Energy where does it come from?!

tiny-tim

but what if it goes back there?

Hypo

Its is at the same time is really confusing...
Not know where something came from and its "constant" how could you imagine energy to be infinite... Can't be created or destroyed... Confusing and mind bothering thought.

Hypo

Why? Well, everything in our daily lives every second of it depends on energy. Knowing more about it would be useful for our development and unlocking mysteries about life.

It has 2 main laws stated over 100 years ago and its still stand as it is. I just think we should study or review it.

I totally agree with the concept that it's always conserved. But can't be created or destroyed... That is the bothering part I'd like to find a solution for...

Drakkith

What makes you think we aren't doing this?

Solution to what? It can't be created or destroyed because that would require weird things to happen that we don't see, such as a rock that has fallen to the ground suddenly teleporting back to where it fell from, or the exhaust from a car suddenly splitting and recombining back to gasoline and oxygen for no reason.

Mark M

We DO understand why energy is conserved, because of Noether's theorem. Certain symmetries will ensure the conservation of certain quantities. For example, space-translation invariance. This means the laws of physics are the same regardless of your position. For example, Newton's laws still hold in the Andromeda galaxy just as well as they do here. Using Noether's theorem, we can use this symmetry to demonstrate the conservation of momentum.

Similarly, time-translation invariance, the symmetry in the laws of physics over time, ensures that energy must be conserved.

You can look up a mathematical derivation of the theorem or both momentum and energy. See here:

http://www.sjsu.edu/faculty/watkins/noetherth.htm

Mark M

Drakkith, I think you're confusing the conservation of energy, the first law, with the second law. This states that entropy will always increase towards the future. All of the things you listed *could* happen, but they're so statistically unlikely I wouldn't count on it. However, like you say, a violation of the conservation of energy would lead to nonsensical results.

DeepSpace9

Is the current mass of the universe a constant? Or is it possible for mass to be added to the universe? Or deducted?

audioloop

just spread....


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good to read
http://en.wikipedia.org/wiki/Future_...nding_universe

audioloop

not nothing.
I agree.

Drakkith

If they happened, would that not be a violation of the conservation laws?

Mark M

No, remember that one of those events is just an everyday process played in reverse. For example, if a cup of coffee with some cream in it spontaneously split into the coffee and the cream. If this violated a conservation law, then so would its reverse, mixing coffee and cream. However, we do this everyday and no laws are violated.

However, this would seem to violate the second law. But, as shown by Boltzmann in the late 19th century, the second law is just a statistical likelihood . There are more ways to have more entropy than less, so systems will naturally evolve towards states of more entropy. However, nothing strictly forbids something like coffee with cream splitting into coffee and cream. It's just highly, highly, unlikely.

bluey

There can be no nothing without something!Think about it,you have to have something to relate to nothingness As in ying and yang, its the symmetry of nature that expresses itself in electro-magnetism, ying as in electro and yang as in magnetism,without one or the other we don't exist,there wouldn't be any radiation heat light ect...

DennisN

• If energy can be created, would energy be conserved?
• If energy can be destroyed, would energy be conserved?

Aren't these things just different ways of saying the same thing?

Example from wiki:
"The law of conservation of energy:
This states that energy can be neither created nor destroyed. However, energy can change forms, and energy can flow from one place to another. The total energy of an isolated system remains the same."

Drakkith

I don't really understand. If the coffee split into coffee on one side, and cream on the other due to the random nature of the movement of the molecules, then that's fine, that has nothing to do with energy. But CO2 splitting and reforming into gasoline seems like a pretty big violation, as does the rock.

chill_factor

The rock can take thermal energy from its surroundings and turn it into mechanical energy if the 2nd law did not exist. Same for the exhaust, if it wasn't for the 2nd law, it can take thermal energy from the air to reform the chemical bonds.

Energy is part of the system. Let me give you an example for the OP:

Lets say you have a car moving at 100 miles per hour. It crashes into a stationary wall (lets put this as moving 0 miles per hour). There's energy which goes into shredding the metal of the car. But what about the same car, crashing into a wall moving at 99 miles per hour in the same direction? Maybe just minor bumper damage. WHY?!

If energy was something concrete, then why should the same car moving at the same speed, have different outcomes when it crashes into the same wall, but the wall moving differently?

The answer: energy is the property of a system. It is a helpful number that makes the calculations work out right. Don't worry about why. Lots of "why" questions have no answer. Instead think "how".

vincentm

Beautiful response, well put

Whovian

With all due respect, we're not talking philosophy here; we're talking cosmology.