Seeing Double
When our eyes focus on something 5 meters away, objects that are 1 meter away tend to appear as two separate objects.
Say that you're focusing on an object 5 meters in front of you and you're holding up your right pointer finger 1 meter away from your face, almost in line with the object you're focused on. You then extend your left hand 0.5 meters directly infront of you so that it does not yet interfere with your view of your finger. You then slowly move your left hand between your right pointer finger and your left eye. Which image of your right finger will disappear first?
Challenge : Do this without acting it out.
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1 solution
@Trevor Arashiro Fun little experiment; I can't believe I've never noticed this before. :)
So how are things? I'd imagine you'll be keeping track of The Masters this weekend. Any predictions?
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Oh, looks like I forgot to hit "post" on my comment last night. RIP
Well, for starters, how about I start with the unexpected... like Ernie SEVEN PUTTING THE FIRST HOLE. Man that was painful to watch.
I also was pulling for Bubba and English to score much better than they did. Fortunately, Bubba made the cut (by a margin much smaller than the hairs on his chest, lol). Speith did well as expected, but I mean who doesn't have ridiculously high expectations of this guy? He's got some enormous pressure going into moving day and I'm curious to see how he deals with it. My personal prediction: a dirty dog fight for first between Speith, McIlroy, and Day.
As for school, things have been ramping up cuz all my AP teachers are trying to Prep us for the AP exams. Some how I've found a little time for Brilliant. Here's each teacher's logic, "We all have to prep you for exams, so we have to make you study hard... but I deserve just as much of your attention as all your other AP teachers, so I'm going to make this class just as hard as your other teachers make theirs." Then it becomes a contest between teachers for who can give their student the most homework and the winner gets $1,000,000. So have have things been with you?
As for the right finger disappearing first, I'm glad you had fun with this experiment. I figured this out the other day when I saw a dirty spot on the glass of my mom's car (ikr, dirty spot. . . mom's car. . . something is wrong) and I blinked one eye to see which disappeared first, to which I got this surprising result.
However, I'm not sure if it's the lateralization of the brain function as it is sight lines. My theory comes from a slight reversal of the experiment I did after. If you reverse the experiment and focus on a close object and see double of a far object, the left object disappears first if you repeat the above steps.
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Hey Trevor. Sorry to hear that all your AP teachers are causing you so much grief. There seems to be so much more pressure on your generation than previous ones. Hopefully hitting golf balls really hard (while of course swinging within yourself) allows you to deal with the stress. :)
Poor Ernie; if not for that one hole he would have made the cut. :( And lucky Bubba! Spieth's bogey on the 17th put him on the 10-shot threshold, and bizarrely he was the only player at plus-6. You may be right about the dogfight between the world's top three. Day is my personal fave, but McIlroy has a bounce in his step and sparkle in his eye that makes me think he may take home his first green jacket this year. But scoring conditions will be tough this weekend, (the low score today was only 71), so I think that will bring more players into the mix. I'll be curious to see how the amateur Bryson Dechambeau fares; he looks like he may be a star in the making.
As for the question at hand, I think that your sight-line theory does make sense and gains more traction when considering your "reverse" experiment. I used a ruler held vertically rather than my free hand to do the visual obstruction this time around, moving it back and forth across the field of view. The reverse results of the close vs. far experiments do corroborate your theory, as illustrated by your diagrams. All brought on by a dirty windshield; physics is lurking everywhere. :)
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@Brian Charlesworth – Well yesterday was quite the day. Both for me and the masters. Took the ACT and that was somethin else.
I never expected Bernhard to come this close to the top. Unfortunately, he's 3 over today so he's fallen out of it. I called Day's comeback but I was hoping he'd go a little lower. Still, he's only 4 strokes back so he's in it. So with handled the pressure quite well yesterday and managed a 1 over. As for now, the top four are going at it and it's gonna come down to the last hole.
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@Trevor Arashiro – Was the ACT test tougher than you expected?
The Masters is Spieth's to lose, but it should still be an amazing back 9. So many good players just a few strokes behind: Willett, Westwood, Johnson, Day, Snedeker ... Could end up being a real horse race to the finish. My only prediction is that -6 will be the winning score. :)
Edit: Wow, I didn't see that coming. I have no doubt that Jordan will recover from that debacle, but it will sure sting for a while. Once again the 12th at Augusta on Sunday lives up to its reputation of being the scariest hole in golf. (The 17th at TPC Sawgrass is wickedly frightening too but The Players isn't a major of course.) What are your takeaways from this year's tournament?
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@Brian Charlesworth – Well, I learned that just cuz you don't know a guy, doesn't mean that he can't win the masters. I was very shocked by this year's outcome. In a good way at least. Spieth is getting a lot of talk for not winning after such an outstanding first day, and I have seen some pretty funny pictures about this ( such as this one ).
The ACT wasn't that bad, except for the reading section which I really feel they didn't give us enough time to do. The math section was easy as always :3
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@Trevor Arashiro – Always fear the guy who has nothing to lose. Willett is a new father and originally hadn't planned to be at the Masters because April 10th was his wife's due date. The baby came early so he could compete, and he made the most of it. Becoming a father must have put golf in perspective. You could see from his facial expression while he watched his tee shot on the 16th just how dialed in he was; no fear whatsoever. As for Spieth, trying to go wire-to-wire, back-to-back, the pressure was immense. And on top of that, he was never really comfortable with his swing all week. He backed off of every shot and was put on the clock Friday as a result. But what was really weird was that he had seemed to get it together with those 4 birdies at the end of the front 9, and then .... well, you know the rest. He thought he had the putt on 11, let that miss get to him and then rushed his tee shot on 12. That I can understand, but the chunked 3rd shot I can't. That was pure choke, and it will haunt him for some time. (He needs to do something about that chicken wing on his wedge shots; I know it's what he does normally but it looks horrible and doesn't seem to hold up under pressure.) He has handled himself with grace since the meltdown and has been remarkably candid about what was going through his mind at the time, so while he's clearly scarred psychologically he should eventually emerge from this stronger than ever. Maybe he can get his revenge on the golfing gods at Oakmont. I'd like to see Dustin Johnson do well there too; he's due for a breakthrough. Then for the British Open, Day for the win. :)
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@Brian Charlesworth – Wow, that's quite an insight on the masters. I never really give competitions other than the ones I participate in that much thought. Where does all your knowledge of golf come from? You know more about golf than me XD :P. Are you a golfer yourself?
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@Trevor Arashiro – I was an avid golfer in my late teens and early 20's. I never had a lesson; I learned from books, (Hogan, Nicklaus, Armour), magazines and from watching tournament golf live on the telly, (no recording devices or youtube in those days). I initially watched to learn the technical stuff, but soon realized that the game was as much a test of character as it was of technique. This also led to an interest in the history of the game, (although I'm no Ben Crenshaw at that). You spend a fraction of the time actually hitting a ball and most of the time trying your best to keep thoughts of what can go wrong from creeping in to your game,. Nowadays I experience golf vicariously through watching the majors, the main focus being the human drama involved. You get a sense of these guys by how they respond to pressure, success and failure, and I develop favorites based on these responses. Perhaps I'm a psychologist at heart as well. :)
@Trevor Arashiro – Amazing win for Dustin! :)) I was really pulling for him. Now I just need Day to win the British. As for the PGA: Spieth, perhaps? So is your school year done?
@Brian Charlesworth – Ummm... 1 question.... Will a helium balloon rise in a vacuum?
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@Pasan Aluthge – A helium balloon rises in air because helium gas is lighter than air, (which is mostly nitrogen and oxygen), at standard atmospheric pressure. But if the surrounding atmosphere, (or lack of an atmosphere in the case of a vacuum), is lighter than helium gas then the balloon would fall .... as long as some gravity is present. So on the Moon the ballon would fall, as there is no atmosphere. In the case of Mars, there is an atmosphere that is thinner than Earth's but still heavier than that found in upper levels of Earth's atmosphere where helium balloons have been known to still rise, so since Mars' gravity is less than Earth's we would expect a helium ballon to rise on Mars. In zero gravity situations, like in outer space or even in the Space Station, (which has an atmosphere), the balloon would just sit there until some external force acts on it.
The balloon would expand in inverse proportion to the ambient (surrounding) pressure, so if the balloon is made of a particularly fragile material it could burst in a vacuum. Hypothetically, though, if the balloon were made of a material with infinite tensile strength then in a perfect vacuum, (which not even outer space is, alas), the balloon could expand to the size of the universe, (and maybe beyond). :)
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@Brian Charlesworth – Wow.....Great Explanation....Thank you so much!
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@Pasan Aluthge – You're welcome! It was a fun question to think about. :)
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@Brian Charlesworth – I Have A Few More Questions....Hope you can help me out a bit..
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@Pasan Aluthge – Does it take longer to boil eggs on a mountain than at sea level? WHY? IF you placed a bulb on water and passed electricity through the water, would the bulb light? What would happen to a glass of water placed in space?
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@Pasan Aluthge – At higher elevations the atmosphere thins and hence the ambient air pressure decreases. Now boiling water requires energy to overcome the bonds between water molecules as well as to overcome the outside pressure on the water which helps keep the water molecules together. This outside pressure comes from both gravity and ambient air pressure. So since on a mountain the air pressure is diminished, it requires less energy to boil the water and hence the water boils at a lower temperature. At a lower temperature it then takes longer to cook the egg, as it is receiving less energy per second to complete the process. At sea level a medium-sized egg would take about 3 minutes to cook in boiling water, while at an elevation of 3000 m. it would take about 5 minutes. (Note that the Earth's gravitational effect is diminished at higher elevations as well, but the effect would be relatively small compared to the effect of the change in ambient air pressure.)
In space there would be no external air pressure, so the energy required for the water to boil would be greatly diminished. Since the water, to be in that state, would initially have a temperature between 0 and 100 degrees Celsius, there would be enough energy in the glass to allow for some molecules to break free, i.e., boil off. But after some of this inherent energy is lost the remaining molecules will lose energy and eventually revert from a liquid to a solid state, i.e., freeze. This video explains the phenomenon and provides a demonstration.
(Another cool video shows what happens to water on the Space Station, where this is an atmosphere but no gravity.)
As for the bulb in water, since fresh water is a poor conductor there would not be sufficient electricity generated to light the bulb. However, by dissolving some salt in the water the mixture would become a relatively good conductor, in which case there might be enough electricity to cause the bulb, held with the metal portion in the mixture, to glow, (albeit quite dimly). However, it would be better to form a circuit with the bulb out of the solution as demonstrated in this video .
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@Brian Charlesworth – WOW sir.... Your Explanations are the best! Love Them! I'll be sure to ask you more if I get any!!! THANK YOU AGAIN VERY MUCH!
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@Pasan Aluthge – You're welcome! Keep asking great questions. :)
@Pasan Aluthge – Here's a question for you. Using the information in Sir Brian's explanation above, would a helium balloon in a decelerating car move towards the front or the back of the car? The car is airtight.
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@Trevor Arashiro – WOW! Thanks for that great explanation! Really Appreciate it! Thank you! .. As for your question,I Feel Like It Would Move Backwards Since there is a force acting backwards on the car for it to decelerate..... But since the balloon rises(since He is less dense than air) to the top of the car (the roof part), it might not move at all if the friction is greater then the backward force (LOL) ... Love Answering these questions... THEY'RE AWESOME! (EVEN THOUGH I MIGHT BE INCORRECT) Waiting Impatiently For Your Explanation!
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@Pasan Aluthge – You're right in fact. It would move backward, but not because of the force of the deceleration of the car. By Newton's first law, objects in motion tend to stay in motion. The air in the car likes to stay in motion as well as the helium balloon. But the air is heavier than the helium balloon and thus has more inertia and it pushes towards the front of the car. Because of this forward movement of air, the helium balloon is pushed towards the back of the car.
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@Trevor Arashiro – Wouldn't the balloon be pushed forward along with the air particles?
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@Pasan Aluthge – It is pushed forward. Let me explain.
Say the entire car was filled with tiny balloons filled of air and helium. Each occupying the same amount of space. Helium is less dense than air, and thus the helium balloons will have less mass. F=ma and both types of balloons experience the same amount of deceleration. However, since the air balloons weigh more, they have more force forward and thus push towards the front with more force than the helium balloons.
It's the same concept as to why helium balloons rise in air. The helium and air balloons experience the same 9.8 m/s downwards acceleration, but since the air weighs more, it pushes down with more force thus forces the helium balloons up. This is why having no atmosphere will cause helium balloons to falls.
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@Trevor Arashiro – To demonstrate the so-called centrifugal force , we can consider what the balloon would do when driving in a circle at a constant speed. The air molecules and the balloon, because of inertia, will move to the side of the car on the outside of the curve, but as the air molecules are heavier the balloon will end up being forced to the side of the car on the inside of the curve.
@Trevor Arashiro – Oh I see..... never thought of using f=ma for the situation....cool..thanks!
@Pasan Aluthge – I could be wrong, but As for the light bulb, if you simply put the bulb in the water I don't think it will light. Current running through a bulb is what causes it to glow. In a salt water tank, the electric potential is basically the same for two points near eachother (which is what you'd get if you stuck a light bulb in. Current is caused by a difference in electric potential between two places. With a regular light bulb, the points of contact will be right next to eachother. Both points will have the same potential as eachother, thus the difference in potential between the two prongs is 0 and there will be no current.
However
1) if the liquid was a semi conductor, potential would fall off much quicker for a given length. Thus two points near eachother would have a greater difference in potential.
2) if the points where it contacts the water are far enough apart, then there will be a potential difference and thus the bulb will light.
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@Trevor Arashiro – You're quite right; even if the salt water tank were hooked up directly to the Hoover Dam the bulb probably wouldn't light up while just floating around, (although it might explode). :P Considering note 2), if we had a little LED light with two long contact wires with end-tabs made of dissimilar metals, (e.g., copper and aluminum, as in the video), placed far enough apart in the saline solution the bulb should(?) light up. In the video the solution hadn't been "pre-charged" as would normally be the case for a saltwater battery, so I would need to try that experiment myself before being convinced, (I'm an empiricist at heart).
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@Brian Charlesworth – Haha. I guess we're both empiricists. First thing I did when I got home was grab 3 pieces of foil, 2 batteries, and an LED. I created a working circuit, then used the third piece of foil to place across the prongs of the LED to simulate equal potentials at both ends to make sure that the bulb wouldn't light. This should imitate submerging a bulb in salt water.
Man, us nerds really are something else :P
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@Trevor Arashiro – Haha. Yes, indeed. :) So when you connected the two prongs with the third piece of foil did you simultaneously remove the batteries from the circuit, or did you effectively short the circuit?
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@Brian Charlesworth – I shorted the circuit, but I did it for at most a second. I couldn't remove them because that would stop the circuit.
The top is focusing on a distant object (similar to the problem) and the bottom focusing on a closer object.
The pink dot is the object you see two of, the black is the object you focus on. The blue sight line is the sight line from your left eye and the red from your right eye. When we obstruct the left sight line (right half), the object remains on the left/right side of our single, unobstructed sight line. This is why one time, the left side disappears first and the other time, the right one disappears first.
Just for the sake of starting a discussion, when I reverse the roles of my two hands it is the left image of my finger that disappears. (To make the experiment a bit easier I brought my "interfering" hand down with fingers spread out, so that I could more easily notice which of the two images remained and which disappeared.)
So the left image of the right pointer finger remained and the right image of the left pointer finger remained. I suspect this phenomenon comes as a result of the lateralization of brain function .