Pioneer Anomaly: New Physics or Bad Maths?

1972 and 1973, NASA sent two unmanned spacecraft on a one-way trip to the edge of the solar system and beyond, Pioneer I and Pioneer II. These two spacecraft were sent to take pictures of the gas giants and give us insight into their structure, they did their job, scientists oohed and aahed at the results, updated all the relevant textbooks, and moved onto the next big project in science. But because scientists are inquisitive, and care about the well-being of the Pioneer craft, they kept tabs on them, to make sure they stay fit and healthy. This was meant to be just a routine check-up every now and then, just to see how far they go, but physicists discovered something strange. The distance between where Einsteins physics predicted the spacecrafts should be and where they actually were was different. Somehow, the crafts where slowing down. Now, they amount of deceleration was very small, less than one nanometer per second per second, but this was enough for scientists to really consider revising physics books, because nobody could think of anything that would cause this extra deceleration.

For scientists, this was a prime time to witness a paradigm shift, something key to the process of science. Some may think that science is just a steady progress of learning about nature, but its not. It actually involves rapid changes of ideas most of the time, in so-called paradigm shifts. This is a stage in science which occurs when evidence comes up which is contradictory to current science. After new evidence shows up, there will be further investigation from scientists to try to figure out what is the correct model, if the first evidence is overturned, and science stays with the current theory, this is not a paradigm shift. When the evidence is confirmed and new evidence supports it, scientists will formulate a new model which accounts for this evidence, and this is known as a paradigm shift.

Paradigm shifts are very important to science, as they mean deeper knowledge of the universe. But a possible paradigm shift which turns out not to be one is good too, because it means that our current model is pretty good. Pioneer was worthy of study to find out if the physics textbooks needed a re-write.

For almost 30 years, there hasn’t been enough evidence to formulate a hypothesis either way, and it has been an unsolved mystery to science, often called the Pioneer Anomaly. But now, a team at the Jet Propulsion Laboratory in California have an answer. The team published a paper in Physical Review Letters in which they demonstrated that some electronic components on the craft where producing small amounts of heat, and the force imparted on the craft from this heat was enough to cause the deceleration. “I think it is solved for good” said lead author of the report Slava Turyshev.

Great! The mystery is solved. Just put this down as another proof of Einstein’s Gravity. As a good scientist, you should know that any result is a good result. Confirming evidence just means one more piece in the puzzle which proves our theories, contradicting evidence means new physics, which is also good.

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Could the laws of the universe be different?

Hello skeptics and other lurkers,

Today’s post again comes courtesy of a tweeter, who asked a question along the lines of this post’s title. This is a question which I have wanted to deal with for a while now, and I think that tonight is as good a time as ever for me to deal with it.

The laws of nature (as you should all know by now) are the laws which define the four fundamental forces we observe (gravity, strong nuclear, weak nuclear, electromagnetism) and the mathematical equations which describe these four forces. Most of the plight of modern particle physics is to find out as much as we can about these forces and equations, and see how it works out for the universe now, in the past and in the future, hoping to discover as much about our universe as possible, with the ultimate goal being to finish with one sum which describes all of these forces, the Theory of Everything (TOE). Last night I talked about string theory and the TOE, and this is one of the important parts in answering tonight’s question.

One of the most important ideas in particle physics is that, under extremely high energies, three of the fundamental forces (electromagnetism, strong nuclear, weak nuclear) can be united by one Grand Unified Theory (GUT) which describes all three forces. This theory has survived mathematical attempts at disproof and appears strong mathematically. This Grand Unified Theory is very important to particle physics. The hope is that, under EVEN higher temperatures and energies, this Grand Unified Theory can be combined with gravity to create the Theory of Everything. Gravity has always been a thorn in the side of physicists, and is actually the least understood and proven of all the fundamental forces, despite its obviousness in everyday life.

The hope and expectations are that gravity and the other three forces can be combined under higher temperatures to form one Theory of Everything. If it is true, as predicted by modern physics, then this has surprising implications for the four fundamental forces.

When the universe was born in the big bang, it was in a state of extreme heat, pressure and energy. Then it went under a process called ‘inflation’, where the universe expanded extremely rapidly (faster than the speed of light) and cooled extremely rapidly. There are two factors which are important in answering our question. 1. At the start, the universe was in a state of very high energy and heat, and 2. The universe expanded faster than the speed of light. Now, if there was ever a time in the history of the universe where the four fundamental forces would be combined, it would be right at the start.

Now, one hypothesis of a multiverse is extrapolated from this. If the universe went under rapid expansion while the four fundamental forces were combined, it could be true that, due to different parts of the universe being cut off from each other because of the speed of light, in different places, the universe could have cooled at different rates, meaning that the four fundamental forces could be different in those universes. Due to this hypothesis, it could be true that from one big bang, multiple universes could have been created. The definition of a universe is all of the things which can be observed, and seeing that these places are cut off from each other due to the speed of light, you have your self a multiverse, with different laws of physics.

This idea, like all multiverse hypotheses, has ramifications for the fine-tuning of the universe. It is one which is also hypothesized by accepted physics models, and is one if the easiest to accept, seeing that we know there must be much more out there than the observable universe.

String Theory – Science or Sermon?

Hello skeptics and others,

I recently came across a question on twitter which went as phrased “String Theory, Science of Philosophy?” and I thought, as I had not done much with string theory, that now would be as good a time as ever to tackle this question which comes up with string theory often. But first, a bit of background on string theory.

String theory is the name given to a set of sums which attempt to explain things about the things we observe in particle physics. It is basically the claim that the 3 spacial dimensions and 1 time dimension we observe in our universe, are the left overs and that there are possibly up to 8 other dimensions which are all just packed in very tight so that we cannot see them. To explain this to you, I will use the same method Stephen Hawking has done.
Imagine a plastic drinking straw. From up close, you can easily see that it is a three-dimensional object, with height, width, and breadth. If you back it up to a distance of a few metres, the drinking straw starts to appear as two-dimensional, with only length and breadth, you can no longer make out the depth of the straw. As you back out further to a distance of about 20 metres, you can only observe one dimension, it only has length, and you can no longer observe the width of the straw.

Now, the other 2 dimensions still exist, but you can only make out one from this resolution, so for all intents and purposes, the straw is 1 dimensional. The same is true with the hypothesized extra 8 dimensions of string theory. They still exist, but we cannot observe them because they have been compressed in so small. It is physicists belief that these extra dimensions, ‘strings’, carry along them the elementary particles which create the four fundamental forces, gravitons, photons etc. in the world of particle physics. String theory is also said to be the most favoured path for the elusive Theory Of Everything (TOE).

String theory often comes under attack for a few reasons, being that it makes no specific predictions about the universe, it is no different from other theories about observed phenomena and there is so far no test of the ‘theory’. These criticisms all have legitimate reasons behind them.

It is true that string theory makes no predictions and it is indifferent about what we are already observing in the universe. String theory has not been of any real use to us yet other than jobs for people to do the maths behind string theory. In that way (except the maths), string theory is just like creationism… it makes no predictions or offer a hypothesis to test.

However, I think that just because string theory has not provided any scientific worth so far, it is in no way something we should give up on. It is a theory which has held up to all that maths has to throw at it, so there are no real internal problems with it, but the real question is “Is this how reality really is?” and that question is a long way off. String Theory is a path worth following, as it could be of value to future scientists. At best it is still only a hypothesis… not a theory, and should be treated as such. But it is worth the time and effort to work with and who knows, it may cough up a test for us, and it is worth waiting around for.