How could time be non-existent?
The main point is time and space aren’t separate things – they are one thing together – spacetime – and spacetime simply did not exist before the universe existed. You may, however, be thinking of Einstein’s use of the phrase “For us believing physicists, the distinction between past, present and future is only a stubbornly persistent illusion.” What he means is that all of spacetime – from the moment of initial existence to however things “end” – exists fully and completely all at once. Things don’t “come into being” in the future or recede into the past – that’s just an illusion. All of it exists right now, has since the beginning of spacetime, and never goes away. We just “travel” through it, and it is only our experience that makes it seem as if there’s a difference between past and future, and hence an experience of “time.”
Think of the entirety of spacetime as being a giant loaf of bread – at one crust slice is the start of spacetime, and the other crust slice is the end of spacetime. But the entire loaf exists all at once and came out of the oven fully baked – it’s not changing at all. Imagine a tiny ant starting at the beginning crust and eating its way through in a straight line from one end to the other. It can’t back up and it can’t change its pace. It can only move steadily forward and with each bite it can only get sensory input from the part of the loaf its sensory organs are touching. To the ant, it seems that each moment is unique, and while it may remember the moments from behind it, it hasn’t yet experienced the moments to come. It seems there’s a difference in the past and future, but the loaf is already there on both ends. Now what makes it weirder is that the ant itself is baked into the loaf from start to finish so in a sense it’s merely “occupying” a new version of itself from one moment to the next. This also isn’t quite right, since it’s more accurate to say that the ant is a collection of all the separate moments the ant experiences. It’s not an individual creature making it’s way from one end to the other – it’s the entire “history” of the creature from start to finish.
Doesn’t make a lot of intuitive sense to us mere humans, and the concepts have serious repercussions for the concept of free will, but that’s a different discussion.
What is the theory that black holes can be used for time travel?
First it’s important to realize that Black Holes aren’t really holes, they’re just an astronomical amount of stuff all compressed down to a relatively small size. But with all that stuff in such a small area of space comes a lot of gravity. Gravity does not just affect 3-dimensional space such as an object or a person, but also the 4th dimension of time. The more gravity that affects an object, the slower time moves for it (and the faster time moves around it from it’s point of view). So black holes can be used for time travel in a sense that you’re pressing the fast-forward button on the rest of the universe around you and when you get to the part of the movie you want to watch you can just move away from the black hole and continue.
The drawback here is that it only works as a fast-forward and cannot (to our current knowledge) be used to go backwards. It’s not exactly time travel, it’s more like stasis.
How does gravity “bend” time?
Light travels at a constant speed. Imagine Light going from A to B in a straight line, now imagine that line is pulled by gravity so its curved, it’s gonna take the light longer to get from A to B, light doesn’t change speed but the time it takes to get there does, thus time slows down to accommodate.
The universe is made up of atoms which are made out of subatomic particles which are in turn made up of quarks. Do we know if this daisy chain stops, or, like a true five-year old, will be always be asking “and then what?”
We assume that quarks are the smallest particle available to the universe (currently). There are a few reasons for this:
- Anything that is a quark cannot be on it’s own (meaning we can’t break them apart to look at them individually, thus pull more information than is available). This is due to something called Color Confinement. Without getting into the mathematics, the amount of energy needed to pull apart quark pairs would instantly create new quarks. But even if we COULD separate them, we’d have nothing to use to visibly examine them as they’re smaller than anything we can currently use to view objects (smaller than electrons so no electron scanning, etc.). Of course, this wouldn’t really a big issue because we have other ways of detecting things that are invisible to the electromagnetic spectrum, but it would definitely put a damper on things.
- Our understanding of the universe and reality is based on mathematical models and do not represent reality fully. Basically, our understanding of what goes on at subatomic levels is guessed upon using our observations and tests in our macroscale world. Our models have been correct so far, but they don’t account for everything and a discovery in the future could change how we see things.
- We will always be asking “and then what”. That’s the fundamental foundation of Science. Once we fully understand our Universe (if we ever do), we’ll be at a point where we can look beyond.
When scientists say that wormholes are theoretically possible based on their mathematical calculations, how exactly does math predict their existence?
The math of space time is ultimately best described by Einstein’s General Relativity (GR). It’s a set of mathematical equations that describes the way space and time bend in the presence of some form of matter (star, planet, whatever).
The usual order of things is to take a mass and calculate how space and time would respond to its presence. However you can also go the other way. You can take a particular spacetime shape and calculate the kind of mass that would be necessary to produce it.
In the case of wormholes, this is what is going on. We can describe a setup of spacetime that would behave like what we would call a wormhole. However if you then calculate what kind of mass we would need to produce this wormhole, we find that it would require a kind of mass that is not known to exist.
So to say the math “predicts” their existence is not really correct. We can describe just about anything with math, but it doesn’t mean that thing exists out in the real universe.
If the Big Bang theory is correct, how could nothing exist before the universe existed? What existed before the universe existed
The big bang only addresses the very early universe, and not the origin of the universe.
Would you consider an analogy or ‘thought experiment’?
Start walking north. Keep going until you reach the north pole.
Can you keep going north?
‘North’ is not a valid direction at the north pole. You can’t go any more north.
Since time is a dimension of the universe, the phrase “before the universe existed” makes about as much sense as “north of the north pole”.