Question 1 of 12Correct: 0
What would the sky be like in an infinite, eternal universe?
Why is the sky dark after all?
Why does the expanding Universe have no center?
Why aren't Earth and the Solar System stretching?
What is the mystery of antimatter?
What is known about the cause of the imbalance?
Why do scientists trust the estimate of the Universe's age?
What is a tension in measurements of expansion?
Why might the question "what came before" make no sense?
What could help test models of the universe's beginning?
What grows after the hot, dense phase?
Why does the cosmic background radiation come from all directions?
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Why the Night Sky Is Dark Instead of Whitein the app0/2Why the Universe Is Expandingin the app0/2Where Did the Antimatter Go?in the app0/2How We Know the Age of the Universe0/2What Came Before the Big Bang0/2What the Big Bang really was0/2
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Answers and explanations12 questions
- What would the sky be like in an infinite, eternal universe? Glowing in every directionEvery line of sight would eventually end at a star, just as a look into an infinite forest would end at a tree trunk.From “Why the Night Sky Is Dark Instead of White”
- Why is the sky dark after all? The universe is not infinitely old, and light from distant stars has not arrivedDust does not solve the problem: after absorbing light for centuries, it would heat up and glow itself.From “Why the Night Sky Is Dark Instead of White”
- Why does the expanding Universe have no center? Space is stretching everywhere at onceSpace itself is expanding between galaxies, so from any one of them, the others appear to be moving away.From “Why the Universe Is Expanding”
- Why aren't Earth and the Solar System stretching? Gravity within them is stronger than expansionWhere objects are tightly bound by gravity, the expansion of space doesn't increase the distances between them.From “Why the Universe Is Expanding”
- What is the mystery of antimatter? It should have formed equally with matter, but matter remained and it did notIf the amounts had been equal, everything would have annihilated, leaving only radiation in the universe.From “Where Did the Antimatter Go?”
- What is known about the cause of the imbalance? The cause is unknownThe problem is precisely defined, but physics still has no generally accepted answer today.From “Where Did the Antimatter Go?”
- Why do scientists trust the estimate of the Universe's age? Three independent methods give a similar resultAn error in one method would not be reproduced by the other two, which work in completely different ways.From “How We Know the Age of the Universe”
- What is a tension in measurements of expansion? A discrepancy between two ways of measuring the expansion rateThe discrepancy is persistent and means something is missing from the model.From “How We Know the Age of the Universe”
- Why might the question "what came before" make no sense? Time may have begun with expansionIf time began with expansion, there is simply nothing for the word "before" to refer to.From “What Came Before the Big Bang”
- What could help test models of the universe's beginning? The cosmic microwave background and gravitational wavesTraces of early events in the cosmic microwave background and gravitational waves could provide the tests we need.From “What Came Before the Big Bang”
- What grows after the hot, dense phase? Distances between thingsSpace itself grows, so distances between things increase rather than fragments flying apart.From “What the Big Bang really was”
- Why does the cosmic background radiation come from all directions? It is light from the early hot phase, still travelingWhen matter became transparent, the early radiation began traveling freely and still reaches us from every direction.From “What the Big Bang really was”