes, this is a well documented phenomenon. We can do it in the lab and in fact it's kind of how a PET scan works. Astrophysically, we see the characteristic radiation given off from pair annihilation all the time (411KeV?).

 

[crashtestdummy]

I was wondering this because I was reading about matter into energy but has the opposite conversion been discovered yet?

Mass IS energy. E=mc^2 doesn't say that energy and mass are interconvertable, it says that they are equivalent. Any change in energy of a system is a change in mass, and vice versa.

 

[C1]

Have you guys have gone overboard explaining this?

Isnt this what plants do with sunlight?
================
http://www.bbc.co.uk/news/science-environment-11711228

 

[Lemon law]

Have you guys have gone overboard explaining this?

Isnt this what plants do with sunlight?
================
http://www.bbc.co.uk/news/science-environment-11711228

--------------------------------------------------------------------------------------
In a word NO.

Photosythesis merely converts the energy of a photon into chemical energy by altering the energy states of electrons. Its a purely chemical reaction that does not involve the conversion of mass into energy or the conversion of mass into energy.

At no point in time in photosynthesis does the mass change in the before and after states.
So E=mcsquared does not apply in chemical reactions.

But going back to what I believe is the correct Power engineer position, Star Novas best show the conversion of energy into mass. And it should be noted that first generation stars
are only stage one in converting hydrogen and helium into heavier elements.

Once that stage one star goes Nova, only a few heavy elements are created, but as that blown away heavy elements form a part of a later second generation star, and that second generation star goes Nova, only then can still heavier elements be formed. I am pretty sure most of the really heavy radioactive elements take at least three star generations to form.

But when really massive stars can take as little as 75 million years to burn out and go Nova, in the 13.7 assumed billion years of the universe, who knows how many times a given atomic neculus has been through the star to Nova phase.

 

[Biftheunderstudy]

Again, you need to be careful here. Yes the majority of elements past iron were created in supernova, but their mass was not created from energy. They were built up through neutron capture during the extremely high neutron fluxes during this event. Strictly speaking, this is a nuclear reaction and mass is not exactly conserved, meaning there is some conversion of mass to energy going on but it is small compared to simply sticking neutrons onto an element then turning it into a proton.

Conversion of mass to energy and vice versa is usually called pair production and annihilation. This means that if I have a photon of 511keV, it can produce an electron and a positron which follows directly from E=mc^2 and to conservation of momentum (amongst other things). This happens all the time (they can even pop out of the vacuum spontaneously, so long as they give all the energy back). As I mentioned, this is kind of how PET scanners work. You send a positron in and look for the characteristic photons that are emitted when it annihilates (converts back to energy).

 

[sjwaste]

Wasn't there an article recently posted here about high energy lasers, reaching an upper limit where some of the photons were being converted to baryons/leptons (don't remember which, but probably electrons)?

Would that be the conversion of energy to mass, since photons are massless at rest? Or is that something different entirely?

 

[William Gaatjes]

It is a well recognized phenomenon, and its discovery earned the Nobel Prize.

The simplest example is that of 'pair production'. A photon can convert into a particle/anti-particle pair - e.g. electron and positron, if the photon has sufficient energy to yield the mass of the particles. For reasons of conservation of momentum, this process can only occur if the photon hits an atomic nucleus (the light particles produced absorb a lot of energy, but virtually no momentum - something big and heavy, is needed to absorb a lot of momentum, but virtually no energy).

Pair production is an important consideration when calculating gamma ray penetration into substances - e.g. nuclear shield design, radiotherapy planning.

You also get less pure conversion of energy into matter in high energy collisions. In a particle accelerator, electrons/protons/nuclei are accelerated to very high speeds, giving them huge kinetic energy. They are then collided together head on, so that the kinetic energy must be removed - the result is that the kinetic energy is converted into showers of particles.

This is the aim of experiments like the Large Hadron Collider. By analysing the particles that appear from the debris of high-energy collisions, the scientists are looking to catalog the different types of particles, for use as confirmation for various physical theories. For example, the current 'standard model' of physics predicts the existance of a particle that causes the existance of mass - the, so called, 'Higgs Boson'. However, the existance of the Higgs remains uncofirmed. Scientists intend to run examine many collisions at many different energies, looking for Higgs particles being produced (or not).

Well, that is something that always puzzled me. I always heard of the famous PET(Positron emission Tomography) scanner, the proof of antimatter.
I was always in the illusion that the device contained a sensor capable of detecting positrons.


But when i did some background reading about it, the device does not capture positrons, it captures high energy photons and converts these photons to image data.

This is how it works if i am not mistaking :
A radioactive isotope is added to the bloodstream of a patient.
That isotope emits ionizing radiation through beta decay, high energy photons. The current theory is that the beta decay consists of positrons that annihilate with electrons in the surrounding tissue. This causes high energy photons with for as far as i know, a short wavelength . These photons are absorbed by a material that converts these high energy photons into photons with a longer wavelength in the range IR to UV if i am not mistaking. Scintillation is the name for this process.
Then these lower energy emitted photons are captured by an high quality imaging sensor as for example a CCD. A computer starts calculating and presents a picture.

This i find interesting, the positron comes from the theory but is never captured or measured. Only high energy , short wavelength( yes i know both aspects of the photon are related) photons are released.



Another point is, i once predicted that there will be many higgs boson particles discovered. And more other particles will be "discovered" because of flawed models. If, this is not already the case waiting to be peer reviewed and will be presented in the media soon...

I expect this to come true. Intuition is a funny thing, when based on the history of physics...


Can you clarify this a bit for me to take away or reinforce my doubts about the standard model ?

I just love this article :

http://calteches.library.caltech.edu/51/02/CargoCult.pdf

 

[William Gaatjes]

Forgot to mention, the pdf is an article from Richard Feynman. Great read.

But as i am reading about the history of antimatter, i come across great names as Paul Dirac and Carl David Anderson. I also found some interesting reading about how antimatter was needed to solve the differences between relativity of Albert Einstein and the standard model of Niels Bohr and Werner Heisenberg.

I am not yet fully understanding it, but it seems that in the past (perhaps before Paul Dirac started calculating and postulating) the energy calculated to let an electron exist, was not available according to the standard model and relativity. That is where the idea of some form of incredibly powerful power source came from. The annihilation of antimatter with matter. That was the only way to make the calculation and the standard model work together with relativity. Carl David Anderson was the person who used a cloud chamber setup (with the possibility to create electric fields and magnetic fields)to detect cosmic ray particles from outer space and discovered particles that seemed to behave exactly like electrons but had a positive charge... This was then at the time seen as the proof of antimatter. Interesting read, but i am curious how that setup worked and if it was repeated today what would be discovered with modern technology ?


EDIT :
But i always wonder about one thing... One of the cosmic ray particles is a hydrogen atom without an electron also known as a proton. Same charge, opposite sign. I am sure that a proton because of having more mass then an electron responds different to an electrical field as when compared to an electron. Thus leaving a different trail in that cloud chamber. But i wonder, is it possible to give a proton a certain kind of start values , that it will mimic an electron in path behaviour but with an opposite charge ? Is that possible ?

 

[DrPizza]

So E=mcsquared does not apply in chemical reactions.

*sigh* YES, E=mc² DOES apply to all chemical reactions. It generally not considered by chemists, because the amount of mass gained/lost during chemical reactions is negligible. How much mass are we walking about, you might ask? Figure it out yourself. Here's the equation you need: E=mc²

 

[CycloWizard]

*sigh* YES, E=mc² DOES apply to all chemical reactions. It generally not considered by chemists, because the amount of mass gained/lost during chemical reactions is negligible. How much mass are we walking about, you might ask? Figure it out yourself. Here's the equation you need: E=mc²

This. The mass change is the amount of energy transferred divided by the speed of light squared. Since the speed of light is huge, the speed of light squared is even bigger. Thus, the amount of mass gained or lost during a reaction is not measurable until you transfer an insane amount of energy.

 

[Blitzvogel]

I would think of physical particles as energy itself, in a tangible form. It's this energy that gives the particles that make up an atom it's properties, photons, etc and in turn, everything else. Energy can be interpreted and transfered in numerous ways. I consider everything to be a form of energy, because it just is.

 

[shangshang]

I would like ask even the more basic question. What is energy? What is mass? I have never truly understood their definitions.

And have the scientists discovered the mechanism by which energy is converted to matter? (if "convert" is the appropriate word to use).

If a particle is accelerated to lightspeed, then would it become "purer" energy, i.e. it has more energy characteristics than particle characteritics? Umm.. what is energy anyway?

And what is the mechanism of conversion?

The concept of energy and matter is really a complex and abstract subject that I think only a handful of people past and present ever grasped it. But it's always fun to talk about it with the coffee buddies!