Lightyear wise. i dont get it.
And for a harder bonus question: How are the laws of physics put into place? I can understand how a match burns, its flammable. but when i drop a marble it falls. Why? Do the “strings” in string theory dictate what will happen when X happens?
You mean the size of the observable universe? The radius of the observable universe can be greater than it’s age if space is expanding.
A marble falls because of gravity.
But we measure in light years and nothing can go faster then the speed of light.
And what defines gravity? Why is fire hot? What are the most basic elements that define how the laws of physics work?
The observable univesre is defined for a given observer as the region in which light could’ve travelled from any point in it to the obserever. Clearly where there is any expansion the age of observable univesre in years must be greater than it’s radius in light years as when the light arrives at the observer the distance of it’s source generally will be greatre than when it was emitted.
You may be interested to read this paper:
…
What defines anything? Why is anything anything? You can keep on asking those questions. Physics just provides models that make empirical predictions.
Let’s say an ant can run at 1 mile per hour. Put two ants butt to butt and make them run, and in one hour they will be 2 miles apart. But the universe is MUCH bigger than twice its age. How? Put those two ants on a balloon and get them to running. And while they’re running, inflate the balloon. The ants will continue to move at one mile per hour, but the distance between them is expanding as the balloon expands. If space were “already there” and the universe were being measured as if it were just chunks blowing away from an explosion, we’d expect it to be smaller, but the bang isn’t the only thing that’s going on.
Wrap your brain around that one, Opie.
Besides, space is BIG. Really Big. I mean you might think it’s a long way to the store, but that’s just peanuts compared to space.
If the universe is, say, 15 billion years old, then it’s going to be about 30 billion light years across (as light from the Big Bang will have travelled 15 billion light years out from the point where the Big Bang took place). If we are off to one side, we won’t be able to see the other side.
Ok i get it now. Space didnt get longer it streched ok simple enough. I get that differnt atoms make up differnt properties but do we know what if anything make up the laws of physics?
But this violates special relativity, doesn’t it? Nothing can move faster than the speed of light relative to anything else. If you have two photons traveling in opposite directions, they are both moving at the speed of light relative to one another.
Spacetime expanding isn’t “moving” ( movement is something that happens through spacetime ), so spacetime isn’t restricted to the lightspeed limit. According to at least some theories, spacetime expanded much larger than the speed of light in the early moments of the universe.
Also, as I recall, the universe didn’t necessarily start as a point and expand anyway; it started dense, but not necessarily small. It may well have been infinite in size when born.
Right now the standard model of particle physics consists of a bunch of particles with seemingly arbitrary properties: the electron has a certain mass, the quarks that make up protons and neutrons have other masses, gravity is purely attractive while magnetism is attractive and repulsive, and so on. Physicists have measured all these parameters but they don’t know why they have the values they have. Why does the electron have a mass of 9.10938188 × 10^-31 kg and not 9.10938189 × 10^-31 kilograms? I think there are something like 40-odd arbitrary quantities built into the standard model.
String theory is an attempt to explain why the standard model is the way it is. It postulates that all subatomic particles are merely different vibrational patterns of tiny one-dimensional strings in an 11-dimensional universe. The particles have the properties they have because there are a limited number of ways the strings can vibrate. (BTW, recent extensions of the theory suggest that the fundamental objects may not be one dimensional strings after all but higher dimensional “branes”. The basic idea that everything is the result of different vibrational patterns is the some though.)
Spacetime is expanding faster than the speed of light right now.
Say an object 1 lightyear away is moving away from us at 1 meter per second and space is expanding uniformly. Then an object 2 lightyears away will be moving away at 2 meters per second. And an object 300 million lightyears away will be moving away at 300,000 kilometers per second, which is faster than the speed of light.
If the universe is infinite and is expanding uniformly, there will always be some objects receding from each other at greater than the speed of light. During the inflationary stage of the early universe the rate of expansion was particularly high, so objects that we would consider very, very close together were receding at the speed of light. Right now objects have to be billions of lightyears apart before they recede that quickly.
Nothing makes up the laws of physics. They emerge because they are part of the fabric of being.
Gravity, according to Einstein, is a function of the warping of space by mass. If you have space and there is mass in that space, there must be gravity. It’s simply a property of spacetime, part of the very definition of its existence.
We don’t have a complete physical theory that explains the emergence of every law of physics, but one of the purposes behind theories like string theory is that particles themselves and their interactions due to fundamental forces are part of their fabric just like gravity is part of the fabric of relativity.
Lots of things can go faster than the speed of light. Light speed is only a limit for mass/energy and for information (which are equivalent). Spacetime can easily expand faster than the speed of massed particles within it. There are many estimates for how big spacetime has gotten since the big bang, but this article puts it at 156 billion lightyears and gives a brief explanation why.
Or, to put it more simply, lightspeed is only a limiting factor within spacetime. The expansion of the universe is something that’s happening to spacetime itself, so the limiting factors that govern things within spacetime don’t hold in that frame.
Do I have that right, or am I getting something wrong?
I think you’ll really have to be more specific with your questions, or you’ll get (and have been getting) answers in a shotgun fashion (not that that’s particularly bad). But a little focus in asking a question might organize your thoughts and understanding.
Asking ‘what makes up laws of physics’ is too vague. Unless, perhaps, you’re just trying to grasp what physics is. Which, of course, is to study, experiment, and model the observable natural world/universe. Particularly matter and energy, and how they interact.
ChrisBooth12, I think I read somewhere that physicists have some insight into what gravity is about, but that don’t really understand what it is. We are so conditioned to think that “things fall down” that most don’t ask why. It’s good that you do.
Have you ever seen the television series Cosmos? If not, I really think you would find it fascinating! I feel certain that Netflix has it and some movie rental places.
Current estimates put the Big Bang at 13.7 billion years ago and the diameter of the observable universe at 93.56 billion light years at present.
Obviously the numbers do not add up when using light speed as the maximum speed since stars in the observable universe could not have traveled apart at speeds greater than the speed of light. A universe who diameter is 93.56 billion ly would have to be at least roughly 50 billion years old and likely much more unless there was something going on with the time variable. While I recognize the theory that the expansion was greater than light speed immediately following the big bang it would be interesting to know what law of physics was being applied to account for this faster than light expansion.
And finally if some law of physics accounts for faster than light expansion for elements that made up the early universe, why do we still hold that nothing travels faster than the speed of light. Perhaps future generations will view light speed in the way we now think of bridging the sound barrier. In that case what happens to time and space when one approaches three times the speed of light or mach 3 times the speed of light?
This is a five year old thread, but to answer the new poster’s question, faster than light expansion violates no known laws of physics. Only movement within spacetime is influenced by this speed barrier, movement of spacetime is something different entirely.
I was wondering when someone would get around to this!
Thanks, Trihs.
And what are called “the laws of physics” derive from that method. The ‘why’ of those observable phenomena is a very broad and complex matter completely.
A light-year is a unit of distance, not time. Light is also not constant in speed. Gravitational time dilation might explain your question.