# All Questions

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### What effect does the Moon have on the near Earth asteroid population?

Does the big (0.012 Earth masses) Moon of Earth clear away NEAs, Earth orbit crossing asteroids, in a significant way? Venus and Mars don't have large moons, do they therefore have larger or smaller ...
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### Have we seen a black hole?

Have we actually seen a black hole out there? By "seen" I mean "recorded a em-spectrum image of gravitational lensing caused by object believed to be black hole".
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### What would happen if those gravitational waves were much stronger?

What if those gravitational waves detected would be actually so strong that the distance of those mirrors moved would be larger? Not 1/1000th of proton but rather one millimeter, or one meter or even ...
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### How to derive the redshift of GW150914?

We all know LIGO has detected gravitational wave(GW) directly. prl The LIGO team argue they detected the merger of two solar mass black holes($36M\odot+29M\odot-3M\odot$) at z=0.09. My questions ...
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### Why can we detect gravitational waves?

Now that LIGO has finally measured gravitational waves using a huge laser interferometer, to me, the question remains, why was it possible? As it is explained in many news articles, gravitational ...
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### What caused gravitational waves detected by LIGO?

I understand that in recent discovery gravitational waves have been detected. But knowing space time is not static it probably changes constantly in many places in the universe due to changes in ...
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### Will we see gravitational waves from the big bang?

This is almost identical to an unanswered question already asked, but I want to put it a different way. The announced LIGO event was from a localized source. I assume that gravitational waves from the ...
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### Why do Earth and moon move apart but binary black holes move closer?

According to the accepted answer on Is the moon moving further away from Earth and closer to the Sun? Why?, the moon is receding from Earth because tidal forces and friction cause energy to be lost. ...
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### Does a spinning mass follow a straight trajectory in space? Or is it curved like a golf ball?

Suppose that we can send to identical satellites (like Voyager 1&2) on identical trajectories. But one spins to the right while the other spins to the left. Would they follow the same ...
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### How the magnetic field and the rotation of the planets and the sun inside our planetry system are related

Coming from this question Are there collected data about the direction of rotation of black holes and the direction of the magnetic field? I want to know: How the magnetic field and the rotation of ...
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### Is the Earth Really Spinning? (honest question)

Most people consider it common knowledge that the Sun's "movement" in the sky is only perceived due to the Earth's "spin and movement". Based on this, you'd think that the stars in the night sky ...
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### Relationship between absolute magnitude of a star and its luminosity?

Why does this relationship involves the absolute magnitude of the sun and its luminosity? How to derive an expression relating the absolute magnitude of a star to its luminosity? So according to ...
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### Gravitational wave detection time difference between LIGO Livingston and LIGO Hanford

Quote from LIGO's news release: By looking at the time of arrival of the signals—the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford—scientists can say ...
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### Can black holes collide with the Sun? In that case what will happen?

Can a black hole collide with the Sun? What will happen in that case? Will the Sun survive?
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### When stars explode why can we still see them?

This might be a silly question but if light travels at the speed of light and time is frozen in that speed then why the stars we see could be dead already and not just instantly disappearing from the ...
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### Spinning black hole vs non spinning black hole

Does a spinning black hole have a stronger gravity than a non spinning one.After all, a spinning black hole is stretching space-time more, so does that make a difference is gravity?
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### Can a black hole rip spacetime

Can a black hole which has an enormous mass and spins so fast cause spacetime to to be stretched to is absolute limits that it start so rip?
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### Quantum Mechanics after Gravitational Waves detection

Of course everyone knows by now the detection of Gravitational waves (http://www.iflscience.com/space/gravitational-waves-observed-first-time) But, since General Relativity and Quantum Mechanics ...
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### Measuring time and distance in space

When reading through articles about discovering gravitational waves, I got basic understanding of events that happened. But one thing wasn't clear for me. They say that two black holes collided 1.3 ...
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### How to compensate the effect of tectonic activity in devices like LIGO?

In late 2015, the LIGO project team announced the detection of gravitational waves. The detector is (very basically) a laser measuring the distance between two mirrors in vacuum, over a large-enough ...
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### Why is the detection of gravitational waves such a “Big” deal?

I'm a non-scientist. Today's announcement of LIGO's detection of GW waves has been heralded as "huge" –on the same level as the Higgs Boson detection. I realize this is the last remaining part of ...
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### Is it possible to get a glimpse of the Big Bang through gravitation waves?

I read in an article announcing the detection of gravitational waves by LIGO that it will be possible to detect them from the Big Bang. Is this true?
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### The black hole binary that was detected by advanced LIGO - how do such hypergiant binaries form?

With today's announcement of the historic detection of gravitational waves from the merger of 36 solar mass and 29 solar mass black holes 1.3 billion light years away, one can not help but wonder how ...
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### Are there other universes? [duplicate]

Our universe is a very unlikely place. Alter some of its settings even slightly and life as we know it becomes impossible. In an attempt to unravel this "fine-tuning" problem, physicists are ...
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### Where can I watch the announcement from LIGO about gravitational waves?

Today the LIGO consortium are having a press conference to update us on their search for gravitational waves. How should I watch the announcement?
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### Bright lines in a continuum spectrum

Dark lines in a continuum spectrum is common. But are there bright lines too? By the stimulated emission process, the light can also be amplified, right? In this case, we should get bright lines ...
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### Multiple aerobraking [on hold]

I moved this question to more related : Space exploration I spent a lot hours with Kerbal Space Program recently and I am courious about one thing. I got into orbit of moon and then I was able to ...
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### What Are Some Good Southern Hemisphere 7x50 Binocular Targets?

I've been interested in astronomy for a while but only recently purchased my first set of binoculars (7x50). I've been learning various constellations as well as spotting some other objects with the ...
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### What is driving the expansion of the Universe?

Is it just the momentum from the Big Bang? If yes, how can it account for the acceleration of the expansion? Why isn't the collective gravitational force slowing it down? What part does dark energy ...
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### Is the colour of a wave from a far galaxy the same for us as for a galaxy which lies between?

Because of the expansion of the universe, light from a far galaxy is redshifted. The expansion of the universe will make the wavelength of light longer. But is the colour of such light the same for ...
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### energy can neither be created nor destroyed [on hold]

I've studied that energy cannot be destroyed,but when light is absorbed by black hole then it is destroyed because there is a theory that when light enters the black hole,some times it may transported ...
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### Why is it said that the far side of the moon's crust is thicker?

This video states that NASA has determined that the far side of the moon's crust is thicker than the near side's crust. How did they determine this? Please note I'm not asking for theories or ...
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### Why do planets move in an elliptical orbit?

I am a student of class 9 and recently came to know about kepler's law of planetary motion and got confused about the foci and elliptical orbits of planets and some stars.
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### Where do new stars get their hydrogen from? [duplicate]

When stars run out of hydrogen, they explode (though they also use heavier elements for some time) and form nebulae. In the nebulae, new stars are born which use hydrogen as their fuel. So, my ...
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### How does the electric universe theory see the repelling forces happening in universe?

The Electric Universe Theory (EUT) explains why gravitational forces aren't real and not needed because these forces can also be explained by electromagnetic forces. But using these electromagnetic ...
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### What do gravitational waves allow us to understand?

Before reading this question, you should read this paper. From what I understood, we managed to detect gravitational waves for the first time. Is this discovery going to help us understand ...
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### How do star densities work?

If we take a look at stars more massive than the Sun, their densities vary a lot. UY Scuti is an extremely low-density star that's only 8.5x more massive than the Sun, but is 1000-2000x its size. ...
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### What would we not know without spectroscopy?

What do we depend on spectroscopy to know about in astrophysics? Or, without spectroscopy, what would remain unknown to us? I want to know how important it is. My wife is studying spectroscopy in ...
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### Convert axis display in ds9

I have a fits file of an echellogram with the axes showing the pixel indices. However, I would like to convert my horizontal axis from pixel to wavelength given that I have a conversion formula for ...
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### Why do pre-main sequence stars show lithium in absorption?

This paper and this paper state without discussion that the presence of lithium absorption in the stars they observe as strong evidence of these stars being pre-main sequence stars. Because they state ...
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### Determining distance from semi-major axis and eccentricity

I am trying to obtain the distance covered by an object in orbit around the earth within a specified amount of time past its perigee passage. The object is in an elliptical orbit with eccentricity 0.2 ...
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### Why does mass naturally move closer toward's the center of other masses?

If general relativity is understood to mean that mass curves space such that objects are still traveling in a straight line, why does mass naturally move closer toward's the center of other masses?
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### What conditions would lead to this event around the black hole in the Pictor A galaxy?

This is a picture of a jet of particles exiting the supermassive black hole in the center of Pictor A galaxy at nearly the speed of light. Source This event is supposedly created from a black hole ...
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### Is parallel universe possible [duplicate]

Does parallel universe really exists or just science fiction which ain't possible? Can we ever know ?
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### What was the entity/particle/state at the time of the Big bang?

At the time of the big bang if there was an original entity, what were it's attributes(if applicable) - mass, electric charge, color charge or spin? Can the current matter and dark energy together ...
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### Is there any support for the Big Crunch Theory? Could there have been a partial Big Crunch in the past?

Is there proof in either the CMB or other observed astronomical phenomena for Big Crunch? Could there have been a partial Big Crunch maybe like a cluster of Black Holes colluding to create a ...
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### Are there any studies that prove/disprove the Oscillating Universe Theory?

Can anyone cite some studies that provided proof of events/phenomena that either prove or disprove the theory?
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### Is it observable what is the north and what is the south pole of magnetic fields of stars and black holes?

The question is related to this about Are there collected data about the direction of rotation of black holes and the direction of the magnetic field?. Perhaps it is observable for pulsars?