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## High school physics - NGSS

### Course: High school physics - NGSS>Unit 3

Lesson 3: Energy and fields

# Energy and fields

When two objects interacting through a field change relative position, the energy stored in the field is changed. Created by Sal Khan.

## Want to join the conversation?

• So in this video, he is saying that fields and energy are related, right?

If that's right, then does that mean that fields can't be created or destroyed; they can only take on different forms?
• Yes, mathematically in physics, a field always has a value at every point in space and time, even where nothing is there. It can be argued that fields are always present (and not created nor destroyed), but instead take a value of zero in which case it is not applying a force to something.

Also, in quantum field theory (QFT), particles are basically represented by fluctuations or excitations in these fields. When there are no particles, the field is still there; it's just that it is not fluctuating in that particular moment of space and time.

(Therefore, a field is not created or destroyed, its always been there from the origins of the universe)
• So if I said that a blown up helium balloon for instance, has no gravitational pull because it floats up in the air would I be correct?

If I am correct, would that work on humans, or other animals?

And if I am not, Then why does a balloon float when it is blown up with helium? Is it because air moves around, and if the balloon is light enough it will just move with the air?
(1 vote)
• The reason is because helium is less dense than air. Like all things, they have densities, just because you can't see them doesn't mean they're not there.

Theoretically, yes. And this is sometimes demonstrated in outer space, when there is less gravity, people bounce around (for lack of a better term) a lot more.
• So in this video, he is saying that fields and energy are related, right?
(1 vote)
• what is meant by " Another way to think about it is instead of imagining that the energy is stored in the water drop, and it is really happening in our minds,"?
(1 vote)
• How big is time in physics? Is there a time field?
(1 vote)
• What is exactly pushing things apart? It's not mass so atoms aren't really involved, right?
(1 vote)

• This explanation brings into perfect sense of the Second Law of Thermodynamics, which states that when an object does work, that object loses energy.