The speed of gravity

The internet is full of cats and porn. No breaking news, here. There are a lot of other places with interesting information, though. One of them is the askscience of reddit. If you follow the link, you'll find this one too.

The question stated is: if gravity is transferred at $c$ (speed of light), and Sun is 8 minutes away at $c$, regarding the fact the Sun moves, does it mean Earth is attracted to the position the Sun had 8 minutes ago?

Video is from a guy named DjSadhu. Music is cool, if you ask me.

Spacetime as a consequence of something else: ER=EPR.

There's so much I don't know about GR that talking about interpretations and physics trends is a dangerous matter, specially if my words are intended to be, you know, taken seriously. That's the reason I try to focus in learning instead of trying to develop things on my own. And I don't always succeed anyway, so look at that.

Nevertheless sometimes comes the time when you find something interesting and you have to share it and... Well, hell, this is my blog, right?

I have found recently the ER=EPR conjecture and I have tried to learn a bit about it. Shall we talk about it a little? I'll go on with Schwarzschild metric inside the Earth a little bit later. :)

EFE -for beginners!

A short post again, sorry.

Looking for info into old posts, youtube has pointed out a nice video from user DrPhysicsA which seems... shiny!

Old fashinated english accent (I think it's English, pretty sure not American nor Australian, nor Irish... what else could it be?) for 2 hours of EFE fun!

The Cavendish experiment

Disappointed with this blog? Yeah, sorry again. Too much time between posts and I'm not getting very deep in any subject I deal with. That's because it requires time, and that's a thing I didn't nor I have at the moment.

So, let's talk about a funny experiment finally I've found in the internets. It's called Cavendish experiment and you can get good historical explanations of it here and here.

The experiment seems easy to follow. In Newtonian terms, two masses attract each other.

Proportionally to the masses, inverse proportionality to distance squared. But proportional doesn't mean equal. There's a constant in somewhere you have to add to make things right. Unit conversion stuff. Kinky stuff. If you want to measure how much does it weight Earth (is there anything British-er than asking yourself that kind of questions? ) you need to get that constant first.

But, how can you measure the gravitational constant without knowing Earth mass? And harder still, you are living on Earth. In case you figure out a way of measuring without taking into account Earth gravitational pull, doesn't it still f*ck with your measurements?

Before explaining something you probably already know I need to make clear why am I interested in Cavendish experiment:

1. It's an "easy" experiment which allows us to understand gravity in human size scales.
2. What is its relationship with space-time? Before you say human scales are Newtonian, which is almost truth for every almost example you can find, just keep on reading.

Leonard Susskind's GR lectures at Stanford.

I discovered Leonard Susskind because of the book "The black hole war". It was interesting and funny and the fact I was not able to grasp the last part of it -that holographic metaphore is disturbing-, didn't make me dislike it at all. I started to look at physicists more like human beings thanks to it. And that's saying a lot.

Before that, my only contact with physicists were close related hate-filled-relationships due to the fact engineering physics in Spain -the time I studied it, at least- were intended more to make an IQ selection than teaching actual interesting physics. I can blame no one for that. It's a consequence -one of the bad ones- of having a public university model. Good ones outnumbered bad ones, by the way. In the future, who knows.

 

Leonard Susskind a couple of years ago. From Stanford web.

What is happening at JSC?

Sorry for abandoning Math so soon. It is temporary, I promise. For the moment, I have to discuss another -possible- dead end. Which maybe it is not. I don't know yet. Media hype? Likely.

JSC stands for Johnson Space Center, which is one out of the 17 centers NASA has in the States.

I have heard some noise in the internet since September in sites like Gizmodo and Space.com about a JSC's scientist who claim feasibility of warping spacetime under certain specifications. Reliable science news, unfortunately, doesn't come from news sources, so I decided to wait a little before start looking for info.

Aerial view of JSC in 1989 -a long time ago, I know-. (Source: wikipedia)

Rotating superconductors. A dead end?

First time I heard about these, was back in 2006. And it seemed promising. It is a simple concept: Einstein says energy or matter warps spacetime. Why don't we modify matter in order to alter somehow spacetime?

Obviously, harvesting energy as I have pointed out previously is not going to be enough.

So, is it possible to have a "weird" state of matter which gives us more juice for warping porpuses? The idea is quite attractive, because Einstein was an open enemy of quantum theory, and this branch of physics has evolved a lot since Einstein's first days.

 

Experimental ARC Seibersdorf 2006 setup (photo from ESA web)

An interesting video from MIT: EFE, introductory level.

Next post was intended to be an estimation of energy needed for warping spacetime, but its going to take a little more of time since I have to do some checkup on math -and procedure.

So, in the mean time... :)

... I've already said I'm not very fond of hearing classes. In general it is quite truth, but in my quest for understanding spacetime, several internet searches have leaded me to actual videos of classes. Which is a little ironic, I guess...