<p>This is spontaneous reversal of entropy. It happens at Planck times and Planck lengths, but for macroscopic events, the likelihood is the <em>product</em> (not sum)  of the particle event probabilities, all of which are tiny.</p>
<p>Electrons tunnel. Word on the street is that small molecules can. Cats and chairs don't. The sun, being even more massive, certainly doesn't reverse entropy.</p>

CC BY-SA 4.0
2024-06-09T06:41:26.097Z
Given how they can appear in the most random/unexpected ways, cats can _definitely_ quantum tunnel... I'll give you chairs, though.
TripeHound
CC BY-SA 4.0
2024-06-10T10:29:15.243Z
See Clifford Simak's seminal paper on the subject, _Catface_.
Will Crawford
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2024-06-11T03:03:13.037Z
Spontaneous reversal of entropy happens on scales much larger than Planck scales. On scales that are closer, in terms of orders of magnitude, to macroscopic scales than to Planck scales. In fact there are some things that can be considered to be reversal of entropy that happen at macroscopic scales. You might be confusing the first and second laws of thermodynamics and the second. The former can be violated at Planck scales.
Acccumulation
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2024-06-08T14:47:26.283Z
2024-06-08T15:57:04.717Z
2024-06-08T15:57:04.717Z
Miss Understands
<p>The answer is yes, for a small time interval <span class="math-container">$\tau$</span> seconds, there is a probability <span class="math-container">$\sim \exp(-10^{45}\tau)$</span> that no photons are emitted by the Sun.</p>
<p>Photons do not take millions of years to find their way to the surface of the Sun. They are absorbed and then remitted in different processes on short length scales and from that you can estimate timescales which looks like it effectively takes a million years to reach the surface.</p>
<p>In reality, the photons escaping the Sun are emitted/created from the photosphere, they do not come from the centre.</p>
<p>Having got that out of the way. The Sun emits <span class="math-container">$3.8\times 10^{26}$</span> W with a spectrum that peaks at <span class="math-container">$\sim 550$</span> nm. Crudely assuming all photons have that wavelength, the Sun emits <span class="math-container">$10^{45}$</span> photons per second.</p>
<p>If we assume that counting those photons obeys Poissonian statistics, then the probability of emitting zero photons in a time <span class="math-container">$\tau$</span>, when <span class="math-container">$10^{45} \tau$</span> is the expectation value, is <span class="math-container">$\exp(-10^{45}\tau)$</span>, where <span class="math-container">$\tau$</span> is in seconds. So set your probability threshold and work out <span class="math-container">$\tau$</span>.</p>
<p>e.g. If you want a 1 in <span class="math-container">$n$</span> chance that in some time interval the Sun emits no photons
<span class="math-container">$$\frac{1}{n} = \exp(-10^{45}\tau) \ . $$</span>
Take natural log of both sides to get
<span class="math-container">$$\tau = 10^{-45}\ln(n)\ .$$</span></p>
<p>Of course you can modify the problem to ask whether if you (don't do this) look at the Sun, or use a camera with an exposure time <span class="math-container">$\tau$</span> seconds to take a picture, what is the probability of the Sun emitting no photons <em>in your direction</em>. That is a similar problem, but you need to reduce the figure of <span class="math-container">$10^{45}$</span> to be appropriate for the fraction of the Sun's light intercepted by your detector.</p>

CC BY-SA 4.0
2024-06-10T05:42:22.200Z
I'm wondering whether there are fundamental restrictions preventing such a blackout for intervals above some threshold. Yes, if 10^30 or so photons from the Sun hit my eye per second randomly, there 10^-35s intervals without photons will occur -- but that's probably not what the OP meant. They probably meant, say, something like at least 1/1000 or 1/100 seconds. That's akin to ask whether a pebble can move 1/100 on my desk because the thermal movement of its atoms coincidentally was aligned for a moment. But that's not possible: The sum of all momentums is close to zero and cannot change.
Peter - Reinstate Monica
CC BY-SA 4.0
2024-06-10T05:52:35.863Z
Depending on the exact mechanism of radiation production in the photosphere (oscillations? collisions?), perhaps it would be necessary to align all movement (to direct radiation inwards) which is impossible like with the pebble. Or something else *impossible* (not *improbable*) must happen. Then there is the problem of energy storage fraxinus mentioned in a comment. There may not be a mechanism to store the energy flowing through the underlying layer at all. Even just 1/1000 of a second is tremendous energy. Perhaps the sun would explode from the resulting shock wave reverberating.
Peter - Reinstate Monica
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2024-06-10T07:06:27.617Z
@Peter-ReinstateMonica $exp(-10^{42})$ is too small for my calculator. I think statements about what is impossible must consider the uncertainty principle.
ProfRob
CC BY-SA 4.0
2024-06-10T17:14:45.617Z
A good example of where "impossible" thermal movement does in fact happen would be the aLIGO mirrors - these 50 kg mirrors are displaced by thermal motions in the mirror coating by sufficient $\sim 10^{-18}$ m to provide a significant source of noise in detecting gravitational waves.
ProfRob
CC BY-SA 4.0
2024-06-10T17:26:41.547Z
Well, 10^-18 is 15 orders of magnitude smaller than the 10^-3 I was suggesting as what the OP meant (and wondered whether it is strictly impossible). I am not surprised that there is thermal movement in the range of a tiny fraction of atom size. -- As an aside, one may argue that the uncertainty principle you mentioned in a previous comment is "orthogonal" to macroscopic conservation laws (that's the whole point, in a way) so that 1/1000 is not principally impossible the same way 10^-40 is not either; 1/1000 is just exponentially more *unlikely* which is discussed in all the other answers.
Peter - Reinstate Monica
CC BY-SA 4.0
2024-06-10T18:08:19.787Z
@Peter-ReinstateMonica not sure what you mean. The leading answer has now copied my quantitative answer. I haven't mentioned probabilities of 1/1000 or $10^{-40}$ anywhere. "Is it theoretically possible to have a period of time of any length..., ", this was the question and my answer is the only one that addresses this.
ProfRob
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2024-06-09T08:16:26.990Z
2024-06-09T08:16:26.990Z
ProfRob
<p>Is it theoretically possible for a statue to wave at you?  After all the atoms in a statue are moving randomly, so they <em>could</em> (by chance) all move in the same direction.</p>
<p>This doesn't happen.</p>
<p>It is the same with the Sun.  Photons are emitted from its surface randomly at a rate of about <span class="math-container">$10^{45}$</span> photons per second. Since it is random you can ask for the probability of no photons being released in a second,  and the number is so very small that it would make you wince (of the order <span class="math-container">$\exp(-10^{45})$</span>).</p>
<p>At this level of improbability, we can't reasonably say, &quot;It's a theoretical possibility&quot; and settle on &quot;This is impossible&quot;, because it won't happen.</p>
<p>The fact that photons take a long time to reach the surface is irrelevant to this. Moreover, it would be very detectable, by virtue of the Sun going dark for a second.</p>

CC BY-SA 4.0
2024-06-08T20:55:23.893Z
It will not go completely dark, it will dim for 3-4s. After all, its radius is ~2.5s. A nice black ring is to be expected, expanding from the visible center. Of course, we could calculate the probability of an Earth-directed time-synchronous blackout and this is many, many orders of magnitude higher and still deep into the 'impossible' realm.
fraxinus
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2024-06-08T21:23:08.217Z
It's impossible either way
James K
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2024-06-09T09:52:05.323Z
The probability of an Earth directed time-synchronous blackout is exactly the same as a blackout in a given second.
Pere
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2024-06-10T13:11:33.943Z
(Nitpick: the atoms in a statue _aren't_ moving randomly: AIUI, they're vibrating around (roughly) fixed positions in a rigid lattice, with amplitude depending on the temperature, so it would take more than just random motion to make the statue wave.  But I think a gaseous model (whose molecules _do_ move randomly) would work.)
gidds
CC BY-SA 4.0
2024-06-11T10:41:58.560Z
A plank time is about 5.4e-44 seconds long, so the sun emits about 54 photons per plank time. How big is the chance that there is a plank time where no photon is emitted? But then i guess you have to deal with relativity (there is no such thing as simultaneity), quantum properties (can you detect the exact location of a photon?) and the fact that the sun hasn't a exactly defined surface.
12431234123412341234123
CC BY-SA 4.0
2024-06-11T10:46:39.643Z
What does »in a second« even mean? The information from one point on the sun takes more than one second to the opposite side (about 4.64s). Relativity forbids you to have the same time on 2 different places.
12431234123412341234123
CC BY-SA 4.0
2024-06-11T16:46:05.977Z
"a second" is from the perspective of the observer on Earth.  In whatever spacetime frame you choose that means that different parts of the sun would "go dark" at different times.  This is also impossible.
James K
CC BY-SA 4.0
2024-06-08T13:57:08.087Z
2024-06-10T17:15:01.467Z
2024-06-10T17:15:01.467Z
James K
<p>If photons potentially take millions/billions of years to find their way to the surface of the Sun from the core, bouncing off billions of other atoms on their way. Is it theoretically possible to have a period of time of any length, where no photons make it to the surface? I realise that given the sheer amount of photons created and moving at the speed of light, any such event would be undetectable but is it possible that at some brief moment in time the Sun essentially blinks?<br/></p>

CC BY-SA 4.0
2024-06-08T21:00:28.433Z
Sun has somewhat constant energy production and the same power crosses every layer. Where do you intend to store a second worth of solar luminosity?
fraxinus
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2024-06-10T03:53:20.060Z
@fraxinus having read three good answers this question has generated, including Prof. Rob's interesting, educational and somewhat qualified "yes", I think your comment is more snark than science. **voting to leave open**.
uhoh
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2024-06-10T05:23:25.800Z
The Q is good enough as is, my comment was intended to hint the author of an important aspect of his idea
fraxinus
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2024-06-10T13:02:08.140Z
I have to point out that in about 20 billion years sun will be a black dwarf, and will only emit infrared. It will then not emit any visible light until falling onto another body. Whether that counts as a blink is a rhetorical question.
Basilevs
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2024-06-10T18:46:20.033Z
Would that be the same as the "opaque plasma" stage of the big bang?
Dave Gremlin
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2024-06-11T10:37:34.157Z
»a period of time of any length« How long? A Plancktime? But then you have to define what simultaneity means.
12431234123412341234123
CC BY-SA 4.0
2024-11-29T16:25:47.523Z
But what if a Jupiter sized planet collided with a sun-like star?
rdinardo
<star><the-sun><photons><theories>
Is it theoretically possible for the Sun to go dark?
Danny B86
# Is it theoretically possible for the Sun to go dark?

(Asked by: username_0 on 2024-06-08)

If photons potentially take millions/billions of years to find their way to the surface of the Sun from the core, bouncing off billions of other atoms on their way. Is it theoretically possible to have a period of time of any length, where no photons make it to the surface? I realise that given the sheer amount of photons created and moving at the speed of light, any such event would be undetectable but is it possible that at some brief moment in time the Sun essentially blinks?

**Tags:** star, the-sun, photons, theories

> **Comments:**
> **username_1**: Sun has somewhat constant energy production and the same power crosses every layer. Where do you intend to store a second worth of solar luminosity?  
> **username_2**: @username_1 having read three good answers this question has generated, including Prof. Rob's interesting, educational and somewhat qualified "yes", I think your comment is more snark than science. **voting to leave open**.  
> **username_1**: The Q is good enough as is, my comment was intended to hint the author of an important aspect of his idea  
> **username_3**: I have to point out that in about 20 billion years sun will be a black dwarf, and will only emit infrared. It will then not emit any visible light until falling onto another body. Whether that counts as a blink is a rhetorical question.  
> **username_4**: Would that be the same as the "opaque plasma" stage of the big bang?  
> **username_5**: »a period of time of any length« How long? A Plancktime? But then you have to define what simultaneity means.  
> **username_6**: But what if a Jupiter sized planet collided with a sun-like star?  

---

## 3 answers

### Answer by username_13 on 2024-06-08. Score: 33 | Accepted answer

Is it theoretically possible for a statue to wave at you? After all the atoms in a statue are moving randomly, so they *could* (by chance) all move in the same direction.

This doesn't happen.

It is the same with the Sun. Photons are emitted from its surface randomly at a rate of about $10^{45}$ photons per second. Since it is random you can ask for the probability of no photons being released in a second, and the number is so very small that it would make you wince (of the order $\exp(-10^{45})$).

At this level of improbability, we can't reasonably say, "It's a theoretical possibility" and settle on "This is impossible", because it won't happen.

The fact that photons take a long time to reach the surface is irrelevant to this. Moreover, it would be very detectable, by virtue of the Sun going dark for a second.

> **Comments:**
> **username_1**: It will not go completely dark, it will dim for 3-4s. After all, its radius is ~2.5s. A nice black ring is to be expected, expanding from the visible center. Of course, we could calculate the probability of an Earth-directed time-synchronous blackout and this is many, many orders of magnitude higher and still deep into the 'impossible' realm.  
> **username_13**: It's impossible either way  
> **username_14**: The probability of an Earth directed time-synchronous blackout is exactly the same as a blackout in a given second.  
> **username_15**: (Nitpick: the atoms in a statue _aren't_ moving randomly: AIUI, they're vibrating around (roughly) fixed positions in a rigid lattice, with amplitude depending on the temperature, so it would take more than just random motion to make the statue wave.  But I think a gaseous model (whose molecules _do_ move randomly) would work.)  
> **username_5**: A plank time is about 5.4e-44 seconds long, so the sun emits about 54 photons per plank time. How big is the chance that there is a plank time where no photon is emitted? But then i guess you have to deal with relativity (there is no such thing as simultaneity), quantum properties (can you detect the exact location of a photon?) and the fact that the sun hasn't a exactly defined surface.  
> **username_5**: What does »in a second« even mean? The information from one point on the sun takes more than one second to the opposite side (about 4.64s). Relativity forbids you to have the same time on 2 different places.  
> **username_13**: "a second" is from the perspective of the observer on Earth.  In whatever spacetime frame you choose that means that different parts of the sun would "go dark" at different times.  This is also impossible.  

---

### Answer by username_7 on 2024-06-08. Score: 10

This is spontaneous reversal of entropy. It happens at Planck times and Planck lengths, but for macroscopic events, the likelihood is the *product* (not sum) of the particle event probabilities, all of which are tiny.

Electrons tunnel. Word on the street is that small molecules can. Cats and chairs don't. The sun, being even more massive, certainly doesn't reverse entropy.

> **Comments:**
> **username_8**: Given how they can appear in the most random/unexpected ways, cats can _definitely_ quantum tunnel... I'll give you chairs, though.  
> **username_9**: See Clifford Simak's seminal paper on the subject, _Catface_.  
> **username_10**: Spontaneous reversal of entropy happens on scales much larger than Planck scales. On scales that are closer, in terms of orders of magnitude, to macroscopic scales than to Planck scales. In fact there are some things that can be considered to be reversal of entropy that happen at macroscopic scales. You might be confusing the first and second laws of thermodynamics and the second. The former can be violated at Planck scales.  

---

### Answer by username_11 on 2024-06-09. Score: 7

The answer is yes, for a small time interval $\tau$ seconds, there is a probability $\sim \exp(-10^{45}\tau)$ that no photons are emitted by the Sun.

Photons do not take millions of years to find their way to the surface of the Sun. They are absorbed and then remitted in different processes on short length scales and from that you can estimate timescales which looks like it effectively takes a million years to reach the surface.

In reality, the photons escaping the Sun are emitted/created from the photosphere, they do not come from the centre.

Having got that out of the way. The Sun emits $3.8\times 10^{26}$ W with a spectrum that peaks at $\sim 550$ nm. Crudely assuming all photons have that wavelength, the Sun emits $10^{45}$ photons per second.

If we assume that counting those photons obeys Poissonian statistics, then the probability of emitting zero photons in a time $\tau$, when $10^{45} \tau$ is the expectation value, is $\exp(-10^{45}\tau)$, where $\tau$ is in seconds. So set your probability threshold and work out $\tau$.

e.g. If you want a 1 in $n$ chance that in some time interval the Sun emits no photons
$$\frac{1}{n} = \exp(-10^{45}\tau) \ . $$
Take natural log of both sides to get
$$\tau = 10^{-45}\ln(n)\ .$$

Of course you can modify the problem to ask whether if you (don't do this) look at the Sun, or use a camera with an exposure time $\tau$ seconds to take a picture, what is the probability of the Sun emitting no photons *in your direction*. That is a similar problem, but you need to reduce the figure of $10^{45}$ to be appropriate for the fraction of the Sun's light intercepted by your detector.

> **Comments:**
> **username_12**: I'm wondering whether there are fundamental restrictions preventing such a blackout for intervals above some threshold. Yes, if 10^30 or so photons from the Sun hit my eye per second randomly, there 10^-35s intervals without photons will occur -- but that's probably not what the OP meant. They probably meant, say, something like at least 1/1000 or 1/100 seconds. That's akin to ask whether a pebble can move 1/100 on my desk because the thermal movement of its atoms coincidentally was aligned for a moment. But that's not possible: The sum of all momentums is close to zero and cannot change.  
> **username_12**: Depending on the exact mechanism of radiation production in the photosphere (oscillations? collisions?), perhaps it would be necessary to align all movement (to direct radiation inwards) which is impossible like with the pebble. Or something else *impossible* (not *improbable*) must happen. Then there is the problem of energy storage username_1 mentioned in a comment. There may not be a mechanism to store the energy flowing through the underlying layer at all. Even just 1/1000 of a second is tremendous energy. Perhaps the sun would explode from the resulting shock wave reverberating.  
> **username_11**: @Peter-ReinstateMonica $exp(-10^{42})$ is too small for my calculator. I think statements about what is impossible must consider the uncertainty principle.  
> **username_11**: A good example of where "impossible" thermal movement does in fact happen would be the aLIGO mirrors - these 50 kg mirrors are displaced by thermal motions in the mirror coating by sufficient $\sim 10^{-18}$ m to provide a significant source of noise in detecting gravitational waves.  
> **username_12**: Well, 10^-18 is 15 orders of magnitude smaller than the 10^-3 I was suggesting as what the OP meant (and wondered whether it is strictly impossible). I am not surprised that there is thermal movement in the range of a tiny fraction of atom size. -- As an aside, one may argue that the uncertainty principle you mentioned in a previous comment is "orthogonal" to macroscopic conservation laws (that's the whole point, in a way) so that 1/1000 is not principally impossible the same way 10^-40 is not either; 1/1000 is just exponentially more *unlikely* which is discussed in all the other answers.  
> **username_11**: @Peter-ReinstateMonica not sure what you mean. The leading answer has now copied my quantitative answer. I haven't mentioned probabilities of 1/1000 or $10^{-40}$ anywhere. "Is it theoretically possible to have a period of time of any length..., ", this was the question and my answer is the only one that addresses this.  

---

