An object moves along a straight line in curved space

This made me laugh really friggin hard

>let's explain gravity by making a drawing that uses gravity
idiots

Yeah, because like it makes sense for an object to move down a slope, and this picture helps me understand more about how an object will move, but it doesn't explain why it moves. Like I don't understand what's "pushing" or "pulling" the object, I only know what to expect and how to apply it. Any help on this? When I drop a ball, what is the explanation for what is acting on it?

Well there are different theories. In GR you are constantly moving though gravity, and the curvature simply modifies the geodesic (your path). There is no force carrying particle because it's not part of the standard model, but some more speculative theories predict something called a graviton.

Spacetime is 4D, 3D+t. Spacetime is curved because of gravity. The worldline of an object in spacetime has its shape determined by the curvature. When you project the object's worldline into 3D space you get its trajectory.
Nothing is really pushing or pulling, you're just seeing snapshots of the worldline at certain times.

learn riemannian geometry

Thanks, first two actually make a lot of sense, appreciate it. I'll take a look into riemannian geometry, but it depends. How much time do you think I'll have to dedicate before I get what I want?

1/4

2/4

3/4

4/4

Stupid question but when people say there are more than four dimensions what actually are the other dimensions? it's not extra directions like depth,height, width is it? I'm visualizing as our 3d universe is like a cube inside an exterior room that has direcetions not apart of our universe.

Consider the Earth as a curved space for this example:
If you move along the equator on Earth, you are moving in a straight line,in a curved space.
Similarly a satellite is moving in a straight line in the curved space that surrounds a massive celestial body.

>projecting what you do understand onto something you don't understand in order to make sense of it.

A straight line is a imaginary concept like time.
It doesn't exist.
Everything is a curve. perfect circles don't exist either.
Everything in the universe and nature is elliptical.
>>The Earth travels around the sun in an ellipse. If the Earth were to orbit the sun in a circle, the Earth's speed around the sun would be constant. We can think of this as the Earth's average speed. However, because the Earth's orbit is elliptical, the speed of the Earth varies throughout the year.

Think of it like your sexuality. The straight line is your deluded belief that you are heterosexual when in reality that is a trick of relativity. The rest of Veeky Forums, the world even, can see how much of a fag you truly are.

fuck off, gnostic-user

1,maybe 2 centuries if you're lucky

In m theory they predict 10 or 11 dimensions, however they're so miniscule we don't even know they exist

But what are those extra dimensions? I know the 4th is supposed to be time. What is the 5th, 6th etc? Are they spatial directions? Im having trouble imagining something other than height,width and depth.

Honest question from interested brainlet...
I don't understand how LIGO works. They bounce laser beams off mirrors and detect a gravitational wave "ripple" from the small difference in time for the beam to travel each of the two "L" shaped detectors.
So those laser beams travel the shortest paths for both "arms".

Does the gravitational wave "ripple" make the distance traveled longer for one beam vs. the other and therefore take slightly longer?
Is that what they are measuring?

In GR the forces of the ground are in constant resistance to the flow of space time, so you experience gravity because you are in a constant state of acceleration. Objects don't accelerate down, the ground accelerates up against spacetime to meet the object. The falling objects are the ones at rest.

It's not until you care about things that move without contact with the ground for a while. Think about it like this. You're an artillery gunner. You've been tasked with dropping a shell on a snackbar 5 miles away. Snackbar is on the earth and the earth is moving. When the shell gets there the earth will have moved and the snackbar with it.

tl;dr Coriolis is a snackbar sympathizer working behind the scenes to move them out of the way of incoming fire. Luckily he's predictable.

Depends on who you ask.

4th dimension could be time, or it could be 4th spatial dimension. You cannot really properly imagine 4th spatial dimension, since we live in 3D world, but you can see the shadow of a 4D object as it travels through our 3D world (google tesseract), just like you can see a shadow of a 3D cube on a 2D screen or piece of paper. The difference is, 3D is very intuitive to us, and your brain fills in the gaps, so you can see the hexagon drawn on the paper with some dotted edges etc as a transparent cube as seen from a certain perspective. While tesseract will probably make your brain hurt as it does everybody else's. In math you can have n spatial dimensions, and the math works out, but nobody tries to actually imagine n-dimensional objects.

Spacetime is something different and you should google both.

According to the Einstein field equations, matter curves space-TIME (don't forget it's space AND time) via the stress–energy–momentum tensor, and space-time tells matter how to move by taking the shortest path in a now curved 4d manifold via the metric-tensor.

There is literally nothing hard to understand once you have internalized the fact that time, apart from being a unidirectional dimension and thus having an opposite sign to the other three, is just like other dimensions. You exist in 4d.

Of course there are non trivial implications you can derive from this, like special relativity, frame dragging, black holes and light cones, and CTCs which may not even have physical meaning.

Thanks, so time is just a coordinate in the 4th dimension?

For example if you want to meet someone you need the position in the world but you also need to be there at the correct time.

Also,why do we travel automatically through time (4th dimension) at a fixed pace.

>Also,why do we travel automatically through time (4th dimension) at a fixed pace.
Or do we? Google it mate. I don't know enough about spacetime to teach anybody. But luckily for you, the concept is interesting enough that are thousands of websites and even videos on youtube explaining it.

Ever tried to find more than 5 BJT circuit analysis problems online so you can practice? Now that's a toughie.

An object in 4D spacetime is the entire world line of the object. Perception of traveling through time requires a consciousness. The order of events is dictated by causality, but the rate is an illusion of our consciousness. It technically all exists at once. Spacetime includes both the when are where of all objects, so all positions through past and future exist geometrically.

So for example the year 2050 is the future for us but that year must have a present and that exists right now too. Like we in 2017 are living in the 90s future? What makes our conscious being in 2017 right now?

I have no idea what I'm talking about though and I'm starting to confuse even myself.

You can't even measure the passage of time, you measure the increase in entropy in your surroundings. You could, for example, have extra time dimensions and on a macroscopic be none the wiser

Not really... Now and 2050 are separated by events. We experience those events at the rate our brains decide time should move. But all the events are laid out in the geometry of spacetime.

>We experience those events at the rate our brains decide time should move.

But is there an objective rate these events happen at or we would get desynced if everyone had their subjective experience.
When you say all the events are laid out do you mean that they are pre-determined? English is not my first language.

Yes, essentially pre-determined. More than that, it already exists on our world line.

The rate is dictated by biology. Our brains experience time at a rate that would allow us to react to stimuli. It's essentially the same for everyone since our biology is so similar, and so similar to animal brains too. But it can change slightly, depending on how focused you are or how much drugs you're on.

>Does the gravitational wave "ripple" make the distance traveled longer for one beam vs. the other and therefore take slightly longer?
yes
>Is that what they are measuring?
kind of: the laser beams are in perfect phase so should one of the arms become shorter you'd notice an interference, not a full half a wavelenght obscuring interference really but a tiny dimmer light perceived by the sensor.

>The rate is dictated by biology.

Does that mean it would in theory be possible to build some type of time machine by just connection our brain to it and speed up our perception of time?

You could go to sleep and make 8 hours fly by.

They are largely regarded as unknowns
M theory is an evolution of string theory

Using m theory it's actually possible for speeds greater than c

space.com/5725-spaceship-fly-faster-light.html

It's a infinitessimal line element you brainlet.