Astro-2: History of the Universe.


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Astro-2: History of the Universe. Address 3; April 7 2009. Already.. On Astro-2. The universe is much bigger than the Smooth Way (Gpc versus kpc) There are billion of cosmic systems, the Smooth Way is regular person world Most systems can be grouped taking into account their appearance as Circular
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Astro-2: History of the Universe Lecture 3; April 7 2009

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Previously.. On Astro-2 The universe is much bigger than the Milky Way (Gpc versus kpc) There are billion of systems, the Milky Way is regular person cosmic system Most worlds can be arranged in light of their appearance as Elliptical Lenticular Spiral Irregular Spirals pivot and have youthful stars, gas and dust Ellipticals don\'t turn and have old stars, no gas nor dust

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Previously.. On Astro-2 It is troublesome however essential to make sense of the size and separation of things in the universe One way cosmologists do that is by utilizing “standard candles”. Cases of standard candles are cepheids variable stars and supernovae

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Previously.. Two imperative inquiries Are there dark gaps in cosmic systems? What is a dark gap?

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Previously.. Two imperative inquiries How would we know it? Precisely in the same way we know the sun\'s mass, or the mass of universes so far as that is concerned!

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Previously.. Two imperative inquiries If the universe is homogeneous and isotropic how do stars realize that there is a focal point of a cosmic system to circle around? It is a matter of scale: On scale much bigger than a Mpc the universe is homogeneous On scales much littler than a Mpc the universe is NOT homogenous, there are worlds, for instance.

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Today.. On Astro-2 How far are worlds? Measuring speeds and “redshifts”. Hubble’s law. The Universe is extending.

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How far are cosmic systems? Hubble proceeds to work… In 1923 Hubble demonstrated that M31 was 750 kpc away But how enormous was the universe? How far were the various worlds? Utilizing the 100 inch telescope on Mount Wilson, Hubble returns to work and measures separations to numerous cosmic systems, to the extent Mpc away He utilizes standard candles, as cepheids.

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Measuring speeds. There is a whole other world to life than separations, says Hubble.. Hubble and his partner Slipher and Humason utilize huge telescopes to take spectra of those galaxies… They need to discover what cosmic systems are made of! Shock, shock! they find that most cosmic systems are moving AWAY from us

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Measuring speeds with a range. Doppler Effect Like the sound of a squad car When the auto is drawing nearer you hear high pitch, when is fleeing you hear a low pitch The same with light: When something is drawing nearer you see “bluer”, more fiery light (blueshift) When something is retreating you see “redder” light, less enthusiastic, light (redshift) This is called “Doppler Effect”

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Measuring speeds with a range. Doppler Effect Quantitatively, because of the Doppler impact, the WAVELENGTH λ 0 of some otherworldly component is moved to an alternate wavelength λ For a retreating question, the redshift z is the measure of movement towards longer wavelengths: Z=( λ - λ 0 )/λ 0 For z much littler than 1, the viewable pathway speed is v=cz, where c is the pace of light (see Universe Chapter 24 for general recipe)

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Measuring Redshifts, a case. CaK 3933 Å Z=0 Z=? V=? Where is the element now?

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Measuring redshifts, an illustration. CaK 3933 Å Z=0 Z=0.1 V=30,000 km/s Where is the element now?

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First rundown Hubble measured separations to numerous cosmic systems out to a few Mpc away Taking spectra of the nebulae, Hubble and his associates had the capacity measure the relative speed of worlds concerning us They found that most universes are redshifted, as though they were moving far from us!!

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Measuring speeds. Cosmic systems are moving far from us! Hubble found that most cosmic systems were moving far from us! Moreover, the more far off the system, the bigger the redshift

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Hubble’s law: cosmic systems are moving far from us! Hubble found that redshift (or speed) is relative to remove ( Hubble’s law ): on the off chance that you measure twofold speed, you likewise measure twofold separation!

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Hubble’s law: the Hubble steady The proportion between speed v and separation d is a consistent, called the Hubble Constant or H 0 =v/d This is marvelous! In the event that we know H 0 it is adequate to quantify speed (or redshift), which is simple, as we saw prior, to figure out the separation to any cosmic system!!

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Even Hubble makes mistakes…. Hubble’s first estimation of the Hubble consistent wasn\'t right: 500 km/s/Mpc, rather than the present best gauge of 71+-8 km/s/Mpc

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Even Hubble makes mistakes…. Hubble’s slip-up was because of different reasons including that he utilized as standard candles things that were not standard candles

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However Hubble’s law is substantial.. what\'s more, we can utilize it to surmise separations. Space experts like to utilize redshift rather than speed on the grounds that that is the thing that we measure. Additionally redshifts are not appropriately a measure of rate in the sound judgment of the world, however a development\'s measure of the Universe as we will see. A speculation of Hubble’s law gives you the separation to any cosmic system, if you know the redshift

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Hubble’s law. The Hubble steady is NOT a tackled issue The Hubble consistent is apparently the most critical number in cosmology What is at present considered the best estimation gives the Hubble consistent to inside 10% (71+-8 km/s/Mpc), as though you knew your stature inside with 7 inches or somewhere in the vicinity.. [even better in the event that you incorporate different suspicions: WMAP 70.1+-1.3 km/s/Mpc] quite a few people are as yet attempting to enhance our estimations of the Hubble consistent.

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Summary 2 Hubble’s Law takes care of a major issue, giving separations to any article If you know the redshift of a cosmic system you know its separation with a given accuracy, equivalent to the exactness with which you know the Hubble Constant Redshifts can be measured correctly, a great deal more accurately than you know your tallness!!! Thus space experts for the most part say a universe is at a redshift z=0.4231, as opposed to citing its separation Distances can be known just to around 5-10% In cosmology, as in all of material science, estimations additionally accompany an instability, similarly essential as the number itself

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Hubble’s Law. Talk Are all worlds redshifted? No Why?

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The Universe is extending Hubble’s law is not just an advantageous approach to acquire separations to systems from their redshifts Hubble’s law has a significantly more significant criticalness In the present standard cosmological model, Hubble’s law is accepted to be the development\'s aftereffect of the Universe

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The Universe is growing

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The Universe is growing. Significance of the Hubble consistent In our model of the growing universe the Hubble steady speaks to the present extension rate of the Universe What is a development rate? Consider an interest rate on your bank account.. 3% every year now, one year from now may be diverse.

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The Universe is growing. Importance of the Hubble steady The Hubble consistent additionally gives the timescale for the extension. In “normal” units the Hubble Constant is more or less 1/(10 Gyrs) This lets us know that the Universe\'s age is of request 10 Gyrs The vast estimation of the Hubble consistent got by Hubble inferred a much shorter existence of the Universe, of request 1-2 Gyrs. This brought on issues as it was conflicting with the period of Earth, for instance

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The universe is growing. Every now and again asked questions… What is the universe venturing into? Nothing, the universe is all there is, spacetime is growing itself Where is the focal point of the development? No place, there is no inside, the universe is homogenous and isotropic Do we extend also? No, in light of the fact that we are bound by electromagnetic powers Do cosmic systems grow? No in light of the fact that they are bound by gravity and they disengage from the Hubble Flow

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The universe is growing. All the more every now and again asked questions… Are systems at z=2 moving speedier than the velocity of light? No, the watched redshift is not by any stretch of the imagination a Doppler impact! It’s just a geometrical impact because of the universe\'s extension. As the universe gets bigger wavelengths get extended, bringing about the watched redshift.

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Summary 3 Hubble’s law is deciphered as confirmation that the universe is growing. The universe is not venturing into anything, space itself grows. The timescale for extension is given by the backwards of the Hubble consistent ~ 10 G

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