Astrophysics August 20, 2018

By Mark W Gura, CW Brown, and Nina Rose Marina

An old meme which you are probably used to seeing says:

When you wish upon a star, you’re actually a few million years late. The star is dead. Just like your dreams.”

                     (new version of the meme)

Upon closer examination, this old meme doesn’t make much sense, so we changed it a bit above.

If you see a bright object falling in the sky, it is not a star even though some may call it a “shooting star.” They are rocks or dust particles that hit earth’s atmosphere from space. They are meteors. Stars do not fall.

Let’s assume that someone does wish on an actual star. Stars are the stationary objects that we see in the night sky. Those bright points of light that we see as we look into the dark abyss are actually exploding balls of gas, mostly hydrogen and helium. They are nuclear furnaces that make new atomic nuclei from pre-existing nucleons, primarily protons, and neutrons through a process called stellar nucleosynthesis. We can see them here on earth because they burn so bright and we are able to see their light.

Our sun is also a star, but the reason it looks so much larger and brighter than the other stars is that it is located closer to earth (approx. 92.9 million miles away, depending on the elliptical orbit). When we see our sun directly, it’s light drowns out the light coming from all the other, smaller stars, so this is why we only see the other stars at night when our location on earth has turned away from the sun.  

At times, stars flicker. Space is a huge landscape that seems like nothingness and emptiness. The stars that we see at night are incomprehensibly far away. Some are so far away that the light that shines from them took hundreds of thousands of years, or millions of years to travel from the location of the star to reach us. Keep in mind, light travels 9.5 trillion miles in a year, this measure is referred to as a “light year.”  

When you look at stars, the light that you are seeing might be millions of years old or older. It left that star at some point in the past. During that time, some of those stars might have reached the end of their life cycle. They might have already died, burned out and stopped shining. You are time traveling back to a light that once existed and has now changed, and this is amazing to think about.  

Imagine if that light was a picture of you, beamed to someone to some distant planet and it took that picture 186,000 years to travel through space to some far away planet. The recipient would eventually see your picture, but you would no longer exist. Your entire world would have ended 186,000 years ago.

These observations are factual and are based on observable data that can be perceived, measured and confirmed. However, there are some things about our Universe that we do not yet know. For example, one of the most exciting problems in physics today is the fact that there is far more matter in the Universe than we can see. We keep finding evidence for more matter, and we have an idea of how much it would take to eventually stop the expansion. The motion of stars in galaxies and the motion of galaxies in clusters imply that there is about ten times as much mass in the Universe as in the luminous objects we can see. The indirectly observed non-luminous matter is called dark matter. Why is dark matter a problem? For one thing, we do not know what it is. It may well represent 90% of all matter in the Universe, yet there is a possibility that it is a completely unknown entity—a stunning discovery, once we learn what it is. Dark matter has implications for particle physics. We do think that it is an early component of our Universe. It may imply that the Universe contains neutrinos that have smaller masses than expected, or that there exist unknown types of particles in the Universe, and our research into dark matter may answer these question, but we need to learn more. Unfortunately, whenever there is an unknown, some people, especially religious types make hypotheses that sound like facts.  

It might strike you as odd that rationalists, atheists, and agnostics are pondering life, death, dark matter, and travel through time, but atheism is just skepticism of assertions which do not prove supernatural claims made about gods. As long as we label hypotheses as hypotheses, facts as facts and do not delude ourselves into thinking that faith is anything more than an opinion, this too meshes with our atheist outlook. Hope is a good motivator to our well being and wishing on stars can help make us feel better, keep wishing on stars, enjoy life and the wonders of the Universe, just don’t base beliefs on feelings.  


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  • TinnyWhistler

    “Unfortunately, whenever there is an unknown, some people, especially religious types make hypotheses that sound like facts. ”

    Meh, this is true of everybody and is all over the place in science. IIrc, black holes started as fun solutions to Einstein’s field equations and most “evidence” up until really recently has been very much “Oh, hey, this could support the idea of black holes!” rather than “here’s the thing I found one.” Despite that, black holes have been talked about as pretty much fact for a loooong time.

    I’m not saying that’s a wrong approach. Much of modern physics has arisen in more or less this fashion. But being picky with our semantics and dickering about whether it’s still technically a hypothesis because X goalpost hasn’t been met isn’t useful. It’s more productive to full steam ahead with whatever and be willing to modify or throw it out as necessary. And it’s more fun.

  • Mark W. Gura

    @tinnywhistler:disqus. The attitude that distinguishing between words such as “hypothesis” and “facts,” is not “useful,” (as you say) is exactly the problem. Religion has now convinced billions of people that Christ rose from the dead, for example, as if this was a fact, when in realty there is not one incontrovertible piece of evidence to support this feeling or hypotheses as a fact. This is merely a religious opinion that is fervently held by many people.

    It’s time that humanity start to distinguish between reality and mythology. Truth is fun. Religious mythology made to look like fact is not. Science labels information as fact and hypotheses more often and more correctly than religion does, every day of the week. This is what science is, it’s a mechanism that helps us to understand reality. Religion is merely a set of beliefs. Faith is merely opinion.

  • TinnyWhistler

    See, my gut reflex is that you’re advocating for absolute certainty before talking about something as fact. I hope that’s not what you mean because that’s silly and leads to either 1) horrific ego problems and refusal to let go when one’s inevitably proven wrong about something or 2) complete waffling and perpetual “what’s the point I guess we’ll never know”

    My point is that there’s no usefulness in getting into arguments about whether or not something like the evolution of single celled organisms to humans is “hypothesis” or “fact.” If you wanna be anal about it, it’s totally a hypothesis. It’s not something that’s (so far as we know) directly testable or observable. It also happens to be a easily inferred conclusion from the best darn theory for how life’s existed over time that anyone’s come up with and hand-wringing about the fate of Evolution as a concept because minutia aren’t testable only discourages people from using the rest as a framework for looking at how life changes. That’s what bogs down the “macro vs micro evolution” people.

    Huge areas of science obviously do not deal with certain “facts.” Anything historical is one example. Most of astronomy’s another. Rather than using “fact” as some sort of altar, better to say “this is the way it is so far as we know” and move on. If that’s enough for someone, great! If it’s not, remind them that nothing in science is certain and invite them to go look at the evidence and explain how an alternative might explain that evidence better.

    Concluding that Science is The Truth is no good. That’s how we get people like Hoyle who rejected the Big Bang because it conflicted with his Truth.

  • Mark W. Gura

    It is useful for people to be able to distinguish between what is most likely unshakably true versus faith-based ideas that have no evidence to support them. This is the difference between science and Christianity/religion. Facts have been thoroughly tested and confirmed by multiple credible sources. Religious faith in supernatural things has no evidence to support it, whatsoever.

  • TinnyWhistler

    All testing of facts requires assumptions, some more than others. There’s no point in trying to construct your beliefs against things that are “unshakably” true because that way lies either delusion or insanity when it comes to actually getting science done. It’s all a balance of probability. What you need to do is figure out what’s “good enough” for you and move on with your life. Pretending that your line in the sand isn’t more or less arbitrary is just setting yourself up for denial, like Hoyle.

    Even the “thorough testing” of scientific facts usually comes down to probability. That’s what p-values and error calculations are all about. Collectively, we’ve all more or less agreed where that magic line in the sand is between “significant” and not, but that’s literally all it is. It’s not even consistent between fields.

    All science can give you is a “best guess for now” regarding how the physical universe operates. Pretending it’s more than that makes it no longer science but a religion of your own creation.

  • Mark W. Gura

    Are you equivocating facts and opinions?

  • TinnyWhistler

    Not intending to, please point to what I wrote that makes you think that and I’ll clarify 🙂