Physics

States of matter

by Lawrence Henry

There are many different states of matter. In this article I will explain some of them.

Common states of matter

1.solid. In a solid, atoms and molecules are close together. They fixed in place and cannot move, but they vibrate.

Examples: ice, most metals

2.liquid. In a liquid, atoms and molecules can move, but they stay close together. This means that liquids can flow.

Examples: water, mercury

3.gas. In a gas, atoms and molecules are quite far apart and can move. This means that gases can flow and be compressed.

Examples: steam, air

4.plasma. A plasma is similar to a gas, but it has so much energy that electrons leave their atoms. This means that plasma can flow, be compressed and conduct electricity.

Examples: lightning, stars

(some) rare states of matter

1.bose-einstein condensate. At 0 K (-273 C) atoms and molecules stop vibrating, and quantum laws can apply on a macroscopic scale.

2.superfluid. A superfluid is a fluid that can flow without friction. Supersolids also exist. They can move without friction but they retain their shape.

3.quark-gluon plasma. At extremely high temperatures and/or densities (such as the universe just after the big bang), quarks are no longer confined by the strong interaction, and they can move around.

4.neutron degenerate matter. This is found in neutron stars. It is made up of neutrons at an extremely high density.

Particles

By Lawrence Henry 8B

There are many types of particles. Some make up matter and antimatter, while others control fundamental interactions. I will list some types of particle.

Matter and antimatter

1.quarks and antiquarks. They make up protons and neutrons and their antiparticles. There are 6 types of quark. They are: up, down, charm, strange, top, bottom. All other types of quark quickly decay into up and down quarks. Quarks are always found in pairs or threes.

2.electrons and positrons. Electrons have a negative charge. They are often bonded to atomic nuclei. They are a type of lepton. Electrons allow atoms to bond, which lets molecules form. Electrons are essential to many physical phenomena, such as electricity and magnetism. Positrons are their antiparticles.

3.protons and antiprotons. Protons have a positive charge. They are composed of 2 up quarks and 1 down quark. At least 1 proton is found in every atomic nucleus. The number of protons in an atomic nucleus is a defining property of elements.

4.neutrons and antineutrons. Neutrons have a neutral charge. They are composed of 1 up quark and 2 down quarks. Neutrons are found in all atomic nuclei except hydrogen-1 and a few extremely unstable isotopes of other elements. The number of neutrons in an atomic nucleus defines the isotope of that atom.

5.neutrinos and antineutrinos. Neutrinos are similar to electrons, but they have a neutral charge. They only interact with other particles through the weak interaction and gravity.

Interactions

1. W & Z bosons. These carry the weak nuclear force responsible for radioactive decay. The W boson can be positively or negatively charged, while the Z boson has a neutral charge. The W & Z bosons all have mass.

2. gluons. These carry the strong nuclear force between quarks. The strong force holds quarks together to create hadrons such as protons and neutrons. Gluons have no mass.

3. photons. These carry the electromagnetic force responsible for magnetism, electricity and light. Photons have no mass, so they always travel at the speed of light.

Light is made of photons.

Time Travel - Is It Really Possible?

By Marcus Kaniewski 8S

*Disclaimer: This article was put together by many websites and some of this I do not claim to be my own work as this is a very complex subject to understand however this is an interesting topic so I thought I would put something together.

The question we all ask ourselves: Is time travel really possible? In this article you are about to find out the truth about what's possible and what's not, please remember some of this is speculation as we don’t know a huge amount about time travel. I do caution you that if you do not understand that much about science then you do not read this as it is an incredibly complex subject.

So What Actually Is It?

Time travel is the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person, typically with the use of a hypothetical device known as a time machine. Time travel is a widely recognized concept in philosophy and fiction. The idea of a time machine was popularized by H. G. Wells' 1895 novel The Time Machine. It is uncertain if time travel to the past is physically possible. Forward time travel, outside the usual sense of the perception of time, is an extensively observed phenomenon and well-understood within the framework of special relativity and general relativity. However, making one body advance or delay more than a few milliseconds compared to another body is not feasible with current technology. As for backward time travel, it is possible to find solutions in general relativity that allow for it, such as a rotating black hole. Traveling to an arbitrary point in spacetime has a very limited support in theoretical physics, and usually is connected only with quantum mechanics or wormholes, also known as Einstein-Rosen bridges.

How Could It Work?

Some theories, most notably special and general relativity, suggest that suitable geometries of spacetime or specific types of motion in space might allow time travel into the past and future if these geometries or motions were possible. In technical papers, physicists discuss the possibility of closed timelike curves, which are world lines that form closed loops in spacetime, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe spacetimes which contain closed timelike curves, such as Gödel spacetime, but the physical plausibility of these solutions is uncertain. Many in the scientific community believe that backward time travel is highly unlikely. Any theory that would allow time travel would introduce potential problems of causality. The classic example of a problem involving causality is the "grandfather paradox": what if one were to go back in time and kill one's own grandfather before one's father was conceived? Some physicists, such as Novikov and Deutsch, suggested that these sorts of temporal paradoxes can be avoided through the Novikov self-consistency principle or to a variation of the many-worlds interpretation with interacting worlds. Time travel to the past is theoretically possible in certain general relativity spacetime geometries that permit traveling faster than the speed of light, such as cosmic strings, transversable wormholes, and Alcubierre drive.The theory of general relativity does suggest a scientific basis for the possibility of backward time travel in certain unusual scenarios, although arguments from semiclassical gravity suggest that when quantum effects are incorporated into general relativity, these loopholes may be closed. These semiclassical arguments led Stephen Hawking to formulate the chronology protection conjecture, suggesting that the fundamental laws of nature prevent time travel, but physicists cannot come to a definite judgment on the issue without a theory of quantum gravity to join quantum mechanics and general relativity into a completely unified theory.

What Are Wormholes?

Wormholes are a hypothetical warped spacetime which are permitted by the Einstein field equations of general relativity. A proposed time-travel machine using a traversable wormhole would hypothetically work in the following way: One end of the wormhole is accelerated to some significant fraction of the speed of light, perhaps with some advanced propulsion system, and then brought back to the point of origin. Alternatively, another way is to take one entrance of the wormhole and move it to within the gravitational field of an object that has higher gravity than the other entrance, and then return it to a position near the other entrance. For both these methods, time dilation causes the end of the wormhole that has been moved to have aged less, or become "younger", than the stationary end as seen by an external observer; however, time connects differently through the wormhole than outside it, so that synchronized clocks at either end of the wormhole will always remain synchronized as seen by an observer passing through the wormhole, no matter how the two ends move around.This means that an observer entering the "younger" end would exit the "older" end at a time when it was the same age as the "younger" end, effectively going back in time as seen by an observer from the outside. One significant limitation of such a time machine is that it is only possible to go as far back in time as the initial creation of the machine; in essence, it is more of a path through time than it is a device that itself moves through time, and it would not allow the technology itself to be moved backward in time. According to current theories on the nature of wormholes, construction of a traversable wormhole would require the existence of a substance with negative energy, often referred to as "exotic matter". More technically, the wormhole spacetime requires a distribution of energy that violates various energy conditions, such as the null energy condition along with the weak, strong, and dominant energy conditions. However, it is known that quantum effects can lead to small measurable violations of the null energy condition, and many physicists believe that the required negative energy may actually be possible due to the Casimir effect in quantum physics. Although early calculations suggested a very large amount of negative energy would be required, later calculations showed that the amount of negative energy can be made arbitrarily small. In 1993, Matt Visser argued that the two mouths of a wormhole with such an induced clock difference could not be brought together without inducing quantum field and gravitational effects that would either make the wormhole collapse or the two mouths repel each other. Because of this, the two mouths could not be brought close enough for causality violation to take place. However, in a 1997 paper, Visser hypothesized that a complex "Roman ring" (named after Tom Roman) configuration of an N number of wormholes arranged in a symmetric polygon could still act as a time machine, although he concludes that this is more likely a flaw in classical quantum gravity theory rather than proof that causality violation is possible. Another approach involves a dense spinning cylinder usually referred to as a Tipler cylinder, a GR solution discovered by Willem Jacob van Stockum in 1936 and Kornel Lanczos in 1924, but not recognized as allowing closed timelike curves until an analysis by Frank Tipler in 1974. If a cylinder is infinitely long and spins fast enough about its long axis, then a spaceship flying around the cylinder on a spiral path could travel back in time (or forward, depending on the direction of its spiral). However, the density and speed required is so great that ordinary matter is not strong enough to construct it. A similar device might be built from a cosmic string, but none are known to exist, and it does not seem to be possible to create a new cosmic string. Physicist Ronald Mallett is attempting to recreate the conditions of a rotating black hole with ring lasers, in order to bend spacetime and allow for time travel.

Overall it is hard to say whether time travel is possible or not, in theory it does and in practise it doesn’t, it’s one of those things that are hard to get your head around and you could spend days on end reading about it. I hope you have learned something from reading this and if you want to know more then I implore you to do some research of your own.

Electromagnetic radiation

By Lawrence Henry

There are many different types of electromagnetic radiation. These types range from radio waves to gamma rays. Each type has a different wavelength. I will explain each of them.

Radio waves

Radio waves have wavelengths from 10000km to 1m. They are used for communication and navigation. They are generated artificially by transmitters and naturally by pulsar stars.

Microwaves

Microwaves have wavelengths from 1m to 1mm. They are used for communication, navigation and cooking. They are generated artificially by antennas and naturally by stars and the cosmic microwave background.

Infrared

Infrared waves have wavelengths from 1mm to 700nm. They have many uses, including communication and heating. They are generated artificially by some light bulbs and naturally by stars and living things.

Visible light

Visible light waves have wavelengths from 700nm to 400nm. They are used for seeing. They are generated artificially by light bulbs and naturally by stars.

Ultraviolet

Ultraviolet waves have wavelengths from 400nm to 10nm. They are used in fluorescent lights. High energy ultraviolet waves can ionise atoms.They are generated artificially by some light bulbs and naturally by stars.

x-rays

X-rays have wavelengths from 3nm to 30pm. They are used in medicine.

They can ionise atoms. They are generated artificially by x-ray machines and naturally by black holes.

Gamma rays

Gamma rays have wavelengths of less than 10pm. They are used to kill germs.

They can ionise atoms. They are generated artificially with some lasers and naturally by radioactive decay and some types of supernova.