But what about Centrifugal force?!
Okay so there is such a thing as gravity kind of. Hold with me a minute. What we think of as gravity is actually not just a force pulling us towards the centre of the earth. What it actually is is acceleration. Acceleration through space time to be precise. Okay maybe I should go back a bit.
Often we talk about space and time as separate things however Einstein’s theory of relativity models the universe as a giant, incomprehensible ball of 4 dimensional “Space-Time.” Gravity is basically warped space time which we are falling through. To help visualise this imagine an insect crawling along a ball in only 2 dimensions. If you press down the ball then the insect will walk into the area without noticing that you have warped the dimensions of the ball. In the same way we cannot see space-time being warped, we can only feel its effects. The effect we feel is gravity.
But then how come objects with large mass produce stronger gravity? Well it turns out mass is what warps space time. The larger an objects mass, the more space time is warped and so the stronger its gravitational pull.
On another slightly related note centrifugal force doesn’t exist either. It is actually a force of inertia. Objects at a constant velocity want to stay at a constant velocity so for instance when you’re in a car and the car turns a corner you move to the side because your body wants to keep traveling in the same direction you were traveling before hand. This gives the illusion of centrifugal force. Next they’ll be telling us that mass could appear out of nowhere! (Spoilers: It can*)
In the last post I talked about how the sun is fueled by hydrogen atoms colliding so hard that they fuse together and form helium. What I neglected to mention is that this should be impossible. Even at the sun’s huge temperature’s of about 15 million degrees protons are still travelling too slowly to actually fuse together. How then is it possible for this nuclear fusion to happen?
Well it all comes down to one of the main principles of Quantum Physics: The Heisenberg Uncertainty Principle. This principle states that it is impossible to know both the location and the velocity of a particle simultaneously with any degree of certainty. In other words, the more you know about where an atom is the less you know about it’s speed and vice-versa.
In the sun the protons of hydrogen are localised in space: i.e. their location is precisely known. This means their velocity must be highly uncertain - and therefore could be high enough for the protons to have enough energy to tunnel into eachother and fuse together.
This revolutionary discovery was done by Fritz Houtermans and Robert Atkinson. The night after discovering this Houterman tried to impress his girlfriend with the rather original line: “I must be the only person in the world who truly knows why the stars shine.” Two years later they got married.
Okay so you are probably all aware that the sun is a burning ball of fuel where hydrogen atoms are battered into each other at high enough speeds to fuse their protons into one nucleus - creating helium.
What’s really interesting though is that the sun stays together because of the gravity of its own mass, but this force alone would cause it to collapse into a black hole. The only thing keeping it from that is the fuel being burned and pushing outwards. This keeps the sun - and other stars - in a constant state of balance.
Of course this means when it runs out of fuel it begins to collapse. This turns the star into a white dwarf (I will cover why in another post). A white dwarf is incredibly dense and one spoonful of it would way the equivalent of a car. Once this can no longer be maintained the star collapses again into a neutron star - which is so dense that one spoonful weighs more than the entire human race. After this the star eventually just fizzles out.
Of course sometimes the star doesn’t turn into a neutron star and instead actually does collapse into a fully fledged black hole. There is also a possibility that if a white dwarf gains enough material from other stellar object then it could become a Supernova - a star that expands and briefly shines as bright as whole galaxies. This can also happen when a particularly large star runs out of fuel, in which case it’s gravitational potential energy released can expel the star’s outer layers.
“A rainbow in the east will be followed by a fine morrow, in the west by a wet day.” - Weather Proverb
Rainbows are a spectacular display of colour and light that everyone can appreciate, whether they are fully formed rainbows in the sky, or a mini rainbow reflected on top of a puddle. However most people only realise that rainbows require sunlight and water to form.
The more complex explanation follows up from Rayleigh scattering, mentioned in the last post. While it is true light is absorbed and then scattered by gas in the atmosphere light acts slightly differently on water. The light is either reflected or refracted by the water droplets. However, different wavelengths of light are reflected/refracted by different amounts. This displays the whole spectrum of light separately; forming a rainbow.
However we don’t always see a rainbow when it is sunny and raining. This is because raindrops are circular and, as such, their reflection pattern is circular. The closer the sun is to the horizon the more of the reflected light we can see, however if it is more than 42 degrees above the horizon then no rainbow is visible.
So there you have it. If you want to see a rainbow, wait until it’s sunny and raining, wait for sunset and then face the horizon.
Or Red for that matter?
When I was younger I remember asking my parents why the sky was blue. They said it was because it reflected the light from the ocean as the ocean made up the largest portion of the earth’s surface area. I later guessed this probably wasn’t true, and was delighted when I found out the real reason.
What happens is that molecules of air actually reflect certain wavelengths of light. The longer wavelengths of red and some of the green spectrum can pass through as they are too large; however because blue light has a shorter wavelength it is reflected more, making the sky appear blue during the day. This is called Rayleigh scattering.
Of course during the sunset the sky actually seems red. This is because the blue light is still being scattered except now the sun is close to eye level so it is being scattered away from your eyes only letting the red light pass through and reaching your eyes directly.
So there you go, not reflecting the ocean after all. Just certain wavelengths of light.
When is a planet not a planet?
As some of you may know our beloved Pluto has been demoted. It is no longer one of the planets in our solar system, thereby messing up all the mnemonics that we had to learn in primary school. It has instead been classified as a dwarf planet or planetoid due to its tiny size. But surely it was okay before as a planet, so why did they change it?
Well for a start it turns out that Pluto isn’t even the largest dwarf planet in the solar system, that award goes to Eris which has been found to lie way out on the very fringes of our solar system. The main reason though lies just slightly beyond pluto.
It turns out that beyond pluto is an area of space called the Kuiper Belt, which is filled with thousands of huge objects - mostly similar to asteroids. Among these objects are Pluto and three other dwarf planets. This discovery made it seem a bit silly to continue to classify pluto as a planet and so it was reclassified as a dwarf planet to help with the classification of possible future objects found in the Kuiper Belt and, even further out than that, the Scattered Disc.
Remember before observing this blog it is both annoying AND pretentious.
Quantum mechanics is one of the most important ideas in Physics. It has allowed us as a species to invent, among other things, computers, lasers and nuclear reactors. However, unless you’ve studied it most people have never had Quantum Physics even slightly explained to them. So with that in mind I am going to attempt to remedy that.
It all starts with Schrodinger’s cat. Imagine you put a cat in a sealed box and this box was connected to a button which when pressed has a 50/50 chance of killing the cat*. Now usually you would think after pressing that button the cat would have to be dead or alive however quantum theory says this is not the case. Before being observed in some way (e.g. Shaking the box and hearing cat whines; opening the box; or shooting the box - thereby confirming the cats death) the cat is both dead and alive!
This idea of something being two things at once is the fundamental principal behind quantum physics. It is from that idea that everything else stems. When applied to the world of atoms, in particular light, it is used to explain why sometimes light acts like a particle and sometimes a wave. This wave/particle duality seems to be true for all particles and although it is impossible to imagine this means that particles can do all number of seemingly impossible feats, such as being in two places at once.
While Quantum Theory is clearly much more complex than this, this is the underlying principles behind it. I will try to explain it further in later posts however I hope it has helped shed some light on the confusing and impossible world of quantum physics.
*In the actual explanation it’s a machine linked to a radioactive source but who cares.
Hello. My name’s Matt and I’m writing this blog in the hope of entertaining and informing anyone with an interest in science. Not the hardcore scientists who know the difference between different types of leptons or have memorised the entire periodic table. No, this is for people with a casual interest in science but are really much more interested in finding out how things work or reading mildly interesting facts while procrastinating on tumblr. So please enjoy, or not, I’m a scientist I don’t need friends…