How fast are we moving relative to the CMB?How thick is the cosmic microwave background, including the part we cannot see within the observable universe?Understanding The Fluctuations In The CMB Maps
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How fast are we moving relative to the CMB?
How thick is the cosmic microwave background, including the part we cannot see within the observable universe?Understanding The Fluctuations In The CMB Maps
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The cosmic microwave background radiation should provide kind of a global reference frame, because you can determine your speed relative to it using the redshift.
Is it known how fast we are moving in relation to the CMB? If you subtract the various orbital motions (Earth around the Sun, Sun around the Galaxy), are we standing still in the expanding universe, or traveling in a certain direction?
cosmic-microwave-background
asked Sep 27 at 12:27
cuckoocuckoo
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add a comment
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$begingroup$
The cosmic microwave background radiation should provide kind of a global reference frame, because you can determine your speed relative to it using the redshift.
Is it known how fast we are moving in relation to the CMB? If you subtract the various orbital motions (Earth around the Sun, Sun around the Galaxy), are we standing still in the expanding universe, or traveling in a certain direction?
cosmic-microwave-background
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
$endgroup$
1
$begingroup$
This is known as galactic peculiar velocity: en.wikipedia.org/wiki/Peculiar_velocity
$endgroup$
– David Tonhofer
Sep 29 at 8:50
add a comment
|
$begingroup$
The cosmic microwave background radiation should provide kind of a global reference frame, because you can determine your speed relative to it using the redshift.
Is it known how fast we are moving in relation to the CMB? If you subtract the various orbital motions (Earth around the Sun, Sun around the Galaxy), are we standing still in the expanding universe, or traveling in a certain direction?
cosmic-microwave-background
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
$endgroup$
The cosmic microwave background radiation should provide kind of a global reference frame, because you can determine your speed relative to it using the redshift.
Is it known how fast we are moving in relation to the CMB? If you subtract the various orbital motions (Earth around the Sun, Sun around the Galaxy), are we standing still in the expanding universe, or traveling in a certain direction?
cosmic-microwave-background
cosmic-microwave-background
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
asked Sep 27 at 12:27
cuckoocuckoo
4661 silver badge5 bronze badges
4661 silver badge5 bronze badges
1
$begingroup$
This is known as galactic peculiar velocity: en.wikipedia.org/wiki/Peculiar_velocity
$endgroup$
– David Tonhofer
Sep 29 at 8:50
add a comment
|
1
$begingroup$
This is known as galactic peculiar velocity: en.wikipedia.org/wiki/Peculiar_velocity
$endgroup$
– David Tonhofer
Sep 29 at 8:50
1
1
$begingroup$
This is known as galactic peculiar velocity: en.wikipedia.org/wiki/Peculiar_velocity
$endgroup$
– David Tonhofer
Sep 29 at 8:50
$begingroup$
This is known as galactic peculiar velocity: en.wikipedia.org/wiki/Peculiar_velocity
$endgroup$
– David Tonhofer
Sep 29 at 8:50
add a comment
|
1 Answer
1
active
oldest
votes
$begingroup$
Yes, our (i.e. the Sun's) motion in the "global", or comoving, reference frame can be measured accurately from the dipole of the cosmic microwave background. The latest results from the Planck Collaboration et al. (2018) yielded a velocity of
$$369.82pm0.11,mathrmkm,mathrms^-1
$$
in the direction
$$
beginarrayrcl
ell & = & 264.021ºpm0.011º\
b & = & 48.253ºpm0.005º
endarray
$$
(in Galactic coordinates).
Since Earth orbits the Sun with some $30,mathrmkm,mathrms^-1$, there's a small, biannual correction to this result. On much larger timescales ($sim100,mathrmMyr$) our motion round the Milky Way alters our comoving velocity with the order of $sim100,mathrmkm,mathrms^-1$.
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
$endgroup$
1
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
3
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
4
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
5
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
2
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
|
show 11 more comments
Your Answer
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1 Answer
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active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Yes, our (i.e. the Sun's) motion in the "global", or comoving, reference frame can be measured accurately from the dipole of the cosmic microwave background. The latest results from the Planck Collaboration et al. (2018) yielded a velocity of
$$369.82pm0.11,mathrmkm,mathrms^-1
$$
in the direction
$$
beginarrayrcl
ell & = & 264.021ºpm0.011º\
b & = & 48.253ºpm0.005º
endarray
$$
(in Galactic coordinates).
Since Earth orbits the Sun with some $30,mathrmkm,mathrms^-1$, there's a small, biannual correction to this result. On much larger timescales ($sim100,mathrmMyr$) our motion round the Milky Way alters our comoving velocity with the order of $sim100,mathrmkm,mathrms^-1$.
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
$endgroup$
1
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
3
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
4
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
5
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
2
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
|
show 11 more comments
$begingroup$
Yes, our (i.e. the Sun's) motion in the "global", or comoving, reference frame can be measured accurately from the dipole of the cosmic microwave background. The latest results from the Planck Collaboration et al. (2018) yielded a velocity of
$$369.82pm0.11,mathrmkm,mathrms^-1
$$
in the direction
$$
beginarrayrcl
ell & = & 264.021ºpm0.011º\
b & = & 48.253ºpm0.005º
endarray
$$
(in Galactic coordinates).
Since Earth orbits the Sun with some $30,mathrmkm,mathrms^-1$, there's a small, biannual correction to this result. On much larger timescales ($sim100,mathrmMyr$) our motion round the Milky Way alters our comoving velocity with the order of $sim100,mathrmkm,mathrms^-1$.
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
$endgroup$
1
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
3
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
4
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
5
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
2
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
|
show 11 more comments
$begingroup$
Yes, our (i.e. the Sun's) motion in the "global", or comoving, reference frame can be measured accurately from the dipole of the cosmic microwave background. The latest results from the Planck Collaboration et al. (2018) yielded a velocity of
$$369.82pm0.11,mathrmkm,mathrms^-1
$$
in the direction
$$
beginarrayrcl
ell & = & 264.021ºpm0.011º\
b & = & 48.253ºpm0.005º
endarray
$$
(in Galactic coordinates).
Since Earth orbits the Sun with some $30,mathrmkm,mathrms^-1$, there's a small, biannual correction to this result. On much larger timescales ($sim100,mathrmMyr$) our motion round the Milky Way alters our comoving velocity with the order of $sim100,mathrmkm,mathrms^-1$.
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
$endgroup$
Yes, our (i.e. the Sun's) motion in the "global", or comoving, reference frame can be measured accurately from the dipole of the cosmic microwave background. The latest results from the Planck Collaboration et al. (2018) yielded a velocity of
$$369.82pm0.11,mathrmkm,mathrms^-1
$$
in the direction
$$
beginarrayrcl
ell & = & 264.021ºpm0.011º\
b & = & 48.253ºpm0.005º
endarray
$$
(in Galactic coordinates).
Since Earth orbits the Sun with some $30,mathrmkm,mathrms^-1$, there's a small, biannual correction to this result. On much larger timescales ($sim100,mathrmMyr$) our motion round the Milky Way alters our comoving velocity with the order of $sim100,mathrmkm,mathrms^-1$.
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
answered Sep 27 at 13:41
pelapela
21.9k50 silver badges76 bronze badges
21.9k50 silver badges76 bronze badges
1
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
3
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
4
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
5
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
2
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
|
show 11 more comments
1
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
3
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
4
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
5
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
2
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
1
1
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
$begingroup$
How can the Planck results be precise to 0.11 km/s if there's a 60 km/s correction depending on the time of the year?
$endgroup$
– Allure
Sep 27 at 22:27
3
3
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
$begingroup$
@Allure: The Earth's orbital velocity around the Sun is quite well known already. And even if it wasn't, they could just average it out over a whole year (or several).
$endgroup$
– Ilmari Karonen
Sep 27 at 22:30
4
4
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
$begingroup$
@Allure Yes, exactly; that's why I wrote "our (i.e. the Sun's)" :)
$endgroup$
– pela
Sep 28 at 6:36
5
5
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
$begingroup$
@nick012000 Because what you've said isn't true. The small departure from this isotropy is what leads to the measurement quoted in the answer.
$endgroup$
– Rob Jeffries
Sep 28 at 11:46
2
2
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
$begingroup$
@nick I'm sure you've seen CMB images like this, which show that the CMB is isotropic to better than one part in 10,000. Such images have been corrected for our peculiar motion; otherwise, the CMB details would be swamped by the Doppler effect of the peculiar motion. A raw map of the CMB (i.e., without that correction), looks like this.
$endgroup$
– PM 2Ring
Sep 29 at 9:41
|
show 11 more comments
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$begingroup$
This is known as galactic peculiar velocity: en.wikipedia.org/wiki/Peculiar_velocity
$endgroup$
– David Tonhofer
Sep 29 at 8:50