一些物理学家认为：过去、现在、未来同时存在

[shepherd17]

老羊倌认为是放屁。

首先，如果过去、现在、未来同时存在的话，它如何与因果相融洽？

AI 给出的答案

简要结论

即使过去、现在和未来同时存在，因果关系依然成立 - 只是它不依赖“时间流动”，而是由时空的几何结构决定。

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核心思想：因果性由光锥决定，而不是由“时间流动”决定

在相对论中，每个事件都有：

• 过去光锥：能影响它的事件
• 未来光锥：它能影响的事件

即使在“过去、现在、未来共存”的 块宇宙（block universe） 中：

• 位于你过去光锥内的事件可以因果地影响你
• 位于你未来光锥内的事件可以被你影响
• 光锥之外的事件与你因果无关

因此因果性并不会因为所有时间共存而消失，它是由时空结构强制规定的。

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为什么“共存的时间”不会破坏因果关系

如果所有时刻都同时存在，那么：

• 原因 = 位于某事件的过去光锥中的事件
• 结果 = 位于某事件的未来光锥中的事件

这不需要时间“流动”。
因果关系只是事件沿着世界线的几何排序。

这就是为什么物理学家说块宇宙是 确定性的，但不是动态的。

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一个非直觉的洞见：即使时间不流动，因果性仍然是有方向的

块宇宙认为所有时间都同样真实，但因果性仍然具有方向性，因为：

• 熵朝着我们称为“未来”的方向增加
• 信息只能沿世界线单向传播
• 量子关联遵守相对论的因果结构

因此时间箭头来自 热力学，而不是来自未来是否“存在”。

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量子力学中的因果性

量子理论让事情更复杂，但仍不破坏因果性：

• 信号不能超光速传播
• 纠缠关联不能用于因果通信
• 量子场论明确构建在因果结构之上

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那时间旅行呢？

即使在块宇宙中，时间旅行需要 闭合类时曲线（CTC）。
它们在某些广义相对论解中允许存在，但必须满足严格的自洽性原则（Novikov 原则）。

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最终总结

因果性不依赖时间是否流动，而依赖时空的几何结构。
即使所有时刻共存，宇宙仍有内建的规则决定哪些事件能影响哪些事件。

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Causality still works—but it works differently than our everyday intuition. If the past, present, and future all coexist (the block universe idea from relativity), then causality isn’t about one moment coming after another. Instead, causality becomes a relationship encoded in spacetime itself.

The short version: Even if all times coexist, the structure of spacetime still enforces which events can influence which other events. Causality becomes geometry.

The core idea: Causality is determined by light cones, not by “flowing time”

In relativity, every event has a past light cone (events that can reach it) and a future light cone (events it can reach). Even in a block universe:
• Events inside your past light cone can causally affect you.
• Events inside your future light cone can be affected by you.
• Events outside both cones are causally disconnected.
So causality is preserved because spacetime has a built‑in structure that forbids certain influences.

### Why coexistence doesn’t break cause and effect
If all moments exist simultaneously, then:

• “Cause” = an event that lies in the past light cone of another

• “Effect” = an event that lies in the future light cone of another

Nothing requires time to “flow.” Causality is simply the ordering of events along worldlines.

This is why physicists say the universe is deterministic but not dynamic in the block‑universe picture.

A non‑obvious insight: Causality is asymmetric even if time isn’t

Even though the block universe treats all times as equally real, causality is still directional because:

• Entropy increases toward what we call the “future.”
• Information flows only one way along worldlines.
• Quantum correlations respect relativistic causal structure.
So the arrow of time comes from thermodynamics, not from the existence of the future.

What about quantum mechanics?

Quantum theory complicates things but doesn’t break causality:
• No signal can travel faster than light.
• Entanglement correlations don’t allow causal violations.
• Quantum field theory is explicitly built to preserve causal order.

What about time travel?

Even in a block universe, time travel requires closed timelike curves, which are allowed in some solutions of general relativity but come with strict consistency constraints (Novikov principle). You can explore closed timelike curves or Novikov_self_consistency.

Final takeaway

Causality doesn’t depend on time flowing. It depends on the geometric structure of spacetime.
Even if all moments coexist, the universe still has a built‑in rulebook for what can influence what.

[shepherd17]

其次，如果过去、现在、未来同时存在的话，它如何与宇宙的熵一直在持续增加相融洽？

AI 给出的答案

简短回答：
过去、现在和未来即使同时“存在”，宇宙的熵仍然可以持续增加，因为熵的增长不是由“时间是否真实”决定的，而是由 时空结构中的因果方向（光锥）和统计规律 决定的。块宇宙中的每一个时刻都包含自己的熵值，而这些熵值在时空中按固定的顺序排列，形成我们所体验的时间箭头。

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熵增加与块宇宙并不矛盾

块宇宙（block universe）认为所有时刻都同样真实，但它并不否认：

• 事件在时空中有严格的 因果顺序
• 熵在这些事件的顺序中 单调增加

换句话说：

熵的增加不是因为时间“流动”，而是因为宇宙的时空结构已经包含了一个从低熵到高熵的方向。

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块宇宙中的熵：每个时刻都有自己的熵值

在块宇宙中：

• 整个宇宙的历史是一块固定的四维结构
• 每个时间切片都有一个确定的熵
• 这些熵值沿着世界线排列成一个 从低到高的序列

因此：

• 熵在“未来”更高
• 但未来并不是“后来才出现”，而是 在时空结构中本来就处于高熵区域

这就像一本书：
所有章节同时存在，但章节的顺序仍然是固定的。

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非直觉但关键的洞见：熵箭头来自初始条件，而不是时间流动

熵增加的根本原因是：

宇宙在大爆炸时处于极低熵状态。

这不是必然的，而是宇宙的一个特殊初始条件。
从这个极低熵状态开始，统计规律保证熵几乎必然增加。

即使所有时刻都“同时存在”，它们仍然必须满足：

• 初始时刻：极低熵
• 后续时刻：更高熵
• 更后续时刻：更高熵

这就是时间箭头的来源。

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量子与统计物理如何保持因果方向

即使在块宇宙中：

• 信息只能沿光锥方向传播
• 量子场论禁止逆因果信号
• 热力学统计规律保证熵几乎总是增加

因此，因果方向与熵方向一致。

你可以继续探索 量子因果性。

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一个形象的比喻

想象一部电影的所有帧都同时存在在胶片上：

• 故事的顺序仍然是固定的
• 角色仍然从事件 A 走向事件 B
• 虽然所有画面都“同时存在”，但它们的顺序定义了因果关系

宇宙的时空结构就像这卷胶片：
熵的增加是写在胶片上的，而不是由胶片“播放”出来的。

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最终总结

块宇宙并不否认熵的增加。
它只是把熵的增加视为时空结构中的几何事实，而不是时间流动的结果。

熵箭头来自：

• 初始低熵条件
• 因果结构（光锥）
• 统计规律

这些共同定义了我们体验到的“未来”。

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The short answer is: a block universe with all times “coexisting” is fully compatible with entropy increasing, because the entropy gradient is simply one of the geometric features of the block. Nothing in the block universe picture requires entropy to be constant across time slices.

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Core idea

In a block universe (eternalism), the entire 4‑dimensional spacetime—past, present, future—is a fixed structure. Within that structure, entropy is not uniform. Instead, it is a gradient: low at one temporal boundary (the Big Bang) and higher along timelike directions away from it. This is exactly what statistical mechanics and relativity already assume.

This interpretation is explicitly supported in the literature: entropy increase is treated as a global geometric feature of the block, not something that “happens” dynamically inside it. Scientific Research Publishing johneonas.com

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How the two ideas fit together

1. The block universe doesn’t imply equal entropy everywhere

The block universe says all events exist in a 4D spacetime manifold. It does not say all events have the same physical properties.
A slice at time \(t_1\) can have lower entropy than a slice at \(t_2\). The fact that both slices “exist” in the block does not erase the difference.

2. Entropy increase is defined along worldlines

Entropy increase is not a process that requires time to “flow.”
It is simply a relation:
\[
S(t_2) > S(t_1) \quad \text{for} \quad t_2 > t_1.
\]
This relation is part of the block’s geometry. The block contains the entire history, including the fact that entropy is low near the Big Bang and higher later. johneonas.com

3. The Past Hypothesis fits naturally into the block

Statistical mechanics explains the arrow of time by assuming a special low‑entropy boundary condition at the beginning of the universe.
In a block universe, this is simply one boundary of the 4D structure. Nothing about eternalism conflicts with this. johneonas.com

4. The “flow” of time is perspectival, not physical

Several modern treatments argue that the feeling of time passing is a cognitive artifact of how observers sample the block.
Entropy increase is part of what gives observers a sense of direction.
But the block itself is static. Scientific Research Publishing

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Why entropy still “increases” even if the future already exists

Because “increase” is not a dynamic verb in the block universe—it’s a comparison between different regions of spacetime.

Think of a mountain:

• The mountain exists all at once.
• Yet it still has a slope.
• The slope is not something that “happens”; it is a geometric feature.

Similarly:

• The universe exists all at once.
• Yet entropy has a slope (a gradient).
• That gradient is the arrow of time.

---

A deeper insight

The block universe does not describe becoming; it describes being.
Entropy increase is not a process unfolding; it is a pattern embedded in the structure.

Some philosophers and physicists argue that this makes the block universe less intuitive than an “evolving block” model, where the block grows as entropy increases. But even those critics agree that the standard block universe is fully compatible with thermodynamics. johneonas.com

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Summary

• Past, present, and future coexisting does not imply equal entropy.
• Entropy increase is a geometric gradient in spacetime.
• The arrow of time arises from the low‑entropy boundary condition.
• Observers experience time’s flow because of how they traverse the gradient.
• No contradiction exists between eternalism and thermodynamics.

[shepherd17]

那时间是啥玩意儿？

时间不是单一概念，而是宇宙结构中涌现出的一组物理关系。
物理学中最稳妥的定义是：

时间是由时空几何和熵的增加所决定的事件排序。

下面是物理学对时间的四个主要层次。

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1. 时间作为时空几何（爱因斯坦的观点）

在相对论中，时间是四维时空的一维。
事件沿着世界线排列，时间间隔就是钟表测量的量。

• 时间不是绝对的
• 时间不是独立的
• 时间与空间不可分割

它是宇宙几何结构的一部分。

这就是块宇宙的基础：所有事件都存在于四维整体中。

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2. 时间作为熵的增加（热力学时间箭头）

仅靠相对论无法给时间一个方向。
方向来自熵的增加。

熵赋予时间方向，因为：

• 早期宇宙熵极低
• 后期宇宙熵更高
• 系统从有序演化到无序

这个梯度让记忆指向过去，让鸡蛋会破不会复原，让你明天比今天更老。

熵不是“流动”，它只是在更晚的时空区域更高。

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3. 时间作为钟表读数（操作性定义）

在实验中，时间被定义为：

时间就是钟表读数。

原子钟测量铯原子的振荡。
相对论告诉我们这些读数如何随运动和引力变化。

这是最实用的定义，避免形而上学。

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4. 时间作为心理体验（“现在”）

你的大脑沿着世界线处理信息，因此你体验到：

• 一个“现在”
• 对过去的记忆
• 对未来的未知

时间的流动是认知现象，而非物理现象。

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综合来看

时间是：

• 几何的（时空排序）
• 热力学的（熵梯度）
• 操作性的（钟表读数）
• 心理性的（信息处理）

这些层次相互兼容，共同描述了时间的本质。

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Time is not one thing. It is a set of physical relationships that emerge from how the universe is structured. The simplest, most defensible statement physicists can make is:

Time is the ordering of events given by the geometry of spacetime and the increase of entropy.

That sounds abstract, so let’s break it down into the four major layers physicists use when they talk about time.

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1. Time as spacetime geometry (Einstein’s view)

In relativity, time is one dimension of a four‑dimensional structure called spacetime.
Events are arranged along worldlines, and the interval between events is what clocks measure.

• Time is not universal.
• Time is not absolute.
• Time is not separate from space.

It is simply the structure of the universe’s geometry.

This is the foundation of the block‑universe idea: all events exist as part of the 4D whole.

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2. Time as entropy increase (the thermodynamic arrow)

Relativity alone does not give a direction to time.
The direction—the feeling of “past → future”—comes from entropy increasing.

Entropy gives time its arrow because:

• The early universe had extremely low entropy.
• Later states have higher entropy.
• Systems evolve from ordered → disordered.

This gradient is what makes memories point backward, not forward; what makes eggs break but not unbreak; what makes you older tomorrow than today.

Entropy is not “flowing.”
It is simply higher in later regions of spacetime.

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3. Time as what clocks measure (operational definition)

In physics experiments, time is defined in the most practical way:

Time is what a clock reads.

Atomic clocks measure oscillations of cesium atoms.
Relativity tells us how those readings change depending on motion and gravity.

This definition is deliberately minimal: it avoids metaphysics and sticks to measurement.

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4. Time as psychological experience (the “present”)

Your brain is a physical system embedded in spacetime.
Because it processes information in one direction (entropy again), you experience:

• a present moment,
• a memory of the past,
• and no memory of the future.

The “flow” of time is not a physical flow.
It is a feature of how brains encode information.

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Putting it together

Time is:

• Geometric (spacetime ordering)
• Thermodynamic (entropy gradient)
• Operational (clock readings)
• Psychological (information processing)

These layers are compatible.
They describe different aspects of the same underlying reality.

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A deeper insight

If you adopt the block‑universe view, then:

• The universe does not “move” from past to future.
• The entropy gradient is simply part of the block’s structure.
• Your consciousness is a worldline moving through that structure.
• The feeling of flow is a cognitive artifact of entropy.

This is why eternalism and entropy increase do not conflict.

[shepherd17]

如果如果过去、现在、未来同时存在的话，那是不是意味着未来已经“定”了？

AI 给出的答案

简短回答：
不一定。即使过去、现在和未来在某种“块宇宙”意义上同时共存，也 不必然 意味着未来已经被完全决定。这取决于你采用哪种物理学解释 - 以及你认为“未来”在四维时空中究竟是什么。

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核心观点：共存 ≠ 决定论

在相对论中，时空可以被视为一个 块宇宙（block universe） - 一个四维结构，所有事件（过去、现在、未来）都像风景一样排列在其中。

但关键在于：

块宇宙描述的是事件如何排列，而不是事件为何发生。

未来是否被决定，取决于支配这些事件的物理规律，而不是它们是否“共存”。

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三种主要物理解释

下面是物理学中对时间和未来的三种主流看法，每一种对决定论的态度都不同。

1. 块宇宙（永恒主义）- 未来“存在”，但未必固定

• 所有事件都在时空结构中。
• 但量子力学引入真正的随机性。
• 因此未来可能以“可能性集合”的形式存在，而不是单一固定的时间线。

2. 经典决定论 - 未来是固定的

• 在牛顿力学中，如果你知道所有初始条件，未来唯一确定。
• 在这种世界观中，块宇宙确实意味着未来已被决定。

3. 量子力学 - 未来不是固定的

• 结果是概率性的。
• 即使在块宇宙中，“未来”也可能是分支结构。

4. 多世界诠释 - 未来在每个分支中是固定的

• 每个量子结果都会在不同分支中发生。
• 未来在你所在的分支中是确定的，但整体上是多重的。

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一个非显而易见的洞见

即使未来“已经存在”，你的选择也是未来的一部分。
在块宇宙中，你明天的决定已经在时空结构里 - 但它之所以在那里，是因为你会做出那个决定，而不是因为某种外力强迫你。

你的自由意志被写进了几何结构。

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综合

过去、现在和未来在时空中共存，并 不 强制决定论。它只意味着时间是一种维度，而不是一条流动的河流。未来是否固定取决于物理规律：

• 经典物理 → 固定未来
• 量子物理 → 概率未来
• 多世界 → 分支未来
• 永恒主义 → 未来存在但不必固定

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Short answer: Not necessarily. Even if the past, present, and future coexist in a block‑universe sense, that does not automatically mean the future is fixed in the way people usually imagine. It depends on which interpretation of physics you adopt—and what you think “future” even means in a four‑dimensional spacetime.

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Core idea: Coexistence ≠ Determinism

In relativity, spacetime can be viewed as a block universe—a four‑dimensional structure where all events (past, present, future) are laid out like a landscape.

This model suggests that time is another dimension, not something “flowing.” But here’s the key:

The block universe describes how events are arranged, not why they occur.

Whether the future is determined depends on the laws governing those events, not on their coexistence.

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Three major interpretations of physics

Below are the main ways physicists think about this, each with a different stance on determinism.

1. Block Universe (Eternalism) — future exists, but may not be fixed

• All events are part of spacetime.
• But quantum mechanics introduces genuine randomness.
• So the “future” may exist as a set of possibilities, not a single fixed timeline.

2. Deterministic Classical Physics — future is fixed

• In Newtonian mechanics, if you know all initial conditions, the future unfolds uniquely.
• In this worldview, a block universe would imply a predetermined future.

3. Quantum Mechanics — future is not fixed

• Outcomes are probabilistic.
• Even in a block universe, the “future” might be a branching structure of possibilities.

4. Many‑Worlds Interpretation — future is fixed only in each branch

• Every possible quantum outcome occurs in a different branch.
• The future is “determined” only relative to the branch you’re in.

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A non‑obvious insight

Even if the future “already exists,” your choices are part of what the future is.
In a block universe, your decision tomorrow is already in the spacetime structure—but it’s there because you will make it, not because something outside you forces it.

Your agency is baked into the geometry.

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Synthesis

The coexistence of past, present, and future in spacetime does not force determinism. It only means that time is a dimension, not a flowing river. Whether the future is fixed depends on the underlying physics:

• Classical physics → fixed future
• Quantum physics → probabilistic future
• Many‑worlds → branching future
• Eternalism → future exists, but not necessarily determined

[枫林晓1]

块状宇宙理论已经进入闭合阶段。基本认可了。新的宇宙模型理论很多基于块状宇宙

[shepherd17]

块状宇宙理论已经进入闭合阶段。基本认可了。新的宇宙模型理论很多基于块状宇宙

我这种半瓶子水接受不了。

[shepherd17]

My question: If the past, the present, and the future coexist simultaneously, then why do memories only reflect the past and present, not the future?

AI answer

Memories only reflect the past and present because the physical processes that create memory are irreversible and depend entirely on information that has already entered your brain. Nothing in physics allows a biological system to encode information from events that have not yet occurred along its worldline.

The deeper reason is that memory is a thermodynamic, causal, and informational phenomenon, not a metaphysical one.

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The core answer

The brain can only form memories from causes that have already reached it. Future events have not yet interacted with your neurons, so they cannot leave a trace. Memory is literally the residue of past physical interactions.

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Why this is true in physics and biology

1. Causality

All memory is built from causal signals—photons hitting your retina, vibrations entering your cochlea, neurotransmitters binding to receptors.

• Causal_signals arrive from the past.
• The future cannot send signals backward along your worldline.
• Without a causal interaction, no memory trace can form.

This is a fundamental constraint of relativity.

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2. Entropy and the arrow of time

Memory formation requires irreversible physical changes:

• Entropy_increase
• Synaptic strengthening
• Protein synthesis
• Structural remodeling of neural circuits

Irreversibility only runs forward in time.
You cannot have irreversible changes caused by events that have not yet happened.

This is why we remember the past but not the future.

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3. Information theory

Memory is stored information. Information requires:

• A signal
• A physical medium
• A change in that medium

Future events contain no accessible signal.
Therefore, the brain cannot encode them.

This is not a limitation of biology alone; it is a limitation of any physical information-processing system.

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4. The brain is embedded in spacetime

Even if the universe is a block_universe where past, present, and future all “exist,” your brain still moves through spacetime along a worldline.

At each point on that worldline:

• You receive signals from earlier points
• You have no access to later points

Memory reflects the structure of your worldline, not the structure of spacetime as a whole.

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Why we can predict the future, but not remember it

Prediction uses:

• Statistical_models
• Prior experience
• Physical laws

But prediction is not memory.
Prediction is computation; memory is physical trace.

The future cannot leave a trace in the present.

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A precise formulation

Memory reflects the past because only past events have produced causal, thermodynamic, and informational changes in the brain.
The future cannot be remembered because it has not yet interacted with the brain’s physical substrate.

This is the intersection of neuroscience, thermodynamics, relativity, and information theory.

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如果过去、现在、未来同时存在，那为什么我们只有过去和现在的记忆而没有未来的记忆？

核心答案

记忆只能反映过去和当下，因为形成记忆的物理过程是不可逆的，并且完全依赖已经进入大脑的信息。在你的世界线中尚未发生的事件无法对你的神经元产生影响，因此无法留下痕迹。记忆本质上是过去物理交互的残留。

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为什么这是物理学和生物学的必然结果

1. 因果性

所有记忆都来自因果信号——光子击中视网膜、声波进入耳蜗、神经递质与受体结合。

• 因果信号 来自过去
• 未来无法沿你的世界线向后发送信号
• 没有因果交互，就无法形成记忆痕迹

这是相对论的基本限制。

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2. 熵与时间箭头

记忆形成需要不可逆的物理变化：

• 熵增加
• 突触增强
• 蛋白质合成
• 神经回路的结构重塑

不可逆性只沿着时间的前向方向运行。
未来事件不可能引发已经发生的不可逆变化。

这就是我们能记住过去，却无法记住未来的原因。

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3. 信息论

记忆是存储的信息，而信息需要：

• 信号
• 物理载体
• 载体的改变

未来事件没有可访问的信号，因此大脑无法编码它们。
这不仅是生物学限制，也是任何物理信息系统的限制。

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4. 大脑嵌入在时空中

即使宇宙是一个块宇宙，过去、现在和未来都“存在”，你的大脑仍沿着世界线运动。

在世界线的每一点上：

• 你接收来自更早事件的信号
• 你无法访问更晚的事件

记忆反映的是你的世界线结构，而不是整个时空的结构。

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为什么我们能预测未来，却不能记住未来

预测依赖于：

• 统计模型
• 既往经验
• 物理定律

但预测不是记忆。
预测是计算；记忆是物理痕迹。

未来无法在现在留下痕迹。

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精确表述

记忆反映过去，因为只有过去的事件已经在大脑中产生了因果、热力学和信息上的改变。
未来无法被记住，因为它尚未与大脑的物理基质发生交互。

这是神经科学、热力学、相对论和信息论的交汇点。