<p>If you see the same meteor, it of course only has one path - even while the apparent movement differs for different observers. What you basically do in that case is <a href="https://en.wikipedia.org/wiki/Triangulation_(surveying)" rel="noreferrer">triangulation</a> - which you could use with your known geographic location (and time for the observations, and the direction horizontally and vertically) reconstruct the flight path. That's a method which actually is used to identify meteors and and tracking them, e.g. via the <a href="https://en.wikipedia.org/wiki/European_Fireball_Network" rel="noreferrer">fireball network</a>.</p>
<hr />
<p>Is it possible that you saw the meteor given your geographic separation?
(note 11 March: This paragraph is heavily revised and comes to the opposite conclusion with the right trigonometry)</p>
<p>Given the mentioned separation between Norway and Spain, we talk of a few thousand kilometres. The typical height at which you see a meteor is between 50 and 100km. The curvature of Earth then makes sure you don't see the same meteor when you are too far apart - but it might be still just right here:</p>
<p>Madrid and Oslo are about 2000km apart, the Earth's circumference is about 40000km. The earth's radius is <span class="math-container">$r_E = 6371$</span>km which allows us to calculate the angle <span class="math-container">$\alpha$</span> between those as seen from Earth's centre: <span class="math-container">$\alpha = 0.31$</span> (radians). With that angle we can calculate the height an object must be at when we look horizontally and just see it at the horizon (laying on the floor makes it easy to calculate), given it's separated by the angle <span class="math-container">$\alpha$</span>:</p>
<p><a href="https://i.sstatic.net/qFPLc.png" rel="noreferrer"><img src="https://i.sstatic.net/qFPLc.png" alt="image with angle and distances. h:height, rE: earth radius, alpha: angle" /></a></p>
<p><span class="math-container">$$
d_s = r_E\cdot tan\alpha
$$</span>
and
<span class="math-container">$$
\frac{h+r_e}{\sin 90°} = \frac{d_s}{\sin\alpha} = \frac{r_e\tan\alpha}{\sin\alpha} = \frac{r_E}{\cos\alpha} = r_E \sec\alpha
$$</span>
so that
<span class="math-container">$$
h = \frac{r_E}{\cos\alpha}-r_E
$$</span>
Now if you enter the angle between Oslo and Madrid you get a height of about 79km for an object passing half-way (thus at half the angle to each). So it might have been that very same meteor if it was very close to the local horizon. Given that this estimation is pessimistic as it ignores observer height, things get a bit better if you assume that you stand on your feet, on a building or even a mountain. Either way, the meteor will have been close to the horizon for both of you, and very likely for one travelling left to right, for the other observer right to left.</p>

CC BY-SA 4.0
2021-03-11T07:47:17.670Z
This formula is incorrect, the correct formula should be `h = r_E (sec(\alpha / 2) - 1)` to get the minimum height of an object that would be visible by two observers separated by an angle alpha. Plugging the numbers in for this situation gives a minimum altitude of ~70 km.
Kyle
CC BY-SA 4.0
2021-03-11T08:47:27.893Z
@Kyle you are so right! And it somewhat changes the answer. I actually noticed during breakfast and was just editing it when you wrote your comment. Thanks :)
planetmaker
CC BY-SA 4.0
2021-03-10T14:53:38.973Z
2021-03-11T08:45:15.957Z
2021-03-11T08:45:15.957Z
planetmaker
<p>Yes, if the object is moving between the two of you then your reference systems are different. For example two people standing on opposite sides of a river. One sees it flowing from left to right, the other sees it flowing from right to left.</p>
<p>The river, or meteor, has not itself changed direction, but you'll each describe the direction differently if you're using spatial reference systems relative to yourself.</p>

CC BY-SA 4.0
2021-03-11T03:01:17.940Z
This seems similar to the other existing answers. What makes yours different?
slowerthanstopped
CC BY-SA 4.0
2021-03-11T07:31:02.070Z
@slowerthanstopped I think it is much simpler to visualise something on the scale of a river which is clearly flowing one way without having to deal with compass directions or geography. I judged the target audience as needing something that makes it very clear in layman's terms
Craig
CC BY-SA 4.0
2021-03-11T02:08:17.487Z
2021-03-11T02:08:17.487Z
Craig
<p>Yes, but it depends on your reference system.  If the meteor was moving East to West over England, it would appear to be going Left to Right from Norway, but Right to Left from Spain.</p>

CC BY-SA 4.0
2021-03-11T03:41:11.430Z
This is a good supplemental point, and by extension, this can apply to a single person standing (or laying down) an looking straight up. It could be left-right or right-left or even forward or backward (up or down).
uhoh
CC BY-SA 4.0
2021-03-10T14:47:42.860Z
2021-03-10T14:47:42.860Z
Connor Garcia
<p>No, they do not change direction when they pass over country borders or latitude. It is just based on where your positions are relative to the meteor.</p>

CC BY-SA 4.0
2021-03-11T04:26:55.863Z
"Papers, please?"  I would not want to encounter customs officers with such powers.
Camille Goudeseune
CC BY-SA 4.0
2021-03-10T14:01:23.703Z
2021-03-10T14:01:23.703Z
WarpPrime
<p>So here is the question me and a friend of mine from Norway we saw a meteor but que said he saw it in the opposite direction as me and I was looking from spain, does that make any sense? Or we should see it going the same direction? Thanks in advance</p>

CC BY-SA 4.0
2021-03-10T13:32:02.633Z
Welcome to astronomy SE! Please edit in more details: In which direction did he see it, in which direction did you see it?
B--rian
CC BY-SA 4.0
2021-03-10T14:20:49.763Z
If you were 100 km from the North pole but on opposite sides of it and it passed directly over the pole, then one of you would see easterly motion and the other westerly.. Otherwise, I don't think it's possible.
uhoh
CC BY-SA 4.0
2021-03-11T03:20:02.853Z
Maybe you were just looking the opposite direction.
9pfs
CC BY-SA 4.0
2021-03-11T03:45:56.320Z
...assuming "direction" is azimuth (e.g.south, west, east, north...) but answers now explain that if it's left-right the answer can be different. You haven't specified how the observers report direction yet.
uhoh
<meteor>
Does a meteor's direction change between country or latitude?
user38404
# Does a meteor's direction change between country or latitude?

(Asked by: username_0 on 2021-03-10)

So here is the question me and a friend of mine from Norway we saw a meteor but que said he saw it in the opposite direction as me and I was looking from spain, does that make any sense? Or we should see it going the same direction? Thanks in advance

**Tags:** meteor

> **Comments:**
> **username_1**: Welcome to astronomy SE! Please edit in more details: In which direction did he see it, in which direction did you see it?  
> **username_2**: If you were 100 km from the North pole but on opposite sides of it and it passed directly over the pole, then one of you would see easterly motion and the other westerly.. Otherwise, I don't think it's possible.  
> **username_3**: Maybe you were just looking the opposite direction.  
> **username_2**: ...assuming "direction" is azimuth (e.g.south, west, east, north...) but answers now explain that if it's left-right the answer can be different. You haven't specified how the observers report direction yet.  

---

## 4 answers

### Answer by username_4 on 2021-03-10. Score: 40

If you see the same meteor, it of course only has one path - even while the apparent movement differs for different observers. What you basically do in that case is [triangulation](https://en.wikipedia.org/wiki/Triangulation_(surveying)) - which you could use with your known geographic location (and time for the observations, and the direction horizontally and vertically) reconstruct the flight path. That's a method which actually is used to identify meteors and and tracking them, e.g. via the [fireball network](https://en.wikipedia.org/wiki/European_Fireball_Network).

---

Is it possible that you saw the meteor given your geographic separation?
(note 11 March: This paragraph is heavily revised and comes to the opposite conclusion with the right trigonometry)

Given the mentioned separation between Norway and Spain, we talk of a few thousand kilometres. The typical height at which you see a meteor is between 50 and 100km. The curvature of Earth then makes sure you don't see the same meteor when you are too far apart - but it might be still just right here:

Madrid and Oslo are about 2000km apart, the Earth's circumference is about 40000km. The earth's radius is $r\_E = 6371$km which allows us to calculate the angle $\alpha$ between those as seen from Earth's centre: $\alpha = 0.31$ (radians). With that angle we can calculate the height an object must be at when we look horizontally and just see it at the horizon (laying on the floor makes it easy to calculate), given it's separated by the angle $\alpha$:

[![image with angle and distances. h:height, rE: earth radius, alpha: angle](https://i.sstatic.net/qFPLc.png)](https://i.sstatic.net/qFPLc.png)

$$
d\_s = r\_E\cdot tan\alpha
$$
and
$$
\frac{h+r\_e}{\sin 90°} = \frac{d\_s}{\sin\alpha} = \frac{r\_e\tan\alpha}{\sin\alpha} = \frac{r\_E}{\cos\alpha} = r\_E \sec\alpha
$$
so that
$$
h = \frac{r\_E}{\cos\alpha}-r\_E
$$
Now if you enter the angle between Oslo and Madrid you get a height of about 79km for an object passing half-way (thus at half the angle to each). So it might have been that very same meteor if it was very close to the local horizon. Given that this estimation is pessimistic as it ignores observer height, things get a bit better if you assume that you stand on your feet, on a building or even a mountain. Either way, the meteor will have been close to the horizon for both of you, and very likely for one travelling left to right, for the other observer right to left.

> **Comments:**
> **username_5**: This formula is incorrect, the correct formula should be `h = r_E (sec(\alpha / 2) - 1)` to get the minimum height of an object that would be visible by two observers separated by an angle alpha. Plugging the numbers in for this situation gives a minimum altitude of ~70 km.  
> **username_4**: @username_5 you are so right! And it somewhat changes the answer. I actually noticed during breakfast and was just editing it when you wrote your comment. Thanks :)  

---

### Answer by username_8 on 2021-03-10. Score: 18

Yes, but it depends on your reference system. If the meteor was moving East to West over England, it would appear to be going Left to Right from Norway, but Right to Left from Spain.

> **Comments:**
> **username_2**: This is a good supplemental point, and by extension, this can apply to a single person standing (or laying down) an looking straight up. It could be left-right or right-left or even forward or backward (up or down).  

---

### Answer by username_6 on 2021-03-11. Score: 13

Yes, if the object is moving between the two of you then your reference systems are different. For example two people standing on opposite sides of a river. One sees it flowing from left to right, the other sees it flowing from right to left.

The river, or meteor, has not itself changed direction, but you'll each describe the direction differently if you're using spatial reference systems relative to yourself.

> **Comments:**
> **username_7**: This seems similar to the other existing answers. What makes yours different?  
> **username_6**: @username_7 I think it is much simpler to visualise something on the scale of a river which is clearly flowing one way without having to deal with compass directions or geography. I judged the target audience as needing something that makes it very clear in layman's terms  

---

### Answer by username_9 on 2021-03-10. Score: 3

No, they do not change direction when they pass over country borders or latitude. It is just based on where your positions are relative to the meteor.

> **Comments:**
> **username_10**: "Papers, please?"  I would not want to encounter customs officers with such powers.  

---

