Science and Astronomy Questions 
huishb  Date: Tuesday, 08.12.2015, 02:55  Message # 391 
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 Ahh ok! Thanks guys for the feedback. But I thought you could because because of the post from SpaceEngineer:[img]http://http://en.spaceengine.org/_fr/30/8864533.jpg[/img] You can see the universe collapse in on itself due to immense gravitational lensing and the awesome strong red/blue Doppler effect and below you the darkness is engulfing you. I thought if the black hole was supermassive, the gravity is more spread out so you could cross the event horizon. And if it was a smaller black hole, It would seem that you never pass the event horizon (which you would have long before you realize it has been crossed.)
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Edited by huishb  Tuesday, 08.12.2015, 04:57 

 

Watsisname  Date: Tuesday, 08.12.2015, 04:40  Message # 392 
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 I think that's the view you would get when holding stationary with respect to the hole. It's not what you would see if you enter the black hole in freefall, not firing your engines.


 

huishb  Date: Tuesday, 08.12.2015, 05:02  Message # 393 
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 Quote Watsisname ( ) I think that's the view you would get when holding stationary with respect to the hole. It's not what you would see if you enter the black hole in freefall, not firing your engines.
oh well, i meant like using the arrow keys in camera mode not with spacecraft. I think maybe you guys got confused.
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AeroWolf  Date: Saturday, 19.12.2015, 18:13  Message # 394 
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 Sorry if this question has already been answered but how does gravitational lending work?
If we travel to the edge of the universe, could we touch it?
Is infinity a very very big number?
How heavy is the universe?
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Salvo  Date: Saturday, 19.12.2015, 18:52  Message # 395 
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 Quote AeroWolf ( ) how does gravitational lending work? You mean gravitational lensing? It's basically a phenomena that happens when an object has a very strong gravitational field, so strong that it can noticeably change photons' movement. Photons who travel near this object changes its trajectory, and so we have that distortion effect!
Example
Quote AeroWolf ( ) If we travel to the edge of the universe, could we touch it?
No. Ignoring the fact that you can't reach it, even if you travel at the speed of light, there is a problem... there is no edge at all. For comparison, it's like keep going forward on the surface of the earth hoping to reach the end, but there is no end.
It's a bit complicated and the example of "moving on the earth" is probably not the best one out there. Anyway, since there is no "center", there is no "edge", you just have to forgot the image of the universe as a "bubble".
Quote AeroWolf ( ) Is infinity a very very big number?
Mathematically speaking, yes, in reallife it's a number so big that it can not be quantified, so it's infinity.
Quote AeroWolf ( ) How heavy is the universe?
Approximately 3.2*10^54 kg, but it's just an assumption and we actually know very little about the universe to have a pretty acceptable measure.
The universe is not required to be in perfect harmony with human ambition.
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(still don't know why everyone is doing this...)
Edited by Salvo  Saturday, 19.12.2015, 18:56 

 

JackDole  Date: Saturday, 19.12.2015, 19:07  Message # 396 
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 There are I think the theory that if you touch on the back of your head, you touch the end of the universe.
Don't forget to look here.


 

HarbingerDawn  Date: Saturday, 19.12.2015, 19:34  Message # 397 
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 Infinity is not a number.
All forum users, please read this! My SE mods and addons Phenom II X6 1090T 3.2 GHz, 16 GB DDR3 RAM, GTX 970 3584 MB VRAM


 

Watsisname  Date: Saturday, 19.12.2015, 23:22  Message # 398 
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 Yeah, infinity is not a number. Any number times zero is zero. But what is ∞*0? Do you think it is zero? Do you think it is infinity?
If infinity were a number then I could calculate ∞*0 and always get the same numerical answer. But this is not true. ∞*0 is an indeterminate form. That means I can do this calculation in myriad different ways and get all sorts of different answers. I can make it equal to zero, or I can make it equal to infinity. I can even make it equal to 7. :)
Quote AeroWolf ( ) how does gravitational lending work?
Think of light as moving always in perfectly straight lines through spacetime, but the spacetime is warped by gravity, which makes those lines appear curved. This makes light bend around massive objects  the more massive they are, the more the light is bent. Near a black hole, light can even be bent all the way around it to make a closed loop!
Quote AeroWolf ( ) If we travel to the edge of the universe, could we touch it?
There is no "hard edge" to the universe. There is the "observable edge", beyond which we cannot see because the universe is only so old and so light has only had so much time to reach us. But if you could instantly travel to that "edge", you would find that there is more space, with more galaxies, and it'd look pretty much the same (on large scales) as the universe does here. You would seem to be at the center of a universe filled with galaxies, no matter where you actually are.
Quote Salvo ( ) Approximately 3.2*10^54 kg, but it's just an assumption and we actually know very little about the universe to have a pretty acceptable measure.
This is about the correct number, but I think it is better than a mere assumption. It is a calculation based on knowing (by observations) that the large scale curvature of the universe is extremely close to flat, calculating (by general relativity) what the mass density must be in order to make it flat, and then multiplying that figure by the volume of the observable universe.
Most of this mass is not in the form of "normal matter", like protons, neutrons, electrons, etc, but "dark matter" and "dark energy", the precise nature of which being still fairly unknown.


 

Salvo  Date: Sunday, 20.12.2015, 14:17  Message # 399 
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 Quote HarbingerDawn ( ) Infinity is not a number. My math teacher taught us the opposite, but we were talking about limits, I may have misunderstood her.
The universe is not required to be in perfect harmony with human ambition.
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(still don't know why everyone is doing this...)


 

midtskogen  Date: Sunday, 20.12.2015, 17:17  Message # 400 
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 Quote Salvo ( ) My math teacher taught us the opposite, but we were talking about limits, I may have misunderstood her. A simple argument to demonstrate the absurdity of treating infinity as a number  in the sense a natural or real number: if infinity is a number, then infinity + 1 must be a number as well, and infinity * infinity, and infinity ^ infinity, and so on.
NIL DIFFICILE VOLENTI


 

Alek  Date: Sunday, 20.12.2015, 22:20  Message # 401 
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 Quote midtskogen ( ) if infinity is a number, then infinity + 1 must be a number as well, and infinity * infinity, and infinity ^ infinity, and so on.
All of those are valid, but they all equal infinity also.
Living among the stars, I find my way. I grow in strength through knowledge of the space I occupy, until I become the ruler of my own interstellar empire of sorts. Though The world was made for the day, I was made for the night, and thus, the universe itself is within my destiny.


 

Watsisname  Date: Monday, 21.12.2015, 00:01  Message # 402 
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 Quote Salvo ( ) My math teacher taught us the opposite, but we were talking about limits, I may have misunderstood her.
It's possible; limits and infinities can be a confusing subject. See if this helps:
When a limit is "equal to infinity", what we really mean is that the limit diverges, which is a particular way in which a limit might not exist.
For example, if we consider the limit as x approaches 0 (let's say from the right) of f(x)=1/x, and you say this limit exists and is a number L, then I can choose values of x sufficiently close to 0 such that the values of f(x) are greater than L. Indeed, no matter how large of an L you choose, I can always find f(x) which are larger than L for x that are closer to 0. This contradicts the definition of the limit, so this limit doesn't exist. Rather than values of f(x) converging to a number "L" as x approaches some value "a", the values of f(x) grow without bound. "Positive infinity" is just a way of describing this behavior.


 

midtskogen  Date: Monday, 21.12.2015, 06:59  Message # 403 
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 To add confusion, 0.999... is a real number and it equals 1.
NIL DIFFICILE VOLENTI


 

pzampella  Date: Monday, 21.12.2015, 14:43  Message # 404 
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 So, if we think of Earth as a sphere and that is infinity in 2D, then can we think of the Universe as a hypersphere and that is infinity in 3D?


 

Watsisname  Date: Monday, 21.12.2015, 17:43  Message # 405 
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 Quote midtskogen ( ) To add confusion, 0.999... is a real number and it equals 1.
An easy thing to show. 1/3 = 0.3 repeating. Multiply both sides of the equation by 3.
Alternatively, the method employed by one of my calculus professors, was to throw a marker at the wall in the back of the room directly above a sleeping student's head. Then he asks the class, "Did the marker hit the wall?" Yes. "How do you know?" *laughter at the formerly sleeping student's surprise and befuddlement* "But can't I say it only traveled 9/10 of the way there, and then another 9/10 of what remained, and then another 9/10, and so on?" ...yes. "But it did hit the wall?" Yes. "Interesting."
Quote pzampella ( ) So, if we think of Earth as a sphere and that is infinity in 2D, then can we think of the Universe as a hypersphere and that is infinity in 3D?
Is the Earth an infinity in 2D? How large is its surface area?


 