No. That would not even make sense. First of all, you are separating space and time, but in general that's not valid. It's all space-time.Mingfei Li said:The perimeter of a circle increases by radius, the surface area of a ball increase by radius(which is height which is the third dimension if the ball is a planet like the Earth), and the universe is expanding by time, can we say that the fourth dimension is time by this ?
I don't think so. Leaving aside how the radius of your circle is increasing without you defining time beforehand, you can imagine a rubber sheet being stretched in its own plane. Its area increases with its radius, which would imply that one of its spatial directions was also time, by your argument.Mingfei Li said:The perimeter of a circle increases by radius, the surface area of a ball increase by radius(which is height which is the third dimension if the ball is a planet like the Earth), and the universe is expanding by time, can we say that the fourth dimension is time by this ?
Mingfei Li said:The perimeter of a circle increases by radius, the surface area of a ball increase by radius(which is height which is the third dimension if the ball is a planet like the Earth), and the universe is expanding by time, can we say that the fourth dimension is time by this ?
supernova1054 said:But some cosmologists think that it is expanding into a 4d space.
I suspect that you have misunderstood something you read or more likely you are basing that statement on pop-science, which is not accurate.supernova1054 said:... some cosmologists think that it is expanding into a 4d space.
supernova1054 said:We have two rather confusing point of view. 1. It is expanding into nothing or 2. What is the 4d space doing; expanding into a 5d space? And so on!
weirdoguy said:It's rather weird that you wrote something like this since in your "new member introduction" you said that you are an astrophysicst. Anyway, it's a standard knowledge that there are no "two confusing points of view" but only one and very clear that an "expansion of the Universe" is a wording for the existence of the scale factor in metric tensor of FLRW spacetime. A scale factor which is increasing and makes gravitationally non-bound objects "move apart". Knowing what it really means (that is: knowing the maths) makes it rather clear that there is no need for questions like "what does Universe expand into".
supernova1054 said:I taught a course in general relativity and cosmology from 1970 until 2014 and have followed its progress closely.
What about branes? Is it really inconceivable that our universe is enveloped by a higher dimensional Spacetime? The problem is that we conceive of many strange ideas. Without observational or experimental data these concepts are almost invariably wrong.weirdoguy said:Then you should know that there are no "two rather confusing point of views".
supernova1054 said:What about branes?
supernova1054 said:The question is if the universe is creating Spacetime as it expands
supernova1054 said:What about branes? Is it really inconceivable that our universe is enveloped by a higher dimensional Spacetime?
The expansion of the universe refers to the continuous increase in the distance between all galaxies and other celestial objects. This expansion was first discovered by astronomer Edwin Hubble in the 1920s and has been confirmed by numerous observations since then.
The expansion of the universe is measured through a variety of methods, including using the redshift of light from distant galaxies, the cosmic microwave background radiation, and the observation of the large-scale structure of the universe. These measurements help scientists determine the rate of expansion, or the Hubble constant, as well as the amount of matter and energy in the universe.
Dark energy is a mysterious force that is thought to be responsible for the accelerating expansion of the universe. It is believed to make up about 70% of the total energy in the universe and its presence is inferred through observations of the universe's expansion. However, its exact nature and origin are still not fully understood by scientists.
The fourth dimension, also known as space-time, is a fundamental concept in physics that combines the three dimensions of space with the dimension of time. In the context of the expansion of the universe, the fourth dimension is used to describe the fabric of space-time that is being stretched as the universe expands. It is a crucial aspect of understanding the dynamics of the universe's expansion.
Based on current observations and theories, it is believed that the expansion of the universe will continue forever. This means that the distance between galaxies will continue to increase and the universe will become increasingly cold and dark. However, there is still ongoing research and debate about the ultimate fate of the universe and whether the expansion may eventually slow down or reverse.