Symmetry, as a mathematical concept, is widely generalized in physics. At that time, the German mathematical physicist Noether proposed the famous Noether theorem, which linked symmetry and conservation.

There is symmetry in time, and there is symmetry in space. Time is divided into time translation symmetry and time inversion symmetry.

What is the former? The properties that an object has today are the same as those that it has tomorrow.

That is, the properties of objects are unchanging at any time. Of course, this is a situation when external forces do not intervene.

If the temperature rises, the properties of the object must change somewhat. Why is it called translation? This is because the timeline is a straight line.

Although temporal translational symmetry and spatial translational symmetry are different concepts, the idea is the same.

If the object does not have the above symmetry, it cannot move and survive at all. For example, spatial translational symmetry.

When you go from BJ to Shanghai, you are still you. That's what it means. Of course, no matter how much you go around to get to Shanghai, the end result remains the same.

Therefore, the translation here has a tendency to generalize. According to Noether's theorem, one symmetry corresponds to one conservation.

And the time-translational symmetry corresponds to the conservation of energy, so why? It means that there is no change in time, and that change is ultimately embodied in energy.

There is no change, and there is no change in energy in nature. You might say that the change of time is also a change and should also be embodied by energy.

Note that we are talking about symmetry here for an object. Time is changing, but it belongs to the universe and not to an individual.

Therefore, changes in time are not counted when considering changes. Since time cannot exist separately from space, their two symmetries are intertwined.

Of course, spatial translational symmetry is not all-encompassing. Let's say you're in Hainan and then you're in Yushu or XSBN.

Well, the direction you come back in is different. For an object as perfectly symmetrical as a sphere, it is completely translationally symmetrical.

And people are only partially symmetrical, and there must be a difference in direction. You go out with your face outwards and walk in with your face inward.

So, there is a symmetry break here. Symmetry can be convenient, and so can symmetry breaking.

Nature, that is, shackles, is my motto. If you are a fully symmetrical object, then there must be a singularity in what you do.

Whether it's forward or backward, there's hardly much difference. Time reversal symmetry means that although the feeling is different when a video is watched upside down and upside down, the content presented is the same.

If you can look back at history at some point like a video rewind, notice that you are rewinding past events from the point in time you are now.

And the truth you discover in the process is no different from the truth. This symmetry is mainly to lay the foundation for traveling through time and space.

Because in this way, even if someone comes back to the past, it will not affect the past. Since time cannot leave space, it inevitably involves the symmetry of space reversal.

In fact, is time reversal symmetry and space reversal symmetry the same thing? If you want to reconnect the broken ones, be careful not to glue them together or re-repair them in other ways.

It's about really making that piece of broken glass a whole again. We can't rely on manpower except to go back to the past.

However, there is still the possibility that the glass can be restored from the physical level. So, they are fundamentally different.