File talk:IceBlockNearJoekullsarlon.jpg

From the scale given by the photographer in the associated photographs at [1], I am estimating that this block of ice is about 1.5m high x 2m long x 1m deep. In which case it should weigh 4.12 x 10^6 grams or about 4 tonnes. Does that seem about right? - Solipsist 16:23, 23 Jun 2005 (UTC)

I have noth thoght about this and I think the estimation of the volume is fine. On the other hand I wonder how you came from a volume of 3m^3 to a weight of 4 tonnes. For fluid water you would have about 3 tonnes but the density of ice is less than fluid wahter so I would guess about 2 tonnes sounds reasonable. Andreas Tille 05:04, 24 Jun 2005 (UTC)

Well I checked an excellent reference source, called Wikipedia :), which says:

Ice has a density of 0.917 g/cm³ at 0 °C, whereas water has a density of 0.9998 g/cm³

But I have a typo above, I actually used an average depth of 1.5m. So

150 * 150 * 200 * 0.917 = 4,126,500 g = 4.1 tonnes

Ah yes, the typo makes it clear.

Dropping the depth to 1m, reduces that to 2.75 tonnes.

That's why I insisted. For a rough estimation 2 tonnes comes closer to your estimation of the dimensions.

For context, I was wanting an estimate of the mass of this block to improve the caption at en:Ice. Although this is a very nice picture, it does have the problem that there isn't much clue for scale — at first glance it could easily be a drinks ice cube. -- Solipsist 05:47, 24 Jun 2005 (UTC)

Yes, you are perfectly right here. It has more artistic than documentation value. For better estimation I uploaded one source image of the animation to this place. I could measure the hight of the tripod which can be seen inbetween my (the left man) legs perfectly. I guess it will be 40cm - but I can give you the exact measure. The real problem in your estimation is even if you know the maximum height and length and if we assume the maximum depth will be about the maximum height the shape is very different from a cuboid. The fact that the light shines very bright is a clear sign for a thin body at these places. So using the cuboid formula will overestimate the real weight by two or three. If you ask me trying the formula of a spindle which fits into this cuboid would be reasonable so even if you take your dimensions without the typo my clear vote would be that the weight is below 2 tonnes. Andreas Tille 07:50, 24 Jun 2005 (UTC)

Perhaps it makes more sense for the reader to name the maximum length and height than at the caption? Andreas Tille 07:52, 24 Jun 2005 (UTC)

That's good. The purpose of mentioning the weight estimation here was to get input from someone who actually saw this ice cube. I had actually been estimating that the peak height and width was 2m x 3m, since it looked taller than yourself and your friend, who I'd guess to be ~1.7m tall. However, looking at that still, that's probably an over estimate if the tripod is ~40cm - perhaps you never managed to stand up straight whilst swimming away :)

Well, I had no time to stand up (1,80m) because I was in a hurry. ;-)

But using that measurement on the still photo, I make the block average 80px x 160px and the tripod about 24px high. Equating to 1.33m x 2.66m. Again guess a depth equal to the height (its not likely to be smaller as it would roll over, but you might know otherwise) that makes the mass

133 x 133 x 266 x 0.917 = 4.3 x 10^6 g = 4.3 tonnes (that's a suprise - I was all ready to drop the mass to 2 tonnes.)

Well, as I said I do not think that a cuboid formula is right here.

I'm not really sure how best to phrase the size estimate for the caption. I considered 'a block of ice as big as a car', but that seems a bit cumbersome. My impression is that many people feel several tonnes of something is quite a lot without really knowing how much. -- Solipsist 13:15, 24 Jun 2005 (UTC)

Hmmm, as I said the estimation of the weight is quite weak and thus the comparision with a car is really a quite reasonable one.

BTW, I will never forget the moment when I did this shot - do not really think that I will ever be able to repeat this - but the concrete imagination of the size of this block is quite vague. It was thus exciting that I'm unable to remember these details. Andreas Tille 14:36, 24 Jun 2005 (UTC)

Once bitten, twice shy. But think of all the photography opportunities that you could be passing up. You could consider it valuable experience, and take it to the next level with a new career as a war photographer...

Definitely not. ;-)

the estimation of the weight is quite weak hugh what?!? I was trained as an astronomer, so any estimation within a factor of 10 is considered good going. We are easily within a factor of two here.- Solipsist 20:10, 24 Jun 2005 (UTC)

OK. As a physicist I can perfectly live with estimations like this. My reasoning is just that we have reasonable measures for the dimensions of the block which we just hide by an inexact estimation of the weight. Mostly people are not able to estimate the weight if they stand in front of such a thing while they have no big problems with the size. So what do we win by mentioning the weight instead of the dimensions. Andreas Tille 13:11, 25 Jun 2005 (UTC)