Remember back in elementary or middle school, when your science teacher asked you to create a bizzare or alien creature? However, you weren’t allowed to just draw something random- you had to justify your creature’s characteristics scientifically. For instance, you could draw a creature with an extremely short height due to the strong force of gravity on its planet. You could give your creature the ability to do echolocation given that it was nocturnal.
I remember doing the exact same thing. To me, it was sort of fun. It was kinda like playing God; just like how God created us through evolution, I was creating my own animals also in a sense through evolution. However, in the end, what I really created was a picture of my creature. That’s all.
But now, imagine one day you can extend this science project and actually create a virtual world full of aliens. (Again, although it is science fiction, it is not total science fiction given that you have scientific explanations behind the creatures’ characteristics.) Suddenly, you really feel like god. The final result is not a piece of paper that you have to turn in, but a virtual world. To see what I mean, watch the docufiction below:
Pretty cool, right? And also pretty insightful too if a situation like this were to ever occur, such as robots acting all out by themselves without human guidance.
But notice the assumption that the planet we fall on is Earth-like. What I find confusing is that why do scientists assume that life on other planets is gonna be like life on Earth? For instance, a lot of documentaries show that in order for life to exist, there must be water. And what is the basis of that assumption? Well, life on earth. But we can’t just base it off one planet to determine how life on all other planets are going to be like.
In fact, the likelihood of life depending on something non-water has a much higher probability. So, just pointing out that we need to correct that mistake.
If you were to go into your regular high school physics class, and you were asked by your teacher what is gravity, your answer would most likely be that it is the force one mass asserts onto another, with the force being proportional to the masses. And if this question were on a test, you would have to better answer it this way, or else that’s one point off. This is Newton’s definition of gravity.
In my last post, I said that I would be showing why Newton’s definition of gravity is wrong. So one might ask, if it is wrong, then why do they even teach it? Well, my answer is that it is not entirely wrong. The calculations and formulas under Newton’s theory of gravity are actually pretty accurate most of the time, and thus we use them. But notice the phrase “most of the time;” that is because there are things that Newton’s gravity cannot account for.
One of them is Mercury’s orbit. Although Newton did not know it at his time, in the 19th century, when advanced telescopes had been made, it had been observed that there was a small discrepancy in its orbit. Under Newton’s theory, the only way to have explained this perturbation was that there was somehow a planet closer than Mercury to the Sun that existed. However, no planets have been or will ever be found that are closer to the Sun than Mercury. Therefore, something was wrong with Newton’s gravity in this case.
Another problem was the fact that black holes could suck in light. Light is made of photons, and photons have no mass. However, according to Newton’s theory, black holes could only assert a gravity onto another mass. However, photons again have no mass, so the fact that photons could still be sucked in is contradictory to Newton’s gravity.
Overall, another theory of gravity was needed. And that’s where Einstein’s theory of gravity came in, something that you don’t usually get taught about at high school. To explain Einstein’s theory, one must use an analogy. Suppose there is a blanket, that stretches across infinitely, with no limits and boundaries. Now, suppose I were to put a rock in the middle of this blanket. You would probably notice that this rock creates a depression in the blanket as seen below.
Now visualize this: suppose I were to fling a small marble into this depression. The ball would simply go round and round and round in the depression. Now if this were in the real world, the marble would eventually stop moving, due to friction and resistance. However, remember that this is space, in which there is no resistance whatsoever. So if it were in space, this marble would actually never stop, unless acted upon by something else.
With this in mind, suppose now that this big rock is the Sun and the little marble is Earth and this blanket is the fabric of space-time. Under Newton’s definition, the Earth is rotating because the thrust/tendency of the Earth to just speed away is counter-balanced by the force of the Sun’s gravity. Thus, it must stay in one orbit. However, under Einstein’s theory, the real reason why the Earth orbits the sun is because it is simply following this depression, or this curvature of space-time. In essence, gravity is the result of the geometry of space-time (as opposed to what Newton thought- that gravity was just this instantaneous force). The video below helps illustrate this concept:
This theory of Einstein does not totally reject all of Newton’s ideas, but rather explains it in a different way. For instance, let’s look at the case of elliptical orbits. Suppose there was a star and an orbiting planet. If we were to follow Newton, the reason such orbits occur is because at some points, the star’s gravity is stronger, pulling the planet more in, and at some points the star’s gravity is weaker, letting the planet be more far out. Thus, the end shape is an elliptical orbit. (In an ellipses, some parts are closer to the center than others. And if you don’t know what an ellipses is, it is pretty much an oval.) With Einstein, elliptical orbits were the result of the orbit of the object that is being orbited. Take the example of the Earth and Moon. We all know that the Earth orbits the Sun. So while the Earth is orbiting in this depression caused by the Sun, so is the Moon orbiting in this depression caused by the Earth. However, as the Earth is orbiting, the Moon has to move along with it while orbiting all at the same time. To see an illustration of this, go to time 0:29 in the the video above and play it. Notice that the depression of the Earth is constantly changing, due to it orbiting the Sun. Since the orbit of the Moon is based upon this depression, its orbit will not be perfectly circular, but rather elliptical.
Another example of how Einstein’s theory is just explaining gravity in a different way than Newton’s theory can be seen in mass. Newton said that the bigger the mass, the bigger the gravity, and he used a formula to show this. Einstein, on the other hand, showed that the reason this is true is because the bigger the mass of an object, the bigger and deeper the depression in this “blanket” of space-time, and thus it is more liable of things to fall into this depression, thus giving the impression that the object’s gravitational force is strong. It seems as if this object is pulling more things to it because of it’s bigger mass, when in reality it’s just that this depression is really big and deep so more objects are rolling around in this depression.
And speaking of strong gravity, let’s go back to the black hole I mentioned earlier. You have already seen that Newton’s theory doesn’t work here. Now I will show how Einstein’s theory works. First of all, black holes have gravity that is exceedingly high. Why is that? Well, just as I compared a Sun to a rock, compare the black hole to a bowling ball. Not only is it larger, but it is also much more heavier. The depression will be extremely deep; thus, anything that goes near this bowling ball aka black hole will have little chance of “bouncing” out of this depression, and will easily slide in given that the deep depression gives a steep incline for it to fall. In a sense, this depression is not a depression anymore but a super deep hole where it is very easy to fall into. All of this can explain the property of why so few things can escape a black hole.
If we look at black holes this way (in other words Einstein’s way), we can see that the fact photons have mass or not doesn’t matter. The photons will slide in no matter what into the black hole because they are simply rolling along the curvature caused by the black hole. That’s all. As you can see, this is much more efficient, given that Newton couldn’t have explained this using his theory.
I will conclude my post here. Of course, there are much more other things that can be examined, but I believe that I have covered at least the basics and in fact a little bit more. But I do hope that your mindset to physics has been broadened. Let me tell you, the physics out there can get more interesting than even this.
I stumbled onto this article, and I thought it did a pretty good job summarizing the theory of multiverses. This is just to open up your mind to the physics that is out there that goes way beyond the physics in your high school textbook. For my next post, I will focus on the “space-time” mentioned here and use it to explain that gravity is not necessarily the gravity you think it is (in other words, Newton’s definition of gravity is wrong).
Reblogged From NBC News:
The universe we live in may not be the only one out there. In fact, our universe could be just one of an infinite number of universes making up a “multiverse.” Though the concept may stretch credulity, there’s good physics behind it. And there’s not just one way to get to a multiverse — numerous physics theories independently point to such a conclusion. In fact, some experts think the existence of hidden universes is more likely than not. Here are the five most plausible scientific theories suggesting we live in a multiverse:
1. Infinite Universes Scientists can’t be sure what the shape of space-time is, but most likely, it’s flat (as opposed to spherical or even doughnut-shape) and stretches out infinitely. But if space-time goes on forever, then it must start repeating at some point, because there are a finite number of ways particles can be arranged in space and time.
So if you look far enough, you would encounter another version of you — in fact, infinite versions of you. Some of these twins will be doing exactly what you’re doing right now, while others will have worn a different sweater this morning, and still others will have made vastly different career and life choices.
Because the observable universe extends only as far as light has had a chance to get in the 13.7 billion years since the Big Bang (that would be 13.7 billion light-years), the space-time beyond that distance can be considered to be its own separate universe. In this way, a multitude of universes exists next to each other in a giant patchwork quilt of universes.
2. Bubble Universes In addition to the multiple universes created by infinitely extending space-time, other universes could arise from a theory called “eternal inflation.” Inflation is the notion that the universe expanded rapidly after the Big Bang, in effect inflating like a balloon. Eternal inflation, first proposed by Tufts University cosmologist Alexander Vilenkin, suggests that some pockets of space stop inflating, while other regions continue to inflate, thus giving rise to many isolated “bubble universes.”
Thus, our own universe, where inflation has ended, allowing stars and galaxies to form, is but a small bubble in a vast sea of space, some of which is still inflating, that contains many other bubbles like ours. And in some of these bubble universes, the laws of physics and fundamental constants might be different than in ours, making some universes strange places indeed.
3. Parallel Universes Another idea that arises from string theory is the notion of “braneworlds” — parallel universes that hover just out of reach of our own, proposed by Princeton University’s Paul Steinhardt and Neil Turok of the Perimeter Institute for Theoretical Physics in Ontario, Canada. The idea comes from the possibility of many more dimensions to our world than the three of space and one of time that we know. In addition to our own three-dimensional “brane” of space, other three-dimensional branes may float in a higher-dimensional space.
Columbia University physicist Brian Greene describes the idea as the notion that “our universe is one of potentially numerous ‘slabs’ floating in a higher-dimensional space, much like a slice of bread within a grander cosmic loaf,” in his book “The Hidden Reality” (Vintage Books, 2011).
A further wrinkle on this theory suggests these brane universes aren’t always parallel and out of reach. Sometimes, they might slam into each other, causing repeated Big Bangs that reset the universes over and over again.
4. Daughter Universes The theory of quantum mechanics, which reigns over the tiny world of subatomic particles, suggests another way multiple universes might arise. Quantum mechanics describes the world in terms of probabilities, rather than definite outcomes. And the mathematics of this theory might suggest that all possible outcomes of a situation do occur — in their own separate universes. For example, if you reach a crossroads where you can go right or left, the present universe gives rise to two daughter universes: one in which you go right, and one in which you go left.
“And in each universe, there’s a copy of you witnessing one or the other outcome, thinking — incorrectly — that your reality is the only reality,” Greene wrote in “The Hidden Reality.”
5. Mathematical Universes Scientists have debated whether mathematics is simply a useful tool for describing the universe, or whether math itself is the fundamental reality, and our observations of the universe are just imperfect perceptions of its true mathematical nature. If the latter is the case, then perhaps the particular mathematical structure that makes up our universe isn’t the only option, and in fact all possible mathematical structures exist as their own separate universes.
“A mathematical structure is something that you can describe in a way that’s completely independent of human baggage,” said Max Tegmark of MIT, who proposed this brain-twisting idea. “I really believe that there is this universe out there that can exist independently of me that would continue to exist even if there were no humans.”
Whatever Comes To Mind 