# For every action there is an equal and opposite reaction

• B
• Greenlight
In summary, the expansion of the universe does not have an equal and opposite reaction. There is no concept of "dark action" or any other form of reaction to the expansion. While there is a form of energy called dark energy that may contribute to the expansion, it does not follow the same principles as traditional actions and reactions.
Greenlight
TL;DR Summary
is there an equal and opposite reaction to the expansion of the universe?
if the universe is expanding, what is the equal and opposite reaction to this action?

Greenlight said:
Summary: is there an equal and opposite reaction to the expansion of the universe?
No.

if the universe is expanding, what is the equal and opposite reaction to this action?
Since there isn't one, this part of your question is not meaningful.

The universe isn't expanding into anything or against anything. It doesn't work the way you perhaps think it does.

No?

well i guess we could make one up...we can call it dark action. Now my equations work! j/kbut really isn't there dark energy? doesn't energy do work? isn't work action?

Greenlight said:
No?

well i guess we could make one up...we can call it dark action. Now my equations work! j/kbut really isn't there dark energy? doesn't energy do work? isn't work action?
The expansion of the universe is not that kind of thing, weirdly enough. There are TONS of threads on it here on PF. I suggest you poke around and read some of them, and/or just study the phenomenon online. Although exactly WHAT dark energy is is not well understood, how it works is.

## 1. What is Newton's Third Law of Motion?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert a force back on the first object that is equal in magnitude but opposite in direction.

## 2. How does Newton's Third Law apply to everyday life?

Newton's Third Law can be observed in many everyday situations. For example, when you push on a wall, the wall pushes back on you with an equal force, keeping you from falling through. Another example is when you jump off a diving board, the board pushes back on you with an equal force, propelling you into the air.

## 3. Does Newton's Third Law only apply to physical objects?

No, Newton's Third Law applies to all types of forces, including non-contact forces like gravity and electromagnetic forces. For example, the force of gravity between the Earth and the Moon is equal and opposite, causing them to orbit each other.

## 4. Can the equal and opposite forces cancel each other out?

No, the equal and opposite forces described by Newton's Third Law do not cancel each other out. They act on different objects and in opposite directions, so they cannot be added together. The objects will still experience the forces separately.

## 5. Is Newton's Third Law always true?

Yes, Newton's Third Law is a fundamental law of physics and is always true. It applies to all types of forces and has been extensively tested and confirmed through experiments and observations.

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