If you shot a bullet in the air...

If you shot a bullet in the air...

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Discussion

toasty

Original Poster:

7,785 posts

227 months

Thursday 21st August 2014
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..and it ignored the Earth's gravity completely and went into space. What are the chances of it hitting anything ever?


AndrewEH1

4,922 posts

160 months

Thursday 21st August 2014
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P-Jay

10,812 posts

198 months

Thursday 21st August 2014
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I'd argue it's more like 100%

If you consider 'space' is basically a massive explosion expanding the speed of light in every direction chucking matter willy nilly as it goes it's growing far faster than the OP's bullet is going it's never going to run out of space and with nothing to stop it, or even slow it down and all this matter pissing about the place mad as lorries it seems to me a certainty that one day, it'll hit something or something will hit it - or rather at some point - because it might be billions or even trillions of years from now, long after our Sun has died and taken our planet with it rendering the concept of days based on the rotation of a, by then, long gone planet a bit moot.

TLandCruiser

2,811 posts

205 months

Thursday 21st August 2014
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P-Jay said:
I'd argue it's more like 100%

If you consider 'space' is basically a massive explosion expanding the speed of light in every direction chucking matter willy nilly as it goes it's growing far faster than the OP's bullet is going it's never going to run out of space and with nothing to stop it, or even slow it down and all this matter pissing about the place mad as lorries it seems to me a certainty that one day, it'll hit something or something will hit it - or rather at some point - because it might be billions or even trillions of years from now, long after our Sun has died and taken our planet with it rendering the concept of days based on the rotation of a, by then, long gone planet a bit moot.
so what was there before space?

Bisonhead

1,585 posts

196 months

Thursday 21st August 2014
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What a great website! Thanks

ikarl

3,739 posts

206 months

Thursday 21st August 2014
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Surely the chance of it hitting something is incredibly high?

The OP says that the earth doesn't have gravity, it doesn't mean that nothing else won't have a gravity pull on the bullet

Hackney

7,022 posts

215 months

Thursday 21st August 2014
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Assuming no gravity anywhere (Not just on earth) then the chances would be 100%.
In an infinite space and with infinite time, not matter how sparsely populated with objects that space is, as the bullet keeps travelling it will inevitably hit something. It may take a bloody long time but ultimately it will.

scorp

8,783 posts

236 months

Thursday 21st August 2014
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Hackney said:
Assuming no gravity anywhere (Not just on earth) then the chances would be 100%.
In an infinite space and with infinite time, not matter how sparsely populated with objects that space is, as the bullet keeps travelling it will inevitably hit something. It may take a bloody long time but ultimately it will.
Why infinite space ? As far as we know the matter in our universe is finite. The space/3 dimensional volume it sits in could well be infinite.

P-Jay

10,812 posts

198 months

Thursday 21st August 2014
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TLandCruiser said:
P-Jay said:
I'd argue it's more like 100%

If you consider 'space' is basically a massive explosion expanding the speed of light in every direction chucking matter willy nilly as it goes it's growing far faster than the OP's bullet is going it's never going to run out of space and with nothing to stop it, or even slow it down and all this matter pissing about the place mad as lorries it seems to me a certainty that one day, it'll hit something or something will hit it - or rather at some point - because it might be billions or even trillions of years from now, long after our Sun has died and taken our planet with it rendering the concept of days based on the rotation of a, by then, long gone planet a bit moot.
so what was there before space?
We don't know, and even if we did we probably wouldn't be able to understand it.

Back when I used to smoke a bit of weed and thought about things like this, this was always the point my brain sort of blue screened - some people will argue that God doesn't exist - because they know that the universe and whatever else was created by an explosion of super dense material which is still going on now - but like you say what came before this and what created the material and blew it up? I can't escape the thought that there had to be a point zero before anything existed and something caused it to happen - for want of a better term you need a 'God' to do that - is God a chap with a white beard sat on a cloud probably not, but it gives hope to a greater being that we understand which in turn gives hope to me that there's more to it than being blinked out of existence when we die - because to me that the most depression thing I can think of, the thought that when your brain dies that you're not really a person, or a 'soul' you're merely a chemical reaction driven by nothing more than the need to survive and reproduce - that you no longer exist.

Mr Tom

637 posts

148 months

Thursday 21st August 2014
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Hackney said:
Assuming no gravity anywhere (Not just on earth) then the chances would be 100%.
In an infinite space and with infinite time, not matter how sparsely populated with objects that space is, as the bullet keeps travelling it will inevitably hit something. It may take a bloody long time but ultimately it will.
The universe isn't infinite, otherwise the night sky would be infinitely bright, due to there being a star at every point in the sky.

Note: this is some sort of thought experiment, of which I can't remember who said it.

Edit: Ah it is Olbers paradox: http://en.m.wikipedia.org/wiki/Olbers'_paradox

Edited by Mr Tom on Thursday 21st August 10:42

Justin Cyder

12,624 posts

156 months

Thursday 21st August 2014
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Define anything. Space is much more populated with stuff than you might think. The chances of your theoretical bullet hitting something like dust for example are very high.

AndrewEH1

4,922 posts

160 months

Thursday 21st August 2014
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Bisonhead said:
What a great website! Thanks
His comics are pretty good too, he used to work for NASA but most of his comics are pretty accessable to people aren't rocket engineers!

http://xkcd.com/


Pro Tip: Hover over images to get more detail.

toasty

Original Poster:

7,785 posts

227 months

Thursday 21st August 2014
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Justin Cyder said:
Define anything. Space is much more populated with stuff than you might think. The chances of your theoretical bullet hitting something like dust for example are very high.
Good point. Let's say something big enough to stop the bullet continuing its journey.

elster

17,517 posts

217 months

Thursday 21st August 2014
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P-Jay said:
TLandCruiser said:
P-Jay said:
I'd argue it's more like 100%

If you consider 'space' is basically a massive explosion expanding the speed of light in every direction chucking matter willy nilly as it goes it's growing far faster than the OP's bullet is going it's never going to run out of space and with nothing to stop it, or even slow it down and all this matter pissing about the place mad as lorries it seems to me a certainty that one day, it'll hit something or something will hit it - or rather at some point - because it might be billions or even trillions of years from now, long after our Sun has died and taken our planet with it rendering the concept of days based on the rotation of a, by then, long gone planet a bit moot.
so what was there before space?
We don't know, and even if we did we probably wouldn't be able to understand it.

Back when I used to smoke a bit of weed and thought about things like this, this was always the point my brain sort of blue screened - some people will argue that God doesn't exist - because they know that the universe and whatever else was created by an explosion of super dense material which is still going on now - but like you say what came before this and what created the material and blew it up? I can't escape the thought that there had to be a point zero before anything existed and something caused it to happen - for want of a better term you need a 'God' to do that - is God a chap with a white beard sat on a cloud probably not, but it gives hope to a greater being that we understand which in turn gives hope to me that there's more to it than being blinked out of existence when we die - because to me that the most depression thing I can think of, the thought that when your brain dies that you're not really a person, or a 'soul' you're merely a chemical reaction driven by nothing more than the need to survive and reproduce - that you no longer exist.
Slight flaw in your look into the creation of the Universe.

If God created this universe, Who created God?

I think the second part of you point is the real reason of the thought of God, you want to have a purpose and think part of you will carry on.

Hackney

7,022 posts

215 months

Thursday 21st August 2014
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Mr Tom said:
Hackney said:
Assuming no gravity anywhere (Not just on earth) then the chances would be 100%.
In an infinite space and with infinite time, not matter how sparsely populated with objects that space is, as the bullet keeps travelling it will inevitably hit something. It may take a bloody long time but ultimately it will.
The universe isn't infinite, otherwise the night sky would be infinitely bright, due to there being a star at every point in the sky.

Note: this is some sort of thought experiment, of which I can't remember who said it.

Edit: Ah it is Olbers paradox: http://en.m.wikipedia.org/wiki/Olbers'_paradox

Edited by Mr Tom on Thursday 21st August 10:42
Would it though? There are stars out there that we can't see.

Simpo Two

87,119 posts

272 months

Thursday 21st August 2014
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Hackney said:
There are stars out there that we can't see.
- because the light hasn't had time to reach us I think.

Mr Tom

637 posts

148 months

Thursday 21st August 2014
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Simpo Two said:
- because the light hasn't had time to reach us I think.
Yes but if it was infinite, there would be a star (or light from a star) reaching us.

Also the Doppler effect (red/blue shift) suggests that most parts of the universe is moving away from us. (Suggesting a Big Bang)

Also I am no expert, just saying what I remember from my cosmology module of A-Level physics!

P-Jay

10,812 posts

198 months

Thursday 21st August 2014
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elster said:
Slight flaw in your look into the creation of the Universe.

If God created this universe, Who created God?

I think the second part of you point is the real reason of the thought of God, you want to have a purpose and think part of you will carry on.
Not really, to my mind 'God' is the creator, not in a humanoid over-lord who watches over us - you've only got to see the news every night to know that's not true - but as in a catch-all title for the origin of everything.

The truth is, whilst one day man might be able to prove and explain the origins of the universe and everything we'll never know or understand what created what came before that, what was the starting point of the massive chain reaction of events which created not only us, but the rest of the universe and whatever lays beyond that.

Of course it all ties into the whole science v religion argument that's be raging forever - but to me it'll never be settled the religious types are seemingly incapable of thinking outside their ancient texts despite the fact that it's proven that they're fallible and have been butchered and changed so much since their first version they probably bare little resemblance to them, and the scientist can only believe in what they can prove despite the certainty that we cannot prove what came before time.

Hopefully we find out when we die and there is something else, even if it's just another trip around the block in a different body, of a difference species on a different planet.

selym

9,557 posts

178 months

Thursday 21st August 2014
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Read 'A Short History of Nearly Everything' by Bill Bryson. You'll not be any more intelligent, just more enlightened.

Shaoxter

4,216 posts

131 months

Thursday 21st August 2014
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P-Jay said:
I can't escape the thought that there had to be a point zero before anything existed and something caused it to happen
You have to look at it as space-time rather than time being a separate and linear quantity. The Big Bang is when space and time were both created so there is no "before".