Darkchilde

Back at RDF we had a debate section that worked well, and we had some nice debates. Most debates of course were science vs. religion, we even had one creationist try and debate one of our evolution experts, about macroevolution not happening [a lot of laughter that one]. I think that creationist has posted here too, he goes by the name of Robert Byers. [if you go to FSTD, there are plenty of quotes from that one. A lot of laughter from his posts.] We did have 1 or 2 debates always going. Now, at RS, we do have a debate forum, and since we have had some experience with such debates, we are waiting for people to start one. The format for the debate is usually as follows: 10 posts each, one week max for each user to post their answer, and there was at least one moderator for the debate. The moderator made sure that the posts are in line with the FUA, and that they are relevant to the debate, as well as making the decision of who wins the debate and why. Also, we had a commentary thread where people could go and discuss the debate, but the debaters themselves were told not to go and look at that thread, and usually debaters did not use that thread. Posts for the debate have to be approved by the moderator before they can be seen by everyone else, including the second debater. If I have forgotten something, I will come back on this.

This is not what happens, though. If the star exploded then it would a white dwarf star, a pulsar, a black hole, something. Yes it does. I can't say if we see it today or not; it depends on our distance now from the star. If we are receding from the star then there will be a redshift from its light. If we are approaching it, we will see a blueshift. Even though we cannot reach the speed of light: if 2 million years ago, the star was at a distance of 1 million light years, because of the respective speeds and travel that both our systems have done in the galaxy we may be closer or farther away from the star than we were 2 million light years ago. So the light that started 2 million light years ago may or may not have reached us yet. In 2 million years, the Solar system has moved about 1% of its orbit around the galaxy's centre! The sun has moved about 1500 light years around the galaxy in 2 million light years (if my rushed calculations are correct). So, if we take the other star to be stationary, then the light from that supernova may need more time to reach us (about 1500 years) or we may already have seen that (1500 years ago). Or if the star is at the exact same distance as it was nack then, then the light would be reaching us now. There are also other considerations, such as gravitational lensing, and so on, and so forth.

We have the explosion of the star 2 million years ago. The star's distance at that point in time was 1 million light years from the Earth. What is the distance from the star now? What is the relative movement of the Earth-star system? Are we approaching the star, so we are less than 1 million light years away from it, in which case, we have already "seen" the explosion, or are we receding from the star in which case, we are farther than 1 million light years away from the star, and the radiation from the explosion has not reached us yet.

Force is applied to objects; gravitational force has a meaning when applied to a mass. Gravity is actually a field; not a force per se. The Earth produces a gravitational field, and this field is what attracts my body. So, gravity is not a force but a field. It becomes a force when the field interacts with a mass, and then a force is exerted on the mass which is equal to F=mg where m=mass and g=acceleration of gravity.

Thanks. Book looks interesting, I already have Cosmology by Weinberg to study, but will check out Liddle's book as well.

My question is this: was there an amount of helium formed after the Big Bang, along with hydrogen? Or is all helium the product of nucleosynthesis at the cores of stars? Can you please point me at sources about this?

First of all, it is not radius. Radius is for circles, and planetary orbits in our planetary system are elliptical. Which means that there is an aphelion (the greater distance of a planet from the Sun) and a perihelion (the minor distance of a planet from the Sun). For the Earth these distances are called apogee and perigee. So, we cannot test the radius from the Sun. We can measure the distance of the Earth from the Sun at various times and determine the orbital path of the Earth around the Sun.

How about astronomy? What are the best journals in this area?

Hello, I am 39 years old, and my main interest area is astronomy/Quantum Mechanics/Mathematics. I have an MSc in Computer Science from Essex University, and currently studying with the OU, trying to improve my understanding and knowledge of science. This year I have opted for MST209 Mathematical Methods and Models, which I find very interesting especially with regards to differential equations. I also love science fiction, fantasy and horror in general. Grew up reading Isaac Asimov, Ursula K. leGuin and a few other Masters of SF and Fantasy. My interest in science was first instigated by Isaac Asimov and his Robot series, and then Carl Sagan with his wonderful Cosmos series. Used to be in love with that one, and every week was waiting for the next installment of his Cosmic Calendar. I am writing from Athens, Greece where I live and work currently.