Astronomy and Cosmology

I am having a hard time finding an answer to a question. So, I figured I would try the "scientific crowd-sourcing" route in hopes to find it. The question is: Does the the draw or pull of matter/gas into a black hole fluctuate or does it pretty much remain static? I am not referring to the size of the black hole, but rather just the inflow of material into said black hole. Perhaps this question can only be answered using long term observation?

Is some of the universe still antimatter and will it all eventually encounter matter and annihilate.

Since the ISS orbits at about 250 miles above the Earth so its actual gravity is 88.8 percent of that felt at ground level; what value can be derived from the experiments done on ISS in terms of actual microgravity? As in how do we know that a plant that appears to grow well in simulated microgravity does so in a gravity that is much lower, like half way to Mars or well out of the solar system?

Well while we've got you here Ophiolite... I was aware that Mars does have a molten core because it shows evidence of volcanic activity. However, Earthly volcanos show a linear motion through time, such that the volcano creates a 'crest'. On Mars they don't, a volcano will happily sit in one location, indicating that there is no plate movement. If I'm mistaken in my assessment, please correct me and elaborate. If I'm correct, why is there no plate motion over the molten core ? And if this causes a thread derailment, please split off. .

Sometimes a user will refuse to admit they made an error and continue arguing. Not listen to what they are told. Misinterpret what is being said, take issue with strawmen, and so on. It gets to seem like they are arguing just for argument's sake. We need a place for posts that might arise this way, so we can move them here and take some time to think about it---see if the post might have merit, or arises from honest misunderstanding, or is just arguing for its own sake. So here's a thread for that kind of thing, so we can move posts here and check them out. And in some cases move them back into the original thread! Hopefully, if on reflection there seems to be no …

The universe had a finite size at the start. So no matter how fast the universe expanded, except for an infinite speed which it did not, the universe must still be finite, no matter how large. How does a finite universe become infinite in size? This is not about the "observable universe" but about the entire universe.

What Effects Would Slowing Down the Moon Have on the Earth? Are the effects shown in this video scientifically realistic? video link removed

I beleive that dark energy expands the universe. Maybe dark energy is the space of the universe with electromagnetic,gravitional and other fields rushing at the speed of light.And in place where there was galaxy this movement is slowed and in the General scale of the universe with other galaxies,it appears removing them from each other with increasing speed.

all is in tthe title thank you very much for your answers

Hello, I got interested in this paper: http://arxiv.org/pdf/1511.05450v1.pdf as I was not happy to see a non-constant cosmological constant in time, I calculated the value (10 ) with the latest data planck 2015 : https://en.wikipedia.org/wiki/Planck_(spacecraft)#2015_data_release I found that they were a mistake from a strictly factor equal to 3 of the cosmological constant, and that this factor made the 3 really constant cosmological constant in time for H0 = 67.74; 59; 62; 65; 71; 75; 80; and 85. So we have: Lamba0= 3 *H0^2 *OmegaLambda \ c^2 =6Gmdark \ RHubble^3 I leave it to specialists of the forum to demonstrate equality Best regards Stéphane

I've got a couple simple questions on the matter that aren't turning up in searches. 1. Is the heliosphere visible? If you are leaving the solar system do you see it coming? If I were far enough away from the sun would I see the heliosphere bubble around it? 2. If I was EVA traveling through the heliopause, would I feel any force or anything as I pass through it? 3. If I understand correctly, the particles in the solar wind basically "pause" at the heliopause and create an equal force barrier with the outside medium. So, do particles keep building up at this point? Would that not create a cloud? 4. Going off of question 3, would that cloud be the oort clo…

Hello All, I found this article: Is our universe merely one of billions? Evidence of the existence of 'multiverse' revealed for the first time by cosmic map | Daily Mail Online "Laura Mersini-Houghton, theoretical physicist at the University of North Carolina at Chapel Hill, and Richard Holman, professor at Carnegie Mellon University, predicted that anomalies in radiation existed and were caused by the pull from other universes in 2005. Now that she has studied the Planck data, Dr Mersini-Houghton believes her hypothesis has been proven. Her findings imply there could be an infinite number of universes outside of our own. She said: 'These anomalies were caused by other …

In trying to bridge the gap between , 'No Earth' , and the ' early Earth ' 4,600,000,000 years ago , And to today . I would like to know quite what elements, came together to start off the infant earth . Were there only less diverse , different elements, molecules present at Earth Birth, the rest being generated as time passed over the last 4.6 Billion years . Or were all the elements that we have today present at ' Earth Birth ' ? Thus were they all presents in the spinning Solar System Disc ? Or Molecular Gas cloud? Or were some elements generated during the formation of the spinning disc ,making the early system ? Thus :- What ' Element wise' , Molecular wise,…

If I may quote Wikipedia here: "The Roche limit is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction." This being so, in the case of a Solar-mass body, does its Roche limit, as it applies to a given satellite, remain the same, regardless of its diameter? In other words, would the limit stay put, even if the Sun were magically shrunken into a white dwarf, while retaining its original mass? Many thanks.

Does anyone think this is possible in our current technology? Why?

Hello, I have a problem with the proof provided for universe expanding. Isn't it that any observation to support the expansion is based on light. Wouldn't it be that all the observations would be exactly the same if all the galaxies were heading towards a gravitational pull? Any object would seem to move further away because the light between the points bends towards the gravitational source with higher pace than the actual distance between the two points are contracting. (Hubbles redshift would happen etc.). Even the points in same contracting line.

The expanding universe theory illustrates that objects viewed in space are moving away from one another and the further we look into space, the faster this movement is detected. My problem with that theory is that the further we look into space, the further we go back in time, due to light having a finite velocity, so we are using non-current observational data going back as far as billions of (light) years to come up with a theory of a currently expanding universe.If we have no way of knowing what velocity distant objects are CURRENTLY travelling at, but are only measuring the redshift of their image emitted aeons ago, then this theory doesnt make sense to me. In fact it…

I was asked a question, "Is the universe expanding". I went on to explain that the universe is expanding and the expansion is accelerating. To use an analogy I described the expansion as accelerating similar to the follow. Imagine you are in the stratosphere and affected by gravity and so falling back to earth (disregard an atmosphere that would cause resistance). At this distance from the earth the gravity will be less than 9.8m/sec2 but as you fall the gravity will increase towards this and you will fall faster and faster as the effect of gravity increases. Now look at that in reverse and the universe is expanding but at an accelerated rate that is increasing. T…

I just watched an amazing episode of "How the Universe Works", season 4 episode 1: Forces of Mass Construction. The episode was discussing the role of magnetism in the universe, and how it is a lot more than previously thought. There was a portion where astronomer Dr. Phil Plait stated that the shape of the Milky Way's arms are due to magnetism. Then they showed this special effects how magnetism actually prevents and creates star formation. However, I thought dark matter is the reason why galaxies don't fly apart and forms stars. So, is the theory of dark matter starting to disappear due to the discovery of magnetism on the galactic level?

Hi All, Looking again into the Casimir/Hawking/Unruh effects, made me think that: 1. Take any gravity source. 2. Use general relativity's gravity-acceleration equivalence principle. 3. The Unruh effect applies. 4. We get radiation in a similar way to Hawking radiation around a black hole? So, are black holes special in that they give enough energy for virtual particles to emit as radiation, or does every massive object (meaning one with a nonzero stress-energy tensor) have a "Hawking" radiation? To be more specific, do the Earth or Sun produce radiation in a similar mechanism as does a black hole (in addition to their more conventional radiation spectrum)?

I read a post on a website that stated that approximately 10-36 seconds after the Big Bang the Universe expanded disproportionately to the size of an orange. Is the Universe still expanding at the same rate, and if not why ?

What causes planetary wobble and does it increase over time ?

I was reading this article http://m.phys.org/news/2015-02-big-quantum-equation-universe.html I was wondering if this is correct what does this mean for the second law of thermodynamics? If the law is followed and the universe is an infinite age then entropy must be at a maximum. Observation shows this isn't the case, how would this problem be reconciled?

I have a question for those who believe that the Universe began with the Big Bang, estimates of the size of the Universe is approximately 13 billion light years from the center of the known Universe to the outer most edges, where they can detect Galaxies, they also use this to determine the age of the Universe, which is approximately 13 billion years, my question is if all matter in the Universe was created by a single explosion, then why is there Galaxies and stars spread from the center of the Universe to the outer limits of the Universe? If an explosion occurred then wouldn't all the debris spread outward, creating a circular band, and in 13 billion years the band woul…

When did the first photon emerge in the timeline of the Universe ? And how did all photons automatically get modulated to a velocity of 3 x 108 m/s ?