I thought some people might enjoy understanding a bit more about where we all live without the typical scientists annoying habit of making everything sound way more complicated than it really is. I’ll edit this post as and when (if anyone cares). Anything that can add or expand on this or correct a mistake is more than welcome.
First a few facts to try to convey the huge scope of our universe. Light moves at 186,000 miles per second and takes over 100,000 years to cross our galaxy. That should give you an idea of the size of some galaxies. There is on average, 1 supernova every century per galaxy and in the visible universe there are an average of six supernovae every second. That’s how big the universe is.
Einsteins general theory of relativity suggests that the universe must be in motion, which caused a huge divide in the scientific community between the steady state believers (who believed that although the universe is expanding, new matter is constantly being created in the gaps, making it eternal) and the motionists (can’t remember the word so I’ll make one up). Steven Hawking then proved steady state theory wrong by coming up with an equation for the big bang (that’s basically just the general relativity equations in reverse) that suggests the universe started life as a gravitational singularity (black hole), and with the help of the inflationary part of equation (inflation is needed to lock in the uniformity of the universe and keep it flat, but it‘s not known what caused it), it even accurately predicts the rough dispersion of matter throughout the universe (galaxies, galaxy groups and galaxy clusters). Religion, and the pope especially, jumped on the discovery as evidence of a creator. The pope even tried to tell him that it was okay to study everything after the big bang but not the big bang itself because that was the work of god.
Closed universe (spherical) - Positively curved (curves inward towards itself). A universe that is above the critical mass needed for the gravitational curvature of the universe to eventually collapse it back to whence it came. The shape of a closed universe is like the surface of the Earth. If your were to travel far enough in a “straight” line, you would eventually end up back were you started.
Open universe (saddle shaped) - Negatively curved (curves outward away from itself). A universe that is below the critical mass needed for it collapse. An open universe will eventually tare itself apart it in what’s known as the big rip. The dark energy in the universe (which makes up about 90% of the whole universe btw & out of the rest about 90% of matter is dark matter. To quote someone that I can’t remember “the bits we see are just the icing on the cake. It’s the parts we’re not aware of that really make up existence.”) will continue to accelerate the expansion of the universe out into infinity. Current observation suggests that our universe is open.
Flat universe (flatish) - Neutrally curved (still curves locally due to gravity but is flat overall). A universe that has a mass that’s EXACTLY the amount needed for it to keep a roughly uniform shape (not size) for ever. This universe dies with a whimper, over trillions of ions as everything slowly (relevantly slowly) gets further and farther apart. Our universe is extremely close to this, though it’s thought to be just over. In fact the odds of it being as close as it is (it needs to be that close for it to be stable enough for us to exist btw) are lots and lots (can’t remember how many) of trillions to one. This led to the entropic principle which says that the universe is the way it is because if it weren’t, we wouldn’t be here to ask, how come? I spose the uncertainly principle makes this universe impossible because it will have to go one way or the other eventually.
Determining which category our universe falls into involves measuring the current rate of expansion. The further away an object in the distant universe is, the faster it’s moving away from us. The speed is found by measuring the Doppler shift. If an object is moving away from us, the light waves get stretched making it appear red, and if it’s moving towards us, the waves get squashed making it appear blue.
If the Hawking equations are correct, it should be pointed out that even if closed, they disprove the theory of a bouncing universe. Besides even if it did bounce, the uncertainty principle, if completely true would mean that randomness is built into the universe, so you would get a different universe every time, unless the many worlds theory is correct in which case everything that can happen does happen and the uncertainty principle is simply about which direction you take. Depends how you interpret the uncertainty principle really. Some religious people have also used the uncertainty principle as evidence of room for god to manoeuvre. Although a closed, bouncing, deterministic universe does make a hell of a lot of sense. It would mean the three spatial dimensions would be spherical and so would time. If you were to travel far enough in any direction of space or time, you would end up where/when you started. For every action there is an equal and opposite reaction. If you move away from a point in space or time, you move an equal distance towards it in the opposite direction.
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The basic principle of relativity is simply that all the laws of physics must be independent of a coordinate system. Galileo formulated the original theory. He was on a ship and saw something pass and wondered if it was moving or whether it was the ship he was on that was moving. He then realised that if he ignored the land masses, there was absolutely no distinction between them. All movement is relative. This is the single most important concept in physics. Einstein later made it work in the special case of inertial (non-accelerating) bodies despite the discovery that energy always moves at the same speed regardless of the relative velocity of the observer. Ten years later he released a generalised version that incorporated acceleration/gravity. Every time something seemed to contradict the concept of relativity, it lead to a deeper understanding of it. I suspect the same will be true for quantum physics.Galilean Relativity - The theory of motion
The idea that there is no such thing as absolute rest.Galileos principle of relativity:
“The mechanical laws of physics are the same for every inertial observer. By observing the outcome of mechanical experiments, one cannot distinguish a state of rest from a state of constant velocity.”
The only way to infer, and therefore the only thing that defines velocity is a measurement of the relative motion of other bodies in relation to your position in space at the time. This means that time and space are not a fixed constructs and are in fact dynamic and completely dependent on the frame of reference of the observer.Special Relativity - The theory of the electromagnetic force
Special relativity adds in the knowledge that the speed of light is constant regardless the relative velocity of the source.Einsteins principle of special relativity:
“All of the laws of physics are the same for every inertial observer. By observing the outcome of any experiment (mechanical, electromagnetic, optical---or any physical law whatsoever), one cannot distinguish a state of rest from a state of constant velocity.”The pillars of special relativity:
1} - There is absolutely no such thing as non-relative velocity. The only thing that defines independent movement through space-time is acceleration.
2} - Energy always propagates at a constant velocity of c regardless of the relative velocity of the source.
If a ship were flying away from Earth and a signal was sent from Earth to the ship and from the ship to Earth, would both signals take the same amount of time to reach their destination? Yes, but both Earth and the ship would say no. Both observe outgoing signals taking longer than incoming signals because outgoing signals have to catch up to the receding destination. Outgoing signals have to travel further and take longer than incoming ones do to make the same journey, because outgoing signals are measured to when they arrive while incoming signals are measured from when they‘re released. So anything sent by us to the ship would seem to us to be travelling a shorter distance and wouldn’t take as long as a signal sent from the ship to us on Earth would to make the same journey. Incoming signals aren’t travelling as far (length contraction) or taking as long (time dilation) as outgoing signals are to travel between the two, because outgoing signals are always travelling to where an object is going to be and incoming signals are always travelling to where an object is.
There are two ships moving at different velocities. Both have an upright cylinder on top with a light moving up and down through it, and it takes one second for the light to travel up or down from one end of the cylinder to the other. Each would see the light on the other ship move in a zigzag as its relative velocity is added to its motion. Light doesn’t speed up to make up the difference, so it takes longer than one second for the light to get from one end of the cylinder to the other on the others ship. A second for either is a shorter amount of time than a second for the other so each sees the other moving in slow motion, because the light on the other ship has further to go. Now one travels though a tunnel to which the other ship is relatively stationary. The ships front end comes out one second after its back end enters, but space is length contracted from in the direction that it’s travelling in, making anything in the other frame including the tunnel length extended. Its front end emerges before the back end enters from the perspective of the ship at rest with the tunnel. From this frame, the ship is longer than the tunnel.
If you (A) flew away at half the speed of light while your twin (E) stayed on Earth then you would change your frames of reference relative to each other. You’re always stationery from your own perspective and light is always moving at the same velocity (c). Everything else is relative. From each of the perspectives, the other will be travelling at 0.5c but each sees themselves as travelling at 0c. A travels one light-year in two years, but a light-year has changed from As perspective relative to Bs because you’ve moved into a different frame where light speed is c relative two you despite your relatively different velocity. In the time it took for the light to get one light-years distance from Earth from Es perspective; it moved further from As, and the same is true from As perspective of E. So the distance the other covers from each perspective over any given unit of time wont seem like far enough. So if the distance that the other is covering decreases then the space and time separating them must decrease by an equal amount split evenly between the two (there’s one time and one spatial dimension as we’re moving in straight lines to keep things simple). So in both frames the value of the others space-time has lessened. So each view of the others time will appear to be in slow motion (time dilation) and in both views of the other there will appear to be less space (length contraction) along the one spatial dimension (“straight” line) that they are moving, thereby lengthening each ones perspective of anything in the others frame, which makes the perspective of any frame right relative to c. This effectively removes the discrepancy in the speed of light because it isn’t travelling as far and therefore as fast as in its own frame, bringing it right back to c relative to you.
Everything up until now has been symmetric, so each twin sees the same effects on the other, and in exactly the same way. The paradox is that when you return to Earth you’ll be younger than your twin. Both see the other moving in slow motion and through contracted space, which stops anything from moving faster than c relative to you. When you turn round you have to accelerate in the opposite direction (there’s no such thing as deceleration, it’s just acceleration in the opposite of some arbitrary direction) using the same amount of total energy you used to get up to this relative speed, right? Wrong! From Es frame you were burning fuel for a longer length of time than from your own perspective and it’s their reference frame that you return to, so it’s their perspective that will be right. So if you were to accelerate back in to you original frame then more time will have passed and your twin will be older than you, and you would have used the fuel over their worldline. What separated you was the fact that you accelerated and your twin didn’t. If E were to accelerate into As new frame then you’d be the same age again. Length contraction and time dilation would become lessen as your speeds become relatively closer to each other. When the relative velocities match, the only apparent time lag will be caused by how long it takes for light to cover the distance separating you (light hours/days/years).
You can travel as fast as you like because there's no speed limit because there's no such thing as absolute velocity. When you stop accelerating, you are in a new frame where you are now static from your own perspective and the energy requirement for acceleration relative to c is the same in every possible frame. If you accelerate again up to half light speed then you wont be travelling at the speed of light from your starting frame because you are length contracted/time dilated from the perspective of your previous frames and so you're moving slower through time and space. As you accelerate towards something, it gets closer to you beyond what you would expect from the increased velocity. You can move infinitely fast but as far as the rest of the universe is concerned you can't, and you'd have to pay for it if you wanted to return to your original frame.
At a constant acceleration of only 1g, using an antimatter engine (100% energy efficient) and assuming all locations are static and gravity free relative to us and each other:
Where - Nearest star
How far (in our frame) - 4.3 ly
Time to get there - 3.6 years
Fuel to get there - 10 kg
To stop (from half way) - 38kg
Where - Vega
How far (in our frame) - 27 ly
Time to get there - 6.6 years
Fuel to get there - 57 kg
To stop (from half way) - 886kg
Where - Galactic centre
How far (in our frame) - 30,000 ly
Time to get there - 20 years
Fuel to get there - 62 tonnes
To stop (from half way) - 955,000 tonnes
Where - Andromeda
How far (in our frame) - 2,000,000 ly
Time to get there - 28 years
Fuel to get there - 4,100 tonnes
To stop (from half way) - 4,200,000,000 tonnes
This is a bit misleading though as it takes into account the fact that the more fuel you carry, the more fuel is needed to accelerate the extra mass.
The easiest way to think in extra dimensions is to turn time into a spacial dimension. That's what the graphic above does. It's a three dimensional view of our universe. To describe the effects of special relativity we only need two. Imagine a circle. Now imagine an arrow pointing up and with it's base attached to the centre of the circle. The horizontal dimension represents space and vertical represents time. The arrows length represents its own time (proper time) in the same way that its width would represent its volume. Its overall path represents its world line. You are always static in space, so the arrow will always point directly up from its own perspective. If we add a second arrow representing an object moving at a relatively different velocity then it will be at an angle and therefore it's not covering as much time as the first arrow, and we can move the arrows so that the second arrow is pointing directly up and the first is time dilated. If it was to move at c then it would be at a right angle to your arrow and infinitely time dilated. That's why the dimensions are often said to be at right angles to each other. If one were to accelerate then that arrow would be curved from the others perspective, and the circle would be warped from it's own perspective, which is why gravity is the same as acceleration. It takes three times as much energy to return to your previous position in space-time as it does to leave it if we ignore fuel mass and keep the same rate of acceleration. We'll use instant acceleration to keep things simple although it's impossible because it would require infinite energy. We have two arrows on the circle but to start with they both point directly up because they are at rest relative to each other and in roughly the same place. One accelerates to .5c and so creates a 45 degree angle. It then accelerates in the opposite direction to become static again relative to the other. Now the two arrows are parallel. It then accelerates in the same direction again to move towards the other arrow. Finally it accelerates again in the opposite direction to stop right next to the original arrow. That's real movement. Both arrows now point directly up and share the same circle again but the accelerators world line has a skewed path through space-time covering more space and less time from this frame. Its arrow head is now behind the other arrow head so it's aged less, which is why the accelerator is always younger.
Let’s start again. You use one unit of energy to travel up to half the speed of light relative to Earth. Now you are static in you frame of course. Now let’s use another unit of energy to again reach half the speed of light from our new frame. From Earths frame that second unit of energy didn’t accelerate you as much as the first did, but from your perspective it did. The energy consumption of the accelerator increases from Earths perspective because of length contraction/time dilation. So if the same energy is needed to move over a relatively smaller amount of space-time, then the mass of the accelerator has increased from Earths frame, and visa versa of course but Earth isn’t going to accelerate. So because each others energy requirement to move over the same distance increases as your relative difference in velocity increases; your mass increases the faster you move relative to something else. Energy becomes mass as you accelerate relative to the speed of light from perspective of Earth or anything else. That’s how matter and energy are interchangeable, E=mc2.
Now we’ll apply special relativity to the electromagnetic force. Imagine two equally spaced rows of electrons in a wire, one positive and one negative. The positive electrons are moving along the wire at .5c which creates a magnetic force. Now if we accelerate to the frame of the positive electrons we need to length contract the negative ones that at now moving at .5c in the opposite direction relative to this frame, making them closer together. We also need to length extend the positive ones that are now static, making them further apart. So the positive electrons are now more spaced out than they were before and the negative electrons are closer to each other than before, so there are more negative electrons than positive electrons in this frame. So the wire now has a negative charge. So the magnetism from the previous frame is felt here as electricity. Both are just relativistic effects on electrons.
That’s the special theory of relativity and that’s how light seems to always move at the same speed. If you want to travel in the forth dimension then you just need to accelerate. That only describes relative motion though, and there’s still something missing because gravitational waves also travel at the speed of light. We need a more general theory of relativity that includes the effects of gravity.General Relativity - The theory of the gravitational force
The effect of gravity is indistinguishable from a state of constant acceleration, and disappears entirely in any frame of reference that is in freefall.Einsteins principle of general relativity:
“All experiments will give the same results in a local frame of reference in free fall and in a local frame of reference far removed from gravitational influences.”Einsteins equivalence principle:
“... we shall therefore assume the complete physical equivalence of a gravitational field and the corresponding acceleration of the reference frame. This assumption extends the principle of relativity to the case of uniformly accelerated motion of the reference frame.”Einsteins principle of curved space-time:
“If all accelerated systems are equivalent, then Euclidean (flat) geometry cannot hold in all of them.”The pillars of general relativity:
1} - There is absolutely no physical difference between the effect of being in freefall and that of being completely free of all gravitational influences.
2} - There is absolutely no physical difference between the effect of non-freefall gravity and that of constant acceleration.
If you’re in a plane in freefall and you shone a laser from one end to the other you would see the light move in a straight line since freefall is equivalent to constant velocity. Someone on Earth would see the light move across the plane with the downward motion of falling as well. The light will be following a curved path from their perspective despite the fact that light always moves in a straight line. This is because gravitational pull is the equivalent to acceleration. So it distorts space-time, in this case through length contraction. So the beam takes longer to move from one end of the plane to the other from the fame of the accelerator on Earth because its downwards motion means it has further to go, and it can’t move faster to cover the extra distance because it always moves at c. This means the frame on Earth see the people in freefall as moving quicker though time, because Earths frame is accelerating, causing gravitational time dilation.
Downwards momentum in freefall is caused by unchallenged length contraction. That's why objects fall at the same rate regardless of their weight. Gravity is length contraction and dime dilation, and we have to accelerate away from the source to avoid collapse, which we do through the fact that matter doesn’t share the same space (strong nuclear force), and it’s upwards acceleration that pulls us down. What we feel as our weight is actually due to the fact that when we are not in freefall, we are constantly accelerating up at one g relative to a static freefall frame. Time dilation and length contraction stop us from going anywhere. Gravity can’t be felt if it's distributed evenly throughout the observer. What we feel is really just the upwards acceleration of the strong nuclear force of the atoms resisting length contraction. When we accelerate, we feel a force pushing in the opposite direction. In the case of gravity, we experience this as a downward pull. We can’t actually feel gravity because it’s always zero relative to us. We could feel it if the difference in gravity where different enough in one part of our body to another part. A small enough singularity causes what’s known as spaghettification. It’s not the gravity (velocity) you feel, it’s the relative difference in its strength (acceleration). On Earth that difference is very small but it’s enough to determine the direction of gravity.
Imagine a very tall building in freefall. It’s so tall that height and time on the top floors are noticeably different to the lower floors. Gravity strength is inversely proportional to the square of the distance to the mass. In zero dimensions (point) it’s infinite (singularity). In one spatial dimension (straight line) its strength would remain constant regardless of distance. In two dimensions (flat plane) it would be directly proportional to the distance. And in three the strength is divided by four if the distance is doubled and multiplied by four if the distance is halved. It’s always proportional to the volume it fills. The rate of decent is determined by the difference in the gravitational field (how sharp the curve is), not its strength. That how objects know which way to fall. The bottom of the building is in a stronger gravitational field and accelerating faster than the top, but the building always remains a constant height. The reason why this works is because the acceleration rate is measured by time moving at different speeds. Anyone on the top floors would see the bottom ones as too short and moving too slowly through time, while those on bottom floors would see the top ones as too tall and moving too quickly through time.
At the big bang, the 4 forces (electromagnetic, weak nuclear, strong nuclear and gravity) were combined as one super force. This is known as super symmetry. Something happened to gravity to make it hugely weaker when they separated. A small magnet can overpower the gravitational attraction of the entire Earth. String theory attempts to bridge the gap between particle physics and general relativity (they seem to contradict each other) and explain the apparent weakness of gravity. Basically it says that there are between 9 and 11 dimensions, some higher, some lower, and gravity seems weaker than the other forces from our perspective because it’s being spread throughout the other dimensions. It also may explain the uncertainty principle as unknown variables from lower dimensions.
Time is not how we perceive it. It’s like that question so many people ask: "What was there before the big bang"? There was no before the big bang! What we perceive as time (and space), started at the big bang, because the three spatial dimensions and the one time dimension were all condensed to a singularity. Someone in higher dimensional space (if it exists) would see our universe as static, and they would have their own dimension that they perceive as time. Our universe has no beginning or end as such, because we will always have had been here, so to someone outside of our four dimensional universe, we would be eternal.
Gravity is a curvature of the four dimensions (called space-time). Imagine a birds eye view of a two dimensional surface. Now imagine that surface has some give. If you were to put an object on the surface, it would warp the fabric, but from your two dimensional perspective, you wouldn’t be able to see this directly. It would still look flat even with a square grid pattern on the fabric. The heavier the object, the more it would distort the fabric, and if it was too heavy, it would tear a hole in it. Now if you were to roll a marble across it, it would curve around the object (the heavier the object, the sharper the curve) in the centre and fall towards it. Objects in orbit aren’t curling through space because that’s impossible. Instead they’re moving in a straight line through curved space-time. It doesn’t look curved to us because we only have a three dimensional view.
Black holes are what happens when there’s gravity, with nothing to provide a resisting force against it. The nuclear forces of all the atoms on the Earth stop it collapsing for example. Stars have a lot of mass, so need nuclear fusion to hold them up. When a stars fuel runs out, it either forms a white dwarf held up by itself, a neutron star held up by an electromagnetic field, or for the biggest stars, black holes held up by nothing. The gravitational curve inside the event horizon of a black hole is so strong that it curves space back in on itself. No matter which direction you try to go, you will always be facing the singularity at the centre. Time alters relative to gravity in a similar way to velocity. The stronger the gravitation field, the slower time moves within it. At the singularity, time is frozen.
Gravity may be the weakest force by a long, long way, but there can be a lot of it and it has a huge range, unlike the nuclear forces. Remember, when you try to leave Earths orbit, you have to first overpower the gravitational attraction of all the mass on the planet. Think how much everything on the surface weighs, than remember that it’s solid, so times that by a huge number. It’s a miracle we’re not squished. The strength of gravity is directly proportional to the mass of the object and inversely proportional to the square of the distance to that object. That just means that, if you halve the distance, the strength of the gravitational wave is multiplied by four/if you double the distance, the strength is divided by four.
Black holes are all the same size (kind of); infinitely small. The area of effect is just the gravitational waves created by the singularity, determined by its mass. The event horizon, which is generally regarded as the edge, is the point of no return, where space curves back into itself. This helps explain the fact that although something can be by our standards non-existent (the universe before the big bang), a singularity can have vastly different values (as low as a mini black hole or as high as the universe). That’s how a universe can arise from "nothing".
There are three types of black hole. If quantum theory is right then there’s mini black holes, which scientists at CERN are going to try to create http://www.doom3world.org/phpbb2/viewtopic.php?f=8&t=21527
, stellar black holes formed from the cores of massive stars and super massive black holes that form in the centre of spiral galaxies like our Galaxy, the Milky way, and Andromeda, our nearest neighbour. They’re the engines that power the galaxies and make them spin. Everything orbits around the centre of gravity in the same way as a star system. The Milky Way even has two dwarf galaxies orbiting it like moons. The universe doesn’t have a centre or an edge because it’s not a three dimensional object. Everywhere is in the centre from its own perspective.
The Milky Way and Andromeda are by far the biggest galaxies in our local group, which has about fifty. All the galaxies obit the centre of gravity between the big two because heavier objects fall inwards relative to the others because of their stronger pull. Galaxy clusters are made up of lots of groups. The Milky Way and Andromeda are on a collision course and will merge in about 3.5 billion years. The Milky Way’s big, and Andromeda’s about twice the size, so when they merge it will easily be the biggest galaxy in this part of the universe. The radiation during this time will be detectable all the way on the other side of the universe. We can see quasars, which are bright early galaxies, all the way on the other side. They’re from the early universe because the light has taken so long to get here.
When - Fusion occurs when a protostars fiction creates enough heat to overpower the weak nuclear force of the hydrogen atoms that it’s made of. The central part of the nebula generates more frictional heat because of the centrifugal law. When an object is spinning, the central part will need to move faster to have the same amount of energy, because it hasn’t got as far to go, so will have to spin faster to move at the same speed. Nebulae are kick started into motion when the gravitational waves of an exploding/imploding star pass through them. It was proven that our solar system was started by the death of a very close star when local meteorites were found to have elements inside, of the same age as the solar system, and that can only be formed in super nova.
How - When a star becomes nuclear, it pulls in a lot of the nearby gas and throws some into orbit creating a disc shape. The gravity of the orbiting debris isn’t strong enough at this point to create planets but it creates an electromagnetic field through the friction of collisions. This process is called accretion. Dust particles accrete into dust balls and rain drops accrete around dust particles in the air for example. When they reach the size of a mountain, gravity has an effect, pulling in more matter which causes the gravity to increase, which pulls in more matter, and so on. Most planets don’t survive. The Moon was a Mars size planet that crashed into Earth. Some of it makes up the planets crust and the rest is the Moon. Without the tight centre of gravity that we both orbit created by the Moons proximity, we would be all over the place with no defined seasons and a chaotic climate. The distance from the Sun determines the temperature of the forming planet which determines what the planet will be made of. Heavier elements fall into the middle, with the lighter ones at the edge. Mercury is highly dense and metallic, Venus, Earth and Mars and the asteroid belt are made of rock, then the gas giants, and the Kuiper belt at the edge, made from ice (including Pluto) that was forced out from where it was formed. All the water on the planet comes from impacts from these types of comets. Water couldn’t have condensed here because Earth is inside the frost line, which is between the asteroid belt and Jupiter, where it’s too hot for hydrogen and oxygen to form ice.
Why - When a protostar starts fusing hydrogen into helium, energy is realised ((Energy = Mass * light speed squared) E=mc2) because one helium atom weighs slightly less than two hydrogen atoms and the remainder of the mass is realised as energy in the form of heat, light and other radiation carried across the solar system by the solar wind. A lot of what the Sun throws out is deadly, but we’re protected by the Earths magnetic field that’s generated by the molten metallic core. This can be seen as northern and southern lights at the magnetic poles. It’s thought that Mars once had water and maybe life. It’s about half the size of Earth and around a third of the mass. The core didn’t have as much heat and it solidified. Mars lost it’s force field and was scorched by solar radiation, killing the planet.
The fundamental uncertainty in measuring the position and momentum/velocity of a particle are inversely proportional. So if you measured exactly how fast a particle is going, you'd have no idea where it was. This isn't just an uncertainty of the experimental apparatus that you might be able to get around with a bigger budget and more time for instance, it's the inherent uncertainty in nature itself. This is an incredibly cool idea and completely turned on it's head the physics community's hidden assumption ever since Newton came up with classical mechanics that the universe is completely deterministic. Mind you, there are still a few physicists out there (like Gerard t'Hooft) that still think the universe should be completely deterministic and try to come up with theories that are. Btw there is proper experimental evidence that the universe is inherently fuzzy and doesn't contain 'hidden variables' (ie you may think maybe if you completely measure the velocity of a particle it really is in one particular position and for some reason the laws of nature prevent us from seeing this and it looks fuzzy to us).
The uncertainty principal is really just a consequence of the axioms of quantum mechanics, where the fuzziness really lies. One of the most famous experiments that really highlight quantum mechanics and why we need it is the double slit experiment. Say you shine some light on two very fine slits, because light can be thought of as a wave, the light diffracts around the slits and creates a diffraction pattern, much like waves on a beach will bend around corners and stuff. Now scientists also tried this experiment with a beam of electrons and to their great surprise the electron beam, which was thought to be made out of particles also created a diffraction pattern. This was really weird so the scientists turned the electron beam down so only 1 electron would pass through the double slits every second or something so the electrons couldn't influence eachother. They still got a diffraction pattern, which meant the electron was somehow diffracting with 'itself' which meant it was somehow going through both slits at the same time. Now the diffraction pattern looked a bit different from the ones you get from sounds waves for instance because when the electrons hit the wall after the slits they were detected as single particles. It's the buildup of lots of the electrons that showed the diffraction pattern, which suggested the electrons had some sort of 'probability wave' that gets diffracted. It's hard to really explain in words, pictures are a lot better. The scientists also discovered if they put a detector on one of the slits so they could tell which slit the electron went through they stopped getting a diffraction pattern and the electron beam acted like a normal beam of particles. So this basically meant the actual measurement of the electrons somehow influenced whether they'd look like a wave or a particle.
This basically lead to Schrodinger's wave formulation of quantum mechanics where subatomic particles can be thought of as wave functions which describe the probability of measuring that particle in different points in space. So instead of a particle being in a definite place, it's in a 'superposition' of places at any one time. If you measure where a particle is, it's wave function will 'collapse' to become a smaller one. Schrodinger's Cat is a little thought experiment by the physicist so expand upon this premise by imagining a Cat being in a superposition of several states, some being alive and some being dead. The problem with this thought experiment is that it wouldn't work, the box and air molecules themselves would interact with the molecules of the cat and 'measure' what is happening so the cat's wave function would collapse. But it is a good way of illustrating the philosophical conundrums quantum mechanics brings up.
Evolution is extremely simple. In a universe that’s 14 billion years old and currently 100s of billions (American billions) of light years across and getting so much bigger every second that it boggles the mind, it’s not a huge leap to think that somewhere by shear fluke something (amino acid) would interact with its surroundings in way that by pure chance would create something else that is nearly an exact copy of it. Now, if it’s an nearly an exact copy then it too has the capacity to absorb the matter of its surrounding to create a copy of itself. Now evolution kicks in. What if it creates 100 copies and 50 of those can utilise photosynthesis to extend their life spans. They will have more offspring than the others, meaning the next generation will be better at using their surroundings than the previous one was, and so on, until you us.
The origin of life and the odds of it happening are still not entirely known. The building block are contained in comets, but at attempts to artificially trigger life have never succeeded, although amino acids have been artificially produced. Some people have suggested that a lightning strike is the probable trigger, and inconclusive evidence has been produced to support the idea.
To find out how common life/intelligent life is, we need to know:
What percentage of star systems are stable enough for life to form on one of it’s planets or moons?
Answer: Very few systems are as stable as ours (thanks to Jupiter being big enough to gravitationally attract asteroids and comets, but not big enough to disturb the other planets orbits. Also if Saturn had been bigger we would have been in trouble, because two Jupiter sized planet would create very unstable gravitational conditions). However, a system doesn’t have to be as stable as ours to support life.
What percentage of planets that can support life, actually do support life?
What percentage of planets that support life are stable enough and are in systems that are stable enough for complex life to form?
Answer: Probably a relatively low number. We’re very lucky that Jupiter is here and isn’t too small or too big, and that Saturn isn’t any bigger. We’re also very lucky that Thea hit the Earth and created the moon out of some of the rubble to give us a stable axis.
In what percentage of life forms is being intelligent a major advantage?
Answer: As far as we know, 33.3r%. A mass extinction caused by a meteorite lead to the rise of the dinosaurs, who existed for a very long time whilst being really stupid and not getting any cleverer. Then another meteorite lead to the rise of mammals with opposable thumbs. Suddenly a creature could manipulate it’s environment in a way never before possible. Suddenly intelligence became a huge advantage, and there’s no stopping natural selection/survival of the fittest/evolution.
…Or God did it.