Tag Archives: cosmology

Light Travel Time from Exploding Stars

Question:  I am not able to understand one thing, when we say we saw a star exploded billions of light years away, does it mean it exploded billions of light years ago but the light reached to you just now. … Continue reading

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The Kerfuffle Over Non-Cosmological Quasar Redshifts

Question:  Some years ago I read an article that said (if I recall correctly) that there were quasars that seemed to be associated with galaxies (maybe in the center), but the quasar’s much larger red shifts implied that their distance … Continue reading

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How Do Astronomers Study How Things Evolve?

Question:  We know that stars and galaxies we see are just fossil light as they were millions or billions of years ago. Is it possible to extrapolate the changes that we see today in those galaxies to determine their current … Continue reading

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What is a Fairly Representative Radio Astronomy Project?

Question:  What is a fairly representative project a radio astronomer might be involved with perhaps to investigate dark energy or some other equally interesting phenomenon?  – Steve Answer:  As the number of interesting projects that one can do with radio … Continue reading

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Dark Matter and the Stuff Humans are Made of

Question:  If dark matter does not emit or reflect any kind of light, (As I have heard from Neil deGrasse Tyson’s Cosmos series) then how come we can see [ourselves in] a mirror?  – Cyrus Answer:  Scientists love to perform … Continue reading

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Optical and Radio Measurements of the Gravitational Bending of Light Around the Sun

Question:  VLBA measurements have been used to confirm gravitational bending of radio waves by the Sun in confirmation of General relativity of 1″.75 prediction. Most optical observations are usually higher than this. What amount of VLBA data measurements show a … Continue reading

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Top Achievements for the NRAO Very Large Array

Question:  I’m embarrassed to ask this, as I feel after working here for so long I should already know the answer. But here it is: What are the top 3 discoveries/achievements of the VLA? And why?  — Doug Answer:  As … Continue reading

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What is the Difference Between the Redness of an Object and its Redshift?

Question:  What is the difference between Doppler shift of light and Natural light spectra (blue for young and red for old) with respect to stars and galaxies? How does astronomers differentiate between Doppler shift and Natural light spectra of deep … Continue reading

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What is the Flux Density of the Cosmic Microwave Background?

Question:  The temperature of the CMB is about 3 Kelvin, but the 3 K here mean the brightness temperature or the antennna temperature ? what is the CMB flux density ? – Hongmin Answer:  The CMB temperature is the physical … Continue reading

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How Did the First Galaxies Form?

Question:  From where did this initial cloud of gases and dust come? In other words, how did the cloud form? Why were these gases and this dust together in a cloud? I read on another website that the cloud began … Continue reading

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