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Hopeless at maths



 
 
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  #1  
Old March 30th 17, 07:39 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,082
Default Hopeless at maths

I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.

Help!

Bill
  #2  
Old March 30th 17, 07:58 PM posted to uk.tech.digital-tv
Indy Jess John
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Posts: 1,239
Default Hopeless at maths

On 30/03/2017 19:39, Bill Wright wrote:
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.

Help!

Bill


If here to London becomes here to Andromeda, then the human hair becomes
2km thick.

Jim

  #3  
Old March 30th 17, 08:00 PM posted to uk.tech.digital-tv
Mark Carver
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Posts: 7,594
Default Hopeless at maths

On 30/03/2017 19:39, Bill Wright wrote:
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.


Speed of light, 299,792,458 m/s

Number of seconds in a year

60 x 60 x 24 x 365 = 31,536,000 seconds

Therefore in one year light travels 31.536 x 10^6 x 299.792458 x 10^6

= 9.4542547 x 10^15 metres

So in 2.5 years

2.3635637 x 10^16 metres

2.3635637 x 10^13 km

So 2.3635637 x 10^13 km / 250 x 10^3 = 9.4542548 x 10^7

Therefore if a human hair represents 250km, it's 94.5 million hairs to
Andromedia



--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #4  
Old March 30th 17, 08:09 PM posted to uk.tech.digital-tv
Roger Mills[_2_]
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Posts: 273
Default Hopeless at maths

On 30/03/2017 19:39, Bill Wright wrote:
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.

Help!

Bill


Do you have any familiar small objects that are only about 7,000 Km in
size? 'Cos, according to my back of an envelope calculations, that's the
size you'd need to represent a light year if 250Km is represented by 0.2mm
--
Cheers,
Roger
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  #5  
Old March 30th 17, 08:16 PM posted to uk.tech.digital-tv
Chris Green
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Posts: 148
Default Hopeless at maths

Bill Wright wrote:
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

I always find this sort of analogy simply annoying. It's a bit like
"it weighs the same as ten thousand bags of sugar".

Does it really convey anything except that a light year is a very long
way?

--
Chris Green
·
  #6  
Old March 30th 17, 08:42 PM posted to uk.tech.digital-tv
Mark Carver
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Posts: 7,594
Default Hopeless at maths

On 30/03/2017 20:16, Chris Green wrote:

Does it really convey anything except that a light year is a very long
way?


http://www.quotationspage.com/quote/33085.html




--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #7  
Old March 30th 17, 08:53 PM posted to uk.tech.digital-tv
Paul Ratcliffe
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Posts: 2,473
Default Hopeless at maths

On Thu, 30 Mar 2017 20:00:32 +0100, Mark Carver
wrote:

So in 2.5 years

2.3635637 x 10^16 metres

2.3635637 x 10^13 km

So 2.3635637 x 10^13 km / 250 x 10^3 = 9.4542548 x 10^7


Yeah, but he said 2.5 million light years, so multiply that by 10^6.

Therefore if a human hair represents 250km, it's 94.5 million hairs to
Andromedia


94.5 x 10^12 hairs.

Which is 94.5 x 10^12 x 0.2mm, which is 18.9 million km, which is a
bloody long way for a kid to comprehend.
Or about 472 times round the Earth's equator.
  #8  
Old March 30th 17, 09:44 PM posted to uk.tech.digital-tv
johnt
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Posts: 23
Default Hopeless at maths


"Bill Wright" wrote in message
news
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.

Help!

Bill


If 250km = a hair of 0.2 mm in width, my rough calculation suggests that a
light year would be represented by something with a width of about 53,000
km.
--
JohnT

  #9  
Old March 30th 17, 10:40 PM posted to uk.tech.digital-tv
Tim+[_4_]
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Posts: 191
Default Hopeless at maths

Bill Wright wrote:
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.

Help!

Bill


Why use hair widths as an analogy? Most of us have no idea how thick a hair
is. Surely the standard unit of length/distance is the double decker bus?
;-)

Tim

--
Please don't feed the trolls
  #10  
Old March 30th 17, 10:44 PM posted to uk.tech.digital-tv
Norman Wells[_6_]
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Posts: 949
Default Hopeless at maths

On 30/03/2017 20:00, Mark Carver wrote:
On 30/03/2017 19:39, Bill Wright wrote:
I'm hopeless at maths, but I'm trying to get something across to an
intelligent child. So, if the distance from here to London (250km) is
represented by the thickness of a hair (0.2mm) how far is a light year?
It doesn't have to be a hair; it could be anything familiar and small.

It's 2.5 million light years to the Andromeda Galaxy; that's what we're
discussing.


Speed of light, 299,792,458 m/s

Number of seconds in a year

60 x 60 x 24 x 365 = 31,536,000 seconds

Therefore in one year light travels 31.536 x 10^6 x 299.792458 x 10^6

= 9.4542547 x 10^15 metres

So in 2.5 years

2.3635637 x 10^16 metres

2.3635637 x 10^13 km

So 2.3635637 x 10^13 km / 250 x 10^3 = 9.4542548 x 10^7

Therefore if a human hair represents 250km, it's 94.5 million hairs to
Andromedia


It's much more than that.

A light year is 9.461*10^12 km

2.5 light years is 2.365*10^13 km.

Call it 2.5*10^13 km for ease of maths, which is 250*10^11 km.

Divide by 250 km (the distance to London) and you get:

2.5 light years is 10^11 times the distance to London. That's
100,000,000,000 or 100 billion times the distance to London.

Hairs are an irrelevant confusion. Forget them.



 




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