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1500 questions
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Are binary neutron star mergers needed to explain the abundance of gold?
The NPR News item Astronomers Strike Gravitational Gold In Colliding Neutron Stars mentions and quotes "Daniel Kasen, a theoretical astrophysicist at the University of California, Berkeley:"
He spent late nights watching the data come in and says…
uhoh
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If dark matter bends light, how do we know the stuff in the sky is where we think it is?
We measure movement, position, and many other things of an object in space because of its light and what we can measure with it. But as far as I know there's supposed to be a HUGE amount of dark matter in space whose mass and size we don't know, and…
Sebastian Araneda
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Why didn't the Big Bang produce heavier elements?
Shortly after the Big Bang, temperatures cooled from the Planck temperature. Once temperatures lowered to 116 gigakelvins, nucleosynthesis took place and helium, lithium and trace amounts of other elements were created.
However, if the temperatures…
Sir Cumference
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Quantum Mechanics after the detection of Gravitational Waves
Of course everyone knows by now of the detection of Gravitational waves
But, since General Relativity and Quantum Mechanics don't get along, can we say now that this detection proves that Quantum Mechanics doesn't actually apply and that General…
Odin
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Age of the universe and time dilation
Given our knowledge and the standard cosmological model, we estimate that the age of the universe is about 13.7 billion years old.
How much sense does it make to talk about the age of the universe as a whole?
We can observe time dilation so we…
toniedzwiedz
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Is it possible for a lunar eclipse to occur before sunset
I am thinking of a partial lunar eclipse where the Sun has not set yet but all three celestial objects are at such an angle that the Earth can cast some of its shadow on the Moon. Is such a scenario possible? How common is it?
Aaron S
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Could liquid water have existed in open space 15 million years after the Big Bang?
Around 15 million years after the Big Bang, the ambient temperatures was about $24^\circ {\rm C}$, which is in a range where water could be liquid. Could liquid blobs of water be existent then?
PS: I am not talking about water on the surface of any…
Cerelic
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The moon has just the right speed not to crash on the Earth or escape into space. What are the odds?
My understanding is that the moon was created a long time ago when Earth was hit by a big asteroid.
The debris then agglomerated into the Moon, which happens to be orbiting at the exact speed required to neither crash back into the Earth, nor escape…
Zoltan
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What are the odds that the Sun hits another star?
The Sun moves around the Milky Way disk in the same direction as most of the other stars in our galaxy (prograde). But there are a number of older stars in the galactic halo that move in retrograde orbits, and some of them pass between the Sun and…
Connor Garcia
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How early could we detect an asteroid the size of the one that caused the extinction of the dinosaurs?
Would we know months, years ahead? How sophisticated is our technology's ability to detect it at 100% accuracy?
CupOfGreenTea
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How did Eratosthenes know that the sun is far away?
The famous measurements and calculations done by Eratosthenes around 300 BC are very widely known. He concluded correctly that the circumference of the Earth is about $252\,000$ times the length of an athletic stadium.
But what Eratosthenes did…
Michael Hardy
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How far apart are stars in a binary system?
I'm wondering how far apart from one another the stars are in binary systems.
What is the distribution of the separation between binary stars? Are most of the binary stars very far apart like Sirius (8.2 to 31.5 AU)? Are there many stars in orbits…
usernumber
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Is the universe considered to be flat?
I've read various articles and books (like this one) stating that we are not certain about the geometry of the universe, but there were experiments on-going or planned that would help us find out.
Recently though, I've watched a lecture by…
ivanmp
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Pluto's orbit overlaps Neptune's, does this mean Pluto will hit Neptune sometime?
We know that the orbits of Pluto and Neptune overlap.
This means that pluto sometimes crosses the orbit of Neptune; will Pluto hit Neptune in any circumstance?
ReNiSh AR
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How many stars and galaxies can be seen by the naked eye?
How many of the luminous dots that we see naked are galaxies and not stars from our galaxy?
I imagine that the majority of the luminous points that we see naked eye during the night, are actually stars from our galaxy. But how many of them are other…
Mario Stefanutti
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