You know that gravity falls off as the square of the distance, right?

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So if the object gets twice as far from the earth (1/4 gravity) yet it's only slowed down 5% then it'll never fall back, although it's slowing the entire time.

[EDIT]

Play with some magnets a few minutes.

I've tried explaining this before to people but those who never took calculus have a hard time picturing infinity.

If there was just the Earth and another object at a huge distance from each other, the object would eventually hit Earth at 11.2 km/second. What would happen if you fired the object at Earth at 1 km/second instead of simply allowing it to "fall"? (And also somehow miss Earth or allow it to pass through?) Then it'd arrive at the equal distance on the other side, once again traveling at 1 km/second.

Before this thread I've never considered the term 'heat death' to be ambiguous.
I've heard/misunderstood, that randomly particles with their anti-particles are spawning and dissappearing all around. Would that count as making mass?

Actually, you should be able to use 1/x^2.

Again, xkcd to the rescue:
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Haven't observations shown the speed to be increasing? That's what my Astronomy professor said last semester.

That doesn't seem like very much evidence to support the attitude of complete surety my Astronomy professor had. He made it sound as if there was no doubt that the expansion is accelerating.

Within reason, yes.
I would say that the big bang is on less shaky ground than the accelerated expansion of the universe is.

That's not saying that I necessarily don't believe the measurement or the interpretation, but I'm not convinced it's as solid as its sometimes made out to be. There are people who think that stellar astrophysics is all textbook-standard, well understood and essentially "done". This is not the case, but compared to the level of understanding we have about cosmology, it is much closer. So compared to other things we know about cosmology, assuming that SNeIa are "standard candles" is perhaps not doing so badly. When taken on its own, it's a bit less solid.

Yes, but in degrees.

If it turns out that the SNeIa data can be interpreted without needing accelerated expansion of the universe, I would not be shocked. It would make the universe a bit less weird too. When you get down to it, we can't really say that the conventional interpretation is the only reasonable one. The idea that SNeIa are standard candles follows from a simple and straightforward calculation of what we think they are. No one has done the detailed calculation, because there are many uncertainties associated with that, and we don't know that there are no anomalous SNeIa (actually, we do know that there are and people have done some detailed calculations, and indications are that they are probably not standard candles).

If data shows up that disproves the big bang model, I would be quite surprised. Properties of the big bang model have been extensively tested and predictions have been verified to a large extend. We don't know a great deal about the early universe, but the big bang model itself seems very well tested. Any model that were to replace is will have to converge to the same late-time evolution as the big-bang model (not saying whether that's hard or easy; it may be quite easy or it may be quite hard, I don't know) and then one question I would have is how essentially different it is.

If data shows that Newtonian gravity is wrong, I would be quite shocked. This is so well tested and verified that if it were disproven, the entire construct of modern physics would come crashing down.
Note that when I say wrong I do not mean not applicable. Newtonian gravity cannot explain the orbit of Mercury. Not because it's wrong but because it's a weak-field approximation to general relativity (in other words, it's an effective theory) that is not applicable when the field strength is not weak. When I say wrong, what I mean is that it gives the wrong answer in a situation where it should otherwise be valid, based on previous experiments and observations (and for anyone who has heard of MOND, Newtonian gravity has not been verified in the regime where MOND is typically applied).

As I understand it, Pluto is not an example of a changing model or theory; just a change in definition of what it means to be called a 'planet'. The technical meaning of the word 'planet' was tidied up a bit to be more consistent, that's all. I don't think there has been any recent changes in our physical understanding of Pluto or anything related to it - at least not recently.

But yes, no scientific theory can be absolutely 'proven' to be true... but we can be pretty darn confident about many things - confident enough to bet our lives on them, which we frequently do.

Sorry, maybe I used the wrong term. But I thought "model" would fit. Given its the model of our view of planets and our solar system that changed.