Physics Flashcards
What happened in the first second during the Big Bang?
t=0: Singularity, zero volume and infinitely dense. There was only energy, no matter. Also, there was 1 force.
t=1e-43: The first moment in time that can be described by science. It is called quantum cosmology, because quantum physics applied. Size of the universe at this point in time was 1e-33 cm. The temperature was 1e32 C.
t=1e-35: The size of the universe has grown much, so it must be expanding. A process of baryogenesis starts: matter and energy start to decouple. Baryonic matter is the matter we can observe, consisting of matter and anti-matter (but not dark matter). Because there was more matter than anti-matter, and matter annihilates(tenietdoen) anti-matter, matter finally survived.
t=1e-11: This is the first moment that scientist have been able to recreate in labratory. It’s the period of particle cosmology, where the unified force broke down into it’s 4 components:
- Gravity
- Electromagnetism
- Strong nuclear force
- Weak nuclear force
Photons were created but it was too dense for light to shine
t=1e-2: This is called the period of standard cosmology, which is very well described by scientific laws. Expansion continued and the universe cooled. The baryonic matter began to bond and form neutrons and protons.
t=1: Nucleosynthesis: Neutrons and preutons bound to become nuclei of
- 75% hydrogen (deuterium),
- 24% helium
- 1% lithium
t=1e2: Temperature is now 1e9 C. It was still too hot for electrons to join the nuclei and form atoms. Instead, the electrons collided with positrons, to create light. But it was still too dense to shine.
t=5,6e4: Temperature is now 9e3 C. The density of the matter is equal to the density of radiation (?)
t=3,24e5: Temperature is now 3e3 C, low enough for the electrons to join the nuclei and form atoms
t=3,8e5: The density was low enough for the universe to become transparent: light could shine. CMB (cosmic microwave background radiation) began to exist.
t=1e8 (~1000 days): Gravity causes gasses to contract together, which make them dense and hot. Stars formed out of them.
Stars eventually explode. When they did, they ejected many other elements than the basic three.
Why does light bend in a prism?
Because the lower part of the wave hits the prism first. Inside the prism, the light travels slower. So the upper-part is going faster, because it’s still in air. This causes the wave to bend forward.
What is Energy?
The measure of a system’s ability to perform ‘work’
What is matter?
There is no strict definition, and the word is omitted in science. However, one can define matter as:
Anything that has mass and volume (occupying space)
What is a photon
A photon is a ‘packet of energy’ which we see as light. It is emitted by an atom at the moment that an electron falls back from a higher-energy orbit (farther away from the nucleus) to a lower-energy orbit (closer to the nucleus). Because the energy that is lost needs to go somewhere, it emits the photon. Note, that the atom first need to get ‘excited’ (meaning: it has absorbed some energy which made an electron jump to an orbit farther away)
