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Restore mangroves to save Sundarbans. Now that will certainly get you a speeding ticket on the freeway. Just how small can we make an object and how high can we push up the escape velocity?
If we make the object smaller in size than the neutron star but having the same mass, similar to the Sun's , the surface gravity will get bigger and bigger, until The velocity gets up so high that the escape velocity reaches the highest possible speed - the speed of light. Figure 5. Albert Einstein - the fellow with the messy hair who gave us the two theories of relativity. His hair probably had nothing to do with it, but who knows? Now a lot of people have really weird ideas about what black holes are and how they act.
Don't believe it - they aren't that bizarre. To understand black holes and how they interact with the rest of the Universe, we need to understand some of the rules that are in effect around them, how they influence things gravity related stuff and how light operates. These are explained in some of Albert Einstein's theories.
Now don't panic - these aren't all that bad, and I'll just go over the basics so that you understand what is going on with them. First we'll look at the easier of the two theories - the Special Theory of Relativity. I'm not joking about this one being easier - it really is. That is not the most important part of the theory; it's not even a major component.
The main feature of the theory can be stated in the following concept - the speed of light is a constant no matter what is going on, no matter what you are doing, and there is nothing I really mean nothing that can travel faster than the speed of light.
Now, we already ran over the first part of this when we talked about the properties of light - and actually without that concept the rest of the Special Theory of Relativity wouldn't exist. The second part is sort of like a cosmic speed limit. Nothing goes faster than the speed of light, not even when the cops aren't looking. You might not think that these rules are a big deal, but if you relate it to how things move on the Earth, then it is a big deal.
Figure 6. An example of non-relativistic low velocity motion. Here is an example of what I mean. Let's say you have a truck going down the road at 60 mph. In the back of the truck is an overpaid NFL quarterback. He can throw a football with a speed of about 40 mph. Let's say that the truck is going the same direction that he is throwing. Just how fast will the football be moving when it is caught ignoring the effects of wind resistance and such?
You basically add up the velocities, so the football would be going at a speed of mph. I would not want to be on the receiving end of the toss in this case. The example illustrated above is pretty straightforward - you just add up the velocities if they are going in the same direction.
What if the quarterback is throwing in the direction opposite of the direction that the truck is going? Then you would subtract the velocities. This is what happens to things going at non-relativistic speeds speeds much less than the speed of light.
Let's do another experiment, but this time in space. Let's say in the spaceship is an alien with a laser beam, which is basically just an intense flashlight. Let's say that the alien aims the light in the same direction that the spacecraft is moving. Now let's say we have a detector aimed at the spaceship and the laser, and this detector is measuring the speed of the light coming from the laser.
How fast would the light be traveling as we measure it? If you went by the football-throwing example above, you might think that we would measure a speed of 1. Unfortunately, that isn't correct. What does the special theory of relativity say? It doesn't matter if the ship is coming toward us or going away from us; we'd always measure the same speed for the light. Figure 7. An example of relativistic velocities. Unlike the example shown in Figure 6, you can't just add the velocities together, based upon Einstein's Special Theory of relativity.
Isn't that just weird? No, we don't lose it, because we can't gain it in the first place. Light is just a rather strange thing. No matter what you do, you can't get a velocity for light greater than c. Don't feel disappointed, because even though we don't get the expected result of adding velocities, we get some other nifty stuff happening.
If we were outside of the spaceship watching it go by, and we were to measure the length of the spaceship, we would measure a different length than would be measured by someone in the spaceship or if the spaceship were not moving. If we were to measure the mass of the spaceship from our location, it would be different than if we were in the spaceship or if the spaceship were not moving. If we were to look inside the spaceship at its clocks, we would think they were broken since they would be going at a different rate than clocks not on the spaceship.
This is sort of a way that the Special Theory of Relativity makes up for the fact that you don't get the addition of velocities like in the previous example. This also sort of explains why we call it the Special Theory of Relativity - what you measure depends upon your situation relative to the thing you're measuring.
If you were on the spaceship and you were measuring things that aren't moving along with you stuff outside the spaceship for example , you would measure very bizarre things, sort of like the same way someone who isn't moving would be getting strange measurements for the characteristics of your spaceship. You could be moving or the spaceship could be moving - it doesn't matter; the high velocity screws up measurable quantities like length, color, mass, time, etc. The higher the velocity the closer to the speed of light , the more screwed up the measurements.
Now you are probably thinking that I have to be making all of this stuff up, right? This stuff can't really be happening, can it? Does time really pass more slowly on a fast moving rocket compared to the passage of time on the Earth? Actually, this does happen - and people have checked it out.
If you were to put a clock on the space shuttle and let it go around the Earth for a few days, it would not keep time as well as a clock that stayed on the Earth. Even though the space shuttle doesn't go anywhere near the speed of light, it does go fast enough that the effect can be measured on very accurate clocks.
These things have been measured - people have put clocks on jets and checked them out. Also, when particles like electrons are accelerated in physics labs, their masses appear to change.
This isn't science fiction - this stuff does happen. For the Special Theory of Relativity, just remember, only light goes at the speed of light, it always goes at the speed of light, and if an object goes faster and faster, its characteristics as we measure them will appear to be bizarre. If someone were on an object that is moving very fast, they would think that our characteristics or that of anything not on the fast moving object were screwed up - it's all relative.
Believe it or not, that was the easy theory - now it is time to tackle the much more complex General Theory of Relativity. Actually it won't be so bad, since we're skipping all of the math that goes with the general theory - that's what makes it really nasty.
Let's start off with what the General Theory of Relativity does - it picks up where Newton's theory of gravity left off. I'll bet you didn't think that the law of gravity needed any picking up. For the most part it doesn't - the law of gravity as Newton formulated it works just fine for most things. It is in situations where it doesn't work well that Einstein's formula needs to pick up the slack. How does the General Theory do that?
It sort of re-defines gravity. You might think of gravity as a kind of rubber band or a glue that makes things stick together have you ever thought about what actually makes you stick to the surface of the Earth? Einstein's General Theory re-did gravity by looking at how space and time are distorted by mass.
Also, if you have distorted space, then the way that mass travels through it will be effected. Basically, mass distorts space, and space effects mass and anything else within it, like light. Wait a second, what is this I am talking about? Is distorting space like warping space? It is!
How do you distort space? You are familiar with three dimensional space. Any location can be referenced by three coordinates - you can call them x, y, and z, or perhaps latitude, longitude and elevation.
No matter how you do it, any location in the Universe can be designated by three dimensional coordinates. Space is three dimensional. Let's distort it - warp it, bend it, and stretch it like silly putty. When space gets distorted, it gets warped into another dimension that we can't see. Let's call this the fourth dimension - this is a dimension of space; it isn't time, that's something else.
Where is this fourth dimension? I don't know; I can't show you where it is since we humans are only able to exist in and visually comprehend three-dimensional space. You can't point to it, since you can only point in 3-D space, but it is does exist. Let's see if we can simply things. Think how a flat surface a two-dimensional surface can get warped in such a way that it bends into a third spatial dimension.
That's how you can have a flat tortilla two-dimensional object curved up to form a three-dimensional object a taco. If we were tiny two-dimensional creatures living on a tortilla, and we were only aware of two dimensions we could only experience our world in two dimensions , we would not be able to see that the tortilla has been curved into a third dimension, since our senses wouldn't be able to perceive three dimensions.
Even if we could "see" the three dimensions of the taco shell, we would be so small compared to the curvature that it would be difficult to detect. This is similar to why you can't easily see that the Earth is a sphere, but that it looks fairly flat to your eyes after all, we are in Iowa. Going back to your Universe, three-dimensional creatures, like you, me and Einstein, can't see the fourth dimension that space is being distorted into.
No matter how badly distorted the space near you is, you can never actually see its curvature. It is also difficult to draw four-dimensional space - frankly, we can't do it. In order to describe warped space we like to simplify things and just use two-dimensional analogies, which we can warp into three dimensions. Figure 8.
A 2-D analogy to warped 3-D space. The top view is undistorted 2-D space. The two lines red and blue are straight, and objects moving on them will travel the same distance. Placing a mass in this space middle picture causes the space to distort around the mass. The larger the mass, the greater the distortion. The red and blue paths are now no longer equal in length.
The blue path is slightly longer. In the last case, the distortion is very extreme due to a very massive compact object. Now the differences in the lengths between the red and blue lines are very extreme. It is even possible that the blue path has no end but continues down the hole, never ending.
Let's start out with a 2-D universe which doesn't have any distortion, so that it is flat - pretty dull and boring, eh? The rules of General Relativity say that if we were to add some mass to this space, it would get distorted - more mass, more distortion. Let's do that. Here's the nifty stuff - far away from the mass you do not detect any distortion. The space is just as flat as if you didn't have any mass.
As you get closer to the mass, you will experience unusual effects due to the warping of space. Let's say you have two ants in a race in this 2-D universe. They are going to race across the space and travel along straight lines. One will be traveling closer to the mass than the other one will be along the red line, the other along the blue line in Figure 8. How does the race end? The ant that traveled near the mass had to actually travel along a greater path, since that ant's space was distorted.
He lost the race. The weird thing is that he didn't even know that his path was distorted - being a 2-D creature, he could not see the curvature and the line looked straight and normal to him. If the ant had a flashlight and what well equipped ant doesn't have a flashlight?
Light, like the ant, must travel in the space that comprises this universe, so it will travel along what is really a curved path. Even though light travels in a curved path, it will always appear to be straight as seen by the inhabitants of the space.
If you really want to see major distortions you'll need to add a large amount of mass. You could also concentrate the mass into a really small space - make it very dense. This is such a strange concept, this warping space stuff, that it might be hard to believe.
Believe it or not, any mass will distort space - you are distorting space, the computer is distorting space, the building you are in is distorting space, and even your nose is distorting space not a great deal, but it is still distorting space. This sounds like a bunch of science fiction; does this stuff really happen?
To test this out, you need to have a large mass. The largest mass object in our neighborhood is the Sun, and we know that it distorts space. One way that this is apparent is in the way that Mercury's orbit about the Sun is gradually altered orbital precession is the term.
When Mercury gets really close to the Sun when it is at perihelion , it is in slightly distorted space. Its orbit is shifted a little bit. Over the years this alteration to the orbit of Mercury was noticed by astronomers. Newton's laws and Kepler's laws could not explain this apparent aberration in the motion of Mercury, and this caused some people to suspect that there was another planet close to the Sun that was messing up Mercury's orbit.
This isn't actually the case, but that didn't stop people from trying to find the mythical planet Vulcan yes, they really did refer to it as Vulcan. Of course, when Einstein came along with his General Relativity, this pretty much explained the problem with Mercury. Figure 9. The way that the space around the Sun is warped. In the top image there is no warped space.
In this case, the stars located behind the Sun could not be seen on the Earth, since the light from these stars will never reach the Earth. This is not the case, however. The lower image shows how the space actually alters the path of light, so that the stars are visible from the Earth. However, since we can't "see" the warped space, we think the stars are actually in the wrong positions the dark blue spots.
The positions of the stars that are lined up with the Sun appear to be off their proper locations by a small amount, due to their light traveling along warped paths. Is that not enough for you? Here's another instance. Let's say that you have some light traveling near the Sun light which came from other stars. The space near the Sun is distorted, so the path that the starlight takes will be influenced by this distortion. This was demonstrated soon after Einstein published his theory by astronomers viewing the Sun during a total eclipse.
During the eclipse, the locations of stars around the Sun were noted and compared to their normal locations. The star locations were off slightly due to the distortion of space near the Sun. Of course, when we see these stars during an eclipse, we presume they are in the direction in the sky that we see them in, in other words, straight away from us.
But those direction are the wrong directions for the star's true location. If space were not distorted by mass, we would always see the stars in their normal locations and Einstein would probably have never gotten that really cushy job at Princeton. The General Theory of Relatively relates the masses of objects to the effect they have on space. An object like the Sun has measureable effects as described and tested many, many times above, but the Earth also warps space.
A probe studied the effect of the warping of space by the Earth recently provided evidence that supports the theory. You can learn about the probe and its measurements here. Einstein's General Theory helped to fill in the gaps that Newton's law of gravity couldn't cover, especially the cases involving extreme masses.
It can also be thought of as a way to actually cause gravity. The Earth orbits the Sun due to gravity, right? What if you consider the fact that the Sun is warping space and the planets move in that warped space in the only way they can, like a marble rolling around the inside of a bowl? Near the Sun the "bowl" is steeper, so the orbits are smaller and the planets have to move faster so they don't fall in. Further away, the "bowl" is less steep, so the planets don't have to move so fast.
Newton's and Kepler's laws can describe the motion, but Einstein's curved space can give us the cause of it. Whether this helps you in understanding gravity or not is up to you; I'm just telling you how it works. I should also mention that one of the other aspects of the General Theory of Relativity is what it does to time - yes, you got it, time passes more slowly near massive objects than it does further away from them.
It's another victim of curved space! That's enough wandering down the confusing path that Einstein gave us - let's get back to black holes. What can become a black hole? The only ingredient that you need is mass, so anything with mass could become a black hole.
This includes stuff like the Earth, a pencil, John Goodman and so forth. The only reason that these things don't normally become black holes is that you have to make them dense enough compact in size so that their escape velocities are equal to the speed of light.
To do that to the Earth you have to crush it down to a size of less than a centimeter. I suppose a chocolate eclair could push John Goodman over the edge, but I could be mistaken. That's one characteristic of a black hole - it has mass.
Does it have anything else? How about size or shape? Technically it can't have any size, since if it did have a size, that would mean it isn't entirely collapsed down to a black hole. That's sort of a confusing argument, but if you don't think about it too much, it does make sense.
For something to become a black hole it must collapse down to such a small size that it can't hold itself up, so it has no size. This means that the mass has to be crushed down to an infinitely small point - a singularity , which has no size but does have a measurable mass.
If a black hole didn't collapse down to a singularity, then there must be something preventing the collapse - but there is no known force that can overcome the huge gravitational collapse that we run into in these extreme conditions. Black holes have no measurable radii, but do have measurable masses. Of course, if an object has mass, then it has a gravitational pull on anything around it.
Now contrary to what you may think, black holes are not magical vacuum cleaners that travel though the Universe sucking everything in sight down their gullets.
They have to obey the laws of physics just like everything else in the Universe, so you can determine how much gravitational pull a black hole has on objects near it.
For objects further away, the gravitational pull is much less just like it is for anything in the Universe. At large distances there would be no problem in escaping from a black hole, so if you ever do run across one in your travels, don't go in for a closer look - you need to stay far away, where the gravitational pull is low. As you'll see, if you do get too close, there will be nothing to save you. A black hole has to obey the laws of physics, so there is that rule about escape velocity - the speed needed to escape from an object - that you have to watch out for.
If you are too close to an object, you need to travel at a very great speed to escape. If you start out at a point further away, the velocity you need to escape is much less. In the case of the black hole you can use this to define a "boundary" for the black hole. Researchers predicted that such collisions would occur, but did not know how often.
The observations could mean that some ideas of how stars and galaxies form may need to be revised. When we assume something we tend to be proved wrong after a while. So we have to keep our minds open and see what the Universe is telling us. Black holes are astronomical objects that have such strong gravity, not even light can escape.
Neutron stars are dead stars that are incredibly dense. A teaspoonful of material from a neutron star is estimated to weigh around four billion tonnes. Both objects are cosmological monsters, but black holes are considerably more massive than neutron stars.
In the first collision, which was detected on 5 January , a black hole six-and-a-half times the mass of our Sun crashed into a neutron star that was 1. In the second collision, picked up just 10 days later, a black hole of 10 solar masses merged with a neutron star of two solar masses. When objects as massive as these collide they create ripples in the fabric of space called gravitational waves.
And it is these ripples that the researchers have detected. The researchers looked back at earlier observations with fresh eyes and many of them are likely to to have been similar mismatched collisions. Researchers have detected two black holes colliding , as well as two neutron stars but this is the first time they have detected a neutron star crashing into a black hole.
So apart from completing the set, why does this latest collision matter? It is because, according to current theories and past observations, neutron stars tend to be found with - and collide into - other neutron stars.
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