Cosmo_Ken

I saw an article on the internet within the past week about a scientific paper that was published on November 22 in the Astrophysical Journal by Swiss astrophysicist André Maeder, raising the question does Dark Matter really exist and proposing an alternative theory to fit the observations, interesting, see: https://www.space.com/39001-dark-matter-doesnt-exist-study-suggests.html?utm_source=sdc-newsletter&utm_medium=email&utm_campaign=20171208-sdc And on the subject of Dark Energy, is it real or is there something fundamentally wrong with the assumptions. What was the exact methodology that the astronomers used to conclude that the expansion of the universe is accelerating, not slowing down?

Interesting. Thanks.

Thanks.

What about daily surface temperature ranges on Mars, at the equator and at the poles???

Thanks!

I realize that this is probably not the best forum to ask this question, but I thought some of you might know the answer.

Thank you Mordred and Strange, you have given me a number of links to check out! I have two other questions. First, so a recent NASA press release that said that they had observed the most distant galaxy yet, at a distance of 13.8 billion light-years, was wrong? Secondly, is the red-shift we observe with most galaxies strictly the result of the relative motion of the galaxies relative to space, or does it include the effect of the expansion of space too? Cheers. What is "60 e folds"?

But was this background microwave radiation emitted at the time of the start of the big bang or is it from the universe itself "currently" radiating in the microwave region of the electromagnetic spectrum because of the universe's "current" temperature???

Has space expanded that much??? What rate of expansion of space has occurred as a function of time since the BB started? Is it still expanding?

How can the universe be around 96 billion light-years in diameter, since it is supposed to be just over 13 billion years old, this would require the average expansion rate since the big bang of more than the speed of light, i.e. expanding at an average rate equal to the speed of light would result in a diameter of about 27 billion light-years, not 96???

There are things about cosmology that I just don't understand! Microwave Background Radiation is one of them. We are told that this is an extremely uniform residual from the Big Bang and that it indicates that the early universe (before stars formed) was extremely uniform. How can it be as uniform as reported, don’t stars, galaxies and even planets (like Jupiter) emit radiation in the microwave band? Wouldn’t microwave radiation emitted by the Big Bang at the time traveled far beyond us ages ago??? If they are talking about a “current” (more or less) afterglow from the universe, i.e. thinking of the entire universe as a Black Body Radiator as it has cooled since the start of the BB, the same question above still applies and also what exactly is the source of this “current” microwave radiation???

If as you say, the universe has been accelerating for the last 5 billion years, this would result in a higher velocity of expansion profile during those 5 billion years than in the previous model, so that has to result in a difference. The universe would take less time to get to its current size than in the old model.

My reasoning is that prior to the discovery of the accelerating expansion, the model would have had deceleration from the end of inflation until now, resulting in lower velocity of expansion as a function of time. With the discovery of accelerating expansion, the velocity of expansion would have been increasing with time and would thus have taken less time for the universe to get to its current state (size), i.e. it must be younger than in the previous model???

If it is correct that the expansion of the universe is accelerating, it seems that this would imply that the universe is not as old as previously thought? This would lead to the conclusion that the most distant galaxies are not as far away as we previously thought, obviously they can not be older than the universe itself? Do they have a model for the rate of expansion as a function of time post the above discovery, i.e. has it been accelerating ever since inflation?

Thanks, that helps a bit, but how did Kepler figure out the orbits? I am sure that the book I ordered will have a bunch of stuff on Kepler, etc. It is called "The History of Planetary Astronomy, Part B: From the Renaissance to Astrophysics".

Oh, let's not get into philosophy please.

Exactly how did astronomers before Newton come up with all of the values for the various characteristics of the solar system bodies, i.e. orbital parameters, mass of the bodies, etc, so that they could predict the motions of the planets and their moons back then? There wasn't much that they could directly measure! Exactly how did Newton come up with his Laws of Motion and his Law of Universal Gravitation? How did he come up with a value for the gravitational constant "G" in F=GMm/r2, r2 is actually r squared? For the surface of the Earth, GMm/r2 = mg, where "g" is the acceleration due to gravity on the surface of the Earth, M as the mass of the Earth and r is the radius of the Earth. The small m's cancel out so you get GM/r2=g or G=gr2/M, but you need to know M, r and g to calculate G. How did they come up with values for all of the variables? I have ordered a book that will hopefully shed some light on my questions, but it would be against the rules to link to the Amazon page selling it.

I think it is mostly to do with the "romantic" idea that Mars is a lot more hospitable than the moon and that we could eventually Terra-form Mars into a Second Earth, where it would be a wonderful place to live. Mars has long had a special place in our imaginations. I don't think that most people realize that Mars is almost as inhospitable as the Moon, i.e. that the atmosphere is very thin, that on the surface of Mars we would have to wear pressurized spacesuits, that we would have to live in pressurized habitats, that the surface is bombarded by solar and cosmic radiation, and that most of the planet is below freezing all of the time. Mars being so much farther away than the Moon increases the logistical challenges immensely. The only plus I can think of for Mars is that there appears to be vast quantities of frozen water ice just below the surface. A colony on the Moon would be easier and a lot cheaper, but I guess it all comes down to what the long term purpose of the colony is.

What have been the problems along the way and what are they currently working on?

I am interested in the history of astronomy, most particularly how did astronomers over the last few hundred years come up with estimates of the mass of all the solar system bodies, i.e. the Earth, the moon, the Sun, the planets and their moons? And also all the distances and orbital parameters. It seems to me that they would have had to know at least some of those parameters in order to calculate the rest. I am interested in the whole process that they went through over the the last few centuries. Do you know of any books or websites about this?

If we assume for a minute that there is something wrong with the current thinking that the expansion of the universe is accelerating and assume that it is in fact still decelerating and will eventually stop and then begin the Big Crunch, the Big Bang in reverse, at the end of the Big Crunch could some fundamental instability be reached that would trigger another Big Bang? If this were the case then "start of Big Bang to end of Big Crunch" could represent just one cycle in an infinite series of such cycles, such that the universe, in one form or another, has always existed and will always exist? Meaning that there was no beginning and there will be no end, and time is infinite in both directions. No need for a creator or anything like that.

If we assume for a minute that there is something wrong with the current thinking that the expansion of the universe is accelerating and assume that it is in fact still decelerating and will eventually stop and then begin the Big Crunch, the Big Bang in reverse, at the end of the Big Crunch could some fundamental instability be reached that would trigger another Big Bang? If this were the case then start of Big Bang to end of Big Crunch could represent just one cycle in an infinite series of such cycles, such that the universe, in one form or another, has always exists and will always exist? Meaning that there was no beginning and there will be no end. No need for a creator or anything like that.