degrawj

okay, this is like the fourth or fifth time that i have gone through this thread reading peoples posts and i just can't help but get really ticked off. i am pretty disappointed that somebody such as a moderator would make a post such as this. as far as i read, the point of the original thread was essentially "wow, this is really wierd and interesting, what are your thoughts on it?" not, "what are your opinions on space exploration and whether or not we should spend money on it." i have gotten reprimanded several times for leaving posts that were off subject and semi-tasteless. but a respectful moderator can feel free to toss his opinion around when it's not the topic of discussion? i wouldn't be surprised if this post gets edited or deleted but this is a serious issue and i hope that somebody does something about it.

taog

That's interesting about supermassive black holes. I didn't know they had such a large 'radius'. I guess they are a lot bigger than i thought. I really don' tknow much about black holes, but find it very interesting that you study them for a living. What do you do exactly?

Also, most of this type of astronomy isn't funded by the government. A lot of it is worked on by profs and students. The students pay the prof's wages, so the students are paying for the research on said topics to be done.

NASA is a space agency, not an astronomical agency. Though they are directly related, and NASA is astronomy based, the goal of NASA is more for inner solar system research, rather than what's beyond the solar system. Though, now it seems that bush has made NASA's biggest goal manned missions to the moon and mars, which i believe is usless right now.

Anyway, the greatest minds and the best discoveries are founded and funded by universities rather than your taxes.

Other than that, Astronomy is good for the reasons that have been stated in this thread.

One huge thing that people need to realize is the fact that an asteriod or meteor could crash into earth, and either destroy earth on impact, or start a nuclear war or something, if a big enough meteor landed overtop of a country who has nuclear weapons. Imagine that, the blast would look like a nuclear explosion, which would cause a chain reaction of 'who bombed us'. The country where the meteor hit might believe it was their enemy, and turn around and bomb them. This could lead to a nuclear war, and the destruction of earth.

This is fully possible. A lot of people would say, 'we have the sky covered. We can see what is coming towards us and when.' The fact is, we won't know, and we can't see. It's impossible to watch every portion of the sky for asteriods of meteors coming to earth, and picking up ones that are heading our way, before it's too late. Hell, a few years back some astronomers noticed another object orbiting earth. At first, astronomers thought this might have been a second moon to earth that had been missed for hundreds of years. It ended up being part of some spacecraft, a mission to jupiter i think. Astronomers weren't surprised that we could have missed a second moon to earth. This proves that we don't have that close of an eye on the sky.

So, astronomy gives us at least a bit more of a chance, because we are always watching the sky. Becauise of astronomy, we just might have a chance to beat that asteriod that just might be heading for earths path right now.

cchris

Hey degrawj,I wouldn't worry about it too much as it is people such as yourself that keep people like me posting about weird and wonderful stuff anyway.
Iv'e been around here long enough to know that persistence is the key to getting a point across and occasionally threads go way off topic due to reading something the wrong way.

An example was this.

I thought this hilarious but he and I are more insignificant than his mother in law.

analog may believe that money spent on this is wasted but others don't.
I personally don't have a problem with that so I hope we can all get back on track here.

"Goes back to building space ship".

__________________
There's a fine line between participation and mockery

stingc

I do theoretical work in general relativity. So I don't go looking for black holes etc., but work out their (expected) properties, and things related to that.

Recently, I've been looking into the gravitational self-force/radiation reaction problem. An accelerated object will emit gravitational radiation (like a charge will emit light). This carries away energy, so the object will feel a force due to its own radiation. It turns out to be very difficult to work this out properly, but its understanding it has a lot of interesting implications.

You're right that most of these sorts of things are studied at universities, but a large chunk of their money ultimately comes from the government.

Lasereth

I imagine that the astronomers simply used an already-built satellite (probably Hubble since our atmosphere makes Earth-based telescopes exponentionally less-powerful than satellite-scopes in orbit) to find out this information. Not that much money was used. Either way, astronomy is a very, very important science.

Awesome article -- I took Astronomy 1 and 2 at college the past year and can say that it's *easily* the most interesting classes I've had (and probably ever will have).

-Lasereth

__________________
"A Darwinian attacks his theory, seeking to find flaws. An ID believer defends his theory, seeking to conceal flaws." -Roger Ebert

SpikeQX99

Science is hard...

But cool..

Supermassive black holes... Maybe if when we think about it, the answer is like a toilet? We are on the outskirts, whirling around in circles till one day we finally make it in to the center of the black hole, then down the drain we go?

Hmm....

__________________
I'm so in love with a girl... she is my everything

taog

Wow, that's amazing. Congrats on being one of the few people in the world that actually challanges their mind on a regular basis. What did you take in school to land something like that? Also, if you don't mind, what is the company you work for?


I'll sum up what I believe a black hole is. Though, like i have stated, I'm no expert on black holes. stingc would probably be able to give us a much better explanation of a black hole.

Basically a black hole is something that has such an intense gravitational force that it even traps light.

Now, black holes to reside at the centre of galaxies, but it doesn't mean that we are going to be sucked into that black hole. We are so far from the black hole at the centre of our galaxy that it's gravitational pull doesn't have any effect on us at all.

Our orbit in our galaxy isn't influenced by the black hole at the centre. Rather, it's influenced by the cluster of stars and the overall gravitational force of everything in our galaxy combined.

Again, I don't know a whole lot about the makeup of galaxies, or how they came to be, but I do know that we don't have to worry about being sucked into the black hole at the centre of our galaxy. That gives you an idea of how large our galaxy is, and how large this new black hole finding is, also.

However, it is possible that there is a black hole close to us. This wouldn't be a supermassive black hole. It would be small, but 'could' gobble up our solar system, if we got close enough. Though, it would take a long time for it to finally reach our planet. We would be warned of the black hole way ahead of time.

In other words, we can't really think of it as your toilet scenerio. It's an interesting thought, and kind of works for objects in the range of the black holes gravity, but the matter is just condenced and accelerated to speeds higher than the speed of light, or so people think. This is where many questions about black holes come into play. Relativity suggests that nothing with a mass can go the speed of light. If it does, it's mass will be infinite, since your mass increases as you move faster, it's speed of time would be 0, and the energy it would take to get to that speed would also be infinite. It's very hard to think about.

Black holes are very interesting for many reasons.

If you are interested in astronomy, this is a great site to go for definitions of things.

www.bbc.co.uk/science/space

sailor

This is *so* f-ing cool. I love astronomy.

__________________
"Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws."
--Plato

SpikeQX99

Well, taog, I thank you for the explanation.

I kinda sorta knew what a black hole did, but then you got into the whole infinite mass, speed, and all that stuff, and with the condition I'm in tonight, I'm just gonna restate my past opinion and say that...

Science is hard...

But cool!

Thanks for the clarification!

__________________
I'm so in love with a girl... she is my everything

Moobie

One last post about how astronomy aids mankind. Anybody remember late last year when the Sun was freaking out and hosing us with solar flares? Because there are a bunch of scientist up on the hill checking out the heavens we were able to know in advance that the Earth was about to get rocked by solar radiation. This gave people enough time to shut down satellites and save their electronics from the effects. This probably saved us millions of dollars and a huge headache. There are things out there that can affect us, and it's probably a good idea that we know about that stuff.

And besides like G.I. Joe says "Knowing is half the battle!"

__________________
Obscenity is the crutch of inarticulate motherfuckers.

We like money. Give us your money you stupid consumer whore.

taog

Nice. That's my second favourite quote. My first one is, 'imagination is more important than knowledge. Knowledge is limited, imagination encircles the world' - Albert Einstein.

In science you need to have a good imagination. If Einstein didn't have a good imagination, i bet he wouldn't have been able to come up with half the stuff he came up with. He had the intelligence to apply it with math, and come up with one of, if not the greatest known theory in the world. General and special theory of relativity gives us so much knowledge about so many different things. Take a look at E=mc^2 for example, the most well known formula in the world. If this didn't exist, we woudln't have half of the weapons we have on earth today. True, in this case, it was used for something bad, but the same thing can come out to result in something good.

Energy is a huge topic in astronomy. Figuring out how to do things differently, using less energy, or using a better way to come about that energy is challanged in all areas of science. These things are then applied to our every day lives. Knowing how we were created, and figuring it out, by looking at nebulae and things like that, gives us a better understanding of how things are formed, and thus, a better understanding about how to conserve these things. Again, a good thing that has come out of it is how to harness the energy in our every day lives.

There has been so much work done with different types of waves in astronomy as well. If astronomy didn't exist, I'm sure that half of these things wouldn't be known about different types of waves. We would know little about them, and little about how to keep ourselves shaded from the harmful waves that are entering our atmosphere on a daily basis.

Knowing if half the battle. Acting upon the knowledge is the other half. You can't know unless you use your imagination and figure the knowledge out. Astronomy helps us in so many aspects, including individual intelligence.

If it weren't for astronomy, there is no way I would have applied myself and there is no way I would be willing to use my brain at it's true potential. Astronomy is my love, and I know it will challange my brain on a daily basis, as it already does. It brings me intelligence, and lets me feel like I'm doing something good for myself. It makes me happy when i read about a theory and fully understand the meaning behind it. It makes me feel good to come on here and post about what I have learned, so I can give other people a bit of my knowledge. If one million people feel the same way, it's also helping society on a person to person basis. It might just keep some people from being a menace to society.

What I have learned is that we shouldn't knock any profession. Each profession has it's own little way of bringing back good to society or humanity. Even if it's owning one of the biggest companies in the world who doesn't like to finish their operating systems before they start a new one.

I used to think that Archaeology was a usless science. I have now learned that there are many good things that come out of Archaeology. I'm an 'Archaeologist' at the moment actually. I am working for an archaeology company, doing field work and things like that. It's quite interesting to find out what you can find out about the past. There are many things that you can apply to our lives today, to better the way we live, or to help with how we do things.

It's true that most sciences also focus on pure subject related knowledge and information, but all sciences will apply to how we live our lives in some way or another, moreso than you would expect most of the time.

On a last note for this 'argument', Astronomy and every area related all relate back to physics someway or another. Our lives depend on physics more than any other science out there. Some type of physics can be applied to basically anything you do in your daily routine. A lot of physics has been foud or proven through astronomy, and thus used in our daily lives, even though you might not be able to tell. Your whole house is controlled by physics. A lot of those devices in your house have been constructed trhough the finding of proofs and theories proven through physics, astronomy, or some other science. It's all about figuring something out, and applying it to somehing on earth. It just makes sense to do that, and scientists do that daily. They use their imagination to apply things to make things easier for us, or more efficient.

Anyway, that's why science is the best thing for us.

Now, back to topic.

That guy who's doing research and stuff on black holes. Would you be able to kind of sum up what a black hole is exactly for everyone to read? I am basing my explanation on readings from old text books, and I don't really know if anything new has been figured out.

Also, if you could, could you maybe explain the event horizon a little too? That's always an interesting black hole subject.

denim

And, why is the radius of a black hole potentially infinite?

Arsenic7

I'm a little confused by your "time was faster in the past" statement because, well, how can that possibly be an objective statement?

I've started thinking of time as a measurement of change and that thinking has helped me out a bit. So if what you mean is that more stuff went on in the past...ie. the universe was changing more, matter was less stable and chaotic, then yeah, I understand that.

__________________
This is no sig.

stingc

Plenty of new things have been figured out, but the basics are the same. You mostly have the right idea, although you've confused some details. All that stuff about going faster than light is incorrect for example.

I'll try to describe a black hole intuitively. This is very very minimal btw:

If you think about the gravitational field of a planet, it obviously gets stronger as you get closer to it. There's a limit though. If you dug a hole into the planet's surface, you'd find that the field starts getting small again. It vanishes completely at the center (by symmetry).

So a planet has the most gravitational pull at its surface. This suggests a very simple way of increasing the maximum field: let the planet collapse into itself without losing any mass.

A black hole is something that has collapsed as much as possible. If you get close enough to one, its gravitational field is so strong that not even light could ever fully escape.

It is important to say that black holes are not cosmic vacuum cleaners. The collapse process only increases the maximum gravitational field. It doesn't affect anything far away. If the sun could turn into a black hole right now, the earth would continue moving along in exactly the same orbit. Strange things only happen if you go too close.

These 'strange things' are what really make black holes interesting I think. In general relativity, gravity is a manifestation of geometry. It turns out that geometry doesn't quite work the way you learned in high school. There are very minute differences that give rise to the effects we associate with gravity. It is rather difficult to think of the attraction between the sun and the earth this way, and it isn't really needed (although it can be done). Newton's old theory works fine for that. When you start to talk about black holes, though, the geometrical viewpoint is unavoidable. Regular Euclidean geometry completely breaks down.

The replacement describes both space and time as a single intertwined structure. So both time and space act very differently near a black hole. Expanding on that more precisely would take many pages to explain properly.

Arsenic is right that time is a measure of change, but it can be quantified in various ways. You have to be very careful though because different people might quantify it differently. When someone talks about time "slowing down," or something like that, they mean that time as quantified by one person (in an apparently reasonable way) does not agree with someone else's apparently reasonable version of time. That's probably confusing, but it can be made precise. People should be much more careful about discussing time in relativity because most of the time their statements do end up being completely subjective (I'm including physicists here too). Its possible to do it right though.

denim, just like time, space can be quantified in different ways. There are definitions in which the radius of a black hole is infinite, but it doesn't mean much to say that. Someone looking at the hole will see something that certainly doesn't seem infinite. Its better to measure its surface area (there's more than one reasonable definition of surface too -- just choose one), which is always finite, and would be measured the same by everyone.

My degrees are in physics. I'm at Penn State right now (there's a big gravity group here). Companies don't hire anyone to do this kind of research.

Nisses

I guess what is important to keep track of in all that, is the name "theory of relativity".

As in, it's all about different perceptions, relative to where the perception was made. So to person X, outside of the range of gravitational pull of a black hole, it might take 4 hours to see another person Y come out of the black hole, while to the person Y it might seem like it only took 4 minutes.

The same way, when the universe was young, and alot more close together, there was more intense gravity between holes, planets and stars on the whole (since gravity becomes weaker at greater distances). So time indeed did pass faster. Gravity was higher, so time-space was warped to a greater degree.

At least, that's how I understand it

__________________
Moderation should be moderately moderated.

Nisses

stingc:

if an accelerated object emits a gravitational radiation, and for a planet to revolve around the sun, it takes a constant accelaration towards the sun, does that mean that the earth produces gravity in 2 kinds? as in: acceleration gravity and mass-based gravity?

or am I thinking too far and not getting it right anyway?

__________________
Moderation should be moderately moderated.

denim

I think a more interesting question is, what is the speed of gravity? I've read somewhere that it's many orders of magnitude faster than light.

RelaX

Perhaps the great publishing companies of Ursa Minor were the ones trying to bind together the rules of Brockian Ultra Cricket.

"None of these facts, however strange or inexplicable, is as
strange or inexplicable as the rules of the game of Brockian Ultra
Cricket, as played in the higher dimensions. A full set of rules is
so massively complicated that the only time they were all bound
together in a single volume they underwent gravitational collapse and
became a black hole."

__________________
The most likely way for the world to be destroyed, most experts agree, is by accident. That's where we come in; we're computer professionals. We cause accidents.
- Nathaniel Borenstein

Nisses

hu??
where did I type this then?

__________________
Moderation should be moderately moderated.

Ace_O_Spades

If we don't know anything about the world around us, and the universe we live in, how will we expand our scientific knowledge and understanding?

The advancement of knowlege and the scientific pursuits are actually high priorities in my book.

__________________
Feh.

stingc

That's right. The 'acceleration gravity' is immeasurably small in the case of the earth though. It takes a much more extreme situation for the effect to become significant.

There are systems with two very small (but massive) stars orbiting each other once every few hours (!) where the acceleration is enough to cause an observable energy loss. Hulse and Taylor were given a Nobel prize a few years ago for showing that this happened in exactly the amount predicted.

denim,
The speed of gravity is yet another thing that is hard to define. You measure how fast something is going by finding how far it goes in a given time. Since gravity is itself changing the nature of space and time as it goes along, its hard to think of what it would mean to define a speed for it.

It only makes sense if we ask what is the speed of a very weak gravitational wave, so geometry remains almost constant as the wave passes. In that case, relativity predicts that the speed of gravity has components travelling at the speed of light and all slower speeds in general. In the solar system, the components moving at less than the speed of light would be negligible, but they're important in more extreme situations.

denim

So define "time" and "gravity".

stingc

I can't do it simply.

denim

How do they relate? I can't find my 22 year old physics book, so I'm afraid you'll have to start from g and t.

stingc

t and g don't relate in Newtonian physics, so I doubt your old text will talk about it. I'll try to give the first steps towards what's involved. I don't expect people without a technical background to understand this.

The metric in Euclidean geometry is given by the pythagorean theorem, dL^2=dx^2+dy^2+dz^2. {x,y,z} are not intrinsically meaningful. There's nothing preventing you from going to any number of different coordinate systems. L does have meaning though. The distance between any two points is the same for everyone.

Special relativity modified this relation by introducing a fourth coordinate -- time:

dL^2=-(cdt)^2+dx^2+dy^2+dz^2

Just like {x,y,z}, t is not fundamental. You can do coordinate transformations on it. L is again the same to everybody.

This is used to define what it means for something to be moving at the speed of light independent of coordinate choices. If dL=0 along an objects path (in 4D spacetime), then it is moving at light speed. In the above coordinates, this means e.g. dx/dt=c, as expected.

Objects moving at less than the speed of light have dL^2<0 (its ok for dL to be imaginary). One can define what's called the proper time as dT^2=-dL^2. This is uniquely defined, and has many nice properties.

If dL^2>0, then this represents something moving faster than light. Its possible to show with the above equation that an object moving on this type of path will violate causality.

Now as stated before, there are many possible forms for dL depending on the coordinates chosen. If there's no gravity, though, it is always possible to transform back to the metric given above. Gravity modifies the equation for L such that it can no longer be brought into that simple form by any choice of coordinates. Its probably better to say that gravity IS the (invariant) difference in the true metric and the special relativistic version.

redarrow

Ok so I was ignorant. But Im pretty pissed that money is being spent on things that we dont need to know about. Why the fuck are these people studying black holes while they should be looking out for meteors?

And on the black holes, if light isnt matter, how can it be pulled by gravity?

denim

Redarrow, you're still acting ignorant. Go back and re-read the thread again. If that doesn't work, come back in 10 years once you've got some real life experience. The question will likely resolve itself for you in the meantime.

Black holes pull everything, not just matter. Matter is a dense form of energy, so saying gravity pulls matter is just another way to say it pulls energy too. Light is a form of energy, if I understand correctly, so gravity can bend it.

denim

Okay, there are still a couple of things I'm missing. L is what? If gravity makes the situation less simple, just what kind of math is needed? You got into some level 1 calculus there, I see, but I wonder what I'd need to take to add in gravity.

stingc

L is a (4D) distance. Its useful to talk about because knowing distances between points in a space allows you to derive almost anything else you might be interested in (there are important exceptions though).

dL is always a quadratic function in the four coordinates, even with gravity. It is a solution of Einstein's equation, which is a nonlinear partial differential equation.

Most of this falls under differential geometry. Tensor calculus is also very useful.

taog

hey, stingc

I was wondering if you would be interested in helping out on a database type website for astronomy and related topics. I'll get into more detail later, but basically what I plan on doing is creating a huge complex database of different theories and things like that, including different scientists and everything, that is searchable and everything. It will take me a bit to get the basic database design going, and to actually get a small site going, but I'm just wondering if you would be interested in helping out populate the database?


Also, I hope to make it bigger than just astronomy. I hope to merge many different science databases into one kind of thing. It will take a few years to get that far, but I think it will be very rewarding in the future.


Oh yeah, and back on topic.

This black hole doesn't seem so 'surprising' if you read about different ways and theories on how the universe may have started. Some of them would suggest that something like this could have spawned only 1 billion years after the big bang. It's an amazing find, and I'm probably more excited about it than most people on here, but from reading some books this week about the early universe, it doesn't seem taht surprising that something like this existed 12.7 billion years ago.

stingc

Ok, maybe. PM me with more details.

tecoyah

I believe there is now a theoretical possibilty that Photons have an extremely small amount of mass, and are thus suseptible to large gravitational fields, I could be wrong in this. But, I guess we could just kill all funding to find out and instead focus on NEO's as you suggest.

__________________
Holding onto anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one who gets burned. - Buddha