As a novice that has a genuine interest in Space and it's many elements I am intrigued to know what is considered close?
I know it depends on the nature of the subject as saying Mars is close and that a black hole is close are completely different items.
Taking black holes as the measure. What constitutes close to Earth/ our solar system.
Is 100 light years considered neighbours? is 10,000 light years considered close?
What is the scientific perception on close?
In geology and Earth history the existance of humans would only have started in the last minute of Earth's history based on a 24-hour clock.
regards
R47
Full Version: How close is close in light years?
Well it depends.
I am doing this from memory in college so bear with me, but it was a good way for me to get an idea of scale.
Get a yeard stick and a piece of paper.
Put the yardstick over the piece of paper along the bottom of the page.
Place a circle near the left edge of the paper; that is the sun.
.4 inches from the sun place another dot; that is mercury
.75 inches from the sun place another dot; that is venus
1.0 inches from the sun place another dot; that is earth
1.5 inches from the sun place another dot; that is mars
5.0 inches from the sun place another dot; that is jupiter
9.0 inches from the sun place another dot; that is saturn
19.00 inches from the sun place another dot; that is uranus
30.00 inches from the sun place another dot; that is neptune
48.00 inches from the sun place another dot; that is pluto
So, we are about 4 feet from the sun to pluto using this scale... Let's say we are going to add the nearest star to us, Proxima Centauri. We would have to roll out that sheet of paper another FOUR MILES in order to make the next dot representing that star.
That is the closest neighbor and that is 4 light years away.
Our galaxy is about 100,000 light years across. We couldnt afford enough paper to pull that one off, but you get the idea.
The next closest galaxy to ours is The Andromeda galaxy which is a whopping 2.5 MILLION light years away.
I have no idea if I answered your question.
I am doing this from memory in college so bear with me, but it was a good way for me to get an idea of scale.
Get a yeard stick and a piece of paper.
Put the yardstick over the piece of paper along the bottom of the page.
Place a circle near the left edge of the paper; that is the sun.
.4 inches from the sun place another dot; that is mercury
.75 inches from the sun place another dot; that is venus
1.0 inches from the sun place another dot; that is earth
1.5 inches from the sun place another dot; that is mars
5.0 inches from the sun place another dot; that is jupiter
9.0 inches from the sun place another dot; that is saturn
19.00 inches from the sun place another dot; that is uranus
30.00 inches from the sun place another dot; that is neptune
48.00 inches from the sun place another dot; that is pluto
So, we are about 4 feet from the sun to pluto using this scale... Let's say we are going to add the nearest star to us, Proxima Centauri. We would have to roll out that sheet of paper another FOUR MILES in order to make the next dot representing that star.
That is the closest neighbor and that is 4 light years away.
Our galaxy is about 100,000 light years across. We couldnt afford enough paper to pull that one off, but you get the idea.
The next closest galaxy to ours is The Andromeda galaxy which is a whopping 2.5 MILLION light years away.
I have no idea if I answered your question.
Spot on and very much appreciate your explanation.
Easy for me to understand.
As I say..... I take an active interest, but technically I am at a loss.
Thank you
Easy for me to understand.
As I say..... I take an active interest, but technically I am at a loss.
Thank you
Hi Roj47.
A web site you may find interesting is: An Atlas of The Universe. This has 5 maps showing the distance to objects starting at 12.5 light years and ending at 14 billion light years.
A light year is the distance travelled by light (which travels at 300,000kps or 186.000mps) in one year. A light year is about 9.46 trillion (that's a million million) km or 5.88 trillion miles.
There are two other units of distance you may come across in astronomy articles:
The first of these is the Astronomical Unit (AU).
The AU is generally used to measure distances within the solar system. It is the approximate mean distance between the earth and sun (its formal definition makes my head hurt, but here goes: the radius of an unperturbed circular orbit a massless body would revolve about the sun in 2*(pi)/k days (i.e., 365.2568983.... days), where k is defined as the Gaussian constant exactly equal to 0.01720209895.). This is slight less than the actual mean earth sun distance.
1AU = 149,597,870.691km (92,955,807 miles)
The second unit that is used is the parsec. This is sometimes used instead of light years.
Because the Earth orbits the sun we look at nearby stars from a slightly different angle at different points in our orbit. The nearby stars appear to shift slightly against the distant background (in the same way that if you hold you finger up and the alternately look at it with your left and then right eye, the finger appears to move). This is know as parallax. A parsec is the distance required for a star to appear to shift by 1 second of arc (one 3600th of a degree) when it's position is measured 6 months apart.
1 Parsec = 3.261 light years.
A web site you may find interesting is: An Atlas of The Universe. This has 5 maps showing the distance to objects starting at 12.5 light years and ending at 14 billion light years.
A light year is the distance travelled by light (which travels at 300,000kps or 186.000mps) in one year. A light year is about 9.46 trillion (that's a million million) km or 5.88 trillion miles.
There are two other units of distance you may come across in astronomy articles:
The first of these is the Astronomical Unit (AU).
The AU is generally used to measure distances within the solar system. It is the approximate mean distance between the earth and sun (its formal definition makes my head hurt, but here goes: the radius of an unperturbed circular orbit a massless body would revolve about the sun in 2*(pi)/k days (i.e., 365.2568983.... days), where k is defined as the Gaussian constant exactly equal to 0.01720209895.). This is slight less than the actual mean earth sun distance.
1AU = 149,597,870.691km (92,955,807 miles)
The second unit that is used is the parsec. This is sometimes used instead of light years.
Because the Earth orbits the sun we look at nearby stars from a slightly different angle at different points in our orbit. The nearby stars appear to shift slightly against the distant background (in the same way that if you hold you finger up and the alternately look at it with your left and then right eye, the finger appears to move). This is know as parallax. A parsec is the distance required for a star to appear to shift by 1 second of arc (one 3600th of a degree) when it's position is measured 6 months apart.
1 Parsec = 3.261 light years.
Great question Roj47 
. I have learnt something new! I thought about this the other day and looked it up but it was so complicated I just couldn't seem to hold the info in my brain. 
Fluffy and Waspie you have made it much simpler to understand. Thankyou.
. I have learnt something new! I thought about this the other day and looked it up but it was so complicated I just couldn't seem to hold the info in my brain. Fluffy and Waspie you have made it much simpler to understand. Thankyou.
QUOTE(Roj47 @ Jun 9 2006, 04:17 AM) [snapback]1224535[/snapback]
As a novice that has a genuine interest in Space and it's many elements I am intrigued to know what is considered close?
I know it depends on the nature of the subject as saying Mars is close and that a black hole is close are completely different items.
Taking black holes as the measure. What constitutes close to Earth/ our solar system.
Is 100 light years considered neighbours? is 10,000 light years considered close?
What is the scientific perception on close?
In geology and Earth history the existance of humans would only have started in the last minute of Earth's history based on a 24-hour clock.
regards
R47
Roj...
I think Waspie and Fluff have given you a pretty good scalar reference. This allows the mind to comprehend the absolute vastness of the universe...for the most part anyway! It really is a mind boggling concept of distance, and if any of us sit there and really contemplate the vastness of the known universe, I think we're all eventually dumbfounded by its scale (at least I know I am).
Lottie said, "I thought about this the other day and looked it up but it was so complicated I just couldn't seem to hold the info in my brain."
I say, "Me too, Lottie!"
The difficult part of this is defining "close".
That somewhat arbitrary term is dependent on the overall scale that one is talking about.
If we're talking about manned space travel, for instance, the Moon in 1969 was considered far. Today, Mars is certainly considered far, but the Moon is a bit closer, relatively speaking. Neither of these bodies have changed their actual distance from us. But our perceptions have changed based on our knowledge and experience base.
On a solar system scale, we could reasonably conclude that Venus and Mars are somewhat close, but that Uranus , Neptune, and Pluto are indeed far away.
Expand that scale to a Milky Way reference, and Neptune and Pluto become close neighbors. In fact, an object 10,000 ly away is rather close. The other end of the galaxy is really far away.
Then, we can go to the Local Group scale. At that scale, everything in our galaxy is right around the corner, and M31 (Andromeda) is far away.
Take this to the scale of the known universe, and our local group in its entirety is right outside our back door. At this scalle, a billion ly is relatively close!
So, a consideration of "close" is actually subjective, and is entirely dependent on the overall scale of the thing you're talking about.
I bet that makes it as clear as mud, huh?!
Try wrapping your mind around the size of the universe with these thoughts: The closest large galaxy to our Milky Way is the Andromeda galaxy( two million light years ). The farthest galaxies we can now see are 10 or 12 billion light years away. We simply can't see a galaxy that is farther away in light years than the estimated age of the universe (14 billion or so years). This means we are surrounded by a sort of "horizon" that we can't see beyond, this horizon is set by the distance that light can travel over the age of the universe!
How's that for mind blowing vastness?
How's that for mind blowing vastness?
If you really want to know how big space is, read the words of the late, great Douglas Adams that appear in my signature. I think it sums it up nicely. 
Another way of trying to visuallise the size of space is by thinking about the New Horizons Mission to Pluto.
Launched on 19th January 2006 this spacecraft left Earth at 36,000 mph. It passed the moon's orbit in just 6 hours. It will reach Jupiter in February 2007, where it will recieve a gravitational "kick" accelerating it on to Pluto at 47,000 mph. Even at this speed it will not reach Pluto until July 2015.
New Horizons will eventually leave the solar system. If it was pointing in the correct direction to reach the nearest star (Proxima Centauri) it would take somewhere in the region of 60,000 years to arrive.
Another way of trying to visuallise the size of space is by thinking about the New Horizons Mission to Pluto.
Launched on 19th January 2006 this spacecraft left Earth at 36,000 mph. It passed the moon's orbit in just 6 hours. It will reach Jupiter in February 2007, where it will recieve a gravitational "kick" accelerating it on to Pluto at 47,000 mph. Even at this speed it will not reach Pluto until July 2015.
New Horizons will eventually leave the solar system. If it was pointing in the correct direction to reach the nearest star (Proxima Centauri) it would take somewhere in the region of 60,000 years to arrive.
I say about 1,000 light years is like a stars town, about 200 is the nighborhood. But that's just an opinion. Fluffybunny brought out a great about how pluto is close to the sun in the emptynees of space.
thats so crazy how big space is i want 2 go 2 a different galaxiy
light travels at 180,000 miles pers hour which a light year would be 1,576,800,000 miles
QUOTE(chris57 @ Jun 12 2006, 07:28 PM) [snapback]1228535[/snapback]
light travels at 180,000 miles pers hour which a light year would be 1,576,800,000 miles
Light travels at 186,000 miles per second.
What Waspie said, chris...
And that would make a light year approximately 5.88e12 miles, or, written out:
5,880,000,000,000 miles (let's just say six trillion miles...close enough). A loooong way.
The figure you wrote for a light year is actually equivalent to about 2.4 light hours...just a tiny fraction of a light year...about 6/10% of one.
That's a little less than the mean distance of the planet Uranus from Earth. That distance in itself would take almost 2 years to travel...at 100,000 miles per hour!
A light year is really big; unfathomably big...and, it's just an invisible fraction of the distance to the edge of the known universe!
Absolutely mind-numbing...
And that would make a light year approximately 5.88e12 miles, or, written out:
5,880,000,000,000 miles (let's just say six trillion miles...close enough). A loooong way.
The figure you wrote for a light year is actually equivalent to about 2.4 light hours...just a tiny fraction of a light year...about 6/10% of one.
That's a little less than the mean distance of the planet Uranus from Earth. That distance in itself would take almost 2 years to travel...at 100,000 miles per hour!
A light year is really big; unfathomably big...and, it's just an invisible fraction of the distance to the edge of the known universe!
Absolutely mind-numbing...
mmmmmm? interesting thread. 
QUOTE(Waspie_Dwarf @ Jun 12 2006, 01:33 PM) [snapback]1228543[/snapback]
Light travels at 186,000 miles per second.
sorry i thought it was per hour i miss read the article on another site
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