ChatterBank1 min ago
What part of the universe is expanding ?
We believe the universe is expanding but what does that mean ?
Our solar system is not expanding . Our sun and all the planets are all the same distance from each other as they have been for thousands of years so no movement there. Similarly I believe all the stars in our galaxy are not changing their distance from each other or am I mistaken ?
If all other galaxies are similarly stable I can only assume the term expanding universe can only apply to the distance between the galaxies.
Can someone clarify the position.
Our solar system is not expanding . Our sun and all the planets are all the same distance from each other as they have been for thousands of years so no movement there. Similarly I believe all the stars in our galaxy are not changing their distance from each other or am I mistaken ?
If all other galaxies are similarly stable I can only assume the term expanding universe can only apply to the distance between the galaxies.
Can someone clarify the position.
Answers
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(3) Is the Earth expanding with the universe?
The Earth is not expanding and neither is the solar system, nor the Milky Way galaxy. These objects formed under the influence of gravity and stopped moving apart. Gravity also holds galaxies together into groups and clusters. It is mainly the groups and clusters of galaxies that are moving apart in the universe.
from http://
The Earth is not expanding and neither is the solar system, nor the Milky Way galaxy. These objects formed under the influence of gravity and stopped moving apart. Gravity also holds galaxies together into groups and clusters. It is mainly the groups and clusters of galaxies that are moving apart in the universe.
from http://
Interesting link from Rojash.
However, its my understanding that cosmic expansion does happen everywhere, even within the solar system - but you have other, competing forces that are far more influential on a local scale, such as the gravitational pull of the sun and the other planets.
I seem to be remember reading something to the effect ( from a link, provided below) that the influence of the cosmological expansion on the Earth's orbit around the Sun amounts to a growth by only one part in a septillion over the age of the Solar System - so negligible, and virtually impossible to observe, I would have thought :)
There is also a growth effect on the earths orbit due to mass loss of the Sun, but this obviously has nothing to do with cosmic expansion.
Cosmic expansion is something that can be observed on a galactic scale, but within galaxies and clusters, such expansionary forces are tempered by local gravitational forces.
http://
However, its my understanding that cosmic expansion does happen everywhere, even within the solar system - but you have other, competing forces that are far more influential on a local scale, such as the gravitational pull of the sun and the other planets.
I seem to be remember reading something to the effect ( from a link, provided below) that the influence of the cosmological expansion on the Earth's orbit around the Sun amounts to a growth by only one part in a septillion over the age of the Solar System - so negligible, and virtually impossible to observe, I would have thought :)
There is also a growth effect on the earths orbit due to mass loss of the Sun, but this obviously has nothing to do with cosmic expansion.
Cosmic expansion is something that can be observed on a galactic scale, but within galaxies and clusters, such expansionary forces are tempered by local gravitational forces.
http://
Strange isn't it.
Years ago most people were only really interested in what went on in their street.
Then as we got better communication they wondered what went on in their town, then their country.
Then a few years ago, as we got better news media, and the internet came along, we wondered what went on all over the world.
Now comunication has improved so much we wonder if the universe is expanding.
That is a hell of a lot of stuff for us to "worry" about.
Years ago most people were only really interested in what went on in their street.
Then as we got better communication they wondered what went on in their town, then their country.
Then a few years ago, as we got better news media, and the internet came along, we wondered what went on all over the world.
Now comunication has improved so much we wonder if the universe is expanding.
That is a hell of a lot of stuff for us to "worry" about.
The entire universe is expanding - it's just that at the scales of the Solar system we don't notice it any more than we notice he weight of an ant on a car.
The weight of all the ants in the world would crush your car.
Some numbers may help
The Universe is expanding at a rate of 22.7-km/sec for each million light years
the solar system is about 5 light hours in size meaning that it expands at about 0.00000004 km/s (by my reconing ( I might have missed a decimal point!)
The nearest star 4 light years is similarly un measurable
The nearby Andromeda galaxy is 2.4 Million light years away so that's expanding at just 50KM/sec or so away from us
But the furthest objects are some 28 Billion light years from us they will be receding at some 600,000 Km/Sec
It's all a matter of grasping the incredible scale of the Universe - and that's difficult!
The weight of all the ants in the world would crush your car.
Some numbers may help
The Universe is expanding at a rate of 22.7-km/sec for each million light years
the solar system is about 5 light hours in size meaning that it expands at about 0.00000004 km/s (by my reconing ( I might have missed a decimal point!)
The nearest star 4 light years is similarly un measurable
The nearby Andromeda galaxy is 2.4 Million light years away so that's expanding at just 50KM/sec or so away from us
But the furthest objects are some 28 Billion light years from us they will be receding at some 600,000 Km/Sec
It's all a matter of grasping the incredible scale of the Universe - and that's difficult!
<<The nearby Andromeda galaxy is 2.4 Million light years away so that's expanding at just 50KM/sec or so away from us>> I understand that Andromeda is on a collision course with us so presumably is moving towards us faster than the expansion is moving it away? and.....what is the force making it move towards us?
Galaxies all have their own "proper" motion which is independant to the expansion of the Universe mostly driven by gravity.
The nearby Andromeda Galaxy is as you say coming towards us faster than the expansion of the Universe is carrying it away
In a similar way stars have their own proper motion as well as their rotation around the galactic centre
The nearby Andromeda Galaxy is as you say coming towards us faster than the expansion of the Universe is carrying it away
In a similar way stars have their own proper motion as well as their rotation around the galactic centre
As a corolllary for jake's reference, if you'd care to measure it yourselves, use this:
"Hubble's second revolutionary discovery was based on comparing his measurements of the Cepheid-based galaxy distance determinations with measurements of the relative velocities of these galaxies. He showed that more distant galaxies were moving away from us more rapidly:
v = Hod
where v is the speed at which a galaxy moves away from us, and d is its distance. The constant of proportionality Ho is now called the Hubble constant. The common unit of velocity used to measure the speed of a galaxy is km/sec, while the most common unit of for measuring the distance to nearby galaxies is called the Megaparsec (Mpc) which is equal to 3.26 million light years or 30,800,000,000,000,000,000 km! Thus the units of the Hubble constant are (km/sec)/Mpc." ( Source: NASA - WMAP Universe)
"Hubble's second revolutionary discovery was based on comparing his measurements of the Cepheid-based galaxy distance determinations with measurements of the relative velocities of these galaxies. He showed that more distant galaxies were moving away from us more rapidly:
v = Hod
where v is the speed at which a galaxy moves away from us, and d is its distance. The constant of proportionality Ho is now called the Hubble constant. The common unit of velocity used to measure the speed of a galaxy is km/sec, while the most common unit of for measuring the distance to nearby galaxies is called the Megaparsec (Mpc) which is equal to 3.26 million light years or 30,800,000,000,000,000,000 km! Thus the units of the Hubble constant are (km/sec)/Mpc." ( Source: NASA - WMAP Universe)
From the posts and the links it would appear that everything is expanding
which includes everything within our galaxy but if true what happens to all the separate solar systems. As I said in my question if everything is expanding including within our solar system we would be aware of it because we are very close to each other . Our sun is only 93 million miles away from us and all the planets are relatively close .
All the web sites refer to the expansion of galaxies as a whole not what happens within those galaxies. Also one galaxy Andromeda is actually moving towards us which indicates we are not all moving at the same speed. So as jake said there are several forces acting on the galaxies eg
their speed presumably since the big bang and another force resulting in expansion. Great information from everyone thanks a lot.
which includes everything within our galaxy but if true what happens to all the separate solar systems. As I said in my question if everything is expanding including within our solar system we would be aware of it because we are very close to each other . Our sun is only 93 million miles away from us and all the planets are relatively close .
All the web sites refer to the expansion of galaxies as a whole not what happens within those galaxies. Also one galaxy Andromeda is actually moving towards us which indicates we are not all moving at the same speed. So as jake said there are several forces acting on the galaxies eg
their speed presumably since the big bang and another force resulting in expansion. Great information from everyone thanks a lot.
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