Cosmic Scale Problem

[Mintaka]

I have read that to help vizualize the relative sizes of the solar system we can imagine a model in which everything is reduced by a factor of a billion.

Then the model earth would be about 1.3 cm in diameter (like a grape). The moon would be about 30 cm from earth, the sun 1.5 metres away (and would be the height of a man)

and about 150metres from earth. Jupiter would be 15 cm in diameter and 750m away. Saturn would be 1500m away. A human on this scale would be the size of an atom.

 

 

My question is this - because I have forgotten where I read this information - On this scale, would the nearest star be 4000 km or 40,000km away?

 

Thank you!

[JMJones0424]

My question is this - because I have forgotten where I read this information - On this scale, would the nearest star be 4000 km or 40,000km away?

 

A little more than 40,100 km.

 

The speed of light is (roughly) 300,000 km/s and the nearest star, Proxima Centauri, is 4.24 light years away. to get the distance light travels in a year, we multiply 300,000 km/s by 60 s/min, and by 60 min/hr, and by 24 hr/day, and by 365 day/year, then multiply by 4.24 light years and divide by 1 billion, giving about 40,100 km.

 

EDIT: Freeztar has a thread, Cell Size and Scale, in which he linked to a site that shows a progression from intergalactic scales all the way down to the quark.

[Mintaka]

A little more than 40,100 km.

 

The speed of light is (roughly) 300,000 km/s and the nearest star, Proxima Centauri, is 4.24 light years away. to get the distance light travels in a year, we multiply 300,000 km/s by 60 s/min, and by 60 min/hr, and by 24 hr/day, and by 365 day/year, then multiply by 4.24 light years and divide by 1 billion, giving about 40,100 km.

 

EDIT: Freeztar has a thread, Cell Size and Scale, in which he linked to a site that shows a progression from intergalactic scales all the way down to the quark.

 

Thanks again, JM.

Finally managed to open the Java page on a Comet Bird browser, none of the others would do it. Great visuals. Just an afterthought, do you think we'll ever be able to travel at speeds which allow us reach the stars? Is it possible, even in theory? Thanks.

[JMJones0424]

I think I am not alone in saying that if we, as a species, succeed in not wiping ourselves out in the next few hundred years or so, then we might be able to achieve interstellar spaceflight. Technically, we have already launched craft capable of reaching the stars, though we certainly haven't even come close to figuring out the details on a manned mission.

 

From wikipedia-

As of November 12, 2010, Voyager 1 was about 115.251 AU (17.242 billion km, or 10.712 billion miles) or 0.002 of a light-year from the Sun. Radio signals traveling at the speed of light between Voyager 1 and Earth take more than 16 hours to cross the distance between the two. (To compare, Proxima Centauri, the closest star to our Sun, is about 4.2 light-years distant = 265 thousand AU) Voyager 1's current relative velocity is 17.07 km/s, or 61,452 kilometres per hour (38,185 mph). This calculates as 3.6 AU per year, about 10% faster than Voyager 2. At this velocity, 73,600 years would pass before reaching the nearest star, Proxima Centauri, were the spacecraft traveling in the direction of that star.

 

73 thousand years is one heck of a long voyage. Of course the transit time can be shortened with greater velocity, but the faster you go, the more dangerous interstellar particles become. Not to mention the difficulty of supplying the energy to accelerate, and then to decelerate at the destination. We have a long way to go yet.

[Mintaka]

I think I am not alone in saying that if we, as a species, succeed in not wiping ourselves out in the next few hundred years or so, then we might be able to achieve interstellar spaceflight. Technically, we have already launched craft capable of reaching the stars, though we certainly haven't even come close to figuring out the details on a manned mission.

 

From wikipedia-

 

 

73 thousand years is one heck of a long voyage. Of course the transit time can be shortened with greater velocity, but the faster you go, the more dangerous interstellar particles become. Not to mention the difficulty of supplying the energy to accelerate, and then to decelerate at the destination. We have a long way to go yet.

 

Thank you JM. What is the 73,000 year voyage you speak of?

 

Can I ask your own opintion please, on whether you think the universe is finite or infinite? Recently I have begun to think that the scale of our 'known' or viewable universe is so huge, that it's almost an irrelevant question anway. But nonetheless an interesting one. Watching Freeztar's video , I feel that the biggest change in our way of thinking now is adapting to the idea of relativity. Wasn't life simple when everything could be fixed and we knew our place in it? When we view the fly we feel big, but we know that in relation to the aphid, the fly is much bigger than we are in relation to the cosmos. We are much smaller than atoms on this scale, aren't we? For the past 6 years I have been so busy that I have not had time to think about the 'big picture' and the more I think of it, the less I feel the need to 'prove' myself in the so-called 'real world' of work and life. There is a sense of pointlessness to it all, once you begin to lose the ego-centred view. I guess 'humbling' is the word. I suppose this awareness of our minuteness in space is just part of our evolutionary growth as a species, maybe the only one which can save us. Ideas of wars and national interests and boundaries seem so petty in comparison. I guess your question about whether we will survive long enough to see the next few hundred years depends on how we learn humility by looking out into space and seeing our own fragility, rather than wanting to stomp on what we have underneath our feet. "can't see the wood for the trees" is a phrase which comes to mind.

[JMJones0424]

From the wikipedia quote, if Voyager 1 were headed to Proxima Centauri, it would take better than 73,000 years to arrive.

 

My opinion on the boundary condition of the universe is irrelevant, though you may find Ned Wright's Cosmology Tutorial a good starting point for further information.

 

I agree that it can seem overwhelming to think of the vast scale of the universe, but rather than insignificance, I find awe inspiring beauty and wonder. If you have not yet done so, I highly recommend reading Carl Sagan's Cosmos, or you can view the accompanying mini-series on hulu, or possibly find a copy in your local library.

 

The surface of the Earth is the shore of the cosmic ocean.:phones:

[Mintaka]

From the wikipedia quote, if Voyager 1 were headed to Proxima Centauri, it would take better than 73,000 years to arrive.

 

My opinion on the boundary condition of the universe is irrelevant, though you may find Ned Wright's Cosmology Tutorial a good starting point for further information.

 

I agree that it can seem overwhelming to think of the vast scale of the universe, but rather than insignificance, I find awe inspiring beauty and wonder. If you have not yet done so, I highly recommend reading Carl Sagan's Cosmos, or you can view the accompanying mini-series on hulu, or possibly find a copy in your local library.

 

The surface of the Earth is the shore of the cosmic ocean.:phones:

 

Very interesting. Unfortunately the Sagan video's are not viewable outside the US but the turorials by Ned Wright are well-worth printing.

I'm no scientist but the word 'singularity' always leaves me feeling the way I did when I asked my Dad a question he couldn't answer and he said : " Because it IS, that's why! " (in other words , don't ask)

 

A poster in here recently suggested that the idea of a 'singularity' wasn't difficult to grasp, any more than the idea of a baby as a singularity.

 

But this doesn't seem a good analogy to me as we know how babies are born and where they come from. They have parents.

 

To say the Big Bang results from a singularity is almost like Jesuits who claim that God made the earth in 7 days, and if you ask " Well who made God?", they say "God was always there".

 

Am I showing my ignorance by repeating some vague principle that comes back to me from school about " energy can neither be created nor destroyed?". Have I got that one right?

 

in other words, how can something be created from 'nothing?'

 

Do scientists not have a feeling of "copping out" by simply saying "well, there was no space or time before this event, end of story"?

 

Is there not something of the annoyed Dad who doesn't know an answer but who's pride makes him say "Well, because it IS, that's why!".

 

Are there any visual models that can help us to understand the 'shape' of the universe, as opposed to the misleading balloon model that Wright speaks about?

[freeztar]

Very interesting. Unfortunately the Sagan video's are not viewable outside the US but the turorials by Ned Wright are well-worth printing.

I'm no scientist but the word 'singularity' always leaves me feeling the way I did when I asked my Dad a question he couldn't answer and he said : " Because it IS, that's why! " (in other words , don't ask)

 

A poster in here recently suggested that the idea of a 'singularity' wasn't difficult to grasp, any more than the idea of a baby as a singularity.

 

But this doesn't seem a good analogy to me as we know how babies are born and where they come from. They have parents.

 

To say the Big Bang results from a singularity is almost like Jesuits who claim that God made the earth in 7 days, and if you ask " Well who made God?", they say "God was always there".

 

Am I showing my ignorance by repeating some vague principle that comes back to me from school about " energy can neither be created nor destroyed?". Have I got that one right?

 

in other words, how can something be created from 'nothing?'

 

Do scientists not have a feeling of "copping out" by simply saying "well, there was no space or time before this event, end of story"?

 

Is there not something of the annoyed Dad who doesn't know an answer but who's pride makes him say "Well, because it IS, that's why!".

 

Are there any visual models that can help us to understand the 'shape' of the universe, as opposed to the misleading balloon model that Wright speaks about?

 

I wouldn't call it a "cop out". We just simply do not know what happened in the moments before (and immediately after) the big bang. Any responsible scientist would admit to this lack of knowledge. It's how science progresses after all.

 

Quite a bit of progress has been made in the last decade to get closer and closer to the energies seen during the big bang. The LHC is promising in this respect. Several theories have been proposed that include multiverses that spin off "Baby universes" endlessly. These theories are elegant in that they account for some of the current mysteries like the entropy problem, but a lot of it is speculation with no way to form and test a formal scientific hypothesis. It's possible that we'll never really know for sure. Such are the mysteries of life.

 

Here's a decent description of the big bang singularity (note that the centers of black holes are said to be singularities as well):

 

According to the standard theory, our universe sprang into existence as "singularity" around 13.7 billion years ago. What is a "singularity" and where does it come from? Well, to be honest, we don't know for sure. Singularities are zones which defy our current understanding of physics. They are thought to exist at the core of "black holes." Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is actually squished into infinite density (a mathematical concept which truly boggles the mind). These zones of infinite density are called "singularities." Our universe is thought to have begun as an infinitesimally small, infinitely hot, infinitely dense, something - a singularity. Where did it come from? We don't know. Why did it appear? We don't know.

http://www.big-bang-theory.com/

 

It's a good question about mass/energy not being created or destroyed. During the Planck Epoch (the first fractions of a second of the universe), physics looked very different. Such seemingly-impossible conditions existed such as infinite mass and infinite density. In other words, the laws of physics that govern our universe now did not apply then. Secondly, as the BB singularity is presumed infinitely massive, and energy and mass can interchange, then that can equal a massive amount of energy.

 

Of course, it's more complicated. Here's a good read if you are interested: http://abyss.uoregon...ures/lec18.html

[Mintaka]

Thanks Freeztar, interesting article but not easy to get my head around.

 

 

 

I wouldn't call it a "cop out". We just simply do not know what happened in the moments before (and immediately after) the big bang. Any responsible scientist would admit to this lack of knowledge. It's how science progresses after all.

 

Quite a bit of progress has been made in the last decade to get closer and closer to the energies seen during the big bang. The LHC is promising in this respect. Several theories have been proposed that include multiverses that spin off "Baby universes" endlessly. These theories are elegant in that they account for some of the current mysteries like the entropy problem, but a lot of it is speculation with no way to form and test a formal scientific hypothesis. It's possible that we'll never really know for sure. Such are the mysteries of life.

 

Here's a decent description of the big bang singularity (note that the centers of black holes are said to be singularities as well):

 

 

http://www.big-bang-theory.com/

 

It's a good question about mass/energy not being created or destroyed. During the Planck Epoch (the first fractions of a second of the universe), physics looked very different. Such seemingly-impossible conditions existed such as infinite mass and infinite density. In other words, the laws of physics that govern our universe now did not apply then. Secondly, as the BB singularity is presumed infinitely massive, and energy and mass can interchange, then that can equal a massive amount of energy.

 

Of course, it's more complicated. Here's a good read if you are interested: http://abyss.uoregon...ures/lec18.html

[/color][/size]