So how fast are we actually moving?

[DaveC426913]

I guess ray has given us the required reference point. By 'The Big A' I presume he means 'The Great Attractor'.

So, the question becomes how fast are we moving toward the Great Attractor?

I think he also wants to know the orientation of the galaxy wrt our movement towards the GA, and the orientation of the SS wrt the galaxy.

 

[marcus]

still want a speed and direction

the speed and direction were measured by George Smoot Berkeley team quite a long time ago and have been confirmed ever since as more and more data comes in

but he was already on the money as of around 1977!

and he didn't even need a satellite or anything, he did it (or his team did it) just using U-2 spyplane aircraft. Flying out of Moffat field near SF, and also out of someplace in Peru

beautiful measurements with simple resources. maybe i can get a link

 

[marcus]

Whoah! Ned Wright says that some other people measured it using balloon-borne instrument even before Smoot's team did it with U2 aircraft.

http://www.astro.ucla.edu/~wright/CMB-dipole-history.html

But on brief inspection it looks like the earlier team was somewhat off on the speed. Smoot got very close to the figure later confirmed by COBE (1990s) and WMAP (2000s) satellite measurments.

I'll try to find the Smoot website with the U2 pictures.
Here is a Smoot U2 page
http://aether.lbl.gov/www/projects/u2/
NOTICE THE STAR MAP WITH THE CONSTELLATION LEO

In any case the DIRECTION of the solar system's travel is the same direction as currently occupied by the constellation Leo. It is away from the Great Attractor, which is kind of irrelevant as a landmark. Of course we are orbiting Milky center, and Milky is part of Local Group and Local group is falling towards Virgo Cluster and Virgo Cluster is falling towards HydraCentaurus direction "Attractor" but all those complicated motions are not what matters. and not what cosmologists want to know when they have to adjust measurments to compensate for solarsystem motion.

When cosmologists compensate for solar system motion the vector they use is approx 368 km/sec in direction of Leo (you can find the precise coords in Ned Wright site)

and that was what Smoot found with the U2 aircraft (approximately)

 

[marcus]

Back in 2003 I was discussing this kind of thing with, among others, Chroot and I wanted to know how fast Milky was going towards the Great Attractor or in the Hydra-Centaurus direction.

So I hunted around and found a peer-review journal article that gave coordinates and a speed IIRC around 600 km per second.

I posted the figure and the link.

But that does not mean that Milky is approaching Big A at 600 clicks!

In largescale astronomy speeds are typically relative to the CMB

The astronomers had determined that Milky, or the Local Group which is roughly the same speed, is going IN A CERTAIN DIRECTION AT A SPEED OF 600 CLICKS RELATIVE TO CMB.

That doesn't tell about our speed relative to Big A, because Big A itself could be moving in any direction whatever and we wouldn't know.

So Big A, or the Virgo Cluster, or whatever is a BAD LANDMARK and most of the time people simply do not use it.

Another thing I found out was that Milky and the Local Group are not actually moving towards the Great Attractor! Only very roughly. they are not even headed anywhere in the constellations of Hydra and Centaurus!

The coordinates of Local Group velocity vector are in a small Southern constellation called Crater, the drinking cup.

That is something you can see in the sky, in our latitude, in the summer.
and it marks the direction that our Local Fleet of a dozen or so galaxies is really going.

 

[Chronos]

Full circle?

 

[marcus]

Full circle?

Not quite full circle. Nobody like Chroot
I found a PF reference:
https://www.physicsforums.com/archive/index.php/t-41717.html

(EDIT here's another PF reference---January 2004 post, one or the other of these links should work
https://www.physicsforums.com/showthread.php?p=137931#post137931
https://www.physicsforums.com/showthread.php?p=137931&posted=1#post137931 )

The Local Group speed is about 600 km/second as measured by Smoot et al (recent Nobel for this kind of work)

==quote from a September post of mine==

hello king, you should have asked the direction as well
I have a fairly recent (2002) online source that may help.
http://arxiv.org/astro-ph/0210165

This source is a journal article (Phys. Rev. Series D, 2003) reporting an earlier measurment (Smoot et al) of the speed and direction of the Local Group (as usual wrt CMB)
the result IIRC is that motion is in direction of the constellation Crater
(a small faint constell in southern half of sky) or if you want a brighter marker try Corvus. And it gives the speed as 627+/-22 km/sec.
Part of this could be due, instead, to temperature fluctuation in the CMB itself but not enough to affect the rough idea of about 600 km/s.

the motion of Milky Way wrt center of mass of Local Group is small. It would not be too bad an approximation just to say equate Milky's speed wrt CMB and that of the Local Group. So one can say Milky is going about 600 km/s and in the direction of constellation Crater.

(the constellation stars just mark the direction in space, the other stars in the galaxy are not getting closer to them because they are moving along with the galaxy as well)

...
...
the celestial coords given for the Local Group velocity vector are
276 degrees, -33 degrees
so it is in the south hemisphere but not as far south as people usually associate with hydra and centaurus. the "Great Attractor" is in hydra/centaurus. therefore Local Group is not plunging directly at the Great Attractor. Virgo cluster might be, I don't know for sure, but Local deviates a bit from that.

==endquote==

BTW the orientation of the Galaxy as it moves in the Crater direction is sort of like a sailing Frisbee----a little tilted but roughly speaking the direction of motion is approximately in the galaxtic plane. (it's more that than it is parallel to the rotation axis)

 

[Ballon]

Absolut speed of 0, does exist, this is the speed of an object relative to itself...speed are always relative to a frame of reference.

 

[whipnet]

So this is a "physics forum" and no one corrected the OP who thinks the Earth is orbiting around the sun at 30,000 mph?

*

 

[Stratosphere]

So this is a "physics forum" and no one corrected the OP who thinks the Earth is orbiting around the sun at 30,000 mph?

*

Wow I'm surprised no one noticed that, the Earth is traveling at 66,622.17 mph.

 

[DaveC426913]

Absolut speed of 0, does exist, this is the speed of an object relative to itself...speed are always relative to a frame of reference.

This is directly contradictory. Relative speed is not absolute speed.

 

[ray b]

This is directly contradictory. Relative speed is not absolute speed.

two and a half years and still no answer but lots of quibbles
speed of the milky way/local group was given in the first post
how much does the sun motion in the milky way add or subtract to our
movement in one years time plus any other movments

we have known the Earth's speed around the sun
but cancel that as we are talking about a year
so that doesnot matter

the suns speed and direction in its orbit
the milky ways speed and direction in its local group orbit
speed and direction of the motion of the whole local group

THATS THREE VECTORS and SPEEDS
unless there is some other factor
that I am missing
so far we have one vector and speed
please no more quibbles
how about just some data
so HOW FAR DO WE [earth/sun] move in a year
and in what direction

 

[DaveC426913]

THATS THREE VECTORS and SPEEDS
unless there is some other factor
that I am missing
so far we have one vector and speed
please no more quibbles
how about just some data
so HOW FAR DO WE [earth/sun] move in a year
and in what direction

Two and a half years since it was first answered (in post #2), and still some people are failing to grasp that the question is ambiguous.

How fast are we moving relative to what?

 

[Quantum_Grid]

Relative to the speed at which this thread is advancing, aka absolute zero time...

 

[ray b]

Two and a half years since it was first answered (in post #2), and still some people are failing to grasp that the question is ambiguous.

How fast are we moving relative to what?

for the 3rd time
the Earth sun position one year ago or one year from now
relative to nothing else
just how far do we move in a year and in what direction
btw your are QUIBBLEING
I SAID NO QUIBBLES
so post some vectors or you are not adding anything at all

 

[Chronos]

Any 'position' is always relative to some landmark, some coordinate system. It appears you are asking for an absolute coordinate system, ray b, where none exists. The CMB reference frame is as good as it gets. I do not see how this is quibbling. We can, of course, deduce our relative postion with respect to some arbitrarily selected galaxies, or even stars within our own galaxy. Neither approach will produce entirely satisfactory results.

 

[DaveC426913]

btw your are QUIBBLEING
I SAID NO QUIBBLES

We are not quibbling. There is no answer to the question without a reference point.

We are moving relative to the galaxy, which is moving relative to our local group, which is moving relative to our supercluster, which is moving relative to ... what?

It is possible to give you a vector that tells us how we are moving relative to our local supercluster, but that is still relative to some reference point. We do not know what our supercluster is doing because there is no absolute reference frame.


Now stop being so churlish and accept that we're not just jerking your chain. We kind of know a little about this.




P.S. I want to request a new emoticon: : yourarequibblingIsaidnoquibbles :

 

[Quantum_Grid]

P.S. I want to request a new emoticon: : yourarequibblingIsaidnoquibbles :

hahaha

 

[Quantum_Grid]

Also, this may have been said already, but this is taken from "The Big Bang" by Joseph Silk:

The actual measured velocity of the Earth relative to the background radiation is only 390 kilometers/sec; the higher velocity for our galaxy results when account is taken of the Earth's motion around the sun (30 km/s), the solar motion around the galactic center (220 km/s), and the motion of the Milky Way toward the Andromeda galaxy in the local group of galaxies (100 km/s). The net direction of the Local Group's center of mass velocity is about 45 degrees away from the Virgo Cluster, consequently, when account is taken for the Local Group infall, the entire Virgo supercluster is inferred to be moving at a velocity of about 400 kilometers per second toward a region in the southern sky where the Hydra and Centaurus clusters are located. (The Big Bang, by Joseph Silk, p53​

)

 

[Quantum_Grid]

So, ray b, THE BEST ANSWER YOU ARE GOING TO GET: is 390 kilometers/sec.

Now, no more quibbles!

 

[ray b]

yes space is growing and everything is moving too so what
there is no fixed grid again so what
I simply made one up

BUT I still don't get why a dated Earth position at x=0 y=0 and z = 0 grid
line the x-axis with the suns motion in orbit around our galixcy's center
and y=90 degrees to x, z points as near as possible to north
wait a full year to cancel Earth orbit movement and where are we NOW
does not give a true reference frame to chart a new location for the earth
after a year has past
and a simple answer to the question of what is our speed and direction

I do understand everything else has moved to
and there is no center of the universe point
but why can't our motion be grafted
with a pick a point now and wait a year reference

 

[Brain Dwarf]

Your planet is moving at a rate of 1.17936 condules per rotation, and is in danger of wandering into intergalatic transform tube 17A - you are advised to change course immediately or you may be sturgwolled by a passing freighter, you will receive no further warnings.

 

[Integral]

How do you mark that spot?

 

[DaveC426913]

yes space is growing and everything is moving too so what
there is no fixed grid again so what
I simply made one up

BUT I still don't get why a dated Earth position at x=0 y=0 and z = 0 grid
line the x-axis with the suns motion in orbit around our galixcy's center
and y=90 degrees to x, z points as near as possible to north
wait a full year to cancel Earth orbit movement and where are we NOW
does not give a true reference frame to chart a new location for the earth
after a year has past
and a simple answer to the question of what is our speed and direction

I do understand everything else has moved to
and there is no center of the universe point
but why can't our motion be grafted
with a pick a point now and wait a year reference

OK, so you mentioned our galaxy's center. Is that what you'd like to use as your frame of reference? You could calculate our movement around the sun and the sun's movemnt through the galaxy with the galaxy as the non-rotating reference point.

Of course, it would ignore any movement of our galaxy within the cluster...



All that aside, you won't get a very useful answer. The sum of these vectors means very little. Picture a marble in a roulette wheel that is in the back of a van driving down a north-running street. You are asking for the position of the marble after ten seconds - summing the movement of the marble on the roulette wheel with the movement of the van down the road, with reference to some point outside the van. OK, so in ten seconds the marble has moved pi radians clockwise and 100 yards north, or something like 100.05 yards North-by-northwest.

 

[DaveC426913]

How do you mark that spot?

Good one, good one.

 

[ray b]

How do you mark that spot?

in your mind
anyone really think you can draw an X in space
or that there is any need to
nobodys going to meassure back to it anyway
no you just set the X Y & Z at zero and see how far away
the Earth travels in a year

I really doNOT see what's so hard to grasp here

 

[Quantum_Grid]

Ok well we have already established that we are moving at 390km/s. There are 31,557,000 (about) seconds in a year. So after one year, the Earth has moved 12,307,230,000 kilometers.

Hows that?

 

[Quantum_Grid]

or 33.7 million kilometers a day

 

[Chronos]

Well, ray, marking an 'X' in 'space' is the essence of your original argument. We argued this is a purely arbitrary [and meaningless] exercise. Sounds like you are shifting the goal posts.

 

[DaveC426913]

in your mind
anyone really think you can draw an X in space
or that there is any need to
nobodys going to meassure back to it anyway
no you just set the X Y & Z at zero and see how far away
the Earth travels in a year

I really doNOT see what's so hard to grasp here

Ray, how do you ensure that your X is not moving? If we did this for real, we'd be in orbit (around the sun, if not around the Earth) and when we dropped the X it too would be in orbit. We would have to apply a counter-force to "bring it to rest". But we don't know what "rest" is. No matter what thought experiment you devise to drop the X and bring it to rest, there is no way even in principle of making it stop without us knowing what "stop" is, and then applying forces to bring it there.

Thus is the nature of "[URL first law[/URL]. As we sail through space, we have no way of determining that we are moving except in relation to some chosen reference point.

 

[Quantum_Grid]

Ok well we have already established that we are moving at 390km/s. There are 31,557,000 (about) seconds in a year. So after one year, the Earth has moved 12,307,230,000 kilometers.

Hows that?

Isn't this the answer he is looking for? Can we not consider this matter closed? In the words of ray b, can we stop the "quibbles"