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Relativity, Black Hole and some doubts

In the model of the big bang I would like to pose the following question. My understanding is that

1. The expansion of the universe is accelerating and

2. The radiation or shock wave to keep the analogy going is something we can measure.

My question is this. While we can rewind the clock to a single moment when the universe was infinity dense how do we know that this was a moment at all. Let me elaborate. As the universe expands could time or space time not also expand and if so than when the big bang occurred is something we cannot measure merely by rewinding the clock. If we are experiencing time at a given rate when the universe is at its current size would time not be being effected by the expansion also and if so would that mean the there was simply no start and no end to the universe? Perhaps the big bang is not as accurate as we may wish and perhaps it is our ability to comprehend that is limited. I propose there is no start or end to the universe it has always and will always be as it, and we, cannot exist without time and as such these two objects or things form a symbiotic relationship with each other. While the universe expands so does time and its effects are reduced in line with its expansion. Does this sound plausible and if not why?

How to describe momentum physically ?

Kiran asks: “How do you describe momentum physically by not in definitions like product of mass and velocity?”

Answer: Momentum is defined as “Mass in Motion” or “The quantity of motion“. Momentum is a measure of the “effect” a moving body can produce. It is a measure of the “effort” required to bring a body to its present state of motion from rest OR the effort required to stop a body from its present state of motion.

Since the effect produced by a moving body depends on “How much” and “How Fast“, momentum is taken as the product of mass and velocity. (P=mv). Momentum is a vector quantity and its direction is same as that of velocity.

Want to know more? Please refer to the following links

BMMD – Body Mass Measuring Device

Priyanka asked

What is a BMMD? How does it work?

Ans:

BMMD stands for Body Mass Measuring Device used by astronauts, which is basically a spring mounted chair which measures mass as a measure of inertia. As you know, one experiences weightlessness inside a satellite and normal methods of measuring mass do not work. (like a common balance or a spring balance). The time period of oscillations which depends on the force constant and mass is used in measuring mass in BMMD used by an astronomer

Why ordinary ammeter cannot measure AC?

Ac changes its direction frequently and therefore the ordinary ammeter which is just a galvanometer with a shunt, tends to respond to the magnitude and direction of the instantaneous values of current and in effect it will not show any deflection.
Ac is measured using hot wire ammeter, which is based on the heating effect of current

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