/sci/ - Science & Math

[Anonymous No.4316266]

i honest to god dont understand gravity. after a star explodes how does gravity just start to pull things together at a particular point and start over? and why arent we flying around right now.

i know im a retard but i would appreciate some clarification in laymans terms.

[fizixfag !!2lAY/u9qu1I No.4316276]

Mass inherently attracts mass to itself. Much analogous to how positive charges and negative charges attract one another.

We don't know how exactly, there are several competing theories.

[Anonymous No.4316284]

>>4316266
Its alright, nobody understands gravity.

[Anonymous No.4316288]

>>4316276
>We don't know how exactly, there are several competing theories.
what do you mean by 'we don't know how exactly'? every prediction and axiom in GTR has been experimentally confirmed. if you are referring to canonical quantization, give me a break.

[Anonymous No.4316296]

>>4316288
GTR can explain plenty, but what explains GTR..?

[Anonymous No.4316308]

>>4316296
i can explain it to you, just tell me what do you not understand

[fizixfag !!2lAY/u9qu1I No.4316315]

>>4316288
Gravity is probably the most poorly understood of the four fundamental interactions.

[Anonymous No.4316318]

>>4316308
what makes matter pull other matter toward itself

[Anonymous No.4316325]

Am I the only one who finds it funny how gravity is the "weakest" of the four fundamental interactions, yet also the most influential and widespread?

Also, OP. This is how GRT explains gravity.

Pic related.

[Anonymous No.4316333]

>>4316325
>the most influential and widespread
Nope, I don't think so. It's just the one that we are AWARE of the most

[Anonymous No.4316334]

>>4316325
it only seems the most influential to you because you're so big. imo electromagnetism and the strong force are A LOt more influential to our everyday lives

[Anonymous No.4316339]

>>4316334

Electromagnitism would be irrelevant if not for gravity keeping shit in place for it to be necessary. Gravity is the most influential, because without it, NOTHING would exist at all. Galaxies would be completely nonexistent. Without gravity, there would be no stars. There would be no planets. There would be no Nuclear Fusion in stars, if they somehow were created. So on and so forth.

[Anonymous No.4316345]

>>4316339
good points, actually. historically it maybe have been the most significant

[Arclinon No.4316347]

Good question in fact very good one which i used to wonder a few years back and developed my own theory of fabric of the unvierse more commonly called Paper universe theory but its just a theory in its current state and that theory accepts cosmos as 4 dimensional paper and whe n too much mass gathers (neutron star) in any point of that paper it punches hole in it ( aka black holes) but when there is not enough mass to punch a hole then it bends the space towards it like putting a rock on a sheat you can actually test it using a piece of paper and some weight and try it out but it is still a theory and must be proven mathematically (and some of those formulas do not exist right now so we gotta wait) before it can become a law but for now that is what i could find closest to an answer hope it sheds some light on the issue . PS: sorry for spelling errors and grammar but cba to correct it atm hope it is still understandable

[Anonymous No.4316349]

>>4316339
We can say the same thing for the three other forces. Without any of them, nothing would be. Also, without gravity, everything would be floating and MAYBE, with some luck and electromagnetism, things would be stuck together. There would be a small chance for something to happen.

[Anonymous No.4316350]

>>4316315
in terms of describing the gravitational fields of elementary particles, sure.

from a classical approach? no. GTR, in many cases, can be considered more complete than electrodynamics.

[Anonymous No.4316352]

>>4316347
>mfw you are talking about relativity and this already accepted as the "official" theory

[Anonymous No.4316353]

what the fuck happens inside a black hole is what i wanna konw

[Anonymous No.4316354]

>>4316353
the concept of "happen" means NOThing inside a black hole. nigger

[Anonymous No.4316358]

>>4316352
that isn't at all relativity or an einstein tensor. it's crackpottery.

>>4316353
http://www.youtube.com/watch?v=GYKyt3C0oT4

[Anonymous No.4316360]

>>4316349

Gravity is, without a doubt, the weakest of the forces (to our knowledge). You are completely right in what you say, but Gravity, despite being the weakest (I mean, a fucking quarter can resist all of Earth's gravity when tied to a piece of twine), it is the most important on a macro-scale.

I hate quoting from wikipedia, but I think this paragraph sums it up nicely:

>Even though electromagnetism is far stronger than gravitation, electrostatic attraction is not relevant for large celestial bodies, such as planets, stars, and galaxies, simply because such bodies contain equal numbers of protons and electrons and so have a net electric charge of zero. Nothing "cancels" gravity, since it is only attractive, unlike electric forces which can be attractive or repulsive. On the other hand, all objects having mass are subject to the gravitational force, which only attracts. Therefore, only gravitation matters on the large scale structure of the universe.

>The long range of gravitation makes it responsible for such large-scale phenomena as the structure of galaxies, black holes, and the expansion of the universe. Gravitation also explains astronomical phenomena on more modest scales, such as planetary orbits, as well as everyday experience: objects fall; heavy objects act as if they were glued to the ground; and animals can only jump so high.

I don't want to downplay the role that electromagnitism, along with the other two very important fundamental forces, play on our Universe as a whole. Again, nothing would be the way they are without any of them. However, I think, in the grand scheme of things -- nothing could have been, at all, without Gravity. It is the driving force behind our entire Universe, and without it, there is no room for anything else. There could, theoretically, be a Universe without Electromagnitism. There couldn't without Gravity.

[Arclinon No.4316362]

Oh and btw when Newton introduced universal law of gravity he also added something like this (dont remember the exact quote) "I can explain with what force gravity affects a mass but i cannot explain how does that gravity comes to be" and in my last post i tried to explain how 2nd part works and also real theory is 6 pages long excluding calculations that was just a part of it in case you wonder...

[Anonymous No.4316371]

okay. so basically mass attracts mass, and the larger the object the stronger theyre attracted, similar to magnetic poles. is gravity centered on one point or what?

[Anonymous No.4316370]

>>4316362
He never said that.

[Anonymous No.4316376]

>>4316371
>putting name in the subject box
wow never done that one before.

[Anonymous No.4316379]

>>4316353

I've always perceived black holes like this: It is not a hole at all. All a black hole is, is super dense, super condensed, and super heavy matter. The only reason we give it the title of "infinite" gravity and mass is because there is no way to quantify it, due to the extremity of it. That's all it really is, is a ball of mass so dense it sucks in everything around it. My reasoning for this? Neutron Stars. Which are made of literally entirely Neutrons after a stars collapse, and whose mass and density work as followed:

>A neutron star is so dense that one teaspoon (5 milliliters) of its material would have a mass over 5.5×1012 kg, about 900 times the mass of the Great Pyramid of Giza.[13] The resulting force of gravity is so strong that if an object were to fall from a height of one meter it would only take one microsecond to hit the surface of the neutron star, and would do so at around 2000 kilometers per second, or 7.2 million kilometers per hour.[14]

If such a dense object could exist, I don't see how Black Holes could not simply be a slight step forward -- to the point where even light could not escape it.

[Anonymous No.4316383]

<div class="math">G_{\mu \nu}=8\pi T_{\mu \nu }</div>

There you go OP. The metric is related to energy/mass/momentum by the above equation. Objects follow geodesics through spacetime characterized by this metric.

[Anonymous No.4316389]

>>4316371
>is gravity centered on one point or what

yes we call this the center of gravity

[GR Student No.4316396]

>>4316379
>The only reason we give it the title of "infinite" gravity and mass is because there is no way to quantify it

Black holes have neither infinite gravity nor infinite mass.

Theoretical astrophysics PhD student specializing in GR, checking in.

[Anonymous No.4316399]

>>4316396

I've always heard people just slap the tag "infinite gravity and mass" to black holes. Glad to see they were fucking retarded.

[Anonymous No.4316401]

>>4316396
what are your thoughts on the holographic principle?

[GR Student No.4316406]

>>4316399

You often hear in pop science that they have infinite density. I guess that gets confused with infinite mass or gravity.

[GR Student No.4316412]

>>4316401

It's interesting, but I don't work on that so I don't have any strong opinions.

[Anonymous No.4316423]

>>4316396
>Theoretical astrophysics PhD student
are you an orthodox relativist? do you like the addition of a higgs scalar field? would you add a higgs mass term to your lagrangian?

[Anonymous No.4316435]

>>4316423
Why do people always assume the higgs field is directly related to GR? It's not.

[Anonymous No.4316442]

>>4316412
Oh well, I thought you might since you were talking about black holes

[GR Student No.4316450]

>>4316423
>are you an orthodox relativist?

I don't know what that means.

>do you like the addition of a higgs scalar field? would you add a higgs mass term to your lagrangian?

No, I would not. I study black hole mergers. I'm not even sure how such a term would alter my work.

[Anonymous No.4316462]

>>4316435
where did i ever state that? i'm a grad student myself, i'm always curious on others' opinions of the higgs. considering he's specializing in relativity, i'm simply curious.

in a philosophical sense, there are many interpretations of the constituents of the vacuum due to the absence of experimental evidence. the einstein tensor is our best classical description of the gravitational field.

[Anonymous No.4316468]

>>4316450
When two black holes collide, does that mean we can travel back in time???

[GR Student No.4316480]

>>4316468
>When two black holes collide, does that mean we can travel back in time???

Well, I can't. I don't know about you.

[Anonymous No.4316494]

>>4316480
Neil Degrasse tyson says that when black holes collide, time travel is possible

[GR Student No.4316505]

>>4316494
>Neil Degrasse tyson says that when black holes collide, time travel is possible

He says a lot of things.

He was probably referring to closed timelike curves. These are paths through spacetime which loop around on themselves, so they don't extend all the way to the past or future. Kind of like Groundhog Day.

[Anonymous No.4316506]

>>4316494
richard feynman says that when you square a double and triple a circle you consequently resonate with the vacuum and escape into the 5th dimension

[Anonymous No.4316517]

>>4316462
You're still implying that relativity is related to the Higgs field. It's not. Also, no physics grad student would say "in a philosophical sense..."

I'm not sure what you mean by "the constituents of the vacuum." I also have no idea what this has to do with the einstein tensor. And it's not the einstein tensor that provides a model for gravity, its its relation to the SE tensor.

[Anonymous No.4316589]

>>4316517
>I also have no idea what this has to do with the einstein tensor.
how do you not know what this is? the einstein tensor provides a description of curvature:
<div class="math">\mathbf{G}=\mathbf{R}-\frac{1}{2}\mathbf{g}R</div>
both are essential for the EFE.

>You're still implying that relativity is related to the Higgs field
are you incapable of english comprehension? mass generation has no correlation to any description of gravity. is that clear enough for you? this is pretty evident unless you'd like to make a mockery of yourself.

>Also, [...] would say "in a philosophical sense..."
this statement is often used to prevent a argument regarding the scientific accuracy of some point. what i stated thereafter (the nature of space-time) is not resolved in physics. (inb4 i'm an experimentalist)

>no physics grad student
what do you want me to do? post links to my published papers on an anonymous imageboard?

[Anonymous No.4316600]

>>4316589
also, just for reference:
https://www.google.com/search?ix=hcb&sourceid=chrome&ie=UTF-8&q=%22in+a+philosophical+se
nse%22#sclient=psy-ab&hl=en&source=hp&q=%22in+a+philosophical+sense%22+site:arxiv.org&am
p;pbx=1&oq=%22in+a+philosophical+sense%22+site:arxiv.org&aq=f&aqi=&aql=&gs_sm=e&
amp;gs_upl=3906l4632l2l4863l5l3l2l0l0l0l219l589l0.2.1l5l0&bav=on.2,or.r_gc.r_pw.r_cp.,cf
.osb&fp=21ae9f9a745b336d&ix=hcb&biw=1680&bih=943