<p>No, the Earth will not start to rotate in the opposite direction. Ever.</p>
<p>The reason Earth maintains its direction of rotation is conservation of angular momentum. Just like a moving body resists changes in velocity because it has linear momentum, a rotating body will resist forces that try to change its rotation state. Angular momentum can be moved around in a composite system (consider a figure skater pulling in her arms while spinning), but it doesn't disappear unless there is a lot of friction. Which space lacks.</p>
<p>There is a grain of truth in the confused articles that led to the question: Earth is losing some angular momentum over time. Most of this is due to tidal interactions with the moon. When the moon formed Earth rotated much faster and the moon was close. Mutual gravitation caused tides that made some of the angular momentum transfer from Earth to the moon, slowing the rotation of both (to the extent the Moon now only turns one face towards the Earth, tidal locking) and giving the moon more angular momentum in its orbit, making it move outwards at a very slow rate. There are also tides from the sun (and other planets) but they are too small to matter here.</p>
<p>In reality, the sun will become a red giant in 5 billion years and expand, ending the story of the Earth and moon (ironically in this context, likely by tides dragging in Earth into the sun when it gets close enough to the surface). But if we ignore that, what would happen?</p>
<p>As the Earth's rotation is slowed by lunar tides, eventually it would become tidally locked to the moon in about 50 billion years. The moon would always stay over the same spot, visible only from one hemisphere. But Earth, like the moon today, would also continue to rotate around its axis. It is just that the &quot;day&quot; would be more than a month (about 47 days), corresponding to one full rotation of the Earth-moon system. <strong><strong>But the direction would be the same as now, since the moon is moving around the Earth in the same direction as Earth is rotating.</strong></strong></p>
<p>At this point there would still be some loss of angular momentum due to solar tides, so over very long time periods (about 50 billion years more) the Earth and moon would slowly orbit closer and closer. Eventually they would merge into an (again) somewhat fast spinning body (still moving in the same direction!)</p>
<p>In the <em>really</em> long run tidal forces would slow this rotation so the big planet would be tidally locked to the sun. But again, the one-year rotation of the planet would be in the same direction as now.</p>
<p>There is a lot of nonsense claimed on the Internet. Learn the basic laws of physics like conservation of energy and momentum, get used to do rough calculations, and you can usually see through it quickly.</p>

CC BY-SA 4.0
2021-01-11T13:09:16.713Z
2021-01-11T13:09:16.713Z
Anders Sandberg
<p>There is a lot of confusion in those articles.</p>
<p>The headline though is <strong>The Earth won't start rotating backwards</strong> and <strong>The sun won't rise in the West</strong></p>
<ol>
<li><p>Yes Mars and the other planets do move retrograde against the stars.  This happens once every year-and-a-bit, and is a perspective effect.  The Earth moves faster than Mars and so it can overtake it.  When Earth overtakes Mars, it appears to be going backwards. But to be clear <strong>Mars never actually goes backwards</strong>, and <strong>The orbit of the Earth never goes backwards</strong>. So finally <strong>The Sun will not rise in the west</strong>.  The rest of the first article is just how this would confirm prophecy, and contains no astronomy.</p>
</li>
<li><p>Is a copy-and-paste combination of 1 and 3</p>
</li>
<li><p>Yes, the Earth's magnetic poles do sometimes &quot;flip&quot;, and quite quickly on a Geological scale, taking only a few thousand years.  There is some reason to think that a flip might occur in the next 100,000 years or so.  There is no particular reason to believe that a flip is imminant.  During a flip the magnetic field would weaken, and there would be less protection from the sun, but in previous flips, exactly 0 animals went extinct as a result of the flip.  And even if the magnetic poles flip, the rotational poles stay the same. So <strong>The Sun will not rise in the West</strong></p>
</li>
<li><p>This article is a &quot;What if&quot;.  It considers various effects of the Earth changing direction. It states &quot;the earth is not likely to spontaneously change directions&quot;  This might be the understatement of the decade.  <strong>It is absolutely impossible for the Earth to change direction unless willed to by God</strong>.  Nothing physical do this: not man, nor asteroid impact, nor aliens.</p>
</li>
</ol>
<p>In short these are three unreliable sources. Please just forget.</p>

CC BY-SA 4.0
2021-01-11T18:39:51.883Z
Respectfully, I think we should leave "God's will" out of Astronomy Stack Exchange.  We don't all share the same God belief, and I think it distracts us from the scientific arguments.
Connor Garcia
CC BY-SA 4.0
2021-01-11T18:46:02.080Z
It is highly relevant to the OP's question; if you see the links 1 it is about how this will be a fulfillment of prophesy.  Whether you believe in God or not, I stand by the fact that It is absolutely impossible for the Earth to change direction unless willed to by God.  If you believe in an all powerful god or gods, then you believe that god can do this.  If you don't then I claim it is completely impossible.  I could have included "magic" but I thought this would be flippant in the context in which the OP asked the question.
James K
CC BY-SA 4.0
2021-01-11T13:45:10.967Z
2021-01-11T13:45:10.967Z
James K
<h2>Almost certainly not.</h2>
<p>All available information seems to indicate that the Earth will probably not reverse it's spin direction before it ends. However, we don't have absolute certainty of this.</p>
<p><strong>Inner-planetary collisions</strong></p>
<p>There are numerical simulations indicating the &quot;Existence of collisional trajectories of Mercury, Mars, and Venus with Earth&quot; within 5 Gyr time-scales, published in Nature by <a href="https://www.nature.com/articles/nature08096" rel="nofollow noreferrer">Laskar and Gastineau 2009</a>.  These are based on the possibility of potential resonance orbits of the inner planets with Jupiter.  Laskar was influential in showing that the Solar System is a mathematically chaotic system on large time scales.  While the probability of inter-inner-planetary collisions was extremely low according to their simulations, <span class="math-container">$unlikely \ne impossible$</span>.  For certain grazing impacts, &quot;angular momentum dominates&quot; according to <a href="https://arxiv.org/ftp/arxiv/papers/1810/1810.05797.pdf" rel="nofollow noreferrer">Elkins-Tanton and Weiss 2016</a> as shown in one of the excellent figures from their paper:</p>
<p><a href="https://i.sstatic.net/tofwj.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/tofwj.png" alt="enter image description here" /></a></p>
<p>A sufficiently energetic inter-planetary collision could certainly change Earth's spin direction and either merge, graze, or potentially strip the mantle.</p>
<p><strong>Exoplanetary collisions</strong></p>
<p>Also, I don't think we can rule out the possibility of a near miss of our Solar System with another stellar system within the Milky Way.  We know that there are <a href="https://astronomy.stackexchange.com/questions/40718/is-there-a-retrograde-star-that-passes-closer-to-the-galactic-center-than-our-su">some stars in retrograde galactic orbits that cross the Sun's prograde orbit</a> around the Milky Way.  If our Solar System was to pass through the stellar system of a retrograde star, an Earth collision with an exoplanet would be possible.</p>
<p><strong>Notes:</strong></p>
<ol>
<li><p>One could argue that after a planetary collision, the Earth's composition would be so changed that it would no longer be the Earth.  We could consider another case in which our Moon was knocked out of Earth orbit by a collision. Then the obliquity of the Earth would vary up to about 85 degrees according to <a href="https://www.nature.com/articles/361615a0" rel="nofollow noreferrer">Laskar et al.</a>.  If another smaller Earth impact collision tipped the obliquity past 90 degrees, the Earth would indeed be spinning the opposite direction without much change to its composition.</p>
</li>
<li><p>The sources linked by the OP are not scientifically credible, but that doesn't mean we can rule out the possibility of their conclusions.  Astronomy is still an incredibly vibrant and open field with many unanswered questions.  I don't think we can be 100% certain that the Earth's spin direction will never change when we don't have a <a href="https://astronomy.stackexchange.com/questions/26/what-is-the-current-accepted-theory-as-to-why-venus-has-a-slow-retrograde-rotati">universally accepted explanation for Venus's retrograde rotation</a>.</p>
</li>
<li><p>I disagree with the heavy downvoting of the OP's question. They edited their post by adding links and their question is valid.</p>
</li>
</ol>

CC BY-SA 4.0
2021-01-12T17:41:16.810Z
2021-01-12T17:41:16.810Z
Connor Garcia
<p>Hello recently I heave heard the earth will eventually start rotating in the opposite direction (ie sunrise from the west) . I am not sure if this is true, but a lot of sites are claiming it to be true, they say that the earth's rotation is slowing down slowly, and it will eventually stop and start rotating in the opposite direction, please let me know if this is true or not as I do not have much knowledge in astronomy.</p>
<p>EDIT:</p>
<p>Some of the sites that claim this event to be true, explain it in this way -
they say
&quot;The earth is slowing down every year, so much so that when it first started spinning each day was only 4 hours but now it's 24 hours, a day will come when the earth will stop rotating and it will behave like a spring and then it will start rotating in the opposite direction (they don't mention if humans will be alive till that day or not) &quot;</p>
<p>Here are the sources that led me to consider the possibility of this event-</p>
<p>1 - <a href="https://archive.siasat.com/news/nasa-confirms-possibility-sun-rising-west-102184/#:%7E:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!" rel="noreferrer">https://archive.siasat.com/news/nasa-confirms-possibility-sun-rising-west-102184/#:~:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!</a>!</p>
<p>2 - <a href="https://medium.com/@loadjunker/nasa-confirms-possibility-of-sun-rising-from-the-west-ad5ddd166c11#:%7E:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!" rel="noreferrer">https://medium.com/@loadjunker/nasa-confirms-possibility-of-sun-rising-from-the-west-ad5ddd166c11#:~:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!</a>!</p>
<p>3 - <a href="https://www.express.co.uk/news/science/597607/Sunrise-WEST-Scientists-warn-magnetic-poles-SWITCHING-North-become-south" rel="noreferrer">https://www.express.co.uk/news/science/597607/Sunrise-WEST-Scientists-warn-magnetic-poles-SWITCHING-North-become-south</a></p>
<p>4 - <a href="https://medium.com/swlh/if-the-sun-rises-from-the-west-92452a570f86" rel="noreferrer">https://medium.com/swlh/if-the-sun-rises-from-the-west-92452a570f86</a></p>

CC BY-SA 4.0
2021-01-07T10:58:54.087Z
If this is a genuine question, please just forget.
Alchimista
CC BY-SA 4.0
2021-01-07T11:41:17.630Z
If there are "many sites", you can surely provide sources (which are not of the esoteric type)
planetmaker
CC BY-SA 4.0
2021-01-07T15:14:44.863Z
Addendum: it is true that the Earth's rotation slow down, but extremely slowly and there is no reason for inversion.
Alchimista
CC BY-SA 4.0
2021-01-07T21:33:30.753Z
No. Earth will not start rotating in the opposite direction. Please see a more valid source if you are genuinely asking this.
Max0815
CC BY-SA 4.0
2021-01-08T00:29:28.373Z
I think it might some reincarnation of the magnetic pole shift thing from about a decade ago.
peterh
CC BY-SA 4.0
2021-01-08T01:10:45.777Z
When you hear things like this, try to imagine how it would work - what it would take. 

Use things that you _do_ know about to help you. 

Imagine, for instance, taking a ball and spinning it on a table, floor, or your finger. 

The ball will stop moving after some time, due to forces acting upon it. 

Does the ball at this point then begin rotating in a reverse direction? Why / why not? What does it take for that to happen? 

And what about a heavier ball of the same size? Spin both at the same time, which stops first, and why?
etc...
Aaron F
CC BY-SA 4.0
2021-01-08T04:26:01.983Z
Does this answer your question? [Will the Earth ever be tidally locked to the Moon?](https://astronomy.stackexchange.com/questions/18794/will-the-earth-ever-be-tidally-locked-to-the-moon)
PM 2Ring
CC BY-SA 4.0
2021-01-08T12:13:50.930Z
I vote to reopen.  The OP has a valid, focused question.  The source of the claim is not relevant.  We know that tidal locking is a thing, an answer would explain why the rotation can't reverse.  It would not be easy to research an answer to this.  We need to be more open to newbie questions.
Dave Gremlin
CC BY-SA 4.0
2021-01-09T19:44:15.630Z
@planetmaker https://archive.siasat.com/news/nasa-confirms-possibility-sun-rising-west-102184/#:~:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!!&text=!!,-And%20the%20strange
X caliber
CC BY-SA 4.0
2021-01-10T02:05:59.567Z
I would like to encourage you to modify/amend your question with that link
planetmaker
CC BY-SA 4.0
2021-01-10T02:08:55.710Z
@Dave Gremlin: the source is very much relevant. Judging credibility of sources is an important skill. And it gives context which here seems relevant (see link)
planetmaker
CC BY-SA 4.0
2021-01-11T10:20:36.623Z
@planetmaker i edited the post and added the sources.
X caliber
CC BY-SA 4.0
2021-01-11T14:27:21.090Z
@AaronF If you don't know the cause of the changing angular velocity, it's not easy to reach that conclusion. For instance, if you throw a piece of paper against the wind, it will also slow down. Will it ever starting moving in the opposite direction?
pela
CC BY-SA 4.0
2021-01-12T02:27:10.930Z
I ddon't know about the future but, in the past, it rotated backwards on a Superman movie.
John Canon
CC BY-SA 4.0
2021-01-13T10:16:22.950Z
@pela my point is that by thinking about the problem critically, and trying to imagine the forces involved, then you're starting to reason about it. It doesn't matter if you're right or wrong in your conclusions. Just wondering about it will give you something to research, or at least will give you more to write about when you ask the question on SE :-)
Aaron F
CC BY-SA 4.0
2021-01-13T19:47:56.443Z
@AaronF Okay, fair enough :)
pela
CC BY-SA 4.0
2022-03-27T04:03:24.180Z
It's worth noting that some of your sources are influenced by the existence of an Islamic prophecy about the sun rising in the west.  They are coming from a religious stance, not a scientific one.
Dawood ibn Kareem
CC BY-SA 4.0
2023-01-24T17:22:48.917Z
@Xcaliber the earth is actually spinning faster. Where did you see this?
Deko Revinio
<earth><rotation>
Will Earth rotate backwards in the future?
X caliber
# Will Earth rotate backwards in the future?

(Asked by: username_0 on 2021-01-07)

Hello recently I heave heard the earth will eventually start rotating in the opposite direction (ie sunrise from the west) . I am not sure if this is true, but a lot of sites are claiming it to be true, they say that the earth's rotation is slowing down slowly, and it will eventually stop and start rotating in the opposite direction, please let me know if this is true or not as I do not have much knowledge in astronomy.

EDIT:

Some of the sites that claim this event to be true, explain it in this way -
they say
"The earth is slowing down every year, so much so that when it first started spinning each day was only 4 hours but now it's 24 hours, a day will come when the earth will stop rotating and it will behave like a spring and then it will start rotating in the opposite direction (they don't mention if humans will be alive till that day or not) "

Here are the sources that led me to consider the possibility of this event-

1 - [https://archive.siasat.com/news/nasa-confirms-possibility-sun-rising-west-102184/#:~:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!](https://archive.siasat.com/news/nasa-confirms-possibility-sun-rising-west-102184/#:%7E:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!)!

2 - [https://medium.com/@loadjunker/nasa-confirms-possibility-of-sun-rising-from-the-west-ad5ddd166c11#:~:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!](https://medium.com/@loadjunker/nasa-confirms-possibility-of-sun-rising-from-the-west-ad5ddd166c11#:%7E:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!)!

3 - <https://www.express.co.uk/news/science/597607/Sunrise-WEST-Scientists-warn-magnetic-poles-SWITCHING-North-become-south>

4 - <https://medium.com/swlh/if-the-sun-rises-from-the-west-92452a570f86>

**Tags:** earth, rotation
> **Comments:**
> **username_1**: If this is a genuine question, please just forget.  
> **username_2**: If there are "many sites", you can surely provide sources (which are not of the esoteric type)  
> **username_1**: Addendum: it is true that the Earth's rotation slow down, but extremely slowly and there is no reason for inversion.  
> **username_3**: No. Earth will not start rotating in the opposite direction. Please see a more valid source if you are genuinely asking this.  
> **username_4**: I think it might some reincarnation of the magnetic pole shift thing from about a decade ago.  
> **username_5**: When you hear things like this, try to imagine how it would work - what it would take.   Use things that you _do_ know about to help you.   Imagine, for instance, taking a ball and spinning it on a table, floor, or your finger.   The ball will stop moving after some time, due to forces acting upon it.   Does the ball at this point then begin rotating in a reverse direction? Why / why not? What does it take for that to happen?   And what about a heavier ball of the same size? Spin both at the same time, which stops first, and why? etc...  
> **username_6**: Does this answer your question? [Will the Earth ever be tidally locked to the Moon?](https://astronomy.stackexchange.com/questions/18794/will-the-earth-ever-be-tidally-locked-to-the-moon)  
> **username_7**: I vote to reopen.  The OP has a valid, focused question.  The source of the claim is not relevant.  We know that tidal locking is a thing, an answer would explain why the rotation can't reverse.  It would not be easy to research an answer to this.  We need to be more open to newbie questions.  
> **username_0**: @planetmaker https://archive.siasat.com/news/nasa-confirms-possibility-sun-rising-west-102184/#:~:text=And%20this%20weird%20phenomena%20of,rise%20from%20the%20west!!&text=!!,-And%20the%20strange  
> **username_2**: I would like to encourage you to modify/amend your question with that link  
> **username_2**: @Dave Gremlin: the source is very much relevant. Judging credibility of sources is an important skill. And it gives context which here seems relevant (see link)  
> **username_0**: @planetmaker i edited the post and added the sources.  
> **username_8**: @AaronF If you don't know the cause of the changing angular velocity, it's not easy to reach that conclusion. For instance, if you throw a piece of paper against the wind, it will also slow down. Will it ever starting moving in the opposite direction?  
> **username_9**: I ddon't know about the future but, in the past, it rotated backwards on a Superman movie.  
> **username_5**: @pela my point is that by thinking about the problem critically, and trying to imagine the forces involved, then you're starting to reason about it. It doesn't matter if you're right or wrong in your conclusions. Just wondering about it will give you something to research, or at least will give you more to write about when you ask the question on SE :-)  
> **username_8**: @AaronF Okay, fair enough :)  
> **username_10**: It's worth noting that some of your sources are influenced by the existence of an Islamic prophecy about the sun rising in the west.  They are coming from a religious stance, not a scientific one.  
> **username_11**: @Xcaliber the earth is actually spinning faster. Where did you see this?  

---

## 3 answers

### Answer by username_12 on 2021-01-11. Score: 11

No, the Earth will not start to rotate in the opposite direction. Ever.

The reason Earth maintains its direction of rotation is conservation of angular momentum. Just like a moving body resists changes in velocity because it has linear momentum, a rotating body will resist forces that try to change its rotation state. Angular momentum can be moved around in a composite system (consider a figure skater pulling in her arms while spinning), but it doesn't disappear unless there is a lot of friction. Which space lacks.

There is a grain of truth in the confused articles that led to the question: Earth is losing some angular momentum over time. Most of this is due to tidal interactions with the moon. When the moon formed Earth rotated much faster and the moon was close. Mutual gravitation caused tides that made some of the angular momentum transfer from Earth to the moon, slowing the rotation of both (to the extent the Moon now only turns one face towards the Earth, tidal locking) and giving the moon more angular momentum in its orbit, making it move outwards at a very slow rate. There are also tides from the sun (and other planets) but they are too small to matter here.

In reality, the sun will become a red giant in 5 billion years and expand, ending the story of the Earth and moon (ironically in this context, likely by tides dragging in Earth into the sun when it gets close enough to the surface). But if we ignore that, what would happen?

As the Earth's rotation is slowed by lunar tides, eventually it would become tidally locked to the moon in about 50 billion years. The moon would always stay over the same spot, visible only from one hemisphere. But Earth, like the moon today, would also continue to rotate around its axis. It is just that the "day" would be more than a month (about 47 days), corresponding to one full rotation of the Earth-moon system. ****But the direction would be the same as now, since the moon is moving around the Earth in the same direction as Earth is rotating.****

At this point there would still be some loss of angular momentum due to solar tides, so over very long time periods (about 50 billion years more) the Earth and moon would slowly orbit closer and closer. Eventually they would merge into an (again) somewhat fast spinning body (still moving in the same direction!)

In the *really* long run tidal forces would slow this rotation so the big planet would be tidally locked to the sun. But again, the one-year rotation of the planet would be in the same direction as now.

There is a lot of nonsense claimed on the Internet. Learn the basic laws of physics like conservation of energy and momentum, get used to do rough calculations, and you can usually see through it quickly.


---

### Answer by username_13 on 2021-01-11. Score: 5

There is a lot of confusion in those articles.

The headline though is **The Earth won't start rotating backwards** and **The sun won't rise in the West**

1. Yes Mars and the other planets do move retrograde against the stars. This happens once every year-and-a-bit, and is a perspective effect. The Earth moves faster than Mars and so it can overtake it. When Earth overtakes Mars, it appears to be going backwards. But to be clear **Mars never actually goes backwards**, and **The orbit of the Earth never goes backwards**. So finally **The Sun will not rise in the west**. The rest of the first article is just how this would confirm prophecy, and contains no astronomy.
2. Is a copy-and-paste combination of 1 and 3
3. Yes, the Earth's magnetic poles do sometimes "flip", and quite quickly on a Geological scale, taking only a few thousand years. There is some reason to think that a flip might occur in the next 100,000 years or so. There is no particular reason to believe that a flip is imminant. During a flip the magnetic field would weaken, and there would be less protection from the sun, but in previous flips, exactly 0 animals went extinct as a result of the flip. And even if the magnetic poles flip, the rotational poles stay the same. So **The Sun will not rise in the West**
4. This article is a "What if". It considers various effects of the Earth changing direction. It states "the earth is not likely to spontaneously change directions" This might be the understatement of the decade. **It is absolutely impossible for the Earth to change direction unless willed to by God**. Nothing physical do this: not man, nor asteroid impact, nor aliens.

In short these are three unreliable sources. Please just forget.

> **Comments:**
> **username_14**: Respectfully, I think we should leave "God's will" out of Astronomy Stack Exchange.  We don't all share the same God belief, and I think it distracts us from the scientific arguments.  
> **username_13**: It is highly relevant to the OP's question; if you see the links 1 it is about how this will be a fulfillment of prophesy.  Whether you believe in God or not, I stand by the fact that It is absolutely impossible for the Earth to change direction unless willed to by God.  If you believe in an all powerful god or gods, then you believe that god can do this.  If you don't then I claim it is completely impossible.  I could have included "magic" but I thought this would be flippant in the context in which the OP asked the question.  

---

### Answer by username_14 on 2021-01-12. Score: 3

## Almost certainly not.

All available information seems to indicate that the Earth will probably not reverse it's spin direction before it ends. However, we don't have absolute certainty of this.

**Inner-planetary collisions**

There are numerical simulations indicating the "Existence of collisional trajectories of Mercury, Mars, and Venus with Earth" within 5 Gyr time-scales, published in Nature by [Laskar and Gastineau 2009](https://www.nature.com/articles/nature08096). These are based on the possibility of potential resonance orbits of the inner planets with Jupiter. Laskar was influential in showing that the Solar System is a mathematically chaotic system on large time scales. While the probability of inter-inner-planetary collisions was extremely low according to their simulations, $unlikely \ne impossible$. For certain grazing impacts, "angular momentum dominates" according to [Elkins-Tanton and Weiss 2016](https://arxiv.org/ftp/arxiv/papers/1810/1810.05797.pdf) as shown in one of the excellent figures from their paper:

[![enter image description here](https://i.sstatic.net/tofwj.png)](https://i.sstatic.net/tofwj.png)

A sufficiently energetic inter-planetary collision could certainly change Earth's spin direction and either merge, graze, or potentially strip the mantle.

**Exoplanetary collisions**

Also, I don't think we can rule out the possibility of a near miss of our Solar System with another stellar system within the Milky Way. We know that there are [some stars in retrograde galactic orbits that cross the Sun's prograde orbit](https://astronomy.stackexchange.com/questions/40718/is-there-a-retrograde-star-that-passes-closer-to-the-galactic-center-than-our-su) around the Milky Way. If our Solar System was to pass through the stellar system of a retrograde star, an Earth collision with an exoplanet would be possible.

**Notes:**

1. One could argue that after a planetary collision, the Earth's composition would be so changed that it would no longer be the Earth. We could consider another case in which our Moon was knocked out of Earth orbit by a collision. Then the obliquity of the Earth would vary up to about 85 degrees according to [Laskar et al.](https://www.nature.com/articles/361615a0). If another smaller Earth impact collision tipped the obliquity past 90 degrees, the Earth would indeed be spinning the opposite direction without much change to its composition.
2. The sources linked by the OP are not scientifically credible, but that doesn't mean we can rule out the possibility of their conclusions. Astronomy is still an incredibly vibrant and open field with many unanswered questions. I don't think we can be 100% certain that the Earth's spin direction will never change when we don't have a [universally accepted explanation for Venus's retrograde rotation](https://astronomy.stackexchange.com/questions/26/what-is-the-current-accepted-theory-as-to-why-venus-has-a-slow-retrograde-rotati).
3. I disagree with the heavy downvoting of the OP's question. They edited their post by adding links and their question is valid.


---

