Orbis non sufficit
Wednesday, May 30, 2007
Ninja Party
Anyone got anything wrong with this date? It's very preliminary, but may move from that to solid within 24 hours :p.
Anyone got anything wrong with this date? It's very preliminary, but may move from that to solid within 24 hours :p.
Friday, May 25, 2007
How small we are
Since my sister asked me how many stars are in the solar system the other day, I have decided to enlighten you all as to your place in the known universe. You probably know where you are on planet, in the solar system and maybe even in the galaxy, but I shall take you further, while also showing you pretty pictures, many of which you can click on to see larger versions:
Firstly, I will assume you know where on Earth you are:
"The Blue Marble", Earth from approx. 45000 km
This is a real photograph, original caption:
"View of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Note the heavy cloud cover in the Southern Hemisphere. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is Madagascar. The Asian mainland is on the horizon toward the northeast."
Perhaps it's just me, but I always overcome by a feeling of how beautiful and mysterious the universe is when I see this picture. It is a very powerful image to me because, unlike any of the other photographs or images I will show you from here on, someone was there along with that camera. That view was directly witnessed by human eyes. We take all kinds of pretty pictures of the cosmos from here on Earth, but since that mission no human has ever been so far away from our home planet.
It is believed that this is the most widely distributed image in human history.
The inner solar system, with asteroids. There is really quite a lot of crap floating about out there.
The Milky Way (our galaxy), a 360 view from our vantage point. This is a collage of real photos.
This obviously is not the Milky Way, it is actually the spiral galaxy NGC 7331, approximately 43 million light years away, in the Pegasus constellation. It is believed that the milky way looks a lot like this though. The actual structure of the Milky Way as we believe it to be is shown below (less pretty though)
The numbering in the diagram is as follows:
2 and 8 - 3kpc and Perseus Arm
3 and 7 - Norma and Cygnus Arm (Along with a newly discovered extension - 6)
4 and 10 - Crux and Scutum Arm
5 and 9 - Carina and Sagittarius Arm
There are at least two smaller arms or spurs, including:
11 - Orion Arm (which contains the solar system and the Sun - 12)
So there you have it, you are at the 12 in the diagram. For interests sake, our nearest neighbour (spiral) galaxy is Andromeda, about 2.5 million light years away and pictured below
Next comes the local group of galaxies. At this point I'll stop pointing out where we are since the only way I can show that is with a more diagrams and we're here for pretty pictures.
"The galaxies of HCG 87, about four hundred million light-years distant. The large edge-on spiral, the fuzzy elliptical galaxy immediately to its right, and the spiral near the top of the image are members of the group, while the small spiral galaxy exactly in the middle is a more distant background galaxy."
The Milky Way is a member of its own group of galaxies just like this. Galaxies come in all sizes and shapes and colours; they're very pretty but I won't go into that.
Beyond that, groups of galaxies tend to clump together into galactic superclusters. Ours is called the Virgo supercluster. Pictures of these things are hard to get, so I'll just slap you with a nice picture of the "Hubble ultra-deep field"
It is very much worth your while to click on that and look at the big version. That photo was taken by the hubble space telescope and represents a piece of sky of size 11.5 square arcminutes. "This is smaller than a grain of sand held at arm's length, and equal to roughly one thirteen-millionth of the total area of the sky" (wikipedia).
As you can see, in this tiny portion of the sky there are a huge number of galaxies. Oh yes, most of those dots are galaxies, not stars. Some are even clusters of galaxies. To my knowledge, some of the small, red galaxies in that picture are among "the most distant objects to have been imaged by an optical telescope, existing when the universe was just 800 million years old", which is about 13 billion years ago. Ie, in the picture you are looking back 13 billion years in time at some points, to the very early universe.
Anyway, the picture isn't a bad representation of what a galactic supercluster might look like.
Finally, we reach the large-scale structure of the universe. For this, I have movies for you from the "Millenium Simulation" created by the Max Planck Institute. These things are hard to make, and are essentially a physics simulation containing huge numbers of particles, onto which Einstein's equations of general relativity are unleashed, which tells the particles how to gravitationally interact. These simulations are solutions to those equations, which to me is a testament to the predictive power of physics and mathematics. Let us begin with a journey through the large scale structure of the universe.
The dots you see are mass concentrations, essentially clusters of galaxies. Brighter, more yellow areas have a higher concentration of galaxies. You can see that galactic clusters form giant, crazy weblike structures. This is made more obvious in the next video:
Here we are beginning way out on the largest length scales that exist in the known universe and zoom in to somewhere around the size of the first video. GPc/h is a Giga-Parsec (the h is an error-related term), which is about 3.262 billion light-years, or roughly one fourteenth of the distance to the horizon of the observable universe.
Finally, we have the formation of the universe:
The simulation begins with matter spread evenly throughout space, as it is believed to have been a few million years after the big bang. As time progresses, gravity starts to pull matter into clumps, which then have more gravity and pull other things towards themselves, etc, eventually forming the weblike structure seen in the previous videos.
Phew. Feel insignificant yet? Keep in mind this is only as far as it is physically possible for us to observe. The edge of the observable universe is the furthest we can see before light has not had sufficient time to reach us since the beginning of the universe (ie, about 14 billion light years). We have no way of knowing what else is out there. Also, these simulations show the whole universe evolving at once, but this is not acutally what we see. Since light takes time to reach us, we see further into the past as we look further away, so looking into the depths of space we see less structure further away.
Anyway, thats enough eductation for now. Now you all know where you fit into the grand scheme of things.
Ok, one last thing. This next image is from a 3D model created by SDSS, or the Sloan Digital Sky Survey, which is a huge project currently running with the goal of mapping the local universe. The big fans are what have been mapped so far. You can see that they are really quite thin if you rotate the model. One fan is what has been observed from the northern hemisphere and the other is the southern. They've done an impressive job so far, but there is a lot to go. The Earth is at the centre where the fans converge, as you move further from the Earth you can see what I was saying about there being less structure (as we see it). Note that what we observe matches the models above pretty well.
Since my sister asked me how many stars are in the solar system the other day, I have decided to enlighten you all as to your place in the known universe. You probably know where you are on planet, in the solar system and maybe even in the galaxy, but I shall take you further, while also showing you pretty pictures, many of which you can click on to see larger versions:
Firstly, I will assume you know where on Earth you are:
"The Blue Marble", Earth from approx. 45000 km
This is a real photograph, original caption:
"View of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Note the heavy cloud cover in the Southern Hemisphere. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is Madagascar. The Asian mainland is on the horizon toward the northeast."
Perhaps it's just me, but I always overcome by a feeling of how beautiful and mysterious the universe is when I see this picture. It is a very powerful image to me because, unlike any of the other photographs or images I will show you from here on, someone was there along with that camera. That view was directly witnessed by human eyes. We take all kinds of pretty pictures of the cosmos from here on Earth, but since that mission no human has ever been so far away from our home planet.
It is believed that this is the most widely distributed image in human history.
The inner solar system, with asteroids. There is really quite a lot of crap floating about out there.
The Milky Way (our galaxy), a 360 view from our vantage point. This is a collage of real photos.
This obviously is not the Milky Way, it is actually the spiral galaxy NGC 7331, approximately 43 million light years away, in the Pegasus constellation. It is believed that the milky way looks a lot like this though. The actual structure of the Milky Way as we believe it to be is shown below (less pretty though)
The numbering in the diagram is as follows:
2 and 8 - 3kpc and Perseus Arm
3 and 7 - Norma and Cygnus Arm (Along with a newly discovered extension - 6)
4 and 10 - Crux and Scutum Arm
5 and 9 - Carina and Sagittarius Arm
There are at least two smaller arms or spurs, including:
11 - Orion Arm (which contains the solar system and the Sun - 12)
So there you have it, you are at the 12 in the diagram. For interests sake, our nearest neighbour (spiral) galaxy is Andromeda, about 2.5 million light years away and pictured below
Next comes the local group of galaxies. At this point I'll stop pointing out where we are since the only way I can show that is with a more diagrams and we're here for pretty pictures.
"The galaxies of HCG 87, about four hundred million light-years distant. The large edge-on spiral, the fuzzy elliptical galaxy immediately to its right, and the spiral near the top of the image are members of the group, while the small spiral galaxy exactly in the middle is a more distant background galaxy."
The Milky Way is a member of its own group of galaxies just like this. Galaxies come in all sizes and shapes and colours; they're very pretty but I won't go into that.
Beyond that, groups of galaxies tend to clump together into galactic superclusters. Ours is called the Virgo supercluster. Pictures of these things are hard to get, so I'll just slap you with a nice picture of the "Hubble ultra-deep field"
It is very much worth your while to click on that and look at the big version. That photo was taken by the hubble space telescope and represents a piece of sky of size 11.5 square arcminutes. "This is smaller than a grain of sand held at arm's length, and equal to roughly one thirteen-millionth of the total area of the sky" (wikipedia).
As you can see, in this tiny portion of the sky there are a huge number of galaxies. Oh yes, most of those dots are galaxies, not stars. Some are even clusters of galaxies. To my knowledge, some of the small, red galaxies in that picture are among "the most distant objects to have been imaged by an optical telescope, existing when the universe was just 800 million years old", which is about 13 billion years ago. Ie, in the picture you are looking back 13 billion years in time at some points, to the very early universe.
Anyway, the picture isn't a bad representation of what a galactic supercluster might look like.
Finally, we reach the large-scale structure of the universe. For this, I have movies for you from the "Millenium Simulation" created by the Max Planck Institute. These things are hard to make, and are essentially a physics simulation containing huge numbers of particles, onto which Einstein's equations of general relativity are unleashed, which tells the particles how to gravitationally interact. These simulations are solutions to those equations, which to me is a testament to the predictive power of physics and mathematics. Let us begin with a journey through the large scale structure of the universe.
The dots you see are mass concentrations, essentially clusters of galaxies. Brighter, more yellow areas have a higher concentration of galaxies. You can see that galactic clusters form giant, crazy weblike structures. This is made more obvious in the next video:
Here we are beginning way out on the largest length scales that exist in the known universe and zoom in to somewhere around the size of the first video. GPc/h is a Giga-Parsec (the h is an error-related term), which is about 3.262 billion light-years, or roughly one fourteenth of the distance to the horizon of the observable universe.
Finally, we have the formation of the universe:
The simulation begins with matter spread evenly throughout space, as it is believed to have been a few million years after the big bang. As time progresses, gravity starts to pull matter into clumps, which then have more gravity and pull other things towards themselves, etc, eventually forming the weblike structure seen in the previous videos.
Phew. Feel insignificant yet? Keep in mind this is only as far as it is physically possible for us to observe. The edge of the observable universe is the furthest we can see before light has not had sufficient time to reach us since the beginning of the universe (ie, about 14 billion light years). We have no way of knowing what else is out there. Also, these simulations show the whole universe evolving at once, but this is not acutally what we see. Since light takes time to reach us, we see further into the past as we look further away, so looking into the depths of space we see less structure further away.
Anyway, thats enough eductation for now. Now you all know where you fit into the grand scheme of things.
Ok, one last thing. This next image is from a 3D model created by SDSS, or the Sloan Digital Sky Survey, which is a huge project currently running with the goal of mapping the local universe. The big fans are what have been mapped so far. You can see that they are really quite thin if you rotate the model. One fan is what has been observed from the northern hemisphere and the other is the southern. They've done an impressive job so far, but there is a lot to go. The Earth is at the centre where the fans converge, as you move further from the Earth you can see what I was saying about there being less structure (as we see it). Note that what we observe matches the models above pretty well.
