How far can I (one) see?
Discussion
SpudLink said:
So, a star that suddenly appeared very bright in Andromeda might have gone supernova 2.5 million years ago, and you would be seeing 2.5 million light years (whatever that is in miles).
A supernova in a galaxy much much further away could mean you are seeing billions of light years, although what you are seeing happened before multi-celled life started on earth.
Is that right (in simple terms for my simple brain).
Yes - in simple terms.A supernova in a galaxy much much further away could mean you are seeing billions of light years, although what you are seeing happened before multi-celled life started on earth.
Is that right (in simple terms for my simple brain).
Light takes a finite time to travel from A to B. If the sun shut down suddenly, it would take 8 minutes for us to find out.
Andromeda is the NEAREST galaxy to us - and that is 2.5 million light years away. Most galaxies are a lot further and as far as I know, none can be seen without the aid of a telescope or binoculars.
Ayahuasca said:
Eric Mc said:
It's pretty certain that the Andromeda Galaxy is still there.
You cannot be certain that is still there. It may have been swallowed by a black hole thousands of years ago and you just wouldn't know. Don't forget it is the black hole at the centre of each galaxy that keeps them together.
And I did say "pretty certain" - not "absolutely certain".
TwigtheWonderkid said:
Apparently gamma ray bursts put out more light for a brief time than the rest of the combined light in the universe. 
Can they be seen with the naked eye (assuming you were fortunate enough to be looking in the right spot at the right moment)?
Humans can't see gamma rays. They're right at the end of the electromagnetic spectrum (the one that contains radio, heat, visible light, UV, microwave and gamma radiation). Can they be seen with the naked eye (assuming you were fortunate enough to be looking in the right spot at the right moment)?
TwigtheWonderkid said:
Agreed. So to make the OP's question a bit clear and to get to what I suspect he means, what's the most distant object that gives off light bright enough to see with the naked eye. (or gave off light as it may not exist anymore although we can still see it.)
On the other hand...The distance at which one cannot distinguish if another object is further away.
Something along the lines of the distance at which head movement cannot provide enough parallax to distinguish against objects which are even further away.
Eric Mc said:
Einion Yrth said:
The Magellanic clouds are a lot closer at 160,000 and 200,000 LY.
Yes, but they are gravitationally part of our galaxy i.e. they are island mini-galaxies as opposed to completely separate star systems.Edited by Einion Yrth on Monday 1st December 16:35
Toltec said:
TwigtheWonderkid said:
Agreed. So to make the OP's question a bit clear and to get to what I suspect he means, what's the most distant object that gives off light bright enough to see with the naked eye. (or gave off light as it may not exist anymore although we can still see it.)
On the other hand...The distance at which one cannot distinguish if another object is further away.
Something along the lines of the distance at which head movement cannot provide enough parallax to distinguish against objects which are even further away.
Einion Yrth said:
How separate are the milky way and andromeda? Given that, as you yourself note, they are moving towards an inevitable collision, presumably due to gravitational attraction.
I thought they were moving apart, as in 'expanding universe'?IIRC Andromeda is 400 light years away but this was just dragged up from some recess of the Simpo memory banks and may be wrong.
Einion Yrth said:
These days we use the entire diameter of the orbit of the Earth around the sun as our parallax base line, hence the Parallax second.
It is the radius, i.e one AU, I have heard of having a brain the size of a planet but if you can waggle your head that far...What I was suggesting was a baseline of around half a metre and a lateral way of looking for the answer.
Einion Yrth said:
How separate are the milky way and andromeda? Given that, as you yourself note, they are moving towards an inevitable collision, presumably due to gravitational attraction.
They are part of a galaxy supercluster, which means they are travelling around a common centre of gravity. But they aren't orbiting each other. The Magellanic Clouds are actually part of the Milky Way system. The Andromeda galaxy is not.But you are right, it is heading our way and eventually the two galaxies will collide - which should be fun.
Eric Mc said:
Einion Yrth said:
How separate are the milky way and andromeda? Given that, as you yourself note, they are moving towards an inevitable collision, presumably due to gravitational attraction.
They are part of a galaxy supercluster, which means they are travelling around a common centre of gravity. But they aren't orbiting each other. The Magellanic Clouds are actually part of the Milky Way system. The Andromeda galaxy is not.But you are right, it is heading our way and eventually the two galaxies will collide - which should be fun.
ash73 said:
And think about this; while it takes us 2.5M years to catch up on the latest goings on in Andromeda, as far as the light reaching our eyes is concerned it travelled zero distance, has no concept of time, and 'sees' the universe as a singularity. It didn't get the memo about the whole big bang expansion thing 
And since all photons are "the same", given the above, there need only be one.Eric Mc said:
Einion Yrth said:
How separate are the milky way and andromeda? Given that, as you yourself note, they are moving towards an inevitable collision, presumably due to gravitational attraction.
They are part of a galaxy supercluster, which means they are travelling around a common centre of gravity. But they aren't orbiting each other. The Magellanic Clouds are actually part of the Milky Way system. The Andromeda galaxy is not.But you are right, it is heading our way and eventually the two galaxies will collide - which should be fun.
annodomini2 said:
Roughly 1 billion years at which point many scientists believe there will be a high probability of our solar system being thrown out of the galaxy.
"And not before bloody time" - said the leader of the intelligent inhabitants of the planet Glise 581G."For way too long we've had to put up with our radio spectrum being polluted by the likes of Louis Walsh, "Celebrity Big Brother" and Russell Brand. The sooner the earth' Solar System moves beyond the radio range of ours the better".
With that he resumed feeding through his tentacled hands whilst incubating his brood of 800 children.
How far can you see ? Depends on what's blocking your view, not what photon's hit your eye.
If I looked out in the night sky at a blank piece of sky and there is nothing blocking my view then what distance am I looking at?
In effect I am looking at a distance up to the known limits of the universe (whatever they are this month) even if my eyes cannot resolve any features.
So there you go.
If I looked out in the night sky at a blank piece of sky and there is nothing blocking my view then what distance am I looking at?
In effect I am looking at a distance up to the known limits of the universe (whatever they are this month) even if my eyes cannot resolve any features.
So there you go.
Eric Mc said:
Ayahuasca said:
Eric Mc said:
It's pretty certain that the Andromeda Galaxy is still there.
You cannot be certain that is still there. It may have been swallowed by a black hole thousands of years ago and you just wouldn't know. Don't forget it is the black hole at the centre of each galaxy that keeps them together.
And I did say "pretty certain" - not "absolutely certain".
Edited by Ayahuasca on Wednesday 3rd December 02:19
Gassing Station | Science! | Top of Page | What's New | My Stuff