Helping members understand the physics of Space.

Originally posted by davidgrouchy
If the trend was so universal as the feeble-man-made-satallite detour tries to assert,
then why aren't all the moons tidaly locked?

See, you play word games, you ASSUME something is odd rather than ask an honest question. Your question there isn't honest, you don't want to hear the answer, you want to raise doubt in the minds of others who don't know as much about astronomy. That's precisely why you were playing word games. I find it revolting.

For those who actually want the answer, the time it takes for a moon to become tidally locked is inversely proportional to its radius.
t lock = (w*a^6*I*Q)/(3*G*mp^2*k*R^5)
t lock = time to tidal locking
w = initial spin rate of the moon
a = semi-major axis of the moon's orbit
I = moment of inertia of the moon
Q = dissipation function of the moon.
G = gravitational constant
mp = mass of the parent planet
k = Love number of the moon
R = radius of the moon

I too am curious if in fact a large asteroid hit earth and is the reasoning behind our moon. So the planets with more than a couple moons were then hit by multiple asteroids all not effecting the previous moon formation. I guess my point is how were all the other planets moons formed, or do we not know factually and can only speculate...? This is all very confusing in some parts. I think there all a lot of basic factors for me to learn before I can understand velocities and vortex's. Thanks so far to everyone that has posted in this thread. It wil be a huge referrence point for me to stop in and re-read to instill meaning in all of this.

David, you need to review the link I provided for two Saturian moons Epimetheus and Janus to find what I believe your challenge is, a perfect 1:1 orbital resonance.

When Epimetheus and Janus trade orbits without colliding, the distance isn't an exact trade, its directly proportionate to the bodies mass, Janus being the larger of the two moons doesn't orbit as far away as Epimetheus does when its in the larger orbit, and also tidally locked with Saturn.

One moon orbits 50 km (31 miles) higher (farther away from the planet) and consequently moves slightly slower than the other. The slight velocity difference means the inner satellite catches up to the other in approximately four Earth years. Then, the gravity interaction between the two pulls the inner moon faster moving it to a higher orbit. At the same time, the catching-up inner moon drags the leading outer moon backward so that it drops into a lower orbit. The result is that the two exchange places, and the nearest they approach is within 15,000 km (6,200 miles). During the 2010 trade off the Epimethean orbital radius dropped by approximately 80 km (50 miles), while Janus increased by only approximately 20 km (12.4 miles). The Janus orbit changes only a quarter of the Epimetheus change because Janus is four times more massive than Epimetheus.

reply to post by davidgrouchy


All I said it seemed like a useful thread which turned p!ssy, your comment provides why. Not everyone knows or has the time to research everything. I enjoy informative threads and learn as much as possible were I am interested in doing so. No reason to belittle others for their lack of it which they are learning.
The blatant fear mongering lies need to be called out and usually are within time.

reply to post by mugger


Thank you for your response and of course I agree. I have this thread bookmarked in my phone's browser. This way I can continually practice muscle memory with the facts contained in it.

This question just hit me also. Going back on the history of Earth. So the Earth was formed in the solar dust cloud over a loooonnngg period of time. Eventually resulting in one big rock covered in magma due to friction caused my constant collision. My question is this: Before our oceans filled up (meteorites carry salt crystals with drop of water in them. Hitting eath trillions of times) How did our moon act before tidal locking (With no ocean to lock it). Or is there a glitch in my recount of history?

Another question lol: Would global warming have a large effect on lunar orbit or 'tidal locking' with Earth?

reply to post by jeenyus2008


Liquid oceans and orbital tidal locking are completely unrelated.

Originally posted by Illustronic
reply to post by jeenyus2008

 

Liquid oceans and orbital tidal locking are completely unrelated.

I thought I read another poster say the oceans on our planet do in fact have an effect on our moon, because of the pushing and pulling motion of the water (Gravity?). Are you saying this is wrong, and the tide of the ocean wouldn't effect lunar position/orbit?



If the moon is constantly at a small rate getting further from us, what will that eventually lead to??

Originally posted by jeenyus2008
2) In lamence terms can someone explain why we have seasons, the way our moon orbits us, and how the planets orbit the sun?

This was already addressed, but I'd like to add a few things to it in relation to the moon. As mentioned, seasons are driven by our axial tilt. Our moon orbits us inclined to both our equator and to the ecliptic, and it orbits in an elliptical orbit. The inclination of its orbit is the reason why we don't have a solar and lunar eclipse every month, but we do have them when the moon's orbit intersects the ecliptic at the time of a new moon or full moon. The elliptical nature of its orbit means that it sometimes closer to earth and sometimes farther away, but the phase it's in at its farthest or closest point varies over time; the orbital period (27.3 days) is not the same as the synodic month (based on the moon's phases, an average of 29.53 days). The moon's elliptical orbit also precesses eastward once every 9 years due to solar tidal forces. Not only does the earth exert a tidal force on the moon, which is why it's tidally locked, so too does the sun. This means that the time it takes the moon to go from perigee (the closest point to earth) to apogee (the farthest point from earth) and back again to perigee takes slightly longer than the actual time it takes to orbit the earth once. We call this the anomalistic month.

reply to post by ngchunter


Thank you for adding that! I actually am starting to understand it all little by little. There are a few words that I will have to gander into. So Tidal Locking is or isn't in response to our oceans??

reply to post by jeenyus2008


Effects are not causal.

Some insight on another idea; Jenny, water is a bind, a molecular bind that wants to happen, between 2 of the 3 most plentiful elements by mass in the Universe, hydrogen, (1) first, and Oxygen (8) third. Helium (2) is the second most abundant element in the universe.

10 most abundent elements.

Our oceans weren't filled by comets, water came from the earth, our atmosphere kept it from being lost to space, protected by the magnetosphere. A fortunate snowball effect with a delicate balance.

The mass of surface water compared to the mass of the entire planet earth is a negligible percentage of the total mass, mass and proximity between two bodies is all that is necessary for tidal friction, water being an element, as related as chocolate is.

Originally posted by jeenyus2008

Originally posted by Illustronic
reply to post by jeenyus2008

 

Liquid oceans and orbital tidal locking are completely unrelated.

I thought I read another poster say the oceans on our planet do in fact have an effect on our moon, because of the pushing and pulling motion of the water (Gravity?). Are you saying this is wrong, and the tide of the ocean wouldn't effect lunar position/orbit?


If the moon is constantly at a small rate getting further from us, what will that eventually lead to??

Water does contribute to the overall gravity of earth, but is not necessary for the earth to have gravity. In fact, it's only a tiny fraction of the earth's total mass. The tide of the ocean is an effect of the moon's tidal force exerted on earth. It's just the opposite effect that has caused the moon to become tidally locked; the earth's gravity has a tidal effect on the moon. All that means is that the near side of the moon experiences more of earth's gravity than the far side due to the fact that gravity decreases with distance squared. As the moon rotates with respect to the direction of this tidal force, it causes friction and dissipates the moon's rotational energy until its rotational period reaches a state of equilibrium; the point at which the rotational period equals the orbital period.

This also happens with the earth due to the moon's tidal force on the earth, but because we're much more massive than the moon, the tidal braking effect of our rotation is much more gradual and we are not tidally locked to the moon. Over time our rotation does slow, but this energy is not destroyed, in fact it's the reason why the moon is gradually getting farther away from earth. Over a long period of time this will eventually mean that there are no more total solar eclipses as the moon will be too far away to completely cover the sun.

reply to post by Illustronic


Ahh! So Earth oceans are effected by the Tidal Locking of the moon and Earth, causing gravity to pull certain elements that have strong surface tension/bonds. I'm really sorry if I come off dumb to anyone, this stuff is difficult to comprehend on such a vast scale. I would at this point like to encourage people to continue asking questions they may have whether easy or impossible to answer. Thank you for being sincere in replying to me.

Originally posted by jeenyus2008

If the moon is constantly at a small rate getting further from us, what will that eventually lead to??

Earth rotational/lunar orbital equilibrium. If the sun lasts long enough, several billion years from now, a day will last as long as a lunar orbit, a day will equal a lunar month. This is somewhere around 55 days. I had a link long ago. At this point the moon will no longer recede from earth, and the earth's rotation will not further slow, if the sun lasted forever like it is now, the earth rotation and lunar orbit would stay the same forever.

This is purely a mathematical calculation projection, it can never happen in reality.

The old adage; "The older you get the days get longer but the years get shorter", is astronomically true!

reply to post by ngchunter


I especially like the part of the equation; 'Love number of the moon'.

reply to post by jeenyus2008


Oh, I should have found this thread earlier... I *LOVE* explaining Science...

*SCIENCE!!!!!*

1) When you look up at the stars, there are so many different of objects shining (I understand some are planets, some are stars). My question is how come most are a bright fluorescent white dots, and some are a bright orange?

This is caused by various factors:

1: Spectral Luminosity.



The above picture is the Emission spectrum of 3 different elements (Top to Bottom: H(Hydrogen), Hg(Mercury), Ne(Neon)) and the Absorption spectrum of H(Hydrogen) at the bottom.

These images are basically made by heating the element to "White Hot" and shining it's light through a prism...

the lines are the specific Wavelengths (Colors) of light that these specific elements give off when they are Really hot.

The Emission spectrum of an element is dependant upon it's temperature.... If the object is just Sort of hot, it will emit the light from the red end of the spectrum, and as it's temperature increases, the spectrum gradually starts to include the wavelengths closer and closer towards the blue end of the spectrum.

This is known as the "BlackBody" curve:



As the Temperature of the object in question increases, the wavelengths that it emits includes shorter wavelengths (higher energy)

So, Each element has a specific Spectral Emission signature.... Hydrogen is going to emit the exact same wavelengths no matter where it is in the universe, so long as it is hot enough to emit them.

Likewise, Helium, Beryllium, Carbon, Oxygen, etcetera all have their own unique emission spectrum.

So, the primary cause of the stars being of different colors, is their elemental composition and temperature, which is somewhat dependant upon their age.

Young stars are mostly Hydrogen, with secondary fusion products including the light elements (H + H + H + H = Helium), (Helium + Hydrogen = Lithium) etcetera, etcetera.

So, as the star gets older, its composition becomes less "Just Hydrogen" and more "Hydrogen plus other stuff"

Also, you are only seeing the Surface of the star, so if the surface temperature is something like 10,000 Celsius, you are going to get the whole emission spectrum of the hydrogen shining.

IF the surface temperature is less than that, like 3,000 Celsius, You are only going to get the wavelengths towards the red end of the spectrum.

Your Red Giant stars have mostly used up their hydrogen, and are thus colder, and have lots of different elements in them.

So, I guess the easiest way of saying it is that...... For the same reason White hot metal and Red hot metal glow different colours, it's mainly because of the temperature difference.

2) In lamence terms can someone explain why we have seasons, the way our moon orbits us, and how the planets orbit the sun?

The Earth is tilted about 23.5 degrees, and it's always tilted the same way....

So, for half of the year, the north pole is tilted towards the sun, and for the other half, the north pole is tilted AWAY from the sun.

This is what causes the sun to appear to "Drop" on the horizon during the winter, and climb higher in the sky in the summer.

And this is what causes our seasons.... because the earth's atmosphere is about 125 kilometres thick.

IF the sun is shining directly overhead, the light only has to pass through 125 kilometers of atmosphere....

But if the sun is at an angle to the atmosphere over your head, the light has to travel through more atmosphere, and thus it's heat is absorbed more.

When the sun is high in the sky, more of it's heat makes it to the surface... when the sun is low in the sky, less of it's heat makes it to the surface.





Tidal locking essentially occurs because the gravitational force of the earth diminishes as your distance from the earth increases.

This causes the Gravity of the earth to be Greater on the side of the moon that is closer to the earth, that it is on the side that is farther away from the earth.

This unequal distribution of gravitational force causes a *SLIGHT* distortion of the shape of the moon... causing it to be sort of oval shaped (Very *VERY* small effect... you wouldn't be able to notice it.)

Anyway, this creates counter-torque on the moons rotation, which would slow it's spin until it stops rotating relative to the earth. (Same side always facing the earth)

The same thing happens to the earth, the moons gravity causing the earth to reshape into a sort of oval that is always pointed towards the moon....

Luckily, the Oceans are pretty fluid, and they do most of the Reshaping.... this is what causes tides.

reply to post by jeenyus2008

3)When you look up pictures of a Nebula is that how we would see it (With all the neon colors) or would it not be so glorified? Could we even look directly at one?

IT really depends on which specific picture you are talking about....

Most nebula photos are taken by a time exposure process, and a lot of them are taken in 3 different colours (Red, Green, Blue) over three separate exposures, and then composited together.

Some other nebula pictures use False colours (For example, making Infra-red into a Red hue) and then composited that way...

And you wouldn't be able to see the infra-red... but yeah, I'd say that most pictures of nebula are pretty much exactly as you would see them with your own eyes, if you were close enough to them.


Furthermore, When two bodies are locked in a gravitational orbit with eachother, they actually orbit around the "Barycentre" (Gravitational centre of mass) of both objects.



When something is orbiting something else, it is because the force of gravitational acceleration Attracting the orbiting body (The Small thing)) to it's primary (The big thing) is equal to it's sidewards motion.... Thus, it "Falls" in a big circle around the primary, and constantly misses it, because it curves away from it as the satellite falls towards it.

The easiest way to put it is Issac Newton's "Cannonball" thought experiment...



IF you fire a cannonball, it wants to fly in a straight line, but the gravity of the earth curves the path of the cannonball towards the earth.

IF you fire it faster, the gravity has less time to curve the path of the cannonball, so it travels farther before it ultimately hits the earth.

And if you fire it FAST enough, the surface of the earth will curve away from the cannonball at the same rate that the cannonball curves towards the earth.

Thus, the cannonball will constantly "Fall" towards the earth, and yet never hit it.


This is called an Orbit.

reply to post by ErtaiNaGia


The Hubble Spectrum will indeed enhance what is out of our visual spectrum. But I especially like your previous post. To think Neon (Atomic Number 10), is the forth most abundant element in the universe has me wondering of what intrinsic purpose does neon serve in my daily life, I conclude it helps me find the local pub!

Stay thirsty my friends.

reply to post by ErtaiNaGia

That really helps. Thank you. Are you a teacher? The way you explained those concepts really helps me understand it in a easier way.

Sorry to everyone. I'm at home now and do not have a desktop computer. Im on my mobile and will be replying with more questions

Originally posted by metalshredmetal
reply to post by jeenyus2008

 

3) the colors that show in pictures of nebulas are not real colors. they are colors that are assigned to different chemicals in the nebula, like oxygen might be assigned blue, nitrogen red, etc. this is digital computer magic to make them look pretty, and visually separate the different gases.

Not entirely true. Some do take filtered shots and add back in the colors. However, in the shots I have made, long exposures show the colors.