Welcome Digital Thinkers

Check out some of our most recent since lessons through our science sections; PhysicsChemistry and Biology.

Or go to a some of our most recent pages such as;

The cycle of life

Electromagnetic Spectrum

Features of a wave

Motion

Forces

Momentum

Electrostatics

Nuclear Power!

The Zeroth law of Thermodynamics

 

 

The zeroth law is one of the weirdest laws I think I've ever come across at this point in my physics career because it's so simple! So simple that I doubted making a page for this law but when I thought about it harder I realised that this law is so crucial that it had to be included!

 

The zeroth law goes as followed;

 

If you had two objects, let's say a nail and a piece of cake, the cake has just come out the oven so its relative temperature is hotter than the nail. Basic science and common sense have told us that the heat will transfer from the hotter object to the colder object. So heat will transfer from the cake to the nail. Then they will come to a point when no more heat is being exchanged and the objects have a thermal equilibrium.

 

 

Thermal equilibrium: When there is no net heat exchange between 2 objects

 

 

Then you take the nail off the cake and place it in water. This is rarely the case but let's say the nail and the water have the same relative temperature so they are already in thermal equilibrium. So now we know that the nail is the same temperature as the cake and the water. So now will the water and the cake be at thermal equilibrium?

 

 

THE ANSWER IS YES!

 

It's all just common sense! If the nail was, say, 20 degrees then the cake and the water will also be 20 degrees since they have the same relative temperature making them all equal.

This is the easiest law ever to comprehend but it is one of the most important.

 

 

Why is it so important then??

 

 

Well if this law didn't hold we would have to measure every different object with a different scale. Such as a nail to cake heat comparison would be different to a nail/ water comparison.

 

THIS LAW IS NEEDED FOR A RELATIVE TEMPERATURE MEASUREMENT THAT WORKS FOR ALL OBJECTS IN OUR UNIVERSE!

 

This law is how Celsius, Fahrenheit and Kelvin work because we can base the relative heat of objects to a common scale and that's why it is so important to the world.


So why is it called the zeroth law if it's so important??

 

Well, physicists had been working on the first law of thermodynamics for years and years and after they perfected it, they realised how fundamental the universal heat measurement was to the law. They had to put it before the 1st law but since it was the 1st law they had to make it the 0th law.

The life cycle of stars

 

Stars are massive fireballs that glitter throughout the universe in different shapes and sizes. It is very uncommon to come across similar stars as they can range from 450x smaller to over 1000x larger than our sun. A star's mass is measured in the unit solar mass with I solar mass being the mass of our sun. Stars can range from a twelfth of a solar mass to over 50 solar masses. The colours of stars are determined by their temperature with blue being the hottest to red being the coolest. Size has a similar correlation to temperature as the bigger the star is the cooler it gets. The energy that provides these temperatures are from nuclear fusion contained in the core of the star. This brightness is measured in magnitude, the brighter the star the less magnitude it has.

 

The origin of the stars

 

 

Stars are born in regions with high densities of gas called Nebula. When there is enough gas to form a gravitational attraction the gas contracts under its own gravity.
This region of condensing gas will begin to violently heat and start glowing to form a Protostar. At this stage, the protostars gravity is stronger than the repelling forces acting against it which will cause the gas to start reacting and fusing. The temperatures can get to around 15 millions degrees celsius and this is enough heat for the nuclear fusion to being within the star.
When the fusion between the hydrogen and helium begins huge amounts of energy are released. This energy repels the gravitational attraction until a state of equilibrium is achieved, this is when both forces are equal so no movement occurs. When this state of equilibrium is achieved, depending on the mass of the star, it will stay in the state for billions of years. Stars with a larger mass are bigger than other stars so their gravitational attraction is stronger, therefore to keep the equilibrium the hydrogen and helium are consumed faster.
These reactions allow heavier elements to be made in the core, this includes beryllium, lithium, boron etc. up to iron in the periodic table. Only smaller stars with a higher temperature and longer lifespan make it up to iron. These elements cause fusion to slow down and makes the temperature of the star drop and the outer layers to float away causing the star to appear larger also known as a red giant. When all the helium runs out the smaller star's outer layers completely drift away from the core and the core a white dwarf.

 

Bigger stars

 

 

Bigger stars do mostly the same as what I have mentioned above, however there death is quicker and more spontaneous. The large mass in the core means that when the fusion stops the gravity contracts the star again. this takes less than a second and the resulting implosion is called a supernova. A supernova is a shock wave of the imploding core that sends all the outer layers away causing a spectacular image to occur in the universe. If the core of the star survived the explosion it will contract further to become a neutron star. A neutron star is mainly a star of neutrons, with some protons, and it is one of the densest objects in the universe. However, the alternative state of the core is even denser as it becomes a black hole. A black hole is said to have infinite density. The gravitational field is so strong that even light can't escape its attraction and so we can barely detect them giving the name black hole.


The next page will be on black holes so you can learn about them in more detail.

Fundamental forces

 

 

Currently there are 4 fundamental forces that we know of in the universe. Gravity, electromagnetism, the weak nuclear force and the strong nuclear force. These forces combine everything in the universe and without one of these forces all existing matter would rapidly change. If you would like to know about spins and colors that will come up in the articles check out my previous page.

 

The strong force

 

The strong nuclear force is the force that holds the nuclei of atoms together against the enormous force of repulsion from the protons. However, the strong force only stays strong at very short distances and the further out two particles go the weaker the force gets. The actual fundamental particle that is said to hold the quarks together in this force is called the gluon. The gluon is a massless particle that carries no normal charge. These gluons are said to be a product of the residual color force of the coloured quarks. Gluons are sort of like rubber bands that loop around the different quarks and keep them all together. The strong force is 1000000000000000000000000000000000000000 (10 with 38 zeros after it) x stronger than gravity.

 

 

Weak force

 

The weak force is responsible for the decay of nuclei. In a proton there are two up quarks and one down quarks. When an up quark flips to become a down quark the whole composition of the particle changes and it becomes a neutron and vice versa. This is caused by the weak force. So, a true definition of this force is it changes the flavour of the quarks. However, up and down quarks have different electron-volts of energy so if one switches the leftover energy has to be transferred into something. The is the physics of conservation. So when a quark flips the left over electron-volt energy get converted into an electron and an electron neutrino. In radioactive decay, when an atom stabilises it releases beta particles while converting a neutron to a proton. This beta particle is a fast moving electron and is the most basic observation of the weak force at work. The weak force particles are W and Z bosons that have a large mass, therefore making them slow and weak. Like the strong force, the weak force gets weaker the further away the particles are so it can only work on very small distances. The weak force is 100000000000000000000000000 (10 with 25 zeros) x stronger than gravity.

 

 

Electromagnetism

 

The electromagnetic force acts on anything with an electric charge. This force creates the properties for electrostatic charges, opposites attract and like repel. An example of electromagnetism on the atomic scale is the atom. The electrons (negative charge) orbiting the nucleus that has positively charged protons attract therefore keeping the electrons from flying off into space. The electromagnetic force seems to not get weaker the further apart the acting objects are so, like gravity, it could have infinite size. The particle that is used with the electromagnetic force is the photon aka. light. They have no mass and no charge and can exchange infinitely as just discussed. The main theory of electromagnetism is quantum electrodynamics. The electromagnetic force is 10000000000000000000000000000000000000 ( 10 with 36 zeros after it) x stronger than gravity.

 

 

Gravity

 

Gravity is the weakest force out of the ones that I listed above, yet it acts over the longest distances? Unlike the weak and strong forces, gravity has infinite distance at which it can act. A real life example of how weak gravity is is something you can do right now. Firstly, if you jump you have beaten the attraction of gravity for a few seconds, however, if you tried to pick a proton out of your hand it wouldn't go so well, even if you have a high-powered microscope and a scalpel. This is because gravity is the only force that gets stronger with a greater amount of binding agent in this case mass. As gravity is stronger with the more mass you add, we humans don't account for 1% of the mass of the earth so we have a weak gravitational attraction. Therefore when we jump, the earth doesn't attract towards us as much as we attract towards it. So we can break the gravitational attraction by using enough energy to break it for a few seconds. The more energy you have the easier it is to break gravity. However, because of human limitations rockets can only carry so much, so most of the ship is fuel to get enough energy to break the atmosphere. Gravity is supposedly maintained by the graviton particles but none have been detected in experiments so it is still yet to say what is behind gravity.

 

 

So gravity is infinite then why isn't the electromagnetic force keeping us in orbit around the sun?

 

As I explain earlier, the more mass you add the stronger the force becomes but with the electro-mag force the more positive and negative charges you add the more they will attract and eventually cancel out to produce no charge. So that is why gravity dominates the planets because there is more mass in the universe than charge.