Where does energy come from, ultimately?

Pachomius · (#1)

Read this account of where energy comes from ultimately:

Quote:

Where does energy come from? Where does energy go?

[ Bolding from Pachomius ]

Energy can be found in many things and takes many forms. There is potential energy in objects at rest that will make them move if resistance is removed. There is kinetic energy in objects that are moving. The molecules making up all matter contains a huge amount of energy, as Einstein's E = mc^2 pointed out to us. Energy can also travel in the form of electromagnetic waves, such as heat, light, radio, and gamma rays. Your body is using metabolic energy from your last meal as you read this. Energy is constantly flowing and changing form. If you take your metabolic energy and rub your hands together, you have made metabolic energy into mechanical energy. Your hands will heat up. That is some of the mechanical energy turning into heat energy.

So energy can change form, but where did that energy ultimately come from? Let's trace back a chain of events. A bicycle is rolling down the hill, transferring potential energy into kinetic (movement) energy. The bicycle got its potential energy (energy due to position related to gravity) by the rider using metabolic energy to move the pedals. The pedals used mechanical energy to move the chain, which moved the wheels. The rider's metabolic energy came from chemical energy that was stored in the molecules of the food she ate. That chemical energy entered the animal whose meat she ate by the animal digesting a plant and breaking the bonds in its molecules. The plant made the molecules by using light energy from the Sun. The Sun's light energy came from electrons in its atoms lowering energy states, and releasing energy. The energy in the atoms came from the nuclear reactions in the heart of the Sun. What started the nuclear reactions? Physicists think the Big Bang did.

http://www.qrg.northwestern.edu/proj...om-and-go.html

What do you guys here think, has the author given the ultimate explanation for where energy come from?

Pachomius

bowmore · (#2)

Quote:

Originally Posted by Pachomius

What do you guys here think, has the author given the ultimate explanation for where energy come from?

The first law of thermodynamics, an expression of the principle of conservation of energy, states that energy can be transformed (changed from one form to another), but cannot be created or destroyed. (wiki)

So energy has simply always existed.

piesquared · (#3)

Things to note:

1.) When we say "law" we don't necessarily mean that it is absolutely inviolable. Consider Netwon's 2nd law, which relativity and quantum mechanics later proved to be only a valid approximation of the truth at medium size and speed. Laws seem valid for our experiences so far... but if there were ever a situation where exceptions would take place, it'd be the big bang.
2.) Matter is a form of energy (E=mc^2).
3.) The big bang was either the start of time and space, or at the least wiped out any possibility of ever seeing what happened before.

And so the answer is simple - all the energy was present (in one form or another) at the big bang. Asking what happened before is not a valid question, because time effectively started then. There can be no causal relationship between anything after the big bang and anything before it - if indeed "before" has an any meaning in this context.

Alternatively, the "net" energy of the universe may be zero. It may be that at some point the universe will stop expanding and instead contract back to a singularity. Singularity to singularity - no net change, no net energy, no problem.

Finally, we at the big bang relativity and quantum mechanics collide. That's why we can't even retrace our steps all the way back to the big bang - relativity and quantum mechanics don't work together, but at that point they had to. This tells us that one or both of them requires a change of the same magnitude that each modified Netwon's laws. Since we don't know what the final laws will be, we can't apply them and figure out what exactly happened at the big bang. In short: we don't know, yet.

(Please note that while there's something missing from relativity and quantum mechanics, they are still both good approximations of the truth for big/fast things and small/slow things, respectively - in the same way that Netwon's laws are good approximations of the truth for medium size/speed things.)

Thought Criminal · (#4)

Quote:

Originally Posted by bowmore

The first law of thermodynamics, an expression of the principle of conservation of energy, states that energy can be transformed (changed from one form to another), but cannot be created or destroyed. (wiki)

So energy has simply always existed.

If by "always", you mean "all time", then I can't argue. There's no "before" the universe.

bowmore · (#5)

Quote:

Originally Posted by Thought Criminal

If by "always", you mean "all time", then I can't argue. There's no "before" the universe.

What else then "at every point in time" could 'always' mean?

Pachomius · (#6)

Quote:

Originally Posted by piesquared

Things to note:

1.) When we say "law" we don't necessarily mean that it is absolutely inviolable. Consider Netwon's 2nd law, which relativity and quantum mechanics later proved to be only a valid approximation of the truth at medium size and speed. Laws seem valid for our experiences so far... but if there were ever a situation where exceptions would take place, it'd be the big bang.
2.) Matter is a form of energy (E=mc^2).
3.) The big bang was either the start of time and space, or at the least wiped out any possibility of ever seeing what happened before.

And so the answer is simple - all the energy was present (in one form or another) at the big bang. Asking what happened before is not a valid question, because time effectively started then. There can be no causal relationship between anything after the big bang and anything before it - if indeed "before" has an any meaning in this context.

Alternatively, the "net" energy of the universe may be zero. It may be that at some point the universe will stop expanding and instead contract back to a singularity. Singularity to singularity - no net change, no net energy, no problem.

Finally, we at the big bang relativity and quantum mechanics collide. That's why we can't even retrace our steps all the way back to the big bang - relativity and quantum mechanics don't work together, but at that point they had to. This tells us that one or both of them requires a change of the same magnitude that each modified Netwon's laws. Since we don't know what the final laws will be, we can't apply them and figure out what exactly happened at the big bang. In short: we don't know, yet.

(Please note that while there's something missing from relativity and quantum mechanics, they are still both good approximations of the truth for big/fast things and small/slow things, respectively - in the same way that Netwon's laws are good approximations of the truth for medium size/speed things.)

You say:

And so the answer is simple - all the energy was present (in one form or another) at the big bang. Asking what happened before is not a valid question, because time effectively started then. There can be no causal relationship between anything after the big bang and anything before it - if indeed "before" has an any meaning in this context.

I want to bring your attention to this particular line:

Asking what happened before is not a valid question, because time effectively started then.

Do you mean that there is nothing outside time?

Pachomius

Thought Criminal · (#7)

Quote:

Originally Posted by bowmore

What else then "at every point in time" could 'always' mean?

In the cosmology I'm speaking of, there is a finite amount of time between the present and the first moment. If the universe has an end, there is a finite amount in total.

In the implicit model being used here, people speak casually of "before the BB" or "outside the universe", as if these were meaningful. In these models, time is either infinite or there are multiple forms of it.