• Ask your space questions of a real life astrophysicist with our latest AMA by clicking here!

I know very little of space, but I am in awe of it and love it. Why does earth have gravity?

May 31, 2020
8
8
15
Hello,

This forum is an absolutely great place to learn about space, physics, mathematics, etc., etc I should start here because my questions are way too simple for the main forum were the super smart adults hang out.

I heard planet is like a rocket shooting threw space in one direction at the same speed (or rather faster and faster because the universe is expanding exponentially?) it’s doing this because the universe is expanding.
Now earth has a curve on the bottom of it, Einstein calls this gravity. So earth is traveling threw space with the sun and planets following us and going around earth, or rather earth is following the sun? I don’t know this is hard stuff for me, sorry. And the sun and the planets are all going elliptical around earth as we are shooting threw space?

Now my big question is if earth has gravity which way does it have gravity? Since space has no up or down how can earth have gravity on a space time grid, like if I put a ball on a trampoline and put it in the center you would see this fold underneath the ball. That’s fine for the trampoline , but space is not a trampoline ( or is it like a trampoline in a sense? ) and has no up or down or left or right, etc. etc. so what causes earth to have that gravity underneath the earth. If earth has gravity then is the earth falling? Or Is it turtles all the way down?

Thanks so much fellow beings in awe of space and are in love with it. Especially how big it is. Blows the mind, doesn’t it? I love that.
 
Last edited:

Wolfshadw

Moderator
Apr 1, 2020
79
49
60
The center of gravity for the Earth is the planet's core. No matter where you stand on the planet, the North Pole, South Pole, the Equator, gravity is pulling you towards the planet's core.

As for traveling through space, all of the planets on our solar system orbit around our star, the Sun. The solar system, as a whole is in orbit around the center of the galaxy, the Milky Way. The Milky Way is traveling through space. So the Earth travels around the Sun, which is traveling around the center of the galaxy, which is traveling through space.

-Wolf sends
 
May 31, 2020
8
8
15
Thanks Wolfshadw and rod.

I’m still a bit confused on another matter, sorry fellas, bare with me, lol. Total noob here, but I love to learn so I’m here.

Anyway if you take a look at that picture of the earth and the sun in that link you gave me “rod”,do you see the gravity of the earth and the sun...well I’m having a hard time wrapping my head around the idea of that . Both the earth and sun are bending the fabric of spacetime. However, like I said spacetime has no up or down or left or right, it’s just space in all directions, what I would like to know is why there is that curvature , or bending, under the sun and the earth? Is it sitting on some kind of membrane? And to us looking at that picture the membrane is horizontal and the earth and the sun cause a curve/bend in spacetime, but I don’t understand why the curve can’t be vertical or literally any direction since there is no direction in space. I suppose that diagram is supposed to give humans a simple picture of how the earth and sun cause a curve in spacetime, but like I said it doesn’t make sense to me. Because you can turn that picture upside down and then the curve would be above the earth. In the picture it’s below the earth, I just don’t understand it. Shouldn’t there be curves all around the earth if spacetime has no up or down , no left or right. I’m trying to read the article you gave me and it still doesn’t make sense. Maybe if I read it again and think on it it will come to me. It’s not difficult , I’m just a bit tired. But maybe you can give me an easy answer? Or maybe it’s just that I’m not explaining myself well. That’s my fault then. If you don’t understand what I mean just say so and I will try to clarify it for you better.

Maybe there is no way to put it into words. Is that why we have mathematics? To describe phenomenon that can’t be told in words? If that really is the case then I would need Einstein’s mathematical notation of why we have that curve/bending in spacetime with that picture of sun and the earth in that article you provided. It seems to be sitting on a membrane, but what is pulling the sun and the earth downward? Gravity right? Ok, like I said there is no up or down or left or right in space, so take that picture turn it upside down and you still have the earth and the sun and the membrane ( or whatever it’s called ) but now the bending / curving is on top of the sun and the earth instead of before where it was underneath the earth and sun.

Thanks for replying back. I have many questions about space but this is the first one I don’t understand.
 
Last edited:
  • Like
Reactions: ahmet cinar

Wolfshadw

Moderator
Apr 1, 2020
79
49
60
That "curve" isn't the location of the gravity well. It's just a 3D representation of the strength of gravity around a given body, The deeper the curve, the stronger the gravity of that body.

-Wolf sends
 
  • Like
Reactions: UBIK and COLGeek
May 31, 2020
8
8
15
Interesting. Now taking what you just said into account we can say that earth has a gravity well and the curve is just a 3D representation. Ok, but what I fail to grasp, hard to put into words sorry, is why earth falls into a gravity well at all, what I called a curve, are you saying that there is a gravity well all around the planet? Or is the gravity well on just one side of earth? Well no right because the picture shows us it goes downward, but how can that be if there is no down in space, where is earth falling into, besides the black hole at the center of our galaxy I mean. Einstein said that celestial bodies have curves or gravity wells. I want to know how can this be , how can there be gravity in space when there is no up or down or left or right in space. I guess what I’m really getting at is, in effect , how can there be gravity in space, let’s use earth as our example here ? We could say, oh the earth is falling downward that’s why it has gravity? But falling towards what? A cement road at the bottom of the universe. Now you just introduced me to the term ‘gravity well’, so earth is kind of like falling into that gravity well right? So what your saying is the 3D representation is just to orient our brains because we think in terms of horizontal and vertical. When we walk we are walking horizontally, so that’s how we orient ourselves on earth. In space we would have to find a way to orient ourselves too. But are you saying that that 3D graph could be upside down in real space? Or turn it to the left and that’s how it really is? Basically how is there gravity for the earth? We are pushed to the earth because of gravity. But what pushes the earth and gives it gravity?
Orientation is a big factor here.
 

Wolfshadw

Moderator
Apr 1, 2020
79
49
60
All objects in space have gravity. The curves that you see in those images are simply a representation of the strength of the object's gravity. It IN NO WAY, represents direction.

All objects have gravity. The center of gravity for Earth is the core of the Earth. All objects in, on and around the Earth are being pulled towards the core of the Earth. As I said earlier, not matter where you stand on Earth, the North Pole, the South Pole, the Equator, you're being pulled towards the center of the Earth. The same thing goes for the Sun. Everything in, on, and around the Sun is being pulled towards the core of the Sun.

-Wolf sends
 
  • Like
Reactions: UBIK
Dec 11, 2019
487
160
360
Thanks for helping me with this, I understand now.
What causes Gravity?
One of Einstein's old tutors, a man by the name of Minkowski showed that the special theory of relativity could be expressed in an interesting way.

The world we live in consists of four dimensions, the three space dimensions and one that is not exactly time but is related to time (it is in fact time multiplied by the square root of -1). This is not at all easy to understand but it means that space-time as we call it has some rather weird properties. In particular, when you move through one of the space dimensions you also travel, unwittingly, through time. You do not notice this, indeed as far as you are concerned nothing happens to you at all, but someone observing you would say that you have travelled through time. Of course, we are always travelling through time, but when you travel through space you travel through time by less that you expect. The most famous example of this effect is the "Twins Paradox".

All the effects of special relativity, such as the slowing down of clocks and the shrinking of rods follow from the above. In fact, it is often better to think of some things, such as electromagnetic fields as being four-dimensional objects. But the important thing to remember for the moment, is: when you move through space you are compelled to move through time but, when you move through time (which of course you are always doing) you do not have to move through space.

So, what does this have to do with gravity? It is quite simple! When a mass is present in the above space-time it distorts it so that whilst it remains true that travelling through space causes you to travel through time, travelling through time now causes you to move (accelerate) through space. In other words just by existing, you are compelled to move through space - this is gravity.

The particular advantage of this theory of gravity (General Relativity) is that it explains, at a stroke, all the observed properties of gravity. For example the fact that it acts equally on all objects and substances becomes obvious when you thing of gravity as a distortion of space-time rather than a force.

Imagine that you are in free space, away from any planets or stars, when suddenly a planet is created quite close to you. You would not be aware that anything is happening to you, you would feel no force, but you would find that you started to accelerate towards the planet. This is just like the case where you travel through space, you are not aware that you have also travelled through time but people observing you are.

Can you feel gravity?
You can argue that we do not. What happens is that, as you pass through time, the distortion of space-time caused by the presence of the earth accelerates your body towards the centre of the earth. But when your feet are touching the ground, the ground exerts a force on your feet in an upwards direction which pushes you in the opposite direction. In other words you are being accelerated upwards with respect to space-time by the force of the ground acting on your feet. It is exactly the same as the force which seems to push you back in your car seat when you accelerate, what is really happening is that the seat is pushing you forwards.
 
  • Like
Reactions: UBIK
May 31, 2020
8
8
15
Lastly, I just wanted to thank everyone else for helping me get a better grasp on gravity and “gravity wells”which is a new term for me. I just bought Einstein’s ‘Special and General Relativity’ book. It’s probably free but I wanted a hardcover copy of this bad boy. I started reading it and so far it’s not as hard to read as I thought it would be, however getting my head around the ideas , theoretical physics, and understanding the mathematical notations he used is a real problem. I don’t know what kind of math he used, well he wrote in the book that he uses geometry but I think he uses other types of maths too, is it non-linear algebra or some super hard math like that?lol. But seriously the math I do see seems difficult , what kind of math is it? That’s my last question for this thread, and once again thank you everyone for educating me.

I will make another thread later on some day if I ever need help with reading Einstein’s Special and General Theory of relativity. The only reason I’m reading this book first is because I want to get into string theory, loop quantum gravity, the Heisenberg Uncertainty Principle, etc. , etc. and I’m pretty sure you need to know Einstein before all that really heavy stuff, not to say Einstein isn’t heavy , he is really heavy. But compared to today’s ideas of the universe Einstein was wrong on a few things ( e.g. God does play dice.)
 
Last edited:
  • Like
Reactions: Truthseeker007
Dec 11, 2019
487
160
360
Lastly, I just wanted to thank everyone else for helping me get a better grasp on gravity and “gravity wells”which is a new term for me. I just bought Einstein’s ‘Special and General Relativity’ book. It’s probably free but I wanted a hardcover copy of this bad boy. I started reading it and so far it’s not as hard to read as I thought it would be, however getting my head around the ideas , theoretical physics, and understanding the mathematical notations he used is a real problem. I don’t know what kind of math he used, well he wrote in the book that he uses geometry but I think he uses other types of maths too, is it non-linear algebra or some super hard math like that?lol. But seriously the math I do see seems difficult , what kind of math is it? That’s my last question for this thread, and once again thank you everyone for educating me.

I will make another thread later on some day if I ever need help with reading Einstein’s Special and General Theory of relativity. The only reason I’m reading this book first is because I want to get into string theory, loop quantum gravity, the Heisenberg Uncertainty Principle, etc. , etc. and I’m pretty sure you need to know Einstein before all that really heavy stuff, not to say Einstein isn’t heavy , he is really heavy. But compared to today’s ideas of the universe Einstein was wrong on a few things ( e.g. God does play dice.)
One good thing to know is much science likes to make things complicated that are quite simple. It almost seems like they talk in a different language if you try to read some of the information. I guess they want to make themselves look smarter then they really are by making it complicated for no reason.

It's kind of like a guitar teacher making the guitar look harder to learn then it really is so they can suck more money out of you and cause you to have to take years to learn. Your better of just teaching yourself instead of listening to the pundits and "teachers" that what to suck time and money out of you.
 
  • Like
Reactions: UBIK
May 31, 2020
8
8
15
Lol, yeah it does seem that way. Like they are just trying to impress their friends and colleagues into thinking they are smarter then they really are, and they go around with their diplomas saying “ Look at me I know everything, seriously everything , even things outside of my chosen field .” Heh, don’t think so.

I like it when Einstein said : "Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution." And I like that quote “Everything should be made as simple as possible, but not simpler", which I think means what you are talking about, at least in part.

Do you really think if I study hard on my own I can understand physics and harder maths? Sounds reasonable, but the prevailing attitude today is that you “need” a teacher or tutor to help you to learn these very difficult subjects, especially string theory and quantum mechanics, however there are many , many books out there to help me learn those subjects. I was thinking of going to a math forum or physics forum , but if you think going it alone would be a better idea I think I just will. I will stick to the hard studying myself. Thanks🙂

Oh, and I didn’t mean I was going to be bothering this forum everyday on what each page means, ha, no way. But I think I will take what you said to heart and post about other subjects instead. I think I’m ready to join the major forum now. I just posted here because it was for children and I’m pretty childish in these areas, but I read some of the posts in the main forum and it’s not that difficult. So I just graduated from Grade 1 to Grade adult in one thread, lol. Or maybe I should stay here in the children’s section...no your right I think I can understand what other posters are saying in other threads in the main forums if I study on it a bit, eh? Yeah, I think you may be right.

Peace guys/ladies
 
Last edited:
  • Like
Reactions: Truthseeker007
Dec 11, 2019
487
160
360
Lol, yeah it does seem that way. Like they are just trying to impress their friends and colleagues into thinking they are smarter then they really are, and they go around with their diplomas saying “ Look at me I know everything, seriously everything , even things outside of my chosen field .” Heh, don’t think so.

I like it when Einstein said : "Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution." And I like that quote “Everything should be made as simple as possible, but not simpler", which I think means what you are talking about, at least in part.

Do you really think if I study hard on my own I can understand physics and harder maths? Sounds reasonable, but the prevailing attitude today is that you “need” a teacher or tutor to help you to learn these very difficult subjects, especially string theory and quantum mechanics, however there are many , many books out there to help me learn those subjects. I was thinking of going to a math forum or physics forum , but if you think going it alone would be a better idea I think I just will. I will stick to the hard studying myself. Thanks🙂

Oh, and I didn’t mean I was going to be bothering this forum everyday on what each page means, ha, no way. But I think I will take what you said to heart and post about other subjects instead. I think I’m ready to join the major forum now. I just posted here because it was for children and I’m pretty childish in these areas, but I read some of the posts in the main forum and it’s not that difficult. So I just graduated from Grade 1 to Grade adult in one thread, lol. Or maybe I should stay here in the children’s section...no your right I think I can understand what other posters are saying in other threads in the main forums if I study on it a bit, eh? Yeah, I think you may be right.

Peace guys/ladies
I would say you are off to a pretty good start already. My bad and I didn't even realize there was a childs section on here. :D But yes keep up the learning and like I said you seem smarter then most adults on here.:D

Einstein is a really great place to start. I think it all depends if you think you need a tutor or teacher or not I mean besides school we all have to get through that. But there are so many many books that you can read and even do your own experiments.

I think what has happened over time things are just being regurgitated and know one seems to stop and think for themselves. So as some say go where the Universe takes you but always remember to think for yourself also. Also know depending on what you want to learn a teacher can only take you so far. It is truly up to you. Getting the basics down is always the first step. Like the analogy of the guitar. You can't play a whole song until you learn all the intricate parts that make up the whole song. Once you can play a whole song then you can start to make your own songs. I hope you find what you want to find and learn what you want to learn and you are off to a great start.
 
  • Like
Reactions: UBIK
May 4, 2020
2
0
10
Hello,

This forum is an absolutely great place to learn about space, physics, mathematics, etc., etc I should start here because my questions are way too simple for the main forum were the super smart adults hang out.

I heard planet is like a rocket shooting threw space in one direction at the same speed (or rather faster and faster because the universe is expanding exponentially?) it’s doing this because the universe is expanding.
Now earth has a curve on the bottom of it, Einstein calls this gravity. So earth is traveling threw space with the sun and planets following us and going around earth, or rather earth is following the sun? I don’t know this is hard stuff for me, sorry. And the sun and the planets are all going elliptical around earth as we are shooting threw space?

Now my big question is if earth has gravity which way does it have gravity? Since space has no up or down how can earth have gravity on a space time grid, like if I put a ball on a trampoline and put it in the center you would see this fold underneath the ball. That’s fine for the trampoline , but space is not a trampoline ( or is it like a trampoline in a sense? ) and has no up or down or left or right, etc. etc. so what causes earth to have that gravity underneath the earth. If earth has gravity then is the earth falling? Or Is it turtles all the way down?

Thanks so much fellow beings in awe of space and are in love with it. Especially how big it is. Blows the mind, doesn’t it? I love that.
 

ASK THE COMMUNITY

TRENDING THREADS