Attitude and Tachyons

I received a question through Ask a High Energy Astronomer with such attitude that I wanted to slap the author. She said that she had asked an “Ask an Astronomer” service at NASA when she was a lot younger if dark matter could be made up of tachyons, and was disappointed when the answer was basically “no”. Luckily, she says, this answer didn’t dissuade her from pursuing physics. Now, as a 4^th year physics student, she’s dug up a paper (“Quasars as bubbles of dark matter: evidence for axion and tachyon matter in the Universe“) that says that tachyons are a dark matter candidate, so she asks us again if dark matter could be tachyons.

Well, didn’t I feel shamed? Um…no. In fact, I was kind of pissed off. Here’s what I wanted to put in the answer I wrote:

• As a 4^th year physics student, you have a network of professors to discuss things like this with. Why are you wasting our time? Our service is run by volunteers, and our time would be better spent answering questions from people who don’t have such a network. Get off your ass and ask one of your professors about this.
• Are you seriously presenting that paper as evidence that tachyons are a real contender for dark matter? The paper is not even in a refereed journal. In fact, it’s not in a journal at all. It looks like it was submitted to astro-ph as a note for others to read and respond to. That paper is about a theory that is not well-supported in astrophysics — the theory that quasars are not at cosmological distances, but are really nearby objects.

  Accroding to the author’s, Anatoly A. Svidzinsky’s, CV, most of his work has been in superfluids. The only astrophysical paper he has in a refereed paper is on radiation of neutron stars produced in a superfluid core. His other papers are in physics journals. Does this necessarily mean that his work will not connect to dark matter and perhaps show that quasars are not cosmological? Of course not. However, more observations need to be made before his hypothesis is given the same weight as other scientific explanations.

  So, we have an author dealing with a questionable hypothesis, proposing that tachyons are a dark matter candidate in a paper that has not been submitted to a journal, let alone a refereed journal. How reliable is this as “evidence” that tachyons really are a dark matter candidate?

• Tachyons? Are you serious? This is not Star Trek. We live in the real world. Tachyons were proposed as particles that would satisfy the requirements of something that could travel faster than light, but have never been observed. In fact, if they did exist, they would violate causality, which is one big reason physicists don’t see them as a real possibility. As a 4^th year physics student you should already know that just because a solution to an equation exists, does not make that solution physically reasonable.
• Are you suggesting that an honest answer from an astronomer could have turned you off from physics? If that’s true, then you shouldn’t be in physics to begin with. Science isn’t about getting the answers we want; it’s about getting at the truth.
• You’re a 4^th year physcis student…research this on your own, and figure out why our answer is still basically “no”.

My actual answer:

If you’re looking for a different answer this time around, you’re coming to the wrong place. This might surprise you, since, indeed, the paper you dug up does say that tachyons might make up dark matter. Why hasn’t our answer changed? Two reasons. First you need to consider the source of that paper, and second the nature of tachyons.

The first point is that the paper that you pointed us to is not in a refereed journal. In fact, it’s not published in a journal at all. Members of the astronomical community can upload papers to the arXiv archive without going through any kind of review process. The paper deals with a topic in astronomy that is not well-accepted (a claim that quasars are not really at large distances, but relatively nearby), and he brings up the topic of tachyons being a dark matter candidate in his abstract (an even less-accepted idea). Does that necessarily make his hypothesis wrong? No, but there needs to be more evidence to support his hypothesis before we’ll give it the same weight as other scientific explanations. You need to learn to look at your sources with a critical eye.

The second point is that tachyons have not been proven to exist. In fact, while tachyons satisfy the equations of relativity, they have never been observed. Just because a solution to an equation exists mathematically, that does not mean that it is physical. You can read more on tachyons on the following page:
http://curious.astro.cornell.edu/question.php?number=504

Does this mean that our answer to your question will never change? Not necessarily. If tachyons are demonstrated to exist, and they are shown to have properties consistent with dark matter, we might answer “yes, tachyons could be a constituent of dark matter.” Does this mean that we’re giving you a “wrong answer”? No.

Let’s say that you asked an astronomer a hundred years ago if there were other galaxies in the Universe. They would have said “no”. We now know that there are many, many galaxies out there. Was that astronomer wrong to say “no” instead of “I don’t know”? Certainly not. They gave an honest answer based on the state of their scientific knowledge. Science is not static. We constantly build on our knowledge, and as a 4th year physics student you should already know this.

Good luck in your future physics career!

Tags: rant, science