Astronomy and Cosmology

I notice that no one is discussing ΛCDM cosmology here. Is this considered "speculative," or do most folks here just not know about it?

whats your view on the probability of the main composition of a black hole being made up of gravitons

Can the universe be thought of as an expanding surface of a 4D sphere? If so could it be rotating and so be the cause of phenomena like pinwheel galaxies that resemble things on the surface of a rotating 3D sphere like a hurricane? Just a random idea, sorry if it's stupid...

I came across two articles in Science News of alpha not being a constant. (I do not have a subscription yet, so I have been unable to read the full article.) First off, what is alpha and why does it matter if it is a constant or not? Yes I have (tired) to read/study about this, even went to Wikipedia, but as a funny comic strip indicated in another thread of mine, it was difficult to keep focused on the topic.

If there was no matter would space not exist also? and what if space itself is simply gravitational fields or is space nothingness?

An Idea came to mind a few weeks back and I'v had some time to mull it over, but I'm on the fence as to whether or not I think it could work. I was thinking of a way we could predict and transmit and instantaneous signal of when a solar flare is about to go off and or has gone off. I found an Article Here that describes a way to possibly predict when a flare is about to go off and use as a preemptive detector. Then I was thinking, well that's good and all, but how can we transmit that information faster than the speed at witch it will travel to Earth at (10.43 million and 12.75 million kilometers per hour). Not sure how long that would actually take to reach us, but it wo…

Hi all, I need a help to find the answer of following. As per Wikipedia and other sources Black hole is created after death of a Star. As per them when such a huge mass of supernova remnant collapses on itself and the small point(core) create an extremely strong gravitational field due to the huge mass got captured in a small point. But I can't understand what is the relationship of "volume" of the remnant to gravitational field ? When same mass(or greater) was a size of red Giant then there wasn't such a strong gravitational field there. But when the volume got smaller then how the Gravitational field got stronger ?? Thanks in Advance

How would the force of gravity differ in an Antimatter Universe?

According to concordance cosmology, the universe expands, and its increase in linear size is described by a function a(t). However, any objects that are gravitationally bound (up to the size of galaxy clusters) do not participate in this expansion. They retain their size. Minor question: How large is the fraction x of the volume of the universe that is at present, i.e., in our cosmic vicinity (up to z = 0.1 or so), occupied by gravitationally bound objects? If a(t) increases with time and gravitationally bound objects retain their size, it is obvious that x must have been larger in the past, so that at an earlier time (not extremely long ago) most or all of the …

If this question has already been answered, please direct me to the thread. I tried to do a search, but came up empty. The way I understand it, a black hole is a point in space where matter has infinite density. The question I have is: Doesn't this conflict with the idea that matter occupies space, and that no two bits of matter can occupy the same space? Wouldn't there be a point where it is impossible for something to become any more dense, because there just isn't any more space between particles? If the density of the object in question was infinite, wouldn't the gravity it produced also be infinite? If the density of the object in question was infinite, w…

This may be a dumb question. Theory tells us that black holes emit radiation as they lose mass. If a black hole swallows all that comes near, how does it lose mass?

Is it possible theoretically to have zones of backward time in the universe? This would still obey the laws of cause and effect where a more complex state would resolve into a simpler one. eg. On such a planet a human would be born old and die young. Cause and effect would still apply although defying commonly accepted norms and conventions. Entropy would still increase and people would still be eccentric. Is such a scenario possible in realty?

Fellow Scientists, I have a perplexing thought for you. This is truly intellectual and most likely cannot be tested, but an interesting idea to think about to say the least. So, I was watching an episode of Into the Universe with Stephen Hawking, and I got caught up in some thoughts. I love to think about paradoxes, and this almost seems fitting, so I'll get on with it. Light speed (3.00x10^8 m/s) is the fastest known speed, and nothing can ever match it. However, it does allow for things to get extremely close, about 99.99999% (maybe even infinitely close). Light is interesting in that a single photon doesn't have mass, yet it is there, but can still travel. Anyw…

hello everyone, this is more like a simple curiosity, yesterday night I took some pictures of the stars with my camera. the first picture was aimed at Capella and the field of view was diagonal, longitudinal and the exposition was 20 seconds, everything went fine. for the second and the third picture I wanted to grab a bigger slice of the sky, so I just put the camera on the ground facing upwards, with the focus to infinity, so the field of view was completely vertical. for the first attempt I set the shutter to 30 seconds and the stars left a trail, for the second attempt I set the shutter 15 seconds and the stars left half the trail relative to the first attempt. …

Wiki tells me that the surface of the sun is 5800K in temperature and the core is far more higher than that. Why isn't the heat in the core conducted to the surface ? What is the true reason for such a big difference in temperature? Thanks in advance. I hope you guys can explain.

Rightey, first things first, Neil Armstrong wouldn't be as famous and rich as he is, and the night sky would be darker than usual. But moving on to a more serious matter, we rely on the moon for many many things, probably the best known one is how the moon affects our tide, how it uses our oceans to keep it tidally 'locked'. Our days would be shorter, the tidal pull from the gravity of the moon slows us down. The Earths rotation slows down because of the moon, but only by about a second every 50,000 years or so. But this difference on the cosmic scale is very large, in terms of millions of years, our days would be considerably shorter! Before leaving you guys to t…

"The black hole at the center of the galaxy..." is an oft repeated phrase on the science channels. 1) The cited evidence for this is the motion of stars at the center of the galaxy. This evidence is insufficient. An object of highly collapsed matter would have the same effect. How would one distinguish between an incipient back hole and a back hole? In an incipient back hole the bulk of the matter lies outside the surface where the event horizon would form. Can highly collapsed matter exchange Hawking radiation with it's environment? 2) The Schwarzschild solution having an event horizon is non-physical. The solution stretches over transfinite time. …

Hi all, I just joined this site in search of a new community of scientists. I wanted to show you all a project I have been working on that mostly focuses on astronomy and overall science. There is not a media forum so I thought this was the place to go. So what is this project? Well, my friend and I alone have started a free, nonprofit magazine to stay updated with all of the newest data. We don't generate any revenue from this and do it for the sake of learning. Even though the magazine may look professional, we are not professionals. We are looking for some viewer input ranging anywhere from pictures, articles, comments, questions, and ideas. Please send t…

What is Trajectory Deflection Angle ? http://en.wikipedia.org/wiki/Flyby_anomaly

If I take a picture of the clear night sky and label on it the stars & planets appearing, in conjunction with the phase of the moon, and show this labelled picture to an astronomer, can he find from this information only when and where the picture was taken?

Is it possible to create super-density like a black hole or neutron star in a particle accelerator for even an iota of time like a femtosecond? And what are its long term implications? Please advise. Thanks in advance.

Do black holes gain mass when matter falls into them?

Okay, There is a speculation that most of our universe is Antimatter, but, I have a question here : When we see universe, we see stars, nebulae and all the stuff - are they not matter? If yes, then why there are some overwhelming speculations about the constituting percentage of antimatter in our universe? If no? then please explain me how?

When we look at a distant quasar we can visualize the history of the universe in its nascent phases. But what about an observer at that point. The light from a quasar at the edge of the observable universe reaches us after say 13 billion years so we can say that that object was indeed present at that point in time. But what about the corollary? Our solar system is not older than 4.5 billion years (by a conservative estimate) so somebody looking at us from out there would opine that we don't exist. So how do we reconcile this? Please advise. Thanks in advance.

Hi. Part of an article I read about Rosetta space probe states : "...The probe and its lander will keep sending back data until their batteries die or the debris streaming off the comet irreparably damages their sensitive instruments. The mission is different from NASA's Deep Impact probe that fired a projectile into a comet in 2005 so scientists could study the resulting plume of matter. NASA also managed to land a probe on an asteroid in 2001, but comets are much more volatile places because they constantly release dust and gas that can harm a spacecraft..." What forces push debris off the comet ? What forces push dust towards the landed spacecraft ?