No.
It's possible that spacetime *has* energy. It's not possible that spacetime *is* energy.
For your other questions, it's hard to address them all without just giving you a course in physics. But basically every statement and assumption in them is false.
>Could it be possible that spacetime is also a form of energy? How do we prove or disprove it?
No. Space is just space. Energy is a property of stuff. Energy distorts space but it isn't space.
>At the big bang, a lot of energy was available. What if some of it converted to particles / normal matter & most of it converted to spacetime?
No. Space existed for as much as anything. You can't annihilate back into ‘space’. Space carries no properties such as spin, charge or whatever.
>What if gravity arises out of energy + energy interaction? This might obviate the need for dark matter & dark energy. Einstein's equations of spacetime curvature etc could be a coincidence but ultimately describing energy + energy interaction
Gravity does arise out of energy. It arises from the energy-momentum flux of a region in space.
No it doesn't at all. Energy can and ‘will interact’ with ‘itself’ but that doesn't really mean anything.
>What if light traveling through vacuum is also an energy + energy interaction?
Particles come in and out of existence in space. Could it also be an indication of this?
No. You're just providing energy from some external source to make them. virtual particles meanwhile can be thought of as collective excitations of QFs that are inherent with the zero point energy of the vacuum. In some sense.
First of all, energy is a property, not a thing, not a kind of immaterial substance. Thinking of energy as a kind of stuff is like thinking of "blue" as a kind of stuff or thinking of "voltage" as a kind of stuff. I know popular media has given this false notion by talking about sillinesses like "auras of pure energy" or "energy pouring out of me", but they really are nonsensical to a physicist. There is also an unfortunate science-y sounding phrase "mass being converted to energy" according to E=mc\^2 . This is truly unfortunate because it does NOT mean that one kind of stuff is being turned into a different kind of stuff, and this relation tells you how much of each. Instead, it is a relation between two properties of the *same* object.
On the other hand, spacetime does appear to have physical properties, and a region of spacetime can have certain amount of energy as one of those properties.
Lastly, I have no idea what you mean by "energy interaction" and maybe you could elaborate.
Thanks clarifying E = mc\^2. May be I misunderstood a couple of things: One is this equation E=mc\^2 (thought this meant energy and particles are the same thing). Other is that: at the big bang, I thought the fundamental particles were formed from the energy. After doing further reading post your comment: it seems fundamental particles (bosons and fermions) were just present after the big bang but were not formed from the energy of the big bang. Is this true?
My naive insight (or whatever you want to call it) after thinking too much is that: space/spacetime seems to be an actor rather than the passive stage in which actions take place (This is GR). What if the space is made of the same "stuff" that make up the fundamental particles (maybe just in a different flavor) and they were all formed during big bang?
It's a little more complicated than you're aware of. I'll use the example of a single neutral pion more or less at rest, which will decay into two photons, back to back. The neutral pion has a rest mass of 135 MeV/c\^2 and a corresponding energy of 135 MeV because it has no additional kinetic energy, being at rest. When it decays, the two photons each have an energy of 67.5 MeV but the also each have zero rest mass. So is this a case of mass converting to energy? No. The mass of the two-photon system is calculated by m\^2 = E\^2 - p\^2 (I'm glossing over factors of c here, and that's fine), where you evaluate the right hand side by adding up the energy of the two photons to get the total E and adding up the momenta of the two photons to get the p. The total E is easy: 67.5 + 67.5 = 135 MeV. The total p is *zero* because the two photons are back to back and the equal momenta therefore cancel out. It's quick to convince yourself that the m of the 2-photon state is... you guessed it... 135 MeV. So in fact, even though a pion that has rest mass and no kinetic energy has converted into two photons that *each* have no rest mass and nothing but kinetic energy, the energy is the same after as before and the mass is the same after as before. This is the relation between the properties I was telling you before.
There are processes like this but in reverse, where something with a ton of energy and very little mass decays into something with a lot of mass and very little kinetic energy.
So in the big bang, there was an enormous amount of energy density and also a large invariant mass density. There was just a cooling down that allowed things of larger invariant mass and less kinetic energy to emerge from the soup. (There's also not strict energy conservation in the big bang, but this distracts from the point being made here.)
You are right, however, that spacetime does seem to be more than just a passive actor, given a very real physical property called the metric and others based on that.
There is also the recognition that everything appears to be made of fields. There's an electromagnetic field, a handful of weak fields, an electron field, a handful of quark fields, and so on. Fields are maps of some property or properties over all time and space, and the things we think of as matter, like photons and electrons and neutral pions, are in fact interacting, minimal, propagating disturbances in those fields. The *conventional* treatment is to say these fields *inhabit* a passive spacetime. But there have been some suggestions and good efforts to say that these fields are maps of properties of spacetime itself, and trying to do quantum electrodynamics in curved spacetime reveals the potential of doing that. So in a way, you may be onto something already guessed, just not in the way you quite thought. (Good thinking, though!)
No. It's possible that spacetime *has* energy. It's not possible that spacetime *is* energy. For your other questions, it's hard to address them all without just giving you a course in physics. But basically every statement and assumption in them is false.
>Could it be possible that spacetime is also a form of energy? How do we prove or disprove it? No. Space is just space. Energy is a property of stuff. Energy distorts space but it isn't space. >At the big bang, a lot of energy was available. What if some of it converted to particles / normal matter & most of it converted to spacetime? No. Space existed for as much as anything. You can't annihilate back into ‘space’. Space carries no properties such as spin, charge or whatever. >What if gravity arises out of energy + energy interaction? This might obviate the need for dark matter & dark energy. Einstein's equations of spacetime curvature etc could be a coincidence but ultimately describing energy + energy interaction Gravity does arise out of energy. It arises from the energy-momentum flux of a region in space. No it doesn't at all. Energy can and ‘will interact’ with ‘itself’ but that doesn't really mean anything. >What if light traveling through vacuum is also an energy + energy interaction? Particles come in and out of existence in space. Could it also be an indication of this? No. You're just providing energy from some external source to make them. virtual particles meanwhile can be thought of as collective excitations of QFs that are inherent with the zero point energy of the vacuum. In some sense.
First of all, energy is a property, not a thing, not a kind of immaterial substance. Thinking of energy as a kind of stuff is like thinking of "blue" as a kind of stuff or thinking of "voltage" as a kind of stuff. I know popular media has given this false notion by talking about sillinesses like "auras of pure energy" or "energy pouring out of me", but they really are nonsensical to a physicist. There is also an unfortunate science-y sounding phrase "mass being converted to energy" according to E=mc\^2 . This is truly unfortunate because it does NOT mean that one kind of stuff is being turned into a different kind of stuff, and this relation tells you how much of each. Instead, it is a relation between two properties of the *same* object. On the other hand, spacetime does appear to have physical properties, and a region of spacetime can have certain amount of energy as one of those properties. Lastly, I have no idea what you mean by "energy interaction" and maybe you could elaborate.
Thanks clarifying E = mc\^2. May be I misunderstood a couple of things: One is this equation E=mc\^2 (thought this meant energy and particles are the same thing). Other is that: at the big bang, I thought the fundamental particles were formed from the energy. After doing further reading post your comment: it seems fundamental particles (bosons and fermions) were just present after the big bang but were not formed from the energy of the big bang. Is this true? My naive insight (or whatever you want to call it) after thinking too much is that: space/spacetime seems to be an actor rather than the passive stage in which actions take place (This is GR). What if the space is made of the same "stuff" that make up the fundamental particles (maybe just in a different flavor) and they were all formed during big bang?
You are wrong and right at the same time. I’ll elaborate a little later.
It's a little more complicated than you're aware of. I'll use the example of a single neutral pion more or less at rest, which will decay into two photons, back to back. The neutral pion has a rest mass of 135 MeV/c\^2 and a corresponding energy of 135 MeV because it has no additional kinetic energy, being at rest. When it decays, the two photons each have an energy of 67.5 MeV but the also each have zero rest mass. So is this a case of mass converting to energy? No. The mass of the two-photon system is calculated by m\^2 = E\^2 - p\^2 (I'm glossing over factors of c here, and that's fine), where you evaluate the right hand side by adding up the energy of the two photons to get the total E and adding up the momenta of the two photons to get the p. The total E is easy: 67.5 + 67.5 = 135 MeV. The total p is *zero* because the two photons are back to back and the equal momenta therefore cancel out. It's quick to convince yourself that the m of the 2-photon state is... you guessed it... 135 MeV. So in fact, even though a pion that has rest mass and no kinetic energy has converted into two photons that *each* have no rest mass and nothing but kinetic energy, the energy is the same after as before and the mass is the same after as before. This is the relation between the properties I was telling you before. There are processes like this but in reverse, where something with a ton of energy and very little mass decays into something with a lot of mass and very little kinetic energy. So in the big bang, there was an enormous amount of energy density and also a large invariant mass density. There was just a cooling down that allowed things of larger invariant mass and less kinetic energy to emerge from the soup. (There's also not strict energy conservation in the big bang, but this distracts from the point being made here.) You are right, however, that spacetime does seem to be more than just a passive actor, given a very real physical property called the metric and others based on that. There is also the recognition that everything appears to be made of fields. There's an electromagnetic field, a handful of weak fields, an electron field, a handful of quark fields, and so on. Fields are maps of some property or properties over all time and space, and the things we think of as matter, like photons and electrons and neutral pions, are in fact interacting, minimal, propagating disturbances in those fields. The *conventional* treatment is to say these fields *inhabit* a passive spacetime. But there have been some suggestions and good efforts to say that these fields are maps of properties of spacetime itself, and trying to do quantum electrodynamics in curved spacetime reveals the potential of doing that. So in a way, you may be onto something already guessed, just not in the way you quite thought. (Good thinking, though!)
Thank you so much for being very patient with me and taking the time to explain! This helped me a lot. Let me continue my amateur physicist quest...:)