Deep space and astronomy is a subject with a lot of far fetched theories that are bandied about by established researchers and theorists. Dark matter, curvature of space & time, billions and trillions of galaxies, parallel universes, expansion beyond infinity, big bang and the list goes on. Most of them seem far fetched and ridiculous to start of with, gain momentum and then slowly disappear.
Which theory (theories) proclaimed with great fanfare has now been debunked and shown to be absolute bunkum.
Know of any? Could we restrict ourselves to theories after 1950s. There were a heck of a lot of rubbish before that…like the earth is flat and at the centre of the solar system etc…which can be excused due to the prevalent lack of technology and communication.
Dark matter is not a “far fetched theory”, it’s a label that refers to an unsolved mystery: if you measure the amount of matter by their gravitational effect, and you estimate the mass of all the stars based on observed brightness, we get very different numbers. It implies most of the matter in the universe is “dark” - i.e. not bound in stars (and other objects that we can see). There are many hypotheses that attempt to explain this discrepancy, but I don’t think any of them rises up to the status of a theory.
Curvature of space-time and “billions and trillions of galaxies” are very real and measurable, there’s nothing far-fetched about these.
Parallel universe is not a theory, just an idea that sometimes gets bandied about.
I’m not sure what you mean by “expansion beyond infinity.”
Well, there was the steady-state theory back in the '50s and '60s, which postulated that the Universe didn’t have a Big Bang but was rather continually creating matter as time went on. The idea was the the continuous creation of matter would balance out the expansion of the Universe, leaving us with a constant average density of matter in the Universe. The steady-state theory lost a lot of its luster in the late '60s after the Cosmic Microwave Background was observed, though — it was much easier to explain in the Big Bang model.
True, but I don’t think it was ever an established theory, it was always one of the several competing hypotheses proposed to explain observations.
If we include situations like that, it wasn’t long ago that many astronomers thought gamma ray bursts occurred very close to us, within our own Galaxy and possibly very close to our solar system. Additional observations made it clear that they were actually at cosmological distances. (Although I think the truth sounds far more remarkable and far-fetched than the early hypotheses.)
There were a bunch of alternative theories to how planets are formed that have been replaced by the “nebular hypothesis”. It was actually a return of the nebular hypothesis; created in 1734 it had been thought to have been proven implausible long ago.
One quite recent change is the overthrow of the long standing assumption that gas giants would exclusively be found in the outer star system like they are in our system; instead, we have a proliferation of close-in “hot Jupiters”.
Technically, the existence of dark matter is a hypothesis. We observe a discrepancy between the motions of galaxies and the predictions of General Relativity. We hypothesize the existence of some heretofore-undetected substance that resolves this discrepancy. Alternatively, some physicists prefer to hypothesize a modification to the predictions of General Relativity. To my knowledge (and I eagerly welcome updates on this point) the data that rules out one or the other is not yet present.
This also is, essentially, a theory. I have seen parallel universes, in various forms, hypothesized:
To explain an interpretation of quantum mechanics
As a consequence of the infinite size of our universe
As a prediction of a theory of eternal inflation, specifically as an unintended but necessary consequence of having enough inflation to generate the universe we see.
As to the OP, I would nominate the Big Bang model, which inflation replaced. Specifically, it was initially theorized that the universe began in a spacetime singularity, which then exploded and expanded and cooled. New data about the homogeneity and isotropy of the observable universe presented problems for that theory, and inflation was invented to solve those problems.
So of the OP’s listing, Dark Matter is a hypothesis, Space-time Curvature, Big Bang and Expansion are consequences of the Theory of General Relativity, parallel universes are a hypothesis (though I’m not sure how you’d test it so maybe a conjecture or inferred fact assuming certain premises are true).
I’d be curious to know why the OP cares that hypothesis found to be wrong are discarded. Why would you keep them if they were?
There’s a ton of observational evidence for Dark Matter (wikipedia gives a list). Its a lot more then just galactic velocity curves, and while there are modified gravitational theories that can explain one piece of evidence or another without the addition of Dark Matter, no ones come up with one that can explain away all the evidence.
Dark matter first arose to explain discrepancies between observation and Newtonian physics.
Inflation is more of an extension of the big bang model than a replacement of it (though some inflationary models are very different from standard big bang theory)
Not since the 50’s but close to it: the Great Debate of 1920 between astronomers Harlow Shapley and Heber Curtis over whether “spiral nebulae” were nearby and part the Milky Way galaxy which covered the whole universe, or whether they were in fact distant “island universes,” of which our own Milky Way was just one of many. The latter proved to be true, of course; the “spiral nebulae” turned out to be the Andromeda galaxy, Pinwheel galaxy, Whirlpool galaxy, and so on. The prevailing view was that the Milky Way was the whole universe until the work of Edwin Hubble and others showed that our own Milky Way galaxy not only isn’t the entirety of the universe, it’s a tiny drop in the bucket among countless galaxies. This is such basic stuff now that it’s odd to think that it was the subject of intense debate among astronomers less than 100 years ago.
That Mercury was tidally locked to the sun (it IIRC has a day 2/3 its year).
That the astroids were a planet that broke up.
That the rings of Saturn were (a) unique and (b) made up of fairly thick fragments
That Mars had canals.
That Mars had green patches.
That light waves and radio waves travelled in an invisible “aether”.
I have a great Arthur C Clark book - ‘The Promise of Space’ - written late 50s-early 60s. It gives an excellent overview of gravitational problems regarding rocketry, orbital mechanics etc suitable for laymen like me.
However, at one point he is talking about Mars. He mentions the seasonal variations in the dark patches visible on the surface, talks about some of the previous far-fetched theories, and ends by saying (paraphrasing here) - ‘It’s obviously seasonal changes in vegetation growth, cannot be anything else, and so is really not worth arguing about anymore’.
One of the most ‘recent’ theories to fall back into favor is that the Moon was formed by an Earth/Mars-sized planet collision. It’s generally the accepted one now, with both the ‘capture theory’ and the ‘spun-off as a molten blob of Earth’ theory being disproven via computer simulations.
Kepler’s laws fit the orbits of the planets pretty well, all except for Mercury. It was hypothesized for a while that Mercury’s strange orbit was the result of another planet within Mercury’s orbit, dubbed Vulcan. No one could find it, though not for lack of trying. Eventually, Einstein published his theory of gravity that explained Mercury’s discrepancies, and the Vulcan theory was discarded.
Similarly, the whole reason Pluto was found decades before any other Kuiper Belt objects was that astronomers had predicted a massive Neptune-sized planet (“Planet X”) to be there, due to discrepancies in Uranus’s orbit. They initially thought that Pluto was their Planet X, but then were very confused to find that it was too puny to exert any noticeable influence on the other gas giants. This mystery held out until Voyager 2 gave a more accurate reading of the mass of Neptune, and the discrepancies disappeared.
It seems to me that predictions about the surface of Venus were one bad speculation after another, even among serious scientists. For example, it went through phases like “clouds means water, so the surface is either ocean or swamp” or “high CO2 means a surface covered with hydrocarbons” or “clouds and CO2 together mean extensive vulcanism, a surface covered with volcanoes and lava.”
Boy were these guys wrong when it turned out to look a lot like a stony Earth desert.