Did the Big Bang Happen in a Pre-Existing Universe?

Question: Is it possible that the big bang occurred in a pre-existing universe? if not, how do we know?  – Gary

Answer: I think that the best evidence to support the fact that the Big Bang happened in this universe is the fact that we see evidence for its existence in our universe.  There really isn’t any reason to invoke the existence of another universe to explain the Big Bang.

Jeff Mangum

Tagged Leave a comment

Could the Accelerating Expansion of the Universe be due to a Pulling Force?

Question: Isn’t it possible that the answer to the increasing speed of the expansion of the Universe is that it is being pulled apart not being pushed apart? If the “unknown” Universe was trillions of light years of dark energy and when the “singularity” appeared, it would have exploded, for lack of a better term, inflation would have occurred, then as gravity was created, the expansion would have slowed down but as the years have gone by the power of all that dark energy, as thin as it is, will eventually overcome the gravity contained in the “known” Universe and pull it into oblivion.  – Philip

Answer: To suggest that the accelerating expansion of the universe is caused by a “pulling” force rather than a “pushing” force would require identifying the source of the “pulling”.  Dark energy is theorized to be a component of the known universe that we had not originally appreciated.  If one wants to incorporate an external force, then one needs to identify from where this force came, which is the difficult part.

Jeff Mangum

Tagged , Leave a comment

How Can a Supermassive Black Hole Form in a Galaxy Only 900 Million Years After the Big Bang?

Question: It is a challenging research topics to search how supermassive black holes formed at the early epoch. I am very much interested to do my future research on this topic. Could how please tell me what can be possible solution for this problem? How can SMBH formed at early epoch?  – Anirban

Answer: The discovery of a supermassive black hole (SMBH) in a quasar (a special kind of galaxy) which is at a redshift which places it at an age of only about 900 million years after the Big Bang certainly pushes the theory of the formation of SMBHs.  One of the most popular theoretical scenarios associates the first massive black holes with the remnants of the first generation of stars in a galaxy.  I believe, though, that the discovery of this very young SMBH means that the formation of black holes must happen over a much shorter timescale than previous believed.

Jeff Mangum

Posted in Black Holes, Cosmology | Tagged , | Leave a comment

Why are Andromeda and the Milky Way on a Collision Course Rather than Moving Away from Each Other?

Question: If the universe is expanding and all galaxies are moving away from each other, how is it possible that the Andromeda and milky way galaxies are on a collision course?  – Johnny

Answer: It is correct that on the largest scales that the universe is expanding such that all galaxies are moving away from each other.  On smaller scales, though, there are so-called “peculiar motions” of galaxies, where one galaxy is found to be moving toward another galaxy due to local gravitational effects in the vicinity of the two galaxies.

Jeff Mangum

Posted in Cosmology, Galaxies | Tagged , | Leave a comment

Are There Multiple Universes?

Question: Hi! I am from Salt Lake City Utah. I’m in the sixth grade and in middle school. Middle school is really amazing and I love it. But what I love about it the most is my science teacher. His name is Mr. Krause and he is the best. he is smart funny and explains stuff in the best way! Right now we are almost done with astronomy. We started talking about the universe and I asked him this question and got a good answer but I thought I could ask you and get an even better answer? Here it is: Could we be looking at the size of the universe the wrong way? Could the universe just be one HUGE galaxy and there are multiple universes just like there are galaxies? Perhaps one day one universe will collide with another just like galaxies in our own universe.

Thanks for reading my comment! Astronomy has always interested me along with many other things about our world and its history like the past cultures. Thanks again and I hope you understand what I am trying to say.  – Kailey

 

Answer: That is really great that you have such an amazing science teacher!  You should be sure to tell him how much you enjoy his teaching.  As for your question about how we view the universe, let me just say that any description of the structure of the universe has always to be based on measurements.  In fact, this rule that any explanation of anything has to be based on fact applies to everything in science.  Now, since we observe stars and galaxies in our single universe, and we believe we have a pretty good understanding of how they interact and evolve, we feel confident that our observations are described very well by a single universe.  To turn that around, we can definitely say that we have no evidence for there being any additional universes other than our own.  That said, it is still possible that there are multiple universes, the evidence for which we just have not found yet.  This is a hypothetical scenario, though, that is not based on any measurements we have made.

I do hope that you continue to enjoy your science class Kailey and that Mr. Krause enjoys teaching science as much as you enjoy learning it.

Jeff Mangum

Tagged Leave a comment

Light Travel Time from Exploding Stars

Question:  I am not able to understand one thing, when we say we saw a star exploded billions of light years away, does it mean it exploded billions of light years ago but the light reached to you just now. Aren’t we studying the phenomena which has happened billions of light years ago. Is it possible that another big bang has already happened, just the explosion light/energy has not reached to us yet?  – Dipanshu

Answer:  When we say that we have seen a star explode that is billions of light years ago, it means that it exploded billions of years ago since that light from that stellar explosion had to travel billions of light years to get to us.  Note, though, that a stellar explosion is not the same as the big bang, in that the big bang expansion started everywhere at once, and was not characterized by an explosion at a single point.

Jeff Mangum

Posted in Cosmology, Stars | Tagged , , | Leave a comment

The Kerfuffle Over Non-Cosmological Quasar Redshifts

Question:  Some years ago I read an article that said (if I recall correctly) that there were quasars that seemed to be associated with galaxies (maybe in the center), but the quasar’s much larger red shifts implied that their distance was far more than the associated galaxies’ distances.  Has this ever been resolved?  – Bill

Answer: The research that you are referring to was done mainly by two astronomers, Halton Arp and Geoffrey Burbidge.  They proposed, based on observations of seemingly associated nearby galaxies and purportedly distant quasars, that quasars were simply ejected matter from these galaxies.  In fact, once large surveys of galaxies (such as the Sloan Digital Sky Survey), became available it was possible to better test this apparent correlation.  In summary, Arp and Burbidge were wrong, their assertion due in fact to what astronomers call a “selection effect”.  If you are interested in more details on this now historical discussion see the Galactic Interactions blog post on the subject.

Jeff Mangum

Posted in Cosmic Distances, Cosmology, Galaxies | Tagged , , | Leave a comment

How Do Astronomers Study How Things Evolve?

Question:  We know that stars and galaxies we see are just fossil light as they were millions or billions of years ago. Is it possible to extrapolate the changes that we see today in those galaxies to determine their current state?  – Vinod

Answer: In a way, yes.  Since, as you point out, we see what amounts to the “fossil light” from stars and galaxies in the universe, we can piece-together how things evolve with time by sampling various times within this fossil record to study the evolution of these stars and galaxies.  Note also that the timescales for the evolution of objects in the universe are, with few exceptions, much longer than a human lifetime, or even the total historical record of scientific measurements.  This means that astronomers must study the evolution of just about every object in the universe by sampling its evolutionary state at different times in the cosmological record.

Jeff Mangum

Posted in Cosmology, Galaxies, Stars | Tagged , , | Leave a comment

What is a Fairly Representative Radio Astronomy Project?

Question:  What is a fairly representative project a radio astronomer might be involved with perhaps to investigate dark energy or some other equally interesting phenomenon?  – Steve

Answer:  As the number of interesting projects that one can do with radio telescopes is too large to list, let me list a radio telescope project that investigates the early universe.  The Hydrogen Epoch of Reionization Array (HERA) is a radio telescope array that will, as the name implies, attempt to image the large-scale structure of the universe at the point when the first stars reionized the neutral intergalactic medium.  This aspect of the universe is one of the last unexplored phases of the evolution of our universe.

Jeff Mangum

Posted in Cosmology, Radio Astronomy | Tagged , | Leave a comment

Dark Matter and the Stuff Humans are Made of

Question:  If dark matter does not emit or reflect any kind of light, (As I have heard from Neil deGrasse Tyson’s Cosmos series) then how come we can see [ourselves in] a mirror?  – Cyrus

Answer:  Scientists love to perform experiments that clear prove a fact.  One interpretation of this observation is that this demonstrates that we are definitely not made of dark matter!  So, simply by looking in a mirror you have proven something fundamental about the material that humans are made of.  Congratulations!

Jeff Mangum

Posted in Cosmology, Physics | Tagged , | Leave a comment