Score
Title
89
AskScience Panel of Scientists XVIII
272
AskScience AMA Series: "I am Rhett Allain, physicist and technical consultant on Mythbusters and MacGyver. Ask me about the physics of pretty much anything!
155
Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology
139
is it possible to move an object in circular motion using magnets?
37076
Why is it that during winter it's not uncommon to have days with abnormally high temperature and summer-like weather, but in the summer it never drops to winter-like weather for a day?
61
What triggers beta particles to form, and for what reason can they not penetrate substantially thick aluminium?
72
If capacitance increases as distance between plates decreases, why aren't there very small 1F capacitors?
27
What happens to the spin of an electron when it leaves a nucleus?
51
If the moon was created from an impact with Earth, could there be “Earth rocks” deep within the Moon?
60
Whats the truth about applying water to burns? Will cold water cause it to blister or stifle it? What about lukewarm water?
4
Have animals been observed using facial expressions to communicate among themselves?
213
If 2 people dislike the same food, are they then more likely to dislike other similar foods?
24
If both the liver and the kidney are filtering organs, what are their different responsibilities? Are there other organs that perform similar functions?
13
Why do martian rovers last so much longer than planned?
28
Are there positions of a chess board that are impossible to achieve legally?
18
Are there any materials that only allow radio waves to pass through in one direction?
1
Why are the characteristic lines from X-Rays limited by a lower AND UPPER energy?
1
How did chemists determine the structures of molecules before they had high power microscopes?
12
Why does water make paper products translucent?
60
Does the Mach Cone occurs only appears when crossing the 1 Mach speed or it can also appear later during the supersonic flight (> 1 Mach)?
5
How exact do orbital speeds need to be so you don't fly off into space (too fast) or fall into the atmosphere (too slow)?
32
What was going on in the science community when the first dinosaur bones were discovered? Did we realize early on what we were looking at? What was the attitude of the community towards the discovery?
5
How are the eggs of birds formed and what is the process called? Are they formed to the size that they are eventually hatched?
11
Is there a theoretical limit to how many protons an atom can contain?
6
What physically happens inside a computer when it crashes or freezes?
23
Could a planet with a highly eccentric orbit be tidally locked?
1
How do scientists assess/prove the age of ancient foot prints?
11
At what frequency does a repetitive sound become a solid sound?
545
Can dogs observe and recognize aging in adult humans? Do they differentiate between young adult, middle-aged and elderly humans?
14
Does the gravitational force of the sun and moon affect the atmosphere the same way it affects the tide? Is there an increase in oxygen during high tide/low tide?
0
I was never able to tune a guitar using my ear. Yesterday i did it out of the blue without practice. What happened to my brain?
10
Why are there so few species of mammals?
2
Can an oil reservoir "blow out" on its own with no human interaction?
28
Why don't the palms of our hands and the soles of our feet tan or burn?
2
Is energy gain relative?
14
Is it possible to trigger or "activate" a volcanic eruption?
2
How uneven can London Dispersion Forces make an atom?
7
Are there any known mutations in drosophila melanogaster that cause a phenotype of folded downward wings?
2
If Earth were larger, would it move closer to the sun or farther away?
9
Are blood bags usually sealed (in a vacuum)?
11011
When does a mushroom die? When it's picked? When it's packaged? Refrigerated? Sliced? Digested?
13
When you physically break or shatter a flash storage chip, to what degree is the data still readable from the fragments?
12 mfb- A great problem, and probably something you can write a master thesis on. Some assumptions: * Edge and corner pieces are recognizable as such * If two pieces fit together, we always know this. * We cannot use any sort of pattern on the pieces. Apart from the previous two bullet points we have no idea where a piece belongs to. Some initial thoughts: You can make estimates based on the relative number of center (M) and edge (E) pieces, but different length to height ratios will lead to different E to M ratios. All you get that way is a lower limit on the size (corresponding to square puzzles, asymmetric puzzles will have the same ratio at a larger overall size). Corner pieces (C) help: There are just 4 of them, if you draw the first one it doesn't tell you much, but with the second one you can be reasonably confident that the puzzle is not too much larger than what you have already. The third and fourth will refine these estimates even more. You know the length or height once you have a continuous connection between the corresponding edges (you don't need to have them in a straight line). This is a problem in [percolation theory](https://en.wikipedia.org/wiki/Percolation_theory). In the limit of infinite puzzle size, you need on average half the puzzle pieces for this if I remember correctly. There is another heuristic estimate, and one that will lead to a reliable (but not exact) estimate the fastest: Count the number of connections you found. I don't have an exact formula, but in a puzzle of N pieces (N>>1), the probability that two random pieces are next to each other is approximately 4/N. With sqrt(N) pieces drawn your expected number of connections is 2, while your expected number of corner pieces is 4. With 2sqrt(N) pieces drawn you expect 8 connections and 8 corner pieces. With 4sqrt(N) pieces drawn you expect 32 connections and 16 corner pieces. The number of connections grows much faster, with its inevitable sqrt(observed) scaling it gives a more reliable estimate than the corner pieces. In addition, its dependence on the overall puzzle shape is much smaller.
2 Sell200AprilAt142 Is the Jigsaw being put together as the pieces emerge? If so then the first time a row or column is completed then you know a dimension (ie it has edge pieces on each end). In this case you don't need the corners to know size If not then I suppose you could observe ratios of edge to non edge pieces and make some rough guess of size from that. (the number of non edge pieces increases in proportion to the square of half the number of edge pieces... That means the ratio should point to a specific size)
2 jaggededge13 The absolute minimum number of pieces is the length and width minus 1 (L+W-1) which has to include at least 4 edge/corner pieces. In addition, there has to be a direct path from edge to edge connecting all 4 sides. There are (2L-4)+(2W-4) or 2(L+W)-8 edge pieces (from here called E) and 4 corner pieces and N total pieces where N=L*W. On the other hand the maximum number needed is (L-1)*(W-1)+4 pieces. Or N-E. From this you can basically make a map of the probability the minimum requirement has been solved given a specified number of pieces drawn between the min and max. This will likely be something of a normal distribution. You are then in an N choose x scenario of possible draw combinations with y combinations that spell success. So Y/(N choose x) is the probability you have the answer. After (L+W-1) picks, the probability of success is LW/(N choose (L+W-1)) and so on. This will give you a plot that should exponentially level off and reach 1 at N-E. you can then do an expected value problem with this set of discreet points and get the expected number of selections before the size is known. This method doesn't really take into account the need for edge pieces, as its based on possible solutions as opposed to probability if picking adjacent pieces.
11 0 mfb- A great problem, and probably something you can write a master thesis on. Some assumptions: * Edge and corner pieces are recognizable as such * If two pieces fit together, we always know this. * We cannot use any sort of pattern on the pieces. Apart from the previous two bullet points we have no idea where a piece belongs to. Some initial thoughts: You can make estimates based on the relative number of center (M) and edge (E) pieces, but different length to height ratios will lead to different E to M ratios. All you get that way is a lower limit on the size (corresponding to square puzzles, asymmetric puzzles will have the same ratio at a larger overall size). Corner pieces (C) help: There are just 4 of them, if you draw the first one it doesn't tell you much, but with the second one you can be reasonably confident that the puzzle is not too much larger than what you have already. The third and fourth will refine these estimates even more. You know the length or height once you have a continuous connection between the corresponding edges (you don't need to have them in a straight line). This is a problem in [percolation theory](https://en.wikipedia.org/wiki/Percolation_theory). In the limit of infinite puzzle size, you need on average half the puzzle pieces for this if I remember correctly. There is another heuristic estimate, and one that will lead to a reliable (but not exact) estimate the fastest: Count the number of connections you found. I don't have an exact formula, but in a puzzle of N pieces (N>>1), the probability that two random pieces are next to each other is approximately 4/N. With sqrt(N) pieces drawn your expected number of connections is 2, while your expected number of corner pieces is 4. With 2sqrt(N) pieces drawn you expect 8 connections and 8 corner pieces. With 4sqrt(N) pieces drawn you expect 32 connections and 16 corner pieces. The number of connections grows much faster, with its inevitable sqrt(observed) scaling it gives a more reliable estimate than the corner pieces. In addition, its dependence on the overall puzzle shape is much smaller.
2 0 Sell200AprilAt142 Is the Jigsaw being put together as the pieces emerge? If so then the first time a row or column is completed then you know a dimension (ie it has edge pieces on each end). In this case you don't need the corners to know size If not then I suppose you could observe ratios of edge to non edge pieces and make some rough guess of size from that. (the number of non edge pieces increases in proportion to the square of half the number of edge pieces... That means the ratio should point to a specific size)
2 0 jaggededge13 The absolute minimum number of pieces is the length and width minus 1 (L+W-1) which has to include at least 4 edge/corner pieces. In addition, there has to be a direct path from edge to edge connecting all 4 sides. There are (2L-4)+(2W-4) or 2(L+W)-8 edge pieces (from here called E) and 4 corner pieces and N total pieces where N=L*W. On the other hand the maximum number needed is (L-1)*(W-1)+4 pieces. Or N-E. From this you can basically make a map of the probability the minimum requirement has been solved given a specified number of pieces drawn between the min and max. This will likely be something of a normal distribution. You are then in an N choose x scenario of possible draw combinations with y combinations that spell success. So Y/(N choose x) is the probability you have the answer. After (L+W-1) picks, the probability of success is LW/(N choose (L+W-1)) and so on. This will give you a plot that should exponentially level off and reach 1 at N-E. you can then do an expected value problem with this set of discreet points and get the expected number of selections before the size is known. This method doesn't really take into account the need for edge pieces, as its based on possible solutions as opposed to probability if picking adjacent pieces.