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Random Astronomy Facts

Entry 1545, on 2013-06-21 at 12:20:48 (Rating 3, Science)

When someone wants to describe a number as being really big they often use the word "astronomical", presumably because astronomy involves so many big numbers. Big numbers are cool in themselves but more interesting when the significance of big numbers can be used to make a more relevant point. So that's what i am going to try to do here, in my next instalment in my "random facts" series, which will probably be slightly less controversial than the last one!

One of the first questions people ask about the universe is how big it is. I will answer this question through the use of some of my random facts from my "Astronomy Random Facts" file (as explained in the entry "Random Environment Facts" from 2013-05-20).

Fact 1: There are 5 times as many stars as grains of sand on every beach on Earth. (source: Infinite Monkey Cage podcast, 20 Jun 2011)

Discussion: The IMC podcast is (was) hosted by well known astronomer Brian Cox so you would expect it to have a certain amount of credibility. But this number varies greatly depending on the source and method used to do the estimate. Some estimates suggest the number of grains of sand and stars is about the same. But either way, that is a lot of stars.

Remember that stars are huge balls of glowing plasma, just like our Sun. The Sun is 1.3 million times bigger (in volume) than the Earth and many stars are much bigger than even that. A star called VY Canis Majoris (a red hypergiant) is often quoted as the biggest known. It's volume is almost 4 billion times bigger than the Sun or 7 thousand trillion times bigger than the Earth!

Plus the distance between stars is huge. Even in our galaxy the distance between stars is 50 million times bigger than the size of the star itself. And stars are grouped into galaxies where the distance between them is generally very large (millions of times greater than the distance between stars).

So, in summary, the universe has a vast number of really big stars separated by huge distances. So yes, the universe is big. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. - Douglas Adams, The Hitchhiker's Guide to the Galaxy

Fact 2: If you attempted to count to stars in a galaxy at a rate of one every second it would take around 3,000 years to count them all. And fact 3: The Hubble Space Telescope (HST) site estimates there is hundreds of billions of galaxies in the universe. A recent German super-computer simulation estimates that the number may be as high as 500 billion.

Discussion: Just to reinforce the number of stars out there, this is the same information presented in a different way. Again, the number is an estimate which varies greatly. The only thing which is certain is that it's big!

I often wonder what people with "human-centric" worldviews think of this sort of thing. For example, the Bible strongly implies that the Universe is here for our benefit, yet we only experience a tiny fraction of it and practically the whole Universe is unsuitable for life as we know it. Why? How can that possibly fit in with a human-centric belief system?

Fact 4: It looks like we live in a flat universe where the total energy is zero.

Discussion: To many people this seems bizarre. How can the Universe have zero energy? After all, there are all those stars and other high energy phenomena, aren't there? Yes, there is a lot of energy in the Universe but there is a lot of negative energy too. Gravitational energy is always stated as negative and it exactly balances the other forms as far as we can tell.

Is this merely coincidental or a side-effect of the measurement techniques, or is it something fundamentally important about the Universe? We don't know for sure but it is interesting to note that something with near-zero energy can easily be created from a vacuum with no underlying cause according to quantum physics. Perhaps the whole Universe is a vacuum fluctuation.

Fact 5: Sun leaks 7 billion tonnes of coronal mass every second into space. And fact 6: The Sun would only burn for about 5000 years if it was made of coal.

Discussion: Stars like our Sun are truly mighty objects. Every second the Sun loses billions of tonnes of it's mass into space yet it has been doing that for billions of years and that has barely made a difference.

But even with such a huge mass it could only produce energy at the rate it does for 5000 years if it utilised conventional combustion. The fact that it has "burned" for a million times as long yet has only used less than 1% of it's total fuel shows how incredibly efficient nuclear fusion is. And that's why we want to use this energy source (not quite the same but very similar to stars) for power production on Earth.

Fact 7: At its closest approach to Earth, Mars appears about as big as a tennis ball viewed from a distance of one and a half miles (two and a quarter kilometers).

Discussion: When I used to teach astronomy to the public there were two responses I commonly got when viewing the sky. The first was the delight that people could actually see those objects (especially Saturn) which they had only seen in books. And the second was disappointment in the image size and clarity we often had. The fact that we were observing from inside a city with a lot of street lights and heat sources didn't help, of course!

But observational astronomy is just inherently difficult. Apart from the Moon everything is too far away to make detailed observation easy. Even the closest objects like Mars (technically the third closest large body after the Moon an Venus) is very small even in large telescopes. When I taught astronomy we didn't have the HST photos we do now so expectations weren't quite as high. It must be a lot more difficult now!

So Mars is very small and it's sometimes difficult to see much more than a small orange disk, but what about genuinely distant objects? What about the closest star? Well that is about the same size as the Sun so it is about 100 times the diameter of Mars. That means that if Mars was a tennis ball, the star would be 6.5 meters across (about 20 feet). But the star is 40 trillion kilometers away compared with a mere 40 million for Mars. That is a million times further.

So the star is a hundred times bigger but a million times further away making it appear 10,000 times smaller. And that's the closest star! In effect this means that stars tend to be just points of light in even the biggest telescope. The damn Universe is just too big to be convenient!

Last fact: Virtually every atom in your body (other than hydrogen) was created in the core of an exploding star over five billion years ago.

Discussion: As Carl Sagan said: we are all star stuff.


Comment 2 (3577) by OJB on 2013-06-21 at 16:20:42: (view earlier comments)

Well I did say that numbers were fun but I wanted to explore the wider issues! I think there is inconsistency because the Bible treats the Universe outside of the Earth almost as an afterthought. How many days did God spend on Earth-related stuff and how much on the rest of the Universe?

Humans aren't necessarily insignificant. As far as we know we are the only example of "intelligent" life. Of course that might only be because of our ignorance of the real situation, or lack of intelligence!

Here, we get back to the old problem with most arguments involving religion. If the Universe was small we would argue God was being efficient. Since it's big we argue God is demonstrating his extravagant power. You can twist the facts to fit any interpretation of god, simply because god is a man-made myth.

Are you saying our inability to explain the Universe now is the same as it was 3000 years ago? How bizarre!

The fact is that we know material can be created literally out of nothing and literally for no reason as long as the total energy is small. This is an observed fact. I made it very clear that extending the idea to the whole universe is highly speculative but until we find a theory encompassing both relativity and quantum physics it will probably stay that way.

If you think everything with a beginning has a cause then you're just plain wrong. And if you think that material can't appear from nothing then you are also wrong. Plus, if you think an idea based on observed quantum phenomena is a faith claim then I'm sorry, but your'e wrong again!

Maybe you should spend less time on those creationist sites and a bit more on those based on reality instead! :)


Comment 3 (3578) by Richard Coulbeck on 2013-06-22 at 13:52:38:

Thanks Owen - Appreciate your reply. Can I ask for clarity? Please can you explain how there is inconsistency if the Bible treats the universe 'almost as an afterthought'. You must remember to assess for inconsistency 'using the view in question' not from 'an alternative' view. i.e. IF God really does exist, then what real obligation is there to devote anymore txt to the rest of the universe? IF He exists, then your only claim is that God hasn't met your personal expectation. Fair enough.

Similarly using your view to assess for inconsistency, again I ask for clarity of what you said. How exactly (in your view) are humans not completely insignificant, the briefest of purely physical accidents on the tiniest 'pale blue dot' in the famous 1990 picture used by Carl Sagan? Of course in the biblical world view, we are significant, and valuable. Don't just respond by saying that's purely our invention to make us feel significant (fine - heard it all before) - answer the fair question of consistency - as viewed from within your world view.

No - I think you know very well I wasn't saying our ability to explain the universe is the same as 300 years ago. Our (you mean sciences) ability to FULLY explain it, is however pretty much the same - it either can or can't - currently it can't, simply because it's (currently) too big.

Please by all means direct me to the sites that have reliably observed and documented matter created literally out of nothing. I think you find that those sites refer to incredibly complex scientific experiments where rather a lot of 'intelligent design' (LOL) has already occurred to create the conditions to make an observation in order to assert this claim. That is a rather strange idea of 'nothing'. Or they may refer to hereto unobserved (ie purely theoretical calculations), based on the same highly 'designed' experiments. True - that of itself, doesn't make them obviously false. It just puts them in the same 'category' as faith (by all reasonable definitions of the word).

So, if i go to your house and knock on the door - I assume I can expect you to ignore the knock knowing that it may have occurred 'spontaneously' with no cause. It's happened so often? That new Porsche in your garage - I want to be around when you tell your family that 'hey it just appeared with no cause whatsoever'. Really? - these ideas are fantastically theoretical, but quickly break down in the real world, where we have no experience of it at all.

Sorry any others folks - for detracting from the (cool) astronomical facts (thanks for them), but Owen did ask for these other discussions, in his post.



Comment 4 (3579) by OJB on 2013-06-22 at 21:11:14:

My original comment was about the Bible, not the idea of a generic god. It is very obvious that the writers of Genesis had no idea about what the Universe is really like, including the relative insignificance of the Earth.

As far as we know humans are the only form of intelligent life in the Universe. Many people would say that it is unlikely that we are really the only intelligence, but at the very least life seems to be rare. That makes us potentially significant.

Either you can or you can't! Really? Surely you don't really think that. We can never explain anything fully but we know a lot more about many subjects now, including cosmology, than we did in the past. That's like saying you don't want to use modern medicine because we don't fully understand disease. Good luck with the leeches instead!

Have a look at this Science Blogs entry. Also there are quantum fluctuations and the Casimir effect. Remember I said in the beginning this stuff is highly speculative.

Complex objects like a car would not appear spontaneously because they have a lot of mass/energy, but low energy objects appear all the time. Remember this started off from the interesting observation that the total energy of the Universe is zero. See the possible significane of that?

You are right to question these things but you should be prepared to accept these possibilities if there is some validity to them. You should also ask yourself why you reject these ideas instead of other counter-intuitive science. But we all know why, don't we?


Comment 5 (3580) by Anonymous on 2013-06-26 at 12:28:14:

Have either of you read A Universe from Nothing: Why There is Something Rather than Nothing, by physicist Lawrence M. Krauss. He explains many of these concepts there.


Comment 6 (3581) by OJB on 2013-06-26 at 14:01:57:

Well of course *I* have read that book. Not sure about Richard though. I think his reading on the subject might come from a slightly different source. I think he's more interested in a religious perspective rather than a scientific one. Richard, if you read this comment and I am wrong (you have read Krauss's book or something similar) please correct me.


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