Register to reply

This seems kind of weird, but...is there really no such thing as gravity in

by New-Prototype
Tags: butis, gravity, kind, solved, thing, weird
Share this thread:
New-Prototype
#1
May5-03, 01:24 PM
P: n/a
Hi, I was just wondering about this because....you see how there's supposed to be no gravity in space, but i sort of think there is because of the movement found within our glaxay and our entire solar system. uhh...it's kind of hard to explain, but everyone knows about the Corneleous Effect found on Earth. Ugh...i can't spell it but it's the movement of ocean currents and it shows that ocean currents above the equator move clockwise while the currents move counter clockwise below the equator. These ocean currents are caused by gravity, right?
Well....how exactly is our milky way galaxy moving in a spiral and our planets circling around the Sun? The reason why this is happening to our solar system is simple. As we all know planets tend to orbit around those who are larger because they have a stronger magnetic pull also known as gravity. (this can include stars, right?) well, as we know, our Sun is the largest Star, therefore, the planets would orbit around it, causing the circular motion.

But why do galaxies move that way? But if there is gravity in space, where is it coming from?
Phys.Org News Partner Astronomy news on Phys.org
Mysterious molecules in space
Next-generation Thirty Meter Telescope begins construction in Hawaii
Comet Jacques makes a 'questionable' appearance
dav2008
#2
May5-03, 01:33 PM
PF Gold
dav2008's Avatar
P: 621
There is no point in space with 0 gravity.

There is always the force of gravity no matter where you go, and only at a distance of infinity from an object is its gravitational pull equal to 0...

The reason that astronauts are weightless in orbit is because they are constantly falling towards earth but the earth falls away under them at the same rate so they just move in a circle around the earth....
LURCH
#3
May5-03, 02:51 PM
Sci Advisor
P: 2,510
Wow, you ask a lot of questions NP (we like that here!).

Your initial conclusion is correct; there is indeed gravity in space. And yes, that is what makes things orbit one another. If the difference in mass between two things is great, the more massive thing will stay in one place (almost), while the lighter object orbit around it. Two objects of nearly equal mass will orbit some point between them. So the moon's goal around the planets, and the planets orbit around the (much heavier) stars. The stars in the galaxy, being of roughly equal mass to one another, just orbit a central point.

As dav was referring to, astronauts only appear weightless in space because they are going around the earth fast enough so that the outward "centrifugal" force (which is really just a form of inertia) is equal to the downward pull of gravity. The two forces back against one another so that the total result is "0", but that's not exactly the same as saying that gravity = "0".

As for the Coreolus Effect (pretty sure I didn't spell it right, either), that's not so much a gravity thing. It's a little complicated, but suffice to say that gravity only plays a minor role.

chroot
#4
May5-03, 05:55 PM
Emeritus
Sci Advisor
PF Gold
chroot's Avatar
P: 10,429
This seems kind of weird, but...is there really no such thing as gravity in

Originally posted by New-Prototype
Hi, I was just wondering about this because....you see how there's supposed to be no gravity in space
As has been explained, there certainly is gravity in space.
Corneleous Effect found on Earth. Ugh...i can't spell it but it's the movement of ocean currents and it shows that ocean currents above the equator move clockwise while the currents move counter clockwise below the equator. These ocean currents are caused by gravity, right?
The Coriolis force is essentially just a result of winds (or water currents) moving over a planet that is spinning beneath it. It makes freely moving objects make curved paths with respect to the surface of the earth. It isn't really a force at all -- it's akin to other ficticious forces: you can choose a coordinate system in a way to remove the Coriolis force.
Well....how exactly is our milky way galaxy moving in a spiral
The galaxy isn't moving in a spiral; it has a spiral shape, and things on the periphery are orbiting the center of mass.
As we all know planets tend to orbit around those who are larger because they have a stronger magnetic pull also known as gravity.
While I understand what you're attempting to say, the word 'magnetic' is not appropriate at all here. Gravity and electromagnetism are two completely unrelated phenomena (at least until we have a Theory of Everything <smirk>).
this can include stars, right?) well, as we know, our Sun is the largest Star, therefore, the planets would orbit around it, causing the circular motion.
The Sun is absolutely not the largest star. In fact, the Sun a puny, average, unimportant star -- except to us humans. What you're grappling at is the concept of 'superposition.' In other words, say you have one mass by itself. You can calculute the force vector experienced by a test mass at any point you like. You can thus describe a 'gravitational field' by expressing what the force vector is at all points in space. You can then add a second, identical mass to the system. The second mass's gravitational influence is simply stacked on top of the first ones -- the two fields can be simply added. The resulting field is just the simple sum of the two fields created by each mass -- the resulting field is the superposition of the two independent fields.
But why do galaxies move that way? But if there is gravity in space, where is it coming from?
Einstein's theory of general relativity explains gravitation as an effect of curved spacetime. In essence, mass curves space -- and space then tells mass how to move.

- Warren
RuroumiKenshin
#5
May5-03, 11:57 PM
P: n/a
(this can include stars, right?) well, as we know, our Sun is the largest Star, therefore, the planets would orbit around it, causing the circular motion.
Yes! (i love this subject) Globular clusters, as they are called, specify a group of binary stars that do more than just orbiting. When they orbit each other, they get caught up in the gravitational pull of nearby stars (and it should be noted the stars are very ((relatively speaking)) close to each other) and the star that is pulled into another binary system collides with one of the stars in the binary system. [sigh] Its very complex.
Binary systems are two stars that orbit each other. One small star orbits another big star (like the Alpha Centauri system).
As chroot said, our sun is really not the largest star. In fact, its at a stage where its really young, and therefore small. The biggest a star can get is, at the age of 20 million, the super red giant. When our good ol' star gets to that age, then it'll get so big, that it'll wipe out the inner planets (mercury to mars). So, in conclusion, our star is fortunately small.
chroot
#6
May6-03, 12:17 AM
Emeritus
Sci Advisor
PF Gold
chroot's Avatar
P: 10,429
No offense MV, but do us a favor: if you don't know something, please either 1) do not post it or 2) preface it with something like "I'm not sure, but I think..."
Originally posted by MajinVegeta
Yes! (i love this subject) Globular clusters, as they are called, specify a group of binary stars that do more than just orbiting.
I don't know what you're talking about -- perhaps you're discussing contact binaries -- but it's not globulars.
Binary systems are two stars that orbit each other. One small star orbits another big star (like the Alpha Centauri system).
No. Both stars, no matter what size, orbit their common center of mass.
As chroot said, our sun is really not the largest star. In fact, its at a stage where its really young, and therefore small.
Our Sun is not "young." It's about 50% of the way through its life, about 4.6 billion years old. Stars are not necessarily smaller when younger either.
The biggest a star can get is, at the age of 20 million, the super red giant.
Stars reach the red supergiant phase at different times, depending upon their mass. Unless you're talking a star with at least 100 times the mass of the sun, it won't be a red supergiant in tens of millions of years.

- Warren
enigma
#7
May6-03, 02:07 AM
Emeritus
Sci Advisor
PF Gold
enigma's Avatar
P: 1,817
Hey, I wrote an article on the "Zero-G" misconception on physicspost.com a few months back. Take a look:

http://www.physicspost.com/articles.php?articleId=104
kyle_soule
#8
May6-03, 10:01 AM
kyle_soule's Avatar
P: 293
Originally posted by chroot
As has been explained, there certainly is gravity in space.

The Coriolis force is essentially just a result of winds (or water currents) moving over a planet that is spinning beneath it. It makes freely moving objects make curved paths with respect to the surface of the earth. It isn't really a force at all -- it's akin to other ficticious forces: you can choose a coordinate system in a way to remove the Coriolis force.

The galaxy isn't moving in a spiral; it has a spiral shape, and things on the periphery are orbiting the center of mass.

While I understand what you're attempting to say, the word 'magnetic' is not appropriate at all here. Gravity and electromagnetism are two completely unrelated phenomena (at least until we have a Theory of Everything <smirk>).

The Sun is absolutely not the largest star. In fact, the Sun a puny, average, unimportant star -- except to us humans. What you're grappling at is the concept of 'superposition.' In other words, say you have one mass by itself. You can calculute the force vector experienced by a test mass at any point you like. You can thus describe a 'gravitational field' by expressing what the force vector is at all points in space. You can then add a second, identical mass to the system. The second mass's gravitational influence is simply stacked on top of the first ones -- the two fields can be simply added. The resulting field is just the simple sum of the two fields created by each mass -- the resulting field is the superposition of the two independent fields.

Einstein's theory of general relativity explains gravitation as an effect of curved spacetime. In essence, mass curves space -- and space then tells mass how to move.

- Warren
I don't believe he wanted his post torn apart and corrected on unneccesary points, such as magnetism NOT being gravity, he wasn't speaking of it as a force, but simply as an attraction.

Anyways, galaxies don't move in a circular orbit, as has been said, but towards other objects, such as galaxy clusters or any other galaxy larger than itself.

Planet's rotate around other stars, and the sun is the largest star in our system, I think this is what you meant, because the ripple they cause in space is sufficient to hold the planet's in it.

No offense MV, but do us a favor: if you don't know something, please either 1) do not post it or 2) preface it with something like "I'm not sure, but I think..."
How could this be taken any way BUT offensive. And he DID know what he was talking about. NP was just referencing our system of planets, and very often planets are in globular clusters.
chroot
#9
May6-03, 12:52 PM
Emeritus
Sci Advisor
PF Gold
chroot's Avatar
P: 10,429
Originally posted by kyle_soule
I don't believe he wanted his post torn apart and corrected on unneccesary points, such as magnetism NOT being gravity, he wasn't speaking of it as a force, but simply as an attraction.
Science is rigorous -- it's important to correct any misunderstandings (or perhaps just poor wording) immediately.
Anyways, galaxies don't move in a circular orbit, as has been said, but towards other objects, such as galaxy clusters or any other galaxy larger than itself.
In most cases, galaxies orbit the center of mass of the local group. They don't necessarily move "towards" anything, but follow standard Keplerian orbits about the center of mass like any other body.
How could this be taken any way BUT offensive. And he DID know what he was talking about. NP was just referencing our system of planets, and very often planets are in globular clusters.
Actually, a globular cluster would be the worst possible place to look for planets.

- Warren
New-Prototype
#10
May8-03, 01:58 PM
P: n/a
Thanks for answering my questions!! I really appreciate it, but uhh.... I sort of have trouble understanding some of the terms u use so if it's not too much trouble can u define them too? ^_^

I'm sort of confused too, because i don't see why our Sun isn't the largest star. But I must disagree with u on one point MV. hehe, sorry but our Sun isn't a young star because it if was it's color would be bright blue or white. As stars age their colors tend to change into a deep red, that's how u'll know that it's a oollddd star, right?

^_^ and kyle_soule is right. I was just wondering bout the positions and movement of our planets and why they do, but since i'm not even in highschool yet my intentions might be a bit vague. hehe sorry.

o!! i just got another thought!!! Aren't there black holes in our universe? What happens to the matter than gets absorbed by them? Does this create a time flux within our universe ~because there's no time in space~? So do u guys think that they're the reason why time bends?

rarr! the more answers i get the more questions i come up with, haha. But now that i can finally get answers and opinions from people I can't help asking! after all..i'm only 11 years old
New-Prototype
#11
May8-03, 02:01 PM
P: n/a
I'm a girl not a boy!!! rarr! hehehe, and it's ok kyle_soule because when Warren tells me what's wrong with my thoughts or theories I learn more. That's why I'm on here to share them, hehe
russ_watters
#12
May8-03, 05:24 PM
Mentor
P: 22,243
Originally posted by New-Prototype
[BI'm sort of confused too, because i don't see why our Sun isn't the largest star. But I must disagree with u on one point MV. hehe, sorry but our Sun isn't a young star because it if was it's color would be bright blue or white. As stars age their colors tend to change into a deep red, that's how u'll know that it's a oollddd star, right? [/B]
The sun is a relatively small star. Thats just the way it is. "Why" really isn't a relevant question. Also, age isn't the only thing that affects color - mass affects color. And since our sun is relatively small, it doesn't burn as hot, and therefore doesn't glow blue. Our sun is estimated to be halfway through its 10 billion year life.
chroot
#13
May8-03, 05:27 PM
Emeritus
Sci Advisor
PF Gold
chroot's Avatar
P: 10,429
Originally posted by New-Prototype
I'm sort of confused too, because i don't see why our Sun isn't the largest star.
Our Sun only looks so big because we're so close to it. We're only 93 million miles from it -- but the next closest star is almost 24 trillion miles away!
But I must disagree with u on one point MV. hehe, sorry but our Sun isn't a young star because it if was it's color would be bright blue or white. As stars age their colors tend to change into a deep red, that's how u'll know that it's a oollddd star, right?
This is, in very general terms, correct. Stars expand and cool as they reach the end of their main sequence lives. As a result, old stars are usually large and red. However, this doesn't mean that all young stars are small and white!

It all depends on the mass of the star, as a matter of fact. Very massive stars are very hot and thus white or blue in color. These stars also burn out very quickly -- so if you see a blue-white star, you know it can't be very old. On the other hand, a low-mass star might appear red or orange even when it's young.

So to recap: 1) All old stars are red, but not all red stars are old. 2) All blue-white stars are young, but not all young stars are blue-white.
o!! i just got another thought!!! Aren't there black holes in our universe? What happens to the matter than gets absorbed by them? Does this create a time flux within our universe ~because there's no time in space~? So do u guys think that they're the reason why time bends?
When a black hole absorbs some matter, it just gets a little larger -- there's nothing spooky going on with time or gravity or anything. There are, however, some spooky things that happen to the information content of the matter that fell in. For example, if you throw a Shakespeare play into a fire, the information is not really lost -- it's just spread out into the ashes and smoke. You could in principle look at all the atoms of ash and smoke and see what the book said -- though it would, of course, be very difficult. On the other hand, if you throw the Shakespeare play into a black hole, the information in the book is irretreivably lost forever, even in principle. It would take a lot more talking to really help you understand the consequences of this, though. Don't worry though, nothing funny happens to time when something falls in a black hole.

- Warren
schwarzchildradius
#14
May10-03, 05:11 AM
schwarzchildradius's Avatar
P: 179
"The Coriolis force is essentially just a result of winds (or water currents) moving over a planet that is spinning beneath it. "

It's not, it is an inherent effect of 3-d circular motion. It shows up in a transformation from rectangular to polar coordinates.
meteor
#15
May10-03, 06:22 AM
P: 915
So to recap: 1) All old stars are red, but not all red stars are old. 2) All blue-white stars are young, but not all young stars are blue-white.
This is not necessarily true. A white dwarf can be really old, and how its name indicates, is white (in fact the Sun will be a white dwarf in 5 billion years, after reaching the stage of red giant)
If you consider a black dwarf like a star, is an exception too
chroot
#16
May10-03, 10:53 AM
Emeritus
Sci Advisor
PF Gold
chroot's Avatar
P: 10,429
Originally posted by meteor
This is not necessarily true. A white dwarf can be really old, and how its name indicates, is white (in fact the Sun will be a white dwarf in 5 billion years, after reaching the stage of red giant)
If you consider a black dwarf like a star, is an exception too
That's certainly true, and thank you for pointing it out. I was talking about (though I did not specify) only about active stars still burning fuel.

- Warren
New-Prototype
#17
May10-03, 05:40 PM
P: n/a
This is not necessarily true. A white dwarf can be really old, and how its name indicates, is white (in fact the Sun will be a white dwarf in 5 billion years, after reaching the stage of red giant)
Does this mean that very old stars are white? Then why are old stars red? And how can our Sun when it reaches the stage of a RED giant be a WHITE dwarf? rarrr astronomy is confusing, but I still like it ^_^

It's not, it is an inherent effect of 3-d circular motion. It shows up in a transformation from rectangular to polar coordinates.
uhhh....this sounds weird but..what did everything he said up there mean? it sounds complicated though. hehe, either than that i have no clue of what he meant when he said "It shows up in a transformation from rectangular to polar coordinates", someone explain it to me. please??
chroot
#18
May10-03, 06:06 PM
Emeritus
Sci Advisor
PF Gold
chroot's Avatar
P: 10,429
Stars generally go through the following phases:

Protostar: radiates mostly in the infrared; fusion has not begun

Main sequence: adult life for a star -- massive stars are hotter and blue-white; less massive stars are cooler and redder

Red giant: reaching the end of the useful hydrogen fuel -- these stars are larger and cooler and redder than when on the main sequence

At this point, the evolution of small mass and large mass stars differ.

End of life for small stars: white dwarf: the core of the dead star, no longer producing any energy. The rest of the star's mass is thrown off into a planetary nebula, leaving the hot white core in the center.

End of life for moderate mass stars: neutron star: a very dense state of matter. These stars are associated with pulsars.

End of life for very massive stars: black holes.

- Warren


Register to reply

Related Discussions
Weird typing thing Computing & Technology 1
Gravity Question... kind of General Physics 24
Kind of Weird Orbital Problem Introductory Physics Homework 1
A different kind of gravity car General Physics 0
Weird thing with water General Physics 2