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Geek Culture / Gravity

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Zotoaster
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Posted: 26th Nov 2005 16:22
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I remember once my geography teacher told me that gravity only happened because the planet kept spinign round, but that wouldn't work out because it would only throw you away. It's been a big question in my head, but how does gravity actually happen, how can you just go near a planet and get sucked in?

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David T
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Posted: 26th Nov 2005 16:35
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From a lecture I attended last week, I gathered gravity is a result of gravitons moving between objects, similar to the way light is a stream of photons.

How that relates to mass and the Higg's field is anybody's guess. But I don't think it's anything to do with the earth spinning.

Particles physics is just weird IMO. You've got to remember it's a completely different world down there, and the best particle physicists in the world just think in terms of equations - trying to impose our perception of how we see things is just impossible!

As my chemistry teacher says - "the best model of how real life works is real life. Trying to understand it completely is suicide".

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come on now. A book. I hate books. book is stupid. I know that I need codes but I dont know the codes"
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Zotoaster
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Posted: 26th Nov 2005 16:43
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Ah... Kinda confusing. I don't understand much when scientists talk, but I know where you're coming from.

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Me!
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Posted: 26th Nov 2005 16:46 Edited at: 26th Nov 2005 16:54
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your geography teacher must have been on something during teabreaks, massive objects put a curve in spacetime, like a heavy cannonball stood in the middle of a trampoline would curve the sheet, so anything near it (stood on the sheet) slides down the curve towards the object, in real terms the Earth revolves very slowly, takes it a whole day to revolve once, so even at the equator the centrifugal force is very small compared to the gravity caused by the mass of the earth, even so, gravity is one of the weakest forces in the universe, the mass of an entire planet isn`t enough to stop you standing up or jumping when you want to, gravity has one big advantage over the other more powerful forces though, it works over immense distances, so even though it is weak it has an effect on objects from close up right up to the other side of the Galaxy, the Earths spin has nothing to do with gravity, the moon has no spin but has gravity for example, the spin of the Earth combined with the metalic core does help to create the earths magnetic field that sheilds us from radiation etc, but that has nothing to do with gravity.



from above post..Gravitons are hypothetical particles, they have never been detected or measured, they are just part of quantum theory and probably wrong since a graviton could carry information out of a black hole for example and create a naked singularity, that would cause big problems for everyone, effectivly making it possible for anything to happen in the universe without cause or effect since it prevents physical laws from working (physical laws don`t work inside singularitys).

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flibX0r
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Posted: 26th Nov 2005 16:52 Edited at: 26th Nov 2005 16:54
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Ok, really simple method of trying to understand it:

Just pretend that every bit of matter in the universe pulls every other bit of matter towards it. Thus planets hold people and atmospheres on them because they are a crapload of matter in a relatively small area (relative I say)

The earth rotating thing is bollocks, your geography teacher is smelly. Now, rotating space stations on the other hand, they do simluate gravity (using the understanding you have of centrifugal force (I know it's not a real "force")). As the space station rotates, your body wants to keep going straight, but the floor is in the way, so it feels like you are being pulled towards the floor, when in actualy fact the floor is being pushed into you (lucky for us we can't tell the difference)

Though I have always wondered what would happen if you jumped...


EDIT:
Quote: "massive objects put a curve in spacetime, like a heavy cannonball stood in the middle of a trampoline would curve the sheet, so anything near it (stood on the sheet) slides down the curve towards the object"


I always loved that explanation - uses gravity to describe gravity



You can't wield supreme executive power just because some watery tart threw a sword at you
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David R
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Posted: 26th Nov 2005 16:55
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Quote: "your geography teacher must have been on something during teabreaks, massive objects put a curve in spacetime, like a heavy cannonball stood in the middle of a trampoline would curve the sheet, so anything near it (stood on the sheet) slides down the curve towards the object, in real terms the Earth revolves very slowly, takes it a whole day to revolve once, so even at the equator the centrifugal force is very small compared to the gravity caused by the mass of the earth, even so gravity is one of the weakest forces in the universe, the mass of an entire planet isn`t enough to stop you standing up or jumping when you want to, gravity has one big advantage over the other more powerful forces though, it works over immense distances, so even though it is weak it has an effect on objects from close up right up to the other side of the Galaxy, the Earths spin has nothing to do with gravity, the moon has no spin but has gravity for example, the spin of the Earth combined with the metalic core does help to create the earths magnetic field that sheilds us from radiation etc, but that has nothing to do with gravity.
"


In other words Zotoaster, google general relativity. You'll get a far friendlier answer


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Me!
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Posted: 26th Nov 2005 16:57 Edited at: 26th Nov 2005 16:58
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LOL, recursion comes in handy for more than software

eh? is that an unfriendly answer?



Do parachute manufacturers have a refunds policy?
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David R
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Posted: 26th Nov 2005 17:02
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No, just a bit confusing. I've been told some GCSE revision sites offer up some pretty good little flash demo's too


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Zotoaster
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Posted: 26th Nov 2005 17:43
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Oh.. hang on, are you guys talking about einsteins theory of relativity - or something, I could swear i heard of somrthing about the bigger the mass the bigger it would push down the "trampoline" and everything would roll into it

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Peter H
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Posted: 26th Nov 2005 17:54
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Quote: "google general relativity."

but that covers so much more then just gravity...

"We make the worst games in the universe..."
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BenDstraw
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Posted: 26th Nov 2005 18:37
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the mass and distance of the object effect gravity as well according to Newton this was expanded upon by Eienstein

bored read my http://bendsthoughts.blogspot.com/
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Wiggett
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Posted: 26th Nov 2005 23:54
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Quote: "the mass of an entire planet isn`t enough to stop you standing up or jumping when you want to"

yet it has enough power to pull you down from a big height at 9.8 meters per second.

http://www.angelfire.com/wizard2/spacerecon/index.html
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MiR
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Posted: 27th Nov 2005 00:07
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mm. I think your geog teacher didn´t understand his physics lessons. The graviational force of a planet can be equalled to the centralfugicaly force if we pretend a planet is perfectly round and the mass orbiting it is is doing so in a circular motion. That doesn´t mean that Fg=Fc. It just means that it has the same value under those circutances as a force that we invented to explain what happens when you spin something around and around.

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blanky
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Posted: 27th Nov 2005 02:11
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@Me!:

Quote: "that would cause big problems for everyone, effectivly making it possible for anything to happen in the universe without cause or effect"


Ah, so that's why my DBP code wouldn't compile.

16-colour PNGs pwn.
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Eric T
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Posted: 27th Nov 2005 21:46
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Gravity? Only witches obey the laws of Gravity...

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Darkbasic MADPSP
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Posted: 27th Nov 2005 21:52
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We got his lecture at school gravity the moon and the earth lol

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Pete Wylie should be famous
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Posted: 27th Nov 2005 22:37
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I think your geography teacher should be sacked!

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Drew Cameron
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Posted: 28th Nov 2005 01:08
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Quote: "Ah... Kinda confusing. I don't understand much when scientists talk, but I know where you're coming from."


Can't be bothered reading what everybody else said, but

Everything has gravity; gravity that draws everything else to it. The greater the mass (weight really) of an object, the greater it's gravity (pull on other stuff).

You in fact have gravity, but it is very weak. A black hole has suck great mass that it pulls itself into itself, and a sun is so massive it makes things orbit near it etc...

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Drew Cameron
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Posted: 28th Nov 2005 01:11
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Also, also

Quote: "the mass of an entire planet isn`t enough to stop you standing up or jumping when you want to"


Quote: "yet it has enough power to pull you down from a big height at 9.8 meters per second."


Big deal that it pulls you down. A paper magnet can pick up a paperclip, thus defeating the gravity of an entire planet.

Gravity is the most budget force of all. All hail magnetism!

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Megaton Cat
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Posted: 28th Nov 2005 01:16
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I have a more pondering question: How can a normal House Fly, fly around in a moving train? The fly never lands on anything, yet it can't be travelling as fast as the train itself? (60-70mph)


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smoked
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Posted: 28th Nov 2005 01:50 Edited at: 28th Nov 2005 01:51
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@ me!


Quote: "the moon has no spin but has gravity for example, "


The moon has no spin...lmao ... why do you think we always see the same surface of the moon?


[href]
http://www.wonderquest.com/MoonSpin.htm[/href]
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dark coder
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Posted: 28th Nov 2005 01:52
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because the air in the train is moved aswell? unless you have some strange train with big holes either end then yes the fly would fly right out.


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Perokreco
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Posted: 28th Nov 2005 02:34
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Becaus fly had to lift of from somewhere inside the train and when she did she already had th speed of the train
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Wiggett
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Posted: 28th Nov 2005 03:02
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I'd have to say air pressures as well. I mean it's the saem reason why we don't all die when we travel in an Air plane.

http://www.angelfire.com/wizard2/spacerecon/index.html
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Megaton Cat
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Posted: 28th Nov 2005 03:06
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Quote: " Becaus fly had to lift of from somewhere inside the train and when she did she already had th speed of the train"


It doesn't matter if it stops then lifts on again. That momentum won't carry it for 25 minutes.

Quote: " because the air in the train is moved aswell?"


I don't think that's it either. Although the fly does have advantage seeing there's less air friction to deal with...


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Benjamin
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Posted: 28th Nov 2005 03:08 Edited at: 28th Nov 2005 03:09
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Quote: "That momentum won't carry it for 25 minutes. "

That's because there is no great force pushing it back, as everything inside the train moves at the same speed as the train itself, including the air. It would be different if the train didn't have sides, as air from outside would be passing through the train, but since it does have sides, everything is fully contained inside.

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Antidote
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Posted: 28th Nov 2005 03:10
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Yay time to explain string theory! Ok basically what string theory is, is a way of looking at the universe different from the two ways that were widely debated over up until the late 90's. There was the theory that matter 'bent' time and space. Thus created gravity in the way a marble will roll into a hole in the ground. The other explanation was quantum mechanics. Quantum mechanics look at everything through probablity. Anything could happen in the universe if you waited long enough. Any action that could possible occur had its own odds. If you continued to push on a wall in a quantum mechanistic world and waited for very close to an eternity then you would eventually pass through the wall. However, both ways could not be explained completely. The theory that time and space were flat until matter made sense at first, but since constant experimentation showed that some things did rely on chance the flat time/space world was just to flat and didn't fluctuate enough. If you looked at the other side of things you saw a crazy world where since everything was based on chance the peaks and vallies of the continum would randomly spike and lower at undetermined intervals. String theory looked at both and combined them. It smoothed the crazyness of quantum mechanics and put it into the flat t/s theorum and created a gentle wave effect. String theory says that there are small particles called strings that effect the physics around us. Gravitons are the gravitational particle. They float above and attach themselves to matter. When floating freely they are full loops but when attached to matter become half-loops. No one knows exactly why or how gravitons attract matter, but it happens. Various other particles exist but I wont get into them since I feel like I've been rambling.



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Jeku
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Posted: 28th Nov 2005 10:51
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Quote: "I have a more pondering question: How can a normal House Fly, fly around in a moving train? The fly never lands on anything, yet it can't be travelling as fast as the train itself? (60-70mph)"


This is due to the fact that there is no resistance inside the train--- because it's sealed. The same reason you don't fly back in the opposite direction the train is moving if you jump Let's see a fly scoot around on a train with no walls.

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Lukas W
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Posted: 28th Nov 2005 12:40 Edited at: 28th Nov 2005 12:43
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Quote: "the mass of an entire planet isn`t enough to stop you standing up or jumping when you want to"

if you were standing on Jupiter (pretend doesn't have a gass surface) you wouldn't be able to stand straight. you would break your bones.
you wouldn't even be able to move at all.

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Me!
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Posted: 28th Nov 2005 13:30 Edited at: 28th Nov 2005 15:29
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Quote: "@ me!

Quote: "the moon has no spin but has gravity for example, "

The moon has no spin...lmao ... why do you think we always see the same surface of the moon?
"


I was simplifying for the sake of the argument, if it realy stresses you then change "no spin" to

"almost no spin (once aprox every 28days or 0.000025rpm)"

feel better now?, theres always someone has to pick up on some triviality that realy has nothing to do with the argument



Do parachute manufacturers have a refunds policy?
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Fallout
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Posted: 28th Nov 2005 14:02 Edited at: 28th Nov 2005 14:04
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hehe. My turn ...

The fly thing ...

In this situation, when the train accelerates, the fly would indeed fly to the back of the train. If a fly was stationary and a train was doing 100mph and you teleported the fly inside the train, it would hit the back of the train at what looked like 100mph. Time to quote the joke ...

Quote: "What's the last thing that goes through a fly's mind when it hits your car windscreen? It's ass."


However, the train accelerates slowly, so even though the fly is sent to the back of the train by the force, its quite easy to overcome. It's the same as you feel yourself being pushed into the back of the seat, although its very slight. This is your inertia (unwillingness to accelerate (you lazy bastard)). You're not really experiencing a force pushing you back .. more a case of you're not moving forward, so you're experience a force trying to push you forwards.

Assuming the fly's arse didn't go through its head and the train has reached 100mph, the fly now has a forwards momentum of 100mph the same as the train does. Because the air in the train is static, there are no wind forces to suck the fly backwards. Because the fly is travelling with the train in a non-wind-resistance effected environment, having been gradually accelerated up to this speed by the train accelerating, the fly can happily move up and down the train as if static. If the fly hover, it is not stationary, it is going 100mph.

The same applies to you. The earth takes 24hours to rotate, and has about a 27,000 miles circumference. Therefore, you are at this moment travelling at well over Mach 1. However, because your body has always existed on this earth, your particles have always been travelling at this speed, so you experience no acceleration forces and gravity keeps you on the ground. If you were in space stationary and then teleported onto the earth surface, you would be effectively travelling over Mach 1 in the opposite direction to the earth's spin. When space rockets enter the earths atmosphere, they have to come in at certain angles and speeds to penetrate the atmosphere and counter the rotational velocity of the earth.

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blanky
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Posted: 28th Nov 2005 17:28 Edited at: 28th Nov 2005 17:28
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Quote: ""almost no spin (once aprox every 28days or 0.000025rpm)""


0.000025rpm?! Some days, my hard drive seems to go about that speed.

*continues to annoy people who are trying to take the subject seriously*

16-colour PNGs pwn.
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