If the weight of a star or planet curves space-time, what is

>>8739366
First of all, it's not the weight that bends spacetime, it's mass.

Weight is a scalar quantity whereas Mass is a vector. There is no direction in space so it's very important to use vector quantities for your variables. Objects in orbit do not have weight because they're always going to end up in the same position and the average weight is 0.

As to your other question, spacetime curvature has already been proven with physical experiments.

>>8739366
Apparently the poster of the first reply doesn't understand English, so let me try.

The maths modelling spacetime in general relativity just works like that. Spacetime isn't curving "into" anything. Your problem is that you're thinking that all properties of an anology used to explain something else must be identical with the properties of the phenomenon it's trying to explain. This defeats the purpose of having an analogy in the first place.

There was a video in which Feynman was asked to explain magnetism, and he said that he could not explain it by analogy because magnetism was both more fundamental and also unlike any other intuitive or everyday phenomenon. I think the same goes for spacetime curvature.

Semi-related: What does the surface of an apple curve into?

>>8739424
>Apparently the poster of the first reply doesn't understand English, so let me try.

He thinks mass and weight are the same.

>Semi-related: What does the surface of an apple curve into?

The box it came in.

>>8739366
>If the weight of a star or planet curves space-time, what is it curving into?
The correct word "mass", anyway, it isn't curving into anything, it's curving intrinsically. It is counter-intuitive, but that's just how it is. The only way to properly imagine this kind of geometry is by embedding the curved geometry into a higher dimensional manifold (e.g. that famous rubber sheet analogy), but that higher dimensional manifold does not exist.

>>8739424
So is the Big Bang and expansion of the universe also an analogy? It's been passed off as scientific fact claiming the universe is expanding but not expanding into anything.

>>8739383
>Weight is a scalar quantity whereas Mass is a vector
Wrong.
Weight is the name given to the force of gravity applied to one object by another, therefore is a vector.
>Objects in orbit do not have weight because they're always going to end up in the same position and the average weight is 0.
Also wrong, in orbit forces are considered radially and angular quantities are generally given as the normal vector to the plane they rotate on.
Luckily your first and last comments aren't completely retarded or I'd go for the hat trick

>>8739424
So if spacetime curvature is just an analogy, why does light bend its path? Maybe photos are not truely massless but too small to be measurable.

>>8739366
A manifold can exist on its own without being embedded into a higher dimensional manifold.
Curvature can be defined based on a manifold itself.

>>8739532
>Using fancy jargon to sound intelligent

>>8739536
Nope. I'm a master's student in math and it's standard differential geometry terminology.
You can't really talk about "the curvature of spacetime" without it.

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>>8739383
>weight isn't a vector
>mass is
lol good one

>>8739591
Then show me something with a negative weight, moron.

>>8739600
muh dick

>>8739600
everything on earth.

>>8739600
Literally a helium balloon you fucking idiot. Your post is a fucking joke, you have no clue what you are talking about.

>>8739600
Helium balon

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>>8739383

>>8739435
>He thinks mass and weight are the same.
Maybe he did or maybe it was a brain fart; it's irrelevant either way. You did not reply to the actual content or the questions in his post.

>>8739442
>>8739532
These guys explained it a little bit more in-depth, but it's still really superficial. The only way you'll get a better understanding of spacetime curvature is to study the maths behind it. Everything else will just be analogies.

>>8739525
>>8739461

I didn't say that spacetime curvature is an analogy, I said that we use an analogy to explain spacetime curvature (to people who haven't studied the math behind it), and that the analogy has some properties that spacetime curvature doesn't have and vice versa (there are many examples of this, the explicit one was that spacetime doesn't curve "into" anything, whereas everything a layman would be able to relate to curves "into" something [whatever that means, it doesn't really make much sense once you really think about what curving "into" means]).

>>8739616
Not the guy you replied to, but as I remember it, weight is defined as the force exerted upon a body due to gravity, regardless of other forces and thus also regardless of net forces, meaning that helium has a non-zero positive weight.

Obviously weight is a vector due to the gravitational force having a direction.

From wikipedia:

>Weight is a vector [...]

You can check the source for that claim in the wiki article if you have a problem with me referencing wikipedia.

>>8739600
If you define your positive direction as opposed to the weight force, then the weight is by definition negative yet the mass has not changed.

>>8739461
I would say that the Big Bang is an analogy.
A lot of people seem to assume that there was some form of universe in existence, and that all matter exploded from a singularity of some sort, whereas the actual theory is that the Big Bang happened everywhere all at once, and then the universe expanded.

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>>8739366
Mass doesn't literally curve space-time, that's just some terminology used to make the concept visualisable, as in pic related

You could also imagine it as spacetime being compressed around matter, or as inertial frames performing an accelerated motion towards matter etc

>>8739383
>mass is a vector

Muh sides, thanks for the kek

>>8739616
>>8739618
The helium balloon rises because helium is less dense than air, not because it has negative weight. If you managed to put a helium balloon in a vacuum, it would sink because it has mass and a directional pull. Only a particle with negative mass could have negative weight

>>8739366
You know at amusement parks those giant 3d nets you can play in? Now think of the distance between each cross section of net as an infinitesimal small distance. When you place mass in that net, the net is "pulled" toward the object. In a way, mass shortens the distance between two points.

The commonly used fabric analogy is beyter, but normie brainlets take it to actually believe objects are "falling into" spacetime when they encounter mass, which of course would be circular as it would be using gravity to demonstrate gravity.

The fabric analogy is also good because it sort of shows how black holes can "infinitly" stretch spacetime, to where objects are pretty much falling toward an asymtote. Particles approach the singularity forever in a single direction because of how compressed spacetime becomes.

Again, this is why pop science is cancer. Math perfectly explains it but dumb brainlet's need a picture that fits their intuition.

Hoped this helps.

>>8739693
>You can check the source for that claim in the wiki article if you have a problem with me referencing wikipedia.

Anybody can edit Wikipedia.

>>8739600
An Australian

>>8739896
>spacetime being compressed around matter
this makes sense

>inertial frames performing an accelerated motion towards matter
what the fuck does this even mean

>>8740940
>Anybody can edit Wikipedia.
Not him, but did you even check the reference?

>>8739616
:^)

>>8739366
Its curving into a dimension we cannot observe. You ever see the fabric with ball bearings example? In those examples we would be 2 dimensional beings. The fabric is curving into the 3rd dimension around the ball bearings, which the 2 dimensional beings would not be able to directly observe. They can however observe how it effects things that pass through this curvature and deduce that said curvature exists.

>>8742436
The inertial frames moving was something that was discussed in a philosphy of spacetime lecture course at my Uni

>inb4 meme

I do proper physics, just took that course as it was interesting and a nice change in pace

Anyways the point is to explain how gravity arises from relativity. By describing the inertial frames as performing an accelerated motion, you can look at the behaviour of matter in those frames.

E.g. an object on earth will then be accelerated upwards in the inertial frames which are "falling" towards the centre of the earth, and that force to create that acceleration is provided by the earths surface, resulting in the perception of gravity

Anyways, that's also more something you can use as a visualisation and a useful mathematical tool

>>8739366
It's curving into something called space-time, which is a kind of abstract mathematical space with special properties that we use to model the universe. "Is it really curving" isn't really a great question since what it's really doing is exactly what we observe it doing, it just so happens that GR models this in a way that makes useful predictions. Words like curving are a way of understanding the transformation that takes place of that mathematical object when mass is present, it's way of intuitively understanding what's happening, but objectively is only meaningful within the model itself. This is true of literally everything in physics though. If you asked me what a hat was, I could a. describe a hat, or b. just show you a hat, which will always be "truer" in a sense. However, a. allows me to be more general, but the price of generality is abstraction. This becomes even more difficult in physics when attempting to describe things we can't directly observe, i.e. forces.