# 11.7 Evolution of the early universe  (Page 5/10)

 Page 5 / 10

## Summary

• The early universe was hot and dense.
• The universe is isotropic and expanding.
• Cosmic background radiation is evidence for the Big Bang.
• The vast portion of the mass and energy of the universe is not well understood.

## Key equations

 Momentum of a charged particle in a cyclotron $p=0.3Br$ Center-of-mass energy of a colliding beam machine ${W}^{2}=2\left[{E}_{1}{E}_{2}+\left({p}_{1}c\right)\left({p}_{2}c\right)\right]+{\left({m}_{1}{c}^{2}\right)}^{2}+{\left({m}_{2}{c}^{2}\right)}^{2}$ Approximate time for exchange of a virtual particle between two other particles $\text{Δ}t=\frac{h}{E}$ Hubble’s law $v={H}_{0}d$ Cosmological space-time metric $d{s}^{2}={c}^{2}d{t}^{2}-a{\left(t\right)}^{2}d{\text{Σ}}^{2}$

## Conceptual questions

What is meant by a “cosmological model of the early universe?” Briefly describe this model in terms of the four fundamental forces.

Describe two pieces of evidence that support the Big Bang model.

The observed expansion of the universe and the cosmic background radiation spectrum.

In what sense are we, as Newton once said, “a boy playing on the sea-shore”? Express your answer in terms of the concepts of dark matter and dark energy.

If some unknown cause of redshift—such as light becoming “tired” from traveling long distances through empty space—is discovered, what effect would that have on cosmology?

If light slow down, it takes long to reach Earth than expected. We conclude that the object is much closer than it really is. Thus, for every recessional velocity (based on the frequency of light, which we assume is not disturbed by the slowing), the distance is smaller than the “true” value, Hubble’s constant is larger than the “true” value, and the age of the universe is smaller than the “true” value.

In the past, many scientists believed the universe to be infinite. However, if the universe is infinite, then any line of sight should eventually fall on a star’s surface and the night sky should be very bright. How is this paradox resolved in modern cosmology?

Experimental results suggest that a muon decays to an electron and photon. How is this possible?

Each of the following reactions is missing a single particle. Identify the missing particle for each reaction.

$\begin{array}{c}\text{(a)}\phantom{\rule{0.2em}{0ex}}\text{p}+\stackrel{\text{−}}{\text{p}}\to \text{n}+?\hfill \\ \text{(b)}\phantom{\rule{0.2em}{0ex}}\text{p}+\text{p}\to \text{p}+{\text{Λ}}^{0}+?\hfill \\ \text{(c)}\phantom{\rule{0.2em}{0ex}}{\pi }^{\text{ࢤ}}+\text{p}\to {\text{Σ}}^{\text{−}}+?\hfill \\ \text{(d)}\phantom{\rule{0.2em}{0ex}}{\text{K}}^{\text{−}}+\text{n}\to {\text{Λ}}^{0}+?\hfill \\ \text{(e)}\phantom{\rule{0.2em}{0ex}}{\tau }^{+}\to {\text{e}}^{+}+{\upsilon }_{\text{e}}+?\hfill \\ \text{(f)}\phantom{\rule{0.2em}{0ex}}{\stackrel{\text{−}}{\upsilon }}_{\text{e}}+\text{p}\to \text{n}+?\hfill \end{array}$

a. $\stackrel{\text{−}}{n}$ ; b. ${\text{K}}^{+}$ ; c. ${\text{K}}^{+}$ ; d. ${\pi }^{\text{−}}$ ; e. ${\stackrel{\text{−}}{\nu }}_{\tau };$ f. ${e}^{+}$

Because of energy loss due to synchrotron radiation in the LHC at CERN, only 5.00 MeV is added to the energy of each proton during each revolution around the main ring. How many revolutions are needed to produce 7.00-TeV (7000 GeV) protons, if they are injected with an initial energy of 8.00 GeV?

A proton and an antiproton collide head-on, with each having a kinetic energy of 7.00 TeV (such as in the LHC at CERN). How much collision energy is available, taking into account the annihilation of the two masses? (Note that this is not significantly greater than the extremely relativistic kinetic energy.)

When an electron and positron collide at the SLAC facility, they each have 50.0-GeV kinetic energies. What is the total collision energy available, taking into account the annihilation energy? Note that the annihilation energy is insignificant, because the electrons are highly relativistic.

what is light
What is photoelectric
light energy (photons) through semiconduction of N-P junction into electrical via excitation of silicon purified and cristalized into wafers with partially contaminated silicon to allow this N-P function to operate.
Michael
i.e. Solar pannel.
Michael
If you lie on a beach looking at the water with your head tipped slightly sideways, your polarized sunglasses do not work very well.Why not?
it has everything to do with the angle the UV sunlight strikes your sunglasses.
Jallal
this is known as optical physics. it describes how visible light, ultraviolet light and infrared light interact when they come into contact with physical matter. usually the photons or light upon interaction result in either reflection refraction diffraction or interference of the light.
Jallal
I hope I'm clear if I'm not please tell me to clarify further or rephrase
Jallal
what is bohrs model for hydrogen atom
hi
Tr
Hello
Youte
Hi
Nwangwu-ike
hi
Siddiquee
hi
Omar
helo
Mcjoi
what is the value of speed of light
1.79×10_¹⁹ km per hour
Swagatika
what r dwarf planet
what is energy
কাজের একক কী
Jasim
কাজের একক কী
Jasim
friction ka direction Kaise pata karte hai
friction is always in the opposite of the direction of moving object
Punia
A twin paradox in the special theory of relativity arises due to.....? a) asymmetric of time only b) symmetric of time only c) only time
b) symmetric of time only
Swagatika
fundamental note of a vibrating string
every matter made up of particles and particles are also subdivided which are themselves subdivided and so on ,and the basic and smallest smallest smallest division is energy which vibrates to become particles and thats why particles have wave nature
Alvin
what are matter waves? Give some examples
according to de Broglie any matter particles by attaining the higher velocity as compared to light'ill show the wave nature and equation of wave will applicable on it but in practical life people see it is impossible however it is practicaly true and possible while looking at the earth matter at far
Manikant
a centeral part of theory of quantum mechanics example:just like a beam of light or a water wave
Swagatika
Mathematical expression of principle of relativity
given that the velocity v of wave depends on the tension f in the spring, it's length 'I' and it's mass 'm'. derive using dimension the equation of the wave
What is the importance of de-broglie's wavelength?
he related wave to matter
Zahid
at subatomic level wave and matter are associated. this refering to mass energy equivalence
Zahid
it is key of quantum
Manikant
how those weight effect a stable motion at equilibrium