He said date not time. If so it would be 3.14.15. 9:26:53. An exponential time/date would better. Though also with date and time standards it is more appropriate to say the time followed by the date. Ideally you would have all of the units ascending or descending so: SS:mm:HH DD:MM:YYYY or YYYY:MM:DD HH:mm:SS. the second is the most appropriate it seems.
He said date not time. If so it would be 3.14.15. 9:26:53. An exponential time/date would better. Though also with date and time standards it is more appropriate to say the time followed by the date. Ideally you would have all of the units ascending or descending so: SS:mm:HH DD:MM:YYYY or YYYY:MM:DD HH:mm:SS. the second is the most appropriate it seems.
Dammit I want metric time.
Me too! But then if we went to metric time, we should/would have to get red of Degrees and replace them with gradians (in angles), as they are derived from the earths solar orbit time (it was origianlly thought the earth took 360 days to orbit the sun)
Me too! But then if we went to metric time, we should/would have to get red of Degrees and replace them with gradians (in angles), as they are derived from the earths solar orbit time (it was origianlly thought the earth took 360 days to orbit the sun)
Radians are quite appropriate though. Particularly with circles being tied to an irrational number.
Er, so... Could we get some science lessons for the dummies like me? I'd like to learn some stuff.
Lots of people here are good with computers, that counts as science right? Anything you can teach me about that? I won't pay you and will ask stupid questions.
Just wondering. It would be nice, you know, knowing stuff.
I'm willing to do something in return although I have no idea what.
I could probably write up some stuff about space or the history of Earth if you're interested in that. In fact, I want to.
I don't know if I'm good with computers, but I know the basics of programming really well. I've been taught them three or four times, and they were easy the first time.
I did my my NaNo (National Novel Writing Month entry) about dinosaurs, actually. It was a rewrite of a horrible cartoon and prominently involved magical, talking velociraptors, but I made sure that the velociraptors were small and had feathers.
Mine was about superheroes! Let's be best friends!
Okay! Maybe there should be a writing topic... Did you finish yours? I got 60,000 words in the end.
I'm writing up what I know about the history of the Earth, but I'm getting tired and I really should go to bed, so here's what I wrote about Earth before interesting life showed up. I'll do the part about life tomorrow.
I hope it makes sense and isn't too boring. I'm fairly certain that all of this true, or thought to be true under current theories.
The Earth is about four and a half billion years old. That's billions as in a thousand million, not a million million like it is in Europe. Not even the universe is a million million years old. So the Earth is about 4,540,000,000 years old.
Earth's history is divided into eons, which are divided into eras, which are divided into periods. There's some more divisions, but they're not important right now.
There are four eons, the Hadean, the Archean, the Proterozoic, and the Phanerozoic.
The earliest is the Hadean eon, which was named after Hades and sounds like a great place to spend an afternoon. It lasted from the formation of the Earth to about 3.8 billion years ago, and not much is known about it because not many rocks from that time survive. It is divided into eras, but they're named after places on the Moon, not the Earth. It was probably hot, and the atmosphere was definitely very different to today. There was far, far less oxygen; a human couldn't have survived. The oceans still managed to form, though, and the surface of the Earth probably wasn't molten, the way people used to think. At least, it probably wasn't molten for the whole eon.
The Earth got hit by a lot of huge rocks at the time, and the moon is thought to have formed when Earth was hit by a rock about the size of Mars, a few million years into Earth's history. Things settled down for a while, until the Late Heavy Bombardment, which happened about 4.1 to 3.8 billion years ago and hit the Earth and moon with a bunch of rocks big enough to resurface them many times over.
Since it's hard enough to find rocks from that time, no evidence of life in the Hadean has been found, but some people think that it existed, despite the being pummelled by giant rocks thing. I once saw a documentary on how life could've survived that - by burrowing deep within the Earth's surface, basically - and it included a disturbing description of what would happen if a rock of that size hit the Earth today.
The next eon was the Archean, which lasted from 3.8 billion years ago to 2.5 billion years ago. The name for the eon comes from an Ancient Greek word meaning "beginning". There still wasn't much oxygen in the air, but the oldest known life is from 3.5 billion years ago, so it definitely evolved during this eon or earlier. It was all microscopic, though. A lot of it hung around the surface in visible mats, but the organisms themselves were microscopic.
The third eon was the Proterozoic, meaning "earlier life". It lasted from 2.5 billion years ago to 0.542 billion years ago, or 542 million, making it almost as long as the Hadean and the Archean put together.
An event known as the oxygen catastrophe happened early in the Protereozoic, about 2.4 billion years ago, which increased the amount of oxygen in the atmosphere by quite a lot, enough to be breathable by a human, I think. It's called a catastrophe because oxygen would've been poisonous to most life at the time, so most of it would have died. Since bacteria evolves quickly, some of was able to adapt and start to depend on oxygen to live. The oxygen catastrophe was probably caused by bacteria that, like modern plants, got energy from the sun and gave off oxygen as a waste product.
Nothing happened for a few billion years, except for the evolution of sex, then Earth apparently froze, with glaciers at the equator. Life survived that too, because if it can survive the atmosphere being replaced by poison, it can survive a bit of freezing solid.
I think complex life evolved soon after the Earth thawed, but I'm not sure about that. Might have been earlier. Anyway, the earliest interesting life evolved near the very end on the Proterozoic, during the Ediacaran period about 635 million years ago to 542 million years ago. Nobody knows how these creatures fit into life as we understand it, and they're all gone now. They don't seem to have been plants, animals, or fungi.
The earliest is the Hadean eon [...] It is divided into eras, but they're named after places on the Moon, not the Earth.
My original question was "oh, did the moon already exist?" but you answered that afterwards. Why is it named after stuff on the moon, though? I mean, at first the moon wasn't there, yet the time when the moon didn't exist is named after part of the moon? That sounds weird.
The third eon was the Proterozoic, meaning "earlier life". It lasted from 2.5 billion years ago to 0.542 billion years ago, or 542 million, making it almost as long as the Hadean and the Archean put together.
So they're not divided into equal parts. They're divided based on events I assume. How so? Why aren't the first too put together for instance?
Nothing happened for a few billion years, except for the evolution of sex
Sex! Hurray!
... Oh, wait. I see what you mean.
That's interesting so far except I can see myself forgetting it pretty soon. I know, why don't you post pictures that were taken at the time? I'm a more visual person :P
I'm looking forward to the rest. I want to hear about the giant bugs.
My original question was "oh, did the moon already exist?" but you answered that afterwards. Why is it named after stuff on the moon, though? I mean, at first the moon wasn't there, yet the time when the moon didn't exist is named after part of the moon? That sounds weird.
So they're not divided into equal parts. They're divided based on events I assume. How so? Why aren't the first too put together for instance?
Sex! Hurray!
... Oh, wait. I see what you mean.
That's interesting so far except I can see myself forgetting it pretty soon. I know, why don't you post pictures that were taken at the time? I'm a more visual person :P
I'm looking forward to the rest. I want to hear about the giant bugs.
Maybe it was because at the time, the moon was aprt of the earth, so those areas would have been too. Just a theory though.
Also, very interesting post Shwoo!(what i read of it, i'm saving most of it until later when i have more time)
Avistew, I have pretty decent science knowledge, but maths is my strong point, by far. Would love to clear up any misconceptions or put anything you might wanna know about into layman's terms.
One thing I found awesome recently:
The earth doesn't spin 365 times in a year. It spins 366 times (367 times in a leap year!)
To explain, first imagine the earth doesn't spin at all. Then in a year, we have 1 massive day, and 1 massive night - we would spend half the year in the sun and half the year out of it. Now, in that image, let's spin the earth slightly, so that someone living where you are gets sun ALL THE TIME. As the earth goes around the sun, it turns so you're always facing the sun. When it's back where it started, you're back where it started, so in order to get no nights and one big day, the earth spins once.
Now make the earth spin twice. It's going faster than before, but you still end up where you started. You will get one day, and one night.
Now for every spin, we get another day and night, because you pass by the sun one more time. So if the earth spins three times, you get two days and two nights. If the earth spins four times, five days.
If we had a 100 day year, the earth would need to spin 101 times to make that happen.
We have a 365 day year, so the earth spins on its axis 366 times. What you learned in primary school was wrong :eek:
As a little added bit, in around the world in 80 days, the person experiences 80 nights and 80 days. Depending on which way round the earth he went, he would either have taken 79 days or 81, so there's a 50% chance he didn't meet the target
I'm not sure I understand the Earth spinning thing. The moon doesn't spin on itself, yet it's the same side facing us at all times, right? Why isn't Earth the same with the Sun?
The moon does spin, once a month. I'll draw a picture to show what would happen if the earth didn't spin.
There we go. That's the earth going around the sun. The red blob is me. When the earth is on the left, it's night, because the sun's rays cannot get to me. The earth's in the way. When the earth's on the right, it's day.
So if the earth didn't spin, half of the year would be daytime, and half of the year would be night.
The moon does spin, once a month. I'll draw a picture to show what would happen if the earth didn't spin.
There we go. That's the earth going around the sun. The red blob is me. When the earth is on the left, it's night, because the sun's rays cannot get to me. The earth's in the way. When the earth's on the right, it's day.
So if the earth didn't spin, half of the year would be daytime, and half of the year would be night.
The Word is orbit. and the earth rotates 365 times in a year (approx.). I don't think you have quite grasped this as a concept. Consider the centre of the earth as a origin and at the start of the year you are at the red point then you return to the original position (relative to the origin) in 24 hours.
Please read my post again. In order for us to perceive 365 days, the earth spins 366 times. The diagram above was demonstrating what would happen if it didn't spin - that we would experience one day and one night.
I chose not to use the word orbit because the 366 spins idea is a tricky enough concept as it is without using certain words that may bring up annoying little technicalities. For example, the fact that the moon doesn't orbit the earth. Both the moon and the earth orbit a central mass point which happens to be closer to the earth than the moon.
It can be hard for people to understand the 366 spins idea given that we are brought up learning 365 days = 365 spins, but please try to follow the explanation.
Another example which may help you understand (not saying it will, it actually just confused me, but helped my ex maths teacher to understand) involves two round coins.
Find any two round coins of the same size you have. OK now place one on top of the other. Keep the bottom one stationary, and roll the top one all the way around the bottom one. You should find that when the coin is at the bottom, it has done 1 complete rotation. Keep going... when the coin is at the top, it has done 2 complete rotations. Now do the same, following one point on the top coin only. You will find that when the coin gets back to the top, that point has only touched the stationary coin once.
If we take the stationary coin to mean the sun, and the moving coin to mean the earth, then that point you were following has experienced 1 day, and 1 day only, but as we concluded earlier, the coin/earth has rotated twice for this to happen.
1 day = 2 spins.
365 days = 366 spins.
Sorry long day, it's something I had never thought about (and frankly don't care about). You put it really badly though, worse than a Maths lecturer could. As a general rule, I wouldn't write something too long, particularly as a first comment. I would have put something along the lines of:
During the calendar year the earth rotates on it's axis 366 times, unlike the common misconception that it does 365 times, once for each day. However the perceived length of a day is actually longer than the period of rotation of the earth, which is closer to 23.94 hours than 24 hours. The reason we interpret the day as otherwise 00:00 would be midnight on the first day of the year and midday on the middle day of the year.
Which is far more concise and easier to read.
With other science stuff, I destroyed my metric spaces midterm earlier today!
Hmmm... I wanted to give an explanation of why it's 366 spins for 365 days rather than just state it outright. If you can think of a better explanation of the concept than the 0 spins, 1 spin, 2 spins way, then please post, so I can use it in the future It may just be that explaining things in person is easier than online.
Sorry if I've upset you, by the way. You seem a bit unhappy at my posts.
Keeping with astronomy and unexpected results though, the colour of the universe is beige, not black. You can see the specific colour it would be, and read more about why, on NASA's website here: http://apod.nasa.gov/apod/ap091101.html
Keeping with astronomy and unexpected results though, the colour of the universe is beige, not black. You can see the specific colour it would be, and read more about why, on NASA's website here: http://apod.nasa.gov/apod/ap091101.html
BBC have a new documentary on called "Wonders of the Solar System" it's not half-bad. UK folk should check it out here
(sorry everywhere else, link only works in the UK)
That program seems oddly close to our A-level physics program. Two weeks ago we were learning about the Hertzprung-russel star diagram, last week about newtonian Gravity, and this week about the gasses, which parrallels, parts of the program. For that reason, our Physics homework of late has been to watch the program.
Also, another Space-y programme worth watching Horizon:What if everything we know about the universe is wrong? . It does an excellent job of exposing theories about the universe as a patch job (This doesn't fit our model, lets invent some invisible, undetectable dark matter!).
My original question was "oh, did the moon already exist?" but you answered that afterwards. Why is it named after stuff on the moon, though? I mean, at first the moon wasn't there, yet the time when the moon didn't exist is named after part of the moon? That sounds weird.
Maybe it was because at the time, the moon was aprt of the earth, so those areas would have been too. Just a theory though.
No, it was an oversight. The moon formed early in the Hadean, and the era before its formation is known as the Cryptic era, because we don't know very much about it.
So they're not divided into equal parts. They're divided based on events I assume. How so? Why aren't the first too put together for instance?
Geological time is usually based on how the rocks at the time looked. For example, this picture I found on Wikipedia clearly shows the difference between rocks in the Cretacous period, the last period that the dinosaurs lived in, and the Paleogene period, the first period where they were all dead.
The end of the Hadean eon is the end of the Late Heavy Bombardment, probably because that's when the Earth was believed to have cooled down from being molten, even though we know now that that's not what happened.
The end of the Archean eon doesn't seem to be defined by anything thin particular, but the end of the Proterozoic was originally defined as when animals first appeared, and it wasn't changed when animals were found before that date.
That's interesting so far except I can see myself forgetting it pretty soon. I know, why don't you post pictures that were taken at the time? I'm a more visual person :P
I could probably find a picture of some galaxies that are far away enough for the light we see now to have left during the Hadean... Actually, I'll upload the timeline I made when I was trying to figure this stuff out. I found it helpful in showing when this stuff happened and how long humans have been here.
(click to enlarge)
I didn't actually label it, but... The bottom row is the whole history of the Earth and is one pixel for five million years, and the top row is just the current eon, and is one pixel for one million years. The green and blue line below the top row signify whether the Earth was in an ice age or not. The blue means ice age.
The moon does spin, once a month. I'll draw a picture to show what would happen if the earth didn't spin.
You know, I thought it was probably what you meant, but when I look at it, it seems to me that in your drawing the Earth does spin, because the red dot isn't facing the sun at all times. And it just feels like its "neutral" state would be to rotate around the Sun while facing it with the same side, so that any variation from that is comparatively spinning.
I understand what you mean, that in the absolute sense it's not. But... I don't know, it might just be me. The way I see it the universe has no up, down, left and right. So you can't really use it to check if you're moving on yourself or not. While "facing the Sun" would be a direction. And if something is always facing the Sun, then it's not spinning.
A bit like the concept of North and South, you know what I mean?
But I guess I see what you meant in your previous post, now. I can't say it boggles my mind :P The Earth spins 365 times + the time it does simply by being in orbit. That seems normal.
And I don't think you explained it badly. The way patters is explaining it, well, I haven't even read it completely, I find it much harder to follow. I just read the beginning over and over again without really following it at all. It's too "book-like". I need to feel like someone is actually talking to me.
Thanks for your answers, Schwoo. Your graph is scaring me.
I couldn't get the rest of the post finished due to unexpected depression... I hate it when that happens... but it should be done by the end of the week.
Which one? The image I made or the Flash I linked to?
The one you made. It's too abstract for me. It doesn't mean anything. Kinda like dates in history, they won't mean anything to me unless you tell me of Mrs X who lived at that time, and talk about what her day was like and what she reads in the paper and what she tells her friends about and so on. (Or you know, it can be a man, or a child, or even a dog if you want.)
I need something to tie it to. Graphs really don't do anything for me, and I was kidding when I talked about pictures.
Take as much time as you need.
Doodinthemood, I hope I didn't scare you off. I realise I wasn't really receptive, and I'm sorry about that.
Haha, that's fine avistew
Was just reading through shwoo's interesting postings. Not something I know much about, so am loving them.
Another bit of unexpectedness now:
If you have 50ml of water (measured in a measuring cylinder, perfectly) and 50ml of alcohol (ethanol, measured in a measuring cylinder, perfectly) and pour one into the other, you will have 96ml of liquid. But why?
The moon rotates around itself and the earth, at least if you're looking at the moon from the earth. Otherwise it's more the barycenter of the moon earth system. From earth you don't see any rotation of the moon around itself because it's a bound rotation which means, the moon is doing a full 360° rotation in the same time he needs to rotate around earth (in something about 27 days) as well.
This dynamic relationship between moon an earth is very important because it's stabilizing, keeping up the speed, of our earth rotation, which again is very important for good life conditions. Sadly our moon is slowly drifting away from us as well.
If you have 50ml of water (measured in a measuring cylinder, perfectly) and 50ml of alcohol (ethanol, measured in a measuring cylinder, perfectly) and pour one into the other, you will have 96ml of liquid. But why?
Does it have something to do with how when you have one bucket of sand and one bucket of water and you mix them you only have one bucket of wet sand, not two?
The best part of that costume was Raj immediately identifying Sheldon's costume as soon as he walks into the room. "I mean, look at Wolowitz. He's not English, but he's dressed like Peter Pan. Sheldon is neither sound nor light, but he's obviously the Doppler Effect." That is true. He is not. And Sheldon trying to get people to guess what he is. "A choo-choo train?" "...A retarded choo-choo train?"
The one you made. It's too abstract for me. It doesn't mean anything. Kinda like dates in history, they won't mean anything to me unless you tell me of Mrs X who lived at that time, and talk about what her day was like and what she reads in the paper and what she tells her friends about and so on. (Or you know, it can be a man, or a child, or even a dog if you want.)
I need something to tie it to. Graphs really don't do anything for me, and I was kidding when I talked about pictures.
The dates were too abstract for me until I made that graph and could see how much time had passed in between them. I know you were joking about the pictures, but I found that graph so helpful when I was figuring this stuff out that I thought I should post it. I was going to say that I didn't really have any pictures of the Precambrian, but I remembered that I never mentioned that phrase in my last post (it's an imformal term from the Hadean, Archean and Proterozoic eons), and I couldn't think of anything else.
Comments
Wait 6 years...
You mean 5.
3.14.15 Then, at 9 o' clock, Magic Happens.
Here in the Uk, the closes we ever get is Pi-approximation day, on the 22cnd of July (22/7)
I celebrate both :P
By eating only pies.
Oh, and there is also a Pie day.
All excuses are good to eat pie all day...
He said date not time. If so it would be 3.14.15. 9:26:53. An exponential time/date would better. Though also with date and time standards it is more appropriate to say the time followed by the date. Ideally you would have all of the units ascending or descending so: SS:mm:HH DD:MM:YYYY or YYYY:MM:DD HH:mm:SS. the second is the most appropriate it seems.
Dammit I want metric time.
Radians are quite appropriate though. Particularly with circles being tied to an irrational number.
Maybe, but i still hate them.
Lots of people here are good with computers, that counts as science right? Anything you can teach me about that? I won't pay you and will ask stupid questions.
Just wondering. It would be nice, you know, knowing stuff.
I'm willing to do something in return although I have no idea what.
I don't know if I'm good with computers, but I know the basics of programming really well. I've been taught them three or four times, and they were easy the first time.
Okay! Maybe there should be a writing topic... Did you finish yours? I got 60,000 words in the end.
Sure, that sounds interesting! Just pretend you're talking to a little kid and I should be able to follow :P
I hope it makes sense and isn't too boring. I'm fairly certain that all of this true, or thought to be true under current theories.
The Earth is about four and a half billion years old. That's billions as in a thousand million, not a million million like it is in Europe. Not even the universe is a million million years old. So the Earth is about 4,540,000,000 years old.
Earth's history is divided into eons, which are divided into eras, which are divided into periods. There's some more divisions, but they're not important right now.
There are four eons, the Hadean, the Archean, the Proterozoic, and the Phanerozoic.
The earliest is the Hadean eon, which was named after Hades and sounds like a great place to spend an afternoon. It lasted from the formation of the Earth to about 3.8 billion years ago, and not much is known about it because not many rocks from that time survive. It is divided into eras, but they're named after places on the Moon, not the Earth. It was probably hot, and the atmosphere was definitely very different to today. There was far, far less oxygen; a human couldn't have survived. The oceans still managed to form, though, and the surface of the Earth probably wasn't molten, the way people used to think. At least, it probably wasn't molten for the whole eon.
The Earth got hit by a lot of huge rocks at the time, and the moon is thought to have formed when Earth was hit by a rock about the size of Mars, a few million years into Earth's history. Things settled down for a while, until the Late Heavy Bombardment, which happened about 4.1 to 3.8 billion years ago and hit the Earth and moon with a bunch of rocks big enough to resurface them many times over.
Since it's hard enough to find rocks from that time, no evidence of life in the Hadean has been found, but some people think that it existed, despite the being pummelled by giant rocks thing. I once saw a documentary on how life could've survived that - by burrowing deep within the Earth's surface, basically - and it included a disturbing description of what would happen if a rock of that size hit the Earth today.
The next eon was the Archean, which lasted from 3.8 billion years ago to 2.5 billion years ago. The name for the eon comes from an Ancient Greek word meaning "beginning". There still wasn't much oxygen in the air, but the oldest known life is from 3.5 billion years ago, so it definitely evolved during this eon or earlier. It was all microscopic, though. A lot of it hung around the surface in visible mats, but the organisms themselves were microscopic.
The third eon was the Proterozoic, meaning "earlier life". It lasted from 2.5 billion years ago to 0.542 billion years ago, or 542 million, making it almost as long as the Hadean and the Archean put together.
An event known as the oxygen catastrophe happened early in the Protereozoic, about 2.4 billion years ago, which increased the amount of oxygen in the atmosphere by quite a lot, enough to be breathable by a human, I think. It's called a catastrophe because oxygen would've been poisonous to most life at the time, so most of it would have died. Since bacteria evolves quickly, some of was able to adapt and start to depend on oxygen to live. The oxygen catastrophe was probably caused by bacteria that, like modern plants, got energy from the sun and gave off oxygen as a waste product.
Nothing happened for a few billion years, except for the evolution of sex, then Earth apparently froze, with glaciers at the equator. Life survived that too, because if it can survive the atmosphere being replaced by poison, it can survive a bit of freezing solid.
I think complex life evolved soon after the Earth thawed, but I'm not sure about that. Might have been earlier. Anyway, the earliest interesting life evolved near the very end on the Proterozoic, during the Ediacaran period about 635 million years ago to 542 million years ago. Nobody knows how these creatures fit into life as we understand it, and they're all gone now. They don't seem to have been plants, animals, or fungi.
I'll post about the Phanerozoic tomorrow.
(Continued here, on a day that was not tomorrow)
My original question was "oh, did the moon already exist?" but you answered that afterwards. Why is it named after stuff on the moon, though? I mean, at first the moon wasn't there, yet the time when the moon didn't exist is named after part of the moon? That sounds weird.
So they're not divided into equal parts. They're divided based on events I assume. How so? Why aren't the first too put together for instance?
Sex! Hurray!
... Oh, wait. I see what you mean.
That's interesting so far except I can see myself forgetting it pretty soon. I know, why don't you post pictures that were taken at the time? I'm a more visual person :P
I'm looking forward to the rest. I want to hear about the giant bugs.
Maybe it was because at the time, the moon was aprt of the earth, so those areas would have been too. Just a theory though.
Also, very interesting post Shwoo!(what i read of it, i'm saving most of it until later when i have more time)
I prefer this version It's about 40 years old, but it goes into atomic substructure aswell. Or at least what was known about atoms back then.
Oh, I remember this one being played to us in primary school. I really liked it.
I'd never seen it before, until 2pstart did a gaming comic on it.
One thing I found awesome recently:
The earth doesn't spin 365 times in a year. It spins 366 times (367 times in a leap year!)
To explain, first imagine the earth doesn't spin at all. Then in a year, we have 1 massive day, and 1 massive night - we would spend half the year in the sun and half the year out of it. Now, in that image, let's spin the earth slightly, so that someone living where you are gets sun ALL THE TIME. As the earth goes around the sun, it turns so you're always facing the sun. When it's back where it started, you're back where it started, so in order to get no nights and one big day, the earth spins once.
Now make the earth spin twice. It's going faster than before, but you still end up where you started. You will get one day, and one night.
Now for every spin, we get another day and night, because you pass by the sun one more time. So if the earth spins three times, you get two days and two nights. If the earth spins four times, five days.
If we had a 100 day year, the earth would need to spin 101 times to make that happen.
We have a 365 day year, so the earth spins on its axis 366 times. What you learned in primary school was wrong :eek:
As a little added bit, in around the world in 80 days, the person experiences 80 nights and 80 days. Depending on which way round the earth he went, he would either have taken 79 days or 81, so there's a 50% chance he didn't meet the target
There we go. That's the earth going around the sun. The red blob is me. When the earth is on the left, it's night, because the sun's rays cannot get to me. The earth's in the way. When the earth's on the right, it's day.
So if the earth didn't spin, half of the year would be daytime, and half of the year would be night.
The Word is orbit. and the earth rotates 365 times in a year (approx.). I don't think you have quite grasped this as a concept. Consider the centre of the earth as a origin and at the start of the year you are at the red point then you return to the original position (relative to the origin) in 24 hours.
QED.
I chose not to use the word orbit because the 366 spins idea is a tricky enough concept as it is without using certain words that may bring up annoying little technicalities. For example, the fact that the moon doesn't orbit the earth. Both the moon and the earth orbit a central mass point which happens to be closer to the earth than the moon.
It can be hard for people to understand the 366 spins idea given that we are brought up learning 365 days = 365 spins, but please try to follow the explanation.
Another example which may help you understand (not saying it will, it actually just confused me, but helped my ex maths teacher to understand) involves two round coins.
Find any two round coins of the same size you have. OK now place one on top of the other. Keep the bottom one stationary, and roll the top one all the way around the bottom one. You should find that when the coin is at the bottom, it has done 1 complete rotation. Keep going... when the coin is at the top, it has done 2 complete rotations. Now do the same, following one point on the top coin only. You will find that when the coin gets back to the top, that point has only touched the stationary coin once.
If we take the stationary coin to mean the sun, and the moving coin to mean the earth, then that point you were following has experienced 1 day, and 1 day only, but as we concluded earlier, the coin/earth has rotated twice for this to happen.
1 day = 2 spins.
365 days = 366 spins.
(sorry everywhere else, link only works in the UK)
Sorry long day, it's something I had never thought about (and frankly don't care about). You put it really badly though, worse than a Maths lecturer could. As a general rule, I wouldn't write something too long, particularly as a first comment. I would have put something along the lines of:
During the calendar year the earth rotates on it's axis 366 times, unlike the common misconception that it does 365 times, once for each day. However the perceived length of a day is actually longer than the period of rotation of the earth, which is closer to 23.94 hours than 24 hours. The reason we interpret the day as otherwise 00:00 would be midnight on the first day of the year and midday on the middle day of the year.
Which is far more concise and easier to read.
With other science stuff, I destroyed my metric spaces midterm earlier today!
Sorry if I've upset you, by the way. You seem a bit unhappy at my posts.
Keeping with astronomy and unexpected results though, the colour of the universe is beige, not black. You can see the specific colour it would be, and read more about why, on NASA's website here:
http://apod.nasa.gov/apod/ap091101.html
Ok... that's new...
Also, another Space-y programme worth watching Horizon:What if everything we know about the universe is wrong? . It does an excellent job of exposing theories about the universe as a patch job (This doesn't fit our model, lets invent some invisible, undetectable dark matter!).
Geological time is usually based on how the rocks at the time looked. For example, this picture I found on Wikipedia clearly shows the difference between rocks in the Cretacous period, the last period that the dinosaurs lived in, and the Paleogene period, the first period where they were all dead.
The end of the Hadean eon is the end of the Late Heavy Bombardment, probably because that's when the Earth was believed to have cooled down from being molten, even though we know now that that's not what happened.
The end of the Archean eon doesn't seem to be defined by anything thin particular, but the end of the Proterozoic was originally defined as when animals first appeared, and it wasn't changed when animals were found before that date.
I could probably find a picture of some galaxies that are far away enough for the light we see now to have left during the Hadean... Actually, I'll upload the timeline I made when I was trying to figure this stuff out. I found it helpful in showing when this stuff happened and how long humans have been here.
(click to enlarge)
I didn't actually label it, but... The bottom row is the whole history of the Earth and is one pixel for five million years, and the top row is just the current eon, and is one pixel for one million years. The green and blue line below the top row signify whether the Earth was in an ice age or not. The blue means ice age.
The scale of the universe. It's interactive. I hear the subatomic particles are kind of wrong, though.
You know, I thought it was probably what you meant, but when I look at it, it seems to me that in your drawing the Earth does spin, because the red dot isn't facing the sun at all times. And it just feels like its "neutral" state would be to rotate around the Sun while facing it with the same side, so that any variation from that is comparatively spinning.
I understand what you mean, that in the absolute sense it's not. But... I don't know, it might just be me. The way I see it the universe has no up, down, left and right. So you can't really use it to check if you're moving on yourself or not. While "facing the Sun" would be a direction. And if something is always facing the Sun, then it's not spinning.
A bit like the concept of North and South, you know what I mean?
But I guess I see what you meant in your previous post, now. I can't say it boggles my mind :P The Earth spins 365 times + the time it does simply by being in orbit. That seems normal.
And I don't think you explained it badly. The way patters is explaining it, well, I haven't even read it completely, I find it much harder to follow. I just read the beginning over and over again without really following it at all. It's too "book-like". I need to feel like someone is actually talking to me.
Thanks for your answers, Schwoo. Your graph is scaring me.
There's actually no such thing as absolute position or orientation.
Which one? The image I made or the Flash I linked to?
The one you made. It's too abstract for me. It doesn't mean anything. Kinda like dates in history, they won't mean anything to me unless you tell me of Mrs X who lived at that time, and talk about what her day was like and what she reads in the paper and what she tells her friends about and so on. (Or you know, it can be a man, or a child, or even a dog if you want.)
I need something to tie it to. Graphs really don't do anything for me, and I was kidding when I talked about pictures.
Take as much time as you need.
Doodinthemood, I hope I didn't scare you off. I realise I wasn't really receptive, and I'm sorry about that.
You make me remember Doopler Effect. At the end, I always put the viewer without Velocity and re-arrange the source's accordingly.
Also, you make remember Albert Einstein and his dammed ball. "It's help me think". ARGH!
Was just reading through shwoo's interesting postings. Not something I know much about, so am loving them.
Another bit of unexpectedness now:
If you have 50ml of water (measured in a measuring cylinder, perfectly) and 50ml of alcohol (ethanol, measured in a measuring cylinder, perfectly) and pour one into the other, you will have 96ml of liquid. But why?
The moon rotates around itself and the earth, at least if you're looking at the moon from the earth. Otherwise it's more the barycenter of the moon earth system. From earth you don't see any rotation of the moon around itself because it's a bound rotation which means, the moon is doing a full 360° rotation in the same time he needs to rotate around earth (in something about 27 days) as well.
This dynamic relationship between moon an earth is very important because it's stabilizing, keeping up the speed, of our earth rotation, which again is very important for good life conditions. Sadly our moon is slowly drifting away from us as well.
@Shwoo
Nice link and a wonderful tune.
Does it have something to do with how when you have one bucket of sand and one bucket of water and you mix them you only have one bucket of wet sand, not two?
... Yep. That's my contribution to the thread. Sheldon's Doppler costume. Umm... "Woo, science!"?
Sitcoms about scientists are still science, okay.
The dates were too abstract for me until I made that graph and could see how much time had passed in between them. I know you were joking about the pictures, but I found that graph so helpful when I was figuring this stuff out that I thought I should post it. I was going to say that I didn't really have any pictures of the Precambrian, but I remembered that I never mentioned that phrase in my last post (it's an imformal term from the Hadean, Archean and Proterozoic eons), and I couldn't think of anything else.