Waves and the Universe Flashcards Preview

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Flashcards in Waves and the Universe Deck (28):

What is the Solar System part of?

The Milky Way Galaxy


What is a galaxy?

A collection of stars


What does the universe include?

All of the galaxies


What is Neptune?

Furthest planet from the Sun


What is Proxima Centauri?

Nearest star to the sun


What is Andromeda?

Nearest large Galaxy to the Milky Way


How are other regions of the electromagnetic spectrum used by other telescopes?

Modern telescopes can be designed to detect almost any part of EM spectrum - shows things that can't be detected using visible light


How does data gathered by modern telescopes impact our understanding of the Universe?

Observation of galaxies better - improved magnification
Discovery of objects not detectable using visible light - different types of telescope
Ability to collect more data - telescopes use digital cameras to record images, computers analyse images & look for new objects


Why are some telescopes located outside the earth's atmosphere?

Can produce clear & sharp images because above atmosphere, so light wages from space not reflected or refracted by clouds/dust/movements of air
Atmosphere absorbs wavelength of radiation some telescopes are designed to detect


What are space probes?

A space vehicle that can be put into orbit around a planet or moon, or parachuted down through the atmosphere


What have space probes orbiting Mars done?

Photographed channels created by flowing water in the past


What are landers?

A space vehicle that lands on a planet or moon


What have landers in Mars done?

Experiments on soil to look for chemical changes that may have been caused by living organisms
One showed some changes but others did not
Conclusion: no evidence for life


What is Search for Extraterrestrial Intelligence (SETI)?

Series of projects that analyse radio waves coming from space
Look for signals possibly produced by intelligent beings
None detected so far


Describe the formation of stars

Nebula - cloud of dust and gases (mainly hydrogen)
Materials pulled together by own gravity
Hydrogen hotter - gravitational potential energy converted to thermal energy
Cloud contracts, denser, starts to glow
More mass attracted, gravitational pull stronger, compresses material more (protostar)
When temp & pressure high enough, hydrogen nuclei fuse - form helium (fusion reaction)
Lot of energy released as electromagnetic radiation (star in main sequence)


Describe the life cycle of stars like the Sun

After 10 billion years - most hydrogen fused to helium
Core of star not hot enough to withstand gravity - collapses
Outer layers expand (red giant - much larger than original star)
Fusion reactions happen inside red giant
After 1billion years - shell of gas thrown off
Rest of star pulled together by gravity - collapses (white dwarf)
No fusion reactions inside white dwarf - gradually cool over billion years - black dwarf


Describe the life cycle of massive stars

Stars considerably bigger than sun - hotter & brighter
Fuse hydrogen to helium faster - red supergiant
End of red supergiant period - star rapidly collapse then explode (supernova)
In explosion, outer layers of supergiant cast off, expand outwards
IF REMAINS 4+x MASS OF SUN - gravity pull remains together to form black hole
IF REMAINS LESS THAN 4x MASS OF SUN - gravity pull remains together to form small very dense star (neutron star)


What is the Big Bang Theory?

Whole universe & all matter started out as tiny point of concentrated energy about 13.5 billion years ago
Universe expanded from this point, still expanding


What is the Steady State Theory?

Universe has always existed, is expanding
New matter continuously created as universe expands


What evidence supports the Big Bang Theory?

Red shift
CMB radiation


Why is the Big Bang Theory currently the accepted model for the origin of the Universe?

More evidence supporting it than SteadyState Theory


What is Cosmic Microwave Background (CMB) radiation?

Microwave radiation received from all over the sky, origniting from the Big Bang


How was CMB radiation discovered?

Microwave signals detected coming from the sky discovered by astronomers
Radiation predicted by Big Bang Theory - huge amounts of radiation released at beginning of Universe & should still be detectable as microwave radiation


What happens if a wave source is moving relative to an observer?

Change in observed frequency & wavelength
Wavelength behind source 'stretched' longer behind source, and shorter in front


Define red shift

Waves emitted by something moving away from an observer have their wavelength increased and frequency decreased compared to waves from a stationary object


Describe how red shift occurs

Visible spectrum of light from stars contains gaps
If these are red-shifted, star moving away from us
If shifted in opposite direction, star moving towards us


Why does the red-shift of galaxies provide evidence for the universe expanding?

1920s - Hubble measured how far gaps between visible light spectrum were shifted for many galaxies. Discovered they were all red-shifted, all galaxies therefore moving away from us. Further away a galaxy is, faster it is moving away from us. Universe must be expanding


Why do both the Big Bang Theory and Steady State theory both account for red-shift of galaxies?

Both predict universe is expanding
Red-shift shows that galaxies moving away from us & therefore expanding