Can Dark Matter and Black Holes be Associated in Earth's Rotation?

[thinkies]

......so,what makes Earth rotate...I believe I'm still in my *discovery*phase(normal for a 15 yrs old..)...sry if this is a newbish question...

I though looking on the internet..but so lazy and beside i will prob. not understand with they complicated terms and stuff they'll use to explain...o.0

also,i dun know if this makes sense or not,but can we assosiate dark matters with black holes...in someway,such as...dark matters can not be be seen and if I am not wrong they don't even show any signs of energy(if they had,im sure they would produce some sort of gamma rays or w/e,=.=right?)..whereas black holes,we know they exist,yet...still many mysterious facts remain...

? so confused...o.0
hmmm any books recommendation...I was wondering to take some books and learn basics(very very very basic stuff...)about quantum mechanic(are they even useful in astrophysics?)..

Thx:D

 

[thinkies]

...

hmmmm......
so..

 

[Woozie]

When the solar system was formed, the matter had angular momentum. When the matter clumped together, the angular momentum from the individual pieces of matter had to be conserved, so things formed from this matter (like planets and even the sun itself) rotates.

 

[DaveC426913]

Dark matter was hypothized as an explanation of why we see galaxies holding together while rotating too fast to do so. The only thing that seems to explain it is if the galaxies have more mass than we see. Not sure if that helps.

 

[thinkies]

woha...i dun think that i got wut you guys really are sayin...umm..then how come its still rotating...i mean,theres something...or else ..it wouldn't be rotating since all those years that passed...right? o.0btw,im not even sure if i get this 'angular momentum'...and why did the matters had angular momentum when the solar system formed?

and...hmmmmmm exactly how did we find out the existence of dark matters...?

 

[OmCheeto]

woha...i dun think that i got wut you guys really are sayin...umm..then how come its still rotating...i mean,theres something...or else ..it wouldn't be rotating since all those years that passed...right? o.0btw,im not even sure if i get this 'angular momentum'...and why did the matters had angular momentum when the solar system formed?

Well, it's like a big ol' gyroscope in a vacuum.
Once you get it going, there's nothing to slow it down. (except for the moon of course)
You really need to do the math:

earth mass = 6e24kg
earth radius = 6.371km
rotational speed = 24 hours

um... I'm not near my calculus book at the moment ...

and the web seems to be a bit light on spherical gyro's today,

and...hmmmmmm exactly how did we find out the existence of dark matters...?

That's still way out there so I'll wait till morning to attempt an answer.

 

[DaveC426913]

I think we would be a lot more willing to discuss this with you if you made an attempt to write intelligibly. It sort of feels like we're entertainnig a drunk.



In our everyday world, we are used to seeing spinning objects gradually slow down and stop - like a spinning top running down. But this is actually the exception to the rule. Newton's first law states that 'things in motion will tend to stay in motion unelss acted upon by an outside force'.

Things slowing to a stop happens usually because of friction - in the case of the top, friction with the table it's on and the air. If the top were set spinning out in space, it would spin forever.

So it is with the Earth.

All that being said, the Earth is actually slowing down; it's just taking billions of years to do so. If you notice, the Moon has slowed to a stop (with respect to Earth at least)

 

[OmCheeto]

I think we would be a lot more willing to discuss this with you if you made an attempt to write intelligibly. It sort of feels like we're entertainnig a drunk.



In our everyday world, we are used to seeing spinning objects gradually slow down and stop - like a spinning top running down. But this is actually the exception to the rule. Newton's first law states that 'things in motion will tend to stay in motion unelss acted upon by an outside force'.

Things slowing to a stop happens usually because of friction - in the case of the top, friction with the table it's on and the air. If the top were set spinning out in space, it would spin forever.

So it is with the Earth.

All that being said, the Earth is actually slowing down; it's just taking billions of years to do so. If you notice, the Moon has slowed to a stop (with respect to Earth at least)

I swear to god I just said all that a minute ago...
in different words of course.

 

[DaveC426913]

I swear to god I just said all that a minute ago...
in different words of course.

Yes, you just beat me to the post.

 

[OmCheeto]

Yes, you just beat me to the post.

so do you know where to find spherical gyroscopic equations outside of my old textbooks?
It's a question that's been going around for a day or two.

 

[DaveC426913]

so do you know where to find spherical gyroscopic equations outside of my old textbooks?
It's a question that's been going around for a day or two.

Uh, you got me. :shy:

Formally, I only have a high school level of ecucation in math - I barely passed Calculus. Thirty five years of reading has alloowed me to understand much of physics, but I don't really have the skills to do the formulae. Pity.

 

[Quincy]

o.0btw,im not even sure if i get this 'angular momentum'

You know if you spin on a... spinning chair or w/e with your arms/legs out, and then you turn your arms/legs in, the chair spins faster; that's angular momentum.

All that being said, the Earth is actually slowing down; it's just taking billions of years to do so. If you notice, the Moon has slowed to a stop (with respect to Earth at least)

Isn't that because it's tidally locked to Earth?

 

[LURCH]

Isn't that because it's tidally locked to Earth?

Yes, exactly. And, in the same way, the Earth is becoming tightly locked to the moon. This year takes 24 hours to complete one revolution, the moon orbits and much slower pace, taking 28 days to complete one orbit. Because of this, the gravitational attraction between the Earth in the moon is causing the moon to act like a break and slow the Earth's rotation, while simultaneously speeding up the moon's orbit. Given enough time, these two would eventually become synchronous, and the moon would occupy one spot in the sky always, without moving.

 

[thinkies]

well...let see if i really get it.
Basically,the Earth rotation begun when this solar system formed and it had this angular momentum.

It it is still rotating becuz of some Newton law,since there is no force in space,theres nothing to stop it.right? o.0...im very very slow at understanding :P

However,there is something i am not understanding.How canthe moon be affecting Earth rotation exactly...?

 

[Quincy]

well...let see if i really get it.
Basically,the Earth rotation begun when this solar system formed and it had this angular momentum.

It it is still rotating becuz of some Newton law,since there is no force in space,theres nothing to stop it.right? o.0...im very very slow at understanding :P

However,there is something i am not understanding.How canthe moon be affecting Earth rotation exactly...?

If you spin a top on Earth, it's eventually going to stop because of Earth's gravity right? Well, the rotation of the Earth is eventually going to stop because of the Moon's gravity.

 

[D H]

so do you know where to find spherical gyroscopic equations outside of my old textbooks?

Newton's second law of motion, \mathbf F=d\mathbf p/dt, is \mathbf \tau = d\mathbf L/dt, where \mathbf \tau is the total external torque and \mathbf L is the angular momentum expressed in inertial coordinates. The linear momentum of some body is given by \mathbf p = m\mathbf v. Similarly, the angular momentum of some rigid body is given by \mathbf L = \mathbf I\mathbf \omega. There is a complication with this latter expression. We typically represent the inertia tensor \mathbf I and the angular velocity \mathbf \omega in rotating coordinates rather than inertial coordinates. In a coordinate frame rotating with the body in question, the inertia tensor for a rigid, constant mass body is constant. This is not the case for the inertia tensor expressed in inertial coordinates.

Any decent junior-level (college) classical dynamics text will cover the relationship between derivatives of vector quantities in rotating and nonrotating frames:
\frac {d\mathbf q}{dt_{\text{fixed}}} = \frac {d\mathbf q}{dt_{\text{rot}}} + \mathbf \omega \times \mathbf q
where \mathbf q is any vector quantity. Some call this the transport theorem (not to be confused with the Reynold's transport theorem), some (e.g., Marion, Classical Dynamics) don't bother to give this relationship a name. (Marion does a lousy job proving it, BTW). Apply this relationship to the angular momentum vector:
\mathbf \tau = \frac {d\mathbf L}{dt_{\text{fixed}}} = \frac {d\mathbf L}{dt_{\text{rot}}} + \mathbf \omega \times \mathbf L = \frac {d}{dt}(\mathbf I \mathbf \omega) + \mathbf \omega \times (\mathbf I \mathbf \omega)
If the inertia tensor is constant in the rotating frame (and it is for an ideal rigid body), the inertia tensor comes out of the derivative. Solving for the time derivative of the body rate,
\mathbf I\dot{\mathbf\omega} =\mathbf \tau - \mathbf \omega \times (\mathbf I \mathbf \omega)

These are "[URL equations[/URL], just written a lot more compactly than usual.

 

[DaveC426913]

However,there is something i am not understanding.How canthe moon be affecting Earth rotation exactly...?

If the Earth were prefectly circular and perfectly rigid, it could not.

But the Moon causes lots of tiny forces of the Earth: it pulls on mountains and it sloshes water around. The net effect is friction - and a slowing of the Earth's rotation.

Think about this: You turn off a ceiling fan (so that its spinning freely with no force or friction) and want to bring it to a stop quickly. It's much faster to bring it to a stop by grabbing its blades than by grabbing its smooth, circular body. Think of the blades like the mountains and oceans of Earth.

 

[D H]

If you spin a top on Earth, it's eventually going to stop because of Earth's gravity right?

No. It will eventually stop because of friction. Friction between the end of the top and the surface on which it is resting exerts a torque on the top. Gravity itself does not exert a torque. All that gravity does is hold the top on the surface of the Earth. If you spun a perfectly rigid top in space it would spin forever.

The reason the Earth is slowing down is because of friction. The moon's gravity is a bit weaker on the side of the Earth away from the Moon than the side of the Earth facing the Moon. The tides result from this gradient in the gravitational acceleration. Friction between the rising and falling tides and the more-or-less solid Earth are what are slowing the Earth's rotation rate down.

EDIT: Dave C beat me do it. Dang.

 

[thinkies]

If you spin a top on Earth, it's eventually going to stop because of Earth's gravity right? Well, the rotation of the Earth is eventually going to stop because of the Moon's gravity.

=.=,earth's gravity is way more stronger then the moon...o.0,how can this be even possible...

 

[thinkies]

oh...i think I am getting this...but since this process may take million of yrs,in distant future,will there be a day/night concept...?(since it'll eventually slow down its rotating,as mentioned by some of you..)

also,for planets that do not have any natural satellite,will they keep rotating..for ever?

 

[thinkies]

also,this may be irrelevant wid this thread...but let's say we were to test a nuclear bomb on the moon...wut would be the consequence if it explodes on the moon o.0?is it even possible testing there? >.<

 

[DaveC426913]

oh...i think I am getting this...but since this process may take million of yrs,in distant future,will there be a day/night concept...?(since it'll eventually slow down its rotating,as mentioned by some of you..)

Certainly. Earth's prehistoric past had a much shorter day/night cycle. Shoot, I can't remember - was it as short as ten hours?

also,for planets that do not have any natural satellite,will they keep rotating..for ever?

All planets are in the gravitational grip of other planets and of the sun.

also,this may be irrelevant wid this thread...but let's say we were to test a nuclear bomb on the moon...wut would be the consequence if it explodes on the moon o.0?is it even possible testing there? >.<

Yes, this could be done. (But we wouldn't learn a lot, so there's little point.)

 

[D H]

also,for planets that do not have any natural satellite,will they keep rotating..for ever?

All planets are in the gravitational grip of other planets and of the sun.

That is true, Dave, but the time for a body orbiting about another body to be tidally lock to that second body is proportional to the sixth power of the radial distance between the two objects. The Sun will blow up to a red giant and fade to a white dwarf long before the Sun tidally locks the Earth. For the outer planets, it just won't happen.

 

[Sourabh N]

Well, I remember searching the same question(Rotation of Earth) on net, and I found that its due to the nuclear reactions going on inside earth.(Sorry, but i don't have the link to page now)

 

[Sourabh N]

Well, I remember searching the same question(Rotation of Earth) on net, and I found that its due to the nuclear reactions going on inside earth.(Sorry, but i don't have the link to page now)

 

[D H]

Well, I remember searching the same question(Rotation of Earth) on net, and I found that its due to the nuclear reactions going on inside earth.

You either misread or you read some woo-woo pyschoceramic claptrap garbage (and if you ask again, I'll tell you what I really think ).

The Earth is rotating because (a) the Earth was rotating when it was first formed, (b) angular momentum is a conserved quantity, and (c) the external torques on the Earth (i.e., tides caused by the Moon) are not large enough to have stopped the Earth's rotation.

Anything happening in the interior of the Earth does not qualify as an external torque.

 

[thinkies]

hmm...since the sun rotates too,if there was a greater attraction(more powerful then the sun)would it slow it down too...>.< or this would lead into some different scenarios...?

 

[thinkies]

bump...

 

[OmCheeto]

also,this may be irrelevant wid this thread...but let's say we were to test a nuclear bomb on the moon...wut would be the consequence if it explodes on the moon o.0?is it even possible testing there? >.<

Sorry I'm late.
This has nothing to do with nuclear bombs on the moon but does describe why the Earth keeps spinning, in a slightly more illustrative fashion.

The following assumes we could direct the energy from a nuclear blast to slow the rotation of the earth:

(energy is in Joules)

6.30E+13 energy from the Hiroshima bomb (ref 1)
2.57E+29 energy due to the Earth's rotation (ref 2)
4E+15 number of Hiroshima bombs equivalent to the Earth's rotational energy
1,440 number of minutes in a day (we're going to set off one bomb every minute)
2.83289E+12 number of day we need to explode the bombs
365.24 number of days in a year
7,756,249,086 number of years to stop the rotation of the earth.

That's 7.76 billion years setting off a nuclear bomb every 60 seconds.

So you see, there is a lot of energy stored in our planet due to it's rotation.

On a side note, I also ran across an interesting article about some spherical gyroscopes in orbit around our planet:

http://science.nasa.gov/headlines/y2004/26apr_gpbtech.htm
A Pocket of Near-Perfection
Now orbiting Earth, Gravity Probe B is a technologicaltour de force.
In this pristine, high-vacuum environment, the spherical gyroscope could spin at its operating speed of 10,000 rpm for 1,000 years without slowing by more than 1 percent.

And they are only an inch and a half across.

references
(1) http://www.carnicom.com/time3.htm kinetic energy of the rotation of the earth
(2) http://en.wikipedia.org/wiki/Megaton energy of the Hiroshima bomb

 

[thinkies]

hey,omcheeto,umm i know this will be a stupid question but let's say we were to explode a nuclear bomb on Earth's core...will it lead to some bad consequence?and what kind of consequence..?

 

[DaveC426913]

hmm...since the sun rotates too,if there was a greater attraction(more powerful then the sun)would it slow it down too...>.< or this would lead into some different scenarios...?

The sun is a gaseous body; it is not rigid at all.

 

[DaveC426913]

hey,omcheeto,umm i know this will be a stupid question but let's say we were to explode a nuclear bomb on Earth's core...will it lead to some bad consequence?and what kind of consequence..?

None.

 

[thinkies]

my bad,that nuclear thing on the Earth's core was really a stupid question...since the core produces a million time more energy then the nuclear bomb..still...i was hesitating...=.=

also,the sun does rotate right o.0,so that means that all this rotating thing we talked applies to telluric planets only??and why would the sun be rotating...(ive read about sun rotation on couple of websites...)?...

hmm thx

 

[thinkies]

hmm also...since the sun will eventually become a red giant,life will of course wouldn't be possible on earth...since this is to happen in billion of billions of years,i presume that the technology will progress to an extent where we will eventually "move" from this planet to another?

or...will this be the end of humanity...?

i know i may be asking so many questions...srry o.0,just curious..

 

[OmCheeto]

hey,omcheeto,umm i know this will be a stupid question but let's say we were to explode a nuclear bomb on Earth's core...will it lead to some bad consequence?and what kind of consequence..?

I think you ask too many questions...
But I'll answer anyways

Virtually nothing.
The Earth's size in comparison to nuclear bomb yield is incredible.
I doubt anyone would notice.
They used to set off megaton nuclear bombs out in the Pacific and the Earth hardly noticed. Except for the radioactive waste of course.

ah ha!

http://en.wikipedia.org/wiki/Underground_nuclear_testing
Plumbbob Rainier was detonated at 899 ft underground on 19 September 1957. The 1.7 kt explosion was the first to be entirely contained underground, producing no fallout.

The Earth's core is about 4,000 miles down. Thats 23,500 times deeper than the above mentioned nuclear blast.

http://en.wikipedia.org/wiki/Megaton
The largest quake registered, the 1960 Chilean quake, released almost 60,000 gigatons of TNT equivalent.

That's 600 of the mankinds biggest nuclear bombs. Did anyone outside of Chile notice that earthquake? I doubt it.

 

[DaveC426913]

my bad,that nuclear thing on the Earth's core was really a stupid question...since the core produces a million time more energy then the nuclear bomb.

You got it.

also,the sun does rotate right o.0,so that means that all this rotating thing we talked applies to telluric planets only??

We were talking about slowing of rotation. It works more effectively on rigid bodies. The initial rotation of all planets is from conservation of angular momentum

and why would the sun be rotating

Same reason.

 

[thinkies]

back with another question...

70% of the universe consist of dark energy and 25% of dark matters...since they make up most of the universe,y is that energy not observable and y do we know little about them how can this be even possible...?

 

[thinkies]

also,wut do these matters really do,how are they affecting the galaxies and other stuff.Can a black hole absorb that dark energy,or,is that dark energy present inside dark wholes ...right? then y does it remain a simple mysterious fact...

 

[D H]

The sun is a gaseous body; it is not rigid at all.

The sun still rotates, however, and it therefore has angular momentum. The same mechanism that leads to the transfer of angular momentum from the Earth about its own axis to the Moon's orbit about the Earth applies to the Sun and the planets. Several of the planets we have observed orbiting other stars are massive planets whose orbits are much closer to their parent stars than are the orbits of Jupiter and Saturn.

The Sun has about 99.9% of the total mass of the solar system, but only 0.3% of the total angular momentum. Why the discrepancy? Creationists have a silly rationale, and no, I do not ascribe to it. To scientists, the angular momentum problem is an open question but one which they think they will eventually resolve. One hypothesis is that the solar wind has robbed the Sun of much of its angular momentum. While the solar wind removes very little mass from the Sun, it can remove much, much more angular momentum.

Another hypothesis is that the massive planets originally orbited the Sun much closer than they do now. They moved to their present distant orbits by stealing angular momentum from the Sun. The recent observations of planets around other stars bolsters this conjecture: We have observed several massive planets that orbit their parent star at incredibly short distances.

 

[thinkies]

@D H

that information is quit interesting...ah,i really like astronomy...full of wonders...:D

 

[thinkies]

ummm one more questions,since all the planets in this solar system are bounded by sun's gravity,y are we not being 'sucked' by the sun rather then orbiting around it and what cause us to not move from our orbital location(others planet attraction?)...?

 

[DaveC426913]

ummm one more questions,since all the planets in this solar system are bounded by sun's gravity,y are we not being 'sucked' by the sun rather then orbiting around it and what cause us to not move from our orbital location(others planet attraction?)...?

In the classical Newtonian world, we are indeed falling towards the sun. And if we had no angular momentum, we'd simply plunge right into it. But our angular momentum (i.e. our 'sideways motion') carries us past it.

The objects that have the right angluar momentum that matches their distance form the sun have formed stable orbits. The objects that have the wrong angular momentum for their distance aren't stable, which is why mostly we don't see them in present day - they've either accreted into the sun at the SS's formation, or they been flung out into deep space.

 

[DaveC426913]

The sun is a gaseous body; it is not rigid at all.

The sun still rotates, however, and it therefore has angular momentum.

I was responding to Thinkies' comments about the sun slowing down due to friction. It works great on rocky planets. I'm not sure how well it works on gaseous bodies.

 

[RonL]

Reading this thread got the crazy part of my brain going, and i can't make it stop. Here is a link that came up in a search while trying to learn something, and as stupid as it sounds, i have to ask the question, is there any logic to the thought of trying to affect the speed of Earth's rotation??

http://stopthespin.org/action.php

 

[thinkies]

anything regarding my dark matter/dark energy questions...i will be appreciating any kind of response(and am grateful to see many ppl answering my questions :D )...

 

[OmCheeto]

Reading this thread got the crazy part of my brain going, and i can't make it stop. Here is a link that came up in a search while trying to learn something, and as stupid as it sounds, i have to ask the question, is there any logic to the thought of trying to affect the speed of Earth's rotation??

http://stopthespin.org/action.php

That website is just silly.
If they had sone some simple calculations, they would have seen vehicles are very poor devices for slowing down the planet.

Here are my calculations, once again, to stop the Earth's rotation putting everyone on the planet driving a bus that gets 1 mpg at 50 mph converting all of their energy to STOP THE EARTH!

3.46E+07 joules in a liter of gas
0.264 gallons per liter
131,060,606 joules per gallon gas
2.57E+29 Earth's rotational ke
1.96092E+21 gallons to stop planet
6.00E+09 people on the planet
3.27E+11 gallons per person
1 mpg
50 mph
50 gallons per hour
6,536,416,185 hours per person
8,766 hours per year
745,675.9 years

That's quite a bit faster than blowing up the bombs.
Kind of puts energy use by 6 billion people into perspective.

That would be quite the sight to watch though. 6 billion buses circling the Earth for 3/4 of a million years. Ah ha!
Math is fun.

 

[OmCheeto]

anything regarding my dark matter/dark energy questions...i will be appreciating any kind of response(and am grateful to see many ppl answering my questions :D )...

This is the best explanation I've ever seen of dark energy:

Dark energy - little more than a fancy name (for) our ignorance of what seems to make up about two thirds of the matter budget.

But everyone seems to have an opinion:

http://www.sciencedaily.com/releases/2008/01/080131094056.htm
Dark Fluid: Dark Matter And Dark Energy May Be Two Faces Of Same Coin
ScienceDaily (Feb. 1, 2008) — Astronomers at the University of St Andrews believe they can "simplify the dark side of the universe" by shedding new light on two of its mysterious constituents.

Dr HongSheng Zhao, of the University's School of Physics and Astronomy, has shown that the puzzling dark matter and its counterpart dark energy may be more closely linked than was previously thought.

Only 4% of the universe is made of known material - the other 96% is traditionally labeled into two sectors, dark matter and dark energy.

...

I personally have no opinion on the matter.

 

[russ_watters]

That's 600 of the mankinds biggest nuclear bombs. Did anyone outside of Chile notice that earthquake? I doubt it.

Actually, that's 600,000 of our biggest nuclear bombs.

 

[RonL]

Thanks OmCheeto
But going back to my question, the thought that jumped into my mind, was affecting the speed of Earth's rotation in archseconds, not bringing it to a stop.
As silly as that site is, it was in the first steps of my learning something new, that i have never given any real thought to before ( i'll not bore anyone with the thought of how to put an affect into play)
But again thanks for your answer.

That website is just silly.
If they had sone some simple calculations, they would have seen vehicles are very poor devices for slowing down the planet.

Here are my calculations, once again, to stop the Earth's rotation putting everyone on the planet driving a bus that gets 1 mpg at 50 mph converting all of their energy to STOP THE EARTH!

3.46E+07 joules in a liter of gas
0.264 gallons per liter
131,060,606 joules per gallon gas
2.57E+29 Earth's rotational ke
1.96092E+21 gallons to stop planet
6.00E+09 people on the planet
3.27E+11 gallons per person
1 mpg
50 mph
50 gallons per hour
6,536,416,185 hours per person
8,766 hours per year
745,675.9 years

That's quite a bit faster than blowing up the bombs.
Kind of puts energy use by 6 billion people into perspective.

That would be quite the sight to watch though. 6 billion buses circling the Earth for 3/4 of a million years. Ah ha!
Math is fun.

 

[D H]

That website is not only silly, it is wrong. Following their instructions won't change the Earth's rotation rate one bit. There will be a slight change (very slight!) in the Earth's rotation rate when the car accelerates. The car will not change the rotation rate one bit while the car is driving at a constant velocity. Eventually the car comes to a stop. This also changes the Earth's rotation rate, and the change is exactly opposed to the initial change. End result: zero change.