Facts that blow your mind
- Thread starter SmallTown
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Laughing
Well-known member
We don't know how big the universe is, nor, to be fair, would it matter for that fact, assuming it's not infinite.
In a room of 30 people, there is about 95% chance 2 will have the same birthday (different years probably).
In my household of 5 people, there were 2 people who shared one birthday and two others that shared a different birthday, both days were the 25th of a month and one of those days was Christmas day. Furthermore, one of the twin children went on to have two kids of her own that share the same birthday, but different years. We like to economise on greetings cards.
Brian Marwood
Well-known member
Twins are more likely than not to share the same birthday.
Brian Marwood
Well-known member
The Monty Hall problem is beautiful:
Surprisingly, the odds aren’t 50-50. If you switch doors you’ll win 2/3 of the time!
- There are 3 doors, behind which are two goats and a car.
- You pick a door (call it door A). You’re hoping for the car of course.
- Monty Hall, the game show host, examines the other doors (B & C) and opens one with a goat. (If both doors have goats, he picks randomly.)
Surprisingly, the odds aren’t 50-50. If you switch doors you’ll win 2/3 of the time!
Laughing
Well-known member
I was aware of this and have even simulated it to prove. However I still don't underrstand why. Your common sense tells you it should still remain a 1 in 3 chance.
I do understand that you have a bit more information than you had at the begining, and thats what reduces the odds, but, the host could always open one of the two remaining doors. So do you really have more information. You knew when you selected, in your example door A that either B or C would contain a goat, so do you have more information. You now know that, lets say door C has a goat. Previously you knew that B or C had a goat 100%, but not which one.
Thats why I ran the simulation and it is the case that if you swap choices, you win 2/3rds of the time. If you don't you win 1/3rd of the time.
Brian Marwood
Well-known member
But the equator is a real physical thing in that if you empty a bath above the equator the water will swirl one way and the opposite if you are below the equator. There are now enough baths to be able to see this from space.
Laughing
Well-known member
It isn't the north and south hemisphere its the earths rotation. It's called, and I am doing this from memory, the corlioris effect, or force.
Sorry, its actually stated as the observable universe.
The size of the observable universe is estimated at 93 billion light years, which is 8.8×1026 metres.
The shortest length, the Planck length, is around 1.6×10−35 metres.
It's may mean nothing but a fact I find fascinating nonetheless.
*the observable universe is a hard limit due to the opaque nature of the early universe, even if the actual universe was bigger we will never see it.
Laughing
Well-known member
The reason it doesn't mean anything is because everything smaller than a galaxy is, roughly, in the middle of the two lengths you give. This is because they are at the extremes of big and small.
Want being snarky but giving the reason.
Brian Marwood
Well-known member
Rubbish, that’s about the size of a landing strip, not the universe.
Laughing
Well-known member
I think he means x10^1026 metres
Haha, I didn't think it would be so controversial. The mid point of the two extremes I quoted is 0.12mm. Not my calculations and no offense taken if you disagree with the concept. It was a Neil Turok lecture where I first heard it and found it fascinating, whether it ultimately means anything I'd entirely up to our own imaginations.
Brian Marwood
Well-known member
Ahhh now we’re talking Hubble instead of binoculars.
Laughing
Well-known member
Yeah I generally disagree with the principle. Think back to the post a million is roughly a billion away from a billion. It's the difference in scale.
No need for offence to be taken by either of us, interesting conversation.
festa5
Well-known member
You definitely have more information (edit maybe you don't actually, but what you do have is a very different option to the one you were originally presented with, but it doesn't feel like it
). The best way I've seen it explained was what instead of 3 doors, there were 100.
You pick one at random.
The game show host (who knows what's behind every door) then opens 98 other doors he knows have goats in.
The original problem is the same principle but just with smaller numbers involved.
At the start what's the odds it's behind the door you picked? 1 in 3. The odds of it being behind one of the other two doors are 2 in 3. That fact never changes.
festa5
Well-known member
There was a great thread on this years and years ago. People flatly refused to accept it was anything other than 50/50, resorted to calling people who disagreed idiots etc.
Tremendous fun.
Ipad1977
Well-known member
What about if you had a garage with 10 cars in it, but you're hosting a garden party and your lawnmower has just packed in?
That goat would come in handy then.
king_hellfire
Well-known member
I’ve got a few books explaining this problem. One of them, I can’t remember what it’s called (but can find out) even extends the example to 100 doors and allowing you to choose 98 of them.
It’s a no brainer that you would take the option of choosing the option to open 98 doors out of 100, with the option of swapping for a 99th door, If you were given opportunity.
But it’s the same principle as with three doors or 1 million doors. No matter how many you choose all the empty doors will be opened leaving you with the same option at the end: stick or switch between the two remaining closed doors. Leaving you with the below situation.
