"Something out of nothing" and "started with an explosion" are wrong assumptions?

"Something out of nothing" is an ambiguous concept in the absence of an explanation of the term "nothing."   For example, so-called "empty space" is permeated by gravitational fields and the Higgs field; it is also filled with vast numbers of virtual particles that pop into and out of existence.  No informed person says that the universe "started with an explosion" because the expansion of space itself is not an explosion. 

Yes, wrong assumptions based on a misunderstanding of the science (and for big name creationists they continue to espouse these lies even after having been corrected numerous times).

Nobody except those ignorant of the science or those who wish to purposefully discredit its findings claims that the Big Bang was an explosion. The name Big Bang was coined as a derogatory term to discredit the early hypothesis but it stuck and now people get the wrong idea about it because they associate the word bang with an explosion. However, the actual science describes it as a rapid expansion of space, not an explosion. And it is based upon a mathematical model, so the rapid expansion is just a way of us trying to describe what the findings show us rather than a definitive explanation.

As for the "something from nothing" that is again a common creationist talking point that stems from a general misunderstanding of the science and is perpetuated by those who have been corrected and choose to keep spreading the lie because they can bilk gullible followers out of their money. The exact answer is that we do not know because the information we have does not tell us what was there at the start of our current perception of space-time. Mathematically we trace it back to a singularity, where all mass and energy were concentrated into a single point. In what world does :all mass and energy" mean the same thing as "nothing?" That seems like something existed and the universe expanded from that something.

We don't know what, if anything, came "before" the singularity, but that in itself is perhaps a meaningless concept anyway since space-time came into existence with the Big Bang, so if time did not exist until the Big Bang there is no such thing as "before." They can certainly hypothesize and test to try to gather evidence that supports a cohesive theory, but as of right now the honest answer is simply "we do not know."

You don't know anything about physics and you don't understand surprise you can make matter and anti matter with nothing but a **** load of energy 

Energy is nothing physical 

It's an extrapolation from a few decades of observation to billions of years and assuming an entirely mechanistic past. It's not surprising it's in error; a big one.

Are you talking about the explanations for the beginning of our universe? Those phrases are often used. They are not assumptions or facts.

For the first one, "something out of nothing" ... that's a short tag line to get attention. Once the scientist have your attention, they can go on to define their real explanation. This involve things like redefining the word "nothing" to mean "quantum foam", and then a lot of complicated physics and math.

The second one, "started with an explosion" ... that's so far off from what serious cosmologists say, it's not worth discussing.

P.S. why do so many people worry about the beginning of our universe? Why don't they wonder about the formation of stars and galaxies?

You are attacking straw men. Not worthy of any further response.

Those are vastly inaccurate oversimplifications of logical conclusions drawn from observed evidence.

Science seeks hypotheses that are consistent with present-day observations.  There is some consensus about what could have happened after the universe had already been in existence for (let's say) two seconds.  By that time, the universe was already abounding with ordinary matter (protons, electrons, neutrons), but it probably took some hundreds of thousands of years for these particles to make the atoms we feel are familiar today.

Scientists agree that whatever may have happened before the existence of protons, neutrons, and electrons is entirely hypothetical and that we cannot conduct physical experiments to "prove" any of it.

Neither is strictly true in terms of what is claimed, if that is your question.  It is what the less knowledgeable (being kind here) say is claimed, when it is not.

Those are strawman, nonsense statements NOT MADE BY REAL SCIENCE OR SCIENTISTS, but by mindless religious people who hate science and try to belittle scientific knowledge by bravely misstating scientific positions and then tearing down their own silly strawmen - then having a parade, as if they accomplished something.