If you can move freely in space with no resistance, how can mass enable space to change Earths traje

sityeuropa

sityeuropa

sityeuropa

Associate
Joined
3 Oct 2014
Posts
1,780
What puzzles me so much is how a huge object like Earth can be pulled from its straight line trajectory into an orbit by the bending of space from a huge mass (sun).

Too easily understand it we think of space like a fabric that bends in order to allow objects to follow gravities forces.

It's so hard to picture space being strong enough to pull the Earth in.

Does anyone understand what I'm getting at, I probably have not explained it as best as I wanted.

The fabric example, although this doesn't show the forces in every direction.
 
Last edited:
I don't understand what you're asking. What do you mean by "forced to change direction"?

Are you by chance referring to a 'mavity slingshot'?
 
The Earth is in theory travelling always in a straight line.

mavity is what is bending space so that the straight line actually becomes an orbit around the sun.

I find it amazing that space what we think of as empty with no friction or resistances as something that can be bent.

Like an invisible train track.
 
Last edited:
I think you're thinking of this in completely the wrong way.

The mass is what provides the 'force' and space because it has no resistance or friction, does nothing to oppose this force.

This is just a 2 dimensional representation of how gravitational forces work. I'll grant you that visualising the bending of space is not intuitive, but I don't see why it being empty with no friction or resistance makes it any harder to perceive.
 
sityeuropa said:
What puzzles me so much is how a huge object like Earth can be pulled from its straight line trajectory into an orbit by the bending of space from a huge mass (sun).

Too easily understand it we think of space like a fabric that bends in order to allow objects to follow gravities forces.

It's so hard to picture space being strong enough to pull the Earth in.

Does anyone understand what I'm getting at, I probably have not explained it as best as I wanted.

The fabric example, although this doesn't show the forces in every direction.
Click to expand...


Likewise its hard to believe the moon causes tides.
 
Question from a none sciency person but who has a passion for it none the less. Given the way the ISS and other man made satellites orbit the earth being that they are basically always falling towards earth but due to their speed they are always falling " of the edge " thus continually orbit. Can it be similarly explained as planets behaving in this way or are the orbital mechanics different for celestial bodies?

Im a simpleton so please be easy on me :D
 
IMG_4292.jpg
 
harry5522 said:
Question from a none sciency person but who has a passion for it none the less. Given the way the ISS and other man made satellites orbit the earth being that they are basically always falling towards earth but due to their speed they are always falling " of the edge " thus continually orbit. Can it be similarly explained as planets behaving in this way or are the orbital mechanics different for celestial bodies?

Im a simpleton so please be easy on me :D
Click to expand...

The principle is the same. A planet might have originated around a star or it might have been captured as it wandered too close, but in either case it is always travelling and always missing the star because it's just going too darn fast.

But to expand your understanding a little further, learn that it's not actually falling towards the star, it's falling to the common centre of mavity. What is the common centre of mavity? Well it's the point between the planet and the star where their combined gravities balance. After all, a planet is pretty big itself so it has significant mavity too. So when you see a planet going round a star, imagine a point between the two, a point much closer to the star because the star is so much bigger, but still not at the centre of the star. This point, this gravitational middle, is the real centre of the orbit.

So when you orbit a star, that star - just a little bit - also orbits you. :)
 
More mass = stronger gravitational pull.

The Sun is big. Like really, really, really big. So it has really, really, really big gravitational force.
 
It's not just the Sun that keeps our planet going on its set orbit. All the other planets play roles of varying scale. If Jupiter didn't exist, we wouldn't exist, for example. If the other planets were a different distance apart from each other, then our orbit would be different, perhaps bordering on an extreme to support human life as we know it.

Our solar system is quite unique in that way. All the conditions are just right for life as we know it to exist.
 
If you want to make it a bit more twisty in your head, consider that the sun orbits around the center of the Milky Way Galaxy, and that the planets moving around the sun is actually a vortex.

 
I think you are looking at it the wrong way. Space itself isn't actually pulling on anything. All you are seeing is the effects of mass on spacetime.

Imagine a marble rolling down a plank of wood. The marble is rolling but the wood isn't pulling on it. We say that mavity "pulls" because its that is what it feels like and its the easiest way to visualize it but thats not really what is happening. All of the plants are just marbles rolling on a plank of wood and the woods incline is determined by the mass of the objects themselves.
 
Rifte said:
https://s16.postimg.org/66ggnmkvp/IMG_4292.jpg[/
[/QUOTE]

[QUOTE]But 8 km/s is blisteringly fast. When you look at the sky near sunset, you can sometimes see the ISS go past ... and then, 90 minutes later, see it go past again.[6] In those 90 minutes, it's circled the entire world.[/QUOTE]


:eek: Cant say Ive ever seen the ISS. Anyone seen it twice at sunset



18,000 mph pretty fast then
Click to expand...
 
sityeuropa said:
SNIP
Click to expand...

It's one of the most simple and easy to understand concepts of them all :confused:

Mass bends space time, otherwise an object will keep travelling in a straight line .......... until it encounters a gravitational field that bends the space/time in the way your video shows.

I guess your thinking of the object being directly affected as opposed to it and all the 3d space and time it occupies.
 
harry5522 said:
Question from a none sciency person but who has a passion for it none the less. Given the way the ISS and other man made satellites orbit the earth being that they are basically always falling towards earth but due to their speed they are always falling " of the edge " thus continually orbit. Can it be similarly explained as planets behaving in this way or are the orbital mechanics different for celestial bodies?

Im a simpleton so please be easy on me :D
Click to expand...

The ISS experiences and hits minor amounts of debris/dust/rocks in it's orbit, which slows it down to the point that mavity begins to pull it down. The ISS then needs to "boost" back up to a suitable orbital velocity. to stop falling. It's a bit different to the way planets behave :p
 
Yup, re-boosting also has a pretty cool effect for crew on-board. They need to do it once a month.

 
You must log in or register to reply here.
Back
Top Bottom