Tagged Questions
0
votes
1answer
106 views
Did space and time exist before the Big Bang? [duplicate]
I accept the Big Bang theory. What I can't understand is how there can be a where or when to the Big Bang if space time did not exist prior to it. Did space and time exist prior to the Big Bang?
3
votes
3answers
119 views
Looking out into the universe means looking back in time - how does that work?
This is a question that has been gnawing on me for many years now. Back a long time ago, as I recall in reference to a scene in a popular science show on TV, I was asked the following.
The claim is ...
0
votes
1answer
85 views
Does our local time speed up as the Universe expands?
Starting from a simplified radial Freidman Walker metric we have
$$ds^2 = -c^2 dt^2 + a(t)^2 dr^2 $$
How does one measure one's proper time operationally?
One times a light beam along an element of ...
2
votes
1answer
80 views
What was ticking just after the Big Bang?
When reading about the Big Bang, I see phrases like 3 trillionths of a second after... So, what was ticking to give a time scale like this? We define time now in terms of atomic oscillations, but ...
9
votes
3answers
437 views
The meaning of imaginary time
What is imaginary (or complex) time? I was reading about Hawking's wave function of the universe and this topic came up. If imaginary mass and similar imaginary quantities do not make sense in ...
0
votes
1answer
175 views
Does the Earth's revolution around the Sun affect radioactive decay?
Premises:
The radioactivity is either hastened or slowed inside a fast moving aircraft.
Speed of fastest aircraft: 3,529.6 km/h.
The earth's revolution is: 107278.87 km/h.
The earth's ...
2
votes
0answers
256 views
Is large-scale “time reversal” (Poincaré recurrence) possible given infinite time?
The following are some assumptions I'm basing my question on, from what (little) I understand of physics. I list them so an expert can (kindly) tell me where I'm going wrong.
There is a probability ...
1
vote
1answer
82 views
How precisely can we date the recombination?
The early universe was hot and opaque. Once it cooled enough, protons and electrons were able to form hydrogen atoms. This made the universe transparent, and was known as recombination. We can see the ...
1
vote
1answer
469 views
Relation between comoving distance and conformal time?
In cosmology, we have two quantities and I want to understand the physical relation between these two :
$\chi = \int_{t_e}^{t_0}c\frac{dt'}{a(t')}$ : the comoving distance with $t_e$ the time at ...
-2
votes
11answers
494 views
Are there any theories that explain the very beginning of absolutely everything? [closed]
Of course there's the theory of The Big Bang, and there are theories on what caused The Big Bang, but what was the cause of the very first thing that ever happened? What started every
I also won't ...
2
votes
1answer
1k views
What did Hawking mean? 'Time started at the big bang'. Book suggestions please [closed]
After writing down this question, I have come to realize that. What I really want is reading materials on the questions below.
Before the big bang there was no such thing as 'time' (Steven Hawking on ...
4
votes
4answers
105 views
Could there be more universes?
In the documentary: "Curiosity - Did God Create the Universe (on YouTube)", theoretical physicist and cosmologist Stephen Hawking states that time did not exist before the big bang.
The first ...
1
vote
0answers
89 views
Confusion with infinity and time [closed]
I have some confusion between with resolving the following situation.
I know that no measurable quantity can have a value of infinity. For example, I just wrote something out, but clearly this ...
9
votes
3answers
52 views
Seeing cosmic activity now, really means it happens millions/billions of years ago?
A Recent report about a cosmic burst 3.8 billion light years away. It is written as though it is happening now. However, my question is, if the event is 3.8 billion light years away, doesn't that mean ...
0
votes
1answer
183 views
If you removed every particle from space…? [closed]
I'm trying to find something Einstein (I think) said about time...It
was something like..
"If you removed every particle from space and were left with only one
pocket watch (clock, timepiece?), time ...
7
votes
4answers
1k views
Did time exist before the creation of matter in the universe?
Does time stretch all the way back for infinity or was there a point when time appears to start in the universe?
I remember reading long ago somewhere that according to one theory time began shortly ...
2
votes
2answers
428 views
Big bang and time
I heard Carl Sagan talking about the Universe 15 Billion years ago, and the Big Bang. He made the statement that it was the biggest explosion of all time (at first I thought this a subtle pun). This ...
