So I was reading up about gravity and how objects with a bigger mass actually “bend” the fabric of space which is often called space-time. But what is it exactly?
Can we see space-time? Does it actually exist or is it just a concept/hypothetical?
Also, an article mentioned that that we need to be in the 5th dimension to actually see space-time. So, does that prove higher dimensions do in fact exist and are having an impact on our 3D world?
In: Planetary Science
Spacetime is real in the sense that we can measure it and model it and see how changes in spacetime have real effects, but it’s not actually a physical thing that you can see or touch. Rather, it’s a mathematical construct for us to understand how things exist in and move through 3 dimensions in space and 1 dimension of time, and how events can influence each other in space and time.
As to that article you read, I’m not sure where that came from, but it sounds like a pop-sci article, and you should be very careful with those because they are usually wrong. In short, no, you would not need to be a a 5th dimension to see spacetime, since spacetime isn’t a thing you can see anyway, and it does not in any way prove or even hint at the existence of higher spatial dimensions. There’s zero evidence of the existence of more than the 3 dimensions of space that we already know.
>But what is it exactly?
A set of mathematical equations which are often oversimplified to a rubber sheet.
>Can we see space-time?
Yes.
Not with our eyes, but if you shine a laser down two really long tunnels at the same time (using a special type of mirror called a beam splitter) and then recombine and “overlap” the two beams, you can see one tunnel becoming a teeny tiny bit longer than the other whenever something with mass moves past – whether that’s a car driving on the road outside or a pair of black holes merging millions of lightyears away/millions of years ago.
>Does it actually exist or is it just a concept/hypothetical?
We can also use it to see neutron stars falling into black holes and then – since waves in space-time travel slightly faster than light through the imperfect vacuum of intergalactic space – point normal telescopes at where it happened and see it happen “for real” (by which I mean using light).
>Also, an article mentioned that that we need to be in the 5th dimension to actually see space-time. So, does that prove higher dimensions do in fact exist and are having an impact on our 3D world?
On the contrary, the waves we’ve been able to see have allowed us to rule out higher dimensions existing and having an impact on our 3D world in specific ways.
Edit to clarify: higher dimensions can still exist and have impacts in various other ways. We have no evidence to say they do, but also no evidence to say they can’t.
Gravity and Momentum are pretty much the same thing. The Earth is having an effect on your momentum because it’s great mass is distorting spacetime.
We live in 3D space, which means you need 3 numbers to describe where something is in space, like “1m forward, 1m left and 1m up” uniquely describes a position in space (relative to some starting point). In spacetime you describe events using 3 numbers for the location and one for the time an event happens, like “1m forward, 1m left, 1m up and 6 seconds in the future”. Whether spacetime is real or not is more of a philosophical question, but most people would say space and time are real, and spacetime just puts them together, so it should probably also be real. The 5th dimension thing means that, since spacetime is 4 dimensional (3 space dimensions + time), in order to really see something moving through spacetime, you’d have to look at it from “outside 4d space” (i.e. at least 5d), the same way you can only see an entire sheet of paper (2d) if you’re looking at it from above (3d).
What is it? We don’t really know it is one of the key discussions in modern physics, we can see and measure the impact, but can see what is causing it directly. https://youtu.be/3NWnSdBq5eg
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