/sci/ - Science & Math

>>5778103
Energy is everything, from a conversation toward someone to trigger a response, to a thought to ones self in which could in fact change the future in its own demention.

>>5778103

energy = mass * distance^2/time^2

>>5778111

that's ergs, is it?

>>5778103
Energy is a property of matter/ a system. The correct definition is that its the constant of motion conjugate to time. to understand what that means you have to understated that every symmetry goes together with a conserved quantity. In this case the conserved quantity (energy) is because time is homogeneous, so physics will be the same today as tomorrow and yesterday. Its the same as momentum, (which is conjugate to spacial direction), which is conserved due to space being homogeneous. you can see that breaking the symmetry breaks the conserved quantity by imagining a ball hitting a wall (when looking only at the ball), the wall obviously breaks the homogeneous space thus breaking the conservation of momentum in the system.

tl;dr - its just the function that is conserved of a system due to time being so the same.

Picture a universe run by a lazy god. The god has to get every object from its starting point at creation to its correct position on judgment day. She wants to do it in the way that takes the least amount of work on her part. Usually the slower she moves things around, the less work it takes. But if she slows down on one day, she has to speed up some other day, or she won't have everything in the right position when judgment day comes. So she adjusts her plan meticulously until she finds the sweet spot where the effect of speeding things up a little on one day and slowing things down on any other makes no difference in her workload. In the final plan that she implements, the extra work it would take her to shave off a second from a day's events is the same for all days. It's a conserved quantity. And that conserved quantity is what we call energy.

http://simple.wikipedia.org/wiki/Energy

>>5778148
>Energy in Science
>Energy is something that can do work.
>There are two basic forms of energy:
>Kinetic energy
>Potential energy
riiight.

Energy is the potential to make change. It's the most material you can get, as the universe fundamentally *is* change. Basically all we can infer is that the energy is the universe. All other notions are inherently wild speculation or metaphysical.

>>5778155
And what is your problem with that?
Other than your autism or "hur durr simple wiki doesn't contain the newest cern findings about energy with at least 5000 words"

>>5778186
>autism

>>5778198
Well i though so, so that clears that then.

>>5778186
>newest cern findings
i dint know cern researched classical mechanics in the 1950s

and please do work with the zero point energy of a harmonic oscillator for me. i want to see how its done. or is that not energy?

>>5778103
energy is the ability to do work
everything is energy - even matter.
that's what einstein's infamous E=mc^2 is about.

http://www.colorado.edu/physics/phys1110/phys1110_fa10/Feynman_energy.pdf

Everyone needs to read that at least once.

>>5778155
this guy knows what's up
we don't know what it is
we have useful but circular definitions of it

>>5778299
>everything is energy - even matter.
>that's what einstein's infamous E=mc^2 is about
Uh, no it's not. Energy is an abstract quantity - it doesn't make up anything. E=mc^2 tells us that mass is a form of energy, nothing else.

>>5778299
retarded

>>5778310
we know exactly what it is.

>>5778103
Do you know what is conservation of momentum? If two bodies of different masses and at different speeds collide, they exchange momentum.
The mass of the heavier body is <math>M</math> and mass of the lighter one is <math>m</math> and their respective speeds <math>v_0</math> and <math>u_0</math> you can derive that <math>M\vec{v_0}+m\vec{u_0}=M\vec{v_1} +m\vec{u_1}</math> . The right-hand side variables <math>\vec{v_1}</math> and <math>\vec{u_1}</math> are the speeds of the heavier and lighter body after the collision, respectively.
This conservation is derived from Newton's Law of Motion.
Energy is also a measure of the "motion" inside a system. But unlike momentum, it can is shared and exchanged by objects that spin, rise hills, fall, orbit, heat, vibrate, compresses, expand, change chemical composition and collide. If you take into account all the different forms of energy tranfer inside the system, it should remain the same if the system is a closed one, without exchanges of masses, fluids, heat or forces with the outside.
You can derive the concepts of kinetic and potential energy from Newtons Laws of Motion and the constant forces.
Imagined a body over a table is tied to a string. That string goes into a pulley on the edge of the table and is tied to a small object. The object is left hanging beside the table. Its weight is known. The force of on the body is the weight of the hanging object. You make the table very smooth so any movement is almost completely inertial i.e. frictionless.
What is the body's speed when the hanging object is free to pull it and the difference in height between when the hanging object started and finished?
Now use an object that is 4 times the size. What would it speed be?
This demonstrates the principle of exchange of gravitational potential energy into kinetic energy. Any moving body or fluid has energy.
continued...

energy is a constant of integration!

energy is a constant of integration! but we still use it when its not conserved

it's simply a number.

>>5778594
The mass of the heavier body is <span class="math">M[/spoiler] and mass of the lighter one is <span class="math">m[/spoiler] and their respective speeds <span class="math">v_0[/spoiler] and <span class="math">u_0[/spoiler] you can derive that <span class="math">M\vec{v_0}+m\vec{u_0}=M\vec{v_1} +m\vec{u_1}[/spoiler] . The right-hand side variables <span class="math">\vec{v_1}[/spoiler] and <span class="math">\vec{u_1}[/spoiler] are the speeds of the heavier and lighter body after the collision, respectively.

Energy is the ability to do work.

http://starwars.wikia.com/wiki/The_Force

>>5778617

but you can add energy without doing work...

It's a quantity we came up with to to describe change in a physical system.

>>5778594
[continuing]
Advancing Classical Physics proved that heated bodies and gases have similarly convertible energy. That explained the workings of steam engines. Chemicals can produce heat, so they contained chemical energy. The study of electricity proved that electrical charges could also store energy. And so could magnets.

Later, heat and chemical energy were explained as kinetic and potential energy of small particles that made up substances, this was tested and proved by mathematical models of such particles.

With the research on electricity it was discovered how it relates with magnetism. A magnet can make an electrical field and an electrical charge can produce magnetic effects. This lead to Electromagnetism and Maxwell Equations that describe it. Energy is a fundamental part of its development and how it works.

The equations predicted Electromagnetic waves that no one have ever imagined possible. But Maxwell himself was sure that light itself was a form of such waves, but it could still be just a conjecture. Until the German scientist Heinrich Hertz in 1887 produced and detected such waves artificially, radio waves, 23 years after Maxwell mathematically predicted their existence. A huge success.

But after Maxwell Equations were looked into more deeply in the beginning of the 20th century, it was discovered that the speed of objects could make the equations behave very oddly. If the objects were to reach speeds that were representative fractions of the speed of electromagnetic waves, the equations predicted extremely unlikely things. Objects of certain charge would attract themselves with different strength than if they were resting instead. This lead to the possibility that different observers going in different directions while the Earth rotates at about 1670 km/h (or at different moments while the Earth orbits the sun, the speed gradually changes from 30.29 km/s to 29.29 km/s) would measure different electrical forces.
But this was not true.

>>5778617
Sure you're not thinking of Gibb's free energy?

>>5778103
Energy is just some abstract conserved quantity. It doesn't admit a unified physical interpretation. The way we axiomatise physical theores is basically like this:
- There is this thing called energy
- Physical systems behave in some matter which depends on said energy
Since "energy" is defined externally to the theory (it is used in its axiomatisation) the theory cannot explain what energy is.

>>5778751
By the way, for an example of said axiom system look up "Hamiltonian mechanics" and "Hamilton's principle".

>>5778139
If she's so lazy, why did she go to all that effort to find the "sweet spot"?

Also,
>God
>she

Take that, creationists!

>>5778270
>Simple English Wikipedia

>>5778741
continuing
Trying to come up with changes to Maxwell equations that could make them work the same on different speeds, scientists came up with a solution:
Objects and observers contract and dilate depending on their relative speed. Their perception of distant simultaneous events are different. Two simultaneous events for one observer is not simultaneous to a second one.
Einstein was the one that perfected this concept and then he reworked the relationship between kinetic energy and potential energy. While doing this he corrected equations for this relativistic momentum and found the correct relationship between energy and mass for a resting body. <span class="math">E=mc^2[/spoiler].
This meant that resting mass could also, somehow, be turned into pure energy.
And that any energy stored inside a body, electromagnetic, heat, chemical, contributed to the mass of the body. A spinning top weights more than a resting top. A charged electric battery weights more than a discharged one. Hydrogen and oxygen weight more when pure than when they combine into water. The effect is negligible for these moderate levels of energy.
But with the discovery of the nuclear radiation and decay, it was clear that the huge amounts of energy released from atoms actually decreases its mass. And so it was proved mass can be turned to energy and energy can be turned to mass.

>>5778751
>Energy is just some abstract conserved quantity
Energy is not an abstract quantity. It is the measure of a system ability to do work, ultimately accelerate masses and move them against forces. Large or small. Cosmic or subatomic.

>"energy" is defined externally to the theory (it is used in its axiomatisation)
The concept of energy arises from the need to quantify the ability of a system to cause motion or dislocation against forces. It is not an axiom. It is a relationship.

>theory cannot explain what energy is
The theory explain energy relationship to forces, matter, the known components of the Universe. It is extremely relevant.

>>5778877
>relationship to forces, matter

>>5778751
Matter cannot be explained in a separately from forces either, just like energy. Does that makes it unexplained because it require a relationship to be defined?

>>5778891
"Matter is a poorly-defined term in science (see below). The term has often been used in reference to a substance (often a particle) that has rest mass. Matter is also used loosely as a general term for the substance that makes up all observable physical objects."
http://en.wikipedia.org/wiki/Matter