Archive for the ‘astronomy’ Category

How Many Universes?

January 15, 2010 Leave a comment

The consequences of the anthropic principle continue to worry me. More specifically I cannot understand how the universe seems to be so finely tuned that it allows life to exist. Its not the fact that planets exist, or even stars, although those are important. Its more the really basic stuff, like the universe existing for billions of years, or that the proton is stable, or that objects such as stars and planets can exist because the values of various forces are just right for that to happen.

The history of science, and of astronomy in particular, has been a continual progression of discoveries which make our place in the universe less and less important. We thought humans were a special creation but evolution showed we weren’t. We though the Earth was the center of the universe but the heliocentric theory showed it wasn’t. We though the Sun was the center of the universe but the discovery of the structure of the galaxy showed it wasn’t. We thought the galaxy was the whole universe but observations showed that there are billions of others.

So there seems to be nothing special about us, or our planet, or our star, or our galaxy. It just happens that out of the trillions of planets out there (although I admit we only know about a few hundred so far) that Earth is well suited for carbon based life to exist (and I think that’s the only type of life which can arise naturally – but that’s another story).

So what’s the chances of Earth being as good as it is for life? First, let’s just say that its not that great – the fact that 99% of species which ever existed have become extinct shows that! Major global disasters such as asteroid, meteor and comet collisions, huge volcanic eruption events, and major climate variations show that Earth is far from ideal for life. But it is good enough.

So let’s say the chances of a planet being “good enough” are one in a billion (a totally arbitrary number I admit, but it doesn’t matter too much as I hope you will see). If Earth was the only planet in the universe we would say we are very lucky that the right formula has arisen at all (the formula involves mass, orbit, axial tilt, temperature, composition, gravity, etc) but if there are trillions of planets then its inevitable that many will be “good enough” and there must be a huge number which are actually better than Earth!

So that explains the planet – and a similar argument applies to the star (our Sun) and galaxy. What about the universe? Why do the basic laws allow stars and planets to even exist? The tempting answer is to apply the same logic as I have for the planet and say that there are a large (maybe infinite) number of universes and ours just happens to be one with good (but not perfect) conditions for life to exist (just like the Earth provides good but not perfect conditions for life).

The only problem is that we know other stars and planets exist but we are a bit less certain (and that’s a real understatement) about other universes.

At this point we really get into the realm of philosophy more than science. It would certainly be nice if there was an infinite (in time and space) multiverse which our universe is only a small part of. Universes could form with arbitrary laws and sometimes those universes would allow life to exist. Ours does, but there would be others where life also exists (probably in better conditions than in this universe too).

Some people (who maybe haven’t thought this through too carefully) might ask at this stage: but what are the chances of us existing in just the right universe? I would say the answer to that is 100% because that’s where we are. Its like a lottery winner asking “what is the chance of me winning” after they already won. That would be 100% but if they asked before winning it might have been only 0.0001% Only people who already have won (or exist in a “friendly” universe ask the question so the answer can only be one thing!

The whole question I have dealt with here is so big that there are theological implications. Many people think the fine-tuned universe we live in proves a god exists because the chances of all the laws and constants being just right are just too tiny to contemplate otherwise. If this was the only universe they would have a good point (although there are other possible explanations) but I think the multiverse theory answers the question better.

I only have one nagging doubt. If the multiverse creates all of these universes and only some are good for life, why do the “meta-laws” of the multiverse allow the creation of universes at all? (in fact the same argument could apply to a god) But, at this point, I prefer not to even think about that!

UFOs Identified

March 30, 2009 Leave a comment

Recently the British Department of Defence released its files on its investigation of UFO sightings. They took it very seriously but in the end the final result was inconclusive. That means that no one could definitely say that UFOs are visitors from outer space but they also couldn’t say that they weren’t.

That’s not really surprising because, in many UFO cases, there is not enough evidence to reach a reasonable conclusion. Lack of evidence usually means the phenomenon doesn’t exist but we can never be sure because its almost impossible to prove a negative.

Before I go any further I should clarify a few points. First, UFO stands for unidentified flying object. By this definition they certainly exist because there are flying objects which are unidentified. But many people think UFO means alien visitors and that is the definition I am discussing in this post. We also usually mean the alien visitors have visited Earth and they are responsible for the strange lights, alien probings, and other assorted phenomena.

I don’t think aliens have ever visited the Earth but I do think other intelligent life exists in the universe. How do I know that they haven’t visited us here? First, because if they had it would probably be more obvious; second, because the way life originates and evolves in the Universe means it might be still quite rare; and third, interstellar travel is just really hard.

So what are UFOs if they aren’t visitors from outer space? They are astronomical objects, atmospheric effects, aircraft, and various other effects, sometimes viewed under unusual conditions. And they are things we just haven’t identified yet. Its that simple.

Rockets Are Fun

March 7, 2009 Leave a comment

About an hour ago a Delta II rocket launched the latest astronomy mission, Kepler, into orbit and I watched, listened and received updates in other forms over the Internet. Rocket launches are always great spectacles: there’s the power and speed of the rocket; lots of noise, fire and smoke; and the ever present tension because of the uncertainty of success.

The Delta II is the second most reliable launch vehicle of all time – of 411 launches it has had only one partial and one total failure – so there was always a good chance the launch would be a success. But nothing can be taken for granted so its great to hear that everything went perfectly.

There are two cool things about this launch. First there is the rocket itself. The numbers are impressive. During the first part of the launch the rocket consumes a ton of fuel per second! After about 7 minutes its at a height of 100 miles, over 1300 miles away and travelling at about 15,000 miles per hour. Yes that’s 15 thousand. Pretty fast really, even for a fast car and aircraft enthusiast like me! For comparison, the fastest production car (the Buggati Veyron) can manage just over 250 miles per hour and the fastest aircraft (the SR71 Blackbird) flies at about 2,200 mph.

The second cool thing is the Kepler mission which has been put into orbit. This will fly in orbit around the Sun (not the Earth) but will follow the Earth around the Sun. It will be used to examine stars in the constellations of Cygnus and Lyra where it will look for subtle changes in the brightness of stars which will indicate planets crossing the star and reducing its total light.

Kepler has a 1 meter telescope and can detect changes in light of about 20 parts per million (meaning the star’s light drops by just 0.002%) which should allow detection of planets of Earth size or smaller.

Yes, rockets are fun. Missions like this, which have no “practical” benefit or monetary value are what science is all about. There are so many more pure science missions which could be launched but I suppose the reduction in spending on space science makes the missions which have survived budget cuts even more special.

Categories: astronomy Tags: , , ,

Life As We Know It

February 17, 2009 Leave a comment

Yesterday I blogged about the new stuff which has appeared in the area of astronomy over the last 20 years. I realised today that there are several other significant changes which I didn’t mention. These aren’t just things which interest astronomy geeks (or at least they shouldn’t be) because they should be really significant for anyone with any sort of intellectual interest in the world.

The most significant is maybe the discovery of exoplanets. Yesterday I talked about how complicated the Solar System had got with the new classification of dwarf planets and how many items are either in or are likely to be included in that group. But there is also the far more important discovery that planets are very likely to be ridiculously numerous elsewhere in the universe. In fact, we already know about 300 exoplanets (that is planets orbiting other stars).

Why is this a big deal? I mean, shouldn’t we expect that planets are numerous? If the Sun has 8 planets plus numerous dwarf planets, plus millions of asteroids, hundreds of moons and millions of comets, why shouldn’t other stars be the same? Good question. Logically other planets should exist and everyone expected they would, but proving they exist is actually really difficult.

Why is this so significant? As far as we can tell, planets are the most likely place for life to exist. This is because they have solid surfaces (at least Earth-like planets do), they usually have stable orbits and therefore stable temperatures and those temperatures can potentially be within the range that life can survive in. Also planets often have atmospheres and liquid water which we think are a likely requirement for life.

All of the above assumes I’m referring to “life as we know it” (that classic, and rather over-used phrase). OK, sure, that’s true, but there are good reasons to believe that life as we know it is likely to be the most common form of life everywhere (assuming life does exist elsewhere which itself is currently a completely open question).

Life on Earth is based on carbon but we think that is likely on other planets as well because carbon is the only element which bonds in sufficiently complex ways to make the huge complicated molecules of life possible. Those bonds are only stable at a narrow temperature range (let’s say 0 to 100 Celsius, just to make it simple) so we can also constrain the temperature life can survive at. Its beginning to look like “life as we know it” might have a similarity to just “life”. Of course, its possible that synthetic life might be created using advanced technology, and that might not be based on carbon, but I’m sticking to “naturally” occurring forms here.

So the significance of these exoplanets is that they might be places where life exists. I mentioned that the planets themselves are hard to detect. How would we detect a small part of the planet, like its life forms. It seems impossible. Well, maybe not…

If we extend the “life as we know it” assumption above we can assume that oxygen might be involved in the metabolism of life in most cases. That’s because oxygen is an abundant “heavy” element created in supernovae and is active enough to be a good source of energy production. It also has the advantage that it is so reactive that it tends to disappear quickly in a natural state where it isn’t being replenished by a life process.

So if we see oxygen on a planet it might indicate there is life there. Once we know a planet exists, spectrographic analysis becomes a possibility. I’m not saying its easy – it isn’t – but it is possible.

Planets are being discovered at such a rate that its only a matter of time before one very like the Earth is found. The current smallest planet is about twice as big as Earth because big planets are much easier to detect than small ones of course. The planet would need to be rocky and in a stable orbit around a main sequence dwarf star, like the Sun. It would need to be the right distance from the star so that it was the right temperature. And it would preferably need to have an atmosphere and/or ocean. In those circumstances I would be surprised if life didn’t exist.

My prediction is that within 5 years we will have several candidate planets which are showing signs that life exists. We just won’t be able to prove it beyond doubt which will, no doubt, be very frustrating!

Categories: astronomy Tags: , ,