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Author Topic: Black Holes?  (Read 14417 times)

ruletheuniverse!

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Black Holes?
« on: September 25, 2008, 06:44:05 PM »
I had a question. if a black hole has near infinite density. how does it remain at a maximum of Zero velocity. i mean if a object equal to at least 10 solar masses how come it is not moving at all?

Dan Dixon

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Re: Black Holes?
« Reply #1 on: September 26, 2008, 02:02:40 PM »
I'm not sure I understand your question...

Being massive doesn't mean that it will move. In Universe Sandbox an object will only move if you give it some velocity (hit the Nudge button) or the gravitational force of another object pulls on it.

Does that help?

ruletheuniverse!

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Re: Black Holes?
« Reply #2 on: September 29, 2008, 01:00:18 PM »
Ummmmmm hehe NO

Dan Dixon

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Re: Black Holes?
« Reply #3 on: September 29, 2008, 01:28:06 PM »
What do you mean by "how does it remain at a maximum of Zero velocity. i mean if a object equal to at least 10 solar masses how come it is not moving at all?"

Why would it move by itself?  Help me understand your question. :)

Frosty10001

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Re: Black Holes?
« Reply #4 on: October 01, 2008, 04:50:55 AM »
Hmm.. I think I might have an idea of what ruletheuniverse! is talking about.. Since a object with the mass about 10 solar masses would be very slow to move, since the milky way is a galaxy and takes millions of light years to move, thats why your object with that much mass couldn't move in your expectations.

Dan Dixon

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Re: Black Holes?
« Reply #5 on: October 02, 2008, 05:02:34 PM »
Here's how gravity works:

Everything pulls on everything else.

If you put a 10 solar mass object as far away as Jupiter from our Sun... It would be pulled on by our Sun as much the Sun pulls on Jupiter. But because the 10 solar mass object is so big... it might seem that it's not moving as much. (And consider that the 10 solar mass object would also be pulling on the Sun.)

This is an experiment you can do in Universe Sandbox.

Does that help?




ruletheuniverse!

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Re: Black Holes?
« Reply #6 on: October 08, 2008, 04:49:29 PM »
well if the black hole is at a density of ten solar masses. how come it is moving at all? i mean if there is something that has a bigger density then what is it?

Dan Dixon

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Re: Black Holes?
« Reply #7 on: October 08, 2008, 05:48:02 PM »
If you drop a feather and a hammer from the same height in a vacuum they are accelerated equally by the planet or moon or star and will hit the surface at the same time.

Feather & Hammer Drop on Moon


If you drop a car and hammer they will fall at the same rate. So... if you drop a Jupiter and a 10 solar mass they will fall at the same rate.

But keep in mind that the feather and hammer were also pulling on the moon since everything pulls on everything else (it's just so little that it wasn't noticeable). In the case of Jupiter or a 10 solar mass it would be very noticeable.

Even a feather would move a 10 solar mass (it would just be very, very little).

Here's an experiment I just tried:
I created two objects, a 1000000 kg mass and one with a mass of 10 Suns. I placed them 1 AU apart (the distance from the earth to the Sun). The massive star swallowed the smaller object after pulling on it for about 20 days, but not before it moved the 10 solar mass object .0000000000000078 meters. :) It didn't move the star much, but it did move it.

Does that make sense?

Everything pulls on everything else. That's why a 10 solar mass would move.

travisg

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Re: Black Holes?
« Reply #8 on: October 22, 2008, 01:08:41 PM »


If you drop a car and hammer they will fall at the same rate. So... if you drop a Jupiter and a 10 solar mass they will fall at the same rate.


well i don't think that's right. the bigger the mass of the object, the faster it will accelerate in direction to it's "parent" body. (see mr. newton: gravitational force = gravitational_constant*((mass_of_object_1 * mass_of_object_2) / distance_of_the_two^2)). but the differences in weight in comparison to it's parent body in yor examples are so small that you won't notice any difference. but if you (for example) throw a black hole which has the mass of our moon onto earth, you will notice that it'l accelerate much faster than a feather (well, if everything around earth would be in a vacuum, that is)

Dan Dixon

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Re: Black Holes?
« Reply #9 on: October 26, 2008, 01:58:35 PM »
A large object (a moon) might appear to fall toward a planet faster than a small object (a feather) because the large object is also pulling the planet toward it. So in that example the moon and planet would collide more quickly than a feature 'dropped' from the same distance as the moon. But if the position of the planet was locked down (something you can't currently do in Universe Sandbox, but something I will add) then the feather and moon (or even a supermassive black hole) would all fall toward the earth at the same rate.

Newton's Law of Gravitation:
Force = Gravity Constant * (Mass of A * Mass of B) / (Distance between Mass A & Mass B) ^2
is the force for both bodies (the moon and the planet) but in order to find a single body's acceleration you just use the mass of the other body:
Force on Object B = G * (Mass of A) / (Distance between Mass A & Mass B) ^2


travisg

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Re: Black Holes?
« Reply #10 on: October 27, 2008, 01:27:05 PM »
A large object (a moon) might appear to fall toward a planet faster than a small object (a feather) because the large object is also pulling the planet toward it. So in that example the moon and planet would collide more quickly than a feature 'dropped' from the same distance as the moon. But if the position of the planet was locked down (something you can't currently do in Universe Sandbox, but something I will add) then the feather and moon (or even a supermassive black hole) would all fall toward the earth at the same rate.

Newton's Law of Gravitation:
Force = Gravity Constant * (Mass of A * Mass of B) / (Distance between Mass A & Mass B) ^2
is the force for both bodies (the moon and the planet) but in order to find a single body's acceleration you just use the mass of the other body:
Force on Object B = G * (Mass of A) / (Distance between Mass A & Mass B) ^2



yeah, if one of the bodies is somehow locked that's right. i somehow missed that point in your posts, sorry bout that.

Dan Dixon

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Re: Black Holes?
« Reply #11 on: October 27, 2008, 01:29:18 PM »
No worries... I wasn't completely clear about that.

Thanks for pointing out the ambiguity.

Rock on.

bessy

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Re: Black Holes?
« Reply #12 on: October 07, 2009, 01:49:11 PM »
for some insite into why the feather would hit the planet first see my post in thread

Gravitational Force Between Bodies

qwew80

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Re: Black Holes?
« Reply #13 on: October 07, 2009, 02:27:45 PM »
Wait, isn't there something wrong with newton's universe? In fact, according to the book I'm reading right now, there are plenty of things wring. 1. Time varies by movement, meaning someone travelling at the speed of light would barely age, and that space and time is not seperate, but intertwined, like space-time. 2. If a supermassive black hole and the Earth were travelling at the speed of light with no interaction with each other, the Earth would actually get further faster then the black hole. 3. If a car and a hammer were dropped from a very high point on Earth, the gravity of the car would not only pull on the gravity of the Earth, but the gravity of the hammer as well. Newton also said that the positions and movements in space (including Earth and it's objects) should all be measurable relative to some non-moving, absolute "frame of reference" called "the ether", which was later proven to be non existent with the help of Einstein's theories of relativity along with some tests that failed to prove the existence of "the ether"

Alex_Ian_Hamilton

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Re: Black Holes?
« Reply #14 on: October 09, 2009, 12:24:36 PM »
Hi qwew80
I'll try to respond to your statements one-by-one, I think you're right overall, but confused on some fine details.

1) yes, your perception of time is related to your speed (imagine you have a watch on), the faster you travel, the slower you experience time (your watch slows and things around you seem to be going faster because your actually going slower); in theory, at the extreme of  the speed of light (the maximum speed allowed in the universe) you will no-longer experience time (your watch stops, you may move a great distance, but to you it'll have taken no time at all). The same is true if you're in a gravitational field, the stronger the field, the slower your watch will run. (and in the extreme, if you hit the event horizon of a black hole, in theory you will no-longer experience time, your watch stops, again)

2) Mainly, according to the theory of relativity, no massive object (i.e. object with any mass, from a heavy planet to a puni particle) could ever reach the speed of light, it would require an infinite amount of energy as the mass would tend towards infinite.
I tried to answer further, but things get hard when you ignore one fundamental law and assume things could work...

3) Firstly, you've made a bit of an inaccurate statement saying “the gravity of the car would not only pull on the gravity of the Earth...”; in the case of falling bodies you should say that the gravity of the Earth pulls the Car... Gravity pulling gravity sounds confusing.
But yes, you're right, the ether model was disproved; however Newton's theories can be applied if you set any arbitrary reference frame; though in relativistic extremes, his theories don't work.
In relativity, the very concept is that any “inertial frame of reference” (which is a complicated concept) is a good frame of reference; so for example, if I wanted to calculate what happens to things around me as I sit in a moving spacecraft (moving in a straight line at a constant velocity), then I could use myself as a stationary point in my reference frame, and the maths will workout for everything around me.
Equally, it's just as true that for another spacecraft (moving in a straight line at a constant velocity, even if it doesn't match mine) can decide that they're the stationary point in their reference frame, and the maths still all works out.
(it doesn't matter which inertial reference frame I use, both work)

In the long run tho, Newtonian dynamics are wrong, but only in extreme cases (moving near the speed of light, in strong gravitational fields...); but as a general rule you would never notice the difference. Of the 8 planets in the solar system (no Pluto, sorry), you can almost exactly calculate the motions of 7 of them with Newton's laws (Mercury is so close to the sun it causes issues), and the last is only inaccurate by a few percent.
I'd love Universe Sandbox to support relativistic physics, but considering you need a degree in maths to even touch upon it and it'd definitely eat my laptop for breakfast (the maths of relativity is notoriously hard, unlike Newtonian dynamics)...
I'm OK with Newtonian dynamics for now...
In-fact, most models of the Universe we run on supercomputers use newtonian dynamics, if we didn't then those suer computers wouldn't be anywhere near powerful enough.

I hope this helps.

Please, if anybody notices a mistake with my post, then tell me... Thanks

qwew80

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Re: Black Holes?
« Reply #15 on: October 12, 2009, 06:05:17 PM »
Thank you for that very informative reply, Alex_Ian_Hamilton, but I have one more question:

If you were to go faster than the speed of light (eg. using tackeyons) would we actually get younger, or what? Please try to answer me in any way, even if you don't know. Just guess!


P.S. Most of the time, I am using a school laptop. Technically, it is mine, but I have to use this because my mom won't let me use our P.C. very often (i'm only eleven).

Alex_Ian_Hamilton

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Re: Black Holes?
« Reply #16 on: October 13, 2009, 11:31:37 AM »
Hi qwew80,

Tough one to answer...
Tachyons are weird theoretical particles (like photons for light); but unlike photons, the less energy you give a tachyon, the faster they go (and they must ALWAYS go faster than the speed of light).
Unfortunately, tachyons probably don’t exist, which is very good for relativity, because relativity really doesn’t like things to go faster than the speed of light; in relativity nothing travels faster than light, and that’s kinda a strict rule of the Universe or else you have issues with “causality” (the way that one thing leads to another like a chain, it doesn’t work if some things break the speed of light).
If tachyons did exist, then they might experience reverse time too up (so they start life at the end of the Universe, and travel through time until the Big Bang), but remember that they are just particles; even if they exist, then you can’t use them to get past the speed of light in the same way that you can’t use photons of light to reach the speed of light.
For a person, the best I can really say is that when you get past the speed of light, the equations of relativity get really “funny” and just don’t work; but time seems to be a one-way trip for us anyway (we can do weird stuff to slow it down, or even stop it, but it never seems to reverse for us). So in my opinion, nope, we’d still be going forwards in time IF we could get faster than light...

On the idea of aging backwards, I hear that some people think that anti-matter is actually travelling backwards in time (again, they start at the end and work their way to the beginning (the Big Bang)); it sounds silly, but if you took a video of a pool table where one ball hits another, and then reverse the tape you can see that it’d look the same (and if you’re into the maths it actually works); it’s just all in reverse, so it could actually be true.

Good question for 11; at your age I didn’t have any idea about  this sort of stuff. I hope my answer helps.
Just say if you want more info...  :)

monmarfori

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Re: Black Holes?
« Reply #17 on: October 13, 2009, 01:46:41 PM »
In about 2020 some things looks upgraded and showing airships flying. I am now 20 at that time. So we have to detect black holes better.

qwew80

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Re: Black Holes?
« Reply #18 on: October 13, 2009, 01:55:33 PM »
Ok, than, suppose Tackeyons do exist, and we could find out how they were created. Could we use this energy source to achieve speeds faster than light? Does the math add up? is there even such a source? Please answer!

Alex_Ian_Hamilton

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Re: Black Holes?
« Reply #19 on: October 14, 2009, 01:25:36 AM »
Heya qwew80,

Well the reason that we can't travel faster than the speed of light is that as you (or any object with weight/mass) get faster, you get heavier (more heavy/massive), so it takes more energy to push you any faster. If you do that maths, then you end up requiring an infinite amount of energy to reach the speed of light.

Even if tachyons do exist, that doesn't mean that they could have infinite energy, so they couldn't help us get to the speed of light any more than any other form of energy.

I'm afraid there is no easy way past the speed of light for us :-(
But people are thinking of ways we might be able to get around it, like wormholes or warp drive; however so-far they are just theoretical and have no evidence of working yet.


monmarfori: yep, there'll be loads of new cool machines by 2020 (including the James Webb Space Telescope), so we'll be finding loads of things; but it's always going to be hard to spot dark things against the blackness of space.

fredetuc

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Re: Black Holes?
« Reply #20 on: April 04, 2016, 12:41:38 PM »
But we have found that worm holes exist just that it would be impossible to stabilize one so we could make it through without dying if that makes sense.

vh

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Re: Black Holes?
« Reply #21 on: April 07, 2016, 07:17:55 PM »
wormholes still don't let you break the speed of light

Physics_Hacker

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Re: Black Holes?
« Reply #22 on: June 11, 2016, 02:33:19 PM »
wormholes still don't let you break the speed of light

Technically they do, since you are travelling a distance instantly that would also be instant at 100% of the speed of light so if anything it's like becoming light--and is nothing like using warp drive where to get somewhere instantly you'd have to use an infinite warp factor, but wormholes are, as explained in lots of places, like folding a piece of paper to get to the other side instead of travelling the distance across it.

tesco

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Re: Black Holes?
« Reply #23 on: August 02, 2016, 04:14:41 AM »
wormholes still don't let you break the speed of light

Technically they do, since you are travelling a distance instantly that would also be instant at 100% of the speed of light so if anything it's like becoming light--and is nothing like using warp drive where to get somewhere instantly you'd have to use an infinite warp factor, but wormholes are, as explained in lots of places, like folding a piece of paper to get to the other side instead of travelling the distance across it.

Not really, wormholes bend spacetime right? So they bend it so you can go through at any kind of speed but you aren't going faster than the speed of light. You can travel huge distances quicker than light can travel there but you aren't going faster than the speed of light

Physics_Hacker

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Re: Black Holes?
« Reply #24 on: November 03, 2016, 06:36:45 PM »
wormholes still don't let you break the speed of light

Technically they do, since you are travelling a distance instantly that would also be instant at 100% of the speed of light so if anything it's like becoming light--and is nothing like using warp drive where to get somewhere instantly you'd have to use an infinite warp factor, but wormholes are, as explained in lots of places, like folding a piece of paper to get to the other side instead of travelling the distance across it.

Not really, wormholes bend spacetime right? So they bend it so you can go through at any kind of speed but you aren't going faster than the speed of light. You can travel huge distances quicker than light can travel there but you aren't going faster than the speed of light

That description is better suited to warp drive, wormholes fold spacetime and allow you to go through the gap through a higher dimension, and end up in the other part of the universe.

Sorry for the really, really late reply. I don't check this subforum much anymore.