Planck Length .. and a 7yr old

[SystemParanoia]

Hi Guys,

My kids asked me this weekend what the smallest thing in the whole entire galaxy was, and how many can you fit in an atom. Offhand i told him that plank length was the smallest thing science could measure.

trouble is, after a few zero's I just lose all perspective of scale and cant imagine it at all.

So how can i explain the the difference size of an atom vs plank length ??

they have lots of books showing the size of earth vs Jupiter and the solar system etc..

P.S .. they wont let this go, so i've pretty much made a rod for my own back lol

Help?!

[rhinochopig]

There was a brilliant flash thing in this forum a few months ago, which started at human scale and you could zoom in or out to the biggest and smallest scales - great for adults and 7 year olds alike.

Sadly I can't find the thread but some kind soul will probably link to it if I've jogged their memory.

[mrmr96]

BOOM!

http://scaleofuniverse.com/

[skeeterm5]

If an atom was expanded to the size of the known universe, the Planck length would scarcely reach the height of an average tree.

I think a 7 year old could get that.

S

[rhinochopig]

mrmr96 said:

BOOM!

http://scaleofuniverse.com/

That's the badger! Well done that man. I shall book mark it for when my 4 year old gets older and asks the same question

[SystemParanoia]

Brilliant!

Thanks both of you..

plank length is really blooming small isnt. It! Lol


If something mesured 1 or 2 planck in size.. would it really exist?

[FarmyardPants]

Yes. My composter is proof of that.

[jimmy156]

mrmr96 said:

BOOM!

http://scaleofuniverse.com/

Interesting that!

Although it suggests that the electron is about the size of a chlorine nucleus which it isn't. An electron is about 1/1836th (or something like that) of the size of a proton, so significantly smaller. Although it does say something about it being the classic definition of an electron, so its either something to do with that (which i haven't heard of) or its wrong.

[TwigtheWonderkid]

Re the size of atoms, I was given 2 comparisons. If an atom in a Smartie was expanded to the size of a tube of Smarties, then a tube of Smarties would stretch to Pluto and back.

There are approx the same number of atoms in a teaspoon of water as there are teaspoons of water in the pacific ocean.

I haven't done the maths to verify these!!!

[Krikkit]

jimmy156 said:

mrmr96 said:

BOOM!

http://scaleofuniverse.com/

Interesting that!

Although it suggests that the electron is about the size of a chlorine nucleus which it isn't. An electron is about 1/1836th (or something like that) of the size of a proton, so significantly smaller. Although it does say something about it being the classic definition of an electron, so its either something to do with that (which i haven't heard of) or its wrong.

http://en.wikipedia.org/wiki/Classical_electron_radius

Basically, it's based on relativistic classical mechanics with no quantum fudgyness.

[jimmy156]

Krikkit said:

http://en.wikipedia.org/wiki/Classical_electron_ra...

Basically, it's based on relativistic classical mechanics with no quantum fudgyness.

Ah okay, reading that link it is incorrect with todays understanding, but is still used for some applications. Thanks!

[Slink]

TwigtheWonderkid said:

There are approx the same number of atoms in a teaspoon of water as there are teaspoons of water in the pacific ocean.

I haven't done the maths to verify these!!!

I might be incorrect here, but i think you are wrong.

tap water does not contain much apart from a bit of fluoride and other bits like other minerals.

whereas sea water has a hell of a lot of salt dissolved in it, so would be more dense i think (not a lot i grant you, but a bit)

so the salt water will have more atoms in than tap water as there is not just water, but water AND salt.

[Disco You]

SystemParanoia said:

i told him that plank length was the smallest thing science could measure.

Where did you pluck that from?

[SystemParanoia]

Disco You said:

SystemParanoia said:

i told him that plank length was the smallest thing science could measure.

Where did you pluck that from?

something i read online..

whats smaller than plank length?

[rhinochopig]

SystemParanoia said:

Disco You said:

SystemParanoia said:

i told him that plank length was the smallest thing science could measure.

Where did you pluck that from?

something i read online..

whats smaller than plank length?

The milliplank

[Halmyre]

SystemParanoia said:

Hi Guys,

My kids asked me this weekend what the smallest thing in the whole entire galaxy was, and how many can you fit in an atom. Offhand i told him that plank length was the smallest thing science could measure.

Not quite, it's the smallest definable length according to quantum physics, there's no way you could actually measure it.

[V8LM]

SystemParanoia said:

something i read online..

whats smaller than plank length?

A length of planck cut in half?

[Mr E]

mrmr96 said:

BOOM!

http://scaleofuniverse.com/

It is a wonderful and humbling thing.

[jimmy156]

Slink said:

TwigtheWonderkid said:

There are approx the same number of atoms in a teaspoon of water as there are teaspoons of water in the pacific ocean.

I haven't done the maths to verify these!!!

I might be incorrect here, but i think you are wrong.

tap water does not contain much apart from a bit of fluoride and other bits like other minerals.

whereas sea water has a hell of a lot of salt dissolved in it, so would be more dense i think (not a lot i grant you, but a bit)

so the salt water will have more atoms in than tap water as there is not just water, but water AND salt.

You are mis-reading what he said, have a look again!

anyway, a teaspoon of water (5 grams) would have 5/18's of a mole of water molecules. This is 1.67x10-23 molecules of water (167,000,000,000,000,000,000,000) Each molecule of water has three atoms so 5.01x10-23 atoms in a teaspoon of water.

From various sources, the pacific ocean contains 51% of the worlds oceanic water, and the mass of the worlds oceans to be about 1.4x10-21 kg. so 51% of that is 7.14x10-20 kg, which would be 7.14x10-23 grammes, 5 grammes per teaspoon = 1.43x10-23 teaspoons

So by that calculation (the numbers for the second half could be very wrong!) there are 3.5 times as many atoms (and about the same number of water molecules!) in a teaspoon of water as there are teaspoons of water in the pacific.

There are all sorts of things dissolved in sea water, including gold! I seem to remember that the germans, in trying to repay their debt after one of the world wars, tried to collect some of this gold, but it was costing them significantly more to find it then the gold was worth!

ETA: this took a few edits, its late

Edited by jimmy156 on Tuesday 2nd July 23:45

[TheExcession]

jimmy156 said:

ETA: this took a few edits, its late

It took a few reads, it's even later now - Top effort!"